Contamination, ecological-health risks, and sources of potentially toxic elements in road-dust sediments and soils of the largest urban riverfront scenic park in China.

Identifying the contamination and sources of potentially toxic elements (PTEs) in road-dust sediment (RDS) and the surrounding greenspace soil of urban environments and understanding their ecological-health risks are important for pollution management and public health. The contamination characteristics, ecological and probabilistic health risks, and source apportionment of eight PTEs (Cd, Pb, Cr, Cu, Ni, As, Zn, and Hg) in the Yellow River Custom Tourist Line of Lanzhou, which is the largest open urban riverfront scenic park in China, were investigated. The results showed that all the RDS PTE mean concentrations exceeded their soil background values, whereas for the surrounding greenspace soils, the concentrations of the PTEs, except for Cr and Ni, were also higher than their local background levels. Moreover, the RDS-soil system was mainly contaminated by Cd, Zn, Pb, Cu, and Hg to varying degrees, and the integrated ecological risks of PTEs in the RDS and soil were high and considerable at most sites, respectively. The probabilistic health risk assessment results demonstrated that the non-carcinogenic hazard risk for humans was negligible, but the total carcinogenic risks should be considered. Source apportionment using a positive matrix factorization model combined with multivariate statistical analyses revealed that Cr, Ni, and As in the RDS-soil system were from natural and industrial sources, Cd, Pb, Zn, Cu came from vehicle emissions and pesticide and fertilizer applications, and Hg was from natural and industrial sources and utilization of pesticides with fertilizers. This work provides scientific evidence for urban planning and human health protection in urban environments.

[Pollution Characteristics and Risk Assessment of Heavy Metals in Surface Dusts and Surrounding Green Land Soils from Yellow River Custom Tourist Line in Lanzhou].

In order to investigate the contamination levels of dust and its surrounding green land soil heavy metal pollution and potential ecological and health risks in the scenic areas of urban waterfront parks, the gardens, squares, and theme parks of the Yellow River Custom Tourist Line in Lanzhou were selected as the research area, using 27 dust samples and 26 soil samples from its surrounding green lands. The contamination characteristics and potential ecological risks of eight heavy metals (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) were evaluated using the geo-accumulation index (Igeo), single-factor pollution index (Pi), Nemerow integrated pollution index (PN), and improved potential ecological risk index (RI). The human health risk assessment was also evaluated using the exposure risk model. The results showed that the average concentrations of the other heavy metals in the surface dusts were higher than the background values of Gansu Province and Lanzhou City, except that the As mean concentrations in the surface dusts and the surrounding green land soils were slightly lower than the Gansu Province background values. For its surrounding green land soils, the mean concentrations of the other heavy metals (Cu, Zn, Cd, Hg, and Pb) exceeded the soil background values of Gansu Province and Lanzhou City, whereas the Cr and Ni mean concentrations were lower than their corresponding soil background values of Gansu Province and Lanzhou City. The geo-accumulation and single-factor pollution indices demonstrated that a slight to moderate pollution of Cr, Cu, Zn, Cd, Hg, and Pb occurred in surface dusts, and Cu, Zn, Cd, Hg, and Pb appeared in varying degrees of contamination levels in its surrounding green land soils. The Nemerow integrated pollution index analysis manifested that the overall contamination status of the study areas was between slightly and heavily polluted. The potential ecological risk index suggested that Cd and Hg were recognized as significant pollutant elements and that the RI of the other heavy metals were all below 40, presenting slight ecological risk. The health risk assessment indicated that ingestion was the dominant exposure pathway for heavy metals from the surface dusts and the surrounding green land soils, and no carcinogenic and noncarcinogenic risks posed threats to adults and children.

[Spatial Distribution Characteristics and Source Analysis of Heavy Metals in Urban River Surface Sediments from the Lanzhou Reach of the Yellow River].

