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Development and mapping of seleniferous soils in northwestern India

Dhillon, Karaj S., Dhillon, Surjit K.
Chemosphere 2014 v.99 pp. 56-63
calcium carbonate, carbon, electrical conductivity, hills, irrigation, pH, rice, sediments, selenium, silt loam soils, soil map, soil profiles, surveys, vegetation, villages, India
Periodic surveys were undertaken to identify and characterize Se-contaminated soils in northwestern India. Total Se content varied from 0.023 to 4.91mgkg−1 in 0–15cm surface soil and 0.64–515.0mgkg−1 in samples of vegetation. Selenium-contaminated land occupying an area of 865ha was classified into different categories based on total Se content of soils as moderately contaminated (0.5–2.0mg Sekg−1) and highly contaminated (>2.0mg Sekg−1). The normal soils contained <0.5mg Sekg−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 0.3–0.7dSm−1, calcium carbonate 0.1–4.1% and organic carbon 0.4–1.0%. Selenium was present throughout the soil profile up to 2m depth; 0–15cm 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 847μgkg−1, respectively. The sediments transported through seasonal rivulets linking the Shiwalik ranges to affected sites contained 0.57–2.89mg Sekg−1. The underground water containing 2.5–69.5μg SeL−1 used for irrigating transplanted rice grown in Se-contaminated area resulted in a net Se addition in soil up to 881gha−1y−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.