Total mercury in the water and sediments of St. Lawrence River wetlands compared with inland wetlands of Temagami North Bay and Muskoka-Haliburton

The concentration of total Hg was compared among 45 wetlands in three regio ns of Ontario. Twenty-two of these wetlands were located in the Muskoka-Hal iburton Highlands and Temagami - North Bay regions and included bogs, fens, and marshes. Twenty-three were riverine marshes along the St. Lawrence Riv er, near Cornwall, a Great Lakes area of concern, where Hg has been release d through industrial activity. Overall, significant but weak negative relat ionships were found between pH and alkalinity of the surface waters and tot al water Hg concentrations (r(2) = 0.28-0.30, p < 0.001). A significant pos itive relationship was found between dissolved organic C and total water Hg (r(2) = 0.30). On average, St. Lawrence wetlands had lower total water Hg when compared with the inland wetlands, While a strong positive relationshi p was found between sediment organic matter and total sediment Hg concentra tions (p < 0.001), the relationship was significantly different between the St. Lawrence and inland wetlands. In general, the St. Lawrence wetlands, d espite the proximity to point sources of Hg, actually had lower sediment Hg , likely because of the lower organic matter. However, the St. Lawrence wet lands had twice the amount of Hg per unit of organic matter; the consequenc es of this difference for methyl mercury production and bioaccumulation nee d to be addressed.