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The estimated atmospheric lead emissions in China, 1990–2009
Atmospheric Environment 60 (2012) 1e8
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Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv
The estimated atmospheric lead emissions in China, 1990e2009 Qian Li a, Hongguang Cheng a, *, Tan Zhou a, Chunye Lin a, Shu Guo b a b
School of Environment, Beijing Normal University, Beijing 100875, China South China Institute of Environmental Sciences, MEP, Guangzhou 510655, China
h i g h l i g h t s < We provide an inventory of lead emissions from anthropogenic activities in China. < We provide an analysis of the temporal and spatial variations of lead emissions. < The emission structure of lead changed in the last 20 years. < Lead emissions from motor vehicle gasoline combustion declined substantially. < Coal combustion and non-ferrous metal smelting are important emission sources.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 January 2012 Received in revised form 7 June 2012 Accepted 8 June 2012
Estimates of atmospheric emissions of lead from anthropogenic sources in China from 1990 to 2009 are presented with the information on emissions of both total lead and its spatial distribution in regions. The total emissions during the period 1990e2009 are nearly 200 000 tons. Motor vehicle gasoline combustion was the largest source of anthropogenic emissions. The estimated release of 117 800 t of lead represented 60% of the total emissions. Substantial decline occurred in 2001, when the total emissions were about 81% less than the 2000 value. The reduced lead content of motor vehicle gasoline is the primary reason for the decreased in lead emissions in 2001. After leaded gasoline was phased out, coal combustion became the principal source of emissions. Based on data on emissions from 2005 through 2009, the emissions are concentrated in eastern and central China due to the high level of coal consumption and non-ferrous metal smelting. The five provinces with the largest amounts of lead emissions are Shandong, Hebei, Shanxi, Henan and Jiangsu. These five regions produced nearly 40% of the total. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Atmospheric lead emission Emission sources Motor vehicle gasoline combustion Coal combustion Non-ferrous metal smelting
1. Introduction Lead (Pb) is one of the most hazardous heavy metals due to its toxic effects on the environment and on human health. Epidemiologic studies have shown that even at low exposure levels, chronic exposure to lead in humans may result in adverse effects on the blood and on the central nervous system (Lovei, 1998; Lustberg and Silbergeld, 2002; Pocock et al., 1988). Young children are especially sensitive to lead poisoning (Fowler, 1993). Lead pollution in the atmosphere is a serious problem in China (Chen et al., 2005; Duzgoren-Aydin, 2007; Ren et al., 2006). Consequently, the blood level of lead among Chinese children is higher than that of their counterparts in other countries (He et al., 2009; Wang and Zhang, 2006; Zheng et al., 2008).
* Corresponding author. Tel./fax: þ86 10 59893086. E-mail address: [email protected] (H. Cheng). 1352-2310/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.atmosenv.2012.06.025
The principal source of atmospheric lead pollution is anthropogenic lead emissions derived primarily from industrial activity (Wang et al., 2000). Energy generation and vehicular traffic have also contributed significantly to the increase in the levels of lead pollutants in the environment (Pacyna and Pacyna, 2009). Atmospheric emissions of lead from various sectors of the economy were influenced by the contamination of raw materials, physicochemical properties affecting the behavior of lead during industrial processes, the technology used in the industrial processes, and the type and efficiency of control equipment (Pacyna and Pacyna, 2001). The emission factors for the industrial processes and energy combustion have been calculated and used to estimate the levels of lead releases in Europe (Hutchinson and Meema, 1987; Pacyna and Pacyna, 2009). The annual amount of lead emissions in China is estimated, on the basis of economic statistics for 2001, as the fuel consumption and industrial production multiplied by the corresponding emission factors (Niisoe et al., 2011). Chinese scholars previously
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estimated the regional and local lead emissions from gasoline combustion (Qin, 2010a; Salamet and Zheng, 1998) and coal combustion (Luo et al., 2002; Qin, 2010b; Zhang et al., 2009). However, lead emissions from other sources and the total emissions have not yet been estimated in China. The lack of information on lead emissions in various sectors and areas in China makes timely measurements different. Moreover, without a comprehensive study of atmospheric lead emissions, China cannot conduct an accurate assessment of human and environmental health risks. Therefore, the present study aims to provide an inventory of lead emissions from anthropogenic activities and an analysis of the temporal and spatial variations of lead emissions in China, to estimate the lead emissions from different sources, and to identify the sectors that should control lead emissions. A detailed discussion of lead emissions according to sectors and regions can provide the basis of a management policy addressing the environmental health risk of lead emissions. 2. Materials and methods The methods for estimating emissions include material balances, emission factors, and source measurements. All of these methods are partially linked with each other. Emission factors are often based either on stack measurements or on material balances, including information about raw material characteristics, collector removal efficiencies, and industrial technology profiles (Hutchinson and Meema, 1987). Many countries have defined relatively complete categories of emission factors (EEA, 2009; EPA, 1995; NPI, 1999). Lead emissions from the main sources of emissions were estimated in this study. These sources included coal combustion, motor vehicle gasoline combustion, the combustion of oil, iron and steel production, cement production, non-ferrous metal smelting, and waste incineration. 2.1. Coal combustion sources In the present study, coal-fired sources of lead emissions were calculated according to the inventory methods for trace-metal atmospheric emissions inventory (Streets et al., 2005; Tian et al., 2010). The method incorporates the differences in the lead content of the coal consumed in different areas and the influences of various coal-fired boilers and control equipment in different economic sectors. Fuel consumption data and the specified lead emission efficiency represented by different combustion facilities, potential sources equipped with particulate filters, and SO2 control devices were used. The model of lead emissions is as follows:
Eij ¼ Cij Aij Fij ð1 PÞð1 PFGD Þ
(1)
where E is the amount of lead emissions; C is the lead content of the raw coal consumed by each province in China; A is the amount of coal consumption; F is the fraction of lead released from the coal combustion facility; P and PFGD are the lead removal efficiency of dust removal equipment and flue gas desulfurization (FGD) devices, respectively; i is the province (municipality or autonomous region); and j is the emission source classified by economic sector, combustion facility, and use of precipitators and SO2 control devices. From the China Energy Statistical Yearbook 2009 (NBS, 1995e2010), the largest coal-consuming sector is industry, followed by power utilities and residential use. Furthermore, the coal combustion sources can be divided into four economic sectors: power plants, industry, residential, and others (including farming, forestry, husbandry, fishing, water, construction, transportation, and retail).
