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Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked
urban area
European Aerosol Conference 2015 - Milan (Italy), September 6-11, 2015
S. Rovelli(1), S. Zauli Sajani(2), A. Cattaneo(1), I. Ricciardelli(3), A. Trentini(3), D. Bacco(3), V. Poluzzi(3), P. Lauriola(2) and D.M. Cavallo(1)
(1) Department of Science and High Technology, University of Insubria, via Valleggio 11, 22100 Como, Italy (2) Regional Centre for Environment and Health, ARPA Emilia-Romagna, via Begarelli 13, 41121 Modena, Italy
(3) Regional Centre for Urban Areas, ARPA Emilia-Romagna, via Rocchi 19, 40138 Bologna, Italy
Introduction 2
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
General Project:
• «SUPERSITO» Project: improve the knowledge regarding the environmental and health aspects of fine and ultrafine particles, both indoors and outdoors (http://www.arpa.emr.it/supersito)
• 7 Work Packages («Linee Progettuali» - LP) to develop and realize an accurate survey on the atmospheric pollution in the Emilia-Romagna Region, through the monitoring of physical, chemical and toxicological parameters that will be then used as a valid support in epidemilogical and environmental studies
• LP5: «Human exposure to Particulate Matter (PM) in indoor environments» • Characterize the human exposure to airborne pollutants of outdoor origin
in indoor environments, with a particular focus on PM mass and chemical composition
Aims – LP5 3
General aim «LP5» Focus on the variability of human exposure to air pollution in urban areas, with particular regards to the traffic source, that is considered the main source of fine and ultrafine particles in urban environments not directly infleunced by industrial emissions. Data used to assess:
a) Human health risk associated with a different proximity to traffic sources b) Differences in human health risk due to PM exposure during the summer period and
the winter season Study 1. Assessment of I/O ratios and spatial variability of traffic-related air pollutants simultaneously measured at a traffic site and a residential site, located in a low traffic area (Zauli Sajani et al., 2015)
Study 2. Assessment of concentration trends between two locations of the same building, that are at the front-side and at the back-side of the bulding itself
Study 3. Assessment of spatial variability along the vertical profile
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Aims – Study 2 4
• Detrimental effects on human health due to the exposure to PM and other traffic-related air pollutants
• Limited epidemiological evidences of adverse health outcomes associated with a different proximity to traffic sources
• Most of the time spent indoors
Need of an accurate assessment of indoor exposures to the outdoor air pollution Development of an experimental approach to:
Characterize the indoor and outdoor concentrations of PM2.5 (mass and chemical composition), UFPs (number concentration and size distribution) and gaseous pollutants (CO and NO2)
Investigate the street-side/back-side trends and differences of those pollutants
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
• Environmental monitoring of PM2.5, UFPs, CO and NO2 at two sites with different
characteristics in relation to the traffic source (street- and back-side of a two-storey building) – urban area of Bologna, Northern Italy
• Indoor sites selected on the basis of the following characteristics:
uninhabited and with no indoor sources similar in terms of volumes and building materials at the same height from the street level with a comparable Air Exchange Rate (AER)
• Two monitoring campaigns conducted at the two locations – summer (11th – 25th June
2013) and winter session (28th November 2013 – 13th December 2013)
• Indoor and outdoor sampling performed simultaneously on the street- and back-side of the study building
Street-side
Materials and Methods – Study design 5
Street-side
Back-side
Back-side
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Materials and Methods – Study design 6
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
• Measurements based on the tracer gas-decay technique, using CO2 as tracer gas, to verify the estimated AERs (ASTM Standard E741-95 Method)
• AERs controlled by installing in each room a mechanical system, set at a specific value
in order to obtain an estimated AER of about 0.4 h-1
Materials and Methods – Sampling Methods 7
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
PM2.5: 24-h PM2.5 concentrations collected via Skypost (flow rate of 2.3 m3h-1) • Gravimetric mass determination (UNI EN 12341) • Chemical analysis for:
- Organic (OC) and Elemental Carbon (EC) – Thermal Optical Trasmittance (TOT) - Metals (As, Cd, Fe, La, Pb, Sb, Sn, Mn, V, Zn) – ICP-MS - Ions (NH4
+, NO3-, SO4
2-, K+) – Ion chromatography (IC)
