MEASUREMENT OF INSITU RATES OF SELENATE REMOVAL BY DISSIMILATORY BACTERIAL REDUCTION IN SEDIMENTS

A radioisotope method for measurement of bacterial respiratory reduction of selenate to elemental selenium in aquatic sediments was devised. Sediments were labeled with [75Se]selenate, incubated, and washed, and 75Se0(s) was determined as counts remaining in the sediment. Core profiles of selenate reduction, sulfate reduction, and denitrification were made simultaneously in the sediments of an agricultural wastewater evaporation pond. Most of the in situ selenate reduction (85%) and all the denitrification activities were confined to the upper 4-8 cm of the profile, whereas sulfate reduction was greatest below 8 cm (89% of total). The integrated areal rate of selenate reduction was 301 μmol m−2 day−1, which results in a turnover of water column selenate in 82.4 days. © 1990, American Chemical Society. All rights reserved.