Physical Controls on Total and Methylmercury Concentrations in Streams and Lakes of the Northeastern USA

Abstract

The physical factors controlling total mercury (HgT) and methylmercury (MeHg) concentrations in lakes and streams of northeastern USA were assessed in a regional data set containing 693 HgT and 385 corresponding MeHg concentrations in surface waters. Multiple regression models using watershed characteristics and climatic variables explained 38% or less of the variance in HgT and MeHg. Land cover percentages and soil permeability generally provided modest predictive power. Percent wetlands alone explained 19% of the variance in MeHg in streams at low-flow, and it was the only significant (p < 0.02) predictor for MeHg in lakes, albeit explaining only 7% of the variance. When stream discharge was added as a variable it became the dominant predictor for HgT in streams, improving the model r2 from 0.19 to 0.38. Stream discharge improved the MeHg model more modestly, from r2 of 0.25 to 0.33. Methylation efficiency (MeHg/HgT) was modeled well (r2 of 0.78) when a seasonal term was incorporated (sine wave with annual period). Physical models explained 18% of the variance in fish Hg concentrations in 134 lakes and 55% in 20 reservoirs. Our results highlight the important role of seasonality and short-term hydrologic changes to the delivery of Hg to water bodies.

Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs

“…Unfiltered water for ammonia, nitrate ϩ nitrite, and total phosphorus was kept cool until analysis. Water was filtered for SO 4 2Ϫ , DOC, total dissolved nitrogen, and total dissolved phosphorus. Whatman (Maidstone, England) GF/F filters for chlorophyll a and water for nitrogen analyses were frozen.…”

“…For example, inputs of mercury (Hg) to a waterbody can be influenced by atmospheric deposition (2), geology (3), soil and vegetation type (4), and large precipitation events (5). Increases in water temperature, dissolved organic carbon (DOC), and sulfate (SO 4 2Ϫ ) and declines in pH can increase in-lake Hg methylation (6).…”

Specific ultra-violet absorbance as an indicator of mercury sources in an Adirondack River basin

“…Basin percent open water area is a commonly applied metric in studies of spatial controls on Hg cycling (Hurley et al 1995;Shanley et al 2005), and was explored here for inclusion in multiple regression models. An alternative to this metric, the open water index (OWI) that accounts for the proportion of basin drainage area that transits each open water body [0.025 km 2 was also calculated (described in greater detail by Burns et al 2012).…”

Mercury dynamics and transport in two Adirondack Lakes

“…The fraction of Hg present as MeHg (% MeHg) was substantially greater at the inlets of Sunday Lake (10.4 6 4.8%) compared to Arbutus Lake (4.7 6 3.3%). Concentrations of MeHg in catchment runoff are often reported as a function of percentage wetlands within the watershed (Driscoll et al 1995;Watras et al 1995;Shanley et al 2005). Many Adirondack lakes have a high percentage of MeHg (approx.…”