In order to investigate the contamination characteristics and potential sources of heavy metals from the urban river surface sediments in the Yellow River Basin, we selected the Lanzhou reach of the Yellow River as the object of investigation. A total of 46 surface sediment samples were collected along the Lanzhou reach of the Yellow River, and the contents of eight heavy metals, Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb, were determined by using inductively coupled plasma mass spectrometry and an atomic fluorescence spectrometer. Contamination indexes including single factor pollution index (Pi) and geo-accumulation index (Igeo), together with the sediment pollution index (SPI), were used to assess heavy metal pollution characteristics and ecological risk levels in the urban river surface sediments of the Lanzhou reach of the Yellow River. Pearson's correlation analysis (CA), positive matrix factorization (PMF), and principal component analysis/absolute principal component score (PCA/APCS) were jointly employed to quantitatively analyze pollution sources of heavy metals. The results showed that the mean concentrations of the majority of heavy metals exceeded their corresponding background values of Gansu Province and Lanzhou City with the exception of As, and the spatial distribution of high concentrations of heavy metals was mainly concentrated in the corner of the river. Based on the single factor pollution and geo-accumulation indexes of the eight heavy metals, in the Lanzhou reach of the Yellow River, Cr was the dominant pollution element in the urban river surface sediments, followed by Cd and Ni. Additionally, the SPI values for the eight heavy metals in the surface sediments ranged from 0.48 to 8.56, presenting natural to low ecological risk level. Furthermore, source apportionment revealed that a mixture source of industrial and agricultural activities (77.6%) was the largest contributor of Cr, Ni, Zn, As, Cd, and Pb in the urban river surface sediments, followed by natural sources (11.4%) and a mixed source of industrial and traffic activities (11%).

Influence on the levels of PAHs and methylated PAHs in surface soil from pollution control in China: Evidence in 2019 data compared with 2005 and 2012 data.

To comprehensively clarify the pollution characteristics of persistent toxic substances, the Soil and Air Monitoring Program Phase III (SAMP-III) was conducted in 2019 in China. In total, 154 surface soil samples were collected across China, and 30 unsubstituted polycyclic aromatic hydrocarbons (U-PAHs) and 49 methylated PAHs (Me-PAHs) were analyzed in this study. The mean concentrations of total U-PAHs and Me-PAHs were 540 ± 778 and 82.0 ± 132 ng/g dw, respectively. Northeastern China and Eastern China are the two regions of concern with high PAH and BaP equivalency levels. Compared with SAMP-I (2005) and SAMP-II (2012), an obvious upward temporal trend followed by a downward trend of PAH levels was observed in the past 14 years for the first time. The mean concentrations of 16 U-PAHs were 377 ± 716, 780 ± 1010, and 419 ± 611 ng/g dw in surface soil across China for the three phases, respectively. Considering rapid economic growth and energy consumption, an increasing trend from 2005 to 2012 was expected. From 2012 to 2019, the PAH levels in soils across China decreased by 50 %, which was consistent with the decline in PAH emissions. The period of reduction of PAHs in surface soil coincided with the implementation of Air and Soil Pollution Control Actions in China after 2013 and 2016, respectively. Along with the pollution control actions in China, the pollution control of PAHs and the increase in soil quality can be expected in the near future.

The atmospheric lead emission, deposition, and environmental inequality driven by interprovincial trade in China.

Lead (Pb) as a hazardous air pollutant has raised widespread concerns due to its adverse and toxic effects on the ecological environment and human health. Here we integrated the multi-regional input-output (MRIO) model and an atmospheric transport model to examine regional environmental inequality (REI) index induced by Pb emission transfers, and to evaluate the impacts of interprovincial trade on regional atmospheric Pb concentrations and dry deposition fluxes in China in 2012. In 2012, approximately 57.4% ~ 72.6% of Pb emissions in well-developed eastern regions (Beijing-Tianjin, Yangtze River Delta (YRD)) and the southern seaboard of China were embodied in other regions in China subject to the demands from these well-developed regions to industrial products and services. Our results, based on the net virtual flows of Pb emission and value-added, indicate that most provinces in the eastern seaboard of China outsource Pb emission and benefit from the interprovincial trade by reducing their Pb emissions. REI indexes show that the well-developed Guangdong province outsources its Pb emission but has low economic gains. Many less-developed provinces in central China enhance virtual Pb emission inflow but have high economic gains. Whereas, inland provinces in western China not only experience Pb emission increase, but also suffer from indirect economic loss due to trade with well-developed provinces to meet their increasing demands to Pb emission abundant industrial products from these provinces in eastern China which are mostly provided by less-developed but energy and mineral product abundant provinces in western China. For example, the province pair with highest REI index was Jiangsu-Inner Mongolia (REI = 2.47), which revealed that Jiangsu was the largest beneficiary which exported 37.2 t of net Pb emission and gained value-added of 521.4 billion RMB through trade with Inner Mongolia which suffered from both virtual Pb inflow and economic loss in 2012. As a result of interprovincial trade, Pb dry deposition in central and eastern China was decreased but increased in western China. Overall, interprovincial trade reduced 17.6% of atmospheric Pb dry deposition in China.

