Department of Environmental Science and Engineering, Hunan Agricultural University, Changsha, 410128, PR China.
Department of Environmental Science and Engineering, Hunan Agricultural University, Changsha, 410128, PR China.
Ecotoxicol Environ Saf. 2019 Nov 30;184:109620. doi: 10.1016/j.ecoenv.2019.109620. Epub 2019 Sep 4.
The paddy-crusts (PCs) play an important pole in the transformation and transfer of heavy metal in paddy. Different PCs were collected from paddy fields whose soils contained cadmium (Cd) at four concentration levels (0.61, 0.71, 1.53, and 7.08 mg/kg) in Hunan Province, China P.R. at Sep 2017. This metal's distribution among and biological community structures of PCs were both measured. Our results indicated that PCs were able to accumulate Cd from irrigation water and soil. With greater Cd levels in paddy fields, the weak EPS-binding Cd fraction decreased whereas the non-EDTA-exchangeable Cd fraction increased. The sorbed Cd fraction was initially enhanced at low-to mid-level Cd concentrations, but then gradually declined. Biomineralization was shown to function as the dominant Cd accumulation mechanism in non-EDTA-exchangeable fractions. The biological diversity of soil microbes decreased with more Cd in soil, and the Proteobacteria, Bacteroidetes, and Cyanobacteria were the dominant phyla in all the sampled PCs. Canonical correspondence analysis (CCA) between the composition of microbial communities and soil chemical variables in the PCs clustered all samples based on the Cd-contaminated level, and demonstrated that Cd, Mn, and Fe all significantly influenced the microbial communities. In particular, the Alphaproteobacteria and Chloroplast classes of bacteria may play a significant role in Cd accumulation via the bio-mineralization process. Taken together, our results provide basic empirical information to better understand the heavy metal speciation transformation mechanisms of PCs upon Cd-contaminated paddy fields.
水稻壳在水稻中重金属的转化和迁移过程中起着重要的作用。2017 年 9 月，在中国湖南省，从四个不同镉（Cd）浓度水平（0.61、0.71、1.53 和 7.08mg/kg）的稻田中采集了不同的水稻壳。测量了该金属在水稻壳中的分布和生物群落结构。结果表明，水稻壳能够从灌溉水和土壤中积累 Cd。随着稻田中 Cd 含量的增加，弱 EPS 结合 Cd 分数减少，而非 EDTA 可交换 Cd 分数增加。被吸附的 Cd 分数在低到中等 Cd 浓度下最初增加，但随后逐渐下降。生物矿化被证明是不可用 EDTA 交换的分数中 Cd 积累的主要机制。土壤微生物的生物多样性随着土壤中 Cd 的增加而减少，变形菌门、拟杆菌门和蓝藻门是所有采集的水稻壳中的主要门。PCs 中微生物群落组成与土壤化学变量之间的典范对应分析（CCA）根据 Cd 污染水平对所有样品进行聚类，并表明 Cd、Mn 和 Fe 均显著影响微生物群落。特别是，细菌的 Alphaproteobacteria 和叶绿体类群可能通过生物矿化过程在 Cd 积累中发挥重要作用。总之，我们的研究结果为更好地理解受 Cd 污染的稻田中水稻壳对重金属形态转化机制提供了基本的经验信息。
