Temporal and spatial variation characteristics of coal dust pollution in the Shengli coal mine area

The coal dust produced by surface coal mining has a serious impact on the atmosphere, vegetation, soil and residential environment in the coal mining area and its surrounding area, but the related research on the coverage of coal dust pollution, the quantification of pollution area and the trend of long-term series lags behind. In this study, the concepts of the maximum influence area and the continuous influence area were put forward. Based on the Google Earth Engine platform and the Landsat TM/ETM⁺/OLI images during 2006—2021, the ECDI (Enhanced Coal Dust Index) and the pollution coverage of coal dust were inversed. By using the linear regression and superposition analysis methods, the time series variation and spatial difference characteristics of coal dust pollution in the Shengli coal mining area were revealed. The results show that: ① the inter-annual variation of coal dust pollution can be categorized into three phases: a severe period (2006—2009), an improvement period (2010—2013), and a stable period (2014—2021). These phases correspond with the coal mine lifecycle, showing an initial increase followed by a decreasing trend. ② From 2019 to 2021, the coal dust pollution coverage was generally higher in spring and summer. Seasonal spatial variations were more pronounced in the relatively unpolluted area, lightly polluted area and moderately polluted area. ③ The overall accuracy of identifying the influence area of coal dust was 92.67% (kappa coefficient = 0.85). As coal production increased, both the perennial continuous influence area and the maximum influence area decreased, with the reductions of 43% and 80%, respectively. The spatial distribution of the annual continuous influence area remained relatively stable, while the maximum influence area decreased. ④ From 2006 to 2021, the relatively unpolluted area increased by 191.69 km², accounting for 62.70% of the original area. The seriously polluted area decreased by 4.59 km², representing 19.74% of the original area. The coal dust pollution area with a downward trend accounted for 52.11% of the coal mining area, while 4.07% showed an upward trend. As of 2021, the relatively unpolluted area and lightly polluted area accounted for 91.91% of total mining area (about 601.13 km²).