三峡水库动态水位下有机锡的多介质归趋模拟

Simulation of multimedia transfer and fate of organotins in the aquatic environment of the Three Gorges Reservoir under dynamic water level

为探究三峡水库(TGR)动态水位下水环境中有机锡(OTs)的多介质迁移与归趋行为,构建了动态水位下OTs的IV级多介质逸度模型,对大气相、水相、沉积物相及鱼相中三丁基锡(TBT)和三苯基锡(TPT)浓度的动态分布进行了模拟,并依据实测值进行了验证,计算了TBT和TPT在各相间的迁移通量(N)和残留质量,探讨了其主要的迁移途径和归趋行为,并进行了参数敏感性和模型不确定性分析.结果表明,实测浓度与模拟浓度的吻合度较高,TGR水环境中OTs浓度受水位变化影响较大.TBT和TPT的N值随水位变化明显,呈现与水位涨落相反的变化趋势,与坝前水位、入库流量和降雨量的变化相关.平流输入输出、沉积物沉降、掩埋、再悬浮、水相降解和平流输入输出、鱼-水两相迁移是TBT和TPT的主要迁移过程,平流输出与降解是两者主要的损失途径.较大的沉积物输入净迁移通量(N N)表明沉积物相是TBT和TPT重要的储藏库,易在鱼相富集也是TPT的重要归宿.模拟期内TBT和TPT在沉积物相的残留质量最高,分别占总残留量的89%和84%,其在沉积物相、水相、鱼相及大气相的分配比例分别为89.17%、10.81%、0.04‰、0.19‰和83.81%、14.51%、1.68%、1.15×10^-5‰.平流输入浓度(COW)和速率(GOW)对4个环境相TBT和TPT的敏感性系数(SC)>0.6,产生显著正影响,TBT和TPT模拟浓度的变异系数(CV)≤0.15,模型模拟的效果较好.

To study the transfer and fate of organotins(OTs)in the aquatic environment under dynamic water level of the Three Gorges Reservoir(TGR),a level IV multimedia fugacity model was constructed to simulate the dynamic distributions of tributyltin(TBT)and triphenyltin(TPT)concentrations in air,water,sediment and fish and compared to monitored data for validation purpose.The transfer flux(N)and the residual mass of TBT and TPT in each phase were calculated,and the main transfer routes and fate behaviors were determined,and the sensitivity of input parameters and the uncertainty of output results were analyzed.Results show that the simulated concentrations can fit the monitored concentrations well,and are significantly affected by the hydrodynamic conditions of TGR.The N of TBT and TPT changes obviously with the water level,showing the opposite trend with the fluctuation of water level,which is related to the change of water level,inflow and rainfall.Advection process,sedimentation,burial,resuspension,aqueous phase degradation and advection process,fish-water transfer are the main routes of TBT and TPT,and advection output and degradation are the main loss pathways of TBT and TPT.Large sediment input net transfer flux(NN)indicated that sediment is an important reservoir for TBT and TPT,and easy to enrich in fish is also a momentous destination of TPT.During the simulation period,the biggest residual mass of TBT and TPT was obtained in sediment,and the distribution ratios in sediment,water,fish and air were 89.17%,10.81%,0.04‰,0.19‰and 83.81%,14.51%,1.68%,1.15×10^-5‰,respectively.The advection input concentration(COW)and flow(GOW)has a significant positive effect on both TBT and TPT in the four phases(SC>0.6).The coefficient of variation(CV)of the TBT and TPT simulated concentrations is≤0.15,indicated a good simulation result.