heritage

Article Chemical and Biochemical Onslaught of Anthropogenic Airborne Species on the Heritage Monument of the

Deepankar Banerjee 1 and Sabyasachi Sarkar 2,*

1 Archaeological Survey of (ASI), C.G.O. Complex, Salt Lake Sector1, , West Bengal 700064, India 2 Nano Science and Synthetic Leaf Cell, Department of Chemistry, Industrial and Applied Chemistry, Ramakrishna Mission Vidyamandira, Belurmath, Howrah, West Bengal 711022, India * Correspondence: [email protected]

 Received: 18 June 2019; Accepted: 22 July 2019; Published: 24 July 2019 

Abstract: The science on the anthropogenic airborne aerosols impacting the World Heritage monument, the Taj Mahal, at , has been studied in the light of modern physico-chemical approaches. The study is an effort to understand unrecognized airborne species which were found on the surface of the Taj Mahal monument. These species have been analyzed in the light of current analytical methods to impart characterization features and their possible impacts on the surface of the marble. Chemical constituents of these substrates, which were incorporated over the top surface of the monument, have been identified. Interestingly, the carbon particulates which were found on the micro level, popularly called “particulate matters”, have now been identified in the nano domain entity, which is chemically more reactive, and have been found on the surface of the monument. Because of their high chemical activity, these nano carbons have a newer chemistry in the presence of air and sunlight, generating several reactive oxygen species (ROS). These ROS are capable of responding to complicated chemical reactions on the surface of the marble in association with deposited cyanophyceae and other deposits of plant origin, causing rapid degradation. This study provides the nature of the onslaught of such monuments exposed under the prevalent smoggy environmental scenario.

Keywords: marble black crust; carbon nano particles; soluble dust; blue-green algae (cyanophyceae); humic substances

1. Introduction The world heritage monument, the Taj Mahal at Agra, in the Indian state of , has always remained a favorite among tourists due to its grandeur and significance. The monument was built in the seventeenth century using marble, a type of marble found in Makrana marble mines in the adjoining state of . Although Agra has a few other notable monuments, like ’s tomb at Sikandra(Agra), some 36 km away from Agra, , and Itmad-ud-Daula, the Taj Mahal, due to its immaculate beauty and charm, attracts a wider area of aesthetic concern. The environmental concerns with respect to the Taj Mahal came into being in 1974 by the setting up of an oil refinery at Mathura some 50-odd km from Agra. The Government of India attributed an area between Agra and Mathura as an air pollution protected area. Therefore, a notified area called the Taj Trapezium Zone (TTZ) came into being. In 1999, the Ministry of Environment and Forests, Government of India, notified this area, the TTZ, an authority for the protection and improvement of the environment of this zone. Many countries have experienced a progressive degradation in air quality as a consequence of rapid unplanned development over the last three decades [1]. In the cities

Heritage 2019, 2, 2137–2159; doi:10.3390/heritage2030129 www.mdpi.com/journal/heritage Heritage 2019, 2 2138 of developing countries, the environmental problems are much greater because of the overwhelming scale and speed of unplanned urbanization [2]. Agra is connected with Delhi and Jaipur by National Highways, viz. NH-2, 3, and 11. It is also well connected with other major cities by rail, road networks, and air. Recently, Yamuna Expressway linked to Agra Inner Ring Road Expressway that can be used to directly reach the Taj Mahal has been introduced, resulting in direct heavy traffic flow near this monument. Dust fall is a measure of all air pollutants containing smoke, soot, or other potentially active particles that settle, with or without the rain, due to their own weight. It can be considered as a total depositional profile in a particular study area. Dust fall, through a simple non-specific test method, can be very useful in the study of long-term trends as the actual input of organic, inorganic, and biological inputs. Dust fall can be scientifically studied byway of its soluble and insoluble fractions. Therefore, water and air dispersed materials can separately be determined from the floating aerosol. In aerosol science, it is generally believed that particles with an aerodynamic diameter >50 µm do not usually remain airborne very long as they have a terminal velocity >7 cm/second. Dust particles are mostly found with dimensions around <1 µm and for these, settling due to gravity is negligible for practical purposes. In this regard, it can be considered that dusts are made up of solid particles with a size range from below 1 µm to nearly 100 µm. These can become airborne, depending on their physical characteristics, ambient conditions, and origin. Mineral dust has free crystalline silica as quartz, coal, metallic dusts like lead, cadmium, nickel, etc. Other chemical dusts such as bulk chemicals, pesticides, and bio hazards like potential viable particles such as molds and spores are spontaneously grown under such ambient conditions. Airborne dusts are particle-based species, and are mostly considered as Particulate Matter (PM), composed of solid particles and liquid droplets that can float in the air. Dust phenomena occur due to construction, mining, changes in agricultural patterns, industrial activities, and wind transport through continuous soil erosions. Dust particles can be composed of different mineral profiles. Mineral profiles affect their physical and chemical properties. An understanding of the chemical nature of the dust requires determination of the soil mineral profile since soils become airborne by the action of wind. Buildings are subjected to the impact of micro flora like cyanobacteria (blue-green algae) and chlorophyta (green algae), which can be considered as basic inhabitants in the colonization of stones. Due to the photoautotrophic nature of cellular metabolism, these microorganisms grow on stone surfaces and form colored patinas and incrustations. These organisms form a body in which airborne pollutants, particulates, and organisms get entrapped in the form of a potentially live area, which can be referred to as a bio film. Such bio films are found around adjacent areas affected by rainfall. The main inhabitants found in the bio films are the blue-green algae (cyanophyceae).

2. Addressable Problems There is a pressing concern about the yellowing and soiling of the Taj Mahal, voiced by many national and international forums, where respective views on the sustainability of the monument and its environment have been expressed. A detailed study has pointed out the air quality issues [3]. Studies have also been made on the possible impact of sulfur oxide and associated atmospheric depositions [4], along with the possible impact of dust pollution [5]. Apart from these foci, studies on the effect of dry deposition on foliage surfaces at Agra [6], on the rates of dry deposition of sulfur on natural surfaces (marble), and on the dry deposition velocity of particulate sulfate on marble have been calculated [7], and the nature of the water-soluble fraction of aerosols at Agra, the associations of the aerosols, and the ionic balances have also been studied [8]. In a recent work, it was highlighted that black carbon, brown carbon, and airborne dust, which were the result of biomass combustion, trash/refuse burning, and mobile sources, were responsible for the discoloration of the Taj Mahal(Figure1) monument [9]. Heritage 2019, 2 2139 Heritage2019, 2 FOR PEER REVIEW 3

Figure 1. Taj Mahal (UNESCO World Heritage): front view and side view on the bank of the river Yamuna, at Agra,Figure India. 1. Taj Mahal (UNESCO World Heritage): front view and side view on the bank of the river Yamuna, at Agra, India.

The scientificThe concerns scientific concerns and conservation and conservation issues issues of of the the Taj Taj MahalMahal were were first first provided provided in 1997 in by 1997 by the ICCROM-UNESCOthe ICCROM-UNESCO Report [Report10] of [10] the of mission the mission to to Agra, Agra, Satdhara,Satdhara, and and Sanchi Sanchi by M.L.Tabasso. by M.L.Tabasso. However, the steady and systematic approaches that can be used to conserve such monuments have However, thebeen steady suggested and systematicsince 1987[4–11] approaches. These report thats provided can be prevalent used to knowledge conserve- suchbased monumentsstudy on the have been suggestedinterdisciplinar since 1987y approach [4–11]. Theseto the aspects reports of providedconservation prevalent of the Taj Mahal knowledge-based monument. The report studys on the interdisciplinarypointed approach to the presence to the of aspects pigeons ofand conservation bees with hives of, which the Tajcause Mahal conservation monument. problems. The The reports pointed to themajor presence conservation of pigeons problem and of bees the Taj with marble hives, is stated which to cause be due conservation to the frequent problems. appearance The of major fractures and sporadic exfoliation layers. These studies also address the color of the monument as a conservationconcern problem for specialists of the Taj. T marblehe general is public stated and to the be newspapers due to the have frequent occasionally appearance raised the alarm of fractures and sporadicthat exfoliation the monument layers. is turning These grey studies or yello alsow due address to air pollution the color or a of lack the ofmonument maintenance. asIn this a concern for specialists.regard The, it general has also been public mentioned and the that newspapers the human eye, have though occasionally sensitive, has a raised very poor the memory alarm of that the monument iscolors, turning and slight grey variations or yellow could due hardly to air be demonstrated pollution or unless a lack objective of maintenance. data were available. In this Last regard, but not least ,such reports have said that a major conservation issue has been the presence of it has also beenblue mentioned-green algae, which that thegrow humans on different eye, parts though of the sensitive, monument. has a very poor memory of colors, and slight variationsThe literature could hardly on the international be demonstrated scenario unlessis well-equipped objective with data research were on available. air quality Last data;but not least ,such reportsair quality have trends said; thatfindings a major on the conservation acidic gases; issueand monitoring has been o thef the presence concentrations of blue-green of daily, algae, which growsmonthly on diff,erent and yearly parts study of the trends monument. on the concepts of acidic gas inputs and their possible effects on the stone surfaces. In India, such air trend yearly data can be witnessed in the national air quality The literaturestudies onconducted the international through the scenario Central Poll isution well-equipped Control Board with, which research is the main on air nodal quality agency data; air quality trends;under findings the Ministry on the of Environment acidic gases; and and Forests, monitoring Government of of the India. concentrations However, no reports of daily, on the monthly, and yearly studystudy trendsof the effect on of the aerosols concepts on the of monument acidic gas surfaces inputs in Indi anda from their such possible agencies eareffects available on the. stone surfaces. In India,To provide such air a concise, trend yearlyresearch datadata-based, can bepragmatic witnessed understanding in the national of the overall air qualityimpact of studies atmospheric species on the Taj Mahal monument, a couple of studies were recently reported [9,11]. conducted throughThese stud theies Centralpointed out Pollution that the pollution Control load Board, on the whichTaj Mahal is monument the main could nodal be agencyfrom natural under the Ministry of Environmentas well as anthropogenic and Forests, inputs. Government of India. However, no reports on the study of the effect of aerosolsThe on theexternal monument surface of any surfaces building in in India urban frompolluted such environment agenciess is are inevitably available. destined to be To providecovered a concise, with gray research or black layers data-based, generally pragmatic called black crustsunderstanding [12](Figure 2 of). Sulfur the overalldioxide and impact of nitrogen oxides are the most harmful air pollutants for stone materials and they are also the major atmosphericsource species of soluble on the salts, Taj sulfates Mahal, and monument, nitrates [13] a. couple of studies were recently reported [9,11]. These studies pointed out that the pollution load on the Taj Mahal monument could be from natural as well as anthropogenic inputs. The external surface of any building in urban polluted environments is inevitably destined to be covered with gray or black layers generally called black crusts [12](Figure2). Sulfur dioxide and nitrogen oxides are the most harmful air pollutants for stone materials and they are also the major source of soluble salts, sulfates, and nitrates [13]. Heritage 2019, 2 2140 Heritage2019, 2 FOR PEER REVIEW 4

