title: Mercury distribution across 14 U.S. forests. Part II: Patterns of methyl mercury concentrations and areal mass of total and methyl mercury.
abstract: This study characterized distribution patterns of monomethyl mercury (MeHg) and areal mass of total mercury (THg) and MeHg across U.S. upland forests. MeHg concentrations increased from surface litter (average: 0.14 μg kg(-1)) to intermediate (0.47 μg kg(-1)) and deeper, decomposed litter (1.43 μg kg(-1)). MeHg concentrations were lower in soils (0.10 μg kg(-1) at 0-20 cm depth; 0.06 μg kg(-1) at >20 cm depth). Ratios of MeHg to THg were higher in litter compared to soils. In soils, MeHg concentrations positively correlated with THg across all sites, and MeHg concentrations also increased with C content and latitude. THg areal mass ranged from 41.6 g ha(-1) to 268.8 g ha(-1). Largest THg mass at all sites was sequestered in soils (average of 91%), followed by litter (8%) and aboveground biomass (<1%). MeHg mass (litter plus soils only) ranged from 75 to 443 mg ha(-1), of which 88% was found in soils. Both THg and MeHg mass correlated with latitude, with average mass increases of 10.6 g ha(-1) (THg) and 20 μg ha(-1) (MeHg) per degree latitude, indicating that highest THg and MeHg accumulation in upland forests are expected in northern sites.
authors.affiliation: Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512, USA. Daniel.Obrist@dri.edu
authors.forename: Daniel
authors.initials: D
authors.lastname: Obrist
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D018533:Biomass; D004784:Environmental Monitoring; D016014:Linear Models; D008628:Mercury / Q000032:analysis*; D008767:Methylmercury Compounds / Q000032:analysis*; D012987:Soil / Q000737:chemistry; D014197:Trees / Q000378:metabolism*; D014481:United States; D014866:Waste Products / Q000032:analysis
chemical_list: D000393:Air Pollutants; D008767:Methylmercury Compounds; D012987:Soil; D014866:Waste Products; D008628:Mercury