| Liaohe River is an important source of drinking water, industrial water and agriculture water in the northeast of China. In recent years, the water quality has been deteriorated seriously and the ecological environment has been under significant stress due to the rapid population growth and explosive increase in industrial and agricultural activities. Routine environmental monitoring shows that Liaohe River was subject to severe pollution by organics. Persistent organic pollutants (POPs) have attracted a significant amount of attention in recent years, due to their persistent, bio-accumulative, carcinogenic and mutagenic properties.The aim of this study was to determine the spatial and temporal distribution, composition, partitioning behavior of four types of POPs, including polycyclic aromatic hydrocarbons (PAHs), perfluorinated compounds (PFCs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the water and surface sediment in Liaohe River. Their source information and potential risks were discussed as well. The primary results were as follows:(1) Sixteen US EPA priority PAHs were detected in the surface water and sediments from Liaohe River in 2012, with the concentration of 94.8-2931.6 ng/L in water and 54.03-295635.17 ng/g in sediments. For the spatial distribution, Taizi River and Daliao River were more polluted than Hun River and main stream of Liaohe River. Low molecular compounds exhibited higher concentration than the high molecular compounds in both water and sediment. PAHs in both water and sediments were mainly from the combustion of coal, grass, biomass and pertroleum, by diagnostic ratios and clustering analysis. Principal component analysis/multiple linear regression (PCA/MLR) indicated that coal combustion and vehicle emission contributed 60%and 40% to the total sources respectively. Positive matrix factorization (PMF) showed that PAHs in sediments originated from coal combustion, vehicle emission and coke oven source, with contributions of 58%,25%,18% in dry season and 63%,19%,18% in wet season, respectively. ME-2 model apportioned the coal combustion, vehicle emission, coke oven source and biomass combustion, with the contributions of 53%,20%,13%,13%(dry season) and 50%,19%,15%,16% (wet season), respectively. The species sensitivity distribution (SSD) method was used to evaluate the ecological risks of PAHs in surface water to aquatic organisms. Anthracene (Ant) showed the largest ecological risk, followed by pyrene (Pyr) and fluoranthene (Fla). PAHs in the sediments of Liaohe River showed low-moderate risk to the aquatic organisms.(2) PFCs concentration ranged from 0.38 to 127.88 ng/L, and 1.72-10.44 ng/g in water and sediments, respectively. The contamination concentration in water followed the order of Daliao River> main stream of Liaohe River> Hun River> Taizi River. As well, PFCs concentration in sediments from Hun River and Daliao River were higher than those in Liao River and Taizi River. Perfluorooctanoic acid (PFOA) had the highest concentration and detection frequency in both water and sediments, with the proportition of 39.63% in water and 28.03% in sediments. Long chain PFCs homologues showed higher concentration and detection frequency than short chain compounds in sedimens, in comparison to the surface water. The organic carbon normalized partition coefficients (Koc) was calculated to study the partition behavior of PFCs between water and sediments, with the logKoc value ranging from 2.46 to 4.29, logKa ranging from 1.58 to 3.14. Relationships between the water quality parameters (T, DO, conductivity, TDS, salinity, ORP and pH) and koc values of PFCs were also explored in the present study. The results showed that koc of PFCs were significantly correlated with conductivity, TDS, salinity, DO, and pH. The main sources of PFCs identified from diagnostic ratios were emission of manufacturing processes and precursors degradation. The levels of perfluorooctanoic acid and perfluorooctane sulfonate in Liaohe River would not cause immediate health impact through the intake of the water, but PFOA in some sites in the study area may exert adverse effects on the aquatic ecosystem.(3) Total concentration of thirty-three polychlorinated biphenyls (PCBs) in sediments ranged from 4.92 to 179.61 ng/g, with an average value of 39.17 ng/g. PCBs in the sediments were predominated by tri-and tetra-CBs, followed by penta-, hexa-and deca-CBs. PCBs in sediments showed higher concentrations in wet season than dry season, ranging from 4.92-76.86 ng/g in dry season and 11.69-179.61 ng/g in wet season, respectively. The risk assessment showed that PCBs exerted low-moderate effect on the aquatic ecosystem. PCBs in sediment were mainly from commercial mixtures.(4) The total concentration of eight polybrominated diphenyl ethers ranged from 0.17 to 13.73 ng/g in the sediment of Liaohe River. Results showed that PBDEs levels were higher in wet season than in dry season. BDE 209 was the predominant compound. PBDEs in sediment were from the use of penta-, octa- and deca-BDEs commercial mixtures and degradation of high brominated diphenyl ethers. |
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