31-12 Characterisation of Rice Paddy Redox Conditions Driving Arsenic Accumulation within Cambodian Rice

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 38

Presenting Author:

Sienna Chambial

Authors:

Chambial, Sienna¹, Stahl, Mason², Lim, Alexandra³, Casassa, Amelia⁴, Lawless, Keith⁵, Phin, Samnang⁶, Phan, Kongkea⁷, Phan, Samrach⁸, Coleman, Eva⁹, Thompson, Emma¹⁰, Tran, My-Thu¹¹, Sousa, Daniel¹², Kothandaraman, Chellam¹³, Halpert, Eden¹⁴, Bostick, Benjamin¹⁵

(1) Department of Geosciences, Union College, Schenectady, New York, USA, (2) Department of Geosciences, Union College, Schenectady, New York, USA, (3) Department of Geosciences, Union College, Schenectady, New York, USA, (4) Department of Geosciences, Union College, Schenectady, New York, USA, (5) Department of Geosciences, Union College, Schenectady, New York, USA, (6) Water Innovation Lab, Kampong Cham, Cambodia, (7) Water Innovation Lab, Kampong Cham, Cambodia, (8) Water Innovation Lab, Kampong Cham, Cambodia, (9) Department of Geography, San Diego State University, San Diego, California, USA, (10) Department of Geography, San Diego State University, San Diego, California, USA, (11) Department of Geography, San Diego State University, San Diego, California, USA, (12) Department of Geography, San Diego State University, San Diego, California, USA, (13) Barnard College, New York, New York, USA, (14) Lamont Doherty Earth Observatory, Columbia University, New York, New York, USA, (15) Lamont Doherty Earth Observatory, Columbia University, New York, New York, USA,

Abstract:

Rice accounts for 20% of the world’s annual calorie consumption. Due to the rice crop’s unique physiology, it is susceptible to arsenic uptake from soil, leading to its accumulation within the grain. Arsenic is a toxic metalloid widely occurring in soils across the world. Seasonal flooding of rice paddies creates reducing conditions that can lead to the reductive dissolution of arsenic-bearing minerals, in particular iron oxides. Upon dissolution, these minerals can release arsenic into the pore water, allowing for its uptake into the rice grain. Arsenic is toxic to the rice plant, significantly reducing crop yield, and is toxic to humans who consume it.

To better understand the environmental factors that govern arsenic mobility within soils, as well as its subsequent accumulation within the grain, we sampled rice grain, leaves, soils, and water from paddies across a wide geographical range in Cambodia. The country’s reliance on rice for 60% of its caloric intake as well as the widespread traditional farming practices, make Cambodia an ideal location for this research. Soil reflectance measurements of nearly 200 rice paddies across Cambodia were made using a visible reflectance spectrophotometer. We also deployed synthetic iron oxide strips across a subset of these fields to assess their utility as indicators of reduction in soil (IRIS). 

Here, we present the results of IRIS strip measurements and visible reflectance spectroscopy of soil, and link them to soil and rice grain arsenic levels. Our research suggests that spectroscopy of soil within the visible light spectrum is predictive of rice grain arsenic and soil redox conditions. In particular, we find that the spectral slope of reflected light at specific wavelengths correlates with soil arsenic concentrations. This research demonstrates the potential of spectroscopy in predicting rice grain quality before the crop is even planted in a field. Our findings can lead to increased public health and food security in nations like Cambodia where rice is a staple.

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