Abstract
The ecological rehabilitation of potential toxic metal-contaminated soils in sites disturbed by mining has been a great challenge in recent decades. Phytoremediation is one of the most widely promoted renovation methods due to its environmental friendliness and low cost. However, there is a lack of in situ investigation on the influence of vegetation pattern and spontaneous succession on the rehabilitation of potential toxic metal-polluted soil. To clarify how the vegetation pattern in the early stage of restoration and the spontaneous succession influence the remediation of the soil, we investigated a metal mining dump in Sichuan, China, by field investigation and laboratory analysis. We determined the plant growth, soil fertility, and the capacity of potential toxic metals (PTMs) in metal mining soil under different initial vegetation patterns for different years to understand the role of vegetation pattern and spontaneous succession in PTM pollution phytoremediation projects. The results show that: (1) Phytoremediation with a simple initial vegetation pattern (RP rehabilitative plant pattern) which involves two rehabilitation plants, Agave sisalana and Neyraudia reynaudiana, achieves a PTM pollution index that is 9.28% lower than that obtained with the complex vegetation pattern (RP&LP rehabilitation plants mixed with local plants pattern), 21.86% lower in the soil fertility index, and 73.69% lower in the biodiversity index; (2) The phytoremediation with the 10-year RP&LP pattern was associated with a PTM pollution index that was 4.04% higher than that for the 17-year RP&LP pattern, a soil fertility index that was 4.48% lower, and a biodiversity index that was 12.49% lower. During the process of vegetation succession, if accumulator plants face inhibition of growth or retreat, the reclamation rate will decrease. The vegetation patterns influence the effect of phytoremediation. Spontaneous vegetation succession will cause the phytoremediation process to deviate from the intended target. Therefore, according to the goal of vegetation restoration, choosing a suitable vegetation pattern is the main premise to ensure the effect of phytoremediation. The indispensable manipulation of succession is significant during the succession series, and more attention should be paid to the rehabilitative plants to ensure the stable effect of reclamation. The results obtained in this study could provide a guideline for the in situ remediation of PTM-polluted soil in China.
Highlights
The large amount of potential toxic metals present in the tailings of metal mines is an important source of potential toxic metal pollution in soil [1,2,3,4]
There are few studies on the interactions between vegetation patterns and spontaneous succession regarding their effect on the remediation of soil potential toxic metal concentrations. To fill this knowledge gap, we investigated plant biodiversity, soil fertility, and the potential toxic metal content in the soil of reclaimed potential toxic metal mining sites under different vegetation patterns, i.e., rehabilitative plant (RP) and rehabilitative plant and local plant (RP&LP), for project durations of 10 years and 17 years
Phytoremediation is the preferred method of the remediation of soil pollution from potential toxic metal mines
Summary
The large amount of potential toxic metals present in the tailings of metal mines is an important source of potential toxic metal pollution in soil [1,2,3,4]. Genetics may be used to produce new high accumulation plants [13] These plants can absorb potential toxic metals in soil and reduce the negative effects on ecosystem health [2,14]. Molecular tools are being used to better understand the mechanisms of metal uptake, translocation, sequestration, and tolerance in plants [13,15] These efforts can promote the development of agromining and phytomining [16,17,18]. The area displayed reduced biological activity, pH, and organic carbon levels [20,21,22] Another troubling aspect is that fertilizer application is required to increase the concentrations of N, P, and K to initiate the restoration process [22,23,24]
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