Uptake, translocation, and risk assessment of PAHs in contaminated soil-air-vegetable systems based on a field simulation experiment.

Vegetable consumption is a potential toxin exposure pathway for humans. Studies have recognized that vegetables can uptake organic contaminants via roots and translocate pollutants to their aerial parts. However, the aerial parts might also directly uptake polycyclic aromatic hydrocarbons (PAHs) from contaminated soils. This has not been extensively studied. The aim of this study was to explore the uptake and translocation of PAHs in contaminated soil-air-vegetable systems. Sixteen individual PAHs in contaminated soils, vegetable roots, and leaves were identified using GC-MS. The results showed that the average PAH concentrations both in roots and leaves from the reference soil, the moderately contaminated soil, and the heavily polluted soil increased as expected. PAHs with log KOW < 5 accumulated more easily in roots and leaves. Using a Pearson correlation analysis, isomer ratios, and a principal component analysis (PCA), it was found that the contaminated soil not only caused PAH accumulation in roots, but also increased the PAH concentration in leaves. Quantitatively, the absorption of PAHs in roots in the moderately contaminated soil (70.3 ng m-3) was approximately twice that of the reference soil (40.8 ng m-3). The PAHs absorbed by vegetable roots in the heavily polluted soil (74.7 ng m-3) was only slightly higher than that of the moderately polluted soil. In addition, the PAH dose volatilized into the air from the reference soil, the moderately contaminated soil, and the heavily polluted soil also showed an increasing trend. The incremental lifetime cancer risk (ILCR) indicated that adult females had a higher cancer risk via vegetable consumption than other groups. Although vegetable consumption had a slight effect on cancer risk for some groups in the present study, the cancer risk of PAHs caused by eating vegetables grown in heavily contaminated soil still requires attention.

Impacts of biochar and silicate fertilizer on arsenic accumulation in rice (Oryza sativa L.).

Human exposure to arsenic (As) through rice consumption is a global food safety issue, especially in Southeast Asia. To investigate the impacts of biochar amendment (rice husk and smooth cordgrass-derived biochar) and/or silicate fertilizer on As mobility/phytoavailability in soil and on As accumulation in rice, pot and microcosm experiments were conducted. The results showed that both single application of low doses of biochar (0.5%, w/w) and coapplication of biochar with silicate fertilizer decreased As levels in grain (brown rice) by 14-16%, but not in straw and roots. The biodilution of As in grain resulting from increased grain biomass (by 6-21%) could be mainly a response to the decline in grain As levels with biochar and/or silicate fertilizer amendment. However, both applications exerted limited effects to decrease the overall As uptake by rice grain and straw, potentially due to the small changes in As mobility/phytoavailability in amended soil relative to the control, although plant-available silicon (Si) from amendment could potentially inhibit As uptake. Furthermore, microcosm-based anaerobic incubation experiments demonstrated that As levels in soil solution increased (up to 11-14-fold) with increasing doses of biochar amendment (up to 5%, w/w), possibly due to biochar enhancing the reductive dissolution of iron (oxyhydr) oxides via an increase in the total number of iron-reducing bacteria (up to 1.6-3.2-fold). Our findings suggested that a low application rate of biochar may not be a very effective approach for mitigating As accumulation in rice, while a high application rate could enhance the health risk of As in As-contaminated flooded soil.

Occurrence, Distribution and Risk Assessment of Mercury in Multimedia of Soil-Dust-Plants in Shanghai, China.

The urban environment is a complex ecosystem influenced by strong human disturbances in multi-environmental media, so it is necessary to analyze urban environmental pollutants through the comprehensive analysis of different media. Soil, road dust, foliar dust, and camphor leaves from 32 sample sites in Shanghai were collected for the analysis of mercury contamination in soil-road dust-leaves-foliar dust systems. Mercury concentrations in surface soils in Shanghai were the highest, followed by road dust, foliar dust, and leaves, successively. The spatial distribution of mercury in the four environmental media presented different distribution patterns. Except for the significant correlation between mercury concentrations in road dust and mercury concentrations in leaves (r = 0.56, p < 0.001), there was no significant correlation between the other groups in the four media. Besides this, there was no significant correlation between mercury concentrations and land types. The LUR (Land use regression) model was used to assess the impact of urbanization factors on mercury distribution in the environment. The results showed that soil mercury was affected by factories and residential areas. Foliar dust mercury was affected by road density and power plants. Leaf mercury was affected by power plants and road dust mercury was affected by public service areas. The highest average HI (Hazard index) value of mercury in Shanghai was found in road dust, followed by surface soil and foliar dust. The HI values for children were much higher than those for adults. However, the HI values of mercury exposure in all sampling sites were less than one, suggesting a lower health risk level. The microscopic mechanism of mercury in different environmental media was suggested to be studied further in order to learn the quantitative effects of urbanization factors on mercury concentrations.

