Accumulation of arsenic in rice plant from arsenic contaminated irrigation water and its effect on nutrient content

Abstract

To achieve self-sufficiency in food grain production, the HYV rice varieties are widely produced in Bangladesh, particularly in the dry season, and this requires a large volume of groundwater for irrigation. Groundwater of many areas of our country is severely contaminated with arsenic. So, there is a possibility of arsenic .accumulation in rice plants from arsenic contaminated irrigation water. Generally, consumption of protein is not adequate for our people due to insufficient production of major protein sources like fish, meat, milk, eggs, etc. and also due to economic constraints. Any adverse effect on protein content in rice due to use of arsenic contaminated irrigation water may, therefore, aggravate the malnutrition problem of our people. Similarly any adverse effect on amylose content, which is about one forth portion of rice grain by weight, would cause deficiencies in calorie supply. This study aims at assessing the accumulation of arsenic in rice plants and its possible effect on nutrient (protein and amylose) content of rice grains. Arsenic contents in different parts of rice plants were tested using hydride generation Atomic Absorption Spectrophotometry (Shimadzu, AA6800). For assessing nutrient contents (protein and amylose), rice samples were tested at the Laboratory of Grain Quality and Nutrition Division of Bangladesh Rice Research Institute (BRRI), Gazipur. Results from this study show that arsenic accumulates in different parts of rice plants, though the accumulation varies from variety to variety. Highest arsenic concentration was found in root hair with a mean 16.7 mglkg and maximum 38.5 mglkg, and least in grain with a mean 0.32 mglkg and maximum 1.1 mglkg. Mean arsenic concentrations in husk, leaf and stem were found to be 1.06 mglkg, 3.98 mglkg and 3.32 mglkg, respectively. Presence of arsenic in straw (leaf and stem) at moderately high concentration poses risks for cattle and human health. Arsenic concentration in top soil samples of study fields were found to be up to 12 mg/kg. From linear regression analysis only a moderate correlation (R2 = 0.45) was found between arsenic in water and arsenic in root hair. Measured nutrient contents were compared with the standard values. Test results for protein content show rice grain contain less protein than standard values. Similarly, for most samples, amylose content was found to be less than standard value. More studies are needed to better understand these phenomena.