Net Degradation of Methyl Mercury in Alder Swamps

• Published in: Environmental science & technology 2012-12, Vol.46 (24), p.13144-13151
• Main Authors: Kronberg, Rose-Marie, Tjerngren, Ida, Drott, Andreas, Björn, Erik, Skyllberg, Ulf
• Format: Article
• Language: English
• Subjects: Alnus - metabolism; Applied sciences; Biodegradation, Environmental; Biological and physicochemical properties of pollutants. Interaction in the soil; Carbon - analysis; Creeks & streams; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Forest Science; Forestry; Measurement; Mercury; Methylation; Methylmercury Compounds - isolation & purification; Pollution; Pollution, environment geology; Seasons; Skogsvetenskap; Soil - chemistry; Soil and sediments pollution; Soil Pollutants - analysis; Soils; Sweden; Variance analysis; Wetlands
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/es303543k

Wetlands are generally considered to be sources of methyl mercury (MeHg) in northern temperate landscapes. However, a recent input-output mass balance study during 2007–2010 revealed a black alder (Alnus glutinosa) swamp in southern Sweden to be a consistent and significant MeHg sink, with a 30–60% loss of MeHg. The soil pool of MeHg varied substantially between years, but it always decreased with distance from the stream inlet to the swamp. The soil MeHg pool was significantly lower in the downstream as compared to the upstream half of the swamp (0.66 and 1.34 ng MeHg g–1 SOC–1 annual average–1, respectively, one-way ANOVA, p = 0.0006). In 2008 a significant decrease of %MeHg in soil was paralleled by a significant increase in potential demethylation rate constant (k d, p < 0.02 and p < 0.004, respectively). In contrast, the potential methylation rate constant (k m) was unrelated to distance (p = 0.3). Our results suggest that MeHg was net degraded in the Alnus swamp, and that it had a rapid and dynamic internal turnover of MeHg. Snapshot stream input-output measurements at eight additional Alnus glutinosa swamps in southern Sweden indicate that Alnus swamps in general are sinks for MeHg. Our findings have implications for forestry practices and landscape planning, and suggest that restored or preserved Alnus swamps may be used to mitigate MeHg produced in northern temperate landscapes.