A field study of the relationship between sulfide-bound metals and bioaccumulation by Limnodrilus sp. in a heavily polluted river.

Acid volatile sulfide (AVS) has been regarded as an important factor controlling metal bioavailability in anoxic sediments, but its effect on metal accumulation under natural conditions is poorly understood. Here, a field study of the influence of AVS on metal accumulation by Limnodrilus sp. in a heavily polluted river is provided. Most of the study area was subject to anaerobic and strongly reducing conditions, and the concentration of trace metals in surface sediments was high, as were the concentration of AVS and simultaneously extracted metals (SEM; average AVS = 20.3 µmol g(-1), average ∑SEM5 = 9.42 µmol g(-1); ∑SEM5 refers to the sum of SEMCd, SEMCu, SEMPb, SEMNi, and SEMZn). Only a few species and small quantities of benthic invertebrates were found, and Limnodrilus sp. was dominant. There was no correlation between trace metal accumulation and (SEM-AVS), and in stations where (SEM-AVS) <0, the absolute value of bioaccumulation was high (average ∑BIO5 = 4.07 µmol g(-1); ∑BIO5 refers to the sum of BIOCd, BIOCu, BIOPb, BIONi, and BIOZn), indicating that there was no relationship between (SEM-AVS) and metal accumulation in Limnodrilus sp. This was likely because Limnodrilus sp. ingest sediment particles as their main food source, so pore water metals play a minor role in their bioaccumulation (BIO) of materials. However, ∑BIO5 was significantly correlated with ∑SEM5 (r = 0.795, p < 0.01), revealing that the large number of sulfide-bound metals (SEM) in sediments may play an important role in metal accumulation in Limnodrilus sp., which can assimilate sulfide-associated metals by the help of the digestive fluids in the digestive systems.

Ecological risks assessment and pollution source identification of trace elements in contaminated sediments from the Pearl River Delta, China.

Sediments from 14 stations in the Foshan Waterway, a river crossing the industrial district of Guangdong Province, South China, were sampled and subsequently analyzed. The 14 stations were selected for the pollution discharging features of the river, such as the hydrology, the distribution of pollution sources, and the locations of wastewater outlets. The ecological risks were assessed, and the pollution sources were identified to provide valuable information for environmental impact assessment and pollution control. The spatial variability was high and the range were (in milligrams per kilogram dry weight): Pb, 46.0~382.8; Cu, 33.7~ 482.3; Zn, 62.2~1,568.7; Ni, 28.5~130.7; Cr, 34.7~1,656.1; Cd, 0.50~8.53; Hg, 0.02~8.27; and As, 5.77~66.09. The evaluation results of enrichment factor and potential ecological risk index indicate that the metal pollution in the surface and bottom sediments were severely polluted and could pose serious threat to the ecosystem in most stations. Although the hazard levels of the trace element differed among the stations, Hg was the most serious pollutant in all stations. The results of principal component analysis (PCA) show that the discharge of industrial wastewater is the most important polluting factor whereas domestic sewage, which contains a large amount of organic substances, accelerates metal deposition. And potential pollution sources were identified by the way of integrating the analysis results of PCA and data gained from the local government. Therefore, the conclusion is drawn that Foshan Waterway is seriously polluted with trace elements, both in the surface sediment (0 to 20 cm) and the bottom sediments (21 to 50 cm) are contaminated.

[AVS concentrations in Xinan Creek and the influencing factors].

Sediment and overlying water samples were collected at 10 sampling stations at Xinan Creek, a tidal river in Pearl River Delta, and analyzed for physical and chemical characteristics as well as microbial incicators, in order to reveal the main factors dominating the spatial distribution of acid volatile sulfide (AVS). The effects of Eh, SRB OC and TS on the spatial distribution of AVS were investigated and the impact of AVS on the toxicity of heavy metals in the studied area was evaluated. The results showed that the range of AVS was 0.207-41.453 micromol x g(-1), with an average of 6.684 micromol x g(-1), which is relatively high compared to the results in other studies. The AVS value of the surface layer was higher than the bottom layer in 5 stations. The AVS values in both the surface layer and the bottom layer were highly variable, the coefficients of variation being 93.61% and 153.09% , respectively. The analytical results revealed that TS was the factor with the greatest impact on the spatial distribution of AVS, and the order was TS > OC > Eh > SRB. Potential ecological risk of heavy metals existed in 60% of the smpling stations based on the value of Sigma (SEM5-AVS), however, with the criterion of [Sigma(SEM5-AVS)]/foc, none of them had inacceptable ecological risk. Furthermore, in terms of single species of heavy metals, there was certain risk of toxic effect for all the five heavy metals (Cd, Ni, Cu, Zn and Pb). The above mentioned results will provide valuable data for the in-depth study of the formation mechanism of AVS and helpful reference for environmental impact assessment and scientific rehabilitation of heavy metals in polluted rivers.

