Vegetation restoration has been recognized as an effective ecological measure to mitigate soil heavy metal contamination in open-pit mining areas. However, little is known about the processes of accumulation and translocation of heavy metals in naturally restored soil-plant systems in these areas. In this study, soil and plant samples were collected from three natural restoration sites of different post-mining ages (2, 7, and 15 years) to investigate the concentration, accumulation, and translocation of heavy metals in plant tissues (roots, stems, and leaves) of two different plant life forms (trees and shrubs). The results showed that heavy metals occurred at different concentrations in different tissues; and that site age significantly affected the concentration of metals, with higher concentration in older sites. Similarly, the accumulation of metals from soil to roots and the translocation from roots to stems were greater in older sites. We combined redundancy analysis, correlation analysis and multiple regression analysis to determine the effect of environmental factors on accumulation and translocation. Results showed that plant life form took the largest weight for accumulation of Pb, Ni, Cd, and Cr, and for translocation of Ni, Cu, and Zn. Site age made the highest contribution to accumulation of As, and to translocation of Hg and Cd. The accumulation of Hg and translocation of Pb, As, and Cr were most affected by total phosphorus. Soil pH was the major contributor to accumulation of Cu and Zn. These findings could provide some reference for post-mining soil remediation, particularly for gold mines. K E Y W O R D S heavy metals, plant life form, plant tissues, post-mining sites, site age 1 | INTRODUCTION Mining activities have been recognized as the major driver associated with soil degradation (Acosta et al., 2011; Food and Agriculture Organization, 2015). In particular, heavy metal contamination of soils (e.g., Pb, Hg, Cd), which is harmful to environmental and human health, has been identified as one of the primary threats posed by mining activities (Li, Ma, Kuijp, Yuan, & Huang, 2014). It is estimated that the area of land contaminated by heavy metals resulting from mining activities has reached 1.5 million ha in China, and this area is increasing at a rate of 46,700 ha yr −1 (Zhuang, McBride, Xia, Li, & Li, 2009). Mining for gold is particularly bad for heavy metal contamination (such as Pb, Hg, As, Ni, Cd, Cr, Cu, and Zn), where over 99% of waste materials contain at least
Climate variation and land use changes have been widely recognized as two major factors that impact hydrological processes. However, it is difficult to distinguish their contributions to changes in streamflow. Quantifying their contributions to alteration of streamflow is especially important for the sustainable management of water resources. In this study, the changes in streamflow for the period of 1960–2008 at two stations (Dongwan and Luhun) were analyzed in the Yihe watershed in China based on hydrological data series and climate parameters. Using a non-parametric Mann–Kendall (MK) and Pettitt’s test, as well as Budyko analysis, we first examined the trends of hydroclimatic variables and the breakpoint of annual streamflow over the past 50 years. Subsequently, we evaluated the contributions of annual precipitation (P), potential evapotranspiration (PET), and land use condition (represented by w), respectively, to streamflow variation. We observed a decreasing trend for P, as well as increasing trends for PET and w. Annual streamflow showed a significant downward trend with an abrupt change occurring in 1985 during the period of 1960–2008. Accordingly, we divided the studied period into two sub-periods: period I (1960–1985) and period II (1986–2008). The sensitivity of the streamflow to the different environmental factors concerned in this study differed. Streamflow was more sensitive to P than to PET and w. The decrease in P was the greatest contributor to the decline in streamflow, which accounted for 50.01% for Dongwan and 55.36% for Luhun, followed by PET, which accounted for 24.25% for Dongwan and 24.45% for Luhun, and land use change was responsible for 25.25% for Dongwan and 20.19% for Luhun. Although land use change plays a smaller role in streamflow reduction, land use optimization and adjustment still have great significance for future water resource management, since climate variation is difficult to control; however, the pattern optimization of land use can be achieved subjectively.
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