Groundwater Contamination by Mercury from the Aforetime Carroting Practice

In the southernmost Brazilian city of Rio Grande, the chemical treatment of animal fur named carroting was performed between the eighteenth and twentieth century. This type of industry has led to contamination of urban soil with mercury down to the groundwater level. The present study has revealed that the dissolved mercury concentrations in groundwater in the mercury contaminated areas was up to 13 times higher than that found in the reference site. The association between SO₄^2-, Ca²⁺ and dissolved mercury indicate that urban man-made grounds composed by soil, construction and demolition waste, urban rubbish and mud contaminated by "carroting mercury" serve as a source of this metal to groundwater. Despite the high level of contamination, mercury concentrations found in groundwater were below the permissible level established for potable water. Most of the dissolved mercury was chemically combined, probably with organic matter.