Groundwater Contamination by Mercury from the Aforetime Carroting Practice

Area of Science:

• Environmental Science
• Geochemistry
• Urban Hydrology

Background:

• The carroting process, used for animal fur treatment from the 18th-20th centuries in Rio Grande, Brazil, has resulted in significant mercury contamination.
• This historical industrial activity has impacted urban soil and extended contamination to groundwater levels.

Purpose of the Study:

• To assess mercury contamination in groundwater resulting from historical carroting activities.
• To investigate the relationship between soil composition and mercury levels in groundwater.
• To determine if mercury concentrations in groundwater pose a risk to potable water standards.

Main Methods:

• Analysis of dissolved mercury concentrations in groundwater from contaminated and reference sites.
• Identification of associated ions (SO4^2-, Ca^2+) and their correlation with dissolved mercury.
• Evaluation of urban man-made grounds as a mercury source.

Main Results:

• Groundwater mercury concentrations in contaminated areas were up to 13 times higher than in the reference site.
• A strong association was found between sulfate (SO4^2-), calcium (Ca^2+), and dissolved mercury.
• Mercury concentrations in groundwater, despite being elevated, were below the permissible limit for potable water.

Conclusions:

• Urban man-made grounds contaminated with "carroting mercury" act as a source for groundwater contamination.
• The majority of dissolved mercury in the groundwater is chemically bound, likely to organic matter.
• While contamination is significant, current groundwater mercury levels do not exceed safety standards for drinking water.