Quantitative Description Of Trace Elements' Behaviors During Weathering

The behavior of trace elements during weathering is of great significance in delineating geochemical background values,delineating mineralization anomalies and evaluating environmental geochemistry.In this paper,the behavior of elements in the process of weathering was analyzed in wang an town of laiyuan,hebei province.The method of mass balance calculation is limited by the need to determine the parent rock.The mass balance calculation method requires the determination of inactive elements and the determination of parent rock is limited.Therefore,the empirical equation method is adopted in this paper to quantitatively characterize the weathering behavior of elements.The previous empirical equation is obtained by fitting the data of 13profiles across the country,and the geochemical background values of more than 20trace elements can be calculated using only three weathering index WIG,Al₂O₃/Ti and K₂O/SiO₂.In this paper,the data of 27 samples collected in wang'an town were analyzed by regression,including 11 weathering profiles,3 soil samples,2 river sediment samples and 11 rock samples.Based on the previous empirical equations,a new empirical equation is proposed for the area of wang'an town.It is found that there is a quadratic function relationship between WIG and element content in the samples from wang'an town.The empirical equation that quantitatively characterizes the background values of trace elements in the rock weathering process in wang'an town is as follows:lg?c?=A*lg?|a*WIG²+b*WIG+c|?+B*lg?Al₂O₃/Ti?+C*lg?K₂O/SiO₂?+Dwhere c is the content of trace element in ng/g for Cd,Hg and?g/g for others,the content unit of Al₂O₃,K₂O,SiO₂ is weight%,WIG varies from ca.49.78 to 93.96,SiO₂ varies from ca.57.57 to 74.22,Al₂O₃ varies from ca.13.05 to 16.72,and CaO varies from ca.0.258 to 5.585 about the regression data.where A,B,C and D are the fitted parameters,and a,b and c are the coefficient of WIG.Ten samples from the same background area were selected from the references to verify the empirical equation,and it was found that the verification results were within the error range,indicating that the above equation had a significant effect on the geochemical background value in wang'an town area.Based on the re-fitting empirical equation,eight heavy metal elements Cd,Hg,As,Cu,Pb,Cr,Zn and Ni in wang'an town were selected As the research objects,and a method for identifying element anomalies in the application of empirical equation in environmental assessment was proposed.The calculated value of the empirical equation is compared with the measured value.If the calculated value and the measured value are within the allowable error range,the element is not abnormal.If the calculated value is obviously higher than the measured value,the element will move in.If the calculated value is obviously lower than the measured value,the element is removed.