Development and mapping of seleniferous soils in northwestern India

Periodic surveys were undertaken to identify and characterize Se-contaminated soils in northwestern India. Total Se content varied from 0.023 to 4.91 mg kg(-1) in 0-15 cm surface soil and 0.64-515.0 mg kg(-1) in samples of vegetation. Selenium-contaminated land occupying an area of 865 ha was classified into different categories based on total Se content of soils as moderately contaminated (0.5-2.0 mg Se kg(-1)) and highly contaminated (>2.0 mg Se kg). The normal soils contained <0.5 mg Se kg(-1). The soil map was prepared using village level cadastral maps. Se-contaminated soils were silty loam to silty clay loam in texture and tested pH 7.9-8.8, electrical conductivity 0.3-0.7 dS m(-1), calcium carbonate 0.1-4.1% and organic carbon 0.4-1.0%. Selenium was present throughout the soil profile up to 2 m depth; 0-15 cm surface soil layer contained 1.5 to 6.0 times more Se than in subsurface layers. Selenium content in rock samples collected from lower and upper Shiwalik sub-Himalayan ranges varied from 1864 to 2754 and 11 to 847 mu g kg(-1), respectively. The sediments transported through seasonal rivulets linking the Shiwalik ranges to affected sites contained 0.57-2.89 mg Se kg(-1). The underground water containing 2.5-69.5 mu g Se L-1 used for irrigating transplanted rice grown in Se-contaminated area resulted in a net Se addition in soil up to 881 g ha(-1) y(-1); possibly further aggravating the Se-toxicity problem. Presence of substantial amount of Se in rock samples and sediments of seasonal rivulets suggests that Se-rich materials are being transported from Shiwalik hills and deposited in regions where seasonal rivulets end up. (C) 2013 Elsevier Ltd. All rights reserved.