Effects of sodium sulfide application on the growth of Robinia pseudoacacia, heavy metal immobilization, and soil microbial activity in Pb-Zn polluted soil.

Sodium sulfide (Na ₂ S) is usually used as an amendment in industrial sewage treatment. To evaluate the effects of Na ₂ S on the growth of Robinia pseudoacacia (black locust), heavy metal immobilization, and soil microbial activity, the R. pseudoacacia biomass and nutrient content and the soil heavy metal bioavailability, enzyme activity, and arbuscular mycorrhizal (AM) fungal community were measured by a single-factor pot experiment. The Pb-Zn-contaminated soil was collected from a Pb-Zn mine that had been remediated by R. pseudoacacia for five years. Three pollution levels (unpolluted, mildly polluted, and severely polluted) were evaluated by the pollution load index. Na ₂ S application increased the shoot biomass under severe and mild contamination. In soil, Na ₂ S application decreased the bioavailable Pb and Zn contents under severe and mild contamination, which resulted in a decrease in the Pb and Zn content in R. pseudoacacia. However, Na ₂ S application did not affect the total Pb content per plant and enhanced the total Zn content per plant because of the higher biomass of the plants under Na ₂ S application. Increased phosphatase activity and increased available phosphorous content may promote the uptake of phosphorus in R. pseudoacacia. Moreover, Na ₂ S application is beneficial to the diversity of AM fungi under mild and severe pollution. Overall, Na ₂ S application has great potential for enhancing soil heavy metal immobilization, enhancing soil microbial activity, and improving the growth of R. pseudoacacia in polluted soils. Therefore, Na ₂ S is suitable for use in Pb-Zn remediation to ameliorate environmental heavy metal pollution.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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