150
9. Emerging Selenium Contamination Issues
to dispose of fly ash from 5 different power plants. Concerns were
voiced by local wildlife conservation groups regarding the possibility
that selenium-laden leachate from the landfill would threaten populations of native brook trout (Salvelinusfontinalis), a highly valued sport
fish in the region. This prompted an investigation by the Pennsylvania
Department of Environmental Resources (PDER) into the leaching behavior of selenium in fly-ash. The initial investigation provided evidence that selenium leaching was a legitimate concern, leading the
PDER to revoke the disposal permit for 2 of the 5 facilities identified in
the original application (Pennsylvania Bulletin 1992) and to call for
strict controls on the physical and chemical characteristics of ash materials allowed in the landfill (Commonwealth of Pennsylvania 1991).
Additional investigations revealed more potential problems with selenium in leachate from the site and resulted in the landfill being
repermitted to handle only construction and demolition waste-no fly
ash was allowed. The events in this case represent major adjustments
to Pennsylvania laws brought about by environmental concerns over
selenium in fly-ash landfills. Moreover, the actions taken by the PDER
set an important precedent by establishing very rigid requirements for
landfills that are proposed in the future.
Coal-fired power production in the new millennium will increase
the need for new fly-ash landfills which, in turn, will steadily increase
the threat of selenium-laden leachate contaminating aquatic habitats
and impacting fish populations. When the large number of existing
waste dumps is factored in, it becomes clear that the risk of serious
ecological consequences is on the rise. Every new fly-ash landfill is a
potential selenium source to down-gradient aquatic habitats, expanding the threat on a regional and national scale.
Feedlot Wastes
Selenium is widely used as a nutritional supplement to livestock diets,
and it is common for the liquid manure associated with swine or cattle
feedlots to contain 50 to 150 Ilg SelL (Oldfield 1998). A primary reason
for these relatively high levels is that livestock feeds are typically supplemented with selenium to enhance growth; thus, higher intake means
higher concentrations in wastes. Because excreted selenium has been
physiologically processed by the animal, the chemical forms present
in this matrix likely include various organic metabolites or other organic compounds. Importantly, organic selenium has a much greater
bioaccumulation potential in aquatic ecosystems than the inorganic
selenium that is associated with other pollution sources (eg, coal-fired
power plants, subsurface agricultural irrigation drainage). For example,
waterborne inorganic selenate and selenite typically bioaccumulate
100 to 4000 times in aquatic food chains, but organic selenoamino
9. Emerging Selenium Contamination Issues
to dispose of fly ash from 5 different power plants. Concerns were
voiced by local wildlife conservation groups regarding the possibility
that selenium-laden leachate from the landfill would threaten populations of native brook trout (Salvelinusfontinalis), a highly valued sport
fish in the region. This prompted an investigation by the Pennsylvania
Department of Environmental Resources (PDER) into the leaching behavior of selenium in fly-ash. The initial investigation provided evidence that selenium leaching was a legitimate concern, leading the
PDER to revoke the disposal permit for 2 of the 5 facilities identified in
the original application (Pennsylvania Bulletin 1992) and to call for
strict controls on the physical and chemical characteristics of ash materials allowed in the landfill (Commonwealth of Pennsylvania 1991).
Additional investigations revealed more potential problems with selenium in leachate from the site and resulted in the landfill being
repermitted to handle only construction and demolition waste-no fly
ash was allowed. The events in this case represent major adjustments
to Pennsylvania laws brought about by environmental concerns over
selenium in fly-ash landfills. Moreover, the actions taken by the PDER
set an important precedent by establishing very rigid requirements for
landfills that are proposed in the future.
Coal-fired power production in the new millennium will increase
the need for new fly-ash landfills which, in turn, will steadily increase
the threat of selenium-laden leachate contaminating aquatic habitats
and impacting fish populations. When the large number of existing
waste dumps is factored in, it becomes clear that the risk of serious
ecological consequences is on the rise. Every new fly-ash landfill is a
potential selenium source to down-gradient aquatic habitats, expanding the threat on a regional and national scale.
Feedlot Wastes
Selenium is widely used as a nutritional supplement to livestock diets,
and it is common for the liquid manure associated with swine or cattle
feedlots to contain 50 to 150 Ilg SelL (Oldfield 1998). A primary reason
for these relatively high levels is that livestock feeds are typically supplemented with selenium to enhance growth; thus, higher intake means
higher concentrations in wastes. Because excreted selenium has been
physiologically processed by the animal, the chemical forms present
in this matrix likely include various organic metabolites or other organic compounds. Importantly, organic selenium has a much greater
bioaccumulation potential in aquatic ecosystems than the inorganic
selenium that is associated with other pollution sources (eg, coal-fired
power plants, subsurface agricultural irrigation drainage). For example,
waterborne inorganic selenate and selenite typically bioaccumulate
100 to 4000 times in aquatic food chains, but organic selenoamino