Persistent Organic Pollutants Passed Water Section At Gaoyao Hydrological Station Of The Xijiang River

"Water is the source of the life", With the development of agriculture and industry, the progress of science and technology, large amount of toxic chemical compounds has been introduced to environment in Pearl River Delta. The quality of water is being deteriorated at very fast rate. The regional water pollution has thus become a key factor which hinders the development of the economy and society in this region.Extensive studies have attached importance to persistent organic pollutants (POPs), due to their ubiquitous, persistence, bioaccumulation and carcinogenic, mutagenic and toxic effects. They can undergo long-range atmospheric transport and can be deposited into aquatic systems and cause environmental damage.The Xijiang River is the major tributary of the Pearl River that is the third largest river in China. The Xijiang River is 2214 km long and has a catchment area of 3.53×10⁵km² . It discharges 2.38×10¹¹km³ of fresh water to the sea annually, which accounts for 70.8% of total runoff of the Pearl River. The Xijiang River is an important source of water for agricultural and industry activities and also serve as a supplier of drinking water for several counties and cities.In this thesis, the distribution, concentration and load of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs),polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides(OCPs) in the dissolved phase and suspended particle matter (SPM) phase were determined in water body on Gaoyao Station of the Xijiang River. Several results were summarized as following:The characteristics of PCDD/Fs The PCDD/Fs concentrations in the dissolved phase and SPM phase ranged from 1.567～8.008 pg/L and 569.4～4279.6 pg/g, respectively. The composition and distribution of PCDD/Fs in the Xijiang River varied seasonally. Higher PCDD/Fs concentrations occurred in summer; lower in winter. Compared to PCDD/Fs concentrations in other rivers of the world, the Xijiang River exhibited lower concentrations. The PCDD/Fs in the Xijiang River derived from soil runoff, atmospheric deposition, and domestic or industry sewage, although those from soil were dominant. The proportion contributed by the three sources varied temporally due to large seasonal differences in water discharge. A sufficiently good correlation existed between lgK_oc and lgK_ow for 2, 3, 7, 8-substituted PCDD/Fs congeners. The annual loadings for total PCDD/Fs, 2, 3, 7, 8-chlorine substituted PCDD/Fs, and I-TEQ were 8.55 kg, 7.74 kg and 0.026 kg, respectively.The characteristics of PAHs Composition and distribution exhibit temporal difference of PAHs because of being influenced by the discharge of the Xijiang River in the different seasons. Concentration of PAHs in water samples ranged from 30.96 ng/L to 357.90 ng/L with a mean value of 150.14 ng/L. And the total concentration of SPM varied between 292.54 ng/g and 873.65 ng/g (mean 574.32 ng/g). 2-ring (Nap) and 3-ring (Ace, Acy, Flu, Phe, and Ant) were abundant to the total PAHs in water phase. In contrast, 3-ring and 4-ring (Fluo, Pyr, BaA, and Chry) were important compounds in SPM samples. The ratios of PAHs indicated in the Xijiang River, the primary source of PAHs was biomass combustion. A sufficiently good correlation existed between lgK_oc and lgK_ow. The annual loading of Ant, BaA, BaP, BbF, BkF, IncdP, DbahA, Chry and total PAHs were 1019, 1028, 693, 723, 1054, 906, 867, 1373 and 48904 kg, respectively. The annual toxic BaP equivalent quantity (TEQ^carc) for the each of seven PAHs and total of them were 103, 693, 72, 11, 91, 867, 1.4, and 1838 kg, respectively.The characteristics of OCPs The OCPs concentrations in the dissolved phase and SPM phase ranged from 2.28～10.21 ng/L and 20.29～58.74 ng/g, respectively. Compared with other reported results, the total concentration of the OCPs in the Xijiang River were much lower. From the characteristics of HCHs and DDTs compositions, the main sources of HCHs were β-HCH, and the use of dicofol might be the new source of DDT. A sufficiently good correlation existed between lgK_oc and lgK_ow. The estimated annual loadings of HCHs, DDTs and total OCPs were 272.3, 164.6, 1245.3 kg, respectively.