Toxic aqueous discharge of iron and sulphur from spoiled coal mined lands and its control by phytostabilization process

Abstract

Toxic aqueous discharge of iron and sulphur due to acid mine drainage causes soil and water pollution. Many countries with unoperating as well as functional mining industries face this problem. In north-eastern India, coal mining has severely degraded much of the agricultural land by impairing soil, plant diversity and water quality. A study was conducted in coal mined out area of Jaintia hills, Meghalaya (northeastern India) to eliminate toxic aqueous discharge (iron and sulphur) and restore the soil fertility of affected land for sustainable crop production. The treatment of acid mine drainage through phytostabilization and soil amendment with agricultural lime and organic manures reduced sulphate from 22 to 5 mg kg–1 and soluble iron from 476 to 109 mg kg–1 of surface soil. The soil pH increased by 1.4 unit from its initial value and concentration of plant nutrients like N, P, K and microbial biomass content reached optimum fertility levels. Soluble iron and sulphate in drainage water reduced considerably by 26% and 49% respectively, with concurrent increases in water pH (3.2 to 7.2). Rice grain yield in the mined out area reached about 1320 kg ha–1 after reclamation as compared 1920 kg ha–1 in non-mined area. The adaptation of native plant species (Citrus reticulate, Prunus napalensis and Pyrus communis) was about 70%. Afforestation with native fruit plant species and ferns/grasses, soil amendment using lime and organic manure, and channelling of seepage water for checking acid mine drainage contamination of water bodies and crop fields were some of the measures that were effective in mitigating toxicity. Phytostabilization helped in reversing the trend and restoring soil fertility and plant growth due to a rise in soil organic matter, nutrient availability as well as biological activities.