Why are there heavy metals in soil?
Soil provides a good environment for plant growth, but if the soil is polluted, the pollutants will enter the human body through plants, especially crops, thereby endangering people's health. Heavy metals are a common pollutant in the soil environment. People often believe that normal soil does not contain heavy metals, and that heavy metals are all caused by pollution. However, this is not the case. Heavy metals in soil can be divided into two main sources: natural sources and human sources.
If rocks contain a large amount of heavy metals before the formation of soil, these heavy metals will remain in the soil, causing high heavy metal content in natural soil. In China's natural soil, the heavy metal content is not high, but in recent decades, heavy metal pollution caused by human activities has become increasingly serious.
There are various human activities that can lead to an increase in heavy metals in soil. For example, irrational fertilization can cause cadmium in soil to rise, because some phosphate fertilizers from certain regions contain a large amount of heavy metal cadmium; excessive use of pesticides can cause excessive arsenic in soil, because arsenic is a component of some pesticides. The most important artificial sources of heavy metals in soil are industrial activities, especially various heavy metals produced during the development and smelting of metal products, chromium produced by the leather manufacturing industry, and lead produced by the lead-acid battery industry. Heavy metals released into the environment by industrial production can eventually settle in soil through water and air, causing large-area soil heavy metal pollution.