Emissions Characteristics of Hazardous Air Pollutants from the Incineration of Sacriﬁcial Oﬀerings

atmosphere

Article Emissions Characteristics of Hazardous Air Pollutants from the Incineration of Sacriﬁcial Oﬀerings

Shihao Zhang 1,2, Lianhong Zhong 1, Xi Chen 3, Yanan Liu 1,4, Xiaoman Zhai 3, Yifeng Xue 1,*, Wei Wang 3,*, Jie Liu 1,2 and Kangli Xu 1

1 National Engineering Research Center of Urban Environmental Pollution Control, Beijing Municipal Research Institute of Environmental Protection, Beijing 100037, China; [email protected] (S.Z.); [email protected] (L.Z.); [email protected] (Y.L.); [email protected] (J.L.); [email protected] (K.X.) 2 College of Resource Environment and Tourism, Capital Normal University, Beijing 100048, China 3 Key Laboratory of Pollution Control of Ministry of Civil Aﬀairs, 101 Institute of Ministry of Civil Aﬀairs, Beijing 100070, China; [email protected] (X.C.); [email protected] (X.Z.) 4 College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, China * Correspondence: [email protected] (Y.X.); [email protected] (W.W.)

Received: 26 May 2019; Accepted: 14 June 2019; Published: 18 June 2019

Abstract: The incineration of sacrificial offerings generates numerous hazardous air pollutants, including particulate matter (PM), CO, SO2, NOx and non-methane hydrocarbons (NMHC), which has significant effects on the environment and human health. However, due to the concealment of sacrificial offerings incineration, the emission of such pollutants has not received sufficient attention. Relevant quantification of the emission, emission factors and pollution control measures for this pollution source are lacking. To address these problems, herein, we quantified the particulate matter and its chemical composition and the emission levels of gaseous pollutants, including SO2, NOx, NMHC and CO, by performing incineration experiments of four typical sacrificial offerings (Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper), and obtained the emission factors and emission characteristics for the incineration of sacrificial offerings. Therefore, this study lays the foundation and provides support for establishing an emission inventory of the air pollutants from the incineration of sacrificial offerings and introducing corresponding pollution control measures. The results show that the emission concentrations of CO and total suspended particulate (TSP) from the incineration of sacrificial offerings greatly exceed the emission standard, with averages 3 3 of 621.4 mg m− and 142.9 mg m− at 11% oxygen content, respectively. The average emission factors of SO2, NOx, NMHC, CO, PM10 and PM2.5 for the incineration of the four offerings are (0.47 0.17) kg t 1, (2.46 0.35) kg t 1, (5.78 2.41) kg t 1, (32.40 8.80) kg t 1, (4.23 0.71) kg t 1 ± − ± − ± − ± − ± − and (2.62 0.48) kg t 1, respectively, among which the emission intensities of NMHC and CO are ± − relatively high. Among the different types of sacrificial offerings, the overall average emission factor of air pollutants generated from the incineration of Yuanbao paper is the highest, which is mainly due to the low burning efficiency and the coating material. For the chemical composition of the particulate matters, ions, OC, EC and metal elements account for proportions of the PM at (23.55 10.37) %, 2.5 ± (29.74 9.95) %, (14.83 6.55) % and (13.45 4.88) %, respectively, indicating that the organic ± ± ± pollution is severe

Keywords: The incineration of sacrificial offerings; air pollution; emission factor; emission characteristic; chemical composition of particulate matter

Atmosphere 2019, 10, 332; doi:10.3390/atmos10060332 www.mdpi.com/journal/atmosphere Atmosphere 2019, 10, 332 2 of 14

1. Introduction 1. Introduction As a funeral custom, the incineration of sacrificial offerings is prevalent in China (Figure1). As a funeral custom, the incineration of sacrificial offerings is prevalent in China (Figure 1). Because of the large number of deaths, the annual cremations and the quantity of the accompanying Because of the large number of deaths, the annual cremations and the quantity of the accompanying incineration of sacrificial offerings are very large. The incineration of sacrificial offerings (such as incineration of sacrificial offerings are very large. The incineration of sacrificial offerings (such as Joss Joss paper, Funeral wreath, Taoist paper art, Yuanbao paper and cloths) generates large amounts paper, Funeral wreath, Taoist paper art, Yuanbao paper and cloths) generates large amounts of of hazardous air pollutants, including PM, CO, SO2, NOx and NMHC [1–6]. The pollutants that hazardous air pollutants, including PM, CO, SO2, NOx and NMHC [1–6]. The pollutants that are are directly emitted to the atmospheric environment will participate in atmospheric photochemical directly emitted to the atmospheric environment will participate in atmospheric photochemical reactions [7–10]. In addition, the large amounts of organic carbon, elemental carbon, inorganic ions and reactions [7–10]. In addition, the large amounts of organic carbon, elemental carbon, inorganic ions heavy metals in the particulate matter can directly or indirectly influence the solar radiation, thereby and heavy metals in the particulate matter can directly or indirectly influence the solar radiation, altering the radiation balance and photochemical properties of the atmosphere. These changes, in turn, thereby altering the radiation balance and photochemical properties of the atmosphere. These lead to atmospheric haze, severely impacting the environment and human health [11–14]. Since the changes, in turn, lead to atmospheric haze, severely impacting the environment and human health issuing of emission standards of air pollutants for crematories in 2015, certain crematories have set [11–14]. Since the issuing of emission standards of air pollutants for crematories in 2015, certain up special incinerators for sacrificial offerings. However, the unorganized, individual incineration of crematories have set up special incinerators for sacrificial offerings. However, the unorganized, sacrificial offerings is still prevalent. Even in those crematories where special incinerators are set up for individual incineration of sacrificial offerings is still prevalent. Even in those crematories where the incineration of sacrificial offerings, most have not installed flue gas purification systems. As a result, special incinerators are set up for the incineration of sacrificial offerings, most have not installed flue pollutants are directly discharged to the atmosphere without purification, causing severe impacts gas purification systems. As a result, pollutants are directly discharged to the atmosphere without on the environment and human health in the surrounding areas. Although the visible emission and purification, causing severe impacts on the environment and human health in the surrounding areas. pollution are serious, due to custom, the pollution from the incineration of sacrificial offerings is usually Although the visible emission and pollution are serious, due to custom, the pollution from the ignored, and the quantification of the pollution emissions and emission factors and development of incineration of sacrificial offerings is usually ignored, and the quantification of the pollution pollution control measures are lacking. emissions and emission factors and development of pollution control measures are lacking.

