Vegetation mantle change in the open pit mining area of Sin Quyen Copper Mine in Vietnam by satellite imagery data

Abstract

The article presents the estimation results on the change in vegetation mantle in the region of Sin Quyen Mine (Bat Xat District, Lao Cai Province, Northern Vietnam) in the area of 19012 hectares. The normalized difference vegetation index (NDVI) and the vegetation mantle density change were calculated using satellite images Landsat 5 TM and Landsat 8 obtained between 1990 and 2020. In the period of copper mining for 30 years in the test area, the plant ecosystem has suffered the essential changes in the structure. From the remote sensing data and analytical results in 2020, the plant community is structured as follows. In the phase of high-rate mining (2000–2020), the sites with NDVI in the range of 0.4–0.6 prevailed (60.74%). The area of sites having NIDVI > 0.6 reduced by 3330 times—to 0.2%. The area of sites with NDVI in the range of 0.2–0.4 grew to 33.78%. The areas of sites with NDVI less the 0 and from 0 to 0.2 made 1.42 and 4.04%, respectively. Such structural changes are explained by drilling-and-blasting and by operation of drill rigs, shovels, dump trucks and dozers. The dusting objects are pit walls, working and nonworking sites, and overburden dumps. At the same time, an increasing trend is revealed in the areas of sites with low NDVI (by 1.5–6 times). The analytical estimation produced an inverse dependence of decrease in the area of sites with dense vegetation cover with increasing areas of mining and dumping. This dependence is explained by the progressive degradation of ecological situation in the region of open pit mining of the deposit composed of sulfide-bearing rocks. The studies were carried out in the framework of international cooperation in the sphere of wider application of remote sensing.