Dry deposition of polycyclic aromatic compounds to various land covers in the Athabasca oil sands region

Abstract

AbstractA framework was developed to estimate dry deposition of polycyclic aromatic compounds (PACs), including 17 polycyclic aromatic hydrocarbons (PAHs), 21 alkylated PAHs, and 5 parent and alkylated dibenzothiophenes (DBTs), to various land covers surrounding three monitoring sites in the Athabasca oil sands region. Modeled dry deposition velocities for various gaseous PACs and over various land covers were mostly in the range of 0.01–0.5 cm s−1 with median and annual mean values between 0.08 and 0.24 cm s−1, comparable with literature values obtained from field studies. Annual dry deposition of the sum of PAHs was estimated to range from 330 to 560 μg m−2 over forested canopies surrounding the three sites and from 270 to 490 μg m−2 over grass and shrubs. The corresponding values are 3920–5380 and 2850–4920 μg m−2 for the sum of 21 alkylated PAHs, and are 230–1120 and 450–930 μg m−2 for the sum of 5 DBTs. The three monitoring sites are situated nearby the Athabasca River, and the direct annual atmospheric dry deposition to water surface was estimated to range from 350 to 500, 3170 to 4530, and 170 to 840 μg m−2 for PAHs, alkylated PAHs, and DBTs, respectively. Alkylated PAHs contributed 80% of the total dry and 60% of the total wet deposition budget, suggesting the importance of including this group of PAHs in the atmospheric deposition budget estimation for subsequent ecosystem impact studies.