2.1.1. Lead content of raw coal consumed The average lead content of raw coal in China has been measured by different methods (Bai et al., 2007; Tang, 2002; Zhuang et al., 1999). Due to the broad distribution of coal resources in China, the lead content of raw coal production is affected by various wide-ranging changes in the natural environment. Specifying the lead content of coal for different regions tends to make the results more accurate. The lead content data were averaged from different studies in the same province. A zero value is assigned to provinces that do not produce coal, such as Hainan and Guangdong. The average lead content in coal from geographically neighboring provinces can be used if no values are available from the existing literature. With the common practice of transporting coal between regions, the coal consumed in a given province may not usually be coal native to that province. Hence, the lead content of the coal consumed in each province should be used. Tian et al. (2010, 2011) provide a coal flow matrix to calculate the lead content of the raw coal consumed. The values of lead content in raw coal are summarized in Table S1 of Supplementary information. 2.1.2. Efficiency of coal combustion facilities and control equipments As a result of changing technology, different types of coalburning stoves were developed and show different lead release efficiencies. China does not have sufficient research information on the emission factors associated with coal combustion. For this reason, the average efficiency of boilers, particulate matter (PM) control devices, and FGD devices summarized from the literature were considered (Table S2 in Supplementary information). The industrial sector does not need to install FGD devices. The major combustion types for residential usage are traditional and improved cookstoves, which do not have any PM and SO2 control devices. Likewise, the major combustion devices used for other purpose are medium- and small-scale stoker-fired boilers, which are primarily used for supplying hot water and heating and have no PM and SO2 control devices (Tian et al., 2011). There is little research on the emission release rate for residential and other coal combustion applications, and for this reason the emission factor of 21 mg GJ1 was chosen as a reference value (EEA, 2009). However, due to the lack of detailed information on emission factors in different technologies, the estimates in this part of the present study are subject to high uncertainty. 2.2. Motor vehicle gasoline combustion sources The emissions from motor vehicle gasoline combustion can be estimated based on fuel consumption and specific emission factors (EEA, 2009; EPA, 1995; NPI, 2000). The determination of the emission factors depends on the national emissions standards and the lead content of gasoline. However, the national emissions standards implemented by China differ from the national standards used by other countries, and even the same emissions standards were defined in different periods. Therefore, we used the following formula to calculate the emissions from gasoline:
Egasoline ¼ 0:76KPb Qgasoline
(2)
where Egasoline is the lead emissions from gasoline, KPb is the lead content in gasoline, Qgasoline is the gasoline consumption, and 0.76 indicates that 76% of the lead contained in gasoline is emitted into the air. The estimates of the emission factors by the European Environment Agency (EEA) are based on the assumption that 75% of the lead contained in gasoline is emitted into the air (Hassel et al.,
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1987), where the National Environment Protection Council of Australia defined the proportion of lead in petrol emitted to the air as 77% (Biggins and Harrison, 1979). From these two values, we compute an average value of 76% of the lead in gasoline released into the atmosphere by moving motor vehicles. China stopped using leaded gasoline on July 1, 2000. The lead content in unleaded gasoline for motor vehicles should be no more than 0.005 g l1 (GB 17930-1999). KPb was chosen to be 0.005 g l1 for unleaded gasoline in the period 2001 through 2009, 0.35 g l1 for leaded gasoline for 1991e2000 (GB 484-89), and 0.64 g l1 for 1965e1990 (GB 484-64) (Qin, 2010a).
2.3. Non-ferrous metal smelting The non-ferrous metal smelters in China vary from sophisticated facilities with good emission controls to primitive artisanal smelting operations that have no controls at all. The efficiency values of different technologies and PM control facilities are summarized in Supplementary information Tables S3 and S4. The emissions can be calculated as follows:
Esmelting ¼ Qsmelting Cm fn
(3)
where Esmelting is the lead emissions from non-ferrous metal smelting; Qsmelting is the production of non-ferrous metal, namely, Pb, Zn and Cu for the purposes of the present study; C is the coefficient of pollution production for smelting technology m; and f is the efficiency of PM control facility n.
2.4. Other sources
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3. Results 3.1. Lead emissions from different sources from 1990 to 2009 in China The total and annual atmospheric lead emissions from various sources in China from 1990 to 2009 are shown in Table 2 and Fig. 1. The results show that the accumulated total emissions of lead in China from 1990 to 2009 are estimated to be 196 700 t (Table S5). Motor vehicle gasoline combustion was the largest emission source. The estimated release of 117 800 t of lead in twenty years represented 60% of the total lead emission. Coal combustion was the second largest source, followed by non-ferrous metal smelting. Fig. 1 shows that the emissions experienced two fluctuations over the 20-year period. The first emission decline occurred in 1991, when the total emissions were 3900 tons less than the 1990 value. The other sharp decline occurred in 2001, when the total emissions were 12 000 tons (81%) less than the 2000 value. However, the lead emissions continued to increase in the following year. The largest emissions of lead occurred in 2000, a release of 14 700 t of lead into the atmosphere. The smallest emissions occurred in 2001, with 2800 t of lead emissions released. The twenty-year period from 1990 to 2009 can be divided into two parts: the leaded gasoline period (1990e2000) and the unleaded gasoline period (2001e2009). During the leaded gasoline period, the annual motor vehicle gasoline combustion was the main emission source and contributed more than 78% of the total emissions. During the unleaded gasoline period, coal combustion was the largest emission source and contributed more than one half of the total emissions. 3.2. Spatial variation of lead emissions in China
The other sources of lead emissions are oil (kerosene and diesel fuel) combustion, iron and steel production, cement production, and waste incineration. The Pb emissions from these sources can be calculated by the activity level (production and energy consumption) multiplied by the emission factors for each source. The formula is as follows:
Eothers ¼ Qothers F
(4)
where Eothers is the emissions of lead, Qothers is fuel consumption or industrial production, and F is the emission factor. China has not performed sufficient research on emission factors. Although advanced technology has resulted in decreasing of emissions, the emission factors obtained during recent years are more appropriate for the actual conditions. Hence, we incorporated the results from authoritative sources and selected the emission factors presented by the European Environmental Agency and the US Environmental Protection Agency. The emission factors used in the present study are listed in Table 1.
The lead emissions by region from 2005 to 2009 are summarized in Fig. 2. The total of the lead emissions for the five-year period was 41 200 t (Table S6). The contributions to the five-year emissions from the top five emission-producing provinces were as follows: 5500 t from Shandong, 3000 t from Hebei, 2700 t from Shanxi, 2400 t from Henan, and 2300 t from Jiangsu. The five largest emission regions produced nearly 40% of the total. The histogram in Fig. 2 represents the emission structure in each region. In 16 regions, coal combustion contributed more than one-half of the total emissions. 4. Discussions 4.1. Temporal and spatial variation in lead emissions in China 4.1.1. Temporal variation from 1990 to 2009 The total lead emissions in China decreased from 13 700 t in 1990 to 9600 t in 2009. The annual emissions during this period Table 2 The atmospheric lead emissions from various sources in China in 1990e2009.
Table 1 The emission factors of other sources. Sources Iron and steel production Steel making Pig iron produced Oil combustion Kerosene Diesel Cement production Waste incineration
Emission factors
References
0.7 g Mg1 0.0006 g Mg1
EEA, 2009 EEA, 2009
4.1 mg GJ1 4.1 mg GJ1 36 105 kg Mg1 (EST) 3.8 105 kg Mg1 (FF) 0.8 g Mg1
EEA, 2009 EEA, 2009 EPA, 1995 EEA, 2009
Source
Emissions (t)
Coal combustion Motor vehicle gasoline combustion Non-ferrous metal smelting Cooper Lead Zinc Iron and steel industry Cement production Oil combustion Waste incineration Total
46 300 117 800 17 800 4100 4200 3000 3300 278 66 196 700
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Fig. 1. The atmospheric lead emissions in China in 1990e2009.
are much less than the value of 56 000 t yr1 estimated by the study of Niisoe (Niisoe et al., 2010). The primary reason for this reason is that the emission factors used in Niisoe’s study were taken from the research conducted by Nriagu and Pacyna in 1988. These factors are too large to apply to the current situation in
China and do not incorporate the relatively lower extent of penetration of advanced PM control devices (Tian et al., 2012). For example, the first China Pollution Source Census in 2008 surveyed the pollution production coefficients of different types of lead smelters. The largest coefficient found by this survey is 227
Fig. 2. Lead emissions by region from different sources in China in 2005e2009. Hong Kong, Macao and Taiwan are not included. Duo to the lack of some information about the amount of energy consumption and industrial production in Tibet, the emissions estimated may be low.
