Long-term impact of accidental pollution on the distribution and risks of metals and metalloids in the sediment of the Longjiang River, China.

In January 2012, a serious accident polluted the Longjiang River with high concentrations of cadmium (Cd) and other concomitant metals and metalloids in the water. After emergency treatment (i.e., the addition of coagulants), these metals and metalloids were transferred from the water into the sediment through precipitation of the flocculent materials produced. In this study, the long-term distribution of six metals and metalloids in the sediment of the Longjiang River was investigated and their ecological risks were assessed. Approximately 1 year after the accident (i.e., late 2012), the average Cd content in the sediment of the affected sites decreased to 25.6 ± 19.5 mg/kg, which was 8 times higher than that of 3.16 ± 3.18 mg/kg in the upstream reference sites. In 2016 and 2017, the average Cd content in the sediment of the affected sites further decreased to 4.91 ± 2.23 and 6.27 ± 4.27 mg/kg, respectively. Compared with late 2012, the amounts of Zn, Pb, and Cu obviously decreased in 2016 and 2017, whereas there were no obvious differences in the As and Hg amounts during 3 years considered. Among metals and metalloids, the average contribution of Cd to the potential ecological risk index (RI) was 90%, 69%, and 70% in the affected areas in 2012, 2016, and 2017, respectively, suggesting that Cd was the most important factor affecting the ecological risk of metals in the Longjiang River. It should be noted that the average contribution of Hg to RI in the affected areas increased from 8% in 2012 to 25% and 23% in 2016 and 2017, respectively. The sequence of contribution of six elements was Cd > Hg > As>Pb > Cu ≈ Zn. A high ecological risk of metals and metalloids was found in the sediments of two reservoirs, probably owing to the barrier effect of the dam. This study will be useful for the environmental management of rivers affected by accidental pollution of metals and metalloids.

[Distribution and Bioaccumulation Characteristics of Cadmium in Fish Species from the Longjiang River in the Guangxi Autonomous Region].

Emergent cadmium pollution can cause water quality deterioration in rivers, which destroys the aquatic eco-environment and poses threats to human health. Fish species in these aquatic systems are prone to such pollution incidents and act as important indicators of the pollution level. Because cadmium enters the systematic circulation of fish and is non-biodegradable, the investigation of cadmium accumulation in fish bodies provides insights into the detrimental effects of cadmium pollution on the aquatic biological system. This research aims to validate the eco-environmental risks associated with emergent cadmium pollution incidents based on the investigation of the different tissues and organs of diverse fish species. The investigation was conducted six times along the Longjiang River using sampling methods during which all fish species were also classified and analyzed based on the water layer they reside in and their feeding habits. The results show that the cadmium concentration in the fish tissues is significantly higher in the former three investigations compared with that of the latter three analyses. For herbivorous, carnivorous, and omnivorous fish species, the cadmium concentration of their different tissues and organs follows the order:kidney > liver > gut > gill > egg > scale ≈ muscle. The cadmium concentration in the kidney is significantly higher (P<0.05) than that in any other organs of the fish species. This agrees with the fact that the kidney intensively metabolizes and accumulates heavy metals. The cadmium concentration in the same tissues or organs of the fish species living in different water layers follows the trend:demersal fish species > middle lower-layer species > middle upper-layer species. The sequence of the cadmium bioaccumulation factors in the muscles of different fish species is omnivore > carnivorous > herbivorous, that is, 8.32, 6.33, and 5.15, respectively, while the bioaccumulation factors in the muscles of the fish species in different water layers decrease in the following sequence:demersal fish species (8.18) > middle bottom-layer fish species (7.70) > middle upper-layer fish species (4.99). These experimental results indicate the biomagnification effects in heavy metal-polluted aquatic environments, where the bioaccumulation of heavy metals by fish is related to both the overall pollution level and local residential environment.

Seasonal occurrence, removal and risk assessment of 10 pharmaceuticals in 2 sewage treatment plants of Guangdong, China.