[Gridded Emission Inventories of Major Criteria Air Pollutants and Source Contributions in Lan-Bai Metropolitan Area, Northwest China].

Lan-Bai Metropolitan Area in Gansu province is an important heavy-industry base with the highest level of total air pollutant emissions in Northwest China. It is significant to study the high-resolution pollutant emission inventory to forecast regional air quality and to simulate pollutant emission reduction, as well as provide early warnings and forecasts, and to control air pollution. Taking Lanzhou and Baiyin as the main research areas, this study established the gridded emission inventories of seven major criteria air pollutants in the Lan-Bai Metropolitan Area based on emission data and statistical yearbooks of 2015-2016. The spatial pollution characteristics and emission source contributions were also studied. The results showed that the total annual emissions of seven major criteria air pollutants in the Lan-Bai Metropolitan Area were as followings:NOx 2.22×105 t, NH3 4.53×104t, VOCs 7.74×104t, CO 5.62×105 t, PM10 4.95×105 t, PM2.5 1.91×105 t, and SO2 1.37×105 t. Among them, annual CO emissions were the highest, while the annual emissions of NH3 were the lowest. The comparison of this gridded emission inventories with the Peking and Tsinghua University's MEIC inventories, found that the consistency of the three inventories for traffic source was relatively high, but for the total emissions and industrial source emissions of CO, a 30%-40% difference was found when compared with emissions in the Peking and Tsinghua University's inventories. The main differences were from the collected emission factors and the different resolution and years for collected data. The industrial non-combustion process sources, accounting for the largest proportion, were mainly concentrated in urban areas for the other six major criteria air pollutants except for NH3. The main contributing sources of NH3 were from the use of nitrogen fertilizers and livestock emissions, so its spatial pollution distribution was mainly affected by farmland distribution and other factors. It can be concluded that countermeasures, such as controlling industrial non-combustion process sources, integrating high-quality and high-efficiency power supply, using clean energy, strict dust emission control on construction sites and industrial production facilities, as well as urban greening could effectively reduce the emissions of six major criteria air pollutants including NOx, VOCs, CO, PM10, PM2.5, and SO2 in the Lan-Bai Metropolitan Area. The reduction of NH3 emission mainly depends on reducing the use of nitrogen fertilizer and controlling livestock emissions in the rural regions of Lan-Bai Metropolitan Area. This paper also used Monte Carlo uncertainty analysis to evaluate uncertainty in the gridded emission inventories, in which the maximum uncertainty was -31%-30% for NH3, the uncertainty of CO at -18%-16% was minimal. Therefore, the overall credibility was high for the established gridded emission inventories in this study.

[Sources and Health Risks of Atmospheric Polychlorinated Biphenyls in an Urban/Industrial Areas, Northwest China].

A passive air sampler was used to monitor the concentration and contamination profile of 18 polychlorinated biphenyls (PCBs) in the atmosphere over the urban and industrial area of Gaolan, a city in northwest China, during the non-heating and heating seasons of 2018, and the sources, pollutant transport, and the health risks of PCB exposure were analyzed and assessed using principle component analysis, trajectory modeling, and inhalation exposure modeling. The atmospheric concentration in the study area ranged from 110.2 to 429.9 pg·m-3, and the highest average concentration was found at the industrial estate. Tetra-PCBs and penta-PCBs were the dominant homologue groups, and the percentage of tetra-PCBs increased in the heating season. Combustion and industrial thermal processes, PCB-containing electrical equipment, and the combined source of volatilization from paint, combustion, and industrial thermal processes were considered to be the main sources, and the source of combustion and industrial thermal processes contributed the largest proportion of PCBs at 40.8%. Largely, the emission of UP-PCBs would significantly influence PCB pollution in the study area. Trajectory analysis results illustrated that PCBs emitted from sources in the study area would be transmitted to Lanzhou City atmospherically; local pollution would be the main source of PCBs contamination in the study area during the non-heating season, while the atmospheric input of PCBs transmitted from the northwest region would be another source during the heating season. Health risk analysis showed that the non-cancer risk of PCBs exposure was low in all age groups; however, lifetime cancer risks exceeded 10-6. PCBs emitted from combustion and industrial thermal processes sources would have a strong impact on resident exposure to PCBs, and adverse health effects would be caused due to long-term inhalation exposure of the inhabitants to PCBs contamination in the study area.

