Arsenic in irrigation water : a threat for rice cultivation?

• Frequent cultivation of high yielding rice varieties (HYV) for increased food production are the key reasons for massive application of groundwater based irrigation in the rice fields of Bangladesh. Including the Asian continent, more than half of the world’s population chooses rice as their staple food and it is already considered as one of the major sources of inorganic arsenic (As) intake in the human body through food stuffs. The water logged rice cultivation method also has influence on As accumulation in rice grain. The study area Matlab located in southeastern Bangladesh, which is identified as a prominent As hotspot with incidences of high level of As in the groundwater. The objective of this study was to find out the influence of irrigation water quality and soil on the level of As in rice grain and more specifically identify the influence of iron (Fe), silicon (Si) and phosphorus (P) in the soil on the As uptake in the rice grain. A number of previous laboratory based studies has found, all three elements exert significant control on the biogeochemical interactions of As in soils and uptake in the plants.The aim of this study was to compare the level of As in rice grain and bran of different HYVs and local rice varieties, grown in this region and to compare the results with the levels of Fe, Si and P in the irrigated soils. The ICP-OES based analysis showed that the total As concentration (5.74-16.78 mg Askg-1) in the soil samples from the rice fields of the area (n=9) has exceeded the average global As concentration in the crust and soils. The concentration of Fe and Si in the soil was positively correlated with total As in the soil. The As analogue, P was positively correlated with As (R2=0.52) in the soil samples. The arsenic concentration in the irrigation water of that particular area was (> 200 μg As l -1) The AAS based analysis found that the total arsenic concentration ranged (0.017- 0.23 mg As kg-1) in the grain whereas [Asbran] was higher compared with the grains. High level of Fe present in the soil could play a significant role on the bioavailability of As due to its sorption onto the surface of the Fe-oxide colloids and roots of the rice plants. To address the As bioavailability in the rice grain, the level of As influencing elements in both grain and bran should be focused in further investigation.

Subject headings

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geokemi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geochemistry (hsv//eng)

Publication and Content Type

ref (subject category)

kon (subject category)