Figure 1. Sites of the incinerator for sacrificial sacriﬁcial offerings. oﬀerings.

2 Atmosphere 2019, 10, 332 3 of 14

There have been few studies about the emission characteristics of the incineration of sacrificial offerings in China and abroad. Some researchers studied the emissions from the incineration of Joss paper in Taiwan. For example, Rau et al. [15] sampled and analyzed the flue gas from the open 3 burning of Joss paper. They found that the concentration of particulate matter can reach 76~732 µg m− , and the concentration of gaseous polycyclic aromatic hydrocarbons (PAHs) can reach as high as 3 3 1905.4 ng m− . Lin et al. [16] determined that the total concentration of PAHs can reach 5384 ng m− during the Hungry Ghost Festival in Taiwan, China. Chiu et al. [17] analyzed the polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) from the stack flue gases, fly ashes and bottom ashes. Past research mainly focused on the emissions and concentrations of particulate matters, PAHs and PCDD/Fs from incineration [18–20]; however, investigations of the emission levels and characteristics of other hazardous pollutants (e.g., NMHC) are lacking. Therefore, these studies are insufficient to ascertain the characteristics of the air pollutants from the incineration of sacrificial offerings. To find out the emission characteristics of the pollutants from the incineration of sacrificial offerings, establish a corresponding emission factor database and identify the chemical compositions of the pollution sources, we have chosen four typical sacrificial offerings in this study and carried out experiments for the emission of hazardous air pollutants. By using off-line and online analytical systems, we monitored the changes in the concentrations of gaseous pollutants and analyzed the chemical composition of particulate matter and their concentrations. Based on the experiments, we obtained emission factors for the hazardous air pollutants from the incineration of sacrificial offerings and identified the composition of the pollution sources. The results could provide a reference and support for the identification of pollution sources and pollution management and control.

2. Materials and Methods

2.1. Materials and Equipments Based on the surveys we did in 19 crematoria, four common and typical sacriﬁcial oﬀerings were chosen for the incineration experiments, namely, Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper (Figure2).

FigureFigure 2. 2.Four Four typestypes ofof sacriﬁcialsacrificial offerings oﬀerings used used in in the the experiment. experiment.

These four sacrificial offerings were individually placed in the incinerator for burning. Each sacrificial offering was divided into three parts by mass, and three repeated experiments were performed. Based on a large number of on-site investigations, the incinerator used in this research was the most mainstream incinerator of sacrificial offerings used in the crematorium. The flue gas was collected by the gas-collecting hood and was sucked into the tunnel through the wind-inducing effect from the high-capacity ventilator for sampling and monitoring. The experiment platform was

Figure 3. Pollutant-monitoring platform for the incineration of sacrificial offerings.

2.2. Sample Collection and Analysis The equipment used for the collection and analysis of the hazardous air pollutants from the incineration of sacrificial offerings is listed in Table 1. Before the start of the burning experiments, the quartz membranes (used for organic carbon (OC), element carbon (EC), ions and metal elements analysis) and Teflon membranes (used to calculate the weight of the particulate matters) were pretreated. The quartz membranes were burned at 600 °C for 4 h in a muffle furnace and then equilibrated for 24 h in a chamber at a constant temperature (25 °C) and constant humidity (0%rH). Finally, the membranes were weighed and stored in a membrane box. Similarly, the Teflon membranes were equilibrated for 24 h in a chamber at a constant temperature (25 °C) and constant humidity (0%rH) and weighed. Before starting the experiments, the sacrificial offerings used in the experiment were sorted and weighed, and the equipment was calibrated. In the monitoring and sampling stage, a Laoying3012H Automatic Stack Dust Sampler/Flue Gas Analyzer was first used to measure the velocity, temperature, humidity and pressure of the flue gas. Then, the measured parameters were input into the two-stage virtual impactor to set up the parameters of the sampler, and sampling heads were chosen for the capture of the particulate matter in the flue gas, with diameters in the ranges of 0~2.5 μm, 2.5~10 μm and 10~100 μm. A Thermo online monitoring system was used to record the changes in the gas concentrations every minute. After the experiment, the membranes were loaded into membrane box for cold storage. The concentrations of OC and EC, ions, and metal elements in the particulate matter were determined by using an OC/EC analyzer, ion

Atmosphere 2019, 10, 332 4 of 14 shown in Figure3, including the incinerator, gas-collecting hood, dilution tunnel, particulate matter sampler, ﬂue gas parameter tester, online monitoring instrument for atmospheric pollutants, ﬁltration equipment and ventilator.Figure 2. Four types of sacrificial offerings used in the experiment.

FigureFigure 3. 3.Pollutant-monitoring Pollutant-monitoring platformplatform for the incineration incineration of of sacrificial sacriﬁcial offerings. oﬀerings.

