Indian Journal of Radio & Space Physics Vol 43, August - October 2014, pp 284-292 Chemical characterization of particulate matter at Sinhagad, a high altitude station in Pune, India P Gursumeeran Satsangi1,$,*, Suresh P Chavan2, P S P Rao2 & P D Safai2 1Department of Chemistry, University of Pune, Pune 411 007, India 2Indian Institute of Tropical Meteorology, Pashan, Pune 411 008, India $E-mail: [email protected] Received 27 January 2014; revised 25 August 2014; accepted 5 September 2014 Particulate matter, PM10 and PM2.5, samples were collected at Sinhagad, a high altitude location, near Pune, India during November 2008 - April 2009. The average concentrations of PM10, PM2.5 and PM10-2.5 at Sinhagad were 35.8, -3 14.1 and 21.7 µg m , respectively. The average ratio of PM2.5/PM10 (0.39) suggested that PM10 at study area is dominated by primary particulate emissions by natural activities. In PM10, anions and cations contributed 33% and 67%, whereas in + - 2+ PM2.5, these were 43% and 57%. In both PM10 and PM2.5, contribution of marine components, viz. Na , Cl and Mg were found to be 58% and 49%, respectively reflecting Arabian Sea is the major source of these components. All the ionic 2- - + components in PM10 showed higher concentration in summer, whereas in PM2.5, secondary particles (SO4 , NO3 and NH4 ) 2+ 2+ + + showed higher concentration in winter. The order of neutralization factor was found to be Ca > Mg > NH4 > K for 2+ + 2+ + PM10; and Ca > NH4 > Mg > K for PM2.5. Source categorization, i.e. marine, crustal and anthropogenic of chemical components of PM has been done. Sea salt and crustal fractions have been calculated by assuming entire Na and Ca from Sea and crust, respectively. The fraction of the chemical component, which remains after deducting the sea and crust fractions, has been considered as of anthropogenic origin. Major contribution observed was from marine sources [PM2.5 (43%) and PM10 (53%)]; followed by crustal sources [PM2.5 (25%) and PM10 (30%)]; and then anthropogenic sources [(PM2.5 (32%) and PM10 (17%)]. Keywords: Particulate matter, Chemical composition, Air pollution, Aerosol PACS Nos: 92.60.Sz; 82.33.Tb 1 Introduction or metals. Fine sulphate and nitrate particulates are Particulate air pollution is a complex mixture of formed when SO2 and NOx condense in the small and large particles of varying origin and atmosphere. The major neutralizing species in the chemical compositions. Particulate matter (PM) have atmosphere are NH3 and CaCO3, and their relative strong influence in many atmospheric processes, with dominance over a particular region can be ascertained important environmental effects including changes in by comparing their abundance in precipitation3,4. The visibility, solar radiation transfer (related with global large sources of fine particle are fuel combustion in warming), cloud formation, and play a major role in industries and diesel exhaust from vehicular traffic. the acidification of clouds, rain and fog1,2. The fine Important information on the origin of particulate airborne particles have high probability of deposition matter can be obtained through chemical analysis5-17. deeper into the respiratory tract and are likely to The aerosol composition is highly variable in space trigger or exacerbate respiratory diseases. These and time and depends upon the relative contribution particles also have higher burdens of toxins, which from diverse sources such as sea salts, mineral dust when absorbed in the body can result in health and anthropogenic emissions as well as on the consequences other than respiratory health effects. meteorological conditions18. Many components can be Particles, having 2.5-100 µm diameters, usually used as tracers for specific sources, for example comprise more of dust from agriculture, construction, sodium is a tracer that is almost exclusively road traffic, plant pollens and other natural sources. associated with sea salt. The degree of the acidity of Smaller particles, with less than 2.5µm diameter, deposition depends on neutralization by certain + 2+ generally come from combustion of fossil fuels. alkaline components, such as NH4 , Ca [in the form These particles include soot from vehicle exhaust and of CaCO3 or Ca(OH)2], Na and Mg. The objective of are often coated with various chemical contaminants the present study is to investigate: (i) variation in SATSANGI et al: CHEMICAL CHARACTERIZATION OF PARTICULATE MATTER AT SINHAGAD 285 2- - concentrations of major acidifying (SO4 and NO3 ) sampling location and about 100 m below the 2+ + and alkaline (Ca and NH4 ) constituents of sampling height. Thus, the site is relatively free from particulate matter (PM10 and PM2.5); (ii) their effect on major urban pollution sources. Sampling was carried the acidification/neutralization potential of out in the complex of a Microwave Tower building particulate; and (iii) quantification of sources of PM10 (about 10 m) owned by Bharat Sanchar Nigam and PM2.5. The data revealed from the present study Limited (BSNL), Government of India, at Sinhagad can be useful for the other studies as this site is free fort. It is a protected site and trespassers or tourists from the local pollution sources. are not allowed to enter. Figure 1 depicts the exact location of Sinhagad site. 2 Materials and methods 2.1 Sampling site 2.2 Sample collection ′ ′ Sinhagad (18°21 N and 73°45 E, 1450 amsl) is a PM10 and PM2.5 samples were collected from hill station on a mountaintop in the Western Ghats November 2008 to April 2009 at Sinhagad using an mountain range. It is located at about 18 km air sampler (APM-550 from Envirotech Pvt Ltd, southwest of Pune (18°32′N, 73°51′E). Its top is flat India,). PM10 and PM2.5 sampler is based on designs with an area of about 0.5 km2. Other mountain peaks standardized by US EPA, Omni-directional air inlet of comparable heights surround it. This part of the with PM10 separation through an impactor followed Western Ghats is covered with vegetation, grass and by PM2.5 separation WINS impactor. For sampling of trees. The only noticeable local source of pollution is PM10 and PM2.5, glass (Whatman- GF/A) and PTFE wood burning for cooking. A few people live at the filters were used, respectively. The desiccated filter summit and some tourists visit the area by foot. The papers were weighed twice (before and after the vehicular traffic stops at about 1 km distance from the sampling) on the micro-balance (AE 163, Metler) and Fig. 1 — Map showing the sampling site 286 INDIAN J RADIO & SPACE PHYS, AUGUST - OCTOBER 2014 again desiccated for 24 hours. The conditioned and judgment. The filter should be immersed in 3- 4 drops weighed filter papers (PM10 and PM2.5) were placed in of silicon oil at regular intervals as per the need; filter holders and taken to the field for sampling to (iii) Periodic cleaning of the sampler was done to avoid contamination of the filter papers on the way. make the sampler dust free so that the dust on the Before starting the sampling, initial volume and timer sampler may not be counted with the mass readings were noted for PM10 and PM2.5 in field concentration of the sample. monitoring sheet. The pre-weighted and coded filter papers were placed in the filter holder of the 2.4.2 Blank correction respective samplers and screwed properly before Background contamination was monitored by using field blanks (unexposed filter papers), which were starting the samplers. Both the PM10 and PM2.5 samplers were operated for 24 hours sampling period. processed with samples. The field blank filters, Before and after each set of sampling, data were exposed in the field for few seconds, were collected entered in the field data sheet in the pre-defined thrice during the season. Background contamination was eliminated by subtracting the field blank values format and concentrations of PM10 and PM2.5 were calculated gravimetrically. After sampling, filter from concentrations of the samples. Usually, field blank values were very low, typically below or around papers (PM10 and PM2.5) were removed with forceps and placed in the cassette and the cassette was the detection limits. wrapped with aluminum foil to prevent the 2.4.3 Reproducibility test degradation of organic compounds due to Reproducibility test demonstrates the stability of photo-oxidation and brought back to the laboratory. the analytical instruments. Analysis of the same The weighed filter papers were preserved in freezer standard solution was repeated 10 times on IC, AAS for further chemical analysis. and UV-Vis. spectrophotometer. The relative standard deviation was ranged 0.62-5.8% for all analyzed 2.3 Chemical analysis After exposing the filter papers for the required species which indicates about 95% reproducibility of time, papers were extracted for water soluble measured species. components by soxhlet extractor. After extraction, the water soluble extracts of PM were analyzed for major 3 Results and Discussion - 2- - + + + The average chemical composition of PM10, PM2.5 anions and cations (Cl , SO4 , NO3 , NH4 , Na , K , Ca2+ and Mg2+). Ion chromatograph (DX100) was and PM10−2.5 at Sinhagad are given in Table 1. The - 2- - average concentrations of PM10 and PM2.5 at Sinhagad used for the analysis of Cl , SO4 and NO3 . Also, -3 + were found to be 35.8 and 14.1µ gm , respectively. NH4 was analysed by UV-Vis spectrophotometer + The higher PM10 values indicate the impact of marine (Spectronic -20D). Ammonium (NH4 ) reacts with phenol and hypochlorite in the presence of a catalyst source, especially sea salt from Arabian Sea. The day-to-day change in order of magnitude of PM10 and (sodium nitroprusside) to produce a blue coloured -3 PM2.5 concentrations is found to be 7.4 – 58.2 µg m indo-phenol dye (Weatherburn, 1967).