Characterization of polycyclic aromatic hydrocarbons (PAHs) in vegetables near industrial areas of Shanghai, China: Sources, exposure, and cancer risk.

Dietary consumption of contaminated vegetables may contribute to polycyclic aromatic hydrocarbon (PAH) exposure in humans; however, this exposure pathway has not been examined thoroughly. This study aims to characterize the concentrations of PAHs in six types of vegetables grown near industrial facilities in Shanghai, China. We analyzed 16 individual PAHs on the US EPA priority list, and the total concentration in vegetables ranged from 65.7 to 458.0 ng g-1 in the following order: leafy vegetables (romaine lettuce, Chinese cabbage and Shanghai green cabbage) > stem vegetables (lettuce) > seed and pod vegetables (broad bean) > rhizome vegetables (daikon). Vegetable species, wind direction, and local anthropogenic emissions were determinants of PAH concentrations in the edible part of the vegetable. Using isomer ratios and principal component analysis, PAHs in the vegetables were determined to be mainly from coal and wood combustion. The sources of PAHs in the six types of vegetables varied. Daily ingestion of PAHs due to dietary consumption of these vegetables ranged from 0.71 to 14.06 ng d-1 kg-1, with contributions from Chinese cabbage > broad bean > romaine > Shanghai green cabbage > lettuce > daikon. The daily intake doses adjusted by body weight in children were higher than those in teenagers and adults. Moreover, in adults, higher concentrations of PAHs were found in females than in males. For individuals of different age and gender, the incremental lifetime cancer risks (ILCRs) from consuming these six vegetables ranged from 4.47 × 10-7 to 6.39 × 10-5. Most were higher than the acceptable risk level of 1 × 10-6. Our findings demonstrate that planting vegetables near industrial facilities may pose potential cancer risks to those who consume the vegetables.

Heavy metals and lead isotopes in soils, road dust and leafy vegetables and health risks via vegetable consumption in the industrial areas of Shanghai, China.

Vegetable fields have a high risk of heavy metal contamination from pollution sources in suburban and industrial areas of cities. Eighty-seven soil samples, 106 leafy vegetables and 48 road dust samples were collected from industrial areas of Shanghai, China. We studied the levels of heavy metals, health risk through consumption of leafy vegetables, and sources of Pb in soils, road dust and leafy vegetables. Soil Cd, Zn, Pb, Cu, Hg and As concentrations exceeded the soil background values in 73.6%, 97.7%, 52.3%, 37.8%, 95.1% and 20.2% soil samples, respectively, but were below the criteria for agricultural soil in China, with the exception of Hg. The concentrations of Cd, Zn, Pb, Cu and As in road dust were significantly higher than concentrations in soils, while Hg concentration in road dust was lower. Cd, Zn, Pb, Hg and Cu concentrations in soils and Zn, Pb and Cu concentrations in road dust were greatest near the municipal solid waste incineration power plant. Heavy metal concentrations in the edible tissues of vegetables were not correlated with their total values in soils and varied among vegetable species. The trends in transfer factors (TFs) in different vegetables were Cd>Zn>Cu>As>Hg>Pb. There was low health risk from heavy metal exposure by consumption of vegetables based on Hazard Quotients (HQM): As was the major contributor to HQM, followed by Cd and Pb. Parent material of the Yangtze River Estuary was the major source of Pb in soils, while coal-fired, stationary industrial emissions and municipal waste incineration emissions were the major sources of Pb in dust and vegetables based on use of the lead isotopic tracing method. Accumulation of Pb in leafy vegetables was through foliar uptake and directly related to atmospheric Pb.

