Local Coal Combustion Research Articles

Physicochemical Characterization and Oxidative Potential of Iron-Containing Particles Emitted from Xuanwei Coal Combustion.

Respiratory diseases have been proven to be directly related to air pollutants. Xuanwei, located in South China, has been known to have the highest mortality rate for lung cancer in China because of the air pollutants emitted through local coal combustion. However, the mechanism of lung cancer induced by air pollutants is not clear. Based on the fact that a large number of iron-bearing mineral particles was found in Xuanwei coal combustion particles, the iron-containing particles were hypothesized to play important roles in the pathogenesis of the high incidence rate of lung cancer in this area. In this study, raw coal samples were collected from a coal mine in the Xuanwei area. Size-resolved particles emitted from the raw coal samples were collected using an Anderson high-volume sampler. Mineralogical characterization and an assessment of the oxidative potential of the iron-containing particles were conducted using cutting-edge technologies, and the biological activity of the particles were evaluated via DTT assay. Our data showed that the iron-containing minerals accounted for more than 10% of the measured particles emitted from Xuanwei coal combustion samples. The content analysis of ·OH generated from Xuanwei coal combustion particles showed that ·OH content was dependent on the size of particles in the surrogated lung fluid. The concentration of ·OH increased as the particle size decreased. The DTT assay data further demonstrated that when the mass concentration of dissolved irons increased, the oxidation potential of the particles increased. The highest proportion of divalent iron in the total dissolved iron was found in the submicron particles in low pH solution(pH = 1), which indicated that the oxidative potential induced by submicron particles was stronger than that induced by coarse particles and fine particles. Armed with the above data, the toxicological mechanism of the iron-containing mineral particles can be investigated further.

Influence of anthropogenic activities and loess dusts on the rainwater hydrochemistry in the Chinese Loess Plateau

Rainwater hydrochemistry is an important indicator for tracing anthropogenic input on air quality. As the fastest economically developing city in the northwestern China and the Chinese Loess Plateau, rainwater chemistry, sources of dissolved solutes, and the influence of loess dust on rainwater chemistry in Xi'an city is unclear. Inorganic ions, δD and δ18O of two years' rainwater samples were measured to decipher the above issues. Rainwater samples were weakly alkaline (pH = 7.2) with the mean total dissolved solids (TDS) values of 43 mg/L. NH4+ and Ca2+ dominated in the cations and SO42− and NO3− dominated in the anions. The wet deposition of sulfur (S) and nitrogen (N) was 70.9 ± 67 mg·(m2·month)−1 and 244.8 ± 270.9 mg·(m2·month)−1, respectively. The meteoric water line in Xi'an was δD = 7.29δ18O+3.72 (R2 = 0.99). δD, δ18O, and d-excess analysis indicated the influence of evaporation on the dissolved solutes in rainwater, especially in the dry season. Rainwater acidity in the Xi'an city was mainly neutralized by Ca2+ and NH4+, and the neutralization ability in Xi'an city is higher than the southern China cities. Correlation analysis (CA), positive matrix factorization (PMF), and the backward air masses trajectory model identified high NH4+ and Ca2+ in rainwater were mainly originated from local agricultural activities and loess dust, while NO3− and SO42− were associated with local coal combustion and vehicle exhaust sources. High inputs of dusts and coal combustion in spring and winter resulted in elevated values of pH and major ions in Xi'an. Due to the air pollution control policy, air quality in Xi'an is getting better in recent years. Our study highlights the influence of anthropogenic activities and loess dusts on the rainwater hydrochemistry in Xi'an and provides important dataset for air pollution control for other cities in semi-arid and arid regions.

