Plants, terrestrial selenium

All manner of pollutants are considered under the discipline of terrestrial ecotoxicology including pesticides, persistent organic pollutants, other organic substances, and metals and metalloids (e.g., selenium and arsenic). Naturally occurring toxins such as those produced by poisonous plants, snakes, or invertebrates generally are not included unless people intentionally apply them for pest control. For example, the pyrethroid pesticides are derived from the naturally occurring pyrethrin toxin that is found in chrysanthemum. 

Terrestrial plants take up soluble selenate and selenite and biosynthesize organic selenium compounds, predominantly selenomethionine and, to a lesser extent, selenocysteine. Selenates tend to be taken up by plants from soils more readily than selenites, in part because selenites tend to adsorb more strongly to soils (Dimes et al. 1988 Zhang et al. 1988). These compounds can be released to the soils once the plants die and decay. Water-soluble organic selenium compounds are also probably readily taken up by plants (Shamberger 1981 Shrift 1964). 

Arthur MA, Rubin G, Woodbury PB, et al. 1992. Uptake and accumulation of selenium by terrestrial plants growing on a coal fly ash landfill Part 2. Forage and root crops. Environ Toxicol Chem 11(9) 1289-1299. 

Annually, 79 000 tons of selenium are mobilized into the biosphere, as estimated by Nriagu and Pacyna (1988). This amount corresponds to the median value of the terrestrial plus aquatic inputs, minus atmospheric emissions (Figure 7.1). The major sources of selenium pollution in aquatic ecosystems, including the oceans, are domestic wastewater effluents, coal-buming power plants, and... 

Among terrestrial plants, selenium accumulations in species of Aster,Astragalus, and several other genera are sometimes spectacularly high. Astragalus is the most widely distributed. About 24 of its more than 200 species are... 

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