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Located in the Darwin Valley (80 degrees S), Lake Wilson is one of the southern-most of the stratified, ice-covered inland lakes of the arid McMurdo Dry Valley region. In January 1993 samples were collected for the determination of acid-soluble and dissolved trace metal (Cu, Pb, Zn, Co, Cd, and Ni) concentrations in the lake and its inflow. Parameters likely to influence trace metal speciation such as DO, pH, major ion concentrations, suspended sediment load, Fe-, Al-and Mn-oxide concentrations and phytoplankton activity, were also quantified.

The inflow to Lake Wilson transfers a significant load of suspended sediment into the upper/oxic layers of the lake, and this was reflected in the high concentrations of suspended sediment, Fe-oxide and Al-oxide in the upper water column. In the inflow, trace metals were predominantly bound to suspended particulates. In the lake, metals could be broadly classified into two groups on the basis of observed behaviour: those predominantly bound to particulates in the oxic lake water, showing high concentrations in the upper/oxic layer where suspended sediment levels were high (Pb and Co), and those predominantly or partially present in dissolved form in the oxic lake water (Cu, Zn, Ni and Cd). The concentrations of the latter increased with increasing salinity in the lower lake waters. Trace metal concentrations increased or remained relatively high in the anoxic zone below 95 m depth.

The principal process controlling trace metal speciation in the inflow and upper layers of Lake Wilson is considered to be metal adsorption onto, and desorption from, oxide surfaces in the suspended sediment, as has previously been proposed for Lake Vanda. However, the vertical distribution of trace metals in Lake Wilson differed from that of metals in Lake Vanda, due to differences in the density gradients (affecting suspended sediment distribution), pH gradients (affecting the degree of metal adsorption), biological activity and H2S concentrations (affecting metal solubility in and just above the anoxic zone). Upward diffusion of trace metals from the lower lake appeared to be an important factor influencing metal distribution in the water column of Lake Wilson.