Use of semipermeable membrane devices to investigate the impacts of DDT (Dichlorodiphenyltrichloroethane) in the Holland Marsh environs of the Lake Simcoe watershed (Ontario, Canada)

Abstract

In 2004 the Lake Simcoe Region Conservation Authority (LSRCA) initiated a sampling program to examine historic and emerging contaminants throughout the Lake Simcoe watershed. Through the sampling program it was determined that Dichlorodiphenyltrichloroethane (DDT) concentrations in sediment were exceeding the Canadian Environmental Quality Guidelines just downstream of the Holland Marsh. The objective of this study was to investigate the presence of DDT in the waters surrounding the Holland Marsh and examine if the concentrations sampled represented a potential threat to aquatic and terrestrial biota in the Holland Marsh environs. Semipermeable membrane devices were used to determine DDT concentrations at different locations within the Holland Marsh and surrounding waters for a month in 2006, 2007 and 2008. DDT concentrations were compared to fish tissue guidelines where it was found that some sections of the Marsh experience concentrations which have the potential to impact the health of biota in the immediate area. Varying weather conditions between study years revealed the importance of precipitation in transporting DDT through the marsh. Precipitation above or equaling long-term normals occurred in 2006 and 2008 which coincided with higher DDT concentrations than the significantly drier year of 2007. The information gained in this study will play a valuable role for both terrestrial and aquatic ecosystem managers in understanding how historic DDT use in the Holland Marsh may still be affecting this environment and Lake Simcoe today.