9
Emerging Selenium
Contamination Issues
Introduction
Because of recent increases in human activities that promote the
introduction of selenium into aquatic habitats, new threats are
emerging on a broad scale in the United States and elsewhere. An
important factor in these threats is that food-chain bioaccumulation
and resultant dietary exposure cause the response curve for selenium poisoning in fish to be very steep. For example, a transition
from no effect to complete reproductive failure can occur within a
range of only a few f-lglL (parts per billion) waterborne selenium
(Fig. 9.1). Thus, activities that cause even slight increases can
quickly push selenium bioaccumulation over the toxic threshold.
In the United States, anthropogenic disturbances have greatly
increased the likelihood that aquatic ecosystems will experience
elevated selenium. From the 1960s through the 1980s, two disturbances stood apart as the major human-related causes of selenium
mobilization on a regional and national scale: (1) procurement,
processing, and combustion of fossil fuels (Lemly 1985); and (2)
irrigation of seleniferous soils for crop production in arid and semiarid regions (Lemly et al. 1993). Since the early 1990s, other issues
have emerged as potentially important factors in the mobilization
and bioaccumulation of hazardous concentrations of selenium. Primary among these are: (l) phosphate mining wastes, (2) use of
constructed wetlands to treat selenium-laden wastewater, (3) landfill
disposal of ash from coal-fired power plants, and (4) accumulation
of animal waste at livestock feedlots and intensive rearing facilities. This chapter examines these issues in the context of new, largely
uninvestigated selenium threats that may be sufficient to cause
widespread impacts to aquatic ecosystems.
145
Emerging Selenium
Contamination Issues
Introduction
Because of recent increases in human activities that promote the
introduction of selenium into aquatic habitats, new threats are
emerging on a broad scale in the United States and elsewhere. An
important factor in these threats is that food-chain bioaccumulation
and resultant dietary exposure cause the response curve for selenium poisoning in fish to be very steep. For example, a transition
from no effect to complete reproductive failure can occur within a
range of only a few f-lglL (parts per billion) waterborne selenium
(Fig. 9.1). Thus, activities that cause even slight increases can
quickly push selenium bioaccumulation over the toxic threshold.
In the United States, anthropogenic disturbances have greatly
increased the likelihood that aquatic ecosystems will experience
elevated selenium. From the 1960s through the 1980s, two disturbances stood apart as the major human-related causes of selenium
mobilization on a regional and national scale: (1) procurement,
processing, and combustion of fossil fuels (Lemly 1985); and (2)
irrigation of seleniferous soils for crop production in arid and semiarid regions (Lemly et al. 1993). Since the early 1990s, other issues
have emerged as potentially important factors in the mobilization
and bioaccumulation of hazardous concentrations of selenium. Primary among these are: (l) phosphate mining wastes, (2) use of
constructed wetlands to treat selenium-laden wastewater, (3) landfill
disposal of ash from coal-fired power plants, and (4) accumulation
of animal waste at livestock feedlots and intensive rearing facilities. This chapter examines these issues in the context of new, largely
uninvestigated selenium threats that may be sufficient to cause
widespread impacts to aquatic ecosystems.
145