Selenite and selenate in clouds at a high-altitude mountain location in central Japan

The atmosphere is a temporal reservoir of selenium (Se). Understanding the chemical reactions and speciation of Se in primary emissions is crucial because atmospheric deposition is an important source of both Se contamination and micronutrients for terrestrial (agricultural) systems. In this study, the concentrations of selenite and selenate in acid cloud water (pH 4.3 average), including non-precipitating and precipitating clouds, were analyzed at a site near the summit of Mt. Norikura (2770 m a.s.l.), central Japan. The soluble Se in cloud water has a positive correlation with that of non-sea-salt sulfate, implying that the Se was incorporated in ammonium sulfate. The ammonium sulfate was generated from fossil fuel combustions in industrial and urban areas of southwest Japan and China. The concentrations of selenite and selenate in cloud water gradually decreased with a rise in acidity (pH) in approximately the same proportion. The coexistence of selenite and selenate perhaps indicates an oxidation-reduction equilibrium for the HSeO3−–SeO42− couple. For the precipitating cloud water, the selenite was the dominant species in all cloud events. This may be attributed to scavenging of local coal-combustion aerosols from southwest Japan by the rain droplets (washout). The selenite/selenate ratios of clouds as well as precipitating clouds were not correlated with gaseous O3 concentrations and remained stable throughout both day and night. In addition, laboratory experiments with Se–hydrogen peroxide (H2O2) solutions mimicking the cloud water conditions indicated that selenious acids (HSeO3−) cannot be oxidized with H2O2. The observational and experimental results suggest that the Se oxidation states in acid clouds are not caused by oxidation by the possible oxidants for SO2 such as H2O2 and O3.

RECENT PROGRESS IN ATMOSPHERIC FOSSIL FUEL CO2 TRENDS TRACED BY RADIOCARBON IN CHINA

ABSTRACTIt is important to know how much of the increased atmospheric CO2 is derived from fossil fuel emissions. Here, we review the progress in atmospheric fossil fuel CO2 (CO2ff) tracing over recent years by measurement of Δ14C in Chinese cities. In this paper we make progress by expanding the analysis from some locations to more regional views, by combining observations with modeling, and by making a preliminary comparison of observation-derived CO2ff with inventory-derived CO2ff. We have obtained a general picture of Chinese urban CO2ff and characteristics of its spatio-temporal variations at different scale, and identified the corresponding influencing factors. Interestingly, we found that the weekend effect of CO2ff was less evident in Chinese cities. In addition, we observed simultaneous variations in CO2ff and PM2.5 in a winter haze event in Beijing and a simultaneous decrease in annual averages of CO2ff and PM2.5 in Xi’an based on multi-year (2011–2016) Δ14CO2 monitoring. We found that local coal combustion was the main source of CO2ff in Xi’an, which is located in the Guanzhong basin, by applying a WRF-Chem model and looking at δ13C signatures. Thus, reduction of coal consumption is a crucial target for carbon emissions reduction in China.

Source apportionment of PM2.5 and its optical properties during a regional haze episode over north China plain

Based on the data of air pollutants in a typical regional haze pollution episode over North China Plain (NCP) in November 2018, Positive matrix factorization (PMF), potential source contribution function (PSCF) and concentration-weighted trajectory (CWT) models were used to analyze the sources and affecting areas of PM2.5 under different development stages. The whole observation period was divided into 6 segments (clean days, fog process, haze process including three stages of I: accumulation, II: growth, III: explosion, and dry haze process) according to PM2.5 concentration, visibility and relative humidity (RH). The dominant source in clean days was soil dust, with contribution percentage of 30.0%. The contributions of coal combustion and secondary nitrate increased with the development of haze pollution, while those of photochemical product, soil dust and secondary sulfate decreased. Coal combustion contributed the most in stage III (35.8%), indicating that the local coal combustion emission was the main reason for the rapid explosion of pollutants. The contribution of vehicular emission was 16.7%, 30.1% and 12.8% in stage I, II, and III, respectively, which was 2.1, 3.8, and 1.6 times that on clean days, presenting significant regional distribution characteristics. The significant local contribution and short-range transport were the major sources of haze pollution episodes in NCP, and Xianghe will bring pollutants to its northeast and southwest directions in the future. (NH4)2SO4, NH4NO3, and organic matter (OM) were the major components of aerosol extinction coefficient (bext) under all development stages, together accounting for 59.5%–78.6%. With the development of haze process, the contribution of (NH4)2SO4 to bext decreased, while that of NH4NO3 increased.