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(Table S3), approximately 10 times smaller than the value of 3000 in Nriagu and Pacyna’s study. The large amount of lead emissions can be explained by the growing demands for energy and increasing industrial production. As a result of these demands, the emissions are not only larger than the emissions in other countries but also showed an increasing trend (Pacyna and Pacyna, 2001). As observed in Fig. 1 (and Fig. S1), the decrease/increase in the total emissions is generally consistent with the variation in the trend of motor vehicle gasoline combustion emissions. 4.1.2. Spatial variation in China Fig. 2 shows the distribution of lead emissions in China from 2005 through 2009. The five provinces with the highest emissions were located in central and eastern China, the area with the greatest industrial production and energy consumption. Specifically, lead emissions from coal consumption are the major cause of pollution in the area as well as in northern China. In central and southern China, Anhui, Jiangxi, Hunan and Hubei provinces also have relatively large emissions. This finding results primarily from the emissions from non-ferrous metal smelting. Yunnan, Sichuan and Gansu are the provinces with the largest values of emissions in western China. Moreover, Yunnan and Gansu both have large amounts of non-ferrous metals smelting. In general, lead emissions in eastern China are larger than those in western China. 4.1.3. Variation in emissions among regions The annual emission growth rates by region for the years 2005e2009 are summarized in Fig. 3. During this five-year period, the emissions in most of the regions show a high rate of growth. The fastest-growing region is Qinghai province in 2007 (Tibet is excluded due to the lack of data), with an annual rate of increase of 44%. A negative growth rate appeared in certain regions, including Beijing, Chongqing, Guangdong and 11 other regions. Overall, however, the negative trends are much less common than the positive trends. Most of the negative growth rates observed in 2008 may be due to factors related to the 2008 Olympic Games in China. 4.2. Emissions from different sources
reduced in recent years because of the phasing out of leaded gasoline and because of controls on industrial emissions (Ilyin et al., 2007; Storch et al., 2003). Certain scholars (Pacyna and Pacyna, 2001) estimated that Chinese vehicular traffic sources emitted more than 8500 t of lead in 1995. In contrast, the present study estimated emissions of approximately 10 200 t. Fig. 1 illustrates that during the leaded gasoline period, from 1990 to 2000, the combustion of motor vehicle gasoline, which is the largest source of lead emissions in China, emitted 115 000 t of lead into the atmosphere, representing 80% of the total emissions. However, the emissions from this source were reduced substantially beginning in 2001 (the unleaded gasoline period), and the corresponding proportion is 5%. In terms of motor vehicle gasoline combustion, the five regions with the largest emissions are Guangdong (217 t), Shandong (148 t), Hubei (131 t), Jiangsu (130 t), and Zhejiang (115 t). The sum of these five largest emissions represented more than one-third of the total national emissions (1900 t). In contrast, Qinghai (5 t), Ningxia (5 t), Hainan (10 t), Jiangxi (18 t), and Gansu (19 t) are the five regions with the lowest emissions. Collectively, these regions released only 3% of the total (data from Tibet is not available). The results of the present study for motor vehicle gasoline combustion are very similar to the figures cited by Qin (Qin, 2010a). In 2008, the number of civilian motor vehicles in the Guangdong province is 5.73 million, followed by Shandong, Zhejiang, and Jiangsu (CATARC, 2009). The lead emissions from gasoline combustion are proportional to the regional total of civilian-owned motor vehicles. The reduced lead content of motor vehicle gasoline is the primary reason for the decreased in lead emissions in 1991 and 2001. Since leaded gasoline has been phased out in 2000, the average annual lead emissions from motor vehicle gasoline combustion were reduced by 97%, a substantial decrease. The large percentage reduction found in the present study is similar to the 98% reduction indicated in a previous study (Qin, 2010a). Particular attention should be directed to the excessive lead content found in leaded gasoline samples. For example, 15 samples of gasoline 90# in Beijing have exceeded the mandated lead content (0.35 g l1) by 64%, whereas 15 samples of gasoline 93# exceeded the mandated lead content (0.45 g l1) by 53% (Salamet and Zheng, 1998). Therefore, the estimate in our study of the emissions from leaded gasoline may be low. During the unleaded gasoline period (2001e2009), the General Administration of Quality Supervision, Inspection and Quarantine of China (AQSIQ) has performed spot checks on unleaded gasoline samples from gasoline stations in several regions. The lead content of these samples met the requirements for lead content (Table S7).
Annual Rate, %
4.2.1. Emissions from motor vehicle gasoline combustion Leaded gasoline combustion is considered to be the largest source of lead emissions (Ewing et al., 2010; Gon and Appelman, 2009; Niisoe et al., 2010). In contrast, certain scholars (Pacyna et al., 2007) believe that transport gasoline combustion is still the main source of anthropogenic lead emissions. In many developed countries, anthropogenic lead emissions have been markedly
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Fig. 3. The annual emission growth rates by region in 2005e2009.
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4.2.2. Emissions from coal combustion Coal is the primary energy source in China and coal combustion has increased dramatically during the past two decades (Ewing et al., 2010). A previous study (Tan et al., 2006) examined aerosol samples of PM10 particulates. This study showed that the atmospheric lead particulates in Shanghai during the winter of 2002e2003 were primarily from coal combustion after the elimination of leaded gasoline. Coal combustion, the second-largest emission source, released 46 300 t lead during the period 1990 through 2009. In this study, only raw coal combustion was considered. This category does not include coke, briquettes, or cleaned coal. Fig. 4 shows the distribution of the lead emissions in the coal combustion sector of China in 1990e2009. The industrial sector, the largest source of coal combustion, represented 83% of the total (38 200 t). Emissions from power plants have been increasing at an annual average growth rate of 9% since 1990 and reached 580 t in 2009. The emissions from the residential sector were reduced because traditional energy sources were gradually being replaced by clean fuel. For the same reason, the emissions from other sectors decreased initially. However, emissions again increased beginning in 2002 due to the significant increase in the urban transport sector. Moreover, energy consumption by urban buildings increased the emissions following the rapid increase in the urban population. Fig. 4 shows that negative growth in coal consumption was reported in 1997 and 1998. This result is due primarily to the Asian financial crisis (Hao et al., 2001). Fig. 4 also shows a large fluctuation in the emissions from coal combustion during or near the year 2000. Although the power plant sector has always presented a tendency toward rapid growth during this period, the above-mentioned decline in total emissions can be explained entirely by the decrease in coal consumption in the industrial, residential, and other sectors. A decrease in coal consumption was observed as improvements were made in the combustion efficiency of boilers and equipment due to the introduction of various control devices to save energy and reduce emissions (Zhao et al., 2008). However, as the economy recovered and production increased, the emission levels gradually increased beginning in 2001. The total emissions of lead from coal combustion are sensitive to changes in coal consumption in the industrial sector because industrial use is very large and the net emission rate is relatively higher (Tian et al., 2010). The other reason for the decrease in lead emissions in 2000 is the reduction in coal consumption in the industrial and residential sectors due to the application of energy-saving technology. Emissions in China were decreased since the beginning of the 21st century with the rapid growth of energy-saving technology. 4.2.3. Emissions from non-ferrous smelting The copperenickel industry emits larger quantities of trace metals (except for Hg and Zn) than the lead and zinc industries
