润色这一段话：土壤重金属超标主要是，伴随科技与工业的不断进步，越来越多的重金属被排放在环境中，在土壤中不断地累积，且不易被微生物所降解，从而使土壤中的重金属自然本底含量不断地升高。土壤中的重金属有可能富集在农作物中，通过食物链进入到人体，在人体中不断地累积，超过限值时，对人体造成损伤

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Soil heavy metal pollution is mainly caused by the continuous progress of technology and industry, which leads to the increasing discharge of heavy metals into the environment. These heavy metals accumulate in the soil and are not easily degraded by microorganisms, resulting in a continuous increase in the natural background content of heavy metals in the soil. Heavy metals in the soil can potentially accumulate in crops, enter the human body through the food chain, and accumulate over time, causing damage when exceeding safe limits.