Abstract
The study investigated the interrelationships among chlorpyrifos (CPF) concentrations in water resources, CPF application and rainfall during peak pesticide application period with usual rainfall pattern. Water samples were collected at three day intervals from groundwater and surface water resources at Marassana, a commercial vegetable cultivation area in the Kandy District, Sri Lanka, during a 5-month period. CPF application and rainfall data were also collected simultaneously. High performance liquid chromatography analyses revealed that the average CPF concentration in groundwater and surface water samples were 0.63 and 0.52 μg/L, respectively. The respective corresponding maximum values were 7.1 and 3.7 μg/L. Multiple linear regression analysis of the data established that 1 L of CPF 40 % (= 400 g/L concentration) applied in the catchments increased the CPF concentration in the groundwater and surface water by 0.65 μg/L and 0.120 μg/L, respectively; 1 mm of cumulative rainfall received increased the CPF concentration of surface water by 0.021 μg/L but did not affect the groundwater concentration significantly. Uncertainties in the model parameters analysed using Monte Carlo stochastic simulation established that there was an 88 % probability for the CPF concentration to remain positive in the surface water. Doi: http://dx.doi.org/10.4038/jnsfsr.v40i4.5047 J.Natn.Sci.Foundation Sri Lanka 2012 40 (4): 333-344
Highlights
Chlorpyrifos (CPF) is the common name used for O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl)phosphorothioate, which is a broad-spectrum chlorinated organophosphate insecticide
Water samples were collected at three day intervals from groundwater and surface water resources at Marassana, a commercial vegetable cultivation area in the Kandy District, Sri Lanka, during a 5-month period
High performance liquid chromatography analyses revealed that the average CPF concentration in groundwater and surface water samples were 0.63 and 0.52 μg/L, respectively
Summary
Chlorpyrifos (CPF) is the common name used for O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl)phosphorothioate, which is a broad-spectrum chlorinated organophosphate insecticide. The objective of this study was to estimate the CPF concentrations in surface water and groundwater in a commercial vegetable cultivation area in the central hills of Sri Lanka, and to determine the factors affecting the contamination. The maximum permissible level for CPF in fresh water is 0.041 μg/L according to the USEPA (2009) water quality criteria. The 2008 amendment (NER, 2008) to the Sri Lankan National Environmental Regulations (NER) has increased the tolerance limit of total pesticides for the discharge of effluent into inland surface waters from “undetectable” (NER, 1990) to a maximum of 5 μg/L. The regulation stipulates that such discharged effluent should be diluted by at least eight volumes of clean receiving water, which amounts to 0.55 μg/L, the maximum permissible tolerance limit for pesticides in surface water. The permissible levels of CPF for ground water resources are not yet defined
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