Spatial-temporal variability of aerosol sources based on chemical composition and particle number size distributions in an urban settlement influenced by metallurgical industry.

The Moravian-Silesian region of the Czech Republic with its capital city Ostrava is a European air pollution hot spot for airborne particulate matter (PM). Therefore, the spatiotemporal variability assessment of source contributions to aerosol particles is essential for the successful abatement strategies implementation. Positive Matrix Factorization (PMF) was applied to highly-time resolved PM0.15-1.15 chemical composition (1h resolution) and particle number size distribution (PNSD, 14nm - 10μm) data measured at the suburban (Ostrava-Plesná) and urban (Ostrava-Radvanice) residential receptor sites in parallel during an intensive winter campaign. Diel patterns, meteorological variables, inorganic and organic markers, and associations between the chemical composition factors and PNSD factors were used to identify the pollution sources and their origins (local, urban agglomeration and regional). The source apportionment analysis resolved six and four PM0.15-1.15 sources in Plesná and Radvanice, respectively. In Plesná, local residential combustion sources (coal and biomass combustion) followed by regional combustion sources (residential heating, metallurgical industry) were the main contributors to PM0.15-1.15. In Radvanice, local residential combustion and the metallurgical industry were the most important PM0.15-1.15 sources. Aitken and accumulation mode particles emitted by local residential combustion sources along with common urban sources (residential heating, industry and traffic) were the main contributors to the particle number concentration (PNC) in Plesná. Additionally, accumulation mode particles from local residential combustion sources and regional pollution dominated the particle volume concentration (PVC). In Radvanice, local industrial sources were the major contributors to PNC and local coal combustion was the main contributor to PVC. The source apportionment results from the complementary datasets elucidated the relevance of highly time-resolved parallel measurements at both receptor sites given the specific meteorological conditions produced by the regional orography. These results are in agreement with our previous studies conducted at this site. Graphical abstract.

Impact of anthropogenic sulfate deposition via precipitation on carbonate weathering in a typical industrial city in a karst basin of southwest China: A case study in Liuzhou

An analysis was performed of the hydrochemical characteristics of precipitation and river water samples collected from the Liujiang River Basin from June 2014 to May 2015, SW China to determine the carbon source and sink of carbonate weathering by anthropogenic sulfate deposition via precipitation in a typical Karst industrial city. Our findings revealed that (1) the pH of the precipitation samples has a volume-weighted mean (VWM) of 5.78 and that the acid rain rate is 12%. The enrichment factor (EF), sea salt fraction (SSF), crustal fraction (CF) and anthropogenic fraction (AF) were calculated, and the results indicated that precipitation was characterized by high concentrations of SO4, NH4, Ca and NO3. Na and Cl, Ca and NH4, and SO4 (98.2%) and NO3 (99.8%) were mainly derived from sea salt, earth crust, and anthropogenic activities, respectively. Combined with the air mass trajectory (HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory)) and the concentration of non-sea salt (NSS) SO4 and δ34S–SO4nss, the δ34S–SO4sam ranged from −2.6–12.6‰ and atmospheric sulfate was mainly associated with local coal combustion, fossil fuels and the transmission distance of pollution sources from the northwest and southwest in the interior of the continents. (2) An analysis of the river hydrochemical characteristics showed that the cations are mainly Ca and Mg, and they accounted for approximately 90% of the total cations. The anions were mainly HCO3 and SO4, and the hydrochemical composition of the river was mainly controlled by the weathering of carbonate minerals in the river basin. An analysis of the correlation between the changes in the chemical equivalence concentration of [Ca + Mg]/[HCO3+SO4] showed that the ratio of most river water samples was approximately 1, indicating that Ca and Mg in the river need HCO3 and SO4 for chemical equilibrium and that SO4 in the river may be involved in the dissolution of carbonate minerals. (3) Corrections were performed based on the chloride-normalized ratios and the contribution of each terminal element was calculated to estimate the major ions of precipitation input; the results showed that the average contribution ratio of SO4 transported to the river by anthropogenic sulfuric acid in precipitation reached 85.57%. (4) According to the proportional relationships, carbonate weathering accounts for 31.73% of the anthropogenic sulfuric acid via precipitation and would cause an approximate 6.27% increase in carbonate weathering rates but a 19.48% decrease in CO2 consumption rates. Taken together, our results revealed that even in high-carbonate areas of Southwest China, chemical weathering by sulfuric acid can reduce the carbon sink effect caused by carbonate weathering.

