Abstract
A shocking Longjiang River cadmium pollution accident occurred in 2012, the effects of which on microbial communities remain unclear. Alkaline precipitation technology was applied for remediation, but concerns rose about the stability of this technology. To understand the geographic distribution of cadmium and its correlation with microbes, in this study, 39 water samples and 39 sludge samples from this river and 2 soil samples from the nearby farmland were collected for chemical and microbial analyses. The Cd concentrations of all water samples were lower than 0.005 mg/L and reached the quality standards for Chinese surface water. A ranking of sludge samples based on Cd contents showed sewage outfall > dosing sites > farmland, all of which were higher than the quality standard for soil. Alkaline precipitation technology was effective for Cd precipitation. Cd was unstable; it was constantly dissolving and being released from the sludge. The Cd content of each phase was mainly influenced by the total Cd content. Over 40,000 effective sequences were detected in each sample, and a total of 59,833 OTUs and 1,273 genera were found using Illumina MiSeq sequencing. Two phyla and 39 genera were notably positively correlated with the Cd distribution, while the cases of 10 phyla and 6 genera were the opposite.
Highlights
In Guangxi Zhuang Autonomous Region of China, nonferrous metal industries are mainly concentrated in the Longjiang River basin, where the major grain producing area occurs
Microorganisms are sensitive to heavy metals[15], and contamination by heavy metals has a significant influence on changes in bacterial community structure[16], microbial biomass[17] and microbial diversity[18]
Higher Cd content in the dosing site samples indicated that some Cd was precipitated from the river water to sludge and that the weak alkaline chemical precipitation technology used to remove Cd from river water had some effects in 2012
Summary
In Guangxi Zhuang Autonomous Region of China, nonferrous metal industries are mainly concentrated in the Longjiang River basin, where the major grain producing area occurs. The geographic distribution, existence form and stability of the precipitated Cd in the Longjiang River are in need of research. Metals (Fe, Ni and Zn)[29] and Cr30 changed the bacterial community composition of river sediments. In heavy metal polluted sites, high throughput sequencing has been widely used, for example, to determine the microbial community of the Cd-, Zn-, Ni-, and Fe-contaminated Nanfei River[29], a Leforest site with higher Cd, Zn and Mn32, soil containing Cd and Zn33, and mining soils contaminated with Cu and Zn34.
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