Wang De-Gao, Alaee Mehran, Byer Jonathan, Liu Yong-Jun, Tian Chong-Guo
Department of Environmental Science and Engineering, Dalian Maritime University, Dalian, P R China.
J Environ Monit. 2011 Jun;13(6):1589-96. doi: 10.1039/c0em00731e. Epub 2011 May 9.
Diffusion is an important process for sediment-water exchange and plays a vital role in controlling water quality. Fugacity fraction (ff) was used to estimate the sediment-water diffusion of polycyclic aromatic hydrocarbons (PAHs) between seawater and surficial sediment. A total of 33 surface sediment and sea water samples were collected concurrently from the northeast coastal area in China and 25 PAHs were analyzed including the alkylated and chlorated PAHs. Fugacity fraction was calculated based on the PAH concentrations in water and sediment, octanol-water partition coefficient of PAHs, organic matter content in sediment, and density of sediment. The calculated results showed that ff increased with decreasing molecular weight of PAHs. The low molecular weight PAHs (2-3 rings) transferred from sediment to water and the sediment acted as a secondary source to the water. The medium molecular weight PAHs (4-5 rings) were close to the sediment-water equilibrium and the transfer tendency shifted between sediment and water. The high molecular weight PAHs (5-6 rings) transferred from water into sediment and the sediment acted as a sink. Soot carbon and the difference of PAH concentrations between sediment and water were found to be important factors affecting the sediment-water diffusion. This study provided new insight into the process of sediment-water diffusion, which has a great influence on the quality of water, especially in severely-polluted sediment areas.
扩散是沉积物 - 水交换的一个重要过程，在控制水质方面起着至关重要的作用。逸度分数（ff）被用于估算多环芳烃（PAHs）在海水与表层沉积物之间的沉积物 - 水扩散情况。在中国东北沿海地区同时采集了33个表层沉积物和海水样本，并分析了包括烷基化和氯化多环芳烃在内的25种多环芳烃。逸度分数是根据水中和沉积物中的多环芳烃浓度、多环芳烃的正辛醇 - 水分配系数、沉积物中的有机质含量以及沉积物密度计算得出的。计算结果表明，逸度分数随多环芳烃分子量的降低而增加。低分子量多环芳烃（2 - 3环）从沉积物转移到水中，沉积物成为水体的次要来源。中等分子量多环芳烃（4 - 5环）接近沉积物 - 水平衡，转移趋势在沉积物和水之间变化。高分子量多环芳烃（5 - 6环）从水转移到沉积物中，沉积物起到汇的作用。发现烟灰碳以及沉积物和水之间多环芳烃浓度的差异是影响沉积物 - 水扩散的重要因素。本研究为沉积物 - 水扩散过程提供了新的见解，该过程对水质有很大影响，尤其是在污染严重的沉积物区域。