(Pacyna and Pacyna, 2001). Copper smelting, the largest source of emissions from non-ferrous smelting in China, emitted 17 800 t (9%) of lead during the period 1990e2009. Lead and zinc smelting released 4100 t and 4200 t, respectively, representing 2% of the total non-ferrous smelting emissions. With the growth of production, emissions from non-ferrous metal smelting sources increased continuously each year. Although these sources are not the largest sources of emissions, the concentration of emissions in the absence of effective control equipment represents significant health hazards for the surrounding population. During recent years, several cases of blood lead poisoning have been examined in China. Most of these cases were caused by lead pollution from nearby non-ferrous smelting plants, especially lead-zinc smelting plants. Small- and mediumsized enterprises located in remote areas with crude production facilities and defective emissions management systems were involved in most of these cases. Certain small companies do not comply with the environmental impact assessment and environmental inspection procedures. This situation produces a large number of pollution incidents. Moreover, most of the production from these small plants has not been included in the national statistical data used in the present study. Jiangxi, Anhui, Yunnan, Gansu and Henan are the principal regions in which China should devote more attention to the non-ferrous smelting sector. 4.2.4. Other sources Since the 1990s and up to a few years ago, electrostatic precipitators (ESTs) were widely used in cement kilns in China. Along with the development of dust emission requirements, fabric filters (FFs) gradually replaced ESTs due to the high collection efficiency of FFs. However, the proportion of FFs is still small, and the production of cement is increasing as the demand expands. These factors both contribute to higher lead emissions from cement production in China. Certain scholars noted that the emissions of trace metals from the iron and steel industry are substantially lower than the emissions from other major sources. Thus, this source will not have a significant impact on the quality of the estimates of total emissions of trace metals worldwide (Pacyna and Pacyna, 2001). However, in the present study, the lead emissions estimated to result from iron and steel production are relative high due to the substantial amount of iron and steel production in China. Production by this industry has substantially increased since the 1990s. As the world’s largest producer and consumer, China represents nearly one-half of the world’s iron and steel production, a value greater than the total iron and steel production of the 20 next-highest countries. The iron and steel industry has the highest energy consumption and highest pollution levels and became the fifthhighest source of emissions source during 2001e2009 in China (Fig. 1). In general, the emissions from waste incineration and oil combustion are increasing each year. Waste incineration is developing in China due to the lack of space for new landfills and is playing an increasingly important role in municipal solid waste management in China (Nie, 2008). Only kerosene and diesel were included as sources of oil combustion in this study. 4.3. Uncertainty analysis
Fig. 4. Distribution of lead emissions in the coal combustion sector of China in 1990e2009.
Ideally, data for the accurate estimation of lead emissions should be obtained through proper sampling and measurement methods. If this approach is not feasible in particular cases, emissions can be estimated from existing data on the levels of activity and emission factors. However, it is different to make accurate assessments of current atmospheric emissions based on limited information about
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emission factors and specific statistical data. The emission factors used in this study were cited from research references from other countries and are not accurate for use in the estimation of Chinese emissions due to the differences in boiler combustion efficiency, control devices, and production technology. However, the use of information about the lead content of raw materials and about energy can increase the accuracy of the estimation. Finally, the emissions from at least the major sources, such as large power plants, smelters, steel and iron plants, and cement kilns should be measured. The mining industry and the lead-acid battery industry were not considered in the present study due to a lack of activity data. To obtain better and more reliable estimates of lead emissions, long-term field testing and continuous monitoring of all types of combustion facilities and technology in China warrant further investigation (Tian et al., 2011). 5. Conclusions Detailed estimates of China’s lead emissions from different sources by region from 1990 to 2009 were presented in this study. A substantial decrease in lead emissions occurred at the beginning of 21st century. The principal causes of this decrease were a reduction of the lead content of motor vehicle gasoline and a cutback in coal consumption in the industrial and residential sectors. However, the downward trend did not persist, and the emissions increased gradually during the following years. Motor vehicle gasoline combustion was the largest source of emissions from 1990 through 2009. After leaded gasoline was phased out, coal combustion became the principal source of emissions due to the country’s substantial production activities. Based on data on emissions from 2005 through 2009, Shandong and Hebei are the provinces with the largest amounts of emissions in China. The emissions are concentrated in eastern and central China due to the high level of coal consumption and non-ferrous metal smelting. The results of the present study can be used in atmospheric models of lead pollution to analyze deposition in the atmosphere and environmental concentrations. The findings also furnish important information for assessing the health effects of blood lead levels in the population. These lead levels will be considered in future research on environmental health risk assessment. Acknowledgments This research work was funded by the National Natural Science Foundation of China (key project 40930740 and general project 41171384) and Special Environmental Research Funds for Public Welfare (No. 201009046 and No. 201109064). Appendix A. Supplementary information Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.atmosenv.2012.06.025. References Bai, X.F., Li, W.H., Chen, Y.F., Jiang, Y., 2007. The general distributions of trace elements in Chinese coals (In Chinese with abstract in English). Coal Quality Technology 1, 1e4. Biggins, P.D.E., Harrison, R.M., 1979. Atmospheric chemistry of automotive lead. Environmental Science & Technology 13 (5), 558e565. China Automotive Technology and Research Center (CATARC), 2009. China Automotive Industry Yearbook. China Automotive Industry Yearbook House, 613 pp. Chen, J.M., Tan, M.G., Li, Y.L., et al., 2005. A lead isotope record of shanghai atmospheric lead emissions in total suspended particles during the period of phasing out of leaded gasoline. Atmospheric Environment 39 (7), 1245e1253.
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Emissions Estimation Techniques Manual: Aggregated Emissions from Fuel Combustion (Sub-threshold), Environment Australia. http://www.npi.gov.au/publications/aedmanuals/pubs/subcombustion_ ff.pdf. National Pollutant Inventory (NPI), 2000. Emissions Estimation Technique Manual for Aggregated Emissions from Motor Vehicles. National Environment Protection Council (NEPC), Australia. http://www2.unitar.org/cwm/publications/cbl/ prtr/pdf/cat5/Australia_motorvehicles.pdf. Pacyna, J.M., Pacyna, E.G., 2001. An assessment of global and regional emissions of trace metals to the atmosphere from anthropogenic sources worldwide. Environmental Reviews 9 (4), 269e298. Pacyna, J.M., Pacyna, E.G., 2009. Changes of emissions and atmospheric deposition of mercury, lead, and cadmium. Atmospheric Environment 43 (1), 117e127. Pacyna, E.G., Pacyna, J.M., Fudala, J., et al., 2007. Current and future emissions of selected heavy metals to the atmosphere from anthropogenic sources in Europe. Atmospheric Environment 41 (38), 8557e8566. Pocock, S.J., Shaper, A.G., Ashby, D., et al., 1988. The relationship between blood lead, blood pressure, stroke, and heart attacks in middle-aged British men. Environmental Health Perspectives 78, 23e30. Qin, J.F., 2010a. Estimation of lead emission to atmospheric from gasoline combustion (In Chinese with abstract in English). Guangdong Trace Elements Science 17 (10), 27e34. Qin, J.F., 2010b. Estimation of lead emissions to atmospheric from coal combustion in China, 1953e2005 (In Chinese with abstract in English). Guangdong Trace Elements Science 17 (8), 27e35. Ren, H.M., Wang, J.D., Zhang, X.L., 2006. Assessment of soil lead exposure in children in Shenyang, China. Environmental Pollution 144 (1), 327e335. Salamet, Zheng, X., 1998. Investigation on lead pollution to children in China (In Chinese). Guangdong Trace Elements Science 5 (5), 10e17. Storch, H., Costa-Cabrala, M., Hagnera, C., et al., 2003. Four decades of gasoline lead emissions and control policies in Europe: a retrospective assessment. Science of the Total Environment 311 (1e3), 151e176. Streets, D.G., Hao, J.M., Wu, Y., et al., 2005. Anthropogenic mercury emissions in China. Atmospheric Environment 39 (40), 7789e7806. Tan, M.G., Zhang, G.L., Li, X.L., et al., 2006. Comprehensive study of lead pollution in shanghai by multiple technique. Analytical Chemistry 78, 8044e8050. Tang, X., 2002. Modes of occurrence of trace elements in coals (In Chinese). Coal Geology of China 14, 5e17. Tian, H.Z., Wang, Y., Xue, Z.G., et al., 2010. Trend and characteristics of atmospheric emissions of Hg, As, and Se from coal combustion in China, 1980e2007. Atmospheric Chemistry and Physics 10 (23), 11905e11919.