[Acid volatile sulfide and bioaccumulation of Cr in sediments from a municipal polluted river].

Samples of sediment, overlying water, pore water, and benthic invertebrate were collected at 13 stations along a typical municipal polluted river in the Pearl River Delta. The samples were analyzed to study relationships between acid volatile sulfide (AVS) versus Cr(III) and Cr(VI) in sediment, overlying water, and pore water as well as Cr in Limnodrilus sp.. Based on the "Cr hypothesis", the relationship between AVS and bioavailability of Cr in heavily polluted areas was explored to extend the utility of AVS measurements as sediment assessments. The mean value of total Cr in sediment was 329.57 mg/kg, which was 9.4 times of background value (35 mg/kg). The result indicated that the study area has been seriously polluted by Cr. The concentrations of Cr(VI) in sediment and overlying water were low, indicating that most of Cr was in the form of Cr(III). In the study area, the value of AVS was relatively high with an average value of 650.38 mg/kg, while Cr in the pore water was low with the average of 68.42 microg/L. Cr(VI) in the pore water was below the detection limit except at Z1 station. The range of Cr concentrations in Limnodrilus sp. was from 12.46 mg/kg to 38.99 mg/kg of dried weight, with the average of 25.85 mg/kg, which was higher than other similar results in the literature. The result showed that the amount of Cr accumulation in Limnodrilus sp. was significant. A further analysis showed a significant correlation between Cr in Limnodrilus sp. and Cr in the pore water (r = 0.614, p < 0.05). Since most of Cr in pore water was in the form of Cr(III), the toxicity of Cr(III) in pore water to organism can not be neglected in the heavily polluted river.

[Acid volatile sulfide and heavy metals biotoxicity in a municipal polluted river].

The surface layer of sediment and overlying water samples of Foshan Waterway, a typical municipal polluted river in Pearl River Delta, have been sampled and analyzed. The analytical items of sediment and overlying water include AVS, Eh, SEM(Pb), SEM(Cd), SEM(Cu), SEM(Zn), SEM(Ni), SEM(Cr), and Eh, DO, respectively. The benthic macroinvertebrate investigation has been done at the same time in the same place. Combing the results above, the relationship between AVS and heavy metals biotoxicity in Foshan waterway has been discussed. The main object is to examine if the SEM-AVS criterion is valid in judging the biotoxicity of heavy metals in the heavily polluted river. The range of AVS is from 0.339 micromol/g to 69.579 micromol/g, with the average of 20.283 micromol/g. The maximum sigmaSEM5 (Sum of SEM(PB), SEM(Cd), SEM(Cu), SEM(Zn), SEM(Ni)) is 23.067 micromol/g, while the minimum is 1.062 micromol/g. Both the species and quantity of benthic macroinvertebrate are little, and most of them belong to pollution bearable species, with Limnodrilus sp. as dominative species. There are 9 sampling stations where the sigmaSEM5-AVS are below zero, and the analytical results of Non-matric multi-dimentional scaling (MDS) indicate the benthic community structure of 7 sampling stations among them are similar. It means that the heavy metals biotoxicity in the heavily polluted river has close relationship with the value of SEM-AVS. It also proves that heavy metals biotoxicity in sediment is complicated, which can't be explained by SEM-AVS completely.

[Food selenium content and resident daily selenium intake in Guangzhou City].

The investigation on the food selenium content in Guangzhou City of Guangdong Province showed that viscera of animal foods, aquatic products, eggs, and mutton were abundant with selenium ( > 150.0 microg x kg(-1)), followed by cereals and beans (46.5-98.3 microg x kg(-1)), vegetables (15.8 microg x kg(-1)), and fruits (4.97 microg x kg(-1)). Among vegetable foods, mushroom had the highest selenium content (46.0 microg x kg(-1)). The daily selenium intake of residents in Guangzhou was 98.5 microg, in which, 73.7% was contributed by animal foods, and 26.3% was from vegetable foods. Aquatic products, pork and rice contributed 24.8%, 22.3% and 17.2%, respectively. The food selenium content and resident daily selenium intake in Guangzhou could meet the demand of human health in the City.

[Influence of cage culture in Yaling Bay on water environment].

On the basis of on-the-spot survey and analysis of water quality and bed mud in different cage culture section from April of 2002 to January of 2003, the analysis result indicate that the main influence of cage culture on environment are that: (1) It increase the content of nutrition salt, BOD, COD, organic matter and TSS, especially inorganic-nitrogen, inorganic-phosphor and ammonia nitrogen; (2) It enrich N, P, sulphide and organic matter in sediment. The most obvious is nitrogen, sulphide and ammonia nitrogen, next is total nitrogen and organic matter.