Factors Affecting Soil Total Mercury, Carbon and Nitrogen Distributions in Seasonal Pond Basins within a Northern Hardwood Forest in Minnesota, USA

Abstract

Forests are sites for mercury deposition, where accumulation in aquatic environments can occur. Soil total mercury (THg), C and N to 15 cm were studied in ten seasonal pond basins in a northern hardwood forest (Minnesota, USA). Pools and concentrations of THg were lower in uplands than in ponds, indicating downslope transport or differential deposition. In uplands, THg concentrations were the same in 0-2 and 2-5 cm depths and then decreased, whereas density peaked in 2-5 cm, highlighting the importance of bulk density on mass. Carbon and N trends were similar to THg. Apart from pond centers, strong positive relationships between THg and C were observed. Upland slope length, graminoid cover, basin area and tree height accounted for over half of THg variance at pond edge. Understanding the distribution, trends and contributing factors of soil THg can further efforts toward immobilization and sequestration, thus minimizing the potential for bioaccumulation.