Mercury speciation in selenium enriched wheat plants exposed to mercury pollution

Abstract

Mercury (Hg) pollution in agricultural soils and its potential pathway to the human food chain continues being a health concern, whereas selenium (Se) biofortification of crops grown in Se-poor soil regions is becoming a common practice to avoid health issues derived from Se deficient diets. Understanding the pathway of Hg in plants grown under Se biofortification conditions is crucial for practical applications. In this work, the speciation of Hg in wheat plants grown hydroponically under different Se-biofortification treatments (selenite, selenate and a 1:1 mixture of both) have been investigated by X-ray absorption spectroscopy at the Hg L3-edge. The main Hg species found in wheat grains is the highly toxic methylmercury. We found that the Se-biofortification of wheat does not prevent, in general, the Hg translocation to grains. Only the 1:1 Se mixture treatment helps in reducing the levels of Hg and the presence of methylmercury in grains.