Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 1997
Publication Date: N/A
Interpretive Summary: The occurrence of toxic elements in irrigation drainage waters necessitates that these waters be properly managed to limit their impacts on the environment. Disposal of irrigation water from central California farms from 1978 to 1983 resulted in the deposition of 9 tons of the element selenium into a series of evaporation ponds. Research to determine the distribution of the different oxidation states in the evaporation ponds has been limited due to the failure to understand the role of sample preparation and sample storage on the changes in Se oxidation states of environment samples.This manuscript details the Se oxidation state changes that occur in sediment samples with improper storage and the oxidation state changes in seleniferous plant and soil samples that includes air-drying as sample preparation.
Technical Abstract: Significant changes in the distribution of selenium (Se) oxidation states of fresh soil were noted with oven-drying (90oC) or with outdoor storage (>5 years) in compromised plastic containers compared with small changes in Se oxidation state distribution in air-dried samples. Compromised outdoor storage resulted in a 25% increase in the selenate (Se+VI) concentrations with a concomitant 18.4% and 5.7% decrease in refractory Se and selenite (Se+IV) concentrations, respectively. Substantial increases in phosphate-soluble Se from 18.5% for fresh seleniferous alfalfa to 40% phosphate-soluble Se were noted with air-dried alfalfa. The results suggest that air-drying will not substantially alter the distribution of soil Se oxidation states, but air-drying will result in a significant increase in concentration of phosphate-soluble Se in seleniferous alfalfa residue.