High-time-resolution source apportionment of PM<sub>2.5</sub> in Beijing with multiple models

Abstract. Beijing has suffered from heavy local emissions as well as regional transport of air pollutants, resulting in severe atmospheric fine-particle (PM2.5) pollution. This study developed a combined method to investigate source types of PM2.5 and its source regions during winter 2016 in Beijing, which include the receptor model (positive matrix factorization, PMF), footprint and an air quality model. The PMF model was performed with high-time-resolution measurements of trace elements, water soluble ions, organic carbon and elemental carbon using online instruments during the wintertime campaign of the Air Pollution and Human Health in a Chinese Megacity – Beijing (APHH-Beijing) program in 2016. Source types and their contributions estimated by PMF model using online measurements were linked with source regions identified by the footprint model, and the regional transport contribution was estimated by an air quality model (the Nested Air Quality Prediction Model System, NAQPMS) to analyze the specific sources and source regions during haze episodes. Our results show that secondary and biomass-burning sources were dominated by regional transport, while the coal combustion source increased with local contribution, suggesting that strict control strategies for local coal combustion in Beijing and a reduction of biomass-burning and gaseous precursor emissions in surrounding areas were essential to improve air quality in Beijing. The combination of PMF with footprint results revealed that secondary sources were mainly associated with southern footprints (53 %). The northern footprint was characterized by a high dust source contribution (11 %), while industrial sources increased with the eastern footprint (10 %). The results demonstrated the power of combining receptor model-based source apportionment with other models in understanding the formation of haze episodes and identifying specific sources from different source regions affecting air quality in Beijing.

Sulfur Sources and Oxidation Pathways in Summer Aerosols from Nanjing Northern Suburbs Using S and O Isotopes

The sulfur and oxygen isotopic compositions of sulfate in PM2.5 were determined by EA-IRMS to study the sulfur sources and oxidation formation pathways of sulfates in PM2.5 from Nanjing northern suburbs during July 2014. The results indicated that δ34 S values of sulfate ranged from 1.7‰ to 4.8‰ with an average of 3.2‰±1.0‰, while δ18O values ranged from 7.5‰ to 12.9‰ with an average of 9.3‰±1.7‰. Comparing the δ34 S values of aerosol sulfate and potential pollution sources, we concluded that the sulfur source of PM2.5 was mainly local coal combustion and vehicle exhaust. In addition, the secondary sulfate was dominant in PM2.5, and 59.3% of the formation of the secondary sulfate was caused by SO2 homogeneous oxidation. In addition, the heterogeneous oxidation of SO2 in the atmosphere was dominated by ferrous iron oxidation in excess O2. The main mechanisms of homogeneous oxidation include oxidation in the presence of electric discharge (presumably forming O3) and NO2.

