Simulated In-Situ Immobilization of Heavy Metals in Coffee Soils of South India

Abstract

Potentially hazardous pollutants like lead (Pb) and cadmium (Cd) find way into agricultural soils through phosphate fertilizers and sewage sludge and can accumulate over long periods. Chemical remediation of heavy metal polluted soils is gaining importance owing to the multifacet approach in creating ideal physical, chemical and biological conditions in the rhizosphere to ensure higher productivity. Two coffee growing soils (Mollic Kandiudalfs and Typic Rhodustalfs) of south India spiked with 100 mg kg-1 of each Pb and Cd were treated with ameliorants like zeolites (clinoptilolites), agricultural lime, potassium di-hydrogen orthophosphate (KH2PO4) and compost. Sequential extraction procedure was adopted to determine the phyto-available fractions. Potassium di-hydrogen orthophosphate was the most effective chemical in decreasing available Pb as indicated by the lowest phyto-available fraction in soils followed by zeolites, agricultural lime and compost. For Cd, agricultural lime was superior to other amendments in the moderate acidic soil (pH-5.6), while zeolite was the most effective in soil with pH of 7.2.