A long-term investigation, which covered 10 sampling campaigns over 3 years, was performed to evaluate the occurrence, removal and risk of 10 pharmaceuticals in 2 full-scale sewage treatment plants (STPs) in Guangdong, South China. Target pharmaceuticals except for clofibrate and ibuprofen were detected in every sample, with mean concentrations of 12.5-685.6 and 7.9-130.3 ng/L in the influent and effluent, respectively. Salicylic acid was the most abundant compound in both the influents and effluents in the two STPs. For most pharmaceuticals, the seasonal variation in the influent showed the highest concentrations in January and lowest concentrations in July due to their consumption and rainfall. Ibuprofen and fenoprofen presented high removal rates (>90%) and some of the targets such as gemfibrozil, mefenamic acid, tolfenamic acid and diclofenac were detectable with significantly higher mass loads in effluents than in influents. Studies of the five efficiently eliminated pharmaceuticals show that the primary treatment and secondary treatment contributed to most pharmaceutical removal, the anoxic tank made a negligible contribution to their elimination. According to the results produced from the calculation of the risk quotient, only diclofenac might pose a risk to the aquatic environment.

Distribution and ecological risk assessment of cadmium in water and sediment in Longjiang River, China: Implication on water quality management after pollution accident.

In early January 2012, the Longjiang River was subjected to a serious cadmium (Cd) pollution accident, which led to negatively environmental and social impacts. A series of measures of emergency treatment were subsequently taken to reduce water Cd level. However, little information was available about the change of Cd level in environmental matrices and long-term effect of this pollution accident to aquatic ecosystem. Thus, this study investigated the distribution of Cd in water and sediment of this river for two years since pollution accident, as well as assessed its ecological risk to aquatic ecosystem of Longjiang River. The results showed that it was efficient for taking emergency treatment measures to decrease water Cd concentration to below the threshold value of national drinking water quality standard of China. There was high risk (HQ > 1) to aquatic ecosystem in some of reaches between February and July 2012, but low or no risk (HQ < 1) between December 2012 to December 2013. Cd concentration in sediment in polluted reaches increased after pollution accident and emergency treatments in 2012, but decreased in 2013. During flood period, the sediment containing high concentration of Cd in Longjiang River was migrated to downstream Liujiang River. Cd content in sediment was reduced to background level after two years of the pollution accident occurrence. The study provides basic information about Cd levels in different media after pollution accident, which is helpful in evaluating the effectiveness of emergency treatments and the variation of ecological risk, as well as in conducting water management and conservation.

[Eutrophication and Characteristics of Cyanobacteria Bloom in the Summer in Guishi Reservoir].

Large-scale cyanobacteria bloom occurred in the summer of 2014 in the Guishi Reservoir that is an important drinking water source for Hezhou City. The dynamic change regularity, external pollution sources, and the phytoplankton community characteristics during the bloom were investigated to evaluate the eutrophication in the reservoir and to present effective prevention and control measures. The results showed that nitrogen and phosphorus concentrations increased year by year; water quality on some sites has been out of class Ⅱ of national water quality standards; and the main pollution source was the agricultural non-point sources. Phytoplankton cell density was in the range of 8.60×106-5.36×108 cells·L-1 and chlorophyll a concentrations reached 74.48 µg·L-1 during the bloom. The dominant species was Microcystis wesenbergii whose density reached 5.36×108 cells·L-1. The cell density decreased over time and concentrated on the surface and at the depth of 2 m underwater. The total phytoplankton cell density was strongly correlated to total phosphorus, total nitrogen, nitrate nitrogen, and the permanganate index, and was inversely correlated to transparency. The water in the Guishi Reservoir was not polluted by microcystic toxins. Moreover, Guishi Reservoir is in a meso-eutrophic state; therefore, the prevention and control of the cyanobacteria bloom should focus on weather conditions and on reducing the input of nitrogen and phosphorus to keep the nutrient levels low.

[Accumulation Characteristics and Health Risk Assessment of Heavy Metals in Wild Fish Species from Diaojiang River, Guangxi].