Spatial variation and sources of polycyclic aromatic hydrocarbons influenced by intensive land use in an urbanized river network of East China.

The concentrations and distribution of polycyclic aromatic hydrocarbons (PAHs) in urbanized river networks are strongly influenced by intensive land use, industrial activities and population density. The spatial variations and their influencing factors of 16 priority PAHs were investigated in surface water, suspended particulate matter (SPM) and sediments among areas under different intensive land uses (industrial areas, agricultural areas, inner city, suburban towns and island areas) in the Shanghai river network, East China. Source apportionment was carried out using isomer ratios of PAHs and Positive Matrix Factorization (PMF). Total concentrations of 16 PAHs ranged from 105.2 to 400.5 ng/L, 108.1 to 1058.8 ng/L and 104.4 to 19,480.0 ng/g in water, SPM and sediments, respectively. The concentrations of PAHs in SPM and sediments varied significantly among areas (p < 0.05), with the highest concentrations in inner city characterized by highly intensive land use and high population density. The PAH concentrations in sediments were positively correlated with those in SPM and were more strongly correlated with black carbon than with total organic carbon, indicating a stronger influence of prolonged anthropogenic contamination than the recent surface input in sediments. Biomass and coal combustion contributed strongly to total PAHs, followed by natural gas combustion in water and SPM, and vehicular emissions in sediments. Vehicular emissions were the strongest contributors in SPM and sediments of the inner city, indicating the strong influence of vehicular transportation to PAHs pollution in the urbanized river network.

[Distribution Characteristics and Health Risk for Heavy Metals in Vegetables Near the Industrial Areas in Shanghai].

The concentrations of Cd, Zn, Pb, Cu, Hg, and As in vegetables collected from the industrial areas in suburban Shanghai were analyzed before and after washing. Results showed that the average concentrations (fresh weight) of Cd, Zn, Pb, Cu, Hg, and As in washed vegetables were 0.023, 4.444, 0.112, 0.826, 0.004, and 0.094 mg·kg-1, respectively. Amaranth accumulated the highest Cd, Zn, Pb, and Cu, while pakchoi accumulated the highest Hg and As. There was no significant difference of heavy metals between different sites. Washing vegetables prior to cooking reduced the health risk for heavy metals related to the consumption of vegetables. A health risk evaluation indicated that more than 55% of the Total Target Hazard Quotient (TTHQ) came from As, while the other elements contributed less than 1, indicating that the health risk from vegetable consumption was mainly caused by As. Children have higher health risks than adults when eating the same vegetables.

[Concentrations and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils and Vegetables influenced by Facility Cultivation].

The concentrations, sources, and health risks of 16 United States Environmental Protcction Agency(USEPA) priority polycyclic aromatic hydrocarbons (PAHs) in vegetables (leafy lettuce, amaranth, water spinach, and Shanghai green), in soils inside and outside the vegetable greenhouse, and in wet deposition were investigated by conducting an experiment on facility cultivation. The results showed that the average concentrations of total PAHs in vegetables and soils were 99.27 ng·g-1and 128.01 ng·g-1 in the greenhouse, and 109.11 ng·g-1 and 173.07 ng·g-1 out of the greenhouse. The concentrations of PAHs in the greenhouse were lower than those outside and the high ring-PAHs were lower than the low ring-PAHs both inside and outside. The PAH concentrations in suspended particular matter in dissolved phases of wet deposition were 2986.49 ng·g-1 and 61.9 ng·L-1, respectively. The low rings were easily enriched by the vegetables based on the shoot concentration factors. PAHs in soils and vegetables mainly originated from oil emissions and grass, wood, and coal combustion, while those in suspended particular matter in wet deposition were from petrogenic sources and the combustion of grass, wood, and coal. Petroleum combustion emissions were the main sources of PAHs in dissolved phases. We used the model of incremental lifetime cancer risks to evaluate the health risk of eating these vegetables. There was a potential risk of cancer for both children and adults for all vegetables except amaranth. The carcinogenic risk of vegetables outside the greenhouse was higher than the risk inside. Amaranth had a low carcinogenic risk with the value of incremental lifetime cancer risk lower than 10-6, while the risk of Shanghai green ranged between 10-4 and 10-6.

Characteristics, identification, and potential risk of polycyclic aromatic hydrocarbons in road dusts and agricultural soils from industrial sites in Shanghai, China.

