Lee Y H, Bishop K H, Munthe J
Swedish Environmental Research Institute, Gothenburg.
Sci Total Environ. 2000 Oct 9;260(1-3):11-20. doi: 10.1016/s0048-9697(00)00538-6.
Previous studies at the Svartberget catchment in northern Sweden have identified potential terrestrial sources of methylmercury (MeHg) and total mercury (THg) in runoff as well as processes controlling MeHg/Hg transfers from soil to runoff water. This paper considers whether the concepts based on a few seasons of observations are consistent with catchment budgets of MeHg/THg over half a decade. Inter-annual and seasonal variations in the input and output fluxes of THg/MeHg, in open field wet deposition (OF), litterfall (LF) and runoff water are evaluated together with more recently measured concentrations that include the throughfall water (TF) data. The input and output flux data of THg and MeHg from the Svartberget catchment are also compared to those from the Gårdsjön Catchment. The average annual MeHg input fluxes in OF, TF and LF are 0.08, 0.17 and 0.3 g km(-2) year(-1), respectively. The comparable inputs for THg are 7, 15 and 17 g km(-2) year(-1). Thus, LF is as important as TF for THg inputs, while LF is twice as important as TF for MeHg inputs. The annual output flux of MeHg varied between 0.05 and 0.14 g km(-2) year(-1). The annual output flux of THg varied between 1 and 3.4 g km(-2) year(-1). The large inter-annual variations in catchment output did not follow the smaller variations in atmospheric input. This suggests that changes in climate can effect terrestrial outputs of THg/MeHg to surface water more than atmospheric deposition. These data do not contradict the earlier findings that it is the hydrological and biogeochemical processes in the riparian zone that have a central role in determining the amount of MeHg reaching surface waters from forested catchments. The juxtaposition of major flow paths and organic-rich soils in the riparian zone may create the locations of most importance for net MeHg production, runoff export and a larger pool of MeHg.
此前在瑞典北部斯瓦特贝里集水区开展的研究，已确定了径流中甲基汞（MeHg）和总汞（THg）的潜在陆地来源，以及控制MeHg/Hg从土壤转移至径流水中的过程。本文探讨基于几个季节观测得出的概念，是否与该集水区在五年间的MeHg/THg收支情况相符。同时评估了THg/MeHg在露天场地湿沉降（OF）、凋落物（LF）和径流水中输入通量与输出通量的年际变化和季节变化，以及最近测量的浓度，其中包括穿透降水（TF）数据。还将斯瓦特贝里集水区THg和MeHg的输入通量与输出通量数据，与加德湖集水区的数据进行了比较。OF、TF和LF中MeHg的年均输入通量分别为0.08、0.17和0.3 g km⁻² 年⁻¹。THg的可比输入量分别为7、15和17 g km⁻² 年⁻¹。因此，LF对THg输入而言与TF同样重要，而LF对MeHg输入而言的重要性是TF的两倍。MeHg的年输出通量在0.05至0.14 g km⁻² 年⁻¹之间变化。THg的年输出通量在1至3.4 g km⁻² 年⁻¹之间变化。集水区输出的较大年际变化并未遵循大气输入中的较小变化。这表明，气候的变化对THg/MeHg从陆地向地表水的输出影响，可能超过对大气沉降的影响。这些数据与早期研究结果并不矛盾，即河岸带的水文和生物地球化学过程在决定森林集水区进入地表水的MeHg量方面起着核心作用。河岸带主要水流路径与富含有机物土壤的并置，可能形成对净MeHg产生、径流输出以及更大MeHg库最为重要的位置。
