Mitigation of Arsenic Accumulation in Crop Plants Using Biofertilizer

Abstract

Elevated levels of arsenic in crop plants have been found in various regions worldwide, especially where agricultural soils have been affected by arsenic-enriched aquifer and human activities including mining, smelting, pesticide application and so forth. Given the highly toxic nature of arsenic, it is highly recommended that remediation should be carried out immediately to reduce this potentially toxic element transport from soil to crop plants. There are numerous methods to remediate arsenic contamination in soil, however, approaches for remediation of arsenic contaminated paddy soil to reduce arsenic accumulation crop plants have not been widely investigated. This study focused on the utilization of biofertilizer which is a combination of arsenic-accumulating microorganisms and adsorbent (or carrier) in order to achieve high efficiency of arsenic immobilization and ability to apply in the field. Thirty-two bacterial strains were isolated from 9 soil samples collected from Dongjin and Duckum mining areas in Korea using nutrient medium amended with 2mM sodium arsenite. Among isolates, the strain DE12, which was identified as Bacillus megaterium, exhibited greatest arsenic accumulation capacity (0.236 mg/g dry biomass) and ability to resist up to 18mM arsenite and 14 mM arsenate. Among 3 agricultural waste adsorbents studied, rice straw was proved to have higher adsorption capacity (0.104 mg/g) than rice husk and coconut husk. Therefore, rice straw was chosen to be the carrier to form biofertilizer together with the strain DE12. Inoculation of biofertilizer in soil showed reduction of arsenic content in edible part of lettuce, morning glory and sweet basil by 17.5%, 34.1% and 34,1%, respectively compared to control group. Apart from arsenic, heavy metal analysis in these parts of lettuce also revealed the reduction of Pb content when applying biofertilizer. The use of biofertilizer may open up the potential application in the field for other food plants.