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Tian, H.Z., Zhao, D., He, M.C., et al., 2011. Temporal and spatial distribution of atmospheric antimony emission inventories from coal combustion in China. Environmental Pollution 159 (6), 1613e1619. Tian, H.Z., Cheng, K., Wang, Y., et al., 2012. Temporal and spatial variation characteristics of atmospheric emissions of Cd, Cr, and Pb from coal in China. Atmospheric Environment 50, 157e163. U.S. Environmental Protection Agency (EPA), 1995. Emissions Factors & AP 42, Compilation of Air Pollutant Emission Factors. http://www.epa.gov/ttn/chief/ap42/. Wang, S.H., Zhang, J.L., 2006. Blood lead levels in children, China. Environmental Research 101 (3), 412e418. Wang, J., Guo, P., Li, X., et al., 2000. Source identification of lead pollution in the atmosphere of Shanghai City by analyzing single aerosol particles (SAP). Environmental Science & Technology 34, 1900e1905.
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Contents lists available at SciVerse ScienceDirect
Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv
The estimated atmospheric lead emissions in China, 1990e2009 Qian Li a, Hongguang Cheng a, *, Tan Zhou a, Chunye Lin a, Shu Guo b a b
School of Environment, Beijing Normal University, Beijing 100875, China South China Institute of Environmental Sciences, MEP, Guangzhou 510655, China
h i g h l i g h t s < We provide an inventory of lead emissions from anthropogenic activities in China. < We provide an analysis of the temporal and spatial variations of lead emissions. < The emission structure of lead changed in the last 20 years. < Lead emissions from motor vehicle gasoline combustion declined substantially. < Coal combustion and non-ferrous metal smelting are important emission sources.
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 January 2012 Received in revised form 7 June 2012 Accepted 8 June 2012
Estimates of atmospheric emissions of lead from anthropogenic sources in China from 1990 to 2009 are presented with the information on emissions of both total lead and its spatial distribution in regions. The total emissions during the period 1990e2009 are nearly 200 000 tons. Motor vehicle gasoline combustion was the largest source of anthropogenic emissions. The estimated release of 117 800 t of lead represented 60% of the total emissions. Substantial decline occurred in 2001, when the total emissions were about 81% less than the 2000 value. The reduced lead content of motor vehicle gasoline is the primary reason for the decreased in lead emissions in 2001. After leaded gasoline was phased out, coal combustion became the principal source of emissions. Based on data on emissions from 2005 through 2009, the emissions are concentrated in eastern and central China due to the high level of coal consumption and non-ferrous metal smelting. The five provinces with the largest amounts of lead emissions are Shandong, Hebei, Shanxi, Henan and Jiangsu. These five regions produced nearly 40% of the total. Ó 2012 Elsevier Ltd. All rights reserved.
Keywords: Atmospheric lead emission Emission sources Motor vehicle gasoline combustion Coal combustion Non-ferrous metal smelting
1. Introduction Lead (Pb) is one of the most hazardous heavy metals due to its toxic effects on the environment and on human health. Epidemiologic studies have shown that even at low exposure levels, chronic exposure to lead in humans may result in adverse effects on the blood and on the central nervous system (Lovei, 1998; Lustberg and Silbergeld, 2002; Pocock et al., 1988). Young children are especially sensitive to lead poisoning (Fowler, 1993). Lead pollution in the atmosphere is a serious problem in China (Chen et al., 2005; Duzgoren-Aydin, 2007; Ren et al., 2006). Consequently, the blood level of lead among Chinese children is higher than that of their counterparts in other countries (He et al., 2009; Wang and Zhang, 2006; Zheng et al., 2008).
* Corresponding author. Tel./fax: þ86 10 59893086. E-mail address: [email protected] (H. Cheng). 1352-2310/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.atmosenv.2012.06.025
The principal source of atmospheric lead pollution is anthropogenic lead emissions derived primarily from industrial activity (Wang et al., 2000). Energy generation and vehicular traffic have also contributed significantly to the increase in the levels of lead pollutants in the environment (Pacyna and Pacyna, 2009). Atmospheric emissions of lead from various sectors of the economy were influenced by the contamination of raw materials, physicochemical properties affecting the behavior of lead during industrial processes, the technology used in the industrial processes, and the type and efficiency of control equipment (Pacyna and Pacyna, 2001). The emission factors for the industrial processes and energy combustion have been calculated and used to estimate the levels of lead releases in Europe (Hutchinson and Meema, 1987; Pacyna and Pacyna, 2009). The annual amount of lead emissions in China is estimated, on the basis of economic statistics for 2001, as the fuel consumption and industrial production multiplied by the corresponding emission factors (Niisoe et al., 2011). Chinese scholars previously
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estimated the regional and local lead emissions from gasoline combustion (Qin, 2010a; Salamet and Zheng, 1998) and coal combustion (Luo et al., 2002; Qin, 2010b; Zhang et al., 2009). However, lead emissions from other sources and the total emissions have not yet been estimated in China. The lack of information on lead emissions in various sectors and areas in China makes timely measurements different. Moreover, without a comprehensive study of atmospheric lead emissions, China cannot conduct an accurate assessment of human and environmental health risks. Therefore, the present study aims to provide an inventory of lead emissions from anthropogenic activities and an analysis of the temporal and spatial variations of lead emissions in China, to estimate the lead emissions from different sources, and to identify the sectors that should control lead emissions. A detailed discussion of lead emissions according to sectors and regions can provide the basis of a management policy addressing the environmental health risk of lead emissions. 2. Materials and methods The methods for estimating emissions include material balances, emission factors, and source measurements. All of these methods are partially linked with each other. Emission factors are often based either on stack measurements or on material balances, including information about raw material characteristics, collector removal efficiencies, and industrial technology profiles (Hutchinson and Meema, 1987). Many countries have defined relatively complete categories of emission factors (EEA, 2009; EPA, 1995; NPI, 1999). Lead emissions from the main sources of emissions were estimated in this study. These sources included coal combustion, motor vehicle gasoline combustion, the combustion of oil, iron and steel production, cement production, non-ferrous metal smelting, and waste incineration. 2.1. Coal combustion sources In the present study, coal-fired sources of lead emissions were calculated according to the inventory methods for trace-metal atmospheric emissions inventory (Streets et al., 2005; Tian et al., 2010). The method incorporates the differences in the lead content of the coal consumed in different areas and the influences of various coal-fired boilers and control equipment in different economic sectors. Fuel consumption data and the specified lead emission efficiency represented by different combustion facilities, potential sources equipped with particulate filters, and SO2 control devices were used. The model of lead emissions is as follows:
Eij ¼ Cij Aij Fij ð1 PÞð1 PFGD Þ
(1)
where E is the amount of lead emissions; C is the lead content of the raw coal consumed by each province in China; A is the amount of coal consumption; F is the fraction of lead released from the coal combustion facility; P and PFGD are the lead removal efficiency of dust removal equipment and flue gas desulfurization (FGD) devices, respectively; i is the province (municipality or autonomous region); and j is the emission source classified by economic sector, combustion facility, and use of precipitators and SO2 control devices. From the China Energy Statistical Yearbook 2009 (NBS, 1995e2010), the largest coal-consuming sector is industry, followed by power utilities and residential use. Furthermore, the coal combustion sources can be divided into four economic sectors: power plants, industry, residential, and others (including farming, forestry, husbandry, fishing, water, construction, transportation, and retail).
