Potential impact of acid precipitation on arsenic and selenium.

Abstract

The potential impact of acidic precipitation on the environmental mobility of the metalloids arsenic (As) and selenium (Se) has not been given much attention and is poorly understood. As with other elements, the interest here is the potential effect of environmental acidification on environmental behavior in ways that are relevant to human exposure to these metalloids. Available information on acid precipitation and the environmental behavior of these metalloids do, however, permit some preliminary conclusions to be drawn.Both As and Se appear to be mobilized from household plumbing into tap water by the corrosive action of soft, mildly acidic water, while surface water catchment systems in areas impacted by acidic deposition may contain elevated soluble As levels.Acidification of aquatic ecosystems that are drinking water sources may pose the prospect of enhanced release of As from sediment to water as well as reduction in water levels of Se. Acidification of ground waters, where As appears to be especially mobile, is of particular concern in this regard.The potential impact of acidic deposition on As and Se in soils cannot readily be assessed with respect to human exposure, but it would appear that the behavior of these metalloids in poorly buffered, poorly immobilizing soils, e.g., sandy soils of low metal hydrous oxide content, would be most affected. The effect is opposite for the two elements; lowered pH would appear to enhance As mobility and to reduce Se availability.Altered acidity of both soil and aquatic systems poses a risk for altered biotransformation processes involving both As and Se, thereby affecting the relative amounts of different chemical forms varying in their toxicity to humans as well as influencing biogeochemical cycling.

Effect of Trace Elements on Population Dynamics: Selenium Deficiency in Free‐Ranging Black‐Tailed Deer

“…While increased exposure to a number of substances results in an increased demand for Se (e.g., Hg [Burk et al 1974]; Cd [Van Vleet and Boon 1981]; sulfur [Kahn et al 1987]), there are several factors that may contribute to an apparent decline of soil Se availability to plants and animals. Plant selenium concentration or availability can be reduced by acidification of soils (Geering et al 1968) due to acid precipitation (Fisher 1982, Mushak 1985, Frost 1987 or biomass exportation (Ridley et al 1990). Plant fertilizers (S, N, and P) also reduce Se availability to animals (Gissel-Nielsen 1977, Millar 1983, Gupta and Watkinson 1985, a possibility also in remote areas due to aerial deposition (Ellenberg 1986).…”

From Selenium to Selenoproteins: Synthesis, Identity, and Their Role in Human Health

“…On a global scale, selenium availability in the soil varies between areas. Low selenium content is observed in volcanic regions and in regions with "acid soil," such as the southeastern parts of the United States (239,298). The presence of other elements, such as sulphur, aluminium, and iron, also negatively affects the uptake of selenium by plants (165,305).…”

Gastro-Intestinal Absorption of Lead in Children and Adults: Overview of Biological and Biophysico-Chemical Aspects

“…Comparatively less has been forthcoming with regard to metals and metalloids (Calabrese, 1984). Some relevant comparisons have appeared for arsenic and selenium and certain forms of mercury (Mushak, 1985(Mushak, , 1983 but rather less for inorganic, divalent lead, the most environmentally significant chemical form (see, however, Scharding and Oehme, 1973 and relevant papers in these Proceedings).…”

“…The environmental epidemiology of toxic metals and metalloids, by contrast, has often given less attention to circumstances of their form-specific bioavailability and/or bioactivity (e.g. Mushak, 1987aMushak, , 1985Mushak, , 1983. This is due in part to the absence of information on form-specific bioactivity and in part to an assumption that the core element should confer uniform toxicity.…”