Arsenic uptake by rice and accumulation in soil amended with municipal solid waste compost

Effect of municipal solid waste compost (MSWC) on arsenic content of submerged rice paddies was studied. Experiments were conducted during the three consecutive wet seasons from 1997 to 1999 on rice grown under submergence, at the Experimental Farm of Calcutta University, India. A sequential extraction method was used to determine the various arsenic fractions in MSWC and cow dung manure (CDM). Arsenic (As) was significantly bound to the organic matter and iron (Fe) and manganese (Mn) oxides in MSWC and CDM. Arsenic content in rice straw was higher than rice grain. Arsenic bound with Fe and Mn oxides best correlated with straw As (r = + 0.99**) and grain As (r = + 0.99**) content. The As bound with organic matter followed next (r = + 0.98** for straw, and r = + 0.94* for grain) with the exchangeable part being also significant with straw (r = + 0.94*). In CDM, the As content of rice grain correlated best with water soluble As (r = + 0.96**) while the straw As content was best correlated with exchangeable As (r = + 0.99**) followed by As bound with organic matter (r = + 0.98**). MSWC effectively served as binding agent for native soil arsenic thereby moderating the rapid arsenic mobilization to the crop rhizosphere.