Effects Of Coal Exploitation On Soil And Vegetation In Shenmu Mining Area

In recent years, large-scale exploitation of coal resources in coal mine and theunreasonable utilization has provided the country important strategic resource; However, italso caused a series of environmental pollutions and geological disasters, ecological damagewhich threatened the safety of human lifeand the development of the national economy.Especially national energy important region in Shenmu, Northern Shaanxi district.Thecontradictions between the large-scale, high-speed development of coal resources and thelower environmental capacity was increasingly prominent, and with the speeding up of thedevelopmentprocesses, the local environment have further deteriorated, which seriouslythreated the sustainable socio-economic developments. In this study, we selected threerepresentative sampling plots and one control area in Shenmu coal mining areaused themethod of field investigation and laboratory analysis. We measured the indicators of soil andvegetation at the mining areas, also the effect of coal exploitation on ecological environmentwas analyzed. The main conclusions were as follows:（1） Study on soil physical-chemical properties in three coal mining areas showed that thesoil bulk density was smaller and total porosity was bigger than the control, which indicatedthat coal exploitation caused the soil-loose. Soil silt in sampling area was highest, followed bysand and clay. The physical clays in coal mining areas A, B, C were less than in the controlarea. As for soil profile, the physical clay in surface layer was lower than other layers, whichmay be related to the less vegetation coverage rate and the stronger wind and rain erosionexacerbated by movement and loss of soil physical clay. The content of soil organic matter,total nitrogen, total phosphorus in the three coal mine was low; total potassium with mediumcontent; available phosphateand available potassium content were high.Soil nutrients inprofile generally decreased with increasing soil depth.（2） By analyzing the characteristics of the volume fractal dimension of soil particles inthree coal mines, we can draw the conclusion that soil particle size distributions could besignificantly fitted by the volume fractal model （p<0.01）, the coefficient of determination ofthe fitting equation ranged from0.867to0.943. The volume fractal dimension of soil particlesD value ranged from2.484to2.658with the mean of2.576, which had the significantlypositive correlation with the volume percentage of clay and siltand the significantly negative correlation with the volume percentage of sand. Compared to soil silt and sand, the effect ofclay on D was more remarkable, which indicated soil texture could be a comprehensivereflection of soil particle composition, and D was closely related with soil texture. The Dvalues of surface soil in sampling area were C> B> CK> A.（3） The soil heavy metal （Cu, Cd, Cr, Mn, and Ni） content around three collieries in theShenfu coal mine area was measured. The results indicated that long-term development andtransportation of coal resources had resulted in heavy metal contamination around thecollieries. The soil Cd and Ni content was greater than the background values measured inother parts of Shaanxi Province, indicating that the soil around the collieries wascontaminated by Cd and Ni. In contrast, the soil Cu, Cr, and Mn content was lower than thebackground value. The soil heavy metal content in the contaminated areas was higher than thecontrol area but the magnitude of the change varied with the heavy metal species. Soil Cu, Cr,and Mn contents were lower than the background value, but they still increased as colliery ageincreased. The heavy metal pollution around the collieries was affected by the age of thecolliery, the soil texture, and the wind direction.-. The heavy metal content in soil profilegenerally decreased with increasing soil depth.（4） By survey of the vegetation communities and speciediversities in the three coal minesand the control area, there were74vegetation species found in sampling plots, belonging to32families,63genera, Leguminosae, Compositae and Gramineae were the main species,accounting for43.24%of the whole species. The herbs around coal mine areas were generallyat a high level, and shrubs and tree species were significantly lower than the herbs, thus theinfluence of the herbs on community richness was more greater and the community wasunstable as a whole.The dominant species in coal mine A was Setaria viridis, and in B, C, andCK were Stipa bungeana. The Margalef index in coal mine A and C, A and control area wassignificantly different （p<0.05）; the difference of Pielou index, Shannon-Winner index, andSimpson index was not significant, which indicated that the effect of coal exploitation onvegetations in this coal mine area. The similarity index of plant communities in three coalmines showed that the similarity of the coal mine C and the control area was highest, the coalmine B, A and the control area were lowest, which indicated the community stability of thecoal mine A was lowest.（5） The enrichment characteristics of Cd, Cr, Cu, Mn, and Ni in selected plants in coalmining area showed that the mean content of Cd, Cr, Cu, Mn, and Ni in plants was0.41,3.39,6.53,42.91,1.49mg·kg^-1, and the Cd, Cr, Ni content exceeded the limit of the food hygienestandard, which showed that the exploitation of coal resources has resulted in heavy metal Cd,Cr, Ni pollutionto the vegetation around the coal mine area. The enrichment capacity of the plant on heavy metals was various, and the enrichment capacity of the Cd and Cu of8vegetation species were all stronger.