[Atmospheric Pollution Characteristics and Inhalation Exposure Risk of Nitrated Polycyclic Aromatic Hydrocarbons in PM2.5 at the Ningdong Energy and Chemical Industry Base, Northwest China].

Atmospheric PM2.5 samples were collected by using the active sampling method to investigate the pollution characteristics of nitrated polycyclic aromatic hydrocarbons (NPAHs) at the Ningdong Energy and Chemical Industry Base, Northwest China. Furthermore, the primary sources and the contributions of secondary formation sources as well as the inhalation exposure risks were identified. The main results were as follows. The concentration levels of ∑12NPAHs in PM2.5 ranged from 2.06 ng·m-3 to 37.14 ng·m-3 at the Ningdong Energy and Chemical Industry Base. The average concentrations of ∑12NPAHs were (25.57±5.76) ng·m-3 in winter and (6.22±1.74) ng·m-3 in summer for the Baofeng sampling site associated with the energy industry. The average concentrations of ∑12NPAHs were (7.13±1.44) ng·m-3 in winter and (2.58±0.39) ng·m-3 in summer for the Yinglite sampling site associated with chemical and electricity industries. The levels of ∑12NPAHs in PM2.5 were higher in winter than those in summer because of the increased heating in winter. Atmospheric pollution levels of NPAHs at the Baofeng sampling site were generally higher than those at the Yinglite sampling because of the higher primary NPAHs emissions from coal mining and coke production in Baofeng compared with those from the chemical industry in Yinglite. The calculated nocturnal/diurnal ratios revealed that the concentrations of ∑12NPAHs in PM2.5 during the summer season were higher in the daytime than those in the nighttime, but the opposite trend occurred in winter, thus indicating that secondary formation processes made more contributions to NPAHs during summer in the daytime. The congener profiles of NPAHs were mainly composed of primary emission markers such as 2-nitrofluorene (2N-FLO) and 6-nitrochrysene (6N-CHR), which were the predominant ones in winter and summer for both the Baofeng and Yinglite sampling sites. Total proportions of 2N-FLO and 6N-CHR were 46% in winter and 73% in summer for Baofeng and 59% in winter and 55% in summer for Yinglite, respectively. Meanwhile, 3N-PHE, which is a marker compound of secondary formation processes, accounted for a higher percentage in summer especially at Yinglite. This finding revealed that the chemical production at Yinglite was associated with higher precursor emissions than that of Baofeng, and thus, more NPAHs were derived from secondary formation processes. Moreover, ∑12NPAHs/∑16PAHs ratios were calculated to identify the potential sources of NPAHs across the city. The results indicated that higher environmental temperatures in summer promoted the degradation of PAHs and secondary formation of NPAHs, and thus, secondary formation contributed more to NPAHs in summer than in winter. Furthermore, lung cancer risks induced by inhalation exposures to ∑5NPAHs were assessed based on the BaP equivalent toxicity factor. The results showed that the lung cancer risk values of ∑5NPAHs were (3.06×10-5±1.36×10-5) in winter and (1.79×10-5±0.80×10-5) in summer for the Baofeng sampling site, while the risk values were (2.85×10-5±1.20×10-5) in winter and (1.86×10-5±0.83×10-5) in summer for the Yinglite sampling site. Notably, the lung cancer risk values in our study for both sampling sites were higher than the standard limit value (1.00×10-5) of the California Environmental Protection Agency, which indicates that the local population at the Ningdong Energy and Chemical Industry Base has been subjected to potentially elevated lung cancer risks due to inhalation exposures to PM2.5-bound NPAHs.

[Pollution Characteristics and Occupational Exposure Risk of Heavy Metals in Indoor and Outdoor Ambient Particles at a Scaled Electronic Waste Dismantling Plant, Northwest China].