Figure 2.Areas near water spouts exhibiting black crust zones on the Taj Mahal. Figure 2. Areas near water spouts exhibiting black crust zones on the Taj Mahal. Other deteriorating agents like the solar input, relative humidity, and wind conditions also affectOther the deteriorating dispersion and agents dilution like the of solar pollutants input, within relative a humidity, given area. and The wind intensity conditions and also rate a offf ect thew dispersioneathering depend and dilution upon the of pollutantsstone, the surface within area, a given and area. the levels Theintensity of atmospheric and rate pollutants, of weathering the dependorientation upon of the the stone, building, the surfaceacid rain area,, and andrainfall the [ levels14]. of atmospheric pollutants, the orientation of the building,The Agra acid Environment rain, and rainfall Management [14]. Plan[3] stated that actions taken for the protection of the TTZThe were Agra targeted Environment for protecting Management the structure Plan [3 of] stated the Taj that Mahal actions and taken not Agra for the city protection or the TTZ. of theSuch TTZ wereactions targeted taken for for protecting protection the were structure mainly of thefocused Taj Mahal on repairing and not Agra or maintaining city or the TTZ. the Taj Such Mahal actions takenstructure for protection and control wereling the mainly pollution focused through on repairing closing down or maintaining industries. T thehe repor Taj Mahalt also emphasized structure and that there is a need for a scientific study and innovative approach to achieve the desired results. controlling the pollution through closing down industries. The report also emphasized that there is Earlier in the ICCROM-UNESCO report of 1997, [10] pointed to the conservation cum environmental a need for a scientific study and innovative approach to achieve the desired results. Earlier in the concerns in relation to the Taj Mahal monument. Therefore, there is a need to study, quantify, and ICCROM-UNESCO report of 1997, [10] pointed to the conservation cum environmental concerns in assess the actual environmental cum chemical species interacting in this complex scenario. This relation to the Taj Mahal monument. Therefore, there is a need to study, quantify, and assess the actual study has attempted to qualitatively ascertain the atmospheric and associated environmental inputs environmentalacting upon the cum area chemical of the monument. species interacting in this complex scenario. This study has attempted to qualitativelyWith such ascertain thought the, atmosphericfirst, this paper and willassociated focus on environmental significant environmental inputs acting upon inputs the in areathe of thevicinity monument. of the monument to visualize the possible chemical imprints acting upon the area. The importantWith such issues thought, related first, to thisthese paper inputs will are focus governed on significant by the local environmental climate, and inputs demographic in the vicinity and of thesocial monument profile, to which visualize affect the the possible economic chemical-based imprints environmental acting upon issues the related area. The to important the problem issuess relatedencountered to these in inputs conservation are governed of the by monument. the local climate, and demographic and social profile, which affect the economic-basedLocal Climate: environmental Agra has a continental issues related type of to clim theate. problems It has three encountered distinct seasons: in conservation summer, of themonsoon monument., and winter. The monsoon season is from July to September, winter season is from NovemberLocal Climate: to FebruaryAgra, and has summer a continental months typeare from of climate. April to June. It has The three temperature distinct seasons: ranges fro summer,m 26 monsoon,°C to 39 and°C during winter. the The monso monsoonon, from season 27 °C is to from 47 ° JulyC during to September, the summer, winter and seasonbetween is from2 °Cand November15 °C toduring February, the andwinter summer. The relative months humidity are from ranges April from to June. 60% toThe 90% temperatureduring the winter, ranges 60%from to 26 95◦%C to during the monsoon, and 30%to 60% during the summer. The summers are characterized by high 39 ◦C during the monsoon, from 27 ◦C to 47 ◦C during the summer, and between 2 ◦Cand15 ◦C duringdaytime the temperatures winter. The ranging relative between humidity 23 ranges°Cand44 from °C and 60% low to 90%duringhumidity of the 25% winter,–40%. The 60% wind to 95% duringdirection the monsoon,witnessed in and the 30%to city is 60% from during North theto West summer. (prevailing The summers wind) and are South characterized and Southeast by high (monsoon wind)[15]. daytime temperatures ranging between 23 ◦Cand44 ◦C and low humidity of 25%–40%. The wind Socio-demographic profile: Agra has a total population of about 1400,000 and the population direction witnessed in the city is from North to West (prevailing wind) and South and Southeast density is about 19.593 per sq. km [13]. The population density is 897 persons per sq. km compared (monsoon wind) [15]. to the national Indian average of 324persons per sq. km. This data shows an immensely Socio-demographic profile: Agra has a total population of about 1400,000 and the population overcrowded city. The average literacy rate in Agra is 70%. The population is composed of55% density is about 19.593 per sq. km [13]. The population density is 897 persons per sq. km compared to males and 45% females, while the work population rate is only 27%. Vulnerability assessments of the thecity national conducted Indian by various average agencies of 324persons like OXFAM, per sq. the km. State This Urban data Development shows an immensely Authority, overcrowded and Agra city.Mu Thenicipal average Corporation literacy have rate estimated in Agra that is 70%. around The 50% population of residents is composedlive in slums of55% [16], while males another and 45% females,study revealed while the that work the populationslums are home rate to is onlyaround 27%. 40% Vulnerability of the population assessments [3]. The ofurban the cityarea conductedof Agra by various agencies like OXFAM, the State Urban Development Authority, and Agra Municipal

Heritage 2019, 2 2141

Corporation have estimated that around 50% of residents live in slums [16], while another study revealed that the slums are home to around 40% of the population [3]. The urban area of Agra is divided into Nagar Mahapalika (local administrative civic body for the city), Agra Cantonment Area, and the Dayalbagh and Swamibagh Panchayats (Panchayats are local civic administrative bodies). The municipal area has been divided into three main divisions, viz. the main city, Tajganj, and the Trans Yamuna Area. The municipal area has 90 wards. The jurisdiction of the Agra urban area is under the Agra Development Authority (ADA). Economic-based environmental issues: The economy of Agra is based on small and scattered industries, trade, commerce, and tourism. Domestic, medium, and small industries exist as a tradition. On a daily basis, the Taj Mahal is visited by 8–10 thousand tourists, of whom 54% are foreign nationals. There are 12 major- and medium-scale industries and 7200 small-scale units inAgra in various goods, like pipes, cast iron fittings and allied fabrication goods, electrical items, leatherwear, and shoes. The city has 150 foundry units that produce cast iron pipe fittings, motor and tractor parts, weights and measures, diesel engines, pumping sets, generators, agricultural equipment, etc. The small-scale industries are comprised of textiles, cotton, wood paper products, leather goods, metal products, electroplating units, auto and engine parts, etc. The handicraft industry is composed of zari and zardozi, (zari and zardozi are traditional medieval handicraft clothing in which some precious metal is embroidered on the clothes, marble and stone carving inlay works, and in carpet units). About 116 of these are exporting units. Agra has several notified industries; the majority of these are foundries in which the principal source of emission is the cupola. The fuels used in these industries are coal; coke; and HSD, LPG, and furnace oil. The most commonly used are hard coke, steam coal, wood, and fuel oil. The volume of effluent gases discharged depends upon the cupola, melting temperature regimes, operation durations, nature of the charged material, and the coke used. Gases are released during hot metal drawing and during casting. Agra is also famous for Petha (a type of local and traditional sweet), which is produced locally and consumes enormous thermal energy supplied by primitive methods like fire wood, at the cost of depleting local forestry and coal burning. The total air pollution in the city from domestic activity, industrial activity, Petha units (sweets industry), vehicular source inputs, and diesel generators (D.G. sets) is about 51 t/day [3,17]. Along with these, the Mathura refinery, Firozabad glass industries, and brick kiln factories are also situated within 40km from Agra [18]. People in slums use firewood, coal, and cow-dung, and the average consumption is 200–300kg/capita/year. Daily use of burning cow dung is around 4 hours/day. Vehicles contribute a major source of air pollution. The total number of vehicles has grown at a tremendous rate of 57.7% during 1994 to 2000 and the numbers have increased each year. The vehicular pollution load in Agra city is around 15.6 t/day. Diesel Generator (DG) sets also contribute to the pollution input, as the diesel used for running the DG sets emits a considerable amount of airborne effluents. Many of these diesel powered engines are also used in lighting shops during power cuts and for short-distance transport in three wheelers, adulterated diesel is employed, with kerosene emitting voluminous un-burnt fuel as smoke. Natural sources also contribute to the pollution scenario as the soil of Agra consists of loose alluvium, which thus becomes airborne easily. A considerable amount of windblown dust covers the city during the summer months. Dust is the major contributor of particulates in the summer from April to June, during which period dust storms with high crustal loads and high wind speeds occur. Such dusty masses also remain suspended during summers in the atmosphere as hazes. The Suspended Particulate Matter (SPM) shows very high values and more so on days which witness dust storm episodes. Additional air pollution that has not been recognized till now is the contribution from the black particulate matters under nano dimension trapped in floating aerosol originating from the neighboring states. A troubling aspect recently seen is related to the solid waste management in the city, which is extremely poor. There is no method utilized to collect the garbage under the classification of biodegradable and non-degradable approaches. Total solid waste is perhaps in the magnitude of Heritage 2019, 2 2142

450 t/day. There has now been a new unscientific practice introduced by the civic body to burn accumulated city garbage at the city dump sites as a rapid measure to clear it, which in turn releases enormous un-burnt solid particulates with obnoxious gases into the local environment.

3. Sampling/Materials and Methods Interest in the study of aerosol phenomena worldwide is justified by high particle emissions from natural and anthropogenic sources, high concentrations of gaseous precursors, relative humidity, weather conditions that favor the stagnation of pollutants, low precipitation rates, and water vapor in the atmosphere. Aerosols also have an impact on the weathering of historical buildings. The pollutants are transferred by two mechanisms: dry deposition and wet deposition. The external surfaces of a building with an atmospheric effect of pollution evidence black, brown, or grey crusts and black scab-like areas, depending on the deposition of the particles, rainfall, and transformation within the crusts. The geographical area situated in a continental type of climate witnesses a temperature regime which radiates between 1 ◦C in winters to around 47 ◦C in intense summers within a year at Agra. Therefore, the monument falls in a temperature range in which a yearly thermal difference pattern influences geological processes conducive to surface weathering. Micro crust pieces peel and fall off from places such as water spouts or areas of water passage naturally due to natural weathering phenomena. Dust is a natural phenomenon and is measured on a monthly basis as a standard measurement procedure called dust fall, and secondly as dust collected on a daily fixed cycled monitoring operation system to measure Suspended Particulate Matter (SPM) from high volume samplers. The particle mode used for dust characterization was the coarse mode. The algal-bacterial input into the dust fall, i.e., algal sample, has been taken from dust fall samples. Soluble organic components of the aerosols have been determined from the water-soluble portions from the standard glass fiber filter papers used in high volume sampling operations. Marble crust samples and fresh marble used in conservation have been examined along with marble samples with algal growth. Dust has also been characterized based on seasonal conditions. The composite dust represents the airborne input of the annual dust profile. To study the effect of weathering and the chemical nature of these diverse pollutants, samples like blue-green algae, airborne dust, soluble dust from dust fall, seasonal dust, and water-soluble portions of aerosols were analyzed. There are zones near the water spouts, places protected from direct rainfall, niches, and areas where water accumulation had taken place. From these zones, crust pieces, due to weathered geological surfaces, give way due to various geological and atmospheric stress factors and such small pieces have been used as treasure for analyses. Algal samples have taken from monthly dust fall, airborne dust from high volume samplers, natural peeled off pieces from the monument as crust pieces, water-soluble fractions from dust fall, and water-soluble fractions of seasonal organic aerosols have been extracted from the glass fiber filter papers. Dust samples have been taken from high volume samplers representing major seasons, as well as a composite dust profile, which contains the features of the annual dust load.

