RESUMO
In the present study, experiments were conducted to assess the influence of nanoscale sulfur in the microbial community structure of metallophytes in Hg-contaminated rhizosphere soil for planting rapeseed. The results showed that the richness and diversity of the rhizobacteria community decreased significantly under Hg stress, but increased slightly after SNPs addition, with a reduction in the loss of Hg-sensitive microorganisms. Moreover, all changes in the relative abundances of the top ten phyla influenced by Hg treatment were reverted when subjected to Hg + SNPs treatment, except for Myxococcota and Bacteroidota. Similarly, the top five genera, whose relative abundance decreased the most under Hg alone compared to CK, increased by 19.05%-54.66% under Hg + SNPs treatment compared with Hg alone. Furthermore, the relative abundance of Sphingomonas, as one of the dominant genera for both CK and Hg + SNPs treatment, was actively correlated with plant growth. Rhizobacteria, like Pedobacter and Massilia, were significantly decreased under Hg + SNPs and were positively linked to Hg accumulation in plants. This study suggested that SNPs could create a healthier soil microecological environment by reversing the effect of Hg on the relative abundance of microorganisms, thereby assisting microorganisms to remediate heavy metal-contaminated soil and reduce the stress of heavy metals on plants.
In this manuscript, we first comprehensively investigated the changes in the rhizosphere microbial community structure of metallophytes in Hg-contaminated soil with SNPs addition, as well as the relationship between soil microbiology and plant resistance to Hg stress. Our results demonstrated that SNPs exhibit a significant advantage in improving rhizosphere microecology by increasing the abundance of beneficial rhizobacteria, thereby alleviating heavy metal toxicity, and promoting plant growth. This study is the first study describing the response of soil microorganisms coexposed to heavy metals and SNPs, providing valuable information for the potential use of SNPs to assist phytoremediation of toxic metal pollution and its impact on soil microbial communities.
RESUMO
Mercury (Hg) pollution has seriously threatened the crop productivity and food security. In the present research, experiments were conducted to assess the influence of nanoscale sulfur/sulfur nanoparticles and the corresponding bulk and ionic sulfur forms on the growth and Hg accumulation of oilseed rape seedlings grown on Hg-contaminated soil, as well as the transformation of soil Hg fractions. The results showed a significant reduction in fresh biomass for seedlings grown on 80-200 mg/kg Hg-polluted soil after 30 days. At 120 mg/kg Hg treatment, 100-300 mg/kg sulfur nanoparticles (SNPs) application counteracted Hg toxicity more effectively compared to the corresponding bulk sulfur particles (BSPs) and ionic sulfur (sulfate) treatments. The seedlings treated with 120 mg/kg Hg + 300 mg/kg SNPs gained 54.2 and 56.9% more shoot and root biomass, respectively, compared to those treated with Hg alone. Meanwhile, 300 mg/kg SNPs application decreased Hg accumulation by 18.9 and 76.5% in shoots and roots, respectively, relative to Hg alone treatment.SNPs treatment caused more Hg to be blocked in the soil and accumulating significantly less Hg in plants as compared to other S forms. The chemical fractions of Hg in the soil were subsequently investigated, and the solubility of Hg was significantly decreased by applying SNPs to the soil. Especially 200-300 mg/kg SNPs treatments caused the ratio of the soluble/exchangeable and the specifically absorbed fraction to be the lowest, accounting for 1.95-4.13% of the total Hg of soil. These findings suggest that adding SNPs to Hg-contaminated soils could be an effective measure for immobilizing soluble Hg and decreasing the Hg concentration in the edible parts of crops. The results of the current study hold promise for the practical application of SNPs to Hg-contaminated farmland for better yields and simultaneously increasing the food safety.
The novelty of this study is the selection of oilseed rape and nanoscale sulfur (NS) or sulfur nanoparticles (SNPs) as nontoxic nanomaterial to counteract the Hg toxicity and accumulation. Oilseed rape was selected due to its wide adaptability to various environmental conditions and the high-value oil for human consumption and biofuels production. These advantages make oilseed rape a highly valuable crop for various applications. NS was selected due to its reported ability to limit the uptake of heavy metals in oilseed rape, rice, and wheat along with other crops and subsequently restrict the toxicity of heavy metals in these plants and improve food safety. In this study, we evaluated the growth, Hg accumulation, and the resulting toxicity in oilseed rape grown on Hg-contaminated soil, with or without amendments with NS. The outcomes from this study provided evidence of the significant potential of NS in preventing Hg bioaccumulation and improving crop yields in oilseed rape. This provides opportunity to use NS as an ideal non-GMO approach to limit toxic metals in crops.