ARSENIC IN IRRIGATION WATER: A POTENTIAL CAUSE OF INCREASED ARSENIC CONCENTRATION IN SOIL-RICE SYSTEM

Presence of high level of arsenic in the groundwater is one of the major environmental disasters in Bangladesh. A number of mitigation options for providing drinking water have been executed in the affected area in Bangladesh to reduce arsenic exposure to humans. However, the agricultural management system in Bangladesh much depends on the groundwater irrigation system due to tropical climate. Mainly the geogenic reasons are responsible for high level of arsenic in the aquifers of Bengal delta region. In order to understand arsenic mobilization in the water-soil-plant a prominent arsenic hotspot agriculture site, Matlab in Bangladesh (23° 20' 15.31"N 90° 45' 10.31"E) was selected for this study. The aim was to assess the concentration of arsenic transfer to rice via the irrigated fields through arsenic contaminated irrigation water and other influencing elements for example phosphorus (P), as arsenic uptake from soil is influenced by the presence of P, due to similarity between As and P. ICP-OES based analysis of irrigation water samples showed arsenic concentration in the irrigation points to be 8.34-249.69 μg As L^-1 (n=12) which is similar to the standing water (7.78-223.54 μg L^-1 As; n=9) in the irrigated fields. The As concentration in 2 of the samples are above the guideline value for irrigation water (100 μg L^-1 As). Presence of high level of P in the irrigation samples (134-2396.85 μg P L^-1) and its analogue with As in the irrigation water could be one of the major reasons for arsenic accumulation in the rice grain. The reason is that As and P interacts at soil binding sites.