Suwen Yang

Tetrabromobisphenol A: tissue distribution in fish, and seasonal variation in water and sediment of Lake Chaohu, China

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardants (BFRs). It has been detected in various environment media and has been approved to be high toxic to aquatic organisms. However, the exposure levels of TBBPA in the main watersheds in China have not been investigated sufficiently. In this study TBBPA concentrations in water, sediment and tissues of four fish species from Lake Chaohu were determined. Spatial and temporal distribution patterns of TBBPA in water and sediment, and the relationship among TBBPA concentrations in fish tissues and fish size were analyzed. The results showed that the maximum TBBPA concentration in sediment was 518 ng/g in March 2008. It is almost the highest value than those ever reported anywhere in the world. In lake water, TBBPA level reached the maximum value of 4.87xa0μg/L in July. Tissue distributions of TBBPA in four fish species were similar, and the mean concentrations in the fish were in the range of 28.5–39.4 ng/g, much higher than those reported in Japan, Europe, and the United States. The maximum concentrations of TBBPA were found in kidneys where TBBPA concentration was positively correlated with fish size of Cyprinus carpio. Results demonstrated a widespread distribution of TBBPA in Lake Chaohu. The source was mainly inflow rivers near the cities. The distribution coefficient among water, fish, and sediment was 1:28:117. This indicated that sediment was the main repository for TBBPA within Lake Chaohu. Furthermore, TBBPA may pose a potential ecological risk in the lake during summer.

Development of freshwater aquatic life criteria for Tetrabromobisphenol A in China

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant. It has been detected in the environment and has shown to high toxicity to aquatic organisms. To date no aquatic life criteria for TBBPA have been proposed. This work compiled all literature toxicity data of TBBPA on Chinese aquatic species. Eight resident Chinese aquatic organisms were used in toxicity tests to supplement the existing toxicity data for TBBPA. Ten genera mean acute values and three genera mean chronic values to freshwater aquatic animals, as well as two genera toxicity values to aquatic plants were collected. A criterion maximum concentration of 0.1475 mg/L and a criterion continuous concentration of 0.0126 mg/L were derived based on these data, according to the U.S. Environmental Protection Agency guidelines. These criteria may be useful in risk assessment of TBBPA in the ambient water environment.

Development of PFOS and PFOA criteria for the protection of freshwater aquatic life in China.

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are two widely used perfluorinated compounds. They have been detected in various environmental media and have harmed aquatic life and systems. The toxic effects of PFOS and PFOA on freshwater organisms were explored with the goal of protecting aquatic ecosystems in this study. Data from acute toxicity tests using nine aquatic species and chronic toxicity tests using three species were analyzed, along with PFOS and PFOA toxicity data for representative Chinese aquatic biota that have been published in the Chinese and international literature. Using the method recommended by the United States Environmental Protection Agency (US EPA), the criterion maximum concentration (CMC) for PFOS was calculated to be 3.78 mg/L, and the criterion continuous concentration (CCC) was calculated to be 0.25mg/L. For PFOA, the CMC was calculated to be 45.54 mg/L, and the CCC was calculated to be 3.52 mg/L. The criteria derived in this study provide the scientific basis for development of water quality standards and aquatic ecosystem risk evaluation.

Effects of organic matter and submerged macrophytes on variations of alkaline phosphatase activity and phosphorus fractions in lake sediment.

Organic matter and submerged plants may affect internal phosphate loading in lake sediment. In this study, we investigated the changes of alkaline phosphatase activity (APA) and phosphorus (P) fractions in lake sediment by adding organic matter (0.0%, 0.5% and 1.0% of dry weight) and plant submerged plants under experimental conditions. Results indicated that the APA in sediments significant increased after 50 days incubation than at 7 days. The APA in the treatments by adding organic matter and submerged plants increased by 26.37%-61.78% than that of control after 7 days incubation, and increased by 1.00%-29.51% at 50 days, indicating both organic matter and submerged plants may remarkable affect APA in sediment, especially for the early stage of incubation. In addition, the soluble reactive P (SRP) concentrations of the overlying water increased significantly with increasing sediment organic matter, possibly related to increase of APA in sediment. However, the release of SRP was obvious restrained due to absorption of submerged plant. TP and P fraction in sediment decreased with increasing incubation time, but the decrease of TP content in sediment was mainly from NaOH-P and OP sources, but not from HCl-P and IP. Effects of organic matter and submerged plants on P fractions in sediment mainly occurred in NaOH-P and OP fractions. At the end of experiments, the contents of NaOH-P and OP in the treatments by adding organic matter and submerged plant decreased by 5.46%-20.47% and 7.87%-21.46%, respectively. These results indicated that the relative importance of organic matter and submerged plants during the release and transformation of P in lake sediment.

