四面山大洪湖底泥/水界面汞的迁移转化规律

Migration and Transformation of Mercury at Sediment-Water Interface of the Dahong Lake Reservoir in the Simian Mountains

森林生态系统的汞产量可以用森林湖泊或水库的动态变化来表征.而且,下游汞浓度的变化也可以在一定程度上反映森林生态系统汞的输出.通过对四面山大洪湖上游、中游、下游丰水期与枯水期汞的分布与沉积物剖面的分析发现:大洪湖上覆水中总汞浓度在丰水期显著增加(丰水期平均值4. 33 ng·L^(-1),枯水期1. 85 ng·L^(-1)),在下游尤为明显,其总汞和甲基汞的含量明显高于其他类型湖泊,但小于受到污染的湖泊,说明四面山常绿阔叶林具有一定"汞源"的特征,同时沉积物也是大洪湖上覆水中甲基汞和无机汞的输入源;甲基化过程主要发生在沉积物的表层,丰水期时甲基化过程更活跃;在丰水期时,更有利于汞和甲基汞从沉积物固相进入沉积物液相,从而进入上覆水中.

The mercury production in forest ecosystems can be characterized by dynamic changes in forest lakes or reservoirs. Moreover, changes in the downstream mercury concentrations can also reflect the mercury output from forest ecosystems. Based on the analysis of distribution patterns and sediment profiles of mercury in DH1, DH2, DH3, and DH4 during the wet and dry seasons in the Dahong Lake Reservoir, the total mercury concentration of the Dahong Lake Reservoir increases significantly during the wet season （ the average of the wet season is 4.33 ng·L^-1 , the average of the dry season is 1.85 ng·L^-1 ） , especially in the downstream. The content of total mercury and methylmercury in the water column of the Dahong Lake Reservoir is significantly higher than that of background lake levels, but it is much lower than that of contaminated lakes, indicating that evergreen broad-leaved forest in the Simian Mountains has characteristics of Hg sources and the sediments are also sources of methylmercury and inorganic mercury in the water column of the Dahong Lake Reservoir. The methylation process mainly occurs in the surface layer of sediments and the methylation process is more active during the wet season. During the wet season, it is more favorable for mercury and methylmercury to enter the sediment liquid phase from the sediment solid phase and thus the water column.