Sample Preparation A black crust that was separated from the monument under chemical and biological weathering conditions has been identified as the best sample to work with. To search for the identity of any nano domain carbon, a part of this was washed with warm nitric acid, the residue was then leached with dilute sodium hydroxide, and the filtrate was acidified with hydrochloric acid and vacuum evaporated to dryness. Such treatment removes other contaminants, including large carbon particulates, to separate nano carbon. The black residue was washed with cold water thrice to remove any sodium chloride and was then subjected to transmission electron microscopy (TEM) analysis. For mineralogical analysis, the samples were analyzed by a Seifert model Debye flex X-ray Diffractometer, with CrKα radiation and running conditions of 30mA, 40kV, and a scan speed of 3.0◦/min. Samples were analyzed within a range of 0–90◦. XRD plots were further refined by Bruker AXS Software. Heritage 2019, 2 2143

IR analysis was carried out by an FTIR Bruker Spectrophotometer (Vector 22 Model) working between 1 4000 and 400cm− using a KBr disc. For elemental analysis coupled with morphological and topographical analyses, samples were subjected to anFEI Quanta 200 model computer-controlled scanning electron microscopy cum energy dispersive spectroscopy (SEM-EDS) system. Transmission electron microscopy (TEM) images were taken using the FEI TECHNAI-T-20 machine operated at the voltage of 200 kV.

4. Results and Discussion X-ray data of the summer, winter, and a composite mixture with the PDF card number and mineral component is shown in Tables1–3, respectively. The XRD data revealed the soil oriented profile of the summer (Figure3), winter dusts (Figure4) and of composite (Figure5). Composite dust represents the annual dust. Quartz is the main mineral, followed by illite, chlorite, montmorillonite, kaolinite, , magnetite, hematite, and mixed-layer silicates. Feldspars are represented by plagioclase, microcline, and albite. The profiles of X-ray reflections are as per the standard Joint Committee on Powder Diffraction Standards (JCPDS) [19]. According to the JCPDS [19], in XRD patterns, one can observe the major and lesser reflections of minerals. Among the major XRD reflections according to the JCPDS standard patterns, quartz gives reflections at 3.34, 4.23, 1.8, 1.54, and 2.45Å. Subsequently, the mixed layer clay minerals give reflections at 12 Å;illite gives reflections at 10, 4.48, 3.33, 2.61, and 1.53 Å; kaolinite gives reflections at 7.17, 3.57, 1.62, 1.48, and 4.36 Å; chlorite gives reflections at 7.07, 14.1, 3.54, 4.72, and 2.84 Å; orthoclase (alkali feldspar) gives reflections at 3.31, 3.77, 4.22, 3.24, and 3.29 Å; albite (plagioclase feldspar) gives reflections at 3.19, 3.78, 6.39, 3.68, and 4.03 Å; calcite gives reflections at 3.03, 2.28, 2.09, 1.01, and 1.87 Å; hematite gives reflections at 2.69, 1.69, 2.51, 1.83, and 1.48Å; magnetite gives reflections at 2.53 and 2.42 Å; and montmorillonite gives reflections at 15, 4.0, 5.01, 3.02, and 1.5 A◦(Figures3–5). Themineralogical results are based on major and lesser reflections. The XRD results of the marble black crust gave the effect of water percolation on the marble matrix, impact of cyanobacteria, and impact of soil-oriented minerals. With the joint action of water, cyanobacteria, and soil minerals on the marble, the weathering effects could be assessed. oxalate hydrate could be the result of the action of oxalic acid secreted by the cyanobacteria. Ankerite formation may be due to the action of iron oxides on the marble, while hydrate may have been formed by the action of water. The impact of airborne dust on the marble black crust could be seen by the presence of illite, kaolinite, and hematite. Hematite may be from the soil or from anthropogenic sources. The IR spectra of marble black crust gave similar results. The spectral features showed the presence of calcite and soil minerals on the marble viz. montmorillonite, kaolinite, hematite, quartz, and organic carbon.

Table 1. XRD data of summer dust.

d Å Std d Å Exp PDF Card no Mineral Component

7.12 7.79 78-2110 Kaolinite, Al4(OH)8Si4O10

7.07 6.97 13-3 Chlorite, Mg2Al3(Si3Al)O10(O8) Plagioclase Feldspar, NaAlSi O CaAl Si O 9-458, 3 8- 2 2 8 6.39 6.31 Montmorillonite, 003-0016 (6.5)(NaCa)O3(AlMg)2Si4O10(OH)2nH2O

4.26 4.28 19-926 Microcline, KAlSi3O8 (Potassium Aluminium Silicate)

3.34 3.32 46-1045 Quartz, SiO2

Orthoclase Feldspar, KAlSi3O8 3.24 3.23 19-931 Montmorillonite, (3.25) (NaCa)O,3(AlMg)2Si4O10(OH)2nH2O

3.03 3.01 05-0586 Calcite, CaCO3

2.7 2.75 33-0664 Hematite, Fe2O3 Heritage2019, 2 FOR PEER REVIEW 8

Heritage 2019, 2 2144 Heritage2019, 2 FOR PEER REVIEW 8

Figure 3.XRD of summer dust.

Table 2.XRD data of winter dust.

PDF d Å Std d Å Exp FigureFigure 3.3.XRDXRD of of Minerals summerummer dust Component dust.. Card no 7.12 7.5 78-2110 TableTable 2.2.XRD data dataKaolinite of of winter winter Al dust dust.4(OH). 8Si4O10 5.16 5.16 003-0016 Montmorillonite (NaCa)O,3(AlMg)2Si4O10(OH)2nH2O PDF 4.72d d Å Å Std Std4.75 d d Å Å Exp Exp 13-3 PDF Card noChlorite MgMineral2Al Mineral3(Si Component3Al)O Component10(O8) Card no 2 3 10 2 4.48 7.124.34 7.531-968 78-2110IlliteKAl (Si KaoliniteAlO )(OH) Al4(OH) 8Si4O10 7.12 7.5 78-2110 Kaolinite Al4(OH)8Si4O10 4.22 4.22 19-926 Microcline KAlSi3O8 (Potassium Aluminum Silicate) 5.165.16 5.16 5.16 003- 003-00160016 Montmorill Montmorilloniteonite (NaCa)O,3(AlMg) (NaCa)O,3(AlMg)2Si24SiO410O(OH)10(OH)2nH2nH2O2 O 3.34 3.32 46-1045 Quartz SiO2 4.724.72 4.75 4.75 13-3 13-3 Chlorite Chlorite Mg2 MgAl32(SiAl3Al)O(Si3Al)O10(O108)(O 8) 3.03 3.32 05-0586 Calcite CaCO3 4.484.48 4.34 4.34 31-968 31-968 IlliteKAl IlliteKAl2(Si32AlO(Si3AlO10)(OH)10)(OH)2 2 3.34 3.32 31-968 Illite (KAl2(Si3AlO10)(OH)2) 4.22 4.22 19-926 Microcline KAlSi3O8 (Potassium Aluminum Silicate) 4.22 4.2233-0664 19-926 Microcline KAlSi3O8 (Potassium Aluminum Silicate) 2.7 3.34 2.85 3.32 46-1045 HematiteQuartz Fe2O SiO3 2 3.34 3.32 46-1045 Quartz SiO2 3.03 3.32 05-0586 Calcite CaCO3 2.53 3.032.4 3.3246-1045 05-0586Quartz SiO Calcite2 CaCO3 3.34 3.32 31-968 Illite (KAl2(Si3AlO10)(OH)2) 1.69 1.66 33-0664 Hematite Fe2O3 3.34 3.3233-0664 31-968 Illite (KAl2(Si3AlO10)(OH)2) 2.7 2.85 Hematite Fe2O3 2.7 2.85 33-0664 Hematite Fe2O3 2.532.53 2.4 2.4 46-1045 46-1045 Quartz Quartz SiO2 SiO 2 1.691.69 1.66 1.66 33-0664 33-0664 Hematite Hematite Fe2O Fe3 2O3

FigureFigure 4.XRD 4. ofXRD winter of winterdust. dust.

Table 3. XRD data of composite dust.

Figure 4.XRD of winter dust.

Table 3. XRD data of composite dust.

Heritage 2019, 2 2145

Heritage2019, 2 FOR PEER REVIEW Table 3. XRD data of composite dust. 9

d Å DÅ d Å Std DÅ Exp PDFPDF Card Card no. no. Mineral Mineral Component Component Std Exp 12.0 12.23 Mixed layer silicates 12.0 12.23 Mixed layer silicates 10 10.4 31-968 IlliteKAl2(Si3Al10)(OH)2 10 10.4 31-968 IlliteKAl2(Si3Al10)(OH)2 6.5 6.8 003-0016 MontmorilloniteMontmorillonite (NaCa)O.3(AlMg) 2SiO10(OH)2nH2O 6.5 6.8 003-0016 7.12 7.23 78-2110(NaCa)O.3(AlMg) Kaolinite Al2SiO4(OH)10(OH)8Si42OnH10 2O 7.12 7.23 78-2110 IlliteKAlKaolinite(SiAlO Al4)(OH)(OH)8SiMontmorillonite4O10 5.0 5.17 31-968,003-0016 2 10 2, (AlMg) (Si O )(OH) nH O IlliteKAl2(SiAlO10)(OH)2 4 2,10 Montmori2 2llonite 5.0 5.17 31-968,003-0016 4.7 4.7 13-3(AlMg) Chlorite2(Si4 MgO102)(OH)Al3(SIAl)O2nH210O(O 8)

4.24.7 4.7 4.36 19-92613-3/46-1045 Chlorite Microcline Mg KAlSi2Al33(SIAl)OO8/Quartz10(O SiO8) 2(4.42) 4.2 4.36 19-926/46-1045 Microcline KAlSi3O8/Quartz SiO2(4.42) 4.22 4.20 19-926 Microcline KAlSi3O8 (PotasiumAluminium- Silicate) Microcline KAlSi3O8 (PotasiumAluminium- 3.664.22 4.20 3.66 19 20-554-926 Albite NaAlSi3O8 Silicate) 3.34 3.31 46-1045 Quartz SiO2 3.66 3.66 20-554 Albite NaAlSi3O8 3.03 3.00 05-0586 Calcite CaCO 3.34 3.31 46-1045 Quartz SiO2 3 2.953.03 3.00 2.95 05- 19-9260586 Calcite Microcline CaCO KAlSi3 3O8

2.702.95 2.95 2.68 19 33-0664-926 Microcline Hematite KAlSi Fe32OO83

2.532.70 2.68 2.53 33- 76-18490664 Hematite Magnetite Fe2O Fe33 O4 2.53 2.53 76-1849 Magnetite Fe3O4 2.51 2.50 33-0664 Hematite Fe2O3 2.51 2.50 33-0664 Hematite Fe2O3 2.49 2.47 05-0586 Calcite CaCO3 2.49 2.47 05-0586 Calcite CaCO3 2.28 2.29 05-0586 Calcite CaCO3 2.28 2.29 05-0586 Calcite CaCO3

FigureFigure 5. XRD5. of composite of composite dust dust..

The airborne dust profiles of the composite, summer, and winter showed the input of crustal The airborne dust profiles of the composite, summer, and winter showed the input of crustal minerals into the dust. The airborne dust incorporated coarse and fine aerosols. Composite dust or minerals into the dust. The airborne dust incorporated coarse and fine aerosols. Composite dust or the the annual profile of the dust showed a wide range of minerals. Under soil mineralogical annual profile of the dust showed a wide range of minerals. Under soil mineralogical considerations, considerations, the dust represented the minerals of the local soil. The airborne dust gave a the dust represented the minerals of the local soil. The airborne dust gave a soil-oriented profile which soil-oriented profile which becameairborne with the action of wind and meteorological phenomena. becameairborneAmong the minerals with the, calci actionte, quartz of wind, and and feldspars meteorological can be phenomena.considered in Among the coarse the minerals,particle mode calcite, quartz,[20]. and feldspars can be considered in the coarse particle mode [20]. OtherOther minerals minerals like like kaolinite, kaolinite, montmorillonite,montmorillonite, and and illite illite can can be be considered considered in inthe the intermediate intermediate particleparticle mode, mode, whilewhile magnetite and and hematite hematite can can be considered be considered in the in fine the particu fine particulatelate mode. The mode. Thecomposite composite dust dust representing representing the annual the annual dust dustgave gavea broad a broad signature signature of the ofairborne the airborne minerals. minerals. The Themagnetic magnetic mineral mineral magnetite magnetite was was present present in inthe the composite composite (annual) (annual) dust dust profile. profile. Apart Apart from from these these,, thethe other other minerals minerals were were similar similar inin thethe summersummer an andd winter seasons seasons,, depicting depicting that that identical identical minerals minerals werewere present present within within the the area. area. Since Since thethe naturenature of the dust dust represents represents the the parent parent material material,, which which is the is the soil,soil, the the dust dust showed showed that that the the dust dust was was illitic illitic as theas the soil soil material mater wasial was illitic, illitic corresponding, corresponding to an to earlier an studyearlier on study the soils on the of thesoils geographical of the geographical region ofregion Agra of [ 21Agra]. [21].

