Estimation and Mapping of Wet and Dry Mercury Deposition Across Northeastern North America

Abstract

Abstract. Whereas many ecosystem characteristics and processes influence mercury accumulation in higher trophic-level organisms, the mercury flux from the atmosphere to a lake and its watershed is a likely factor in potential risk to biota. Atmospheric deposition clearly affects mercury accumulation in soils and lake sediments. Thus, knowledge of spatial patterns in atmospheric deposition may provide information for assessing the relative risk for ecosystems to exhibit excessive biotic mercury contamination. Atmospheric mercury concentrations in aerosol, vapor, and liquid phases from four observation networks were used to estimate regional surface concentration fields. Statistical models were developed to relate sparsely measured mercury vapor and aerosol concentrations to the more commonly measured mercury concentration in precipitation. High spatial resolution deposition velocities for different phases (precipitation, cloud droplets, aerosols, and reactive gaseous mercury (RGM)) were computed using inferential models. An empirical model was developed to estimate gaseous elemental mercury (GEM) deposition. Spatial patterns of estimated total mercury deposition were complex. Generally, deposition was higher in the southwest and lower in the northeast. Elevation, land cover, and proximity to urban areas modified the general pattern. The estimated net GEM and RGM fluxes were each greater than or equal to wet deposition in many areas. Mercury assimilation by plant foliage may provide a substantial input of methyl-mercury (MeHg) to ecosystems.

Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach

“…At Andrews, weekly bulk deposition was sampled during the non-snow period, and an April snowpack sample represented Hg deposition for the NovembereApril snow accumulation period, recognizing that some revolatilization of Hg may have occurred (Mast et al, 2005). At Sleepers, both wet and dry Hg deposition were estimated from the regional model of Miller et al (2005), which utilizes regional wet Hg deposition data and models dry deposition considering Hg sources, elevation, and land cover type. Hg dry deposition at the other three sites was estimated assuming that dry deposition is two times wet deposition on the forested parts of the watershed .…”

“…Published values of MeHg fluxes are uncommon, but the Sleepers and Allequash MeHg fluxes fall within the range of those reported. Lee et al (1998) (Miller et al, 2005); Allequash from MDN station WI36; Icacos from lower elevation site using MDN protocols; wet deposition of 26.4 mg m À2 with 2900 mm precipitation scaled to 4362 mm precipitation at watershed; Andrews from snowpack (winter) or bulk collector (summer). b Dry deposition Hg input: Sleepers, annual average from regional model (Miller et al, 2005); other sites assumed that forested areas had dry deposition two times wet deposition.…”

“…Hg research in headwater upland landscapes is important because: (1) Hg deposition is enhanced at higher elevations and by forest canopy Miller et al, 2005); (2) headwaters harbor a large pool of Hg with uncertain fate; and (3) the bioavailability of this Hg is unclear and needs to be better assessed.…”

“…5). Wet THg deposition was derived from the model of Miller et al (2005), based on regional measurements. This retention percentage is considerably lower than is typical, and may reflect the focus on event sampling (Fig.…”

Mercury in alpine fish from four rivers in the Tibetan Plateau

“…Mining, smelting, coal combustion and industrial usage of Hg in chlor-alkali production, batteries, fluorescent lamps, medical devices and so on comprise anthropogenic sources (Pirrone et al, 2010;Streets et al, 2011). Due to the long lifetime of Hg in atmosphere and the ability of long range transport, Hg emitted from both natural sources and anthropogenic sources can be deposited into remote lakes and rivers, resulting in serious pollution in aquatic system (Fitzgerald et al, 1998;Miller et al, 2005;Poissant et al, 2008).…”