Occurrence Characteristics And Pollution Assessment Of Heavy Metals On The Surface Of Representative Iron Tailings Ponds In Eastern Hebei Province

The Jidong region,centered on Tangshan,is one of the main deposit areas of sedimentary metamorphic iron ore(Anshan-type iron ore)in China,and the mining process of iron ore has caused corresponding mining environmental problems,especially the heavy metal pollution caused by mining.Therefore,the study of heavy metal distribution and pollution of iron ore tailings in the Jidong region is of great environmental significance and theoretical value for regional pollution prevention and controlIn this study,26 sampling sites,including vertical profile samples and surface samples,were designed to study the tailing ponds in Sijiaying Yanshan tailing pond,Sijiaying No.2tailing pond,Qian’an,Qianxi and Zunhua,and systematic geochemical analysis tests and BCR heavy metal determination were carried out on the samples using ICP-MS,X-ray fluorescence spectrometer,mineral phase microscope and other instrumentation to focus on the heavy metal content and fugacity patterns in the tailing ponds.The content of heavy metal elements in the tailings pond and their distribution patterns were analyzed.Based on the comprehensive analysis of the content,morphological characteristics and distribution changes of heavy metal elements,the heavy metal pollution characteristics of the iron tailings were analyzed using the single-factor pollution index method and the Nemero comprehensive pollution index method,and the potential ecological risk of the iron tailings pond was evaluated using the potential ecological risk index method and the RAC ecological code method.The results showed that:(1)The contents of Cr,Cu and Cd elements in Sijiaying Yanshan tailings pond and Sijiaying No.2 tailings pond exceeded the background values in Hebei Province in some points;the contents of Cu elements in Qian’an and Zunhua tailings ponds and Cu and Pb elements in Qianxi tailings pond also exceeded the background values.In terms of heavy metal morphology,all tailings ponds are dominated by Fe-Mn oxide-bound and residue states,and the extractable state accounts for a larger proportion of the total morphology and has a stronger migration capacity.(2)In the vertical direction,the heavy metal content in both Sijiaying Yanshan and No.2tailings ponds showed a continuous downward migration trend;in the plane,from the edge to the center of the tailings pond,the total amount of heavy metals in Yanshan tailings pond showed a trend of first increasing and then decreasing,and No.2 tailings pond showed a trend of gradually decreasing total amount of heavy metals.(3)The heavy metal pollution characteristics show that there is some pollution of elements Cd,Cr and Cu in Sijiaying Yanshan tailings pond;there is some pollution of elements Cu,Pb and Cr in Sijiaying No.2 tailings pond,among which Cu pollution is more serious;there is some pollution of elements Cu in Qian’an and Zunhua tailings ponds and elements Pb and Cu in Qianxi tailings pond.The risk evaluation of heavy metals showed that the potential ecological risk factor RI of each tailings pond was mild hazard level;among the measured samples,the evaluation results of RAC ecological coding method were all moderate risk.There are 15 figures,28 tables,and 101 references in this thesis.