Comparison of Submicron Particles at a Rural and an Urban Site in the North China Plain during the December 2016 Heavy Pollution Episodes

An extensive field experiment for measurement of physical and chemical properties of aerosols was conducted at an urban site in the Chinese Academy of Meteorological Sciences (CAMS) in Beijing and at a rural site in Gucheng (GC), Hebei Province in December 2016. This paper compares the number size distribution of submicron particle matter (PM1, diameter < 1 μm) between the two sites. The results show that the mean PM1 number concentration at GC was twice that at CAMS, and the mass concentration was three times the amount at CAMS. It is found that the accumulation mode (100–850 nm) particles constituted the largest fraction of PM1 at GC, which was significantly correlated with the local coal combustion, as confirmed by a significant relationship between the accumulation mode and the absorption coefficient of soot particles. The high PM1 concentration at GC prevented the occurrence of new particle formation (NPF) events, while eight such events were observed at CAMS. During the NPF events, the mass fraction of sulfate increased significantly, indicating that sulfate played an important role in NPF. The contribution of regional transport to PM1 mass concentration was approximately 50% at both sites, same as that of the local emission. However, during the red-alert period when emission control took place, the contribution of regional transport was notably higher.

On the source contribution to Beijing PM2.5 concentrations

Beijing is a city with some of the world's worst particulate air pollution. Although there have been various control strategies implemented since 1998, there are still episodes of PM2.5 concentrations of hundreds of micrograms per cubic meter. In this study, samples were collected over a year in Beijing, chemically characterized, and the resulting data analyzed for source apportionment. The new error analysis capabilities built into EPA PMF V5.0 have been employed to better evaluate the profiles and assign them to source types. Secondary sulfate, local coal combustion and secondary nitrate were the major contributors to the PM2.5 mass. However, in this study, traffic was found to be more important as a PM compared to prior studies. It was actually the largest PM2.5 source in autumn and winter although local coal combustion is also a large source of PM in the winter months. These results demonstrate the value of using the displacement method to assess the variability in source profiles to improve our interpretation of PMF results. They also suggest more attention needs to be paid to traffic emissions in Beijing.

Atmospheric lead in urban Guiyang, Southwest China: Isotopic source signatures

Total suspended particles (TSP) and their source-related samples from Guiyang, Southwest China, were collected and analyzed for their lead (Pb) concentrations and Pb isotopic compositions, to identify the sources of atmosphere lead in urban Guiyang. Coals from Guizhou Province had significantly high radiogenic Pb, different to those from North China. Local vehicle exhaust had similar Pb isotope ratios to those of other areas in China. Pb isotopic compositions of atmospheric aerosols, rainwaters, plant samples, and acid-soluble fraction of street dusts were similar to each other. The results clearly suggest that the Pb–Zn ore-related industrial emission, and/or vehicle exhaust, rather than the local coal combustion, are the main sources of atmospheric Pb in Guiyang. Furthermore, binary mixing model indicates that the contribution of coal combustion to the local atmospheric Pb decreased from about 40% in 1988 to about 10% in 2013.

General trends of atmospheric mercury concentrations in urban and rural areas in Korea and characteristics of high-concentration events

Long-term measurement of speciated Hg concentrations is the first step toward identifying the seasonal and spatial characteristics of Hg concentrations; however, atmospheric Hg research is scarce in Korea. In this study, total gaseous mercury (TGM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were measured in urban (Seoul) and rural (Chuncheon) areas over a more than 3 year period in order to improve the understanding of speciated Hg transport. The mean concentrations of TGM, GOM and PBM were 3.72 ± 2.96 (0.19–149.84) ng m−3, 11.3 ± 9.5 (0.9–57.3) pg m−3, and 13.4 ± 12.0 (2.1–64.3) pg m−3 at the Seoul site and 2.12 ± 1.47 (0.26–10.75) ng m−3, 2.7 ± 2.7 (0.1–16.9) pg m−3, and 3.7 ± 5.7 (0.1–30.0) pg m−3 in Chuncheon. Both long-range transport and local sources caused high TGM concentration events, while local coal combustion was a main cause of enhancing the GOM and PBM concentrations in Seoul. However, there was no correlation between the pollutants emitted from coal combustion and the speciated Hg concentration in Chuncheon, indicating that other mechanisms were involved in the Hg increase. We found a positive correlation between the GOM and the O3 concentrations and a negative correlation between the GEM and the GOM concentrations, especially on foggy days, suggesting that the oxidation of GEM was an important source for GOM in Chuncheon. In addition, the ratio of PBM/GOM was inversely proportional to the atmospheric temperature and directly proportional to the relative humidity, which suggests that the in-situ formation of PBM through gas-particle partitioning of GOM was important in rural areas.