2.2.2.2. Sample Sample Collection Collection and and Analysis Analysis TheThe equipment equipment used used for for the the collectioncollection andand analysisanalysis of of the the hazardous hazardous air air pollutants pollutants from from the the incinerationincineration of of sacrificial sacrificial oofferingsfferings is listed listed in in Table Table 1.1 Before. Before the the start start of the of burning the burning experiments, experiments, the thequartz quartz membranes membranes (used (used for for organic organic carbon carbon (OC), (OC), element element carbon carbon (EC), (EC), ions ions and and metal metal elements elements analysis)analysis) and and Teflon Teflon membranes membranes (used (used to calculate to calculate the weight the weight of the particulateof the particulate matters) matters) were pretreated. were Thepretreated. quartz membranes The quartz were membranes burned at were 600 ◦ burnedC for 4 hat in 600 a mu °Cffl fore furnace 4 h in anda muffle then equilibratedfurnace and forthen 24 h in aequilibrated chamber at for a constant24 h in a temperaturechamber at a (25 constant◦C) and temperature constant humidity (25 °C) and (0%rH). constant Finally, humidity the membranes (0%rH). wereFinally, weighed the andmembranes stored in were a membrane weighed box. andSimilarly, stored in the a Teflonmembrane membranes box. Similarly, were equilibrated the Teflon for 24membranes h in a chamber were at aequilibrated constant temperature for 24 h in a (25 chamber◦C) and at constant a constant humidity temperature (0%rH) (25 and °C) weighed. and constant Before startinghumidity the (0%rH) experiments, and weighed. the sacrificial Before ostartingfferings the used experiments, in the experiment the sacrificial were offerings sorted andused weighed, in the andexperiment the equipment were wassorted calibrated. and weighed, In the and monitoring the equipment and sampling was calibrated. stage, a Laoying3012H In the monitoring Automatic and Stacksampling Dust Sampler stage, a /Laoying3012HFlue Gas Analyzer Automatic was first Stack used Dust to Sampler/Flue measure the Gas velocity, Analyzer temperature, was first used humidity to andmeasure pressure the of velocity, the flue gas.temperature, Then, the humidity measured and parameters pressure of were the inputflue gas. into Then, the two-stage the measured virtual parameters were input into the two-stage virtual impactor to set up the parameters of the sampler, impactor to set up the parameters of the sampler, and sampling heads were chosen for the capture of the and sampling heads were chosen for the capture of the particulate matter in the flue gas, with particulate matter in the flue gas, with diameters in the ranges of 0~2.5 µm, 2.5~10 µm and 10~100 µm. diameters in the ranges of 0~2.5 μm, 2.5~10 μm and 10~100 μm. A Thermo online monitoring system A Thermo online monitoring system was used to record the changes in the gas concentrations every was used to record the changes in the gas concentrations every minute. After the experiment, the minute. After the experiment, the membranes were loaded into membrane box for cold storage. membranes were loaded into membrane box for cold storage. The concentrations of OC and EC, ions, Theand concentrations metal elements of OCin the and particulate EC, ions, and matter metal we elementsre determined in the by particulate using an matter OC/EC were analyzer, determined ion by using an OC/EC analyzer, ion chromatograph and Inductively coupled plasma mass spectrometry (ICP-MS), respectively. In order to compare with the4 national standard (GB 13801-2015) [21] (Table2) in which the values are specified in the case of 11% oxygen content, the measured concentrations should be converted into 11% oxygen content.

Table 1. Equipment used for sample collection and analysis.

Item for Monitoring and Analysis Equipment Flue gas parameters (temperature, humidity, oxygen content) Laoying3012H Automatic Stack Dust Sampler/Flue Gas Analyzer Particulate matter Two-stage virtual impactor NOx Thermo 42i NOx online analyzer SO2 Thermo 43i SO2 online analyzer CO Thermo 48i CO online analyzer Thermo 51i THC online analyzer NMHC Thermo 55i CH4 online analyzer OC and EC in PM2.5 OC/EC analyzer (DRI model 2015, Atmoslytic Inc, USA) Ions in PM2.5 Ion chromatograph (IC, Dionex 600 and ICs 2100, USA) Elements in PM2.5 ICP-MS (7700x) Atmosphere 2019, 10, 332 5 of 14

3 Table 2. Emission standard of air pollutants for crematory (GB 13801-2015) Unit: mg m− (except PCDD/Fs and Flue gas blackness)

Control Item Emission Limit TSP 80 SO2 60 NOX 300 CO 300 3 PCDD/Fs(ng-TEQ m− ) 0.5 Flue gas blackness(Ringelmann blackness) 1

2.3. Calculation of Emission Factors Based on the data recorded on the gaseous pollutant online monitor, the experimental setup and the corresponding flue gas data, the equation for the calculation of the emission factors for the gaseous pollutants is shown below: 2 Cij π r v t EF = × × × × , (1) ij 1000 m × i where EFij represents the emission factor of the type j gaseous pollutant from the type i sacrificial 1 offering, with a unit of g kg− ;Cij represents the average monitoring concentration of the type j gaseous 3 pollutant from the type i sacrificial offering, with a unit of mg m− ; r is the radius of the tunnel, 1 with a unit of m; v is the velocity of the flue gas in the tunnel, with a unit of m s− ; t is the sampling time, with a unit of s; and mi represents the weight of the type i sacrificial offering, with a unit of kg. The calculation of the emission factors for the particulate matter is shown in the following equation:

M 1000 Cip = × , (2) Qp t × 2 Cip π r v t 60 EFip = × × × × × , (3) mi where Cip represents the concentration of particulate matter with a diameter of p from the type i 3 sacrificial offering, with a unit of g m− ; M is the mass increase of the membrane, with a unit of g; Qp denotes the collection flow of particulate matter with a diameter of p by the sampler, with a unit of 1 L min− ; t is the sampling time, with a unit of min; EFip represents the emission factor of the particulate 1 matter with a diameter of p from the type i sacrificial offering, with a unit of g kg− ; r is the radius 1 of the tunnel, with a unit of m; v is the velocity of the flue gas in the tunnel, with a unit of m s− ; mi represents the weight of the type i sacrificial offering, with a unit of kg.

