DETERMINATION OF DDT AND ITS METABOLITES IN SEDIMENTS AND SOILS FROM COOTES PARADISE AND VICINITY, HAMILTON, ON, CANADA

Abstract

Understanding the persistence of historical chemicals in the environment is a key component in determining the impact they have on the environment and assessing the need for remediation. The detection of the insecticide DDT in frogs in Cootes Paradise highlighted a current gap in knowledge regarding the presence of DDT and its metabolites within the Royal Botanical Gardens. DDT presence poses a concern for the birds of prey conservation efforts, the Great Lakes Water Quality Agreement, and the Hamilton Harbour Remedial Action Plan. This research aimed to develop a reliable extraction method which could be used to assess the presence of DDT and its metabolites within the soils and sediments of the Cootes Paradise region. The results of this project provide evidence that DDx residues are persisting in the sediments of all sampled regions within the Royal Botanical Gardens with concentrations in many locations exceeding the ISQG limits, PEL’s, and other regions in southern Ontario, including Point Pelee National Park. Contrary to expectations, sediment cores did not show a zone of elevated concentrations that could be attributed to the timing of the peak use of DDT, suggesting that DDx presence in the sampled cores was complicated by contaminant redistribution and/or transport. However, a correlation with location was observed, with elevated ∑DDT concentrations in Presidents Pond which decreased as the sample location moved towards Hamilton Harbour, potentially reflecting the increased application of DDT to stagnant, shallow bodies of water. Despite this decrease in concentration, proportions of DDT relative to ∑DDT were elevated in Cootes Paradise and Carrolls Bay, indicating a lack of DDT degradation which was also supported with calculated half lives averaging 59 years (range 10-211 years) which exceeds the previously reported 35 year maximum. Notably, the marshiest locations contained the highest ∑DDT concentrations, potentially indicating a correlation between organic matter and the binding of ∑DDT. Although DDx concentrations in soils surrounding Presidents Pond remained below CCME guidelines they exceed the ISQG limits and remain a potential source of DDx to Presidents Pond.