DDT, its Metabolites, and PAHs in Soils and Sediments from Cootes Paradise

Abstract

Cootes Paradise, located in Hamilton, Ontario, Canada is a 450-acre wetland marsh and acts as an important habitat for local species of plants, fish, reptiles, birds, and mammals. Recent detection of the legacy insecticide dichlorodiphenyltrichloroethane (DDT) within the tissue of frogs from Cootes Paradise highlighted a potential threat to ecological health and sparked new research into their habitat. Alongside these legacy contaminants, the City of Hamilton is a large metropolitan area with a storied industrial history, leading to a reputation of poor air quality and sediment contaminated with polycyclic aromatic hydrocarbons (PAHs). This research aimed to further expand the body of knowledge on contamination of DDT and its metabolites DDD and DDE within the watershed of Cootes Paradise, as well as begin to assess the extent of PAH contamination by analyzing the presence of the US Environmental Protection Agency’s (EPA) 16 Priority Pollutant PAHs. Results of this study further demonstrate that DDT, DDD, and DDE persist in the topsoil of areas adjacent to the main waterbody of Cootes Paradise. Sampling areas were chosen using ArcGIS Pro, based on the slope of the area as well as the proximity to the water of Cootes Paradise. 12 topsoil samples consisting of 0 to 10 centimeter and 10-to-20-centimeter soil intervals, and two sediment cores were sampled, and extracted and analyzed following a modified EPA organochlorine method. DDD and DDE were primarily observed in samples with high organic carbon content, indicating that degradation is likely associated with carbon content. Contamination of DDx also was the highest along the Southern shores, with a decrease in total DDx concentration and metabolite presence as you move North through Cootes Paradise. PAH contamination was consistent throughout marsh soil and sediment samples with comparable proportions of the 16 analyzed PAHs throughout sampling areas. This suggests one common source of PAH contamination acting as an input to Cootes Paradise. Diagnostic ratio data are indicative of sources such as industrial emissions; however, it is likely that mixing of vehicular emissions also occurs before PAHs are ultimately deposited to the marsh.