To explore the accumulation characteristics and health risk assessment of heavy metals in wild fish species, the concentrations of heavy metals (Pb, Cd, Cr, As and Hg) in the muscle samples of eight wild fish species collected from Diaojiang River, Guangxi were analyzed. The degree of pollution, food safety and health risk of heavy metals in wild fish species were evaluated using the average pollution index and the target hazard quotient methods. The results showed that the concentrations of Pb, Cd, Cr, As and Hg in wild fish species ranged from 0.041 to 1.160, 0.0001 to 0.066, 0.173 to 0.789, 0.010 to 2.420 and 0.0007 to 0.077mg·kg-1, respectively. The concentrations of Pb and As in wild fish species exceeded the limit values of the Maximum Levels of Contaminants in Foods (GB 2762-2012), and the over-standard rates were 5.06% and 64.56% respectively. The concentrations of Cd, Cr and Hg did not exceed the standard. The average pollution index results showed that Acheilognathus tonkinensis and Acheilognathus barbatus were seriously polluted by heavy metals. The Oreochromis niloticus were moderately polluted. The Siniperca kneri Garman, Carassius auratus, Pseudohemiculter dispar, Ctenopharyngodon idellus, Hemiculter leucisculus were slightly polluted. Higher bioaccumulation factors of Pb, Cr and Hg were found in wild fish species from Diaojiang River. The concentrations of heavy metals in carnivorous fish and omnivorous fish were higher than those in herbivorous fish. Potential health risk assessment showed that the total target hazard quotients (TTHQ) of Acheilognathus tonkinensis and Acheilognathus barbatus were higher than 1. It indicated that the local residents posed higher human health risk due to the long-term consumption of Acheilognathus tonkinensis and Acheilognathus barbatus. Among all the TTHQ in wild fish species (except Pseudohemiculter dispar and Hemiculter leucisculus), the contribution rate of As was the highest, and the average contribution rate reached 76.63%, which indicated that As was the main risk factor.

[Nitrogen Release Performance of Sediments in Drainage Pipeline].

The effects of soil and water ratio, pH, temperature and rotation on the nitrogen transformation of sediment in drainage pipeline were investigated in this study. The experimental results for the four impact factors indicated that ammonia nitrogen was the main existing form for nitrogen release from the sediment to the overlying water, the concentration of ammonia nitrogen was uptrend, reaching the maximum in four to six days, and it went down till to the end of experiments. While the variation trend of nitrate nitrogen concentration was opposite to that of ammonia nitrogen. The factor of pH influenced most in the release of ammonia nitrogen among the four factors, then was the disturbance, and the temperature had a minimal impact. The release of ammonia nitrogen followed the descending order of pH 6.3 > pH 8.0 > pH 9.6, and the maximum concentrations were 54.0, 30.9 and 26.7 mg x L(-1) respectively. The higher soil and water ratio and the longer agitation time under the same agitation speed were, the higher ammonia nitrogen concentration was obtained. An increase in temperature promoted the conversion of ammonia nitrogen to the nitrate nitrogen, and speeded up the decrease of total nitrogen in the overlying water.

[Phytoplankton community structure and eutrophication risk assessment of Beijiang River].

To study the distribution of phytoplankton and water quality of Beijiang River, the community structure of phytoplankton was investigated and analyzed in wet and dry seasons. The results showed that a total of 74 species belonging to six phyla, 29 family and 48 genera of phytoplankton were identified, including 58 species of five phyla, 23 family and 41 genera in wet season and 59 species of six phyla, 26 family and 40 genera in dry season. Phytoplankton community structure in Beijiang River was represented by Bacillariophyta, Chlorophyta and Cyanophyta. Bacillariophyta dominanted the phytoplankton, and the dominant species were Aulacoseira granulate, Fragilaria virescens, Surirella biseriata, Nitzschia amphibia, Navicula simplex, Cyclotella meneghiniana, Synedra ulna, Gomphonema angustatum and Cymbella tumida. There was little difference in phytoplankton density between both seasons with the mean values being 3.54 x 10(5) and 4.87 x 10(5) cells L(-1) in dry and wet seasons, respectively. Based on the RDA results, DO, permanganate index, nitrogen and phosphorus were the important environmental factors affecting the distribution of phytoplankton in Beijiang River. The water quality of Beijiang River was classified as oligo-mesotrophic level even if this river was subjected to nitrogen and phosphorus pollution mainly from agricultural non-point source.