3. Results and Discussion

3.1. Emission Concentration Levels of Hazardous Air Pollutants Figures4 and5 show the variations of emission concentration and the average concentrations of the gaseous pollutants from the incineration of Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper. It can be seen from Figure4 that the changes of the pollutants (SO 2, NOx, NMHC, CO) emitted from the incineration of the four sacrificial offerings were similar. In the initial stage, the pollutant concentration increased rapidly, but as the temperature gradually increased, the burning efficiency increased and the pollutant concentration decreased slightly. Among the gaseous pollutants, 3 CO has the highest emission concentration, which can reach as high as 143.52 mg m− , indicating that the sacrificial offerings cannot be completely burned in the incineration process. This is followed by NMHC and NOx. Because these offerings contain low contents of S, the concentrations of SO2 generated from the burning are the lowest and show the smoothest changes. Atmosphere 2019, 10, 332 6 of 14

It can be found from a comparison of the average concentrations of the atmospheric pollutants from the incineration of sacrificial offerings (Figure5) that the average concentration of CO is the 3 highest, at 62.14 mg m− . If the measured concentration is converted into 11% oxygen content, it will be 3 621.4 mg m− , 3.1 times the national emission standard (GB 13801-2015) [21]. The average concentrations 3 3 3 of TSP, PM10 and PM2.5 are 14.29 mg m− , 7.06 mg m− and 4.34 mg m− , respectively. If converted into 3 3 3 11% oxygen content, they will be 142.9 mg m− , 70.6 mg m− and 43.4 mg m− , respectively. Among those, the TSP concentration is 1.8 times the national emission standard. The average concentrations of 3 3 NOx and SO2 are 5.01 mg m− and 0.85 mg m− , respectively. Next to CO, the emission concentration of 3 NMHC is the highest, reaching 10.64 mg m− . These organic compounds may be the most important source of the "odor" in crematories [22–25]. However, in the relevant emission standards for pollutants from the incineration of sacrificial offerings, the emission concentration of NMHC is not regulated. Therefore, we recommend that emission standards should include indexes for these pollutants and urge the pollutant-producing parties to install activated carbon injection device to reduce the emissions.

Figure 4. Emission concentration variations of the gaseous pollutants from the incineration of the four Figure 4. Emission concentration variations of the gaseous pollutants from the incineration of the four sacriﬁcial oﬀerings: (a) Joss paper; (b) Funeral wreath; (c) Taoist paper art; (d) Yuanbao paper. sacrificial offerings: (a) Joss paper; (b) Funeral wreath; (c) Taoist paper art; (d) Yuanbao paper.

Figure 5. Average emission concentrations of pollutants from the incineration of the four sacrificial offerings.

3.2. Emission factors of Hazardous Air Pollutants Based on the calculation methods in section 2.3, the overall average emission factors of the six pollutants of the incineration of the four typical sacrificial offerings (Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper) are 7.53 kg t−1, 6.10 kg t−1, 7.01 kg t−1 and 11.33 kg t−1, respectively. Among those, the emission intensity of the atmospheric pollutants from the Yuanbao paper is the greatest, which is mainly due to its unique coating material. Furthermore, because of the coating, Yuanbao paper becomes much more non-flammable. The emission factors of SO2, NOx, NMHC, CO, PM10 and PM2.5 from the incineration of the four sacrificial offerings are shown in Figure 6, and their average values are (0.47 ± 0.17) kg t−1, (2.46 ± 0.35) kg t−1, (5.78 ± 2.41) kg t−1, (32.40 ± 8.80) kg t−1, (4.23 ± 0.71) kg t−1 and (2.62 ± 0.48) kg t−1, respectively. Among them, the emission factor of CO is the 7

AtmosphereFigure2019 4., Emission10, 332 concentration variations of the gaseous pollutants from the incineration of the four7 of 14 sacrificial offerings: (a) Joss paper; (b) Funeral wreath; (c) Taoist paper art; (d) Yuanbao paper.

FigureFigure 5. Average 5. Average emission emission concentrations concentrations of pollutants of pollutants from from the incineration the incineration of the of four the sacriﬁcial four sacrificial oﬀerings.

offerings. 3.2. Emission factors of Hazardous Air Pollutants greatest; this is mainly due to the insufficient burning of the sacrificial offerings, which results in a 3.2. EmissionBased on factors the calculation of Hazardous methods Air Pollutants in Section 2.3, the overall average emission factors of the six large emission of CO. Among the different sacrificial offerings, the emission factor of CO from pollutants of the incineration of the four typical sacrificial offerings (Joss paper, Funeral wreath, Taoist YuanbaoBased paper on the is greatercalculation than methodsthat from in Joss section paper, 2.3, Funeral the overall wreath average and Taoist emission paper factors art, 47.34 of the kg sixt−1, paper art and Yuanbao paper) are 7.53 kg t 1, 6.10 kg t 1, 7.01 kg t 1 and 11.33 kg t 1, respectively. indicatingpollutants thatof the the incineration burning efficiency of the offour the typical− Yuanba sacrificialo paper− is offerings lower− than (Joss that paper, of the Funeral −other offerings. wreath, Among those, the emission intensity of the atmospheric−1 pollutants−1 from−1 the Yuanbao−1 paper is the TheTaoist emission paper art factors and Yuanbao of PM10 and paper) PM are2.5 from 7.53 Yuanbaokg t , 6.10 paper kg t ,are 7.01 also kg thet and greatest, 11.33 kg5.42 t kg, respectively. t−1 and 3.44 greatest, which is mainly due to its unique coating material. Furthermore, because of the coating, kgAmong t−1, respectively. those, the emission intensity of the atmospheric pollutants from the Yuanbao paper is the Yuanbaogreatest, paperwhich becomesis mainly much due moreto its non-flammable.unique coating material. The emission Furthermore, factors of SObecause2, NO xof, NMHC,the coating, CO, PM and PM from the incineration of the four sacrificial offerings are shown in Figure6, and their Yuanbao10In past paper studies,2.5 becomes very much little more attention non-fl wasammable. paid toThe the emission emission factors of organic of SO2 , compoundsNOx, NMHC, in CO,the averageincineration values of sacrificial are (0.47 offerings.0.17) kg However, t 1, (2.46 the0.35) measurement kg t 1, (5.78 results2.41) show kg t that1, (32.40 the emission8.80) kgfactor t 1, PM10 and PM2.5 from the incineration− of the four sacrificial− offerings are shown− in Figure 6, and their− 1 ± 1 ± ± ± (4.23of NMHC0.71) is kg greater t and than (2.62 that0.48) of SO−1 kg2, tNO, respectively.x, PM10 or− 1 PM Among2.5. The them, emission the−1 emission factor of factor NMHC of−1 COfrom is average± values are− (0.47 ± 0.17)± kg t , (2.46− ± 0.35) kg t , (5.78 ± 2.41) kg t , (32.40 ± 8.80) kg t , (4.23 −1 theYuanbao± 0.71) greatest; kg paper t−1 thisand is is the(2.62 mainly greatest, ± 0.48) due 9.44 kg to thetkg−1, t insurespectively.. Thisfficient finding burning Among is likely of them, therelated sacrificial the to emission the ouniquefferings, factor coating which of CO material results is the inof aYuanbao large emission paper. Therefore, of CO. Among to decrease the diff theerent emissi sacrificialon of NMHC offerings, from the the emission incineration factor of of sacrificial CO from 7 1 Yuanbaoofferings, paper materials is greater with low than amount that from of Jossorganic paper, matters Funeral should wreath be chosen and Taoist and paperthe coating art, 47.34 should kg t −be, indicatingreduced. In that addition, the burning more eattentionfficiency should of the Yuanbaobe paid to paper the emission is lower thanof volatile that of organic the other compounds offerings. 1 Thefrom emission the incineration factors of sacrificial PM10 and offerings, PM2.5 from which Yuanbao should paper be added are also to emission the greatest, standards 5.42 kgto provide t− and 1 3.44guidance kg t− for, respectively. the control of pollution sources.

