The dynamics of persistent organic pollutants in air and in selected lakes of the Canadian Rocky Mountains.

Abstract

This thesis examines the concentrations of persistent organic pollutants (POPs) in air and in selected lakes of the Canadian Rocky Mountains. Water was sampled from seven lakes spanning an elevation of 1430 meters from the Interior Plains to the Western Range of the Canadian Rocky Mountains. Air samples were taken at four of these sites, encompassing an altitudinal gradient of 1205 meters. Air and water samples were used to determine net air-water gas exchange fluxes of six POPs at these four sites. This study revealed that air and water concentrations of several persistent organic pollutants did not change significantly with elevation. However, spring pulses of hexachlorocyclohexanes (HCHs) in the lakes were found to coincide with snowmelt, and concentrations of POPs were highest at Bow Lake during the year with the highest snow pack. It was observed that temperature differences with altitude had little impact on the magnitude and direction of air-water gas exchange, indicating net fluxes of POPs were most sensitive to fluctuations in relative air and water concentrations. Air-water gas exchange was compared with the total lake inventory and with estimated losses by outflow. In general, it was revealed that deposition by air-water gas exchanges was an important source of POPs with lower Henry's law constants, such as alpha and gamma-HCH, and net volatilisation was an important loss for the compounds with higher Henry's law constants, (e.g. hexachlorobenzene (HCB) and dieldrin).