Heavy Metals In Gangue: Shifts And Agroecological Pollution In Farmlands

The experiments in this paper focused on the farmland around Jiahe Coal Mine, a branch ofXuzhou Mine Group to investigate the effects of the contents of Cu, Pb, Cr, Cd and Zn in gangue onthe farmland, main irrigation source and rice. Based on these investigations, analyses wereconducted on the safety of heavy metals in soil and rice, and the shifts of heavy metals in soil.Finally, countermeasures were proposed to harness heavy metal pollutions in gangue. The mainresults were as follows:1. In contrast to the heavy metal contents in soil background, the contents of Cu, Pb, Cr, Cd andZn in the farmland were detected higher. The single pollution indices of each heavy metal were allhigher than 1, and the comprehensive pollution indices were as high as 7.01. Compared with theheavy metal content standards of the first grade soil, the contents of Cu, Pb, Cd and Zn in thefarmland were higher, single pollution indices reaching higher than 1 and the comprehensivepollution index as high as 4.81. Compared with the heavy metal content standards of the secondgrade soil, the contents of Cu and Zn in the farmland were higher, reaching a comprehensivepollution index of 1.59. These results indicated that the soil around Jiahe Coal Mine had beenpolluted by heavy metals in gangue, and the pollution of Cd was the most serious.2. The contents of heavy metals in the main irrigation source around gangue were lower thanthe indices stipulated in National Irrigation Water Standard. No pollution effects were detected.3. In contrast to National Food Hygiene Standard, both the single and the comprehensivepollution indices of Pb in brown rice were higher than 1. The single pollution index of Cd was 0.99.Although it was lower than 1, 7 samples were detected higher than 1. And also for the high toxicityof Cd, much attention must be paid to its pollution. The pollution of Cu, Cr and Zn was not detectedin the rice. The comprehensive pollution index of the five heavy metals in brown rice were slightlyhigher than 1, so the soil around the mine was not suitable for the growth of non-polluted rice.4. The absorption, shifting and accumulation of heavy metals in rice were quite different. Theaverage accumulation rate of Cu, Pb, Cr, Cd and Zn were 0.115, 0.007, 0.009, 0.156 and 0.234,respectively. Of all the 5 heavy metals, the accumulation of Cd was the highest. Much attention mustbe paid to its pollution when planting rice in the region.5. The distribution of heavy metals around the coalmine demonstrated the followingcharacteristics. The pollution in the region within 100-200 meters around the mine was most serious.The further away from 200 meters away the gangue, the lower contents of Cu, Pb and Zn weredetected, while no decrease were detected in the contents of Cr and Cd. As for rice, the highestcontents of Cu and Zn were detected at 200 meters away from the gangue. The further away from200 meters away the gangue, the lower contents of Cu and Zn were detected.The above-mentioned results indicated that the soil around the gangue had been to some degreepolluted by the heavy metals. And the heavy metals in rice were higher than the national standards.These followed the path of the erosion of gangue, the dissolution of heavy metals in water and theabsorption by rice plants.