硒酸钠添加下苗期水稻中硒-汞的分布特征

Distribution characteristics of selenium and mercury in seedling rice under selenate fortification

采用土培盆栽实验研究了在不同外源硒(硒酸钠)梯度(0,1 mg·kg-1,5 mg·kg-1)与外源汞(硫酸汞)梯度(0,0.5 mg·kg-1,1 mg·kg-1)条件下,苗期水稻根与地上部分中硒与汞的分布特征。结果显示,外源硒抑制了苗期水稻根与苗对汞的吸收与积累,苗期水稻对汞的吸收随外源硒增加而呈现降低趋势,5 mg·kg-1是外源硒处理与无硒处理组相比水稻根部汞含量的下降最多,达到36.83%,并使水稻苗的汞含量维持在较低水平。而外源汞添加量1mg·kg-1时水稻苗中硒含量达到(58.16±0.17)mg·kg-1,是相应无汞添加组的20.12倍,说明外源汞添加在一定程度上促进了苗期水稻对硒的吸收与累积。整体而言,水稻苗中的硒-汞的吸收迁移具有一定的相互作用,尤其在水稻苗中的硒-汞富集系数存在显著负相关关系(r=0.48),其可能的机制是硒在水稻根部与汞结合形成硒-汞络合物从而抑制水稻地上部分对汞的吸收,这对于利用硒酸钠来降低苗期水稻地上部分对汞的累积提供了数据基础。

An experiment was conducted to evaluate the bioaccumulation and interaction of selenium （Se） and mercury （Hg） in seedling rice via an indoor pot experiment. The germinated seedling rice was exposed to three different levels of Se as Na2SeO4 （0, 1 and 5 mg·kg-1） and Hg as HgSO4 （0, 0.5 and 1 mg·kg-1） for 3 weeks. The results showed that the Hg concentration in shoots tended to decrease with increased Se concentration, and the Hg concentration in roots decreased by 36.8 % when the Se concentration was 5 mg·kg-1 compared with the no Se group. Moreover, Hg, in a certain extent, promoted the uptake and accumulation of Se in seedling rice at low concentrations, and the Se contens in seedling rice was 20.12 times higher than those of no Hg group when the exogenous Hg concentration was 1 mg·kg-1. Overall, a negative relationship was observed between the bioac- cumulation factors （BAF） of Se and Hg in shoots, and the possible reason might be the formation of Se-Hg com- plex and block the uptake of Hg to shoots. The present findings could provide data basis to relieve the accumula- tion of Hg via Na2SeO4 fertilizer during seedling.