Figure 6. EmissionEmission factors of hazardous ai airr pollutants from the incinerationincineration of sacriﬁcialsacrificial oofferings.ﬀerings.

3.3. ComparisonIn past studies, to the Emissions very little of attention Other Burning was paidSources to the emission of organic compounds in the incineration of sacrificial offerings. However, the measurement results show that the emission factor of The emissions of hazardous air pollutants from the incineration of sacrificial offerings are NMHC is greater than that of SO2, NOx, PM10 or PM2.5. The emission factor of NMHC from Yuanbao compared to that from similar1 burning sources such as cremators and the burning of straw, as shown paper is the greatest, 9.44 kg t− . This finding is likely related to the unique coating material of Yuanbao paper.in Table Therefore, 3. It can be to seen decrease that compared the emission to the of NMHChazardous from air the pollutants incineration not treated of sacrificial with a o ffflueerings, gas materialspurification with system low amountfrom cremator of organics (Cremator matters B), should the emissions be chosen of and the the hazardous coating shouldair pollutants be reduced. from the incineration of sacrificial offerings are less intense. This finding is mainly because the cremation process requires fuel. In addition, the pollutants generated from the burning of the organic compounds in corpses result in a greater initial emission intensity. The emission intensity of pollutants from cremators after flue gas purification system (Cremator A) is greatly reduced and is significantly lower than the air pollutant emissions from the incineration of sacrificial offerings. The average emission factors of PM10 and PM2.5 generated from the incineration of sacrificial offerings are 24 and 48 times the emission intensity of pollutants from cremators treated with flue gas purification system. These results explain the significance of flue gas purification system in the control of pollutant emissions. Therefore, since the emission standards of air pollutants for crematories were issued and implemented in 2015, the control of pollution from cremators has been achieved. The installation rate of flue gas purification system for cremators increased gradually. However, the most incinerators of sacrificial offerings are not controlled. According to the statistical bulletin of Ministry of Civil Affairs, the amount of cremation reaches 4.82 million in 2017. The amount of incineration of sacrificial offerings in 2017 can reach about 144600 tons. Thus, it is the relative contribution from the

8 Atmosphere 2019, 10, 332 8 of 14

In addition, more attention should be paid to the emission of volatile organic compounds from the incineration of sacriﬁcial oﬀerings, which should be added to emission standards to provide guidance for the control of pollution sources.

3.3. Comparison to the Emissions of Other Burning Sources The emissions of hazardous air pollutants from the incineration of sacrificial offerings are compared to that from similar burning sources such as cremators and the burning of straw, as shown in Table3. It can be seen that compared to the hazardous air pollutants not treated with a flue gas purification system from cremators (Cremator B), the emissions of the hazardous air pollutants from the incineration of sacrificial offerings are less intense. This finding is mainly because the cremation process requires fuel. In addition, the pollutants generated from the burning of the organic compounds in corpses result in a greater initial emission intensity. The emission intensity of pollutants from cremators after flue gas purification system (Cremator A) is greatly reduced and is significantly lower than the air pollutant emissions from the incineration of sacrificial offerings. The average emission factors of PM10 and PM2.5 generated from the incineration of sacrificial offerings are 24 and 48 times the emission intensity of pollutants from cremators treated with flue gas purification system. These results explain the significance of flue gas purification system in the control of pollutant emissions. Therefore, since the emission standards of air pollutants for crematories were issued and implemented in 2015, the control of pollution from cremators has been achieved. The installation rate of flue gas purification system for cremators increased gradually. However, the most incinerators of sacrificial offerings are not controlled. According to the statistical bulletin of Ministry of Civil Affairs, the amount of cremation reaches 4.82 million in 2017. The amount of incineration of sacrificial offerings in 2017 can reach about 144,600 tons. Thus, it is the relative contribution from the incineration of sacrificial offerings which will increase when more and more cremators have flue gas purification installed.

Table 3. Emission factors of air pollutants from the incineration of four types of sacriﬁcial oﬀerings and 1. relevant sources Unit: kg t−

Type SO2 NOx CO PM10 PM2.5 Source Incineration of Joss paper 0.02–0.04 1.63–2.16 22.97–45.43 // [26] Cremator A 0.53 12.56 3.28 0.19 0.06 [27] Cremator B 1.41 10.03 18.19 9.97 8.80 [27] Incineration of straw 0.53 1.42 27.7 5.78 5.67 [28] Incineration of wheat 0.85 3.3 60 10.86 7.6 [29] Incineration of cotton 0.002 2.68 68.34 6.93 5.76 [30] Incineration of waste paper //// 2.72 [31] This study 0.22–0.64 1.92–2.84 24.66–47.34 3.66–5.42 2.31–3.44 Note: / means relevant data are unavailable.