Atmospheric particle samples (PM1.0、PM2.5、PM10) were collected from three sampling sites (indoor and outdoor workplaces of a formal e-waste dismantling plant, and upwind area) in an arid area of Northwest China. The contents of six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) were analyzed using ICP-OES. Based on this data, the concentration levels, size distribution characteristics, and occupational exposure risks of heavy metals at the indoor and outdoor dismantling workplaces were studied. Particle analysis showed that Zn (4890 ng·m-3 indoors, 1245 ng·m-3 outdoors)、Pb (indoors 1201 ng·m-3, outdoors 240 ng·m-3), and Cu (indoors 1200 ng·m-3, outdoors 110 ng·m-3) showed higher pollution levels indoors and outdoors at the dismantling workplace. Moreover, the indoor concentration was much higher than that outdoors, indicating that the dismantling activity was the main cause of the high levels of heavy metal contamination. The indoor and outdoor air pollution characteristics were closely related to the types of electronic waste dismantled. Occupational exposure risk assessments showed that the total non-carcinogenic hazard quotient (HQ) of the indoor and outdoor dismantling workshops was 1.62×10-3, and 3.60×10-4, respectively, and the carcinogenic risk values were 2.69×10-7 and 2.59×10-9. Cd caused the greatest carcinogenic and non-carcinogenic risks at both indoor and outdoor dismantling workplaces, but it was still far below the limits (1.0) and acceptable ranges (1×10-6) stipulated by U.S. EPA, indicating that the health risks caused by heavy metals were minor or negligible. Heavy metals in the ambient particulate matter released from an adequately equipped and formally managed e-waste dismantling plant would not lead to any public health risk. The sedimentation characteristics of particulate heavy metals in different organs of the human respiratory system exhibited that the smaller the particle size was, the greater the proportion of deposition in the depths of the respiratory system was. Enterprises should make scientific and effective decisions on the respiratory health risks caused by such fine particles to the health of professional workers.

[Pollution Characteristics, Dry Deposition Fluxes, and Sources for Atmospheric Polycyclic Aromatic Hydrocarbons in the Bosten Lake Watershed].

Passive air samplers (PAS-PUF) and passive dry deposition (PAS-DD) samplers were applied in the Bosten Lake watershed located in Xinjiang to estimate the atmospheric concentrations and dry deposition fluxes for 15 US EPA priority polycyclic aromatic hydrocarbons (PAHs) during a heating period in 2016 and no-heating period in 2017, respectively. The results showed that the atmospheric PAHs concentrations in the Bosten oasis area ranged from 6.38 ng·m-3 to 245.43 ng·m-3 during the heating period and 2.33 ng·m-3 to 74.76 ng·m-3 during the non-heating period. The highest atmospheric PAHs concentrations were found in the residential area, followed by regions near Bosten Lake and Tazhong. The atmospheric dry deposition fluxes of PAHs in the Bosten Lake watershed ranged from 0.45 µg·(m2·d)-1 to 18.10 µg·(m2·d)-1 during the heating period and 0.25 µg·(m2·d)-1to 8.15 µg·(m2·d)-1 during the non-heating period. During the heating period, the atmospheric dry deposition fluxes in the residential area were significantly higher than those in the regions near Bosten Lake and Tazhong. However, the atmospheric PAHs dry deposition flux in Tazhong was much higher than that in other sites during the heating and no-heating periods. In general, the atmospheric PAHs dry deposition fluxes during the heating period were significantly higher than those during the non-heating period. PAH composition for the atmosphere and dry deposition were dominated by 3 and 4 ring congeners, especially by phenanthrene, fluorine, fluoranthene, and pyrene during two sampling periods. In addition, the congener diagnostic ratio shows that coal and biomass combustion were possible sources of atmospheric PAHs in the Bosten Lake watershed. The forward and backward trajectory analysis based on the HYSPLIT model demonstrated that the higher atmospheric PAH emissions from the residential area would be transported to Bosten Lake, which can affect the aquatic environment of this lake by dry deposition.

[Atmospheric Dry Deposition Fluxes and Sources of Polycyclic Aromatic Hydrocarbons in Lanzhou Valley, Northwest China].