Heritage 2019, 2 2146 Heritage2019, 2 FOR PEER REVIEW 10

4.1. Marble Marble C Characterizationharacterization ( (TableTable 44))

4.1.1. Fresh Fresh M Marblearble ( (FigureFigure 66)) The fresh fresh marble marble used used in inconservation conservation showed showed all reflections all reflections of the of calcite the calcitemineral. miner Calciteal. mineral Calcite mineralshowed showed a typical a marble typical texture marble with texture distinct with mineral distinct patterns. mineral patterns. The matrix The showed matrix an showed area with an area high withcrystalline high crystalline features characteristic features characteristic of perfect crystallographicof perfect crystallographic lattices. The lattices. interfaces The withininterfaces the marblewithin thematrix marble were matrix coherent. were coherent.

Heritage2019, 2 FOR PEER REVIEWFiFiguregure 6. XRDXRD of of fresh fresh marble marble used used in in conservation conservation.. 11

4.1.2.4.1.2. Marble Marble with with Black BlackTable Crust Crust 4.(Figure XRD (Figure of7 fresh )7) marble and marble with black crust. The weathered marble with black crust showed weathering profiles and input of the The weathered marbled with blackd crust showed weathering profiles and input of the soil-oriented soilSample-oriented matter within its structure.PDF The Card weathered no mass depictedMineral the Component impact of hydration matter within its structure.ÅStdThe ÅExp weathered mass depicted the impact of hydration combined with allied combined with allied physical and chemical aspects. Hydration is a process resulting in the physical and chemical2.45 aspects. Hydration2.49 is05 a- process0586 resulting in the weatheringCaCO of3 mineral matrices. weathering of mineral matrices. Low crystalline zones were visible in the images. The zones gave the Low crystalline zones were2.27 visible2.28 in the images.05-0586 The zones gave the impact of hydration along with the impact of hydration along with the presence of amorphous layers. Amorphous layers within the fresh marble 2.10 2.09 05-0586 presencemarble of naturally amorphous have layers. a lower Amorphous crystallinity. layers Loss within of the coherence marble between naturally the have interfaces a lower crystallinity. could be 1.90 1.91 05-0586 Lossassessed. of coherence The weathering between theproducts interfaces present could in the be assessed.black crust The were weatheringsoil inputs productsfrom dustpresent like quartz, in the blackillite crust, and weresoil magnetite. inputs1.87 Marble from 1.87 weathering dust like quartz, 05 profiles-0586 illite, were and represented magnetite. by Marble calcium weathering oxalate hydrate, profiles wereankerite, represented and calcium by calcium12.0 carbona oxalate11.79te hydrate. hydrate, ankerite, and calcium carbonateMixed layer hydrate. clays 10.02 10.32 31-968 Illite,KAl2(Si3AlO10)(OH)2 Calcium oxalate hydrate (Whewellite), 5.93 5.93 75-1313 CaC2O4H2O 5.02 5.08 31-968 Illite,KAl2(Si3AlO10)(OH)2 4.91 4.98 31-968 Illite,KAl2(Si3AlO10)(OH)2 4.33 4.33 15-20 Calcium carbonate hydrate, CaCO3H2O Marble with 3.57 3.58 78-2110 Kaolinite, Al4(OH)8Si4O10 black crust 3.03 3.01 05-0586 Calcite, CaCO3 2.9 2.86 33-282 Ankerite,Ca(FeMg)(CO3) 2.63 2.66 15-20 Calcium carbonate hydrate, CaCO3H2O 2.53 Figure2.56 7.Figure XRD 7. spectra of19 marble-629 of marble with black with crust black. crust.Magnetite, Fe3O4 2.45 2.45 46-1045 Quartz, SiO2 4.1.3. FTIR of Marble2.08 Black Crust2.08 ( Figure 8a05) -0586 Calcite CaCO3 The IR spectra of1.91 marble black1.91 crust revealed05-0586 carbonate bands at 2517Calcite cm−1, CaCO1799 cm3 −1, 1428 cm−1, 876 cm−1, and 711 1.87 cm−1 . The1.86 other mineral05-0586,33 componen-0664 ts are montmorilloniteCalcite CaCO3,Fe [222O]3, (1.83)at 606 cm−1, hematite[23] at 585 cm−1 corresponding to the IR band range of 584–588 cm−1, quartz [23] at 457 cm−1 corresponding to the IR band range of 455–450 cm−1, kaolinite[23] at 430 cm−1,and organic carbons (as C-H vibration) at 2924 cm−1 and 2873 cm−1.

4.1.4. FTIR of Organic Content of the Marble Black Crust (Figure 8b)

The organic content of the marble black crust showed symmetric CH2 at 2924 cm−1and asymmetric CH2 at 2852 cm−1;the presence of esters at 1748 cm−1; substituted aromatics at 1561 cm−1;the deformation of CH3 and CH2 [24] at 1477 cm−1 and 1377 cm−1, respectively; asymmetric or symmetric stretching of esters and carbohydrates at 1146 cm−1; aliphatic ethers [25] at 1085 cm−1; and aryl mono-substituted features at 739 cm−1.

Heritage 2019, 2 2147

4.1.3. FTIR of Marble Black Crust (Figure8a)

1 1 1 The IR spectra of marble black crust revealed carbonate bands at 2517 cm− , 1799 cm− , 1428 cm− , 1 1 1 876 cm− , and 711 cm− . The other mineral components are montmorillonite [22] at 606 cm− , 1 1 1 hematite [23] at 585 cm− corresponding to the IR band range of 584–588 cm− , quartz [23] at 457 cm− 1 1 corresponding to the IR band range of 455–450 cm− , kaolinite [23] at 430 cm− ,and organic carbons 1 1 Heritage(as C-H2019 vibration), 2 FOR PEE atR REVIEW 2924 cm − and 2873 cm− . 12

(a)

(b)

Figure 8. FTIR spectra of (a) marble with black crust, and (b) organic content of the marble black Figure 8. FTIR spectra of (a) marble with black crust, and (b) organic content of the marble black crust. crust.

4.2. Algal Characterization (Figure 9)

The FTIR spectra of the blue-green algae showed a water absorption band at 3418 cm−1 conjugated with a protein structure; lipid bands [26] at 2923 cm−1 and 2852 cm−1; protein amide [27] at 1637 cm−1; C-H deformations of CH2 or CH3 groups in aliphatics [27] at 1463 cm−1; carbohydrates [28] at 1026 cm−1; mixed Si-O deformations and octahedral sheet vibrations at 583 cm−1 and 518 cm−1, respectively; and quartz at467 cm−1[23].

Heritage 2019, 2 2148

4.1.4. FTIR of Organic Content of the Marble Black Crust (Figure8b)

1 The organic content of the marble black crust showed symmetric CH2 at 2924 cm− and 1 1 1 asymmetric CH2 at 2852 cm− ; the presence of esters at 1748 cm− ; substituted aromatics at 1561 cm− ; 1 1 the deformation of CH3 and CH2 [24] at 1477 cm− and 1377 cm− , respectively; asymmetric or 1 1 symmetric stretching of esters and carbohydrates at 1146 cm− ; aliphatic ethers [25] at 1085 cm− ; 1 and aryl mono-substituted features at 739 cm− .

Table 4. XRD of fresh marble and marble with black crust.

Sample d ÅStd d ÅExp PDF Card no Mineral Component

2.45 2.49 05-0586 CaCO3 2.27 2.28 05-0586 fresh marble 2.10 2.09 05-0586 1.90 1.91 05-0586 1.87 1.87 05-0586 12.0 11.79 Mixed layer clays

10.02 10.32 31-968 Illite,KAl2(Si3AlO10)(OH)2 Calcium oxalate hydrate 5.93 5.93 75-1313 (Whewellite), CaC2O4H2O

5.02 5.08 31-968 Illite,KAl2(Si3AlO10)(OH)2 Marble with 4.91 4.98 31-968 Illite,KAl2(Si3AlO10)(OH)2 black crust Calcium carbonate hydrate, 4.33 4.33 15-20 CaCO3H2O

3.57 3.58 78-2110 Kaolinite, Al4(OH)8Si4O10

3.03 3.01 05-0586 Calcite, CaCO3

2.9 2.86 33-282 Ankerite,Ca(FeMg)(CO3) Calcium carbonate hydrate, 2.63 2.66 15-20 CaCO3H2O

2.53 2.56 19-629 Magnetite, Fe3O4

2.45 2.45 46-1045 Quartz, SiO2

2.08 2.08 05-0586 Calcite CaCO3

1.91 1.91 05-0586 Calcite CaCO3

1.87 1.86 05-0586,33-0664 Calcite CaCO3,Fe2O3,(1.83)

4.2. Algal Characterization (Figure9)

1 The FTIR spectra of the blue-green algae showed a water absorption band at 3418 cm− conjugated 1 1 1 with a protein structure; lipid bands [26] at 2923 cm− and 2852 cm− ; protein amide [27] at 1637 cm− ; 1 1 C-H deformations of CH2 or CH3 groups in aliphatics [27] at 1463 cm− ; carbohydrates [28] at 1026 cm− ; 1 1 mixed Si-O deformations and octahedral sheet vibrations at 583 cm− and 518 cm− , respectively; 1 and quartz at467 cm− [23]. The IR spectrum of blue-green algae showed the presence of proteins, amide, lipids, aliphatic carbon, amides, and carbohydrates, and the adsorption of clay minerals on the algal surface. The exterior surfaces have a composition of proteins and carbohydrates with which metallic species react. This view is based on the analysis by Cristet al. [29]. Associated silicates were also visible, which get attached to the algae by algal cell wall interactions with silicates within their proximity. According to Dodson etal., during the interaction of the metallic ions with the algae, crystalline Al2O3 and SiO2 are present in the heterogeneous matrix of the algal cell wall [30]. Heritage 2019, 2 2149 Heritage2019, 2 FOR PEER REVIEW 13

