97 / 2023-06-15 09:38:14

Study on the dynamic impact of spontaneous combustion of shallow coal seam on soil chemical properties, Huojitu mine area, Shenmu, China

Shallow burial of spontaneous coal seams,Coal spontaneous combustion,Emitted gas,Soil chemical properties,Huojitu mine area

The heat and gases generated by spontaneously combusting shallow coal seams diffuse into overlying soil, altering soil chemistry and affecting vegetation growth. This study inverted fractional vegetation cover (FVC) from remote sensing imagery, conducted temperature-programmed experiments of coal spontaneous combustion (CSC) with soil cover, and performed soil nutrient and chemical analysis to examine FVC changes, differences in gas composition/concentration, and soil physicochemical alterations across CSC oxidation stages. The results showed FVC in Zhongji Town, with the Huojitu mine, was unstable with the northeastern mining area exhibiting significantly poorer FVC due to coal mining disturbances. The FVC was at its highest in 2019 during the study time, with 30.67% of the area having relatively high-density vegetation. CSC stages were classified as slow oxidation stage (I), critical temperature stage (II), rapid oxidation stage (III), and late oxidation stage (IV). Carbon-oxygen gases increased exponentially in stages III and IV. C₂H₄ was generated in stage III while alkane gases increased rapidly in stages III and IV. Ammonium nitrogen (NH⁴⁺-N) content changed minimally in stage I and then fluctuated upwards in stage II with competing temperature/gas effects, ultimately increasing by 74.44%. Available phosphorous (AP) decreased by 10.8 mg/kg in stages I and II, and then increased to 58.614 mg/kg from stage III. Available potassium (AK) content decreased significantly at the ends of stages I, II, and IV with a short plateau in stage III, ultimately reduced by 16.28%.