revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 396
5.2.3 Soil
5. POTENTIAL FOR HUMAN EXPOSURE
Atmospheric deposition of mercury from both natural and anthropogenic sources has been identified as an
indirect source of mercury to soil and sediments (Sato and Sada 1992; WHO 1990, 1991). Mercury is
released to cultivated soils through the direct application of inorganic and organic fertilizers (e.g., sewage
sludge and compost), lime, and fungicides containing mercury (Andersson 1979). Recent interest in
community recycling of sewage sludge and yard compost may result in increased releases of mercury from
these wastes. Sewage sludge contained approximately 20 times more mercury than yard compost
(2.90 ppm versus 0.15 ppm) (Lisk et al. 1992a); municipal solid waste contained the highest concentration
(3.95 ppm) (Lisk et al. 1992b). Recently, Carpi et al. (1998) studied the contamination of sludge-amended
soil with inorganic and methylmercury and the emission of this mercury contamination into the
atmosphere. These authors reported the routine application of municipal sewage sludge to crop land
significantly increased the concentration of both total mercury and methylmercury in surface soil from 80
to 6,1000 µg/kg (ppb) and 0.3–8.3 µg/kg (ppb), respectively. Both the inorganic and methylmercury were
transported from the sludge/soil matrix to the environment by emission to the atmosphere.
Additional anthropogenic releases of mercury to soil are expected as a result of the disposal of industrial
and domestic solid waste products (e.g., thermometers, electrical switches, and batteries) to landfills (see
Table 5-5). Another source of mercury releases to soil is the disposal of municipal incinerator ash in
landfills (Mumma et al. 1990). In 1987, nationwide concentrations of mercury present in the ash from
municipal waste incineration ranged from 0.03 to 25 ppm (Mumma et al. 1990). Such releases may exhibit
a seasonal variability. For example, fly ash collected prior to Christmas contained significantly less
mercury (6.5 ppm) than ash collected after Christmas (45–58 ppm), possibly as a result of the increased
use and disposal of batteries containing mercury in toys and other equipment during this season (Mumma
et al. 1991). Emission sources include stack emissions, ashes collected at the stack, ashes from
electrostatic precipitators, and in slags (Morselli et al. 1992). An analysis of mercury concentrations in
soil, refuse combustibles, and bottom and fly ash from incinerators showed increasing concentrations of 0,
2, 4, and 100 mg/kg (ppm), respectively (Goldin et al. 1992).
According to the Toxics Release Inventory, in 1996, the estimated releases of 537 pounds of mercury to
land from 31 large processing facilities accounted for about 0.63% of the total 1996 environmental releases
for this element (TRI96 1998). In addition, an estimated 9 pounds of mercury (