Bedrock, mercury

Driscoll et al. (1994) have studied the mercury species relationships among water, sediments, and fish (yellow perch) in a series of Adirondack lakes in New York state, USA. In most lakes, approximately 10% of the total mercury loading was in the form of C2HsHg+. Mercury concentrations increased as pH fell, but the best correlation was found between [dissolved Al] and [dissolved Hg] suggesting that the same factors are responsible for mobilizing both these metals. Methylmercury concentrations correlated strongly with the dissolved organic carbon content in the water. Fish muscle tissue was analyzed for mercury and showed an increase with age. However, the study was unable to resolve the question of whether the principal source of mercury to these lakes was atmospheric deposition or dissolution from bedrock due to acid rains. 

Fig. 12-26. Mercury and Zn contents of soils, fluvioglacial cover and bedrock at the Bastyan dam-site road cutting (from Carr ct al., 1986).

McLEAN I give can you one example from my Table 2. The first two lakes (A1 and A2) are in a mineralized area, where the mercury concentrations in the bedrock are quite high (for Lake Waconichi, 0.5-1.0 ppm). The mercury concentration in the fish in these two lakes are much less than the concentrations in the next two lakes A3 and A4 which are not mineralized and have low sediment mercury concentration (0.05-0.1 ppm). The minerals are sulfide-containing, so presumably, this prevents the release of mercury to the water. 

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