Compared to the open burning of straw, the emission levels of hazardous air pollutants are similar. The emission intensity of NOx from the incineration of sacrificial offerings is slightly higher. However, the emission factors of particulate matters are relatively low. The emission factors of CO and particulate matters from incineration of wheat and cotton are much higher than sacrificial offerings. However, the burning of straw is mostly seasonal or short-term, whereas the incineration of sacrificial offerings is more common and regular, thus resulting in a greater atmospheric environmental hazard. Zhou et al. [26] performed similar studies in Taiwan. They estimated the emission factors of SO2, NOx, CO and particulate matter from the burning of Joss paper by carrying out burning experiments and found that the emission factors of NOx and CO are close to the emission factors of four types of sacrificial offerings in this study. However, the emission intensity of SO2 was smaller in their study; this is related to the low S content in the materials of sacrificial offerings in Taiwan. The emission factor of PM2.5 from the incineration of domestic waste paper falls within the range of this study. In this study, based on more types of Atmosphere 2019, 10, 332 9 of 14

sacrificial offerings, we obtained the emissions of several hazardous air pollutants including the emission characteristics of NMHC and particulate matter and their chemical compositions.

3.4. Chemical Compositions of Particulate Matter

As PM2.5 is more likely to be breathed in, a chemical composition analysis of PM2.5 was done in this research. The percentages of the chemical components in PM2.5 generated from the burning of Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper are shown in Figure7. The average percentages of ions, OC, EC and metal elements are (23.55 10.37)%, (29.74 9.95)%, (14.83 6.55)% ± ± ± and (13.45 4.88)%, respectively. Among those, the percentage of OC is the highest, thus indicating ± that the organic pollution is severe. This finding is particularly true for the incineration of Taoist paper art, which has a percentage of OC as high as 40.56%. This is related to presence of coating and a small amount of plastic protection film on the surface. The ion percentage is also high. The ion percentage from the incineration of Yuanbao paper is the highest, accounting for 26.77% of the chemical components in PM2.5. The components that have the lowest percentage are the metal elements. Even so, the elemental content in Funeral wreath is as high as 24.39%. This is likely due to the use of metal the usewires of in metal the production wires in ofthe the production wreath. Therefore, of the materialswreath. usedTherefore, in the sacrificialmaterials off usederings in have the a sacrificial great offeringsinfluence have on a thegreat composition influence of on particulate the composition matters. of particulate matters.

FigureFigure 7. Percentages 7. Percentages of ofchemical chemical components components in PMPM2.52.5 generatedgenerated from from the the incineration incineration of sacriﬁcial of sacrificial offerings:oﬀerings: (a) Joss (a) Joss paper; paper; (b) ( bFuneral) Funeral wreath; wreath; ( (cc) Taoist paper paper art; art; (d (d)) Yuanbao Yuanbao paper. paper. 3.4.1. OC and EC Components in Particulate Matter 3.4.1. OC and EC Components in Particulate Matter The concentrations of EC and OC in PM2.5 generated from the incineration of sacrificial offerings wereThe concentrations monitored and analyzedof EC and using OC anin PM OC/2.5EC generated analyzer (asfrom shown the incineration in Figure8). Theof sacrificial average mass offerings 3 wereconcentrations monitored and of OCanalyzed and EC using in PM 2.5anfrom OC/EC four analyzer types of sacrificial(as shown offerings in Figure were 8). 1.35 The mg average m− and mass 3 −3 concentrations0.65 mg m− of, respectively, OC and EC accounting in PM2.5 for from 31.0% four and types 15.1% of of thesacrificial PM2.5, on offerings average. Thewere concentration 1.35 mg m of and 0.65 OCmg ism much−3, respectively, higher than accounting that of EC, particularly for 31.0% in and the 15.1% incineration of the of PM Taoist2.5, on paper average. art. The The concentration concentration 3 of OCof OCis much can be ashigher high as than 2.50 mgthat m −of, 2.4EC, times particularly that of EC, in which the isincineration mainly because of ofTaoist the surface paper coating art. The concentrationand plastic of protection OC can film.be as The high results as 2.50 show mg that m the−3, 2.4 organic times pollution that of isEC, severe which in theis mainly incineration because of of the surfacesacrificial coating offerings. and The plastic average protection mass concentrations film. The results of OC show and EC that in thethe PM organic2.5 of the pollution surrounding is severe in the incineration of sacrificial offerings. The average mass concentrations of OC and EC in the PM2.5 of the surrounding atmosphere are 0.89~6.87 μg m−3 (with an average of 3.88 μg m−3) and 0.10~1.74 μg m−3 (with an average of 0.92 μg m−3), respectively, and the average concentrations in the flue gas from the incineration of sacrificial offerings are 348 and 707 times the above values. Thus, the direct emission of flue gas generated from the incineration of sacrificial offerings to the air will have a great impact on the surrounding air and environment.

The OC/EC ratio in PM2.5 can be used to determine the presence of secondary pollution: if OC/EC > 2, secondary organic carbon is present; if OC/EC < 2, the secondary organic carbon can be ignored [32]. Based on the measurement results, the OC/EC ratio in the PM2.5 generated from the incineration of sacrificial offerings is 2.1, indicating that secondary organic carbon is present in the flue gas and can contribute to air pollution by secondarily formed aerosol. Based on the chemical characteristics of the PM2.5 from the incineration of sacrificial offerings, it is necessary to reinforce the control and emission reduction measures for particulate matter generated from the incineration of sacrificial offerings and install high-efficiency dust removal equipment.

1 Atmosphere 2019, 10, 332 10 of 14

3 3 3 atmosphere are 0.89~6.87 µg m− (with an average of 3.88 µg m− ) and 0.10~1.74 µg m− (with an average 3 of 0.92 µg m− ), respectively, and the average concentrations in the flue gas from the incineration of sacrificial offerings are 348 and 707 times the above values. Thus, the direct emission of flue gas generated from the incineration of sacrificial offerings to the air will have a great impact on the surrounding air and environment.