The atmospheric dry deposition flux pollution levels were determined and the sources apportioned for 15 US EPA priority polycyclic aromatic hydrocarbons (PAHs) collected at 13 sampling sites in the Lanzhou valley using passive sampling techniques. The results are as follows. The annual atmospheric dry deposition fluxes ranged from 7.48 to 53.94 µg·(m2·d)-1, with a mean of 18.65 µg·(m2·d)-1. The highest flux levels for both the heating and non-heating seasons, 60.85 µg·(m2·d)-1 and 47.03 µg·(m2·d)-1, respectively, appeared at the traffic site (Donggang Bridge), where the heaviest traffic in the Lanzhou valley occurs. The lowest flux levels of 8.16 µg·(m2·d)-1 and 6.80 µg·(m2·d)-1 for the heating and non-heating seasons, respectively, were found at Baita Mountain, which has a higher percentage of vegetation cover. Meanwhile, the flux levels at the background site (Guantangou Mountain) were significantly lower than those of the other sampling sites. For dry deposition, the PAH components Phe, Flua, Flu, and Pyr were dominant in the heating and non-heating periods, and the sums of the percentages of 3- and 4-ring PAHs were 87.53% for the heating season and 82.73% for the non-heating season. Moreover, the percentage of 5- and 6-ring PAHs for the non-heating period was higher than that for the heating period, which may be because the lighter PAHs were easily volatilized, and thus escaped. Furthermore, the sources of atmospheric dry deposition were identified by principal component analysis (PCA). The results of source apportionment showed that the main atmospheric PAH dry deposition in the Lanzhou valley were from vehicle exhaust emissions, coal combustion, and the coking industry. In further detail, coal combustion and the coking industry contributed most of the PAH dry deposition emissions during the heating period except for the traffic area site of Donggang Bridge, whereas vehicle exhaust was the dominant contributor during the non-heating season. In addition, the annual average dry deposition velocities of atmospheric PAHs were calculated using the dry deposition model for three sites: 0.20 cm·s-1 downtown (Environmental Protection Agency of Lanzhou; JCZ), 0.15 cm·s-1 in an industrial area (Lanyuan Hotel of Xigu; LLH), and 0.17 cm·s-1 in a traffic area (the Staff Hospital of Gansu Province; ZGH), of which the latter two were relatively lower because of comprehensive meteorological factors such as wind speed, temperature, and land use categories. Regarding the dry deposition flux values of the 3- and 4-ring PAHs, the simulated values were a bit larger than the observed values, but all were at the same level of magnitude. However, the simulated flux values were closer to their observed values for 4-ring PAHs than for 3-ring PAHs, which indicated that 3-ring PAHs were lost more easily than 4-ring PAHs were during monitoring.

[Ecological risk assessment of organophosphorus pesticides in aquatic ecosystems of Pearl River Estuary].

The risk quotient method and a probabilistic risk assessment method were applied for assessing aquatic ecological risk of nine organophosphorus pesticides, including thimet, dichlorovos, disulfoton, dimethoate, dimethyl parathion, chlorpyrifos, ethoprophos, sumithion and malathion on eight aquatic organisms in the Pearl River Estuary. Results using the risk quotient method revealed that the risk level of opossum shrimp was the highest among eight aquatic organisms of the Pearl River Estuary. The risk of water flea and midge was in medium level, followed by the rest six aquatic organisms, including diatom, oyster, carp, catfish and eel, which were in the low risk by the examined organophosphorus pesticides. It was found that thimet made the largest contribution to total aquatic ecological risk among nine organophosphorus pesticides to every organism. The results from probabilistic risk assessment showed that the total ecological risk in high water period was higher than that in low water period determined by the HC5 under the 95% confidence level. The largest contribution of thimet to total aquatic ecological risk subject to the HC5 in 50% confidence level was regarded as the toxic reference value. The probabilistic risk of a single contaminant showed that thimet and disulfoton were harmful to exceeded 10% organisms in the estuarine. The probabilistic risk of nine pesticides mixture in high water period was also higher than that in low water period, and both risks were greater than 5% which exceeded safety threshold for 95% organisms in the Pearl River Estuary.

[Residual levels in air, soil and soil-air exchange of organochlorine pesticides in Hami region of Xinjiang and its potential ecological risk].

