Element geochemical characteristics of weathering crust profiles of the Wenchuan section in the upper arid valley of the Minjiang River
This study conducted geochemical tests and analyses for vertical rock-soil profiles with different bedrock types in the Wen-chuan section in the upper arid valley of the Minjiang River.Based on the above,this study explored the vertical distributions of ele-ments in these weathering crust profiles to investigate the influence of bedrocks on the contents of chemical elements in soils.From a geological perspective,this study provided proposals for planting in agricultural production and eco-environmental restoration for the study area.The results of this study are as follows:(1)From top to bottom,weathering crust profiles can be divided into four layers:the humus layer(A),the illuvial layer(B),the soil parent material layer(C),and the bedrock layer(R).The humus layers exhib-it higher average values of Al,Ca,K,Mg,Fe,Se,Zn,Cu,Cd,and Pb and lower average values of Si,Na,Mn,Cr,As,Cd,and Hg,compared to corresponding national average values in soils;(2)In weathering crust profiles with different bedrock types,except for elements with higher contents in both bedrocks and corresponding soil layers,the same elements manifest similar contents in other soil layers;(3)The chemical weathering intensity increased from the bedrock to the humus layers,with soil weathering degrees gener-ally higher than bedrock weathering degrees;(4)In addition to characteristics inherited from soil parent materials,elements in weathe-ring crust profiles show content differentiation,characterized by enriched Al,K,and Se in humus layers,enriched Na,Fe,Si,Pb,Cu,Zn,Mn,As,Cd,Cr,and Hg in illuvial layers,and enriched Mg and Ca in soil parent material layers.
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