Soil Total Mercury, Carbon and Nitrogen Within Northern Minnesota Forested Wetland Basins in Relation to Landscape Position, Profile Depth, and Landscape Characteristics.

Mercury in the environment is a human health hazard as it can become biologically available and enter the food chain. To better manage ecosystems for the control of mercury, its fate and transport must be understood. The objective of this research was to characterize the distribution of total soil mercury (THg), carbon (C) and nitrogen (N) at five landscape positions (wetland center, wetland edge, toe slope, back slope and shoulder), at four depths (0-2, 2-5, 5-10 and 10-15 cm), within ten wetland basins in a northern hardwood forest located in Itasca County, Minnesota, USA. In addition, landscape and vegetative features were recorded (basin perimeter, wetland perimeter, slope length, slope grade, slope aspect, canopy closure, basal area of trees, predominant species, and ground cover). Results indicate that the three upland landscape positions have significantly lower (p<0.05) average THg concentrations than pond centers, ranging from 27.7 to 30.3 ng cm^-3 versus 51.7 ng cm^-3, respectively, indicating that Hg is being transported downslope. At upland landscape positions, THg concentrations in the upper three soil depths ranged from 30.2 to 35.3 ng cm^-3 and were significantly greater than the 10-15 cm depths, which ranged from 19.0 ng cm^-3 to 24.5 ng cm^-3, indicating that Hg was likely from atmospheric deposition and not geogenic. Understanding how THg, C and N behave and factors that may predict their behavior could be useful in managing similar ecosystems for the retention of nutrients and sequestration of C and Hg.