Investigation of Hg uptake and transport between paddy soil and rice seeds combining Hg isotopic composition and speciation

C Feng,M Monperrus,P Li,S Berail,B Du,X Feng,E Tessier,D Amouroux,Z Pedrero

doi:10.12952/journal.elementa.000087

Abstract

Abstract Human consumption of rice constitutes a potential toxicological risk in mercury (Hg) polluted areas such as Hg mining regions in China. It is recognized to be an important source of Hg for the local human diet considering the efficient bioaccumulation of methylmercury (MeHg) in rice seed. To assess Hg sources and uptake pathways to the rice plants, Hg speciation and isotopic composition were investigated in rice seeds and their corresponding paddy soils from different locations within the Wanshan Hg mining area (Guizhou Province, China). A large variation of Hg speciation is observed in rice seeds and paddy soils irrespective of the sampling location. Mass dependent fractionation (MDF) of Hg in rice seeds differs by up to ∼4.0 ‰ in δ202Hg values, while mass independent fractionation (MIF) of Hg isotopes remains constant (Δ199Hg ∼ 0‰). Hg isotopic composition in rice seeds covaries with that of paddy soils but exhibits lighter isotopic signature (δ202Hg). Such isotopic offset is mainly attributed to plant uptake and translocation processes. Also, seeds containing higher MeHg (MeHg/total Hg &gt; 50%) have significantly heavier Hg isotopes suggesting that MeHg uptake and transport to the seed in such rice plants is facilitated compared to inorganic Hg.

Highlights

Mercury (Hg) is a pollutant of major concern that can be bioaccumulated and biomagnified in the trophic web, resulting in potential negative effects on human health (Driscoll et al, 2013; Mergler et al, 2007; WHO, 1990)
According to the classification of “seriously contaminated” and “less impacted” areas giving by Zhang et al, (2010), the samples of our study should be included in the first group.The obtained values exceed the Chinese National Standard Agency permissible limit (20 ng g-1) (CNSA, 1994), indicating the impact of mining and smelting activity in the study area
The percentage of MeHg (%MeHg) fluctuates between 6 and 97% (Figure 2a, Table S4) and it is not related to the total Hg (THg) concentration in rice seeds (p>0.05)

Summary

Introduction

Mercury (Hg) is a pollutant of major concern that can be bioaccumulated and biomagnified in the trophic web, resulting in potential negative effects on human health (Driscoll et al, 2013; Mergler et al, 2007; WHO, 1990). To assess Hg sources and uptake pathways to the rice plants, Hg speciation and isotopic composition were investigated in rice seeds and their corresponding paddy soils from different locations within the Wanshan Hg mining area (Guizhou Province, China).

Results

Conclusion