Mercury empirical relationships in sediments from three Ontario lakes

Abstract

Total mercury (THg), methyl mercury (MeHg), total organic carbon (TOC), sediment bulk density (SBD), redox potential (Eh) and percent fines measurements were made on sediment cores collected along transects from littoral to profundal depths in Harp, Dickie, and Blue Chalk lake located on the Canadian Shield near Dorset, Ontario, Canada to determine whether empirical relationships exist among these sediment properties. MeHg was positively correlated with THg in all sediments with a MeHg:THg ratio (0.004+/-0.004) comparable to other uncontaminated profundal lakes. MeHg, MeHg:THg and TOC decreased with sediment depth within the core for all lakes, whereas THg only showed a decrease in Harp Lake. MeHg:THg ratio in surficial sediments was positively correlated with Eh and negatively correlated with TOC [MeHg:THg=-0.009 TOC (%)+0.001 Eh (mV)-1.902, p=0.026]; whereas THg was positively correlated with TOC [log THg (ppb)=0.026 TOC (%)+1.400, p<0.0001].