2.1.1. Lead content of raw coal consumed The average lead content of raw coal in China has been measured by different methods (Bai et al., 2007; Tang, 2002; Zhuang et al., 1999). Due to the broad distribution of coal resources in China, the lead content of raw coal production is affected by various wide-ranging changes in the natural environment. Specifying the lead content of coal for different regions tends to make the results more accurate. The lead content data were averaged from different studies in the same province. A zero value is assigned to provinces that do not produce coal, such as Hainan and Guangdong. The average lead content in coal from geographically neighboring provinces can be used if no values are available from the existing literature. With the common practice of transporting coal between regions, the coal consumed in a given province may not usually be coal native to that province. Hence, the lead content of the coal consumed in each province should be used. Tian et al. (2010, 2011) provide a coal flow matrix to calculate the lead content of the raw coal consumed. The values of lead content in raw coal are summarized in Table S1 of Supplementary information. 2.1.2. Efficiency of coal combustion facilities and control equipments As a result of changing technology, different types of coalburning stoves were developed and show different lead release efficiencies. China does not have sufficient research information on the emission factors associated with coal combustion. For this reason, the average efficiency of boilers, particulate matter (PM) control devices, and FGD devices summarized from the literature were considered (Table S2 in Supplementary information). The industrial sector does not need to install FGD devices. The major combustion types for residential usage are traditional and improved cookstoves, which do not have any PM and SO2 control devices. Likewise, the major combustion devices used for other purpose are medium- and small-scale stoker-fired boilers, which are primarily used for supplying hot water and heating and have no PM and SO2 control devices (Tian et al., 2011). There is little research on the emission release rate for residential and other coal combustion applications, and for this reason the emission factor of 21 mg GJ1 was chosen as a reference value (EEA, 2009). However, due to the lack of detailed information on emission factors in different technologies, the estimates in this part of the present study are subject to high uncertainty. 2.2. Motor vehicle gasoline combustion sources The emissions from motor vehicle gasoline combustion can be estimated based on fuel consumption and specific emission factors (EEA, 2009; EPA, 1995; NPI, 2000). The determination of the emission factors depends on the national emissions standards and the lead content of gasoline. However, the national emissions standards implemented by China differ from the national standards used by other countries, and even the same emissions standards were defined in different periods. Therefore, we used the following formula to calculate the emissions from gasoline:
Egasoline ¼ 0:76KPb Qgasoline
(2)
where Egasoline is the lead emissions from gasoline, KPb is the lead content in gasoline, Qgasoline is the gasoline consumption, and 0.76 indicates that 76% of the lead contained in gasoline is emitted into the air. The estimates of the emission factors by the European Environment Agency (EEA) are based on the assumption that 75% of the lead contained in gasoline is emitted into the air (Hassel et al.,
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1987), where the National Environment Protection Council of Australia defined the proportion of lead in petrol emitted to the air as 77% (Biggins and Harrison, 1979). From these two values, we compute an average value of 76% of the lead in gasoline released into the atmosphere by moving motor vehicles. China stopped using leaded gasoline on July 1, 2000. The lead content in unleaded gasoline for motor vehicles should be no more than 0.005 g l1 (GB 17930-1999). KPb was chosen to be 0.005 g l1 for unleaded gasoline in the period 2001 through 2009, 0.35 g l1 for leaded gasoline for 1991e2000 (GB 484-89), and 0.64 g l1 for 1965e1990 (GB 484-64) (Qin, 2010a).
2.3. Non-ferrous metal smelting The non-ferrous metal smelters in China vary from sophisticated facilities with good emission controls to primitive artisanal smelting operations that have no controls at all. The efficiency values of different technologies and PM control facilities are summarized in Supplementary information Tables S3 and S4. The emissions can be calculated as follows:
Esmelting ¼ Qsmelting Cm fn
(3)
where Esmelting is the lead emissions from non-ferrous metal smelting; Qsmelting is the production of non-ferrous metal, namely, Pb, Zn and Cu for the purposes of the present study; C is the coefficient of pollution production for smelting technology m; and f is the efficiency of PM control facility n.
2.4. Other sources
3
3. Results 3.1. Lead emissions from different sources from 1990 to 2009 in China The total and annual atmospheric lead emissions from various sources in China from 1990 to 2009 are shown in Table 2 and Fig. 1. The results show that the accumulated total emissions of lead in China from 1990 to 2009 are estimated to be 196 700 t (Table S5). Motor vehicle gasoline combustion was the largest emission source. The estimated release of 117 800 t of lead in twenty years represented 60% of the total lead emission. Coal combustion was the second largest source, followed by non-ferrous metal smelting. Fig. 1 shows that the emissions experienced two fluctuations over the 20-year period. The first emission decline occurred in 1991, when the total emissions were 3900 tons less than the 1990 value. The other sharp decline occurred in 2001, when the total emissions were 12 000 tons (81%) less than the 2000 value. However, the lead emissions continued to increase in the following year. The largest emissions of lead occurred in 2000, a release of 14 700 t of lead into the atmosphere. The smallest emissions occurred in 2001, with 2800 t of lead emissions released. The twenty-year period from 1990 to 2009 can be divided into two parts: the leaded gasoline period (1990e2000) and the unleaded gasoline period (2001e2009). During the leaded gasoline period, the annual motor vehicle gasoline combustion was the main emission source and contributed more than 78% of the total emissions. During the unleaded gasoline period, coal combustion was the largest emission source and contributed more than one half of the total emissions. 3.2. Spatial variation of lead emissions in China
The other sources of lead emissions are oil (kerosene and diesel fuel) combustion, iron and steel production, cement production, and waste incineration. The Pb emissions from these sources can be calculated by the activity level (production and energy consumption) multiplied by the emission factors for each source. The formula is as follows:
Eothers ¼ Qothers F
(4)
where Eothers is the emissions of lead, Qothers is fuel consumption or industrial production, and F is the emission factor. China has not performed sufficient research on emission factors. Although advanced technology has resulted in decreasing of emissions, the emission factors obtained during recent years are more appropriate for the actual conditions. Hence, we incorporated the results from authoritative sources and selected the emission factors presented by the European Environmental Agency and the US Environmental Protection Agency. The emission factors used in the present study are listed in Table 1.