Field evaluation of a near–real time elemental monitor and identification of element sources observed at an air monitoring supersite in Korea

Ambient measurements of elemental species concentrations were made using an online elemental monitor at an air pollution monitoring station in Gwangju, Korea to evaluate the performance of the monitor for near–real time PM2.5 elemental monitoring and identify possible sources of the observed elements. This study also demonstrates the utility of integrating hourly elemental data with the meteorological data to better understand the sources of elements. Good agreement between the online and filter–based measurements was obtained for the elements studied, with an R2 of 0.73–0.97 and regression slopes of 0.84–2.37, suggesting the potential use of the online monitor to observe temporal variations in anthropogenic aerosol particles. Atmospheric element concentration levels studied were 2–20 times greater than their background levels when pollution plumes coming from industrial areas had impacted the site. Examination of the elements data revealed several short spikes of elements that are associated with local industrial emissions and road dusts. For the haze episodes observed over the study period, the element K was significantly influenced by biomass burning emissions with some impacts from soil dusts and industrial activities. Based on the wind direction and wind speed data, As/Se, Se/SO42−, and correlations among Se, As, Pb, SO2, and SO42−, it is suggested that the observed As and Se were significantly impacted by local anthropogenic sources and long–range transport of aerosols, rather than local coal combustion or coke emissions. Conditional probability functions were applied to identify likely local emission source locations of the elements observed at the site, indicating that the elements contributions were from the southwest and northeast directions, where two industrial areas and an express highway are located. Results from principal component analysis indicate that the observed concentrations of the element species were likely attributed to road dust/local industrial emissions, oil combustion, and metal processing.

Physicochemical properties and ability to generate free radicals of ambient coarse, fine, and ultrafine particles in the atmosphere of Xuanwei, China, an area of high lung cancer incidence

The link between the high incidence of lung cancer and harmful pollutants emitted by local coal combustion in Xuanwei, Yunnan province, China, has been a focus of study since the 1980s. However, the mechanisms responsible for the high lung cancer rate remain unclear, necessitating further study. Since a close relationship between ambient air particle pollution and respiratory diseases exists, we sampled size-resolved ambient particles from the atmosphere of Xuanwei. In our indoor experiment, cutting-edge methods, including scanning electron microscopy coupled with energy dispersive X-ray detection (SEM/EDX), particle-induced X-ray emission (PIXE), electronic paramagnetic resonance (EPR) and the cell-free DCFH-DA assay, were employed to investigate the physicochemical properties, the potential to generate free radicals and the oxidative potential of ambient coarse (diameter, 1.8–10 μm), fine (diameter, 0.1–1.8 μm), and ultrafine (diameter, <0.1 μm) particles. We found the total mass concentrations of the size-resolved particles collected in spring were higher than that in early winter. Mass percentage of fine particles accounted for 68% and 61% of the total particulate mass in spring and in early winter samples, respectively, indicating that fine particles were the major component of the Xuanwei ambient particulate matters. On the other hand, the results of SEM/EDX analysis showed that the coarse particles were dominated by minerals, the fine particles by soot aggregates and fly ashes, and the ultrafine particles by soot particles and unidentified particles. Our PIXE results revealed that crustal elements (Ca, Ti Si, Fe) were mainly distributed in coarse particles, while trace metals (Cr, Mn, Ni, Cu, Zn, Pb) dominated in the fine particle fraction, and S, a typical element emitted by coal combustion, mainly resided in fine particles collected from the winter atmosphere. EPR results indicated that the magnitude of free radical intensity caused by size-resolved particles followed these patterns: fine particles > coarse particles > ultrafine particles for spring samples and ultrafine particles > fine particles > coarse particles for winter samples. Cell-free DCFH assay results conclusively showed that all of the measured particle suspensions displayed a higher oxidative potential than the negative control. The correlation coefficient (R2) between free radical intensity and fluorescent intensity generated by the size-resolved particles was 0.535 and 0.507 for the spring and winter seasons, respectively, implying that ambient air particles in the Xuanwei atmosphere have the ability to generate free radicals, and fine and ultrafine particles could be hazardous to local residents.

