[Characteristics of Plant Diversity and Heavy Metal Enrichment and Migration Under Different Ecological Restoration Modes in Abandoned Mining Areas].

In order to select plant materials suitable for the ecological restoration of abandoned mining land, ecological restoration experiments were set up in landfills. The effects of different ecological restoration measures on plant diversity and heavy metal enrichment and migration characteristics were studied. The results showed that under different ecological restoration measures, a total of eight families and 10 species of surviving plants appeared, most of which were herbs. The restoration effect of the arbor shrub and grass plots was the best; the plant coverage reached 100%, and the survival rate was over 69%. The diversity index of the plant community was as follows:arbor shrub grass > shrub grass > joe grass > grass. The dominant plants under different ecological restoration measures were Pinus elliottii, Ligustrum lucidum, Boehmeria nivea, Lagerstroemia indica, and Plantago asiatica. The contents of most heavy metals in plants were higher than the normal values. Among them, the enrichment and transfer coefficients of the leaf stems of P. elliottii and L. indica were close to or greater than 1, showing a strong ability of enrichment and transfer to Cd; these two plants belong to Cd-enrichment type plants. The roots of L. lucidum Ait and P. asiatica, which are root-hoarding plants, had a high retention rate of heavy metals. Boehmeria nivea was a heavy metal-avoidance plant with a low content of heavy metals in each part and had the ability to fix and repair potential soil heavy metal pollution. Considering the diversity of plants and the ability of plant enrichment and migration, the combination of trees, shrubs, and grasses was the best restoration mode. Pinus elliottii, L. indica, and P. asiatica can be the target plants for ecological restoration in the abandoned land of mining areas.

[Reconstructed Soil Vertical Profile Heavy Metal Cd Occurrence and Its Influencing Factors].

Aiming at the problem of heavy metal Cd pollution in mining wasteland under the high background value and superposition area of the historical mining source, a total of 30 samples were collected from the reclaimed soil of a historical sulfur mine in Southwest China. The total contents of Cadmium (Cd), Chromium (Cr), Nickel (Ni), Arsenic (As), and Mercury (Hg) in soil samples were analyzed. Scanning electron microscopy-electron diffraction spectroscopy (SEM-EDS) and BCR method for continuous extraction of heavy metals were used to analyze the occurrence of Cd under different soil thicknesses. The effectiveness of heavy metal Cd was evaluated by the risk assessment coding method (RAC), and the ratio of secondary phase and primary phase (RSP) was obtained. In addition, the changes in Cd morphology under different physicochemical properties were discussed. The results show that the concentration factor of Cd in the five heavy metals is the highest over 4. Through the morphological characteristics, it can be found that there are mainly subangular and angular particles in the samples. The resulting energy spectrum characteristics at different depths were similar, and all sampled contained Cd, Fe, S, and As. Isomorphs of Cd element were observed. According to the potential risk assessment of Cd, the RAC results show that the risk is medium or below, while the RSP results may lead to serious pollution except for the bottom layer. The total amount of heavy metals is the most important factor affecting the distribution of Cd forms, followed by pH, organic matter, and CEC. The results of this study can provide scientific basis for further understanding the activity, migration rule, biological toxicity, and occurrence form of Cd in profile soil.