文献阅读问题答案.pdf

文献阅读问题 Introduction 1. How do heavy metals entry the soils? Answer: Entry of soil-borne metal(loid)s into the food chain depends on the amount and source of metal(loid)s input, the properties of the soil, the rate and magnitude of uptakeby plants, and the extent of absorption by animals. 2. Can you give a definition to heavy metal and give us the examples? Answer: The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic, highly toxic or poisonous at low concentrations. Examples of heavy metals include mercury(Hg), cadmium(Cd),arsenic(As), chromium(Cr), thallium(Ti), and lead(Pb) . Historically, heavy metal(loid)s toxicity to human health received attention primarily as a result of series of widespread poisoning. 3. Why human kind pays attention to heavy metal(loid)s toxicity? Answer: Historically, heavy metal(loid)s toxicity to human health received attention primarily as a result of series of widespread poisoning. 4. Can you describe characteristics of heavy metal(loid)s in soil? Answer: Unlike organic contaminants, metal(loid)s do not undergo microbial or chemical degradation, and the total concentration of these metal(loid)s persist for a long time after their introduction in soils . 5. Can you tell us the difference between phytoextraction and phytostabilization? Answer: Phytoextraction process is used to remove metal(loid)s in soil; phytostabilization is used to immobilize metal(loid)s in soil. Sources of heavy metal(loid)s 1. Where does heavy metal in the soil come from? Answer: Heavy metal(loid)s reach the soil environment through both pedogenic and anthropogenic processes. Dyn