| A large-scale heavy metal pollution along the Xiangjiang drainage basin based on the multi-purpose regional geochemical survey's results in Human Province.Simultaneously,it detected that the abnormal soils regions containing the element of Cd and Pd corresponded to the distribution of mainly large mines.The sources and occurrence state of Cd in soils are complex because various mineral in this mine,it's necessary to confirm the specific sources so that can offer the basic data for later mining activity and pollution control.This thesis studied the Cd's geochemical characteristic in the Shizhuyuan mine and its surrounding soils.After analyzing the Cd's speciation in surface soils at the representative spots,combining mineralogy(XRD,SEM)with geochemistry methods was applied to find out the authentic source of Cd in surface soils in that area.The processes are including analyzing the rocks major-trace elements,identifying the minerals under the microscope,authenticating the XRD spectral line and implementing the experiment of combination Electron Probe Microanalysis analysis in-situ in the representative mineral samples with the MLA testing to find out Cd exists in which kinds of the rocks or minerals.The result illustrates Cd-Contamination soil in the Shizhuyuan mine and its surrounding region is extremely serious.Contrast with the value(0.3mg/kg)in the second-level soils criterion defined in Soil Environmental Quality Standards(GB15618-1995),the mean of Cd-Content(2.839mg/kg)is more than 9 times than the criterion.Moreover,the rate of Cd-Contamination surface soils in the whole study area accounts for 85.45%.The geochemical map reveals that the high value abnormally region of containing high Cd element is overlap with the region involving many mining activities.Through analyzing the change of Cd content in the soils profile graph ranging from 0cm to 20 cm,it states a exponentially decreasing tendency from down to up that influenced by human activities.The result of analyzing the speciation of soils discovered when the surface soils is in the extractive state are about reaching to 80%,has the positive correlation with the gross.The ratio of the most active and strongest state in weak acid is higher than other states and has little correlation with p H and Corg.The active state of soils not exist any rule with the change of spatial distance.Based on the geological background in the local area,the types of collected mineral include the Tungsten-polymetallic ore,Copper and Tin ore and Lead-zinc mine.The wall rock includes the granite,the lean ore skarn,the marble and the limestone.The mean Cdcontent in limestone,granite,polymetallic ore,copper and tin ore and lead-zinc mine are 0.48,1.17,3.07,43.09 and 808.60mg/kg,respectively,indicating the type of high Cd-content in rock and ore is the lead-zinc ore.Using the Electron Probe Microanalysis analysis in-situ in the representative minerals can realize the element of Cd mainly in the way of isomorphism exists in galena and sphalerite and the proportion in sphalerite is larger than in galena.According to the content of sphalerite and galena in two different the lead-zinc deposits can be tested by MLA,ore storage data supplied by the Shizhuyuan Company and Electron Probe Microanalysis,it can quantitatively calculate the mass of Cd in the two lead-zinc deposits with sample controlling is 2147.04 tons.Due to Shizhuyuan large-scale mining Pb-Zn mine was in the era of technology and facilities were faulty,ore and slag which smelt not completely stack outdoors would let a large number of Cd leached to the surrounding environment. |
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