Ja. Mastrine et al., Mercury concentrations in surface waters from fluvial systems draining historical precious metals mining areas in southeastern USA, APPL GEOCH, 14(2), 1999, pp. 147-158
This study evaluates several southern Appalachian Piedmont mining districts
for Hg contamination in surface waters and determines potential relationsh
ips between Kg discharged from historical mining operations and site-specif
ic physical factors. Water samples were collected from 3 fluvial systems th
at drain areas where Hg was used to amalgamate Au from ore during the 19th
century. Each of the fluvial systems exhibit similar physical characteristi
cs such as climate, vegetation, and rock type. Total Hg (Hg-T) determinatio
ns were made using cold vapour atomic fluorescence spectroscopy techniques.
Concentrations of Hg-T in the southern Appalachian Piedmont range from 1-3
ng l(-1) in waters of the Arbacoochee, Alabama, and South Mountains, North
Carolina, Mining Districts to 13 ng l(-1) in waters of the Dahlonega Minin
g District in Georgia. The correlation between Hg, and total suspended soli
ds (TSS) at the southern Appalachian sites was good with a coefficient of d
etermination (r(2)) of 0.82. A clear trend between environmentally-availabl
e Fe (Fe-E) and Hg-T (r(2)=0.86) was also evident. The correlation between
HET and Fe-E most likely reflects similarities in the mechanisms that contr
ol the aqueous concentrations of both metals (i.e., the particle-reactive n
ature of the two elements), allowing for the sorption of Hg onto Fe-oxyhydr
oxides. Hence, increased loads of TSS from erosional events are probably re
sponsible for higher stream water Hg-T concentrations. Vegetation at these
sites, which is heavy due to the warm, humid climate of the Southeastern U.
S.A., may help reduce the total amount of Hg released from contaminated min
ing sites to the rivers by controlling erosion, hence, decreasing the input
of contaminated particles into streams and rivers.
These southern Appalachian mining sites used Hg amalgamation techniques sim
ilar to those used in other precious metals mining districts, such as the h
ighly contaminated Comstock Au-Ag district in Nevada, yet Hg-T concentratio
ns are orders of magnitude lower; This difference in concentration between
the southern Appalachian districts and the Comstock district may correlate
to the relative amounts of HE that were used in each. However, other variab
les were evaluated to determine if physio-chemical differences such as clim
ate could influence Hg-T concentrations in surface waters of the two areas.
(C) 1999 Elsevier Science Ltd. All rights reserved.