The Opencast Mine Dust Characteristics In Arid Land And Its Impact On The Surrounding Plants

The opencast mine of East Junggar Basin in Xinjiang is the largest self-contained coalfield in China,and the ecological environment of the opencast is very fragile because of its arid climate and poor soil.In this paper,opencast coal mine of Shenhua（M1）,Red Sand Springs coal mine（M2）,Dacheng coal mine（M3）were selected as the main research objects,the pollution of dust produced in coal yards and dumps and paved road（R1）and unpaved road（R2）in coal field were analyzed to determine the dust mount by empirical formula.The diffusion rules of dust in coal field and road has been simulated with Gaussian plume diffusion model,and PM_2.5、PM₁₀ were used to verify the dust diffusion rules,meanwhile,PM_2.5 、 PM₁₀ and few meteorological elements data were collected at 52 points in study area,to excogitate the spatial distribution characteristics and time evolution rule of dust and its influence factors.In addition,controlled experiment of coal ash for plants surrounding coal field were used to explore the current environmental pollution by open pit mining,therefore,the variation of net photosynthetic rate（Pn,μmolCO2×m-2×s-1）,stomatal conductance（Gs,molH2O×m-2×s-1）,intercellular CO2 concentrations（Ci,μmolCO2×m-2×s-1）and transpiration rate（Tr,mmolH2O×m-2×s-1）of contaminated plants were measured by photosynthesis meter.The results showed that:Amount of raised dust from coal yard is higher than that in dump,and the wind speed is an important factor affecting the dust in addition to the water content and area.The dust on the paved roads and unpaved roads is 14.02 kg·km^-1·car-1 and 42.35 kg·km^-1·car-1 respectively.The high material volume is a direct factor leading to high road dusting,and road conditions and vehicle driving conditions contribute to the accurate estimation of road dust.The turbulence has an important influence on the dust diffusion.In terms of the Gaussian diffusion model,the effective altitude of the pollution source is the root cause of the inconsistency between the dump field and the coal yard in the diffusion law.There are different diffusion law of dust between paved road and unpaved road,wind speed,road and wind angle is the result of this difference.High concentrations of airborne particles in the study area concentrated in the mining area and around the road.While the desert area in the middle of the study area has a low concentration of particulate matter.The exploitation of opencast coal mine has a positive effect on the increase of air particles.There are different degrees of reduction in Ulmus pumila and Haloxylon ammodendron in net photosynthetic rate and transpiration rate because of the influence of coal dust,under the same circumstances,the intercellular CO2 concentrations increased and the stomatal conductance did not change significantly.Under the ash treatment,the photosynthetic decline of the both plants was not the stomatal conductance factor,while through the experiment we found that the Haloxylon ammodendron had more High tolerance and ability to survive than Ulmus pumila.Long-term effective monitoring and accurate controlled experiment is an effective method to study the dust,diffusion and influence of diffusion in opencast coal mining area and its influence on surrounding vegetation.