Multibiomarker responses upon exposure to tetrabromobisphenol A in the freshwater fish Carassius auratus

Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant. It has been released into aquatic environments, where it is toxic to aquatic organisms. In the present study, five enzymes, glutathione-S-transferase (GST), aspartate aminotransferase (AST), alanine aminotransferase (ALT), UDP-glucuronosyltransferase (UDPGT), and the antioxidant enzyme glutathione reductase (GR) in serum and liver of crucian carp (Carassius auratus) were selected for screening. These enzymes may be suitable for use as early warning indicators of chronic TBBPA exposure. UDPGT, AST, ALT, and GR activities in serum were found to be as more sensitive to TBBPA as those of the liver. When the concentration of TBBPA exceeded 0.50-0.71 mg/L for an exposure period of 32 days, GST, AST, ALT, and UDPGT activities cannot be restored to normal levels, suggesting that fish exposed to TBBPA above this threshold may incur irreversible damage. The activities of AST, ALT, and GR increased more significantly than GST and UDPGT at the lowest concentration of 0.35 mg/L. AST showed the strongest activity with respect to toxic kinetics, followed by ALT and GR. This remained true from day 4 of exposure to TBBPA to day 32. However, GR showed the clearest and most significant dose-effect relationship. This shows that each of these three enzymes can be used as a biomarker for early warning applications focusing on TBBPA pollution. AST and ALT are suitable for use in conventional monitoring of water quality in areas at risk for TBBPA pollution, and GR is more suitable for use in burst TBBPA pollution accidents where GR activity in fish would change with the TBBPA concentration of the flowing water.

Protective effects of puerarin against tetrabromobisphenol a‐induced apoptosis and cardiac developmental toxicity in zebrafish embryo‐larvae

Tetrabromobisphenol A (TBBPA), a brominated flame retardant, is detected commonly in aquatic environments, where it is thought to be highly toxic to the development of aquatic life. In this study, zebrafish embryos and larvae were used to investigate the protective effects of puerarin after exposure to TBBPA. Malformation, blood flow disorders, pericardial edema, and spawn coagulation rates increased, whereas survival decreased significantly after exposure to 0.5 and 1.0 mg L−1 TBBPA. The measured indices of morphological toxicity improved after treatment with puerarin. TBBPA also induced reactive oxygen species (ROS) production in a dose‐dependent manner. Acridine orange staining results revealed that TBBPA exposure caused cardiomyocyte apoptosis and induced the expression of three proapoptotic genes: P53, Bax, and Caspase9. In contrast, the expression of the antiapoptotic gene Bcl2 was down‐regulated. When genes related to cardiac development were assessed, the expression of Tbx1, Raldh2, and Bmp2b changed after exposure to the combination of TBBPA and puerarin. These results suggest that TBBPA induces cardiomyocyte apoptosis and ROS production, resulting in cardiac developmental toxicity in zebrafish embryos or larvae. Therefore, puerarin regulates the expression of cardiac developmental genes, such as Tbx1, Bmp2b, and Raldh2 by inhibiting ROS production, and subsequently modulates cardiac development after the exposure of zebrafish larvae to TBBPA.

Deriving freshwater safety thresholds for hexabromocyclododecane and comparison of toxicity of brominated flame retardants

Hexabromocyclododecane (HBCD) is a brominated flame retardant used throughout the world. It has been detected in various environmental media and has been shown toxic to aquatic life. The toxic effects of HBCD to aquatic organisms in Chinese freshwater ecosystems are discussed here. Experiments were conducted with nine types of acute toxicity testing and three types of chronic toxicity testing. After comparing a range of species sensitivity distribution models, the optimal model of Bull III was used to derive the safety thresholds for HBCD. The acute safety threshold and the chronic safety threshold of HBCD for Chinese freshwater organisms were found to be 2.32mg/L and 0.128mg/L, respectively. Both values were verified by the methods of the Netherlands and the United States. HBCD was found to be less toxic compared to other widely used brominated flame retardants. The present results provide valuable information for revision of the water quality standard of HBCD in China.

