Why Study a Rice Field in Bangladesh?

January 9, 2008

The shallow aquifer in Bangladesh, which provides drinking water for millions and irrigation water for numerable rice fields, is severely contaminated with naturally occurring arsenic. The arsenic exposure is poisoning millions of Bangladeshis and causing thousands to die each year from arsenic-induced cancers. My research group is trying to determine the causes of the high concentrations of arsenic in groundwater.

Rice fields cover approximately 65% of the land area in our study area and water-balance calculations show that they contribute about half of the water that recharges the arsenic-contaminated aquifer every year. When I began my research, it was not clear what role rice fields play in the contamination problem. Rice fields can develop the chemical conditions needed to move arsenic off of the soil and into the water. (All soil, everywhere in the world, contains arsenic. Usually the arsenic remains associated with the soil and does not pose a health threat, but under certain chemical conditions it will dissolve into the surrounding water.) Thus, it is possible that the fields are contributing to arsenic to the shallow aquifer. However, the fields are irrigated with arsenic rich groundwater, which means a significant amount of arsenic is removed from the aquifer and placed onto the fields every year. Therefore, it is also possible that the rice fields act as a net sink for arsenic from the aquifer (i.e., more arsenic is removed from the aquifer then enters the aquifer because of the rice fields).

Figuring out the role of rice fields requires an investigation of both the hydrology and chemistry of a field. I need to determine flow patterns through a rice field and then investigate water chemistry along known flow paths. I will provide more information about my research methods and results in subsequent posts.