Cadmium Contamination, Bioavailability, Uptake Mechanism and Remediation Strategies in Soil-Plant-Environment System: a Critical Review

Abstract

Background: Cadmium contamination is becoming an important issue globally due to its high toxicity and carcinogenicity, leading to detrimental effects on both environmental and human health. This review paper discusses the different sources of cadmium, its toxic effects on the environment and human health, and the influence of different soil factors in changing the speciation and bioavailability of cadmium in soil. This paper also covers research on different remediation strategies currently available for reducing cadmium bioavailability. Methods: Previous research and critical comparison of cadmium extent, toxicity, effects and management were studied Results: The carcinogenic nature of Cadmium is of significant human health concern. Cadmium is found in both free and complexed forms, where its availability depends on its speciation in soil. In soil, oxidizing conditions and high pH decrease cadmium bioavailability and speciation. Here, organic matter can also act as both a sink and source of cadmium and microbes perform many mobilization processes including protonation, chelation, and chemical transformation whereas, sorption or precipitation decreases cadmium availability. Continuous exposure to cadmium can result in browning, decomposing and mucilaginous roots, shoot reduction and apical growth of root, chlorosis, and rolling of leaves. Toxicity may inhibit lateral root formation or can result in rigid, twisted, and browning of the main root. Toxicity also affects photosynthesis and the availability of mineral nutrients. In this paper, the remediation techniques of soil polluted by Cd, including biological, chemical and physical remediation are reviewed. The methods of remediation, developing trends, drawbacks, and strengths were also reviewed to provide a reference for the research in this field to date. Conclusion: Although cadmium toxicity is of great concern, many remediation techniques can be successfully used to mitigate its adverse effects. Phytoremediation, hyperaccumulation, bioremediation, and the application of different amendments to the soil have all been successful in alleviating cadmium bioavailability. Amongst all available techniques, in-situ immobilization with inorganic, organic or clay amendments is an environmentally friendly and cost-effective strategy to remediate cadmium contaminated soils and achieve sustainable agriculture production.