Figure 9. FTIR spectrum of blue-green algae. Figure 9. FTIR spectrum of blue-green algae. The IR spectrum of blue-green algae showed the presence of proteins, amide, lipids, aliphatic 4.3. FTIRcarbon, of amides, Water-SolubleFractions and carbohydrates of Aerosols, and the (Figure adsorption 10) of clay minerals on the algal surface. The exterior surfaces have a composition of proteins and carbohydrates with which metallic species 4.3.1.react. Summer This view Season is based Water-Soluble on the analysis Fraction by Crist ofet Aerosols al. [29]. (Figure 10a) TheAssociated summer season silicates water-soluble were also visib fractionsle, which of getaerosols attached revealed to the asymmetric algae by algal stretching cell wall [ 24] of interactions with silicates within their proximity. According to Dodson etal., during the interaction CH2; symmetric stretching [31] of C-H; stretching of CH2 [31];C = O of carboxylic, ketone, or ester [32] of the metallic1 ions with the algae, crystalline Al2O3 and1 SiO2 are present in the heterogeneous matrix 1 at 1729 cm− corresponding to the IR band at 1725 cm− ; stretching of aromatic C = C[33] at 1600 cm− of the algal cell wall [30]. 1 corresponding to the IR band range of 1595–1630 cm− ; C-H deformation of CH2 and CH3 [32] groups 1 - at 14624.3. cmFTIR− ;of O-H Water deformation-SolubleFractions of C-Oof Aerosols stretching (Figure of 10 the) phenolic O-H group or COO stretching and 1 C-H deformation of CH3 groups [34] at 1380 cm− ; C-O stretching and O-H deformation [31] of COOH 1 1 and4.3.1. phenolics Summer at S 1274eason cm W−atercorresponding-Soluble Fraction to of theAerosols IR band (Figure range 10a) of 1260–1280 cm− ; aryl sulfonic 1 1 acid [35]The at 1123 summer cm− seasoncorresponding water-soluble to the fractions IR band of ofaerosols 1121 cm revealed− ; C-O asymmetric stretching andstretch O-Hing deformation[24] of 1 1 of COOHCH2; symmetric and phenolics stretching [31 ][31 at] 1072of C-H cm; stretch− ; aliphaticing of CH C-O-C2 [31];C or = polysaccharidesO of carboxylic, ketone [31], at or 1039ester cm− ; −1 1 −1 1 and[ tri-substituted32] at 1729 cm corresponding aromatic rings to [ 35the] atIR 743band cm at− 1725corresponding cm ; stretching to of the aromatic IR band C at= C 745 [33 cm] at− 1600. cm−1 corresponding to the IR band range of 1595–1630 cm−1; C-H deformation of CH2 and CH3 4.3.2.[32 Rainy]groups Season at 1462 Water-Soluble cm−1; O-H deformation Fraction of of Aerosols C-O stretching (Figure of 10 theb) phenolic O-H group or COO- stretching and C-H deformation of CH3 groups [34] at 1380 cm−1; C-O stretching and O-H The rainy season water-soluble fraction of aerosols showed symmetric stretching of C-H at deformation [31] of COOH and phenolics at 1274 cm−1 corresponding to the IR band range of 1 1 1 29241260 cm−–1280; stretching cm−1; aryl of sulfonic the CH acid2 group [35] at at 1123 2853 cm cm−1 −corresponding; stretching ofto aromaticthe IR band C of= C[112133 cm] at−1; 1597 C-O cm− 1 correspondingstretching and to theO-H IR deformation band range of COOH of 1595–1630 and phenolics cm− ; C-H[31] at bending 1072 cm of−1; aliphatic CH2 and C- CHO-C3 orgroups; 1 COOpolysaccharides anti-symmetric [31 stretching] at 1039 cm [34−1]; atand 1380 tri-substituted cm− ;and C-Oaromatic stretching rings [35 and] a secondaryt 743 cm−1 corresponding skeletal vibrations −1 1 1 of aliphaticto the IR groups band at [74536] cm at 1019. cm− corresponding to the IR band range of 1150–1000 cm− . The IR spectra of the water-soluble fractions of the seasonal dust fall samples showed functional groups4.3.2. of Rainy a wide Season range W ofater organic-Soluble compounds. Fraction of A Withinerosols these (Figure carboxylic 10b) acids, ketones, esters, aromatics, phenolics,The aryl rainy sulfonic season acids, water- polysaccharides,soluble fraction of andaerosols sulfoxides showed couldsymmetric be assessed. stretching It of was C-H interesting at 2924 to notecm that−1; thestretch water-solubleing of the portionCH2 group of the at rainy 2853 cm season−1; stretching profile gave of aromatic few signatures C = C of[33] organic at 1597 compounds cm−1 duecorresp to obviousonding atmospheric to the IR band scavenging range of 1595 of the–1630 aerosols cm−1; C during-H bending the rainy of CH season.2 and CH The3 groups summer; COO season −1 water-solubleanti-symmetric fraction stretching had the [34 most] at 1380 organic cm ;and compound C-O stretching signatures. and secondary The input skeletal of substituted vibrationsbenzene of aliphatic groups [36] at 1019 cm−1 corresponding to the IR band range of 1150–1000 cm−1. ring compounds could be assessed from the IR spectra of summer and winter season water-soluble The IR spectra of the water-soluble fractions of the seasonal dust fall samples showed functional fractions.groups The of water-solublea wide range of compounds organic compounds. in all the seasons Within werethese dominated carboxylic acids, by humic-like ketones, esters, substances (HULIS). HULIS have the characteristics of natural organic matter. Natural organic matter is generally dominated by humic and fulvic substances. Some aspects of the IR spectra showed the presence of soot in the water-soluble samples [37]. Bands at 1729, (summer and winter seasons), 1600 (summer and 1 rainy season), and 1039 cm− (summer season) were in good agreement with bands of soot at Heritage 2019, 2 2150 Heritage2019, 2 FOR PEER REVIEW 14

1 aromatics,1720, 1620, phenolics, and 1040 aryl cm− sulfonic[37]. The acids, presence polysaccharides, of humic acids and couldsulfoxides also becould assessed be assessed. from a similarIt was interestingstudy [38]. to The note water-soluble that the water fraction-soluble of summerportion of season the rainy aerosols season showed profile signatures gave few ofsignatures C-H at 2958 of 1 1 organicand 2928 compounds cm− and due CH2 toat obvious 2859 cm atmospheric− . Humic-like scavenging substances of the were aerosols represented during at the 1729, rainy 1600, season. 1462, 1 1 Th1274,e summerand 1039 season cm− water. Aryl-soluble sulfonic fraction acids showed had the theirmost presenceorganic compound by a band atsignatures. 1123 cm− The. Therefore, input of substitutedan organo-sulfur benzene particulate ring compounds input was could observed be assessed during summers.from the IR Phenolics spectra andof summer organic acidsand winter gave a 1 1 seasonsignature water at- 1072soluble cm −fractionsand carbohydrates. The water-soluble/aliphatic compounds could be assessedin all the atseasons 1039 cm were− , whiledominated the band by 1 humicat 745-like cm− substancouldces be (HULIS). assigned HULIS to aromatic have structures.the characteristics The water-soluble of natural organic winter matter. season Natural aerosols 1 organicshowed matter C-H asymmetric is generally stretching dominated at 2924 by andhumic stretching and fulvic of CH substances.2 at 2854 cm Some− . Bands aspects at 1749, of the 1455, IR 1 spectraand 1268 showed cm− could the presence be attributed of soot to i humic-liken the water substances-soluble samples (HULIS). [37 Sulfur]. Bands compounds at 1729, (summer showed theirand 1 winterpresence seasons) with alkyl, 1600 sulfonic (summer acid and at 1379 rainy cm season)− and, and subsequently, 1039 cm−1 the(summer S=O group season) in sulfoxides were in good was 1 agreementrepresented with by abands band of at 1086soot cmat 1720,− , showing 1620, and a considerable 1040 cm−1 [37 amount]. The p ofresence organo-sulfur of humic compounds acids could in alsothe winterbe assessed season. from The a presencesimilar study of stretching [38]. The and water secondary-soluble vibrations fraction of of aliphaticsummer season groups aerosols could be 1 showedassigned signatures to a band of at C 1145-H at cm 2−958. Theand winter 2928 cm season−1 and soluble CH2 at aerosol2859 cm also−1. Humic showed-like interesting substances features were 1 representedof aromatic at structures: 1729, 1600, tri-substituted 1462, 1274, and aromatic 1039 cm rings−1. Aryl at 740 sulfonic cm− acidsand C-H showed deformation their presence modes by of a a 1 bandmono-substituted at 1123 cm−1. benzeneTherefore, ring an at organo 696 cm-sulfur− . The particulate winter season input in was North observed India is during characterized summers. by Phenolicsunstable atmospheric and organic conditions, acids gave alonga signature with the at stagnation 1072 cm−1 and of aerosols. carbohydrates/aliphatic Therefore, the presence could be of assessedaromatic at structures 1039 cm−1 in, while such anthe environment band at 745 could cm−1 becould ascertained. be assigned The to rainy aromatic season structures. water-soluble The 1 1 waterfraction-soluble showed winter asymmetric season aerosols stretching showed of C-H C-H at asymmetric 2924 cm− andstretch stretchinging at 2924 of CHand2 atstretch 2853ing cm of− . 1 CHC-O2 at stretching 2854 cm−1 of. Bands aliphatic at groups1749, 1455 was, and represented 1268 cm−1 at could 1019 cmbe− attributed, while humic-like to humic- substanceslike substances gave 1 (HULIS).their presence Sulfur at compounds 1463 and 1378 showed cm− . A their previous presence study with showed alkyl that sulfonic humic acid acids at were 1379 enriched cm−1 and in subsequentlyhydroxyl, carbonyl,, the S=O carboxyl, group and in sulfoxides aliphatic groups was represented and relatively by lackinga band in at aromatic 1086 cm groups−1, showing [38]. a considerable amount of organo-sulfur compounds in the winter season. The presence of stretching 4.3.3. Winter Season Water-Soluble Fraction of Aerosols (Figure 10c) and secondary vibrations of aliphatic groups could be assigned to a band at 1145 cm−1. The winter 1 seasonThe soluble winter season aerosol water-soluble also showed fraction interesting of aerosols features showed of symmetric aromatic stretching structures of: C-H tri- atsubstituted 2924 cm− ; −1 1 1 aromaticstretching rings of CH at2 at740 2854 cm cm and− ; ester,C-H aldehyde,deformation or ketonemodes [ 35of] a at m 1749ono cm-substituted− corresponding benzene to ring the IR at band696 −1 1 1 cmrange. The of 1750–1700 winter season cm− ; in CH North2 and CHIndia3 asymmetric is characterized bending by of unstabl aliphaticse atmospheric [21] at 1455 cmconditions− ; alkyl, sulfonic along 1 1 withacid [35the] atstagnation 1376 cm− corresponding of aerosols. Th toerefore the IR band, the at presence 1379 cm − of; C-O aromatic stretching structures and O-H in deformation such an 1 1 environmentof COOH and could phenolics be ascert [31] atained. 1268 cm The− rainycorresponding season water to the-soluble IR band fraction range of showed 1260–1280 asymmetric cm− ; C-O −1 −1 1 stretchstretchinging of and C- secondaryH at 2924 skeletalcm and vibrations stretching of of aliphatic CH2 at groups 2853 cm [36]. atC- 1145O stretching cm− corresponding of aliphatic groups tothe IR −1 1 −1 1 wasband represented range of 1150–1000 at 1019 cm cm−, while; stretching humic vibrations-like substances of the Sgave= O their group presence in sulfoxides at 1463 [35 and] at 1378 1086 cm cm−. 1 1 Acorresponding previous study to the show IR banded that at 1087 humic cm− acids; tri-substituted were enriched aromatic in rings hydroxyl, [35] at 740carbonyl, cm− corresponding carboxyl, and to 1 1 altheiphatic IR band groups at 745 and cm relatively− ;and aryl lacking monosubstituted in aromatic [39 groups] or C-H [38 at]. 696 cm− .

(a)

Figure 10. Cont.

Heritage 2019, 2 2151 Heritage2019, 2 FOR PEER REVIEW 15

(b)

(c)

Figure 10.FTIR spectra of the a) summer, b) rainy season, and c) winter season water-soluble Figure 10. FTIR spectra of the (a) summer, (b) rainy season, and (c) winter season water-soluble fractions of aerosols. fractions of aerosols.

