Evaluating the effectiveness of low-sulphur marine fuel regulations at improving urban ambient PM 2.5 air quality: Source apportionment of PM 2.5 at Canadian Atlantic and Pacific coast cities with implementation of the North American Emissions Control Area.

Ambient fine size fraction particulate matter (PM _2.5 ) sources were resolved by positive matrix factorization at two Canadian cities on the Atlantic and Pacific coast over the 2010-2016 period, corresponding to implementation of the North American Emissions Control Area (NA ECA) low-sulphur marine fuel regulations. Source types contributing to local PM _2.5 concentrations were: ECA regulation-related (residual oil, anthropogenic sulphate), urban transportation and residential (gasoline, diesel, secondary nitrate, biomass burning, road dust/soil), industry (refinery, Pb-enriched), and largely natural (biogenic sulphate, sea salt). Anthropogenic sources accounted for approximately 80 % of PM _2.5 mass over 2010-2016. Anthropogenic and biogenic sources of PM _2.5 -sulphate were separated and apportioned. Anthropogenic PM _2.5 -sulphate was approximately 2-3 times higher than biogenic PM _2.5 -sulphate prior to implementation of the NA ECA low-S marine fuel regulations, decreasing to 1-2 times higher after regulation implementation. Non-marine anthropogenic sources (gasoline, road dust, local industry factors) were shown to together contribute 38 % - 45 % of urban PM _2.5 . At both coastal cities, the residual oil and anthropogenic sulphate factors clearly reflected the effects of the low-S fuel regulations at reducing primary and secondary sulphur-related PM _2.5 emissions. Comparing a pre-regulation and post-regulation period, residual oil combustion PM _2.5 decreased by 0.24-0.25 μg/m ³ (94%-95 % decrease) in both cities and anthropogenic sulphate PM _2.5 decreased by 0.78 μg/m ³ in Halifax (47 % decrease) and 0.71 μg/m ³ in Burnaby (58 % decrease). Regulation-related PM _2.5 across these factors decreased by approximately 1 μg/m ³ after regulation implementation, providing a quantified lower estimate of the beneficial influence of the regulations on urban ambient PM _2.5 concentrations. Further reductions in coastal city ambient PM _2.5 may best consider air quality strategies that include multiple sources, including marine shipping and non-marine anthropogenic source types given this analysis found that marine vessel emissions remain an important source of urban ambient PM _2.5 .
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Crown Copyright © 2023. Published by Elsevier B.V. All rights reserved.)