What are the causes and effects of pesticide residues in soil and water and fate of pesticides in the ecosystem?
Through water and soil, the pesticides enter into the food web. Some organochlorine pesticides in the soil are degraded from 6 months to 10 years ie, and they have high persistence. These pesticides alter the specific genes that produce the resisting enzymes that degrade the pesticides within the organisms.
Pesticide residues can get into the water supply or they can contaminate soil and animal feed, therefore, find their way into our food indirectly. The human food chain is also affected by the pesticide residues left in crops soil and water. The environment (air, soil and water) can be contaminated by pesticide overuse, spills, leaking storage tanks, rainwater runoff from over-treated areas, spray drift, and improper disposal of pesticides, among other ways. In severe cases, people may even have difficulties in breathing, blurred vision and convulsion. Prolonged excessive intakes of pesticide residues have been shown to cause damage to the nervous system or other organs such as liver and kidneys, as well as affect fetal development in animals. Pesticides can accumulate in bodies of water to levels that kill off zooplankton, the main source of food for young fish. Pesticides can also kill off insects on which some fish feed, causing the fish to travel farther in search of food and exposing them to greater risk from predators. Thus, due to many different human activities such as overuse of pesticides the soil will lose its fertility. Moreover, the presence of excess chemicals will increase the alkalinity or acidity of soil thus degrading the soil quality. This will in turn cause soil erosion. This soil erosion refers to soil pollution. Pesticides affect non-target microbes by interfering with vital processes such as respiration, photosynthesis and biosynthetic reactions, as well as cell growth and division and molecular composition. Soil pollution affects soil fertility; this jeopardises food security, which is essential for human survival. It also poses risks to human health both indirectly through the consumption of contaminated food and drinking water, and directly through exposure to contaminated soil.Pesticides may become airborne, get into soil, enter bodies of water, or be taken up by plants and animals. The environmental fate of pesticides depends on the physical and chemical properties of the pesticide as well as the environmental conditions. Three types of pesticide degradation are microbial, chemical, and photodegradation. Microbial degradation is the breakdown of pesticides by fungi, bacteria, and other microorganisms that use pesticides as a food source. Most microbial degradation of pesticides occurs in the soil. Pesticides can contaminate soil, water, turf, and other vegetation. In addition to killing insects or weeds, pesticides can be toxic to a host of other organisms including birds, fish, beneficial insects, and non-target plants. Movement in runoff water occurs when soluble or insoluble pesticides move from the application site across the soil surface, either dissolved or suspended in runoff waters. Pesticides dissolved or suspended in runoff water may quickly reach surface waters such as lakes, streams and rivers.The high temperatures can also make pesticides more bioavailable, increasing the chance of microbial degradation. Some microorganisms may co-metabolize pesticides, where the microbes rely on the feedstock for food and energy while breaking down an adjacent pesticide. The most common fates are listed below: Absorption is the uptake of pesticide molecules into plant tissues. This action removes the pesticide from the environment and prevents the pesticide from becoming a water contaminant. Adsorption is the physical binding of pesticide molecules to soil particles.
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