4.3.3. Winter Season Water-Soluble Fraction of Aerosols (Figure 10c) 4.4. SEM Study on Algal Growth (Figure 13a) The winter season water-soluble fraction of aerosols showed symmetric stretching of C-H at To supplement the effect of the impact of algal attack on marble, weathered marble with algal 2924 cm−1; stretching of CH2 at 2854 cm−1; ester, aldehyde, or ketone [35] at 1749 cm−1 corresponding inclusion was subjected to analysis under SEM. The algal growth and its impact on the weathered to the IR band range of 1750–1700 cm−1; CH2 and CH3 asymmetric bending of aliphatics [21] at 1455 marble showed a structure similar to an organo-mineral complex [11]. The fibrillar nature of the cm−1; alkyl sulfonic acid [35] at 1376 cm−1 corresponding to the IR band at 1379 cm−1; C-O stretching cyanobacterial cell wall had penetrated into the marble matrix. The calcite grains showed invasion by and O-H deformation of COOH and phenolics [31] at 1268 cm−1 corresponding to the IR band range small agglomerations of cyanobacterial cells closely attached to each other. Close associations of the of 1260–1280 cm−1; C-O stretching and secondary skeletal vibrations of aliphatic groups [36] at 1145 algal cell formations showed that the weathered zones which had become more degraded had been cm−1 corresponding tothe IR band range of 1150–1000 cm−1; stretching vibrations of the S = O group inhabited by the blue-green algae. Invasion by the cyanobacteria in the calcite mass was evidenced by in sulfoxides [35] at 1086 cm−1 corresponding to the IR band at 1087 cm−1; tri-substituted aromatic cyanobacterial inclusions in the pores, pits, and cleavages. The morphology indicated a major role of rings [35] at 740 cm−1 corresponding to the IR band at 745 cm−1;and aryl monosubstituted [39] or C-H the algal invasion and subsequent colonization on the marble. at 696 cm−1. The SEM images of the algal growth on marble gave imprints of invasion by algal unicellular masses into the marble substrate showing colonization. An organo-mineral assemblage showed that the algal invasion was prominent within the system. The weathered marble mass was impregnated

Heritage 2019, 2 2152 with cyanobacterial colonies scattered within the area. Such algal invasions could naturally result inHeritage the secretion2019, 2 FOR of PEE metabolicR REVIEW organic acids by which calcium oxalate hydrate salts were formed17 on the surface. the algal invasion was prominent within the system. The weathered marble mass was impregnated 4.4.1.with EDS cyanobacterial Analysis of colonies Algae (Figure scattered 13 b)within the area. Such algal invasions could naturally result in the secretion of metabolic organic acids by which calcium oxalate hydrate salts were formed on the The blue-green algae was subjected to qualitative elemental and morphological analysis by an surface. SEM-EDS system, which revealed the following. 4.4.1.The EDS EDS Analysis spectra of ofAlgae the (Figure blue-green 11b) algae showed the presence of P(for phosphates) and C(for carbohydrates). Apart from these, the spectra showed the presence of elements like Fe, The blue-green algae was subjected to qualitative elemental and morphological analysis by an Si, and K associated with the cell structure. The algae takes these elements from the airborne dust and SEM-EDS system, which revealed the following. utilizes them in its metabolic cycle. The presence of soil-oriented elements like Fe, Si, and K in the The EDS spectra of the blue-green algae showed the presence of P(for phosphates) and C(for EDS spectra of the algae addresses the same process. The SEM images of the algae showed that the carbohydrates). Apart from these, the spectra showed the presence of elements like Fe, Si, and K algal cell walls had a chlorophyllous structure, testifying the organic nature. Within this structure, associated with the cell structure. The algae takes these elements from the airborne dust and theutilize presences them of microin its metabolic particles showed cycle. The the presence possible adsorptionof soil-oriented of metal elements particles like onFe, theSi, and algal K cell in the walls. AccordingEDS spectra to Crist of the et algae al.,in address this scenario,es the same Si, Fe, process and Al. elementsThe SEM concentrateimages of the at algae the cell showed wall surfacethat the by adsorbingalgal cell onto walls the had surface a chlorophyllous functional groupsstructure [29, ].testifying the organic nature. Within this structure, the presence of micro particles showed the possible adsorption of metal particles on the algal cell 4.4.2. EDS Analysis (Figure 13c) walls. According to Crist et al.,in this scenario, Si, Fe, and Al elements concentrate at the cell wall surfaceThe blue-green by adsorbing algae onto (cyanobacteria) the surface functional which growsgroups on [29 the]. calcitic mass of the monument showed a chlorophyllous matrix cell structure based on natural organic polymers like proteins, sugars, and4.4.2. phosphates. EDS Analysis Some (Figure evidence 11c) of other microbial mass like fungal strains could also be ascertained. EvidenceThe blue of-green possible algae metal (cyanobacteria) particulates embedded which grow ons theon algal the calcitic mass could mass beof identified the monument by EDS in theshowed SEM a images. chlorophyllous The essentially matrix plant-basedcell structure morphological based on natural structure organic also polym showeders like traces proteins, of metal particlesugars inclusions, and phosphates. on the Somechlorophyllous evidence of base. other The microbial elemental mass analysis like fungal by strainsEDS gave could imprints also be of phosphatesascertained. and carbon, and traces of Si, K, and Fe adsorbed on the surface of the algae. TheEvidence SEM image of possible of fresh metal marble particul showsates embedded (Figure 11 ona) athe closed algal knitmass structure,could be identified wherein by the EDS grain boundariesin the SEM were images. well-defined. The essentially The structure plant-based was morphological a compact one. structure The matrix also showed showed perfect traces of crystalline metal features,particle and inclusions the interfaces on the chlorophyllous in the structure base. were The coherent. elemental The analysis calcium by EDS percentage gave imprints in the ofEDS (Figurephosphates 11b,c) and was carbon around, and 97%, traces with of some Si, K, silica and Fe (around adsorbed 3%). on the surface of the algae.

FigureFigu 11. re(a )12. SEM a) SEM image image of fresh of fresh marble marble (marble (marble used used in conservation); in conservation) (b). EDS; b) EDS spectrum, spectrum, (c) elementc) analysis data from EDS element analysis data from EDS

The SEM image of fresh marble shows (Figure 12a) a closed knit structure, wherein the grain boundaries were well-defined. The structure was a compact one. The matrix showed perfect

Heritage2019, 2 FOR PEER REVIEW 18

Heritage 2019, 2 2153 crystalline features, and the interfaces in the structure were coherent. The calcium percentage in the EDS (Figure 12b,c) was around 97%, with some silica (around 3%). TheThe SEM imagesimages showedshowed the the weathering weathering features featur ofes theof marble,the marble, as compared as compared with thewith fresh the marble fresh marblesample. sample. Pits, pores, Pits, andpores, cracks and were cracks visible were in visible the crust. in the The crust. presence The p ofresence an amorphous of an amorphous layer may layer have maybeen have formed been by formedthe action by of the water action and of further water transformations and further transformations in the physical in and the chemical physical profile. and chemicalThe fractures profile. were The uneven, fractures which were showeduneven, the which impact showed of water the impact percolation. of water Since percolation. the amorphous Since thelayer amorphous of the crust layer was of less the crystalline crust was comparedless crystalline to the compared fresh marble, to the the fresh interfaces marble, showed the interfaces that the showedexisting that matrix the had existing less coherence matrix had in theless calcite coherence grains in and the boundaries calcite grains compared and boundaries with the fresh compared marble. withThe EDSthe fresh spectra marble. showed The less EDS weight spectra % ofshowed Ca compared less weight with % the of freshCa compared marble and with also the the fresh presence marble of andFe and also Mn theas presence additional of Fe transition and Mn metalsas additional on the transition crust. metals on the crust. TheThe SEM SEM image image (Figure (Figure 13a,b)12a,b) of of a a black black crust crust sample sample showed showed a a topography topography where where the the grain grain boundariesboundaries in in the calcitic massmass werewere looseloose and and scattered; scattered an; an amorphous-like amorphous-like coating coating was was visible; visible and; and the theweathering weathering pattern pattern was was visible visible in in the the form form of of pits, pits, pores, pores, cracks, cracks,and and crevices.crevices. Amorphous layers layers indicatedindicated the the lower lower cry crystallinestalline nature nature of of the the specimen. specimen. The The structure structure had had imprints imprints of of weathered weathered marblemarble mass. TheThe impact impact of ofhydration hydration could could be assessed, be assessed which, which naturally naturally indicated indic a lowerated crystalline a lower crystallinestructure. Thestructure. EDS spectra The EDS (Figure spectra 12c,d)showed (Figure 13c,d) theshowed presence the of presence elements of like elements Mn, Fe, like Al, andMn, SiFe, apart Al, andfrom Si the apart calcite. from The the presencecalcite. The of Sipresence was from of theSi was calcite from structure, the calcite whereas structure, Al, Mn, whereas and Fe Al, could Mn, haveand Febeen could from have the be crustalen from input the orcrustal from inp anthropogenicut or from anthropogenic sources. sources.

Figure 12. (a,b) Scanning electron microscopy (SEM) images of Taj Mahal marble black crust, and (c) EDS spectra with (d) elemental anlysis Figure 13. a, b)Scanning electron microscopy (SEM) images of Taj Mahal marble black crust, and c) EDS spectra with d) elemental anlysis 4.5. SEM-EDS Spectra of Airborne Dust (Figure 15) 4.5. SEMThe-EDS EDS S spectrapectra of ofAirborne airborne Dust dust (Figure represented 14) an annual pattern of composite airborne dust. TheThe elemental EDS spectra composition of airborne depicted dust a profile represented dominated an annual by soil-oriented pattern of elements composite (crustal airborne elements), dust. Thelike Na, elemental Mg, Al, composition Si, K, and Ca. depicted Some impressions a profile of d anthropogenicominated by elementssoil-oriented could elements be assessed (crustal by the elements)presence, of like Ti, V, Na, Mn, Mg, Fe, Al, and Si, Ni. K,Fe and could Ca. be Some from impressions soil sources, of as anthropogeni well as from anthropogenicc elements could inputs. be assessedThe by elemental the presence composition of Ti, V, Mn, of the Fe,dust and Ni. by EDSFe could gave be the from soil-oriented soil sources elemental, as well as profile. from anthropogenicSome elements input likes. Na, Mg, Al, Si, K, and Ca had a crustal origin; Fe and Mn could have been fromThe soils elemental or an anthropogenic composition source; of the anddust Ni, by Cu, EDS V, gave and Ti the indicated soil-oriented an anthropogenic elemental profile. origin. Some In the elementsoverall elemental like Na, Mg, characterization, Al, Si, K, and theCa basehad a of crustal the dust origin had; aFe crustal and Mn origin, could while have inputsbeen from of industrial soils or ansignatures anthropogenic were visible. source; The and airborne Ni, Cu, dustV, and composition Ti indicated showed an anthropogenic features of a typicalorigin. crustalIn the overall aerosol. elementalThe EDS spectrum characterizati showedon, the that base the ratio of the of dustSi/Al hadwas 2.96a crustal and ratio origin of, Fewhile/Al was inputs 0.95. of These industrial were signaturesin agreement were with visible. the Si The/Al airborne ratio of 2.7 dust and composition the Fe/Al ratio showed of 1.3 features for crustal of a aerosols,typical crustal as reported aerosol. by TheRahn EDS [40 spectrum]. The elements showed represented that the ratio showed of Si/Al the was lithophillic 2.96 and natureratio of of Fe/Al the dust. was 0 The.95. elementalThese were K /inFe agreementratio obtained with by the EDS Si/Al analysis ratio wasof 2.7 0.47, and which the Fe/Al was in ratio good of agreement 1.3 for crustal with aaerosols value of, as 0.4 reported for airborne by coarse crustal material [41].