Road dusts and agricultural soil samples were collected from eight sites close to steel mills, chemical plants, and municipal solid waste incinerator in suburban Shanghai. Sixteen polycyclic aromatic hydrocarbons (PAHs) in the United States Environmental Protection Agency (US EPA) priority controlled list were analyzed quantitatively using GC-MS. The total PAH concentrations ranged from 0.79 to 6.2 µg g-1 in road dust samples with a mean value of 2.38 µg g-1 and 0.26 to 0.54 µg g-1 in agricultural soils with an average of 0.36 µg g-1. The most abundant individual PAHs were phenanthrene, fluoranthene, pyrene, chrysene, and benzo(b)fluoranthene in dust samples and phenanthrene, fluoranthene, chrysene, and benzo(b)fluoranthene, benzo (k) fluoranthene in soil samples. Dominant compounds were four-ring and five- to six-ring PAHs, which accounted for 41.5 and 31.5 % in dusts and 33.9 and 41.1 % in soils. The spatial distribution of PAHs in dusts and soils was consistent. The wind direction could affect the spatial distribution of PAHs. Organic matter contents were found to be significantly positively correlated with PAH concentrations in both dusts and soils while grain size of particles had no correlation with PAH concentrations and could not significantly influence the distribution of PAH concentrations. PAH isomer ratios showed that combustion of grass, wood, and coal was important sources of PAHs in road dusts and agricultural soils. Toxic equivalent concentrations indicated seven kinds of carcinogenetic PAHs were major toxic equivalent concentration (TEQ) contributors, accounting for 98 % of TEQ, in the road dusts and agricultural soils. Incremental lifetime cancer risk (ILCR) estimation results showed that the PAHs in the dusts and soils had potential cancer risk for both children and adults only by direct ingestion exposure. The TEQ and ILCR values of PAHs in road dusts were much higher than those in soils, which suggested that PAHs in road dusts could be an important source of PAHs in soils.

[Spatial Distribution Characteristics and Risk Assessment of Polychlorinated Biphenyls (PCBs) in Sediments and Soils from the Dishui Lake and Its River System].

In order to investigate the pollution levels of PCBs in urban artificial lake, fourteen PCB congeners in sediments and soils of Dishui Lake and its river system were quantified by GC/MS, and then the distributions, sources and ecological risk of PCBs were discussed. The results showed that the concentrations of ∑14 PCBs in sediments and soils ranged from 0.65-16.41 ng·g-1 (dry weight, dw) and 0.47-1.27 ng·g-1, respectively, which were at a low level in general. Higher concentrations of PCBs were found in surface sediments from the river system of Dishui Lake than those in surface and core sediments from Dishui Lake, which indicated that the sediments in Dishui Lake would be polluted by the river system in the process of diversion. The concentrations of PCBs in core sediments decreased with depth, which showed that the sediments of Dishui Lake had been polluted by PCBs since its completion. In all samples, Tetra-CBs and Penta-CBs accounted for 20.65% and 67.12% of ∑14 PCBs, respectively, and PCB105, PCB118 and PCB77 were the dominant compounds. The results of source apportionment by principal component analysis (PCA) indicated that PCBs in sediments and soils from Dishui Lake and its river system were influenced by the historical cumulative emissions of 2#, 1# PCBs used in China and municipal solid waste incineration and combustion sources. The toxic equivalents (TEQs) of 12 (DL-PCBs) ranged from 0.01-79.40 pg·g-1, and the TEQs in 7 samples of surface sediments from Dishui Lake and its river system were beyond the interim sediments quality guidelines (ISQGs) suggested by USEPA, which would result in potential eco-toxicological risks for aquatic organisms.

[Distribution and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments and soils from Ddishui Lake and its water exchange areas].