Investigation of Local Mercury Deposition from a Coal-Fired Power Plant Using Mercury Isotopes

Coal combustion accounts for approximately two-thirds of global anthropogenic mercury (Hg) emissions. Enhanced deposition of Hg can occur close to coal-fired utility boilers (CFUBs), but it is difficult to link specific point sources with local deposition. Measurement of Hg stable isotope ratios in precipitation holds promise as a tool to assist in the identification of local Hg deposition related to anthropogenic emissions. We collected daily event precipitation samples in close proximity to a large CFUB in Crystal River, Florida. Precipitation samples collected in Crystal River were isotopically distinct and displayed large negative δ(202)Hg values (mean = -2.56‰, 1 SD = 1.10‰, n = 28). In contrast, precipitation samples collected at other sites in FL that were not greatly impacted by local coal combustion were characterized by δ(202)Hg values close to 0‰ (mean = 0.07‰, 1 SD = 0.17‰, n = 13). These results indicate that, depending on factors such as powdered coal isotopic composition and efficiency of Hg removal from flue gas, Hg deposited near CFUBs can be isotopically distinct. As this tool is further refined through future studies, Hg stable isotopes may eventually be used to quantify local deposition of Hg emitted by large CFUBs.

Evaluation of ecological risk and source of heavy metals in vegetable-growing soils in Fujian province, China

Heavy metal pollution in vegetable-growing soils is of increasing concern due to the potential health risk via food chain. The present study aimed at assessing the potential ecological risk (RI) of heavy metals (HMs) in the vegetable-growing soils collected from Fujian Province, China, and identifying the potential sources with multivariable methods including correlation matrix and principal component analysis (PCA). The concentrations of HMs including Pb, Cd, Hg, Cr, As, Cu, Zn, and Ni in 160 soils collected from 25 sites of vegetable-growing land in Fujian Province, China, are measured with inductively coupled plasma mass spectrometry and hydrogen generation-atomic fluorescence spectrometer, respectively. Results show that most of the soil samples have been seriously contaminated with HMs, especially the metals of Hg, Cd, and Pb, compared with both of the background values of soils in Fujian Province and the limitation of total HMs in soil environmental quality for edible agricultural products set in China (HJ 332-2006). The indexes of RI indicate that only 8% of the 25 sites are environmentally safe, whereas according to the present study 28% of the sampling sites are heavily contaminated with HMs with 628–1,076 of the RI values. Based on PCA analysis, Zn, Cd, and Pb associated with PC1 are found to derive from anthropogenic sources, especially the local industrial activities, such as porcelain plants in Dehua, zinc metallurgical plants in Nan’an, and sewage irrigation from industrial estate in Taijiang. The concentrations of As, Ni, and Cu loaded in PC2 are found to be mainly controlled by natural factors (i.e., the lithogenic process of natural parent soils). Hg in PC3 is also found to originate from the anthropogenic sources, such as local coal combustion in Longhai and industrial activities in Cangshan. However, Cr in PC3 is mainly derived from the lithogenic sources.