Figure 8. Concentrations of EC and OC in PM2.5 generated from the incineration of sacriﬁcial oﬀerings. Figure 8. Concentrations of EC and OC in PM2.5 generated from the incineration of sacrificial offerings. The OC/EC ratio in PM2.5 can be used to determine the presence of secondary pollution: if OC/EC > 2, 3.4.2. Water-Solublesecondary organic Inorganic carbon isIons present; in Particulate if OC/EC < 2, Matter the secondary organic carbon can be ignored [32]. Based on the measurement results, the OC/EC ratio in the PM2.5 generated from the incineration of Thesacrificial water-soluble offerings inorganic is 2.1, indicating ions that in secondarythe PM2.5 organic generated carbon isfrom present the in incineration the flue gas and of can sacrificial offeringscontribute were analyzed. to air pollution The byconcentration secondarily formed of each aerosol. type Based of inorganic on the chemical ion characteristicsand its percentage of the in the total concentrationPM2.5 from the of incineration inorganic of ions sacrificial are shown offerings, in it Figure is necessary 9. Cl to- reinforcehas the thehighest control concentration and emission in the reduction measures for particulate matter generated from the incineration of sacrificial offerings and −3 + −3 particulateinstall matter, high-efficiency at 1.40 dustmg removalm , followed equipment. by Na , which has a concentration of 0.62 mg m . The high concentrations of Cl- are mainly attributed to the plastic protection film on the surface. Cl− accounts3.4.2. for Water-Soluble43.7%, 34.4%, Inorganic 32.8%, Ions and in 30.1% Particulate of th Mattere total concentrations of water-soluble inorganic + ions in Joss paper,The water-soluble Funeral wreath, inorganic ionsTaoist in the paper PM2.5 artgenerated and Yuanbao from the incineration paper, and of sacrificialNa accounts offerings for 13.9%, 23.5%, 11.6%were analyzed. and 17.5%, The concentration respectively. of each Amon type ofg inorganicthe eight ion water-soluble and its percentage inorganic in the total concentrationions, Cl-, Na+, Ca2+, of inorganic ions are shown in Figure9. Cl − has the highest concentration in the particulate matter, NH4+ and SO42− are significantly higher than K+, Mg2+, NO3−, and they account for 89.0% of the total at 1.40 mg m 3, followed by Na+, which has a concentration of 0.62 mg m 3. The high concentrations of inorganic ions. − − Cl− are mainly attributed to the plastic protection film on the surface. Cl− accounts for 43.7%, 34.4%, 32.8%, and 30.1% of the total concentrations of water-soluble inorganic ions in Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper, and Na+ accounts for 13.9%, 23.5%, 11.6% and 17.5%, respectively. + 2+ + 2 Among the eight water-soluble inorganic ions, Cl−, Na , Ca , NH4 and SO4 − are significantly higher + 2+ than K , Mg , NO3−, and they account for 89.0% of the total inorganic ions.

Figure 9. Concentrations and percentages of water-soluble ions in PM2.5 generated from the incineration of sacrificial offerings.

3.4.3. Concentrations of Elements in Particulate Matter

The 27 elements detected in the PM2.5 generated from the incineration of sacrificial offerings were analyzed. The 10 elements that have the highest concentrations are Na, Mg, Al, K, Ca, Fe, Cu, Zn, Mo and Ba. Their mass concentrations are shown in Figure 10. Al, K, Na, Fe, Mg and Ca account for 92.8% of the total elements. Among those, the concentration of Al is the highest, accounting for 26.7%, 35.8%, 31.9% and 32.4%, respectively, of the elements in Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper. This finding is related to the composition of the raw materials in the sacrificial offerings. The concentrations of certain metals in the particulate matter generated from the burning

Figure 8. Concentrations of EC and OC in PM2.5 generated from the incineration of sacrificial offerings.

3.4.2. Water-Soluble Inorganic Ions in Particulate Matter

The water-soluble inorganic ions in the PM2.5 generated from the incineration of sacrificial offerings were analyzed. The concentration of each type of inorganic ion and its percentage in the total concentration of inorganic ions are shown in Figure 9. Cl- has the highest concentration in the particulate matter, at 1.40 mg m−3, followed by Na+, which has a concentration of 0.62 mg m−3. The high concentrations of Cl- are mainly attributed to the plastic protection film on the surface. Cl− accounts for 43.7%, 34.4%, 32.8%, and 30.1% of the total concentrations of water-soluble inorganic ions in Joss paper, Funeral wreath, Taoist paper art and Yuanbao paper, and Na+ accounts for 13.9%, 23.5%, 11.6% and 17.5%, respectively. Among the eight water-soluble inorganic ions, Cl-, Na+, Ca2+, + 2− + 2+ − AtmosphereNH4 and2019 SO,410 ,are 332 significantly higher than K , Mg , NO3 , and they account for 89.0% of the11 total of 14 inorganic ions.

Figure 9.9.Concentrations Concentrations and and percentages percentages of water-soluble of water-soluble ions in PMions2.5 generatedin PM2.5 generated from the incineration from the ofincineration sacriﬁcial oofﬀ erings.sacrificial offerings.

3.4.3. Concentrations of Elements in Particulate Matter The 27 elements detected in the PM generated from the incineration of sacrificial offerings were The 27 elements detected in the PM2.5 generated from the incineration of sacrificial offerings were analyzed. The The 10 10 elements elements that that have have the the highest highest co concentrationsncentrations are are Na, Na, Mg, Mg, Al, Al,K, Ca, K, Ca,Fe, Cu, Fe, Cu,Zn, Mo Zn, Moand andBa. Their Ba. Their mass mass concentrations concentrations are shown are shown in Figure in Figure 10. Al, 10 K,. Al, Na, K, Fe, Na, Mg Fe, and Mg Ca and account Ca account for 92.8% for 92.8%of the total of the elements. total elements. Among Among those, the those, concentration the concentration of Al is ofthe Al highest, is the highest, accounting accounting for 26.7%, for 35.8%, 26.7%, 35.8%,31.9% and 31.9% 32.4%, and 32.4%,respectively, respectively, of the ofelements the elements in Joss in paper, Joss paper, Funeral Funeral wreath, wreath, Taoist Taoist paper paper art and art andYuanbao Yuanbao paper. paper. This This finding finding is related is related to tothe the composition composition of of the the raw raw materials materials in in the sacrificialsacrificial oofferings.fferings. The concentrations of certain metals in the particulate matter generated from the burning of Funeral wreath are much higher than than those those from from Joss Joss paper, paper, Taoist Taoist paper paper art art and and Yuanbao Yuanbao paper. paper. 3 For example, the concentration ofof AlAl can be as high1 as 338.07 µμg m−3, ,3.3 3.3 times times that that in in Yuanbao Yuanbao paper, paper, 3 and the concentration of K isis asas highhigh asas 214.03214.03 µμgg mm−−3, 7.0 times that in YuanbaoYuanbao paper.paper. TheThe highhigh concentrations ofof certaincertain metals metals in in Funeral Funeral wreath wreath is is likely likely due due to to the the use use of metalof metal wires. wires. Al, Al, K, Na,K, Na, Fe, MgFe, Mg and and Ca areCa are the the six elementssix elements that that contribute contribute most mo tost the to the incineration incineration of sacrificial of sacrificial offerings, offerings, and and the analysisthe analysis provides provides a basis a basis to the to sourcethe source apportionment. apportionment.