Assessment of exposure to heavy metals and health risks among residents near Tonglushan mine in Hubei, China.

Heavy metal contamination due to mining activity is a global major concern because of its potential health risks to local inhabitants. In the present study, we investigated the levels of Cd, Cu, Pb and As in soil, crop, well water and fish samples collected from the vicinity of the Tonglushan mine in Hubei, China, and evaluated potential health risks among local residents. Results indicate that soils near the mine were heavily contaminated with Cd (2.59 mg kg(-1)), Cu (386 mg kg(-1)), Pb (120 mg kg(-1)) and As (35.4 mg kg(-1)), and exceeded the soil quality standard values of Cd and Cu contamination. The concentrations of Cd, Cu, Pb and As in crop samples grown in mine-affected soils were significantly higher than those of the reference soils. The concentrations of Cd and As in most vegetables grown in mine-affected soils exceeded the maximum allowable level (MAL). The Cd, Pb and As concentration in rice grain collected from mine-affected soils were 2.95, 1.85 and 2.07-fold higher than the MAL, respectively. The concentrations of Cd and As in fish muscle from the mine-affected area were above national MAL in 61% and 34% of analyzed samples, respectively. All measured heavy metals except Pb were significantly greater in well water in the mine-affected area than those in the reference areas. The average estimated daily intakes of Cd and As were beyond the provisional tolerable daily intake, respectively. The intake of rice was identified as a major contributor (⩾72%) to the estimated daily intake among the residents.

[Selection of electrochemical anodic materials for PFOA degradation and its mechanism].

Perfluorooctanoate (PFOA) is environmentally stable and endocrine-disrupting. It was resistant to conventional biodegradation and advanced oxidation processes. Electrochemical oxidation method was adopted to degrade PFOA. The anodes, including BDD, Pt, Ti, Ti/RuO2, Ti/RuO2-IrO2, Ti/In2O3, Ti/SnO2-Sb2O5,-IrO2, Ti/SnO2-Sb2O5,-RhO2, Ti/SnO2-Sb2O5, Ti/ SnO2-Sb2O5,-CeO2 and Ti/SnO2-Sb2O5-Bi2O3, were selected as the candidate materials. The oxygen evolution potential (OEP) were determined by linear sweep voltammetry (LSV). The degradation ratios and the defluorination ratios were used to evaluate the oxidation ability of anodic materials. Ultrasonic electrochemical oxidation indirectly demonstrated that direct electron transfer was the initial step for PFOA decomposition. The anodes of Ti/SnO,-Sb20 ,-Bi2,03, Ti/SnO-Sb ,O,-CeO,, Ti/SnO2-Sb20, and BDD effectively degraded PFOA, and the decomposition ratios were 89. 8% , 89. 8% , 93. 3% and 98. 0% , respectively. The removal ratios of PFOA on Ti/ SnO2-Sb2O5,-RhO2, Ti/SnO2-Sb2O5-IrO2, and Ti/In2O3 anodes were low, and the values were 2. 1%, 2.3% , 12. 5% and 3.1%, respectively. However, Ti, Ti/RuO2 and Ti/RuO2-IrO2, had no effect on PFOA. PFOA molecule transferred electrons to the anode, decarboxylated, and followed the CF2, unzipping cycle. The intermediate products detected were C6F13 COO- , C5F11COO-, C4F9COO- and C3F7,COO-.

Fenton Oxidation Kinetics and Intermediates of Nonylphenol Ethoxylates.

