Experiments on Alleviating Arsenic Accumulation in Rice Through Irrigation Management

Abstract

Arsenic (As) in groundwater is a major health concern in Bangladesh and the risks of As ingestion using shallow tubewells (STWs) for drinking-water was identified in the deltaic region, particularly in the Gangetic alluvium of Bengal including Bangladesh and West Bengal of India during the early nineties. It has been termed the world’s biggest natural calamity in known human history. Ground water is the primary source of drinking water for approximately 90% of the total 147 million people (WHO 2001). More than 35 million people of Bangladesh are exposed to an As contamination in drinking water exceeding the national standard of 50 μg L-1 while an estimated 57 million people are at the risk of exposure to As contamination exceeding the WHO guideline of 10 μg L-1 (BGS/DPHE 2001). Extensive contamination in Bangladesh was confirmed in 1995, when additional survey showed contamination of mostly shallow tube-wells (STWs) across much of southern and central Bangladesh (Imamul Huq et al. 2006a). However, a few instances of deep tube-wells (DTWs) contamination are also in report. Approximately 27% of STWs and 1% of DTWs in 270 upazillas (sub-districts) of the country are contaminated with As at Bangladesh standard whereas about 46% of STWs are contaminated at WHO standard. So far 38,000 persons have been diagnosed with an additional of 30 million people at risk of As exposure (APSU 2005). Concentrations of arsenic exceeding 1,000 μg L-1 in shallow tube-wells were reported from 17 districts in Bangladesh (Ahmed et al. 2006). Efforts are being directed towards ensuring safe drinking water either through mitigation technique or through finding alternative sources. Even if an As-safe drinking water supply could be ensured, the same groundwater will continue to be used for irrigation purpose, leaving a risk of soil accumulation of this toxic element and eventual exposure to the food-chain through plant uptake and animal consumption (Imamul Huq 2008). Given the studies on As uptake by crops (Imamul Huq et al. 2001; Abedin et al. 2002; Ali et al. 2003; Islam et al. 2005) there is much potential for the transfer of As present in groundwater to crops. The use of groundwater for irrigation has increased abruptly over the last couple of decades. About 86% of the total groundwater withdrawn is utilized in the agricultural sector