Selenium in Kesterson Reservoir Ephemeral Pools Formed by Groundwater Rise: II. Laboratory Experiments

Abstract

AbstractThe formation of seleniferous ephemeral pools that result from shallow water table rise through seleniferous soils was studied in laboratory columns of soils from Kesterson Reservoir, Merced County, California. Variables included in the column experiments included the depth interval of the soils, the rate of shallow water table rise and temperature. The columns were packed with either surface (0–0.15 m) soils (with and without the original salt crust), or subsurface soils (0.15–0.30 m) sampled from the southwest corner of Pond 1, Kesterson Reservoir. Controlled inputs of nonseleniferous, saline water through the bottoms of the columns provided water table rise rates of 3, 10 and 30 mm d−1. The soil columns were maintained at either room temperature (≈25°C) or 5°C. The amount of Se transported from the soils into the overlying ponding waters was proportional to the water‐extractable soil Se content, and was positively correlated with the rate of water table rise. The 5°C experiments resulted in greater Se transfers into the ponding waters in the columns subjected to 10 and 30 mm d−1 rates of water table rise (relative to comparable room temperature columns), while the reverse effect was observed with 3 mm d−1 columns.