Abstract
To investigate the ambient mass concentration, size-distribution and temporal variability of atmospheric particulate matter (PM), a long-term monitoring campaign was undertaken at an urban background site in Como, Northern Italy, from May 2015 to March 2016. A 13-stage Low Pressure Impactor (DLPI) was used for the collection of size-segregated particulates in the 0.028-10 μm size range. The results revealed a good level of agreement between DLPI and a co-located Harvard-type PM_(2.5) Impactor, allowing them to be classified as comparable and characterized by a reciprocal predictability. The PM concentration levels varied greatly between the different 5-days monitoring sessions, with higher mean mass concentrations during the heating season. Appreciable seasonal differences were found for particles between 0.15 and 1.60 μm that, on average, registered concentration levels 3.5 times higher during the heating season (mean: 28.2 μg m^(-3); median: 24.4 μg m^(-3)) compared to the non-heating season (mean: 8.3 μg m^(-3); median: 7.6 μg m^(-3)). No relevant and significant differences were detected for the coarser ranges (＞ 1.60 μm). Temporal variabilities were influenced by typical PM urban sources (e.g., household heating, traffic), that significantly affected fine and submicrometer particles, and were related to meteorological factors. Ambient air particles exhibited a trimodal distribution: a first and sharp peak more pronounced during the heating season was identified between 0.3 and 0.5 μm and two other slight peaks in the coarse mode were centered on approximately 3 and 8 μm. No relevant differences were found in the shape of the size-distribution between the two investigated seasons. The mean PM_(2.5) (22.4 μg m^(-3)) and PM_(10) (27.7 μg m^(-3)) concentrations monitored in the study area exceeded the annual Air Quality Guideline Values (respectively equal to 10 μg m^(-3) and 20 μg m^(-3)) established by the World Health Organization.
Highlights
Numerous epidemiological and toxicological studies have documented strong correlations between measured particulate matter (PM) levels and adverse health outcomes (Erdinger et al, 2005; Schwarze et al, 2006; Brook et al, 2010; Stafoggia et al, 2013; Raaschou-Nielsen et al, 2016)
DLPI-PM2.5 concentration levels were, on average, lower than those simultaneously monitored by Harvardtype Impactor (HI), with DLPI-HI disagreements that increased with increasing ambient concentration levels (Fig. 3)
The results found in our survey at the URban Background (URB) station for PM0.26 (2.6 ± 0.6 and 6.1 ± 2.4 μg m–3 during the non-heating and the heating season, respectively) were from 2 to 3 times lower than the corresponding PM0.25 concentrations measured along urban traffic routes by Spinazzè et al (2015), mainly because of the specific monitoring protocol that was properly designed to include road and transit microenvironments
Summary
Numerous epidemiological and toxicological studies have documented strong correlations between measured particulate matter (PM) levels and adverse health outcomes (Erdinger et al, 2005; Schwarze et al, 2006; Brook et al, 2010; Stafoggia et al, 2013; Raaschou-Nielsen et al, 2016). The relationships between PM concentrations, chemical characteristics and the potential hazardous effects on human health are related to the penetration, deposition and clearance of particles into the human respiratory tract (Lippmann et al, 1980). As extensively documented in the literature (Lippmann et al, 1980; Heyder et al, 1986; Donaldson et al, 2002), particles > 10 μm are only deposited in the extrathoracic region by inertial impaction and they are not able to reach the nonciliated tract of the respiratory system. Particles in the 1–10 μm size range are deposited due to impaction in the extrathoracic and upper bronchial airways, while sedimentation governs their deposition in the lower bronchial and alveolar region. The impaction deposition increases with increasing particle size whereas sedimentation
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