Search

Ambient fine particulate matter (PM 2.5) data were collected in the lower City of Hamilton, Ontario to apportion the sources of this pollutant over an 18-month period. Hamilton has complex topographical features that may result in worsened air pollution within the lower city, thus, dispersion-normalized, multi-time resolution factor analysis (DN-MT-FA) was used to identify and quantify contributions of factors in a manner that reduced the influence of local meteorology. These factors were secondary organic aerosols type 1 (SOA_1), particulate nitrate (pNO3), particulate sulphate (pSO4), primary traffic organic matter (PTOM), Steel/metal processing and vehicular road dust emissions (Steel & Mobile) and, secondary organic aerosols type 2 (SOA_2) with origins ranging from mainly regional to mainly local. Factors that were mainly local (PTOM, Steel & Mobile, SOA_2) contributed up to 17% of the average PM 2.5 mass while mixed local/regional factors (pNO3, pSO4) made up 43% on average, indicating the potential for further reduction of harmful PM concentrations locally. Of particular interest from a health protection perspective, was the composition of PM 2.5 on days when an exceedance of the 24-hr WHO air quality guideline for this pollutant was observed. In general, SOA_1 was found to drive summer exceedances while pNO3 dominated in the winter. During the summer period, SOA_1 was attributable to wildfires in the northern parts of Canada while local traffic sources in winter contributed to the high levels of pNO3. While local, industrial factors only had minor relative mass contributions during exceedances, they are high in highly oxidized organic species (SOA_2) and toxic metals (Steel & Mobile). Thus, they are likely to have more impacts on human health. The methods and results described in this work will be useful in understanding prevalent sources of particulate matter pollution in the ambient air in the presence of complex topography and meteorological effects. [Display omitted] • DN-MT-FA apportioned sources of PM 2.5 in a city with complex topography. • Dispersion-normalization helps to understand local/regional origins of factors. • Industrially sourced factors had most PM 2.5 metals and unique organic species. • Summer exceedance of WHO AQG for PM 2.5 mainly driven by secondary organic aerosols. • Winter exceedance of WHO AQG for PM 2.5 largely driven by particulate nitrate. [ABSTRACT FROM AUTHOR]

Abstract: The long-term trends in atmospheric reactive nitrogen (Nr) species at 12 Canadian Air and Precipitation Monitoring Network (CAPMoN) stations (9 with air and precipitation observations) across Canada were evaluated during the period 1988–2007. The non-parametric Mann–Kendall test was used to determine monotonic trends in the annual average concentrations of gaseous nitric acid (HNO3), particulate nitrate , particulate ammonium , wet ammonium and wet nitrate in response to emission reductions primarily driven by the Canada–United States Air Quality Agreement. Annual air concentrations (1988–2007) of and HNO3 significantly decreased at all CAPMoN stations, while concentrations increased at 6 of 9 stations. Precipitation had no significant or consistent trend; in contrast precipitation concentrations significantly decreased at 9 of the 11 stations and increased at one (non-significant). Normalized temporal sequences showed consistent patterns across Canada for several Nr species. Annual average air concentrations of and HNO3 had synchronous time-series with consistently decreasing concentrations across all CAPMoN stations (1988–2007), in contrast, had a complex temporal pattern, characterised by an initial period of no change (1988–1993), followed by a period of steep increase (1993–2002) and then a period of steep decrease (2002–2007). The period of steep decrease started around 2002 and was mirrored by all Nr species (except wet ) at all CAPMoN stations. The steep decrease was consistent with the observed decrease in NOx emissions from power plants and on-road vehicles in the United States and Canada. Legislated emission reductions have resulted in significant decreases in Nr concentrations except for , as such uncontrolled ammonia emissions continue to be a significant source of Nr. [Copyright &y& Elsevier]

Increased nitrate (NO3) concentrations in streamwaters draining forested catchments are reportedly an early indicator of nitrogen (N) saturation. Nitrate concentrations in streams draining 16 forested catchments in south central Ontario were monitored over a 16-year period, during which time N bulk deposition was relatively constant (∼9 kg ha-1 yr-1). Mean annual NO3 concentrations in streams were both highly variable among catchments and among years, although patterns of annual concentration were similar among many catchments. Coherence analysis identified two stream groupings. Shallow soils, moderate slopes, low NO3 concentration, and a large wetland component characterized the first group. The second group had primarily upland characteristics including deeper soils, steeper slopes, higher NO3 concentrations, and a much smaller wetland component. Patterns in NO3 concentration in wetland-influenced streams appeared to be related to summer drought and cumulative frost depth, whereas NO3 concentrations in upland-draining streams appeared to be related to both mean annual air temperature and summer drought Because a number of different climate parameters as well as the physical character of the catchments apparently influence NO3 export, NO3 concentrations in streams are not a good indicator of N saturation in this region. [ABSTRACT FROM AUTHOR]