Total and methyl mercury in wetland soils and sediments of Louisiana's Pontchartrain Basin (USA)

Accumulation of methylmercury (MeHg) in aquatic biota is a primary toxicological concern associated with Hg contamination in the environment. This study reports total mercury (THg) and MeHg measurements in 11 swamp and 24 marsh soils/sediments in wetlands surrounding Lake Pontchartrain and Lake Maurepas located in Louisiana's Pontchartrain Basin. The salinity level ranged from fresh, brackish to salt water. Average THg content in the swamp soils/sediments (112.3 μ g kg−1, n = 10) was significantly higher (P = 0.04) than in the marsh soils/sediments (56.5 μ g kg−1, n = 24). The THg content in the marsh soils/sediments tended to decrease with salinity increase, probably due to geographical locations of the sampling sites with less Hg input in more saline regions. Average MeHg content in the soils/sediments was 1.3 μ g kg−1 (n = 34), higher than reported values in the bottom sediments of Lake Maurepas (0.8 μ g kg−1, n = 27) and Lake Pontchartrain (0.6 μ g kg−1, n = 147). Average MeHg/THg ratio in the marsh s...