The concentrations of HCHs and DDTs in soil and air of urban/rural/forestry centre locations in the Hami region of Xinjiang were monitored for a year by passive atmospheric sampling in order to study the residual levels and air-soil exchange and evaluate ecological risk. The study results showed that the annual average concentrations of HCHs and DDTs in the air of Hami were 107.1 pg x m(-3) and 43.9 pg x m(-3), respectively, and the concentrations of HCHs and DDTs in summer and autumn were generally higher than those in winter and spring. It was deduced that the HCHs and DDTs tended to evaporate into the air because of the higher temperatures in summer and autumn. For OCPs in the air of study area, HCHs were dominanted the main pollution compared with DDTs. Meanwhile, alpha-HCH contributed the largest portion among all HCHs isomers, and p,p'-DDE dominated the residual levels of DDTs. Moreover, the values of alpha-HCH/gamma-HCH were in the range of 3 to 7, which indicated that the use of technical HCHs or the long distance atmosphere transport of HCHs may play a significant role for HCHs in the air of Hami region. Furthermore, ratios of (DDD + DDE)/DDTs were in the range of 0.4-0.9, 71.4% of which were higher than 0.5, indicating that DDTs in the air were mainly from historical usage and no new DDTs sources emerged in Hami recently. The concentrations of HCHs and DDTs in soil were between 0.344-6.954 ng x g(-1) and 0.104-26.397 ng x g(-1), respectively, which did not exceed the National Soil Quality Standard Level I. In addition, DDTs predominated in soil OCPs, in which beta-HCH accounting for a huge percentage in HCHs isomers, while o,p'-DDT predominated in pollution caused by DDTs isomers. From study results, it was also suggested that the important cause of DDTs residues in soil of Hami area could be the recent inputs of new sources since the value of (DDD + DDE)/DDTs were lower than 0.5. The sources of HCHs and DDTs in soil and atmosphere were not consistent, which was mainly caused by the different characteristics of soil and atmosphere and the complex geographical environment and climatic conditions in Hami region. The study on air-soil exchange showed that the escaping tendency of the various isomers of HCHs and p, p'-DDE was mainly from the soil to the air, on the contrary, the escaping tendency of o,p'-DDE,o,p'-DDD,p,p'-DDD,o,p'-DDT,p,p'-DDT was mainly from the air to the soil in Hami, which indicated that the soil was the sink of most of DDTs, and the air was the source of most of DDTs; while the air was the sink of HCHs and p,p'-DDE, and the soil was the source of HCHs and p,p'-DDE. There were potential risks of DDTs to birds and soil organisms in urban soil and forestry centre soil of Hami region, while the ecological risk of HCHs was light in Hami surface soil.

[Seasonal variation and spatial distribution of typical organochlorine pesticides in the atmosphere of Hexi Corridor and Lanzhou, northwest China].

Air samples were seasonally collected in Hexi Corridor and Lanzhou, Gansu province, using polyurethane foam (PUF) based passive air samplers for a year and determined hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs). Atmospheric concentrations of sigma HCHs (alpha-HCH +beta-HCH +gamma-HCH +delta-HCH) and sigma DDTs (p,p'-DDT + o,p'-DDT + p,p'-DDE + p,p'-DDD) were 86.22 pg x m(-3) and 34.06 pg x m(-3) in Hexi Corridor and Lanzhou with background concentrations of 54.41 pg x m(-3) and 21.56 pg x m(-3), respectively, which were lower than previously reported values elsewhere. In general, the seasonal pollution characteristics of sigma HCHs and sigma DDTs exhibited higher levels with the average concentrations of 127.4 pg x m(-3) and 47.06 pg x m(-3) in autumn, respectively. Furthermore, relatively higher residual concentrations of HCHs and DDTs were found in Jiuquan, Anxi and Zhangye, relating to their more arable lands and more intensively historical usage. Source apportionment indicated HCHs were mainly originated from historical technical-HCHs residues and recent Lindane usage. Recently introduced technical-DDTs was highly responsible for DDTs contamination, whereas the higher concentrations of o,p'-DDT observed in Jiuquan and Anxi may be attributed to dicofol usage. In addition, human exposure to HCHs and DDTs in Hexi Corridor and Lanzhou via inhalation could be relatively low.