涨落潮影响下长江口PAHs水-悬沙相间分配特征

Multiphase distribution of polycyclic aromatic hydrocarbons (PAHs) in Yangtze Estuary under the impacts of ebb and flow

通过长江口水体、悬沙中16种PAHs总体与单体含量特征采样分析,探讨涨落潮影响下PAHs的多相分配特征,并结合PAHs多相分配系数揭示其归趋行为.结果表明,涨落潮对不同环数PAHs的分配影响差异较大.DOC、水流对水相中溶解态PAHs含量分布影响较大,悬沙理化性质对于悬沙中结合态PAHs影响更大.低环PAHs主要以溶解相迁移,而高环PAHs则以颗粒相迁移.沉积物多次再悬浮能够降低水中溶解态PAHs含量,抑制沉积物中结合态PAHs释放.在涨落潮影响下和沉积物再悬浮过程中16种PAHs的lgKd大小次序均呈现一致性,即5,6环PAHs>4环PAHs>2,3环PAHs.在水-悬沙相间分配过程中,多环芳烃自身理化性质起主导作用,盐度、沉积物组成、水动力强度、水流速大小等因素也共同影响长江口PAHs多相分配作用.

Multiphase redistribution of 16 PAHs species were fully investigated to understand the fate of PAHs in the Yangtze estuary.The focus was mainly laid on the distribution discrepancy of total and individual PAHs under the influence of tidal,with supplemented analysis of the distribution coefficient of PAHs during the sediment resuspension process.The results showed that the impacts of tidal fluctuation on distributions of different types of PAHs in the same section were quite different.Dissolved PAHs in water phase were greater affected by DOC and water currents,while for the bound PAHs on the suspended particles,the effect of physicochemical properties of suspended particles was higher.The main reason was that low molecular weight PAHs were transported mainly in form of dissolved phase while high molecular weight PAHs were mainly in form of particle phase.Particle resuspensions could decrease the concentration of dissolved PAHs in water phase and inhibit the release of PAHs from the sediments.However,the order of lgK_d of different ring PAHs was 5,6 rings>4 rings>2,3 rings under both the influence of fluctuating tide and sediment resuspension process.This indicated that the physical and chemical properties of PAHs played the main roles in their allocation process,while salinity,sediment composition,hydrodynamics and other factors affected the multiphase distributions of PAHs in the Yangtze estuary together.