While chemically synthesized pesticides help ensure increased agricultural yields, approximately 80% of the amount applied enters the environment directly, exerting long-term, multi-dimensional impacts on the atmosphere, soil, water bodies, and the entire ecosystem.
Atmospheric Pollution and Long-Range Transport
Pesticides can enter the air as aerosols or vapors through spray droplets during application, the volatilization of residues from soil and water surfaces, or emissions from pesticide manufacturing facilities.
Such pollution can be transported across regions by air currents; for instance, persistent synthetic pesticides like HCH (hexachlorocyclohexane) have even been detected in the snowpack on Mount Everest-a location where pesticides have never been used.
The extent of volatilization is significantly influenced by the pesticide formulation and the method of application; techniques such as the use of smoke-generating agents or aerial spraying carry a much higher risk of volatilization and drift compared to the use of granules or localized (in-furrow/hole) application.
Soil Degradation and the Accumulation of Residues
In my country, approximately 6.67 million hectares of soil-6.39% of the total arable land-are affected by chemical pesticide pollution. A substantial portion of these pesticides is adsorbed by soil organic matter, directly leading to soil acidification and a decline in organic matter content.
Certain highly persistent pesticides can remain in the soil for years. For example, DDT has been detected in 98.12% of soil samples taken from farmlands in Shanghai, with many sites showing concentrations that exceed the national Grade I standard for soil environmental quality.
Pesticide residues inhibit the activity of soil microorganisms, disrupt the soil's micro-ecological balance, and diminish both the soil's natural fertility and its capacity for self-purification.
