| Hydrophobic organic compounds (HOCs), such as polybrominated diphenyl ethers, organochlorine pesticides, and pyrethroids, are a class of most widely detected organic contaminants in the environment. Due to their strong affinity for organic matter, HOCs tend to be absorbed by soil, sediment, solid particles and accumulated in biota. Therefore, a good understanding about their behaviors and fate in the environment will help us to make an accurate prediction for their risk assessment.Salton Sea in California, US, is an inland lake with elevated concentrations of agriculture-related chemicals in water and sediment since 1960s. For a better understanding about the eventual environmental fate of HOCs, in this paper, Salton Sea was selected as a study model to give a vast view about the occurrence and transport of organochlorine pesticides (OCPs) and pyrethroids. The results indicated notable existences of OCPs in sediments from Salton Sea with mean concentrations of 3-30 ng g-1 and the maximum concentration of 109 ng g-1. Derivatives/isomers of DDT (DF=100%) were the main OCPs and bifenthrin (DF=90%) appears to be the dominant pyrethroid. The pesticide pollution pattern was demonstrated by concentration-based-Kriging contour map model which was built based on geo-statistical analysis and traditional statistical analysis. From this model, significantly higher concentrations coulde be visually observed in samples from Alamo River than from New River, in air-exposed samples than in submerged samples and in surface sediment than in sub-surface sediments. To assess the potential risks to Salton Sea-dependent habitants, the concentration data for major contaminants was compared with sediment quality guidelines like effect-rang low (ERL) and threshold effect concentrations (TEC) and samples were frequently found with exceeding ERL/TEL for DDEs, DDTs and chlordane. The result hints that further safety assessment is necessary when constructing the species conservation habitat at Salton Sea. The partition coefficients Kd and KDOC are important parameters for predicting the environmental behaviors and fate of HOCs. However accurate determination of Kd and KDOC becomes increasingly difficult as Kow increases because HOCs with large log Kow undergo extensive sorption not only to particulate organic matter, but also to colloids such as dissolved organic carbon. In this study, the automated solid phase microextraction method was developed to get the freely dissolved concentration (Cw-SPME) and was further combined with the traditional liquid-liquid extraction to get the partition coefficient for main PBDEs in environment. Obvious underestimation of water sediment partition coefficient Kd values was observed when measured by LLE (Kd values were 1.2-106.3-fold underestimated comparing to SPME). The organic carbon normialized sorption coefficient log Koc were reported to be 4.95-6.13, 5.77-6.44,5.57-6.40,6.19-6.92,5.77-6.70,6.19-7.30,6.10-7.24 and 6.40-7.52 for BDE-28,47,66,99,100,153,154 and 183. The corresponding log KDOC were reported to be 5.81-6.81,5.48-6.19,6.05-6.78,5.10-6.31,6.08-6.99,6.43-7.24, 6.35-7.20 and 6.60-8.02. Great log KDOC values were derived from the SPME measurements, suggesting a strong tendency for PBDEs to complex with DOC. Results from this study showed that PBDE congeners have larger sorption coefficients than would be measured by the conventional method. The high affinity to DOC also means a potential for DOC-facilitated transport, thus extending the range of PBDE movement in environmental compartments such as surface streams.The degradation of a novel pyrimidynyloxybenzoic herbicide ZJ0273, (propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate) was studied in flasks simulating flooded field conditions using three representative field soils. The degradation half-life (T1/2) values were calculated to be 63.7,35.1 and 49.2 days for acidic, neutral and alkaline soils respectively. The metabolites of ZJ0273 formed during degradation were identified using various analytical techniques, viz., liquid scintillation counting (LSC), high performance liquid chromatography (HPLC) and liquid chromatography-mass spectroscopy (LC-MS/MS). Five metabolites were found and identified as 4-(2-(4,6-dimethoxypyrimidin-2-yloxy) benzylamino)benzoic acid (Ml),4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzamido)benzoic acid (M2), 2-(4,6-dimethoxypyrimidin-2-yloxy)benzoic acid (M3),2-(4-hydroxy-6-methoxy pyrimidin-2-yloxy)benzoic acid (M4) and 4,6-dimethoxypyrimidin-2-ol (M5). Two degradation pathways were concluded form the experimental data:a) The degradation of ZJ0273 was initiated by ester hydrolysis to form Ml, and then the phenyl ring (A ring) was cleaved from M1 to form M2, and then M2 was transformed to M3 through hydroxylation, after which M3 was demethylated to M4;b) The propyl group in the parent compound was broken to form M1 and then Ml was further carbonylated to M2. The M2 was degraded into M3, and then further cleaved into M5.c) The degradation of ZJ0273 was initiated by ester hydrolysis to form M1, and then the phenyl ring (A ring) was cleaved from M1 to form M3, which was further demethylated and form M4;d) The propyl group in the parent compound was broken to form M1 and then M1 was further carbonylated cleaved to form M3 and then further cleaved into M5.An ourdoor experiment was further conducted to simulate the transportation and residue of ZJ0273 in agro-ecosystem. The results showed that ZJ0273 has weak leaching ability in soils and about 90% of the induced amount was remained in the surface 0-10cm soil at 120 d after chemical treatment (DAT). ZJ0273 has weak transportation in the oil rape seeds and more than 95% of the induced amount was remain in the labeled leave at 120 DAT. Less than 1% was transported to the root, stem and seed in matured rape body, suggesting a low dietary exposure for humans.
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