Production and Loss of Methylmercury and Loss of Total Mercury from Boreal Forest Catchments Containing Different Types of Wetlands
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- 作者：Vincent L. St. Louis ; John W. M. Rudd ; Carol A. Kelly ; Ken G. Beaty ; Robert J. Flett ; and Nigel T. Roulet
- 刊名：Environmental Science & Technology
- 出版年：1996
- 出版时间：September 1996
- 年：1996
- 卷：30
- 期：9
- 页码：2719 - 2729
- 全文大小：585K
- 年卷期：v.30,no.9(September 1996)
- ISSN：1520-5851
文摘
Four terrestrial boreal forest catchments containingdifferent types of wetlands were studied todetermine their strength as sources or sinks ofmethylmercury (MeHg) and total mercury (THg) todownstream ecosystems and to determine if patternsseen in one year were consistent over several years.All catchments were sinks for THg. The wetlandtype, percentage wetland area (0-25%), or annualwater yield did not appear to have a consistent effecton the magnitude of this retention. Wetland areasof the catchments were always net sources of MeHg.Unlike for THg, there were large and consistentdifferences in the source strength among wetlandtypes for MeHg. These differences appeared to berelated to differences in the internal hydrology ofthe wetlands. All types of wetlands were greatersources of MeHg during years of high water yield,but even during years of low flow all wetland typeswere sources of MeHg. Thus, we conclude thatwetlands are important sites of MeHg production inboreal ecosystems on the long term. Upland areasof catchments were consistently sinks for MeHg, andso whole catchment sink/source values were stronglyaffected by the percentage of wetland areas withina catchment. Mass balance estimates of MeHginput from wetland areas to a lake indicate that theannual input of MeHg from wetlands is larger thanthe annual uptake of Hg by fish and is similar to theamount of MeHg produced in the lake. Becauseof the predictable patterns between terrestrial catchments in their strength as sources or sinks of MeHg,it is possible to model inputs of MeHg from lakecatchments with knowledge of the percentage wetlandarea in a catchment, the type of wetland containedin a catchment, and the annual water yield of acatchment.