The lead emissions by region from 2005 to 2009 are summarized in Fig. 2. The total of the lead emissions for the five-year period was 41 200 t (Table S6). The contributions to the five-year emissions from the top five emission-producing provinces were as follows: 5500 t from Shandong, 3000 t from Hebei, 2700 t from Shanxi, 2400 t from Henan, and 2300 t from Jiangsu. The five largest emission regions produced nearly 40% of the total. The histogram in Fig. 2 represents the emission structure in each region. In 16 regions, coal combustion contributed more than one-half of the total emissions. 4. Discussions 4.1. Temporal and spatial variation in lead emissions in China 4.1.1. Temporal variation from 1990 to 2009 The total lead emissions in China decreased from 13 700 t in 1990 to 9600 t in 2009. The annual emissions during this period Table 2 The atmospheric lead emissions from various sources in China in 1990e2009.
Table 1 The emission factors of other sources. Sources Iron and steel production Steel making Pig iron produced Oil combustion Kerosene Diesel Cement production Waste incineration
Emission factors
References
0.7 g Mg1 0.0006 g Mg1
EEA, 2009 EEA, 2009
4.1 mg GJ1 4.1 mg GJ1 36 105 kg Mg1 (EST) 3.8 105 kg Mg1 (FF) 0.8 g Mg1
EEA, 2009 EEA, 2009 EPA, 1995 EEA, 2009
Source
Emissions (t)
Coal combustion Motor vehicle gasoline combustion Non-ferrous metal smelting Cooper Lead Zinc Iron and steel industry Cement production Oil combustion Waste incineration Total
46 300 117 800 17 800 4100 4200 3000 3300 278 66 196 700
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Fig. 1. The atmospheric lead emissions in China in 1990e2009.
are much less than the value of 56 000 t yr1 estimated by the study of Niisoe (Niisoe et al., 2010). The primary reason for this reason is that the emission factors used in Niisoe’s study were taken from the research conducted by Nriagu and Pacyna in 1988. These factors are too large to apply to the current situation in
China and do not incorporate the relatively lower extent of penetration of advanced PM control devices (Tian et al., 2012). For example, the first China Pollution Source Census in 2008 surveyed the pollution production coefficients of different types of lead smelters. The largest coefficient found by this survey is 227
Fig. 2. Lead emissions by region from different sources in China in 2005e2009. Hong Kong, Macao and Taiwan are not included. Duo to the lack of some information about the amount of energy consumption and industrial production in Tibet, the emissions estimated may be low.
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(Table S3), approximately 10 times smaller than the value of 3000 in Nriagu and Pacyna’s study. The large amount of lead emissions can be explained by the growing demands for energy and increasing industrial production. As a result of these demands, the emissions are not only larger than the emissions in other countries but also showed an increasing trend (Pacyna and Pacyna, 2001). As observed in Fig. 1 (and Fig. S1), the decrease/increase in the total emissions is generally consistent with the variation in the trend of motor vehicle gasoline combustion emissions. 4.1.2. Spatial variation in China Fig. 2 shows the distribution of lead emissions in China from 2005 through 2009. The five provinces with the highest emissions were located in central and eastern China, the area with the greatest industrial production and energy consumption. Specifically, lead emissions from coal consumption are the major cause of pollution in the area as well as in northern China. In central and southern China, Anhui, Jiangxi, Hunan and Hubei provinces also have relatively large emissions. This finding results primarily from the emissions from non-ferrous metal smelting. Yunnan, Sichuan and Gansu are the provinces with the largest values of emissions in western China. Moreover, Yunnan and Gansu both have large amounts of non-ferrous metals smelting. In general, lead emissions in eastern China are larger than those in western China. 4.1.3. Variation in emissions among regions The annual emission growth rates by region for the years 2005e2009 are summarized in Fig. 3. During this five-year period, the emissions in most of the regions show a high rate of growth. The fastest-growing region is Qinghai province in 2007 (Tibet is excluded due to the lack of data), with an annual rate of increase of 44%. A negative growth rate appeared in certain regions, including Beijing, Chongqing, Guangdong and 11 other regions. Overall, however, the negative trends are much less common than the positive trends. Most of the negative growth rates observed in 2008 may be due to factors related to the 2008 Olympic Games in China. 4.2. Emissions from different sources
reduced in recent years because of the phasing out of leaded gasoline and because of controls on industrial emissions (Ilyin et al., 2007; Storch et al., 2003). Certain scholars (Pacyna and Pacyna, 2001) estimated that Chinese vehicular traffic sources emitted more than 8500 t of lead in 1995. In contrast, the present study estimated emissions of approximately 10 200 t. Fig. 1 illustrates that during the leaded gasoline period, from 1990 to 2000, the combustion of motor vehicle gasoline, which is the largest source of lead emissions in China, emitted 115 000 t of lead into the atmosphere, representing 80% of the total emissions. However, the emissions from this source were reduced substantially beginning in 2001 (the unleaded gasoline period), and the corresponding proportion is 5%. In terms of motor vehicle gasoline combustion, the five regions with the largest emissions are Guangdong (217 t), Shandong (148 t), Hubei (131 t), Jiangsu (130 t), and Zhejiang (115 t). The sum of these five largest emissions represented more than one-third of the total national emissions (1900 t). In contrast, Qinghai (5 t), Ningxia (5 t), Hainan (10 t), Jiangxi (18 t), and Gansu (19 t) are the five regions with the lowest emissions. Collectively, these regions released only 3% of the total (data from Tibet is not available). The results of the present study for motor vehicle gasoline combustion are very similar to the figures cited by Qin (Qin, 2010a). In 2008, the number of civilian motor vehicles in the Guangdong province is 5.73 million, followed by Shandong, Zhejiang, and Jiangsu (CATARC, 2009). The lead emissions from gasoline combustion are proportional to the regional total of civilian-owned motor vehicles. The reduced lead content of motor vehicle gasoline is the primary reason for the decreased in lead emissions in 1991 and 2001. Since leaded gasoline has been phased out in 2000, the average annual lead emissions from motor vehicle gasoline combustion were reduced by 97%, a substantial decrease. The large percentage reduction found in the present study is similar to the 98% reduction indicated in a previous study (Qin, 2010a). Particular attention should be directed to the excessive lead content found in leaded gasoline samples. For example, 15 samples of gasoline 90# in Beijing have exceeded the mandated lead content (0.35 g l1) by 64%, whereas 15 samples of gasoline 93# exceeded the mandated lead content (0.45 g l1) by 53% (Salamet and Zheng, 1998). Therefore, the estimate in our study of the emissions from leaded gasoline may be low. During the unleaded gasoline period (2001e2009), the General Administration of Quality Supervision, Inspection and Quarantine of China (AQSIQ) has performed spot checks on unleaded gasoline samples from gasoline stations in several regions. The lead content of these samples met the requirements for lead content (Table S7).
Annual Rate, %
4.2.1. Emissions from motor vehicle gasoline combustion Leaded gasoline combustion is considered to be the largest source of lead emissions (Ewing et al., 2010; Gon and Appelman, 2009; Niisoe et al., 2010). In contrast, certain scholars (Pacyna et al., 2007) believe that transport gasoline combustion is still the main source of anthropogenic lead emissions. In many developed countries, anthropogenic lead emissions have been markedly
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Fig. 3. The annual emission growth rates by region in 2005e2009.