Ecological degeneration of the Erhai Lake and prevention measures

The water quality of Erhai Lake is good as a whole, but its decreasing trend is not optimistic; the water ecosystem of Erhai Lake has changed dramatically, showing an obvious degenerating trend. The main reasons for the ecosystem degeneration are as follows: inflow pollution load exceeding the water environmental capacity, not favorable water habitat for the propagation of submerged plants, and the weak management for the lake basin. To prevent the degeneration of Erhai ecosystem, two key problems should be solved: one is to reduce the inflow pollution load to prevent the increase of nitrogen and phosphorus concentrations in the overlying water; and the other is to implement the ecosystem regulation, namely improve the stability and biodiversity of Erhai ecosystem by habitat improvement, ecological restoration and ecological regulation. In terms of the preventive measures against the Erhai ecosystem degeneration, the pollution source control in combination with ecosystem regulation should be taken as the focus. Pollution source control, habitat improvement, ecological restoration, ecological regulation and watershed management should be emphasized simultaneously. To be specific, the key tasks for preventing Erhai ecosystem degeneration include five points namely, the reduction of pollution loading into lake, adjustment of ecological fishery, restoration of submerged vegetation, watershed integrated management, and emergency treatment of water blooms.

Chlorophyll ratio analysis of the responses of algae communities to light intensity in spring and summer in Lake Erhai

Algae biomass and community structure can reflect the current situation of a lake, especially in response to changes in light intensity. The relationship between chlorophyll a (Chl a) and chlorophyll b (Chl b) ratio and the proportion of Chlorophyta within the algae community were analyzed in this study. Results showed that light was more intense in August than in March. Algae density in August was greater than in March. The concentration of Chl a and b was influenced by light intensity level. In March, Microcystis and Kirchneriella sp dominated surface water, where the light intensity was over 216xa0μmolxa0m−2xa0s−1, Gloeocapsa, Dictyospaerium pulchellum, and Scenedesmus dominated intermediate water, where the light ranged from 36 to 216xa0μmolxa0m−2xa0s−1. Asterionella formosa Hassall and Mougeotia scalaris dominated near the bottom, where the light was below 36xa0μmolxa0m−2xa0s−1. In August, Microcystis and Selenastrum reinsch dominated surface water, where the light was above 18xa0μmolxa0m−2xa0s−1. Chroococcus, Chlorella, and Scendesmus quadricauda dominated intermediate water, where light ranged from 90 to 180xa0μmolxa0m−2xa0s−1. Anabaena spirioides and Pediastrum simplex dominated bottom water, where the light was below 90xa0μmolxa0m−2xa0s−1. According to the mean value of Chlorophyta density and algae cell density in three different water levels, the ratio of Chlorophyta and algae community declined from March to August, ranging from 12.35–21.41 to 4.28–11.19xa0%. The mean value ratio of Chl b and Chl a in three different water levels showed the same tendency from March to August, ranging from 18.05–21.77 to 15.15–17.44xa0%. These variations in chlorophyll ratio and Chlorophyta ratio indicated that the structure of the algae community structure was influenced by differences in light intensity.

Deriving aquatic life criteria for PBDEs in China and comparison of species sensitivity distribution with TBBPA and HBCD

Polybrominated diphenyl ethers (PBDEs) are important industrial brominated flame retardants. PBDEs have raised great concerns for their persistence, bioaccumulation, and harm to aquatic life and human health. Pentabromodiphenyl ether (PeBDE), octabromodiphenyl ether (OcBDE), and decabromodiphenyl ether (DeBDE) are three main commercial PBDEs congeners. In this study, published ecotoxicity data of these three PBDEs congeners for Chinese freshwater species were collected, and several acute and chronic toxicity tests for the three PBDEs congeners were performed. Using the derivation method for aquatic life criteria developed by the United States Environmental Protection Agency (USEPA), we determined that the criterion maximum concentration (CMC) for PeBDE, OcBDE and DeBDE for protection of freshwater organisms were 0.0492u202fmg/L, 0.197u202fmg/L and 0.239u202fmg/L, respectively. The criterion continuous concentration (CCC) for PeBDE, OcBDE and DeBDE were 0.0103u202fmg/L, 0.0224u202fmg/L and 0.0267u202fmg/L, respectively. The results provided a good reference for the derivation of PBDEs water quality criteria and a basis for ecological risk assessment of PBDEs. In addition, the results of species sensitivity distribution comparison showed that the toxicity rank of five brominated flame retardants was TBBPAu202f>u202fPeBDEu202f>u202fOcBDEu202f>u202fDeBDEu202f>u202fHBCD.