Twenty-three surface sediment samples were collected from Dishui Lake and its surroundings, and 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed using GC-MS. The distribution characteristics, possible sources and ecological risk were investigated. The results show that the concentrations of total PAHs range between 11.49 ng x g(-1) and 157.09 ng x g(-1) with a mean value of 66.60 ng x g(-1) in sediments from Dishui Lake, which is lower than the mean value in the catchment area but higher than that in the drainage area. Median and high molecular weight PAHs (4 rings, 5-6 rings) are the dominant compounds compared to the low molecular weight PAHs (2-3 rings) in surface sediments and soils from the lake's surroundings, while in Dishui Lake low and high molecular weight PAHs are the dominator. Based on the PAHs molecule ratios, using principal component analysis and multiple line regression, a combustion source is diagnosed in the lake's surroundings, while the mix sources of leakage of petroleum and combustion are found in Dishui Lake. Ecological risk assessment result indicates that PAHs in the sediments and soils in Dishui Lake and its water exchange areas pose little biological adverse impact.

[Delivery and release of sediment PAHs during resuspension].

The resuspension of sediment after being disturbed is simulated by particle entrainment simulator (PES). The conclusions came out as follows. Sediment nature like granulometric composition and sediment PAHs richness markedly affected the release of PAHs. During the resuspension experiment, the total suspended solids (TSS) content of the overlying water showed significant correlation with particulate PAHs. The influence of the shear stress on the release of PAHs was reflected on two aspects. On one hand, its increase was accompanied with the increase of particulate PAHs. On the other hand, the PAHs enrichment effect of TSS decreased with the increase in the shear stress, since the stronger shear stress could draw more coarse particles with fewer PAHs into overlying water. The total PAHs in the overlying water continued to raise before stabilization at 120 min or 240 min. The particulate PAHs and dissolved PAHs answered each other very well. The release behavior among PAHs of different weight varied significantly. Due to the hydrophobic property of heavy weight PAHs, PAHs detected in overlying water were mostly 3-ring or 4-ring.

[Phosphorus adsorption characteristics of soils and sediments surrounding Dishui Lake in Shanghai].

Soils and sediments of different origins were collected, which included the cropland soils surrounding Dishui Lake, the sediments from rivers, the sediments of wetland and the sediments in Dishui Lake. These samples were used for the experiment of phosphorus isothermal adsorption. The results of this experiment were analyzed and fitted. It shows that, the adsorption-desorption equilibrium mass concentration (EPC(0) value) of the sediments in Dishui Lake (0.11-0.63 mg x L(-1)) is higher than that of the soils and sediments from other sources, which indicates that it is easier to release phosphorus to overlying water. Both the Langmuir model and Freundlich model have a high fitting degree to the isothermal adsorption of phosphorus. The maximum adsorption capacity (Q(m)) calculated by Langmuir model demonstrate that the adsorption capacity of soils and sediments from different sources follows the order: sediments from rivers (1 003.05-2977.65 mg x kg(-1)) > sediments in Dishui Lake (669.77-1 717.94 mg x kg(-1)) > sediments of wetland (368.60-1 145.51 mg x kg(-1)) > cropland soils(441.36-702.30 mg x kg(-). It shows that the adsorption capacity of cropland soils is the weakest. Cropland soils can be a source of phosphorus in Dishui Lake when extra fertilizer is used.

[Pollution load and the first flush effect of BOD5 and COD in urban runoff of Wenzhou City].

Four typical rainfalls were monitored in two different research areas of Wenzhou Municipality. Concentrations of BOD5 and COD in six different urban runoffs were measured. In addition the event mean concentration (EMC), M (V) curve and BOD5/COD of pollutant were calculated. The results showed that concentrations of BOD5 and COD in different urban runoffs of Wenzhou ranged from ND to 69.21 mg x L(-1) and ND to 636 mg x L(-1). Concentrations of BOD5 and COD in different urban runoffs were decreasing over time, so it is greatly significant to manage the initial runoff for reducing organic pollution. Judged by EMC of BOD5 and COD in these five rainfalls, concentrations of pollutant in some urban runoffs were out of the integrated wastewater discharge standard. If these runoffs flowed into river, it would cause environmental pressure to the next level receiving water bodies. According to the M (V) curve, the first flush effect of COD in most urban runoffs was common; while the first flush effect of BOD5 was same as that of COD. The result also showed that organic pollution was serious at the beginning of runoff. The underlying surface type could affect the concentration of BOD5 and COD in urban runoff. While the results of BOD5/COD also suggested that biodegradation was considered as one of the effective ways to decrease the pollution load of organics in urban runoff, and the best management plans (BMPs) should be selected for various urban runoff types for the treatment of organic pollution.

