Atmospheric dry deposition of sulfur and nitrogen in the Athabasca Oil Sands Region, Alberta, Canada

摘要

Due to the potential ecological effects on terrestrial and aquatic ecosystems from atmospheric deposition in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, this study was implemented to estimate atmospheric nitrogen (N) and sulfur (S) inputs. Passive samplers were used to measure ambient concentrations of ammonia (NH_3), nitrogen dioxide (NO_2). nitric aciditrous acid (HNO_3/HONO), and sulfur dioxide (SO_2) in the AOSR. Concentrations of NO_2 and SO_2 in winter were higher than those in summer, while seasonal differences of NH_3 and HNO_3/ HONO showed an opposite trend, with higher values in summer. Concentrations of NH_3, NO_2 and SO_2 were high close to the emission sources (oil sands operations and urban areas). NH_3 concentrations were also elevated in the southern portion of the domain indicating possible agricultural and urban emission sources to the southwest. HNO_3, an oxidation endpoint, showed wider ranges of concentrations and a larger spatial extent Concentrations of NH_3, NO_2, HNO_3/HONO and SO_2 from passive measurements and their monthly deposition velocities calculated by a multi-layer inference model (MLM) were used to calculate dry deposition of N and S. NH_3 contributed the largest fraction of deposited N across the network, ranging between 0.70-1.25 kg N ha~(-1) yr~(-1), HNO_3/HONO deposition ranged between 030-0.90 kg N ha~(-1) yr~(-1) and NO_2 deposition between 0.03-0.70 kg N ha~(-1) yr~(-1). During the modeled period, average dry deposition of the inorganic gaseous N species ranged between 1.03 and 2.85 kg N ha~(-1) yr~(-1) and SO_4-S deposition ranged between 0.26 and 2.04 kg ha~(-1) yr~(-1). Comparisons with co-measured ion exchange resin throughfall data (8.51 kg S ha~(-1) yr~(-1)) indicate that modeled dry deposition combined with measured wet deposition (137 kg S ha~(-1) yr~(-1)) underestimated S deposition. Gas phase NH_3 (71%) and HNO_3 plus NO_2 (79%) dry deposition fluxes dominated the total deposition of NH_4-N and NO_3-N, respectively.