Effects of heavy metals on bacterial community surrounding Bijiashan mining area located in northwest China.

Heavy metal (HM) pollution is a severe and common environmental problem in mining area soil. It is imperative to understand the micro ecological characteristics of mining area soil for HM contaminated soil remediation. This study described the effects of HM pollution level and soil physical and chemical parameters on microbial diversity. In this study, high-throughput sequencing technology was used to study the effects of HM pollution on the diversity and composition of the soil microbial community. The soil groups were barren, exhibiting alkaline pH, low total nitrogen (TN), and total potassium (TK) according to soil fertility standard. Compared with the control group, there was severe multiple HM pollution in the other five groups, including lead (Pb), cadmium (Cd), zinc (Zn), and copper (Cu). The dominant phyla accounting for more than 1% of the overall community in all soil groups were Proteobacteria (34.432 ± 7.478%), Actinobacteria (22.947 ± 4.297%), Acidobacteria (10.47 ± 2.439%), Chloroflexi (7.89 ± 2.980%), Planctomycetota (5.993 ± 1.558%), Bacteroidota (4.275 ± 1.980%), Cyanobacteria (3.478 ± 2.196%), Myxococcus (2.888 ± 0.822%), Gemmatimonadota (2.448 ± 0.447%), Firmicutes (1.193 ± 0.634%), Patescibacteria (0.435 ± 0.813%), and Nitrospirota (0.612 ± 0.468%). Proteobacteria and Actinobacteria were predominant at the phylum level, which showed a certain tolerance to HMs. In addition, redundancy analysis (RDA) results showed that Pb, Cu, Zn, and Cd were strongly correlated with each other (P < 0.01). Other nutrient elements (except for TK) were significantly positively correlated with each other. Cu and nutrient element TK had an important impact on bacterial community structure. Therefore, bacteria with the function of HM tolerance and bioremediation in extreme environments should be researched, which provides a foundation for future ecological remediation of contaminated soil by using microbial remediation technology.

Effects of heavy metals on bacterial community structures in two lead-zinc tailings situated in northwestern China.

We evaluated the variations of bacterial communities in six heavy metal contaminated soils sampled from Yanzi Bian (YZB) and Shanping Cun (SPC) tailings located in northwestern China. Statistical analysis showed that both the heavy metals and soil chemical properties could affect the structure and diversity of the bacterial communities in the tailing soils. Cd, Cu, Zn, Cr, Pb, pH, SOM (soil organic matters), TP (total phosphorus) and TN (total nitrogen) were the main driving factors of the bacterial community variations. As a consequence, the relative abundances of certain bacterial phyla including Proteobacteria, Chloroflexi, Firmicutes, Nitrospirota and Bacteroidota were significantly increased in the tailing soils. Further, we found that the abundance increasement of these phyla were mainly contributed by certain species, such as s__unclassified_g__Thiobacillus (Proteobacteria), s__unclassified_g__Sulfobacillus (Firmicutes) and Leptospirillum ferriphilum (Nitrospirota). Thus, these species were considered to be strongly heavy metal tolerant. Together, our findings will provide a useful insight for further bioremediations of these contaminated areas.

Interactions between Silicon Oxide Nanoparticles (SONPs) and U(VI) Contaminations: Effects of pH, Temperature and Natural Organic Matters.

The interactions between contaminations of U(VI) and silicon oxide nanoparticles (SONPs), both of which have been widely used in modern industry and induced serious environmental challenge due to their high mobility, bioavailability, and toxicity, were studied under different environmental conditions such as pH, temperature, and natural organic matters (NOMs) by using both batch and spectroscopic approaches. The results showed that the accumulation process, i.e., sorption, of U(VI) on SONPs was strongly dependent on pH and ionic strength, demonstrating that possible outer- and/or inner-sphere complexes were controlling the sorption process of U(VI) on SONPs in the observed pH range. Humic acid (HA), one dominated component of NOMs, bounded SONPs can enhance U(VI) sorption below pH~4.5, whereas restrain at high pH range. The reversible sorption of U(VI) on SONPs possibly indicated that the outer-sphere complexes were prevalent at pH 5. However, an irreversible interaction of U(VI) was observed in the presence of HA (Fig 1). It was mainly due to the ternary SONPs-HA-U(VI) complexes (Type A Complexes). After SONPs adsorbed U(VI), the particle size in suspension was apparently increased from ~240 nm to ~350 nm. These results showed that toxicity of both SONPs and U(VI) will decrease to some extent after the interaction in the environment. These findings are key for providing useful information on the possible mutual interactions among different contaminants in the environment.