Development and mapping of seleniferous soils in northwestern India

• Periodic surveys to identify and characterize Se sources and contaminated soils.
• Se in soil, plant varied from 0.02-4.9, 0.6-515 mg/kg; present in profile 2 m depth.
• Developed map showing different categories of seleniferous soils in northwest India.
• Shiwalik rocks and underground water are the main sources of Se contamination.
• Se-rich sediments deposited by rain water lead to development of seleniferous soils.

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−1). 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 μg 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 μg 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.