Phosphorus loads from different urban storm runoff sources in southern China: a case study in Wenzhou City.

Storm runoff from six types of underlying surface area during five rainfall events in two urban study areas of Wenzhou City, China was investigated to measure phosphorus (P) concentrations and discharge rates. The average event mean concentrations (EMCs) of total phosphorus (TP), total dissolved phosphorus (TDP), and particulate phosphorus (PP) ranged from 0.02 to 2.5 mg · L(-1), 0.01 to 0.48 mg · L(-1), and 0.02 to 2.43 mg · L(-1), respectively. PP was generally the dominant component of TP in storm runoff, while the major form of P varied over time, especially in roof runoff, where TDP made up the largest portion in the latter stages of runoff events. Both TP and PP concentrations were positively correlated with pH, total suspended solids (TSS), and biochemical oxygen demand (BOD)/chemical oxygen demand (COD) concentrations (p<0.01), while TDP was positively correlated with BOD/COD only (p<0.01). In addition, the EMCs of TP and PP were negatively correlated with maximum rainfall intensity (p<0.05), while the EMCs of TDP positively correlated with the antecedent dry weather period (p<0.05). The annual TP emission fluxes from the two study areas were 367.33 and 237.85 kg, respectively. Underlying surface type determined the TP and PP loadings in storm runoff, but regional environmental conditions affected the export of TDP more significantly. Our results indicate that the removal of particles from storm runoff could be an effective measure to attenuate P loadings to receiving water bodies.

[Pollution load and the first flush effect of phosphorus in urban runoff of Wenzhou City].

Five typical rainfalls were monitored in two different research areas of Wenzhou municipality. The pH and concentrations of total phosphorus (TP), dissolved phosphorus (DP), particulate phosphorus (PP), total inorganic carbon (TIC), total organic carbon (TOC), total suspended substances (TSS), BOD5 and COD in six different kinds of urban runoff were measured. The results showed that, the concentrations of TP, DP and PP in different kinds of urban runoff of Wenzhou ranged from 0.01 to 4.32 mg x L(-1), ND to 0.88 mg x L(-1) and ND to 4.31 mg x L(-1), respectively. In the early stages of runoff process PP was dominated, while in the later, the proportion of DP in most of the runoff samples would show a rising trend, especially in roof and outlet runoff. Judged by the event mean concentration (EMC) of TP and DP in these five rainfalls, some kinds of urban runoff could cause environmental pressure to the next level receiving water bodies. Meanwhile, the differences among the TP and DP content (maximum, minimum and mean content) in various urban runoffs were significant, and so were the differences among various rainfall events. According to the M (V) curve, the first flush effect of TP in most kinds of urban runoff was common; while the first flush effect of DP was more difficult to occur comparing with TP. Not only the underlying surface types but also many physico-chemical properties of runoff could affect the concentration of TP in urban runoff. All the results also suggested that different best management plans (BMPs) should be selected for various urban runoff types for the treatment of phosphorus pollution, and reducing the concentration of TSS is considered as one of the effective ways to decrease the pollution load of phosphorus in urban runoff.

[Pollution characteristics and sources of polycyclic aromatic hydrocarbons in riparian soils along urban rivers of Wenzhou city].

Twenty one riparian soil samples along Jiushanwai River and Shanxia River of Wenzhou city were collected in August 2010 to investigate the pollution characteristics of polycyclic aromatic hydrocarbons (PAHs). The samples were extracted by an accelerated solvent extractor (ASE), purified by a purification column and determined by GC-MS. Results showed that the total concentrations of PAHs in the riparian soils ranged from 60.7 ng x g(-1) to 3 871.3 ng x g(-1), and the concentrations of sigma PAHs in soils along the Shanxia River were significantly lower than the levels along Jiushanwai River. The dominant compounds were 2 to 3 rings in the riparian soils along both rivers, which in average accounted for 62.47% - 72.51% in sigma PAHs. Compared with the PAHs concentrations in soils of other areas in the world, the riparian soils of the studied rivers were moderately polluted by PAHs, but the concentrations of BaP in three soil samples were much higher than the soil standard value of the former Soviet Union, which should be paid more attention. Based on the ratios of Ant/(Ant + Phe) and Fla/(Fla + Pyr) and principal component analysis results, PAHs in riparian soils of the studied rivers were mainly derived from both the petroleum and combustion.