Heritage 2019, 2 2154 Heritage2019, 2 FOR PEER REVIEW 16

FigureFigure 13. Scanning 11.Scanning electron electron microscopy microscopy ( (SEM)SEM) image image of ofa) algal (a) algal growth growth on marble on marble and b) algae and, ( band) algae, and (c) the energy dispersivec) the energy spectroscopy(EDS) dispersive spectroscopy spectrum(EDS of) algae. spectrum of algae.

The wt% of Fe as analyzed by EDS in the airborne dust was 7.2%, which was near the average weight4.4. % SEM value Study of 6.7% on Algal of Asian Growth dust. (Figure Therefore, 11a) the airborne dust represented a characteristic feature which resembled the nature of Asian dust [42]. To supplement the effect of the impact of algal attack on marble, weathered marble with algal The SEM images of the airborne dust in lesser magnifications showed a soil mineral matrix. inclusion was subjected to analysis under SEM. The algal growth and its impact on the weathered The particlesmarble showed demonstrated a structure a major similar aluminosilicate to an organo-mineral matrix with complex certain [11]. additions. The fibrilla Ther nature additions of the were the presencecyanobacterial of micro cell wall metal had particles penetrated embedded into the marble within matrix. the dust. The calcite The soilgrains mineral showed particles invasion were characterizedby small agglomerations by irregular-shaped, of cyanobacterial rectangular, cells or cl rhomboidalosely attached particles. to each other. The aluminosilicateClose associations particles of werethe associated algal cell with formations agglomerate showed formations that the weathered in which zones the particles which had were become closely more attached degraded to each had other. Thebeen SEM inhabited images by the showed blue-green dust algae. particles Invasion with by irregular the cyanobacteria habits: octagonal in the calcite and mass rhomboidal. was Morphologicalevidenced by analysis cyanobacterial showed inclusions that small in the particles pores, pits were, and attachedcleavages. toThe large morphology particles. indicated The dust particlesa major were role attached of the algal in closeinvasion proximity; and subsequent this could colonization be due toon the the strongmarble. cohesive forces within the The SEM images of the algal growth on marble gave imprints of invasion by algal unicellular particles. The presence of a dry environment like Agra, which falls in to the category of a semi-arid masses into the marble substrate showing colonization. An organo-mineral assemblage showed that zone of India, could be a factor for such a particle habit. Some voids and minute gaps could be seen due to the presence of these odd-shaped particles. Iron oxides in the dust get deposited on the monument surfaces by wind action. Iron aids in crust formation. Iron-rich particles can act as catalysts in various mechanisms, leading to stone decay. Such a phenomenon has been reported by Schiavonet al. [43]. Heritage2019, 2 FOR PEER REVIEW 20

Heritagecatalysts2019 in, 2various mechanisms, leading to stone decay. Such a phenomenon has been reported2155 by Schiavonet al. [43] . The microorganisms present in the weak zones of the monument can utilize the iron oxides and relatedThe elements microorganisms for their presentmetabolic in theactivity.SEM weak zones images of the monumentof the dust canparticles utilize gave the irona soil oxides-oriented and profilerelated and elements also indicated for their particles metabolic that activity.SEM could be from images anthropogenic of the dust activity. particles The gave SEM a soil-orientedimages were profiledominated and by also irregular indicated-shaped particles particles that could, which be indicated from anthropogenic crustal material activity., but The to some SEM imagesextent, some were metaldominated input bylike irregular-shaped iron oxides, as shown particles, by whichEDS analysis, indicated could crustal be ass material,essed. but to some extent, some metalAirborn input likee dusts iron oxides, tend to as accumulateshown by EDS on analysis, the sensitive could be and assessed. weak weathered zones of the monumentAirborne and dusts can aid tend in to crust accumulate formation. on theSuch sensitive a study andwas weakgiven weathered by Torok etal zones., which of the opined monument that dustand canand aid black in crustcrust formation.samples from Such a study wasbuildings given could by Torok be used etal., as which environment opined thatal indicators dust and sinceblack crustboth samplesdust and from crust limestone accumulate buildings air pollutants could be andused act as environmental as memories of indicators the past since pollution both leveldust[ and44]. crust accumulate air pollutants and act as memories of the past pollution level [44]. Calcium can be leached from limestone surfaces or chelated, once solubilized from from the the matrix, matrix, by hexauronic acids, and car carboxylboxyl and hydrohydroxylxyl groups [ 45]].Organic.Organic acids like oxalic, citric, citric, gluconic, malic, succinic, amino, and and uronic acids may react with the stone via salt formation and complexation [ 46].According].According to SaizJiminez and Hermosin, the black crust coatings on the the st structuresructures of bui buildinglding materials located in urban environments have all kinds of organic compounds present in aerosols and particulate matter, which are transferred by dry or wet deposition. The composition of each crust crust is is governed governed by by the the composition composition of the of thevehicular vehicular emissions, emissions, and diesel and diesel engines engines have a have strong a stronginfluence influence [47]. However, [47].However the direct, the impact direct ofimpact humic-like of humic matter-like on matter the marble on the substrate marble wassubstrate difficult was to difficultassess. Finally, to assess. careful Finally, examination careful examination of the black of crust the onblack marble crust by on EMS marble imaging by EMS clearly imaging showed clearly the presenceshowed t ofhe airbornepresence carbon of airborne particulate carbon matters. particulate The matters. latest search The ofsuchlatest search particulates ofsuch has particulates revealed thathas revealthese,ed in appreciablethat these, in quantity, appreciable contain quantity carbon, contain under acarbon nano domainunder a as nano carbon domain nano as tube, carbon graphene nano tube,oxide, graphene and nano oxide carbon, and dots. nano Such carbon nano dots. carbons Such are nano known carbons to produce are known reactive to produc oxygene reactive species (ROS)oxygen inair species and sunlight (ROS) in [48air– 50 and]. The sunlight readily [ available48−50]. The gaseous readily nitrogenous available pollutants gaseous produced nitrogenous by pollutantauto exhaustss produced and refineries by auto whenreacting exhausts and with refineries ROS readily when producereacting reactive with nitrogen ROS readily species produce (RNS). Thesereactive are nitrogen capable ofdestroying species (RNS). marble These surfaces, are inflicting capable permanentofdestroying damage marble to monuments surfaces, inflicting like the Tajpermanent Mahal. The damage presence to monument of nano carbons like dots the ofTaj sizes Mahal. smaller The than presence 5 nm in of the nano black carbon crust candots be of clearly sizes visualizedsmaller than in 5 the nm TEM in the images black (Figurecrust can 14 ).be clearly visualized in the TEM images (Figure 15).

Figure 15. Transmission electron microscopy (TEM) images: Left side: low resolution showing the Figure 14. Transmission electron microscopy (TEM) images: Left side: low resolution showing the presence of assorted nano carbon particles of different shapes and sizes. Right side: a focused presence of assorted nano carbon particles of different shapes and sizes. Right side: a focused zoomed zoomed resolution image showing the nano carbon particles (black dense spots) of less than a 5 nm resolution image showing the nano carbon particles (black dense spots) of less than a 5 nm size. size.

5. Conclusion Characterization of the airborne atmospheric species from abiological and biological natural sources and from anthropogenic origins that interact with the surface of the Taj Mahal monument has been conducted. Ingredients present in the environmental pollutant have been shown to be

Heritage2019, 2 FOR PEER REVIEW 19

Rahn [40]. The elements represented showed the lithophillic nature of the dust. The elemental K/Fe ratio obtained by EDS analysis was 0.47, which was in good agreement with a value of 0.4 for Heritage 2019, 2 2156 airborne coarse crustal material [41].

FigureFigure 15. 14. (a,b) a,b)ScanningScanning electronelectron m microscopyicroscopy (SEM (SEM)) and and c) (energyc) energy dispersive dispersive spectroscopy spectroscopy(EDS)(EDS) spectrum of compositespe airbornectrum of dust composite (d) elemenatal airborne anlysisdust d) elemenatal anlysis

The wt% of Fe as analyzed by EDS in the airborne dust was 7.2%, which was near the average 5. Conclusion weight % value of 6.7% of Asian dust. Therefore, the airborne dust represented a characteristic featureCharacterization which resembled of the the airbornenature of atmosphericAsian dust [42 species]. from abiological and biological natural sourcesThe and SEM from images anthropogenic of the airborne origins dust that in interactlesser magnifications with the surface showed of the a soil Taj mineral Mahal monument matrix. The has beenparticles conducted. demonstrated Ingredients a major present aluminosilicate in the environmental matrix with certain pollutant additions. have been The additions shown to were be natural, the whichpresence were of augmented micro metal by particles anthropogenic embedded activity. within It the is stressed dust. The here soil that mineral beyond particles common were dust, pollutantcharacterized gases, by and irregular carbon- particulates,shaped, rectangular the atmospheric, or rhomboidal aerosol was particles. also comprised The aluminosilicate of microbial speciesparticles and were carbon associated dust with with a size agglomerate under the formations nano domain. in which These the highly particles reactive were species closely participate attached in alliedto each metabolic other. processes upon the marble matrix of the monument. In this process, inorganic crustal The SEM images showed dust particles with irregular habits: octagonal and rhomboidal. minerals like airborne dust and airborne carbon particulates including nano carbons, organic aerosols, Morphological analysis showed that small particles were attached to large particles. The dust natural bio-organic matter like Hulis, and cyanobacterial cellular events, act to create the weathering particles were attached in close proximity; this could be due to the strong cohesive forces within the phenomena of the marble surface a complex one. The visible impact of such an amalgamated complex particles. The presence of a dry environment like Agra, which falls in to the category of a semi-arid reaction has been the degradation and discoloration of the marble surface. The atmospheric inputs zone of India, could be a factor for such a particle habit. Some voids and minute gaps could be seen getdu addede to the to presence a process of of these more odd complex-shaped biochemicals particles. Iron involving oxides in free the dustradical-like get deposited reactive on oxygen the speciesmonument [48–50 surfaces] to contribute by wind to action. the weathering Iron aids mechanisms. in crust formation. A recent Iron report-rich particle on thes erosioncan act of as the Aravalli mountain range showed that human activity extending the Thar Desert that enhanced dust storms drifted by the wind current toward the site of the discussion augmented the degradation process [51]. A clear strategy needs to be developed to prevent the accumulation of such reactive species on the surface of the monument vis-a-vis its surrounding environment. However, it is true that we have to maintain a globally clean environment. It will not help much to clean only the nearby zone as Heritage 2019, 2 2157 aerosol particles are global and are not confined to the place of their origin, but drift all over the globe. At present , a massive tree plantation in the nearby area with frequent surface monitoring, maintenance, and restoration of the affected surface of the monument by certified treatment would be the only viable option to add life span to the monument.

Author Contributions: D.B. collected samples through field work from the building site and other sources and the raw images and the relevant data were extracted from the samples in the laboratory and analyzed under the supervision of S.S. The first draft manuscript was written by D.B. and then both the authors worked on this draft, which was finally checked by S.S. Both the authors have given approval to the final version of the manuscript. Funding: Initial funding for this research was provided by a UNESCO nominated PhD grant to D.B. The sustained financial support from SERB-DST, Government of India, New Delhi, to S.S. is gratefully acknowledged. Acknowledgments: DB thanks Dr. Christian Manhart of the UNESCO for nominating the author for a PhD grant. Thanks are also due to Dr. D. V. Sharma, Dr. N. K. Samadhiya, Dr. K. P. Poonhacha, Mrs. Kasturi Gupta Menon, DGASI for their keen interest in the work. SS thanks DST-SERB, Government of India, N. Delhi, for sustained research funding. Conflicts of Interest: The authors declare no conflict of interest.

