Mass Concentration and Size-Distribution of Atmospheric Particulate Matter in an Urban Environment

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 ) established by the World Health Organization.

Estimation of the Inhaled Dose of Airborne Pollutants during Commuting: Case Study and Application for the General Population

“…PM 2.5 samples were also collected using a GK2.05 sampler (BGI Inc., Waltham, MA, USA), operated with a sampling pump with a flow rate equal to 4 L/min; particles were collected using polytetrafluoroethylene filters. The mass concentration was determined by gravimetric analysis following a standard reference method [ 12 , 13 ] and previous studies [ 14 , 15 , 16 ]. Gravimetric data were used to correct the PM data acquired via the direct-reading instrument by calculating a daily correction factor applied a posteriori to the whole PM dataset [ 17 ].…”

Precision and Accuracy of a Direct-Reading Miniaturized Monitor in PM2.5 Exposure Assessment

“…The average RH was equal to 67.8%, while the temperature ranged from −0.9 °C to 14.0 °C (mean: 7.7 °C). The sampling site was characterized by generally low wind speeds (also reported in a previous study carried out in the same area [ 36 ]), mainly because of the sampling location (approximately 1.8 km from the banks of Lake Como) and the local topographic scenario (with moraine hills which surrounded the area). During the warm period, the wind intensity was <1.5 m/s in 96% of the cases (and <1 m/s in 62.7% of the cases), while during the cold period, the wind speed was <1.5 in 70.6% of the cases.…”

“…It is well known that the factory calibration factor of a photometer cannot be used to obtain accurate data when there are marked differences in terms of shape, morphologies, size-distribution, chemical composition, and reflectance properties between the analyzed particulate and the standard dust. As reported in different studies that were conducted in the study area [ 20 , 36 , 48 ], the local urban particulate is typically less dense than the standard dust, which could result in a significant overestimation of PM concentrations by optical particle counter and nephelometers. This can explain the underestimation of average concentrations by a factor of about 0.5 in summer and an overestimation of mean concentrations by a factor of three during winter.…”

“…Indeed, it was shown that, with larger particles, AB seemed to underestimate PM 2.5 concentrations whereas when the smallest fraction was predominant, PM concentrations tended to be overestimated. This is the case for the winter size-distribution at the sampling site, which is characterized by a sharp increase in the accumulation-mode peak during the cold season [ 36 ].…”

“…The campaign was performed during two different periods (warm period: 24 July 2017–8 August 2017; cold period: 10 January 2018–7 February 2018) at an urban background site described elsewhere [ 20 , 36 ]. An urban background site was chosen according to the Guidelines for Air Quality Monitoring Network provided by the Agency for Environmental Protection and Technical Services [ 37 ] to acquire data representative of the average pollution levels in the study area.…”