Preliminary Study Of Polybrominated Diphenyl Ethers(PBDEs) In Aqueous Biota From Pearl River Estuary

Polybrominated diphenyl ethers(PBDEs) are one class of efficient flameretardants which are extensively used in a range of applications including textile, electronics and ornaments. PBDEs are now becoming the focus due to its frequent detection and high concentrations found in the environment. A previous study of PBDEs in sediment around the Pearl River Estuary indicated that sediment in this region was widely polluted. To investigate the pollution status of PBDEs in aqueous biota, firstly a method for PBDEs analysis was found in biota, then 90 biota samples(including five species fish, two species shrimps and one mantis shrimp) and 9 sediments were collected from Pearl River estuary and further analyzed for PBDEs. δ15N values for fish samples were measured to determine their trophic levels. Influences of biota's habit, metabolism and trophic level on its PBDEs concentrations and its accumulation characteristics were analyzed. The accumulation mechanisms of PBDEs was preliminarily studied using Biota-Sediment accumulation factors (BSAFs). Results are as follows:1. PBDEs were ubiquitous detected in aqueous biota collected from the Pearl River Estuary. The concentrations of 10 PBDEs (including BDE28, 47, 66, 99, 100, 153, 154, 85, 138, 183) in five fish species (large yellow croaker, silvery pomfret, flathead fish, robust tonguefish and bombay duck) were normalized to lipid content and ranged from 37.8 to 407.1 ng/g. Of the five fish species, bombay duck contained the highest PBDE concentration, followed by robust tonguefish and silvery pomfret, and the lowest concentration was found in large yellow croaker. Concentrations of 10 PBDEs in two shrimps (jinga shrimp, greasy-back shrimp) were in the range from 34.1 to 266.4 ng/g. PBDEs concentrations in mantis shrimp were between 95.9 and444.5 ng/g. The sum of 9 PBDEs (the same BDE congeners as above, excluding BDE85) were determined based on organic carbon and ranged between 9.88 and 39.0 ng/g. The detection frequencies of BDE 209 in large yellow croaker, silvery pomfret, flathead fish, robust tonguefish, bombay duck, jinga shrimp, greasy-back shrimp, and mantis shrimp were 69.2%, 60%, 17.6%, 25%, 44.4%, 30%, 60%, and 66.7%, respectively, and its concentrations were in the range from n.d to 623.5 ng/g, lipid, BDE209 concentrations were from 792.1 to 4137.0 ng/g, oc in sediments. Overall, concentrations of PBDEs in aqueous biota samples from Pearl River estuary were similar or slightly higher than those from other estuary worldwide, and lower than those from some lakes or rivers in Northern America.2. The profiles of 10 BDE congener in different analyzed biota samples were by and large the same: BDE47 was the main congener, the decreasing contributions of other individual BDE congeners to ￡PBDEs follow the sequence of BDE 100, BDE99 > BDE154, BDE153, BDE28, BDE66 > BDE85, BDE138, BDE183. However, the differences in the concentrations of BDE99 and BDE 100 in different biota species were also significant. Different contributions of BDE47, 99 and 183 to ￡PBDEs was the main profile difference between biota and sediment. The different profiles of BDEs in different biota were related to different bioaccumulation and metabolism abilities. Except ratios of BDE99/BDE100 were an indicator of metabolism ability of PBDEs in aqueous biota, in this studied region, ratios of BDE153/BDE154 may be another indicator.3. Stable Nitrogen isotopes (515N) were measured in five fish's tissue samples and the relationship between PBDEs concentrations and stable nitrogen isotopes was analyzed. The result showed that the relationship between PBDEs concentrations and stable nitrogen isotopes is not significant, which indicate that PBDEs concentrations in our study region may be not accumulated all by biomagnifications through food chain.4. Only weak or negative correlations were found between the PBDE concentrations and biota lengths, moderate or high positive correlations were found between the PBDEs levels and lipid contents for all the species. This indicated thePBDEs loads in biota from the Pearl River Estuary was mainly the result of bioconcentration, and some factors, such as habits, metabolism, exerted large influences on PBDEs concentrations, while, the influence of trophic transfer was small.5. In this study, some BDEs, such as BDE47, 99, 100, of small molecular weight, had larger BSAF values, which indicated their higher accumulation abilities;while some BDEs, such as BDE183 and BDE209, of large molecular weight, had smaller BSAF values, which showed their lower accumulation abilities. BSAFs for the five fish species (large yellow croaker, silvery pomfret, flathead fish, robust tonguefish, bombay duck) and the mantis shrimp generally increase from BDE 28 to BDE 100 and subsequently decline from BDE 100 to BDE 209. The distribution patterns of BSAFs are consistent with the prediction by a bioaccumulation model that the extent of accumulation of organic chemicals in biota increases with increasing log Kow at log Kow < 7 and then decreases with a further increase of log ￡ow > 7. The BSAF distribution for two benthic invertebrate species (jmga shrimp and greasy-back shrimp) was different from those of other biota species. The BSAF value was the highest for BDE 47, and decreased with increasing bromination. This difference suggests that the BSAF values for individual PBDE congeners could be species dependent.