碳酸盐岩溶蚀作用中Cd的淋溶/残余行为

Leaching/Retaining Behavior of Cd During the Corrosion of Carbonate Rock

揭示碳酸盐岩溶蚀作用中镉(Cd)的淋溶/残余行为是完整理解碳酸盐岩风化剖面形成与演化过程中Cd的地球化学的重要环节。本文对一件白云岩试样进行了淋溶实验,设计了收集淋溶残余物与淋出液的两种装置,随淋溶进程,对淋溶残余物及淋出液相关组分进行了测试。贫Cd碳酸盐岩中的Cd(0.12 mg/kg)在酸不溶相富集(0.98 mg/kg),且样品中酸不溶物质量分数仅为2.48%。由于酸不溶物质量分数极低,酸溶相中Cd占全岩中Cd的质量比仍具有绝对优势。碳酸盐岩溶蚀过程中,在排水条件良好的条件下,酸溶相的Cd随碳酸盐溶解而淋失,酸不溶相的Cd随酸不溶物在淋溶残余物中的集聚而富集。碳酸盐岩溶蚀形成残积土的过程就是基岩中大量Cd绝对淋失与少量Cd显著相对残余富集的过程。

To reveal the leaching/retaining behavior of cadmium(Cd)in the process of the corrosion of carbonate rock is an important link for fully understanding Cd geochemistry during the formation and evolution of weathering profile developed on carbonate rock.In this study,a dolostone sample was leached,and two kinds of leaching experimental devices were designed to collect leaching residues and leachate,respectively.With the leaching process,relevant components of leaching residues and leachate were measured.Cd(0.12 mg/kg)in carbonate rock poor in Cd is enriched in acid-insoluble phases(0.98 mg/kg),and the mass percentage of acid-insoluble matter in the sample is only 2.48%.However,due to extremely low mass percentage of acid-insoluble phases,Cd in acid-soluble phase(i.e.,carbonate)still has an absolute advantage in mass percentage of Cd in the whole rock.During the corrosion of carbonate rock,under good drainage condition,the Cd of acid-soluble phase is leached with the dissolution of carbonates,and the Cd of acid-insoluble phases is enriched with the accumulation of acid-insoluble matter in the leached residues.The process to form relict soil by the corrosion of carbonate rock is actually the process of absolute leaching of a large amount of Cd and significant relative residual enrichment of a small amount of Cd in bedrock.