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4.2.2. Emissions from coal combustion Coal is the primary energy source in China and coal combustion has increased dramatically during the past two decades (Ewing et al., 2010). A previous study (Tan et al., 2006) examined aerosol samples of PM10 particulates. This study showed that the atmospheric lead particulates in Shanghai during the winter of 2002e2003 were primarily from coal combustion after the elimination of leaded gasoline. Coal combustion, the second-largest emission source, released 46 300 t lead during the period 1990 through 2009. In this study, only raw coal combustion was considered. This category does not include coke, briquettes, or cleaned coal. Fig. 4 shows the distribution of the lead emissions in the coal combustion sector of China in 1990e2009. The industrial sector, the largest source of coal combustion, represented 83% of the total (38 200 t). Emissions from power plants have been increasing at an annual average growth rate of 9% since 1990 and reached 580 t in 2009. The emissions from the residential sector were reduced because traditional energy sources were gradually being replaced by clean fuel. For the same reason, the emissions from other sectors decreased initially. However, emissions again increased beginning in 2002 due to the significant increase in the urban transport sector. Moreover, energy consumption by urban buildings increased the emissions following the rapid increase in the urban population. Fig. 4 shows that negative growth in coal consumption was reported in 1997 and 1998. This result is due primarily to the Asian financial crisis (Hao et al., 2001). Fig. 4 also shows a large fluctuation in the emissions from coal combustion during or near the year 2000. Although the power plant sector has always presented a tendency toward rapid growth during this period, the above-mentioned decline in total emissions can be explained entirely by the decrease in coal consumption in the industrial, residential, and other sectors. A decrease in coal consumption was observed as improvements were made in the combustion efficiency of boilers and equipment due to the introduction of various control devices to save energy and reduce emissions (Zhao et al., 2008). However, as the economy recovered and production increased, the emission levels gradually increased beginning in 2001. The total emissions of lead from coal combustion are sensitive to changes in coal consumption in the industrial sector because industrial use is very large and the net emission rate is relatively higher (Tian et al., 2010). The other reason for the decrease in lead emissions in 2000 is the reduction in coal consumption in the industrial and residential sectors due to the application of energy-saving technology. Emissions in China were decreased since the beginning of the 21st century with the rapid growth of energy-saving technology. 4.2.3. Emissions from non-ferrous smelting The copperenickel industry emits larger quantities of trace metals (except for Hg and Zn) than the lead and zinc industries
(Pacyna and Pacyna, 2001). Copper smelting, the largest source of emissions from non-ferrous smelting in China, emitted 17 800 t (9%) of lead during the period 1990e2009. Lead and zinc smelting released 4100 t and 4200 t, respectively, representing 2% of the total non-ferrous smelting emissions. With the growth of production, emissions from non-ferrous metal smelting sources increased continuously each year. Although these sources are not the largest sources of emissions, the concentration of emissions in the absence of effective control equipment represents significant health hazards for the surrounding population. During recent years, several cases of blood lead poisoning have been examined in China. Most of these cases were caused by lead pollution from nearby non-ferrous smelting plants, especially lead-zinc smelting plants. Small- and mediumsized enterprises located in remote areas with crude production facilities and defective emissions management systems were involved in most of these cases. Certain small companies do not comply with the environmental impact assessment and environmental inspection procedures. This situation produces a large number of pollution incidents. Moreover, most of the production from these small plants has not been included in the national statistical data used in the present study. Jiangxi, Anhui, Yunnan, Gansu and Henan are the principal regions in which China should devote more attention to the non-ferrous smelting sector. 4.2.4. Other sources Since the 1990s and up to a few years ago, electrostatic precipitators (ESTs) were widely used in cement kilns in China. Along with the development of dust emission requirements, fabric filters (FFs) gradually replaced ESTs due to the high collection efficiency of FFs. However, the proportion of FFs is still small, and the production of cement is increasing as the demand expands. These factors both contribute to higher lead emissions from cement production in China. Certain scholars noted that the emissions of trace metals from the iron and steel industry are substantially lower than the emissions from other major sources. Thus, this source will not have a significant impact on the quality of the estimates of total emissions of trace metals worldwide (Pacyna and Pacyna, 2001). However, in the present study, the lead emissions estimated to result from iron and steel production are relative high due to the substantial amount of iron and steel production in China. Production by this industry has substantially increased since the 1990s. As the world’s largest producer and consumer, China represents nearly one-half of the world’s iron and steel production, a value greater than the total iron and steel production of the 20 next-highest countries. The iron and steel industry has the highest energy consumption and highest pollution levels and became the fifthhighest source of emissions source during 2001e2009 in China (Fig. 1). In general, the emissions from waste incineration and oil combustion are increasing each year. Waste incineration is developing in China due to the lack of space for new landfills and is playing an increasingly important role in municipal solid waste management in China (Nie, 2008). Only kerosene and diesel were included as sources of oil combustion in this study. 4.3. Uncertainty analysis
Fig. 4. Distribution of lead emissions in the coal combustion sector of China in 1990e2009.
Ideally, data for the accurate estimation of lead emissions should be obtained through proper sampling and measurement methods. If this approach is not feasible in particular cases, emissions can be estimated from existing data on the levels of activity and emission factors. However, it is different to make accurate assessments of current atmospheric emissions based on limited information about
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emission factors and specific statistical data. The emission factors used in this study were cited from research references from other countries and are not accurate for use in the estimation of Chinese emissions due to the differences in boiler combustion efficiency, control devices, and production technology. However, the use of information about the lead content of raw materials and about energy can increase the accuracy of the estimation. Finally, the emissions from at least the major sources, such as large power plants, smelters, steel and iron plants, and cement kilns should be measured. The mining industry and the lead-acid battery industry were not considered in the present study due to a lack of activity data. To obtain better and more reliable estimates of lead emissions, long-term field testing and continuous monitoring of all types of combustion facilities and technology in China warrant further investigation (Tian et al., 2011). 5. Conclusions Detailed estimates of China’s lead emissions from different sources by region from 1990 to 2009 were presented in this study. A substantial decrease in lead emissions occurred at the beginning of 21st century. The principal causes of this decrease were a reduction of the lead content of motor vehicle gasoline and a cutback in coal consumption in the industrial and residential sectors. However, the downward trend did not persist, and the emissions increased gradually during the following years. Motor vehicle gasoline combustion was the largest source of emissions from 1990 through 2009. After leaded gasoline was phased out, coal combustion became the principal source of emissions due to the country’s substantial production activities. Based on data on emissions from 2005 through 2009, Shandong and Hebei are the provinces with the largest amounts of emissions in China. The emissions are concentrated in eastern and central China due to the high level of coal consumption and non-ferrous metal smelting. The results of the present study can be used in atmospheric models of lead pollution to analyze deposition in the atmosphere and environmental concentrations. The findings also furnish important information for assessing the health effects of blood lead levels in the population. These lead levels will be considered in future research on environmental health risk assessment. Acknowledgments This research work was funded by the National Natural Science Foundation of China (key project 40930740 and general project 41171384) and Special Environmental Research Funds for Public Welfare (No. 201009046 and No. 201109064). Appendix A. Supplementary information Supplementary data related to this article can be found online at http://dx.doi.org/10.1016/j.atmosenv.2012.06.025. References Bai, X.F., Li, W.H., Chen, Y.F., Jiang, Y., 2007. The general distributions of trace elements in Chinese coals (In Chinese with abstract in English). Coal Quality Technology 1, 1e4. Biggins, P.D.E., Harrison, R.M., 1979. Atmospheric chemistry of automotive lead. Environmental Science & Technology 13 (5), 558e565. China Automotive Technology and Research Center (CATARC), 2009. China Automotive Industry Yearbook. China Automotive Industry Yearbook House, 613 pp. Chen, J.M., Tan, M.G., Li, Y.L., et al., 2005. A lead isotope record of shanghai atmospheric lead emissions in total suspended particles during the period of phasing out of leaded gasoline. Atmospheric Environment 39 (7), 1245e1253.
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