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Lime is one of the commonly used amendments for acidic soils. The reasonable application of lime can effectively improve the current status of acid tailings and reduce harm to the environment. In this study, we analyzed the pH alternation of acid tin tailing as a function of lime dose based on three methods-single titration method, K-bicarbonate titration method, and buffer curve method-to predict the accurate lime requirement (LR) in acid tin tailing treatments. Of these prediction methods, the buffer curve method was best suited for the prediction of lime dose, and the prediction values agreed with the experimental data by factors of 1.0‒1.4. Thus, we determined that the buffer curve method was more suitable for predicting the lime requirement of acid tailings. This study of acid tailings lime requirement provides scientific research for the subsequent modification of tailings., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

To investigate the dominant plants in ecological restoration of tin mining areas, field investigations were conducted in a tin tailings area in Lailishan, Yunnan Provence, and 15 dominant plants and corresponding rhizosphere soils were collected. The plant root mycorrhizal infection rate; the copper (Cu), cadmium (Cd), arsenic (As), nickel (Ni), lead (Pb), and tin (Sn) contents; and the chemical properties of the rhizosphere tailings were determined. The transfer and enrichment coefficients of six heavy metals were calculated for each of the 15 plants to comprehensively evaluate the application potential of native plants. The rhizophere tailings had an average pH value of 3.13, which was acidic. The organic matter, total nitrogen, total phosphorus, total potassium, alkaline hydrolyzed nitrogen, and available phosphorus content of the soils was 6.07 g ·kg -1 , 5.74 g ·kg -1 , 0.62 g ·kg -1 , 8.66 g ·kg -1 , 30.84 mg ·kg -1 , and 2.08 mg ·kg -1 respectively, indicating relatively nutrient-poor soil. The average Cu, Cd, Ni, Pb, As, and Sn contents of the soils were 347.40, 1.02, 1.34, 168.47, 25.81, and 2299.02 mg ·kg -1 , respectively. Among the heavy metals, the Cd content reached a third-level pollution warning value. The soil also contained a large amount of Cu and Pb which exhibited a different spatial distribution. This area appears to have a high risk of Cu, Pb, and Cd pollution. In addition, the roots of Olea europaea L. and Eurya japonica Thunb. had a high rate of mycorrhizal infection. Alnus cremastogyne Burk., Bambusa multiplex (Lour.) Raeusch. ex Schult. 'Alphonse-Kar' R. A. Young, Juncus effusus L., and Cyperus rotundus L. var . had a strong ability to absorb and transport heavy metals. The other plants were also adapted to the growth environment of the tin tailings, with the potential to restore the mining area.

Ecological reclamation is the major method for the revegetation of acid mine wasteland worldwide. In this study the pH, fertility characteristics, and heavy metal content of soils from Laili Mountain mine wasteland were analyzed. The research also studied the morphological characteristics and the heavy metal in Juncus ochraceus Buchen as well as its resistance to acid, adaptability to soil fertility in abandoned land, and tolerance to heavy metal pollution (e.g., Zn and Cu) to determine its remediation potential as a pioneer plant for acid mine wasteland. Results showed that the pH of soils in the study area were acidic, ranging from 3.46 to 4.01.The contents of organic matter, total potassium, total phosphorus, and available phosphorus was poor, being 10.28-25.75 g·kg -1 , 8.84-9.32 g·kg -1 , 0.56-0.63 g·kg -1 , and 1.82-5.72 mg·kg -1 respectively.The contents of Zn, Cu, and Fe in the soil ranged between 54.93 and 114.49 mg·kg -1 , 92.53 and 127.59 mg·kg -1 , and 47133.60 and 112259.63 mg·kg -1 , whereby the Cu content was 1.85-2.55 times higher than the risk screening value. The height of Juncus ochraceus Buchen in the study area ranged from 43.77 cm to 55.42 cm, which was shorter than the average plant height of the control group (51.38-57.66 cm); however, this was not a significant difference, thus indicating that this plant was resistant to acidic soil and heavy metal pollution.Further analysis showed that Juncus ochraceus Buchen had accumulating capacity for both Cu and Zn, and transferring capacity for Zn as well. Thus, it had potential in heavy metal accumulation and absorption.Plant height was significantly related to the available phosphorus content in the rhizosphere soil. In the future, soil fertility could be improved by supplementing fertilizers containing available phosphorus when Juncus ochraceus Buchen is planted on the land of abandoned mines as a pioneer plant. Comprehensive analysis revealed that Juncus ochraceus Buchen had great potential as a pioneer plant to remediate acid mine wasteland.