Abstract:
Embilipitiya, located in the Right Bank of Walawa basin is under heavy agriculture and
therefore agrochemical usage is very high. Paddy and banana are the most common crops
cultivated in this area. The commonly used pesticides in Embilipitiya were identified through a
survey and they were propanil, MCPA, carbofuran, and dimethoate. These pesticides are
highly water soluble and a risk assessment for movement of these pesticides in soils is
Important for better soil and water management. Using two simple indices, Retardation factor
(RF) and Attenuation factor (AF), the leaching potential and vulnerability for ground water
contamination of these major pesticides were assessed. According to RF, carbofuran followed
by dimethoate (estimated 1.0<RF<2.0 for both pesticides) and based on AF carbofuran
(2.Sxl0'l<AF<1.0) have great risks for ground water contamination in many places in this area.
Hence the ranking of commonly used pesticides in the Walawa basin according their risk levels
can be done as carbofuran > propaniF dimethoate> MCPA’diazinon
