Mercury contamination of active channel sediment and floodplain deposits from historic gold mining at Gold Hill, North Carolina, USA

A reconnaissance investigation of mercury contamination associated with historic gold mining in North Carolina, USA, revealed high concentrations of mercury in channel and floodplain sediments downstream from the Gold Hill mining district. The most intense period of mining activities in this region occurred in the 1840s and 1850s when mercury amalgamation was used to recover fine gold particles from milled ore. This paper evaluates mercury concentrations measured in active channel sediments and two cores recovered from historic floodplain deposits of the lower portion of Dutch Buffalo Creek. Mercury concentrations in these cores range from 0.01 to 2.2 mg/kg, with maximum concentrations more than 35 times background levels. A later peak in copper concentrations is associated with the operation of a large copper mine between 1899 and 1906. Following the most intense periods of mining, both mercury and copper concentrations decrease upcore to constant levels of about twice pre-mining background concentrations. Results suggest that vertical trends in mercury and other trace metals provide a useful tool for interpreting rates of historic floodplain sedimentation in the Piedmont of North Carolina.