贵州丹寨废弃矿区典型农作物中汞、砷含量的分布特征及差异分析

Distribution and Difference of Mercury and Arsenic in Typical Crops of an Abandoned Mining Area in Danzhai,Guizhou Province of China

为摸清废弃矿区重金属汞(Hg)、砷(As)在典型农作物中的含量和空间分布特征,于丹寨金汞矿废弃矿区选取当地主要种植作物-玉米和水稻,采用冷原子荧光光谱法和电感耦合等离子体质谱法分别对农作物Hg、As进行定量分析。结果表明:玉米植株中,茎叶Hg、As出现部分超标点,点位超标率分别为42.11%和5.26%,玉米果实中Hg、As均未超标;玉米Hg、As的空间分布特征表现为距离污染源越远浓度越低。而水稻植株中,茎叶及籽实Hg、As点位超标率和超标倍数均高于玉米,其中水稻茎叶Hg、As点位超标率分别为73.33%和26.67%;水稻中Hg含量随污染源距离的增加而降低,As随污染源距离的增加而增加。相关性研究表明,茎叶Hg和果实Hg不存在显著相关关系,而茎叶As和果实As存在较好的相关性,表明Hg在作物器官中的分布不均匀,而As的分布相对较均匀。玉米和水稻地上部分对Hg、As的生物富集系数均小于0.05,表明玉米和水稻从土壤吸收、并向地上部分转移Hg、As的能力较弱。金属Hg在农作物中的含量及富集系数均低于As,这可能与土壤重金属含量、矿区污染物的释放以及作物本身的耐受性和吸收机制不同有关。

Corn and rice samples were collected from an abandoned gold mining area,Danzhai,to explore the contents of Hg and As in these typical crops and the spatial distribution. Hg and As in crops were determined by cold atomic fluorescence spectrometry and inductively coupled plasma mass spectrometry,respectively. The results showed that the ratio surpass the standard of Hg and As in corn stem-leafs were 42. 11% and 5. 26%,respectively;and Hg,As in corn fruits were not exceed the standard. Spatially,Hg and As in corns decreased with increasing distance to the pollution source. For rice plants,the ratio of Hg and As surpassing the standard were much higher than those of corns,with 73. 33% and 26. 67% of samples exceeded the standard in stem-leafs and seeds,respectively.The Hg content in rice decreased with the increase of the distance to the pollution source,while As increased with the distance to the pollution source. The correlation analysis showed that there was no significant correlation between stem-leaf Hg and fruit Hg,but there was a good correlation between stem-leaf As and fruit As,indicating that the distribution of Hg is more inhomogeneous than As in crop organs. The BCFs of Hg and As in the aboveground biomass were all less than 0. 05,indicating that the ability of crops to absorb Hg and As from soil and then transfer them is poor. The content and enrichment coefficient of Hg in crops were lower than As,which may be related to the difference in contents of heavy metals in soil,the release of pollutants and the absorption mechanism in crops.