Accelerated Rates of Selenium Volatilization From California Soils

Abstract

Volatilization of alkylselenides from soils spiked with labeled Se was monitored in a continuous flow system by using activated carbon traps and counting the recovered 75 Se. Surface soils from a known Se‐problem area in California were used throughout this study. Inoculation with fungal isolates from these soils, including Acremonium falciforme, Penicillium citrinum , and Ulocladium tuberculatum enhanced Se evolution in nonsterile and autoclaved soils. The fraction of added Se volatilized per unit time was dependent upon Se level, soil series, Se species, and C amendment. Without C amendment, volatilization rates were up to an order of magnitude higher with Se(IV) as the Se source, when compared to Se(VI). Carbon addition in the form of pectin accelerated Se evolution 2‐ to 130‐fold, which was more pronounced with Se(VI) and with the less active soils. Hence with C amendment, Se(VI) was volatilized almost as rapidly as Se(IV) by all soils. With three pectin amendments over a period of 118 d, total Se volatilization ranged from 11.3 to 51.4% of the added Se. A minimum Se threshold for alkylselenide production was not found, applying Se additions as low as 10 µg kg −1 soil.