Removal of nonylphenol ethoxylates (NPEOs) in aqueous solution by Fenton oxidation process was studied in a laboratory-scale batch reactor. Operating parameters, including initial pH temperature, hydrogen peroxide, and ferrous ion dosage, were thoroughly investigated. Maximum NPEOs reduction of 84% was achieved within 6 min, under an initial pH of 3.0, 25°C, an H2O2 dosage of 9.74×10-3 M, and a molar ratio of [H2O2]/[Fe2+] of 3. A modified pseudo-first-order kinetic model was found to well represent experimental results. Correlations of reaction rate constants and operational parameters were established based on experimental data. Results indicated that the Fenton oxidation rate and removal efficiency were more dependent on the dosage of H2O2 than Fe2+, and the apparent activation energy (ΔE) was 17.5 kJ/mol. High-performance liquid chromatography and gas chromatograph mass spectrometer analytical results indicated degradation of NPEOs obtained within the first 2 min stepwise occurred by ethoxyl (EO) unit shortening. Long-chain NPEOs mixture demonstrated a higher degradation rate than shorter-chain ones. Nonylphenol (NP), short-chain NPEOs, and NP carboxyethoxylates were identified as the primary intermediates, which were mostly further degraded.

Removal of naproxen and bezafibrate by activated sludge under aerobic conditions: kinetics and effect of substrates.

Naproxen and bezafibrate fall into the category of pharmaceuticals that have been widely detected in the aquatic environment, and one of the major sources is the effluent discharge from wastewater treatment plants. This study investigated the sorption and degradation kinetics of naproxen and bezafibrate in the presence of activated sludge under aerobic conditions. Experimental results indicated that the adsorption of pharmaceuticals by activated sludge was rapid, and the relative adsorbabilities of the two-target compounds were based on their log Kow and pKa values. The adsorption data could be well interpreted by the pseudo-second-order kinetic model. The degradation process could be described by the pseudo-first-order kinetic model, whereas the pseudo-second-order kinetics were also well suited to describe the degradation process of the selected compounds at low concentrations. Bezafibrate was more easily degraded by activated sludge compared with naproxen. The spiked concentration of the two-target compounds was negatively correlated with k1 and k2s , indicating that the substrate inhibition effect occurred at the range of studied concentrations. Chemical oxygen demand (COD) did not associate with naproxen degradation; thus, COD is not an alternative method that could be applied to investigate natural organic matter's impact on degradation of pharmaceuticals by activated sludge.

[Experimental studies on stability of flocs from cadmium pollution emergency treatment].

Taking the flocs from cadmium pollution emergency treatment of Longjiang River in Guangxi province as the research object, the stability of the flocs in the simulated static reservoirs and acidic floods was investigated based on the effects of disturbance and pH on the stability of the flocs. The results indicated that disturbance and pH had great effects on the stability of the flocs, and the concentrations of Cd2+ followed the order of pH 5.0 >> pH 6.0 > pH 7. 0 approximately pH 8.0 > pH 9.0 with the original pH of water. When the original pH of water was 5.0, the concentrations of Cd2+ in samples were 19-58 times higher than the national standard limit, and when the original pH of water were 6.0, 7.0, 8.0 and 9.0, respectively, the concentrations of Cd2+ in samples varied from below to 11 times higher than the national standard limit. The release of cadmium from the flocs was higher in the disturbed water, with the concentrations of Cd2+ in most samples higher than 5.0 microg x L(-1), and the highest was double of the national standard limit. In contrast, there was little release in the simulated static reservoirs, with the concentrations of Cd2+ in all samples below 5.0 microg x L(-1), which was lower than the national standard limit. Therefore, the flocs had good stability in the simulated static reservoirs. But it had poor stability in the simulated acidic floods, with higher release of cadmium, and the concentrations of Cd2+ in samples were 14-25 times higher than the national standard limit. Therefore, the monitoring of cadmium concentrations in the floods should be strengthened in the post project analysis for eco-environmental impact of Longjiang River.

[Characterization of water-soluble inorganic ions in PM2.5 and PM1.0 in summer in Guangzhou].

