McLay Emma M, Donaldson D James
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada.
ACS Earth Space Chem. 2023 Feb 27;7(3):533-547. doi: 10.1021/acsearthspacechem.2c00305. eCollection 2023 Mar 16.
Using publicly available data from the National Air Pollution Surveillance Program, water-soluble ion mole fractions in PM and PM were extracted for 2010, 2012, 2013, and 2015 at six locations across Canada. Fine particle ion content was dominated by ammonium sulfate, with ammonium to sulfate ratios largely approaching 2 and no seasonal or geographic trends. Sulfate and nitrate mole fractions were negatively correlated in the fine particles, consistent with their expected pathways of entry into PM. Coarse particle composition varied depending on location and season. Coastal stations were dominated by sodium and chloride year-round while inland stations showed high amounts of these ions only during the colder months, where road salt is often applied. A negative correlation between nitrate and chloride mole fractions as well as a positive correlation between nitrate concentrations and "missing" chloride provides evidence for near-ubiquitous nitrate displacement of chloride. This displacement was strongly indicated in coastal sites and also evident inland, especially during cold months. Weak evidence for nitrogen dioxide as the source of nitrate was found for inland sites, but none was found for coastal sites, suggesting a nonlocal source for the particulate nitrate precursor.
利用国家空气污染监测计划的公开数据，提取了2010年、2012年、2013年和2015年加拿大六个地点的PM和PM中的水溶性离子摩尔分数。细颗粒离子含量以硫酸铵为主，铵与硫酸的比例大多接近2，且无季节性或地理趋势。细颗粒中硫酸盐和硝酸盐的摩尔分数呈负相关，这与其进入PM的预期途径一致。粗颗粒组成因地点和季节而异。沿海站点全年以钠和氯为主，而内陆站点仅在寒冷月份（经常使用道路融雪盐）时这些离子含量较高。硝酸盐和氯的摩尔分数之间呈负相关，以及硝酸盐浓度与“缺失”氯之间呈正相关，这为氯几乎无处不在的硝酸盐替代提供了证据。这种替代在沿海地区强烈表明，在内陆地区也很明显，尤其是在寒冷月份期间。在内陆站点发现了二氧化氮作为硝酸盐来源的微弱证据，但在沿海站点未发现，这表明颗粒硝酸盐前体有非本地来源。