Stable sulphur and nitrogen isotopes of the moss Haplocladium microphyllum at urban, rural and forested sites

Elemental (S and N) and isotopic ( δ 34S and δ 15N) contents in the moss Haplocladium microphyllum at urban, rural and forested sites in acid rain area of South China have been analyzed for comparisons to show whether they are different and can be effectively used to identify S and N sources of atmospheric deposition. Average moss S content at rural sites (0.29 ± 0.06%) was found to be in between those at urban (0.35 ± 0.05%) and forested (0.25 ± 0.04%) sites, which are significantly different. Average N contents of urban (2.60 ± 0.56%) and rural mosses (2.84 ± 0.77%) are not significantly different, while both are significantly different to that of forested mosses at most areas, indicating that the atmosphere over rural sites has been polluted by N as seriously as that over urban sites. Nitrogen supply, relative to S supply, was in excess of the requirement for protein synthesis, especially at rural and forested sites. Moss stable isotope signatures have been proven to be effective tools for deciphering atmospheric S and N sources at these sites. Through moss δ 34S signatures, we found that atmospheric S at urban and forested sites was mainly from local coal combustion and domestic biomass burning, respectively, whereas northerly air masses contributed more S to forested sites. The relatively negative moss δ 15N values (−7.5 ± 3.0, −3.4 ± 2.1 and −0.8 ± 2.1‰) demonstrated that the main form in the N deposition was NH x in these sites. More negative δ 15N signatures in urban mosses (−7.5 ± 3.0‰) indicated the contribution of NH 3 released from untreated city sewage and wastes, while relatively less negative δ 15N for rural and forested mosses (3.4 ± 2.1 and −0.8 ± 2.1‰) was largely derived from agricultural NH 3.

Elemental carbon in urban soils and road dusts in Xi'an, China and its implication for air pollution

Increasing evidence confirms that elemental carbon (EC) is not only a light-absorbing constituent that warms the atmosphere but also a significant environmental pollutant. Investigations were conducted to identify carbonaceous pollution signatures in road dusts and urban soils and to evaluate potential sources in Xi'an. Average concentrations of EC, char-EC, and soot-EC in soils were 0.90, 0.51, and 0.39 mg g −1, respectively, a little higher than or comparable to prior studies on the Loess Plateau. Vertical profiles in soils revealed soot-EC concentrations from pre-industrialized samples close to ∼0.20 mg g −1, while EC and char-EC varied widely, with no distinct pattern. Enrichment factor analysis indicated that EC, char-EC, and soot-EC in road dusts were all elevated by an order of magnitude. The spatial distribution of total EC, char-EC, and soot-EC in road dusts revealed close correspondence with human activities such as coal combustion and vehicle emissions. The average char-EC/soot-EC ratio was 1.66 for road dusts, suggesting that the main sources of carbonaceous particles are local coal combustion and vehicle emissions. The study demonstrated that EC, char-EC, and soot-EC levels in road dusts are effective indicators of anthropogenic pollution.

PM source apportionment and trace metallic aerosol affinities during atmospheric pollution episodes: a case study from Puertollano, Spain

Source apportionment study was performed, applying principal component analysis to the results of 221 chemical analyses of PM10 and PM2.5 samples collected daily from the industrial (but low traffic) Spanish town of Puertollano over a 14-month period during 2004-2005. Results reveal compositional variations attributable to different mixtures of natural and anthropogenic materials, mainly soil and rock dust (crustal), marine salt (only in PM10), petrochemical refinery emissions, and particles attributed to the combustion of local coal, which is unusually rich in Pb and Sb. During the study period there were 34 pollution episodes when PM10 exceeded 50 tg m(-3), mostly due to winter air temperature inversions, regional atmospheric stagnation, or African dust incursions (North African, NAF days: usually in summer). Whereas the crustal component during NAF episodes averaged 52% with a PM2.5/PM10 ratio of 0.54, this dropped to 29% and a PM2.5/PM10 of 0.67 during non-NAF days when anthropogenic materials predominated. Abnormally enhanced concentrations of pathfinder metallic trace elements provide additional evidence for source apportionment: thus aerosols with raised levels of Pb and Sb are associated with local coal combustion, Ni and V can be linked to petrochemical PM emissions, and Ti, Mn, Rb, and Ce are particularly characteristic of crustal dust incursions.