Abbreviations

ROS Reactive Oxygen Species TTZ Taj Trapezium Zone PM Particulate Matter ADA Agra Development Authority DG Diesel Generator SPM Suspended Particulate Matter Scanning Electron Microscopy (SEM) cum Energy SEM-EDS Dispersive Spectroscopy(EDS) TEM Transmission Electron Microscopy HULIS humic like substances RNS reactive nitrogen species XRD X-Ray Diffraction HSD High Speed Diesel LPG Liquefied petroleum gas IR Infra Red FTIR Fourier Transformed Infra Red

References

1. Agarwal, M.; Singh, B.; Rajput, M.; Marshall, F.; Bell, J.N.B. Effect of air pollution on peri-urban agriculture: A case study. Environ. Pollut. 2003, 126, 323–329. 2. Atash, F. The Deterioration of urban environments in developing countries Mitigating the air pollution crisis in Tehran, Iran. Cities 2007, 24, 399–409. 3. Agra Environment Management Plan; Central Pollution Control Board, Ministry of Environment & Forests, Government of India, Agra Office: Agra, Uttar Pradesh, India, January 2002. 4. Hicks, B.B.; Kumari, M. Marble discoloration at the Taj Mahal: A proposed explanation. In Proceedings of the ICOMOS 8th General Assembly and International Symposium, Washington, DC, USA, 7–15 October 1987; pp. 325–332. 5. Sharma, R.K.; Gupta, H.O. Dust Pollution at the Taj Mahal—A case study. In Proceedings of RILEM/UNESCO Congress; Thiel, M.J., Ed.; E & F. N. Spon: London, UK, 1993; pp. 11–18. 6. Kumar, R.; Rani, A.; Kumari, K.M.; Srivastava, S.S. Direct measurement of atmospheric dry deposition to material surfaces in a semi arid region of north central India. J. Geophys. Res. 2003, 108, 4625. [CrossRef] 7. Kumar, R.; Rani, A.; Singh, S.P.; Kumari, K.M.; Srivastava, S.S. Measurements of dry deposition of gaseous and particulate sulphur on marble at a suburban site. Ind. J. Radio Sp. Phys. 2002, 31, 88–92. 8. Kulshreshtha, U.C.; Saxena, A.; Kumar, N.; Kumari, K.M.; Srivastava, S.S. Mass size distribution of aerosols at a suburban site of Agra. Ind. J. Radio Sp. Phys. 1995, 24, 178–183. Heritage 2019, 2 2158

9. Bergin, M.H.; Tripathi, S.N.; Jaidevi, J.; Gupta, T.; Mckenzie, M.; Rana, K.S.; Shafer, M.M.; Villalobos, A.M.; Schauer, J.J. The discolouration of the Taj Mahal due to particulate Carbon and dust deposition. Environ. Sci. Technol. 2015, 49, 808–812. 10. Tabasso, M.L. ICCROM Report of the Mission to Agra. Satdhara and Sanchi UNESCO Contract no 3970367; ICCROM: Rome, Italy, March 1997; pp. 16–24. 11. Banerjee, D.; Sarkar, S. Chemistry and Deposition of Airborne Particulates on the Taj Mahal at Agra India. Natursteinsanierung. In Proceedings of the Natural and Building Stones, Stuttgart, Germany, March 11–12 2016; pp. 119–129. 12. Toniolo, L.; Zerbi, C.M.; Bugini, R. Black layers on historical architecture. Environ.Sci. Pollut. Res. 2009, 16, 218–226. 13. Del Monte, M.; Ausset, P.; Lefevre, R.A. Evidence of pre-industrial air pollution from the Heads of the kings of Juda statues from NotreDame Cathedral in Paris. Sci. Total Environ. 2001, 273, 101–109. 14. Genestar, C.; Pons, C.; Cerro, J.C.; Cerda, V. Different decay patterns observed in a nineteenth-century building (Palma, Spain). Environ. Sci. Pollut. Res. 2014, 21, 8663–8672. [CrossRef] 15. Parmar, R.S.; Satsangi, G.S.; Kumari, M.; Lakhani, A.; Srivastava, S.S.; Prakash, G.S. Study of size distribution of atmospheric aerosol at Agra. Atmos. Environ. 2001, 35, 693–702. 16. Office of the Registrar General 2011, Tables on Houses, Household Amenities and Assets, Census of India, Vital Statistics Division; Ministry of Home Affairs: New Delhi, India, 2011. 17. District Profile. Available online: https://agra.nic.in/district-profile/ (accessed on 8 July 2019). 18. Kumar, R.; Srivastav, S.S.; Kumari, K.M. Characteristics of Aerosols over Suburban and Urban Site of Semiarid Region in India: Seasonal and Spatial variations. Aerosol. Air Qual. Res. 2007, 7, 531–549. 19. Swanson, H.E.; Tatge, E. Standard X-ray Diffraction Powder Patterns; National Bureau of Standards: Washington, DC, USA, 1962. 20. Keene, G.; van der Merwe, D. Classification of Toxic Cyanobacterial Blooms by Fourier Transform Infrared Technology. Adv. Microbiol. 2013, 3, 1–8. 21. Filip, Z.; Hermann, S. An Attempt to differentiate Pseudomonas spp. And other soil bacteria by FTIR spectroscopy. Eur. J. Soil Biol. 2001, 37, 137–143. 22. Artz, R.R.E.; Chapman, S.J.; Robertson, A.H.J.; Potts, J.M.; Defarge, F.L.; Gogo, S.; Comont, L.; Disnar, J.R.; Francez, A.J. FTIR spectroscopy can be used as a screening tool for organic matter quality in regenerating cutover peatlands. Soil Biol. Biochem. 2008, 40, 515–527. 23. Ramasamy, V.; Ponnusamy, V. Analysis of air suspended particles in Coimbatore—A FTIR study. Ind. J. Phys. 2009, 83, 301–312. 24. Gualteri, M.; Andrioletti, M.; Mantecca, P.; Vismara, C.; Camatini, M. Impact of tire debris on in vitro and in vivo systems. Part. FibreToxicol. 2005, 2, 1. [CrossRef] 25. Chun, Y.; Shing, G.; Chiou, L.T. Evaluation of Current Techniques for Isolation of Chars as Natural Adsorbents. Environ. Sci. Technol. 2004, 38, 4227–4232. 26. Centrone, A.; Brambilla, L.; Renouard, T.; Gherghel, L.; Mathis, C.; Mullen, K.; Zerbi, G. Structure of new carbonaceous materials: The role of vibrational spectroscopy. Carbon 2005, 43, 1593–1609. 27. Bennett, D.; Angove, M.J.; Wells, J.D.; Johnson, B.B.; Baldwin, D. Characterisation of bushfire residues and their leachates, 3rd Australian New Zealand Soil Conference, SuperSoil 2004, 5–9 December 2004, University of Sydney, Australia, Published on CDROM. Website. Available online: www.regional.org.au/au/asssi/ (accessed on 5 December 2004). 28. Havers, N.; Burba, P.; Lambert, J.; Klockow, D. Spectroscopy Characterisation of Humic Like Substances in Airborne Particulate Matter. J. Atmos. Chem. 1998, 29, 45–54. 29. Guo, V.; Bustin, R.M. FTIR spectroscopy and reflectance of modern charcoals and fungal decayed woods: Implications for studies of intertinite in coals. Int. J. Coal Geol. 1998, 37, 29–53. 30. Enev, V.; Pospisilova, L.; Klucakova, M.; Liptaj, T.; Doskocil, L. Spectral characterization of selected Humicsubstances. Soil Water Res. 2014, 9, 9–17.

31. Khare, P.; Baruah, B.P.; Rao, P.G. Water soluble organic compounds (WSOMs) in PM2.5 and PM10 at a subtropical site of India. Tellus 2011, 63, 990–1000. 32. Senesi, N.; Tetsini, C.; Polemio, M. Chemical and spectroscopic characterization of soil organic matter fractions isolated by sequential extraction procedure. J. Soil Sci. 1983, 34, 801–813. Heritage 2019, 2 2159

33. Chatterjee, R.K.; Gupta, D.S. Clay minerals in some Western Uttar Pradesh soils. J. Ind. Soc. Soil Sci. 1970, 18, 391–396. 34. Usher, C.R.; Michel, A.E.; Grassian, V.H. Reactions on mineral dust. Chem. Rev. 2003, 103, 4883–4939. 35. White Joe, L. Interpretation of infrared spectra of soil minerals. Soil Sci. 1971, 112, 22–31. 36. Rahn, K.A. Silicon and aluminium in atmospheric aerosols: Crust-air fractionation. Atmos. Environ. 1976, 10, 597–601. 37. Lawson, D.R.; Winchester, J.W. Sulfur and crustal reference elements in non urban aerosols from Squaw mountain, Colorado. Environ. Sci. Technol. 1978, 12, 716–721. 38. Jeong, G.Y.; Park, M.Y.; Kandler, K.; Nousiainen, T.; Kempinen, O. Mineralogical properties and internal structures of individual fine particles of Saharan dust. Atmos. Chem. Phys. 2016, 16, 12397–12410. 39. Schiavon, N.; Zhou, L. Magnetic chemical and microscopical characterization of urban soiling on historical monuments. Environ. Sci. Technol. 1996, 30, 3624–3629. 40. Torok, A.; Licha, T.; Simon, K.; Siegesmund, S. Urban and rural limestone weathering; the contribution of dust to black crust formation. Environ. Earth Sci. 2010, 63, 675–693. [CrossRef] 41. Crist, R.H.; Oberhoser, K.; Shank, N.; Nguyen, M. Nature of bonding between metallic ions and algal cell walls. Environ. Sci.Technol. 1981, 15, 1212–1217. 42. Dodson, J.K.; Aronson, J.M. Cell wall composition of Enteromorpha intestinalis. Bot. Mar. 1978, 21, 241–246. 43. Chughtai, R.; Jassim, J.A.; Peterson, J.H.; Stedman, D.H.; Smith, D.M. Spectroscopic and solubility characteristics of oxidized soots. Aerosol Sci. Technol. 1991, 15, 112–126. 44. Peng, P.; Zhao, J.; Song, J.; Ma, S. Humic acid, Kerogen and black carbon isolated from atmospheric Total Suspended Particulate from Gungzhoun China. Aerosol Sci. Technol. 2013, 47, 1342–1352. 45. Perry, T.D.; Duckworth, O.W.; McNamara, C.J.; Martin, S.T.; Mitchell, R. Effects of the Biologically Produced Polymer Alginic acid on Macroscopic and Microscopic Calcite Dissolution Rates. Environ. Sci. Technol. 2004, 38, 3040–3046. 46. Sand, W.; Jozsa, P.G.; Mansch, R. Environmental Microbiology; G. Briton Ltd.: New York, NY, USA, 2002; Volume 6, pp. 3364–3375. 47. Jiminez, C.S.; Hermosin, B. Black crusts in the European built environment. Corr. Rev. 2004, 22, 381–393. 48. Dutta, T.; Sarkar, R.; Pakhira, B.; Ghosh, S.; Sarkar, R.; Barui, A.; Sarkar, S. ROS generation by reduced graphene oxide (rGO) induced by visible light showing antibacterial activity: Comparison with graphene oxide (GO). RSC Adv. 2015, 5, 80192–80195. 49. Sonkar, S.K.; Tripathi, S.; Sarkar, S. Activation of aerial oxygen to superoxide radical by carbon nano tubes in indoor spider web trapped aerosol. Curr. Sci. 2009, 97, 1227–1230. 50. Tripathi, K.M.; Singh, A.; Bhati, A.; Sarkar, S.; Sonkar, S.K. Sustainable Feasibility of the Environmental Pollutant Soot to Few-Layer Photoluminescent Graphene Nanosheets for Multifunctional Applications. ACS Sustain. Chem. Eng. 2016, 4, 6399–6408. 51. Available online: https://www.downtoearth.org.in/news/environment/behind-intense-dust-storms-in-north- west-india-lies-withered-aravallis-60873 (accessed on 19 June 2018).

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).