Ground Water Arsenic Contamination and Its Accumulation into Different Varieties of Rice

Abstract

HYV rice BR-11 and BRRI dhan-50 were grown in an open-field Gangetic soil conditions with arsenic amended irrigation water and normal tap-water in experimental plot at Institute of Environmental Science of University of Rajshahi during August to December 2011 and February to June 2012, respectively. Whereas HYV rice BRRI dhan-36, local Boro variety Somsi and local Aman varieties (Mowka and Shorna) were also cultivated in an actual paddy field conditions with arsenic contaminated STW irrigation water in experimental plots at Mandal para village of Shahbajpur union under Shibganj upazila of Chapai Nawabganj district of Bangladesh during February to June 2012 and July to November 2012, respectively. The main objectives of this study were to observe the effect of arsenic (As) on rice (Oryza sativa L.) plants and the effect of arsenic contaminated pump distance and paddy field elevation on arsenic accumulation into HYV Boro and Aman rice. The tillers number, panicle length and grain yield of BR-11 rice were found to decrease significantly (p≤0.05) with increase of arsenic (As) concentration in irrigation water. Arsenic in irrigation water showed a strong positive correlations with arsenic accumulation into soil, straw and grain, and the trend of accumulation was found as water > soil > straw > grain. Chlorophyll contents of BRRI dhan-50 rice leaves were significantly decreased with increasing of soil residual arsenic. Grain and straw yield were not significantly affected by soil residual arsenic. A significant (p ≤ 0.01) increasing trend of arsenic accumulation into straw and grain was observed with increasing of soil residual arsenic. Arsenic accumulation in drainage sediments, paddy field soil, rice straw and grain were decreased significantly (p<0.01) with increasing of arsenic contaminated pump distance during dry season for Boro cultivation period. Arsenic accumulation in paddy soil, rice straw and grain had significant (p<0.01) negative correlation with paddy field elevation from mean sea level during Aman period (rainy season). Dry season hybrid rice varieties (BRRI dhan 50, BRRI dhan 36) accumulated more arsenic than rainy season local non-hybrid rice varieties. Highest arsenic accumulation in rice grain was 0.97±0.01 mg/kg, but not exceeded the WHO recommended permissible limit 1 mg/kg. Local non-hybrid rice varieties should be selected for arsenic contaminated area. Rice cultivation in upland and irrigation from distanced pump is suggested for less arsenic contamination.