Source apportionment of fine and coarse particles at a roadside and urban background site in London during the 2012 summer ClearfLo campaign

Abstract

London, like many major cities, has a noted air pollution problem, and a better understanding of the sources of airborne particles in the different size fractions will facilitate the implementation and effectiveness of control strategies to reduce air pollution. Thus, the trace elemental composition of the fine and coarse fraction were analysed at hourly time resolution at urban background (North Kensington, NK) and roadside (Marylebone Road, MR) sites within central London. Unlike previous work, the current study focuses on measurements during the summer providing a snapshot of contributing sources, utilising the high time resolution to improve source identification. Roadside enrichment was observed for a large number of elements associated with traffic emissions (Al, S, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb and Zr), while those elements that are typically from more regional sources (e.g. Na, Cl, S and K) were not found to have an appreciable increment. Positive Matrix Factorization (PMF) was applied for the source apportionment of the particle mass at both sites with similar sources being identified, including sea salt, airborne soil, traffic emissions, secondary inorganic aerosols and a Zn-Pb source. In the fine fraction, traffic emissions was the largest contributing source at MR (31.9%), whereas it was incorporated within an "urban background" source at NK, which had contributions from wood smoke, vehicle emissions and secondary particles. Regional sources were the major contributors to the coarse fraction at both sites. Secondary inorganic aerosols (which contained influences from shipping emissions and coal combustion) source factors accounted for around 33% of the PM at NK and were found to have the highest contributions from regional sources, including from the European mainland. Exhaust and non-exhaust sources both contribute appreciably to PM levels at the MR site, highlighting the continuing importance of vehicle-related air pollutants at roadside.

First Results of the “Carbonaceous Aerosol in Rome and Environs (CARE)” Experiment: Beyond Current Standards for PM10

“…It is noteworthy that black and brown carbon are important tracers for PM sources so that the possibility of retrieving their concentrations together with a wide elemental characterisation allows an enhancement in source apportionment studies. Indeed, streaker data with 1 h-time resolution are widely used in the literature (e.g., [62][63][64][65][66] and references therein) to achieve a better identification and quantification either of sources showing a sub-daily modulation (e.g., traffic or wood burning for domestic heating) and/or impacting for a limited time slot (e.g., Saharan dust/wildfires advection events, sporadic industrial emissions or fireworks, . .…”

High-resolution sampling and analysis of ambient particulate matter in the Pearl River Delta region of southern China: source apportionment and health risk implications

“…In order to compare the relationship between the range of analytes measured in PM and the total PM mass, a mass closure approach was used. Ideally, when elemental analysis and organic compound analysis have been undertaken on the same sample one can reconstruct the mass using the following general equation for ambient samples as a first approximation (Cahill et al, 1989;Cohen, 1999;Malm et al, 1994): The reconstructed mass (RCM) is based on the fact that the six composite variables or "pseudo" sources given in Eq. (2) are generally the major contributors to fine and coarse particle mass and are based on geochemical principles and constraints.…”

“…For RCM, it is assumed that sulfate is present in fully neutralized form as ammonium sulfate. [Sulfate] therefore represents the ammonium sulfate contribution to aerosol mass with the multiplicative factor of 4.125 [S] to account for ammonium ion and oxygen mass (i.e., (NH 4 ) 2 SO 4 = ((14 + 4) × 2 + 32 + (16 × 4) / 32); Cahill et al, 1989;Cohen, 1999;Malm et al, 1994).…”

“…A majority of PM source apportionment studies in the literature are documented at a lower temporal resolution, typically in 12-24 h integrated filter samples (Pant and Harrison, 2012;Belis et al, 2013). Only limited studies have applied PMF to determine the trace element emission sources at a high time (hourly) resolution (Gao et al, 2016;Dall'Osto et al, 2013;Pancras et al, 2013;Moreno et al, 2011;Crilley et al, 2017;Visser et al, 2015a;Ancelet et al, 2012Ancelet et al, , 2014. Increasing the time resolution of measurements can capture the impact of PM concentration and personal exposure from many intermittent sources such as biomass combustion or industry emission plumes.…”

Sources and Temporal Variations of Coarse Particulate Matter (PM) in Central Tehran, Iran

“…Moreover, some studies have investigated coarse PM effects on visibility, which induces haze events and visibility impairment [22,23]. Coarse particles consisted of crustal elements as well as vehicular tire and brake wear products [22,24]. These particles might have originated from suburban backgrounds and can be carried out to urban areas depending on the particle transport pattern (i.e., proximity to the source of pollution and prevailing wind speed and direction) [25,26].…”