Aquatic Pollution and Coastal Zone Managememnt (2+1)

Unit 4 : Pesticide pollution

4.4.Pathways

Aerial transport/atmospheric Input
The principal source of widespread pesticide contamination is from the agricultural use of these compounds. In fruit and vegetable growing areas where there is heavy use of pesticides,these are rapidly lost to the atmosphere and forms aerosols in the presence of water vapour, which travel long distances.
Example: 99% of HCH lost to air (India)
98% of DDT lost to air (Nigeria)

In arid areas, the dry soil with absorbed pesticides is transported in dust storms.
Dioxins and Furrous-by burning /incineration of municipal waste

River runoff
Although the total burden of pesticides carried out into the sea by rivers is small compared with aerial input, it may be locally damaging.

• Rain washing of pesticides from plants and soil into the river.
• Floods carry out very large quantities of silt into the sea from agricultural lands contaminated with pesticides.

Direct input (Effluents)
Contaminate bottom sediments

• Industrial outfalls (PCB’s)
• Sewage sludge

Fate of pesticides in the Aquatic Environment
On entry into the aquatic environment through various pathways, these non-polar, toxic, semi-volatile and fairly persistent substances may remain within the water body unchanged for a period of time, undergo degradation to simpler compounds which may be more toxic or/and more persistent than the parent compounds (e.g DDE, dioxin) or get reversibly transferred into the atmosphere by volatilization.