北江中上游地表水和沉积物中PAHs和PCBs污染特征和风险评估

采用气相色谱-质谱法（GC-MS）测定了北江中上游流域地表水和沉积物样品中多环芳烃（PAHs）和多氯联苯（PCBs）类污染物的含量，分析了PAHs和PCBs的污染水平和空间分布，并评估了污染物的健康风险和生态风险.结果表明，16种PAHs单体在所有水样和沉积物样品中均被检出，检出范围分别为41.82~443.04 ng·L^-1和59.58~635.73 ng·g^-1，北江中上游PAHs的污染水平为中、轻度.水中PAHs以二环芳烃和三环芳烃为主，沉积物中以三环芳烃和四环芳烃为主.在水样中检出了17种PCBs，浓度范围0.81~287.50 ng·L^-1，以六氯联苯和七氯联苯为主；沉积物中检出了8种PCBs，含量范围0.13~3.96 ng·g^-1，以五氯联苯和七氯联苯为主.整个调查区域内地表水中PAHs和PCBs的终生致癌风险指数小于10^-4，处于中、低水平；非致癌风险指数均小于1，不存在非致癌风险.采用风险商值（RQ）法对地表水中污染物进行生态风险评价，研究区域内地表水中PAHs和PCBs生态风险总体处于中低风险水平，个别点位存在重度风险的污染物单体，值得引起重视.采用沉积物质量基准法（SQGs）对沉积物中污染物进行生态风险评估，沉积物中PAHs和PCBs均处于较低的生态风险水平.

Pollution Characteristics and Risk Assessment of PAHs and PCBs in Surface Water and Sediments in Middle and Upper Reaches of Beijiang River

The contents of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in surface water and sediment samples from the middle and upper reaches of Beijiang River basin were determined using gas chromatography-mass spectrometry (GC-MS). The pollution level and spatial distribution of PAHs and PCBs were analyzed, and the health and ecological risks of pollutants were evaluated. The results showed that 16 PAHs monomers were detected in all surface water and sediment samples, with detection ranges of 41.82-443.04 ng·L^-1 and 59.58-635.73 ng·g^-1, respectively. The pollution levels of PAHs in the middle and upper reaches of Beijiang River were medium and mild. PAHs in water were mainly composed of bicyclic aromatic hydrocarbons and tricyclic aromatic hydrocarbons, whereas tricyclic aromatic hydrocarbons and tetracyclic aromatic hydrocarbons were mainly in sediments. There were 17 monomers of PCBs detected in the water samples with concentrations in the range of 0.81-287.50 ng·L^-1, which mainly consisted of hexachlorobiphenyls and heptachlorobiphenyls. Eight monomers of PCBs were detected in sediments ranging from 0.13 to 3.96 ng·g^-1, which were mainly pentachlorobiphenyls and heptachlorobiphenyls. The lifetime carcinogenic risk index of PAHs and PCBs in surface water of the whole survey area was less than 10^-4, and the non-carcinogenic risk index was less than 1, indicating that the carcinogenic risk of PAHs and PCBs was at a medium and low level, and there was no non-carcinogenic risk in surface water. The risk quotients (RQ) method was used to evaluate the ecological risk of pollutants in surface water. The ecological risk of PAHs and PCBs in surface waters in the study area was generally at a low to moderate risk level, including individual points with the presence of heavily risky pollutants that deserve attention. The method of sediment quality guidelines (SQGs) was used to assess the ecological risk of pollutants in sediments. The results showed that PAHs and PCBs were at a low ecological risk level in sediments of Beijiang River.