CHARACTERIZATION AND CORRELATION OF SOIL AND PLANT SELENIUM IN SOME RANGE AND COAL-MINE ENVIRONMENTS OF WYOMING

Selenium (Se) has been recognized as an element of environmental conce rn because of its natural occurrence and potential toxicity to plants, animals, and humans. Range and coal mine (reclaimed and abandoned) so ils were studied using various soil extracts, including saturated past e, hot water, ammonium bicarbonate-DTPA (AB-DTPA), and phosphate in or der to compare the Se extraction efficiency of these reagents and to c haracterize the soil-plant Se correlations in these environments. Soil extraction data indicated the order of Se extractability was phosphat e > AB-DTPA > hot water > saturated paste. The saturated paste-extract able Se was found to be typically very low. Statistically significant correlations between phosphate, AB-DTPA-, and hot water-extractable Se were observed irrespective of the type of environment. Selenium extra cted by these reagents indicated certain relationships, such as phosph ate approximate to 2 AB-DTPA, phosphate approximate to 5 hot water, an d AB-DTPA approximate to 3 hot water. Selenium content of shrub vegeta tion was approximately half of that of grass and forb. Soil-plant Se c orrelations were found to be dependent on land type as well as vegetat ion type; the regressional values for soil suitability limit (SSL) of Se corresponding to 5 mg/kg plant Se varied accordingly. For a particu lar type of vegetation, the SSL values followed the same order as the extraction efficiency of the different reagents. The AB-DTPA-extractab le Se was found to be the best predictor of soil-plant Se correlations under field conditions, though phosphate-, hot water-, and saturated paste-extractable soil Se were also related to the Se concentrations i n different types of vegetation. Selenate was found to be the potentia l aqueous specie for plant uptake. A comparison of different soil envi ronments containing various vegetation types also suggested that, for a plant containing 5 mg/kg Se, the soil Se status would be highest in abandoned mine lands, followed by reclaimed mine and undisturbed range environments, respectively.