PM2.5 and PM1.0 samples were collected simultaneously during July of 2008 in Guangzhou. The concentrations of water-soluble inorganic ions (Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, and SO4(2-)) were determined by ion chromatography. Meteorological parameters, atmospheric scattering, visibility, and concentrations of trace gases (SO2, NO2, and O3) for this period were also recorded. The results showed the total water-soluble inorganic ions concentrations were (25.5 +/- 10.9) microg x m(-1) and (22. 7 +/- 10.5) microg x m(-3) in PM2.5 and PM1.0, which occupied (47.9 +/- 4.3)% and (49.3 +/- 4.3)% of PM mass respectively. Sulfate was the most abundant ion and contributed (25.8 +/- 4.0)% of PM2.5 mass and (27.5 +/- 4.5)% of PM1.0 mass respectively. High temperature and high ozone level favored the formation of sulfate from sulfur dioxide, while the high relative humidity favored the formation of nitrate were observed. Moreover, sulfate, nitrate, and ammonium in PM2.5 and PM1.0 had great impact on the scattering coefficient and visibility degradation.

[Preliminary study of PBDE levels in house dust and human exposure to PBDEs via dust ingestion].

Fifty-two house dust samples were randomly collected in Guangzhou and Haikou City, to analyze the concentrations of Sigma10 PBDEs (sum of BDE 28, 47, 66, 85, 99, 100, 153, 154, 183 and 209), the PBDE composition profiles, and possible influencing factors, and estimate human exposure to PBDEs via dust ingestion for adults and toddlers. The results showed that PBDEs were found in all samples, with the Sigma10 PBDEs concentrations ranging from 544.2 ng/g to 9 654 ng/g, and with median (mean) of 2 547 (3 096) ng/g. The PBDE levels in Guangzhou samples were obviously higher than those in Haikou. No significant correlations between PBDE levels and residential characteristics (number of TVs, computers, and polyurethane foam-contained furniture, time of using TVs and computers) were observed. BDE209, with a mean concentration of 3 021 ng/g, was the dominated congener, contributing 73.70%-99.74% to the Sigma10 PBDEs, with a mean contribution of 96.85%. BDE 47, 99 and 183 were the most abundant congeners of Sigma9 PBDEs (BDE 209 excluded), with a mean contribution of 24.48%, 23.99%, and 21.66%, respectively. There is no notable difference in PBDE composition between Guangzhou and Haikou samples. The estimated exposure for adults and toddlers to PBDEs ranged from 10.59 ng/d to 254.7 ng/d and from 140.1 ng/d to 509.3 ng/d, respectively. Due to their increased dust ingestion rates, toddlers in took more PBDEs via dust ingestion than adults. Dust ingestion was an important human exposure route for PBDEs, especially for toddlers.

Bioaccumulation behavior of polybrominated diphenyl ethers (PBDEs) in the freshwater food chain of Baiyangdian lake, north China.

Polybrominated diphenyl ethers (PBDEs) are of great environmental concern due to bioaccumulation in different food chains. Trophodynamics of PBDEs in freshwater food chain is an important criterion for assessing their ecological risk. In the study, PBDEs were analyzed in sixteen aquatic species collected from Baiyangdian Lake, North China. The concentrations of nine PBDE congeners (BDE-28, -47, -66, -99, -100, -85, -153, -154, and -183) in aquatic organisms ranged from 3.4 to 160.2ng/g lipid weight. BDE-47 was the predominant PBDE congener in most samples except for river snails and swan mussels. BDE-209 was detected in 50% of biota samples, which indicated the bioavailability of BDE209. Correlation between lipid-normalized concentrations of PBDEs and trophic levels determined by stable isotope nitrogen technologies confirmed that PBDEs were biomagnified in the freshwater food chain. The trophic magnification factors (TMFs) ranged from 1.3 to 2.1 for PBDE congeners, greater than one, indicating the biomagnification potential for the PBDE congeners in the freshwater food chain. The relationship between TMFs and Log K(ow) (octanol-water partition coefficient) indicated that the phenomenon of trophic magnification for lowly brominated congeners was obvious in the freshwater food chain.

[Distribution characteristic of organochlorine pesticides and polybrominated diphenyl ethers in tissues of ducks from Baiyangdian Lake, North China].

