The concentrations of 18 polycyclic aromatic hydrocarbons （PAHs） in surface sediments of the Liangtanhe River, a typical secondary tributary in the reservoir area of the Three Gorges project, were determined individually and their distributions and pollution sources were analyzed. The results showed that the total concentrations of 18 PAHs ranged in 198.5 -4349 ng/g- dw （dry matter） , with a mean value and a med-value of 1441 and 1160 ng/g - dw respectively. Compared with the pollution level of sediments in areas else, that of the Liangtanhe River was medium low. Generally, the pollution of tributaries were more serious than that of the main stream and the right tributary flowing through a town was polluted more seriously than the left tributary and the mainstream flowing rural area. Most of the samples were polluted by PAHs with 4 - 6 benzene rings. PAHs The result of analyzing the PAHs sources showed that the PAHs in the surface sediment mainly sourced from incomplete combustion of fossil fuel and biomass. The toxic equivalent factor （TEF） and mean value of benzopyrene in the sediment were 39.38 - 384. 37 ngTEQ/g and 110. 94 ngTEQ/g respectively. The result of ecological assessment showed that the sediment PAHs of the sample R3 and R4 from the right tributary had negative biological effect, of which the high risk of R4 probably had something to do with the pollution in the Baishiyi Airport nearby.%本文表征了三峡库区典型次级支流（梁滩河）表层沉积物中18种多环芳烃（PAHs）的浓度,并对其分布特征和污染来源进行了探讨。18种PAHs的总浓度（∑18 PAHs）范围为198.5～4349 ng/g-dw（干重）,平均浓度为1441ng/g,中值为1160 ng/g。与其他地区沉积物污染情况相比,梁滩河沉积物中PAHs浓度处于中等偏低的污染程度,支流污染程显著高于干流,流经城镇的右支污染程度显著高于流经农村或人口较少的左支和主干流。大部分采样点以高环（4～6环）PAHs污染为主。PAHs源解析结果表明,梁滩河表层沉积物中PAHs污染以燃烧源为主,主要源于化石燃料和生物质的不完全燃烧。沉积物中苯并[a]芘的毒性当量因子（TEF）值为39.38～384.37 ngTEQ/g,平均值110.94 ngTEQ/g。生态风险评价的结果表明,右支流的两个采样点R3和R4点沉积物中PAHs可能存在生物负效应影响,R4点的高风险可能与附近白市驿机场污染有关。
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