## 3 Results and Discussion
### Impact of Revgegetation on Environmental Risks in Mining Areas  
The environmental risks of As and Sb in mining areas after revegetation were evaluated by the Modified Comprehensive Pollution Risk Assessment method (MCR) [25,39]. The _CRS_ scores of As pollution in each area before and after revegetation (Figure 4a) were US (17) > UT (15) > RS5 (11) > RS10 (7) > RT10 (6), and based on the _CRS_ assessment criteria (Table 2), the values of the _CRS_As in the unremediated US and UT areas were all higher than or equal to 15, which indicated that the unremediated US and UT had a high risk of As pollution. With the revegetation of the mine area, the values of _CRS_As decreased significantly, and the values of _CRS_As in the RS5, RS10, and RT10 areas were reduced by 6, 10, and 11 scores, respectively, compared with the US areas. Compared to the _CRS_ assessment criteria (Table 2), the As pollution problems in RS10 and RT10 have been reduced to low or no pollution levels after 10 years of revegetation treatment. The results showed that the revegetation treatment could effectively reduce the environmental risk of As contamination; with the extension of the revegetation time, the environmental risk of As contamination gradually decreased. Meanwhile, the _CRS_ scores of Sb contamination in each area (Figure 4b) were in the following order: US (19) > UT (16) > RS5 (15) > RS10 (10) > RT10 (6), which showed a similar rule with the As contamination. Both unremediated US and UT had the high risk level of Sb contamination, while the _CRS_Sb values decreased significantly with the revegetation. After 10 years of revegetation, the _CRS_Sb of the RS10 and RT10 areas were 10 and 6, respectively, which indicated that the ecological risk of the accumulation of Sb in the mining area was gradually reduced with the revegetation. This was consistent with the changes in the total amount of metal(loid)s and the transformation of chemical speciation. The results of correlation analysis (Figure 5) also demonstrated that the environmental risks of As and Sb were significantly correlated with their total content and the percentage of exchangeable fraction. In addition, under the effect of revegetation, the geochemical principles were changed, and nutrient elements such as N and P were accumulated in the rhizosphere, which effectively improved the quality of the soil [31,48]. Under the influence of plant root exudates and microbial activities, etc., the content of metal(loid)s and the percentage of bioavailable chemical forms can be effectively reduced, thus reducing environmental risks [35; 40; 49]. Compared to other environmental risk assessment methods, the results of \(I_{goo}\), \(EF\), and \(ER\) exhibited similar risk trends. However, there were some differences among the assessment methods, for example, the results of \(I_{goo}\), \(EF\), and \(ER\) showed that Sb contamination in the US reached a very high risk level, while the results of \(RAC\) showed that it was only a low contamination risk level. Previous studies have also shown that \(I_{goo}\), \(EF\), and \(ER\) values may overestimate the bioavailability and toxicity risk of As and Sb [25]. This is because the \(I_{goo}\), \(EF\), and \(ER\) values are calculated using the total content of metal(loid)s and do not consider the mobility and bioavailability of metal(loid)s, whereas the \(RAC\) calculations are assessed based on the percentage of bioavailable chemical formation of metal(loid)s in the contaminated site. Since most of As and Sb were in the residual fraction and the percentage of their exchangeable fraction was less than 10%, therefore, based on the \(RAC\) assessment criteria, they were shown as non-risk or low-risk level. The MCR method effectively integrates the total amount of metal(loid)s and their chemical formation, which  
Figure 4: The comprehensive pollution risk score (CRS) of As (**a**) and Sb (**b**). The red dashed line indicates the threshold for high pollution levels.