The concentrations of hexachlorocyclohexane (HCHs), dichlorodiphenyltrichloroethane (DDTs), and polybrominated diphenyl ethers (PBDEs) in muscle, liver and brain of ducks from Baiyangdian Lake were determined by gas chromatography coupled with mass spectrometer (GC/MS). The results showed that the concentrations of HCHs, DDTs and PBDEs in various tissues of ducks were in the range of 0.9-5.0 ng/g wet weight (WW), 0.3-2.8 ng/g (WW) and 0.03-0.65 ng/g (WW), respectively. Statistical analysis indicated that the accumulation of DDTs and PBDEs in muscle, liver and brain was significantly different (p < 0.05), but not with HCHs (p > 0.05). Liver tissues contained the highest DDTs and PBDEs levels, with average concentrations of 2.3 ng/g (WW) and 0.37 ng/g (WW), respectively. Among the HCH isomers and DDT metabolites, beta-HCH was the predominant isomers in liver and brain tissues, and p,p'-DDE was the dominant metabolites of DDTs in various tissues. Among the PBDE congeners, BDE47 and BDE99 were the predominant in various tissues. The different profiles of persistent organohalogen compounds in various tissues of ducks may reflect that the Baiyangdian Lake still subject to the contamination of historically residue for HCHs and DDTs. In addition, the source of PBDEs was partly attributed to the industrial pollution, chemical plants, and sewage discharging.

[Evaluation of the heavy metals contamination and its potential ecological risk of the sediments in Beijiang River's upper and middle reaches].

In order to find out the heavy metals concentrations and their potential ecological risks of the sediments in Beijiang river's upper and middle reaches, 25 sediments specimens were sampled from both the trunk stream and tributaries for analyzing Cu, Pb, Zn, Cd, Ni, Cr, As and Hg. The Index of Geoaccumulation and the Potential Ecological Risk Index were then employed to evaluate the pollution degree of heavy metals in the sediments. The results indicate that the sediments in Beijiang River have been severely contaminated by many heavy metals. The descending order of pollution degree of various metals is: Cd >> Hg > Zn > As > Pb approximately to Cu > Ni > Cr; and similarly the potential ecological risk intensity caused by different metals is: Cd >> Hg > Pb approximately to As > Cu > Zn > Cr, and Cd is the predominant element among them. In general, because the trunk stream receives huge waste discharge, the pollution degree of heavy metals is stronger in the trunk stream than that in the tributaries due to long time accumulation. The Maba River is the worst polluted among the tributaries, and the Zhengshui River and Wongjiang River are next to it.

[Content analysis and assessment of polycyclic aromatic hydrocarbons in surface sediments from Beijiang River, China].

In the present study, 16 polycyclic aromatic hydrocarbons (PAHs) in the surface sediment from Beijiang River in China were quantitatively determined by GC/MS. The concentration of PAHs varied from 38.2 to 6470 ng x g(-1) dry weight, with average 1071 ng x g(-1), which was in moderate level compared with other rivers in Pear River Basin. The PAHs distribution in Bejiang River was obviously affected by point source emissions. The high PAHs concentrations of 6470 ng x g(-1) and 4 470 ng x g(-1) were found at the outfalls of Shaoye and the Shakou town, respectively, where PAHs probably derived from local mining/smelting and related industrial actives. The ecological risk of surface sediment in Beijiang River was assessed with the methods of sediment quality guidelines (SQGs), sediment quality standards (SQSs) and contamination factors (CFs) . The result shows that the adverse biological toxicity effect might occasionally happen in more than half of sampling stations. By comparison with the background area, the contamination degrees of PAHs in 20 sampling stations were at very high level, which should arrest the local governments' attentions. The highest ecological risk areas occurred at the outfalls of Shaoye and the Shakou town in which the ecological risks derived from PAHs were within between probable effect level (PEL) and frequent effect level (FEL). The future research was suggested mainly focusing on the status of benthos, sources of pollutants and ways to control pollution in high-risk areas.