The Spatial Distribution and Fate of Trace Metals in Ombrotrophic Peat Bogs

Atmospheric deposition of heavy metals and other pollutants has substantially increased due to human activities over the past several hundred years. For some metals such as lead and mercury, these changes have been well studied because of their potentially harmful impact to human and ecosystem health. However, some aspects of metal transport and storage in the environment are still not well understood; for example, metal mobility in acidic wetlands and peat bogs is complex and not well constrained. Sediment cores from an ombrotrophic peat bog in the S-2 Watershed in Marcell Experimental Forest, Northern Minnesota were examined to determine potential drivers of the element mobilization or remobilization in a wetland/bog environment. Sediments and porewaters were analyzed for metal concentration, and core transects showed clear trends in the metal concentration from upland sites higher in the watershed to the peat bog. The trends were then compared with the hydrology of the watershed, as well as background studies of the elements to determine their potential fate. Evidence suggests some elements such as mercury are actively being transported through the watershed system in relation with the watershed’s hydrologic flow, whereas lead does not appear to be mobile from the uplands into the peatlands, but may be mobile in the peatlands in correspondence with the pH and anoxic condition of the watershed.