On the distribution and speciation of arsenic in the soil-plant-system of a rice field in West-Bengal, India: A μ-synchrotron techniques based case study

In soil, As was mainly associated with Fe-(oxy)hydroxides. Rice root coatings consisted of a similar assemblage of arsenic bearing minerals. Furthermore the incorporation of soil matter in the coating could be shown. On μm-scale, As concentrations in rice root coatings showed an inhomogeneous, patchy distribution (100-2400 mg/kg; median 500 mg/kg) and correlated with Fe concentrations. Some small amounts of arsenic could also be detected in the interior of the root (3-60 mg/kg; median 21 mg/kg). In the rice grain, trace elements such as Zn and Cu were mainly enriched along the grain coating, while As in contrast showed the highest concentrations in the germ and some hot spots in the coating (up to 13 mg/kg). Thus, peeling of rice grain would remove some, but not all of the arsenic.