[Pollution characteristics and sources of polycyclic aromatic hydrocarbons in urban rivers of Wenzhou city].

Concentrations of 18 polycyclic aromatic hydrocarbons (PAHs) in water and surface sediments collected from the urban rivers of Wenzhou city in spring and summer were measured by GC-MS. The results showed that the total PAHs concentrations in water and sediments of the studied rivers varied in ranges of 146.74-3 047.89 ng x L(-1) and 21.01-11 990.48 ng x g(-1), respectively. Higher concentrations occurred in spring. The low and middle rings of 2-4-ring were dominant in both water and sediments, but the concentrations of 5-ring and 6-ring PAHs in sediments were relatively higher than those in water. The EBaP values of PAHs in water of the studied rivers in spring and summer were 1.69-51.95 ng x L(-1) and 0-3.03 ng x L(-1), respectively. Eighty percent of water samples in spring surpassed the limits of BaP in surface water of China. The concentrations of sigma PAHs in the sediments both in spring and summer were lower than the ERM value, but part of the components of PAHs had values higher than the ERM, suggesting possible toxic effect on living organisms. Based on the PAHs molecule ratios and principal component analysis, a mixed PAHs source of petroleum and combustion in water and sediments was diagnosed, while sediments showed a greater proportion of combustion sources.

[Distribution and ecological risk assessment of polycyclic aromatic hydrocarbons in agricultural soil of the Chongming Island in Shanghai].

The concentration and ecological risk of Polycyclic aromatic hydrocarbons (PAHs) were investigated in thirty-three surface soil samples collected from cultivated land in Chongming Island in July 2008. Those samples were extracted using an accelerated solvent extractor (ASE) and determined by GC-MS. Results showed that the concentrations of PAHs ranged between 24.92-1014.61 ng x g(-1) (dry weight), with a mean value of 192.83 ng x g(-1). The sixteen priority PAHs with exception of Indeno(1, 2, 3-cd) pyrene (IcdP) and Dibenzo(a, h)anthracene (DahA) were all detected in all the samples. The dominant compounds were 2-3 ring and 4 ring PAHs, which accounted for 42.6% and 42.2%, respectively, while the 5-6 ring PAHs accounted for 15.7%. PAHs in soil were mainly derived from the fossil oil and the combustion of wood and coal, as determined by the concentration ratio method. The non-industrial combustion and automobile exhaust emissions in Chongming Island may be two of the important sources of PAHs in farmland soil. The analysis of ecological risk showed that the agricultural soil of Chongming Island had low ecological risk.

[Transport and release of Cd, Pb and Cr from the Yangtze Estuarine sediments during sediment resuspension event].

The effects of resuspension energy and duration on release and transport of sediment bound Cd, Pb and Cr in the southern coastal areas of Yangtze Estuary were analyzed experimentally using a particle entrainment simulator (PES). In the sediment resuspension experiment, concentrations of dissolved Cd, Pb and Cr in the overlying water were 0.015-0.157, 0.013-0.890 and 0.066-1.468 microg x L(-1) respectively, and concentrations of particulate Cd, Pb and Cr varied between 0.37-5.40, 8.3-137.1 and 31.6-557.7 microg x g(-1) respectively. Before the biofilm in column surface was not damaged by disturbance, a large number of Cd adsorption to biofilm was released to the overlying water during the resuspension, but after part of the biofilm was damaged with the enhanced disturbance energy, Pb and Cr were released from the sediments to overlying water in short-term. Intensity of physical disturbance was the main factor that influenced the variation of particulate heavy metal concentrations. Results of resuspension fluxes showed that Cd, Pb and Cr released to the water by resuspension were then re-adsorption to suspended particles, and gradually deposited in the bottom sediments when the hydrodynamic conditions weakened, which had less harm to the aquatic ecosystems of Yangtze Estuary. The resuspension process of Cd, Pb and Cr mainly includes the following migration and transformation process: adsorptions of heavy metals in biofilm, direct release and diffusion of dissolved heavy metals from pore water, oxidative release of sulfide associated metals in sediments, re-adsorption of heavy metals to suspended particles in overlying water and deposition of particulate heavy metals.