Figure 10.10.Concentrations Concentrations of of elements elements in the in PMthe2.5 PMgenerated2.5 generated from thefrom incineration the incineration of sacrificial of sacrificial offerings. offerings. 4. Conclusions 4. ConclusionsIn order to better understand emission characteristics of hazardous air pollutants from the incinerationIn order of to sacrificial better understand offerings, emission we conducted characte incinerationristics of hazardous experiments air forpollutants typical sacrificialfrom the oincinerationfferings and of obtained sacrificial the offerings, emission levelswe conducted and emission incineration factors ofexperiments hazardous airfor pollutants,typical sacrificial which canofferings provided and supportobtained for the management emission levels of pollution and em preventionission factors and of control. hazardous The air main pollutants, conclusions which are ascan follows: provided support for management of pollution prevention and control. The main conclusions are as follows:

(1) Flue gas generated from the incineration of sacrificial offerings has a considerable impact on the surrounding environment. The emission concentrations of CO and TSP seriously exceed the national emission standard. Furthermore, the emission of NMHC is the most important source of the odor in crematories, and if people are exposed to the environment for a long time, their health will be threatened. Emission standards should include indexes for these pollutants and urge the pollutant- producing parties to install activated carbon injection device to reduce the emissions.

(2) Among the four different sacrificial offerings, the average emission factor of Yuanbao paper is the greatest, which is mainly due to the unique coating material. Because of the coating, Yuanbao paper becomes much more non-flammable and the emission intensity of NMHC is largest. To decrease the emission of NMHC from the incineration of sacrificial offerings, materials with low amount of organic matters should be chosen and the coating should be reduced. As for different pollutants, the emission intensity of CO is the highest, which is mainly due to the insufficient burning. By comparison, it was found that the emission factors of sacrificial offerings are significantly higher than the emission factors of cremators equipped with the flue gas purification systems, and are equivalent to the open burning of straw. The environmental pollution from the incineration of sacrificial offerings cannot be ignored.

(3) In addition, the chemical composition of the PM2.5 generated from the incineration of sacrificial offerings was analyzed for the first time in this study. The average percentages of ions, OC, EC and metal elements are (23.55 ± 10.37) %, (29.74 ± 9.95) %, (14.83 ± 6.55) % and (13.45 ± 4.88) %, respectively. Materials used in the sacrificial offering have a great influence on the composition of

1 Atmosphere 2019, 10, 332 12 of 14

(1) Flue gas generated from the incineration of sacrificial offerings has a considerable impact on the surrounding environment. The emission concentrations of CO and TSP seriously exceed the national emission standard. Furthermore, the emission of NMHC is the most important source of the odor in crematories, and if people are exposed to the environment for a long time, their health will be threatened. Emission standards should include indexes for these pollutants and urge the pollutant-producing parties to install activated carbon injection device to reduce the emissions. (2) Among the four different sacrificial offerings, the average emission factor of Yuanbao paper is the greatest, which is mainly due to the unique coating material. Because of the coating, Yuanbao paper becomes much more non-flammable and the emission intensity of NMHC is largest. To decrease the emission of NMHC from the incineration of sacrificial offerings, materials with low amount of organic matters should be chosen and the coating should be reduced. As for different pollutants, the emission intensity of CO is the highest, which is mainly due to the insufficient burning. By comparison, it was found that the emission factors of sacrificial offerings are significantly higher than the emission factors of cremators equipped with the flue gas purification systems, and are equivalent to the open burning of straw. The environmental pollution from the incineration of sacrificial offerings cannot be ignored. (3) In addition, the chemical composition of the PM2.5 generated from the incineration of sacrificial offerings was analyzed for the first time in this study. The average percentages of ions, OC, EC and metal elements are (23.55 10.37) %, (29.74 9.95) %, (14.83 6.55) % and (13.45 4.88) %, respectively. ± ± ± ± Materials used in the sacrificial offering have a great influence on the composition of particulate matters. The chemical composition analysis of the particulate matter provides guidance and support for source apportionment. (4) It is a quite common phenomenon that the flue gas from incineration of sacrificial offerings is directly emitted into the atmosphere without purification. Based on the findings, crematoria should control the amount of incineration of sacrificial offerings. Types of sacrificial offerings with the characteristic of flammable and low amount of hazardous materials should be chosen. In order to reduce the emissions, the government should formulate corresponding documents to supervise the crematoria to install flue gas purification systems.

Author Contributions: Conceptualization, Y.X. and W.W.; methodology, S.Z., Y.L. and J.L.; formal analysis, S.Z., X.C. and X.Z.; investigation, S.Z., J.L. and K.X.; data curation, Y.X. and L.Z.; writing—original draft preparation, S.Z.; writing—review and editing, Y.X. and W.W. Funding: This work was funded by the National Natural Science Foundation of China (21806012), the National Key Research and Development Program of China (2016YFC0201106), the Science Foundation of Beijing Municipal Research Institute of Environmental Protection (2017B01), and the Beijing Excellent Personnel Training Project (2017000021733G105). Conﬂicts of Interest: The authors declare no conﬂict of interest.

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