Episodes of Elevated Methylmercury Concentrations in Prairie Streams

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• 作者：Steven J. Balogh ; Yabing Huang ; Heather J. Offerman ; Michael L. Meyer ; and D. Kent Johnson
• 刊名：Environmental Science & Technology
• 出版年：2002
• 出版时间：April 15, 2002
• 年：2002
• 卷：36
• 期：8
• 页码：1665 - 1670
• 全文大小：214K
• 年卷期：v.36,no.8(April 15, 2002)
• ISSN：1520-5851

文摘

Methylmercury (MeHg) and total mercury (THg) concentrations were determined weekly from late Marchthrough mid-December 2000 in unfiltered water samplesfrom two prairie streams in south-central Minnesota. TheLittle Cobb River and County Ditch 86 drain predominantlyagricultural watersheds, but riparian areas along much ofthe Little Cobb River are forested, whereas County Ditch86 is a utilitarian drainage waterway with grassed riparianareas. Episodes of elevated MeHg concentration (1.3 ng/L) were observed in both streams in early May during aperiod of algal bloom. Between late May and lateSeptember, MeHg concentrations varied between 0.05and 0.39 ng/L in the Little Cobb River and between 0.03 and0.29 ng/L in County Ditch 86. Precipitation was wellbelow average in August and September, and dischargein both streams ceased by late September. MeHgconcentrations in the Little Cobb River increased dramaticallyin early October after autumnal leaf fall, increasing from0.44 to 4.90 ng/L over a 5-week period. In contrast, MeHgconcentrations in County Ditch 86 varied between 0.22and 0.48 ng/L over the same time frame. The observeddifferences are thought to reflect differences in the amountsof litterfall entering the two streams. These results showthat algal bloom and leaf fall events can result in elevatedMeHg concentrations in surface waters, potentiallyleading to increased MeHg accumulation in fish.