UFPs: continuous measurements by means of FMPS NO2: collection by radial symmetry diffusive samplers (Radiello®)
• Summer: 15 days of exposure time • Winter: two one-week samplings
CO: continuous measurements by means of Langan T15v electrochemical analyzers
• Zeroing and calibrating procedure performed before and after the monitoring campaign in a glove bag using two certified standard CO gas mixtures (< 50 ppb and 10.3 ppm)
• Correction for temperature on the basis of specific experimental quadratic equations, because of the known interference of temperature on the instrumental baseline
• Sampling limited to the cold season, due to the excessive interference on the output signal when temperatures are elevated (> 28/30 °C)
Results – PM2.5 Mass and Chemical Composition 8
Front-side Back-side
Outdoor Indoor
I/O
Outdoor Indoor
I/O n
Mean n
Mean n
Mean n
Mean
(min - max) (min - max) (min - max) (min - max)
24-h PM2.5 (µg/m3)
Summer 11 15.6 11 15.5 0.99 11 11.1 11 8.5 0.77
(11.3 – 23.8) (11.5 – 20.1) (7.5 – 16.5) (3.8 – 12.8)
Winter 15 47.1 14 26.5 0.56 15 43.4 15 20.2 0.47
(27.0 – 68.1) (16.4 – 41.1) (23.9 – 63.7) (9.5 – 35.7)
Total 26 31.3 25 21.7 0.69 26 27.3 26 14.4 0.53
(11.3 – 68.1) (11.5 – 41.4) (7.5 – 63.7) (3.8 – 35.7)
• PM2.5 outdoor winter levels more than three times higher, on average, compared to the summer data
• Small but significant differences (p < 0.001) in PM2.5 outdoor concentrations between front- and back-side (Ofront/Oback = 1.13)
• Indoor gradients more pronounced (Ifront/Iback = 1.50) • I/O ratios < 1, lower at the back-side and during the cold season
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
0,0
7,0
14,0
21,0
28,0
35,0
V As Cd Sn Sb Pb Zn Mn La
0,003% 0,002% 0,001% 0,01% 0,004% 0,023% 0,12% 0,023% 0,00%
0,006% 0,002% 0,001% 0,018% 0,007% 0,024% 0,13% 0,026% 0,00%
0,004% 0,002% 0,001% 0,009% 0,006% 0,026% 0,13% 0,020% 0,00%
0,006% 0,003% 0,001% 0,009% 0,004% 0,036% 0,17% 0,026% 0,00%
Out front Ind front Out back Ind back
0,0
1,5
3,0
4,5
6,0
7,5
9,0
OC EC NH4+ NO3- SO42- K+ Fe
28,2% 12,7% 9,3% 26,2% 10,6% 1,4% 0,7%
31,4% 19,8% 4,1% 5,9% 9,8% 1,7% 1,2%
28,7%
8,2% 10,4% 28,4% 11,7% 1,6% 0,4%
41,5%
11,8%
5,3% 7,1%
14,7% 2,4% 0,5%
Out front Ind front Out back Ind back
Results – PM2.5 Mass and Chemical Composition 9
• OC and NO3- as the largest
contributors to the outdoor PM2.5 mass, followed by EC, SO4
2- and NH4+
• Primary role of OC also indoors, with a pronounced decrease of NO3
- (I/Ofront = 0.16; I/Oback = 0.13) and NH4
+ (I/Ofront = 0.30; I/Oback = 0.27)
• Metals: minor component (< 0.3%) – primary role played by Fe and Zn
Mean contributions of the chemical species to the average indoor and outdoor PM2.5 levels, at both indoor and outdoor sites. Concentrations are expressed in µg/m3 (Figure a) and ng/m3 (Figure b)
(a)
(b)
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Results - PM2.5 Mass and Chemical Composition 10
Outdoor Indoor
Front/Back p-value Front/Back p-value
Elemental Carbon (EC) 1.76 < 0.001 2.53 < 0.001
Iron (Fe) 1.73 0.122 3.66 0.001
Manganese (Mn) 1.31 0.003 1.5 0.002
Tin (Sn) 1.30 0.246 3.02 < 0.001
Total Carbon (TC) 1.2 0.016 1.45 < 0.001
Organic Carbon (OC) 1.13 0.038 1.14 0.008
Zinc (Zn) 1.11 0.053 1.20 0.008
Nitrates (NO3-) 1.06 0.073 1.25 0.086
Sulphates (SO42-) 1.04 0.184 1.01 0.889
Ammonium (NH4+) 1.02 0.456 1.14 0.129
Vanadium (V) 1.01 0.741 1.35 0.002
Lanthanum (La) 1.00 0.486 1.20 0.138
Arsenic (As) 1.00 0.966 1.07 0.171
Cadmium (Cd) 1.00 0.802 1.07 0.866
Lead (Pb) 0.99 0.782 1.01 0.686
Potassium (K+) 0.98 0.012 1.03 0.279
Antimony (Sb) 0.88 0.591 2.25 0.002
• Significant differences between outdoor front- and back- average levels for EC and Mn
• Large, but not statistically significant, the outdoor trends for Fe and Sn
• Same patterns confirmed indoors, with indoor differences higher than outdoor
• Largest Ifront/Iback ratios for Fe and Sn, with values more than three times higher at the street- compared to the back-site
• EC: important component of diesel exhaust
particulate • Mn and Sn: typical markers of vehicle
emissions for PM2.5 • Tyre wear, vehicle component detachment,
fluid leakage: known sources of elements (e.g. Cu, Mn, Fe)
• Traffic-induced road dust resuspension: secondary contributor to fine-sized aerosol
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Results - UFPs Number Concentration and Size Distribution 11
Front-side Back-side
Outdoor Indoor
I/O
Outdoor Indoor
I/O n
Mean n
Mean n
Mean n
Mean
(min - max) (min - max) (min - max) (min - max)
1-h UFPs (pt/cm3)
Summer 353 15502 353 5109 0.33 353 6169 353 2932 0.48
(2118 - 38367) (1472 - 10773) (647 - 24308) (213 - 7901)
Winter 299 36994 299 10595 0.29 299 8948 299 4266 0.48
(3095 - 120931) (2854 - 21142) (1781 - 26860) (1730 - 8854)
Total 652 25358 652 7625 0.30 652 7444 652 3544 0.48
(2118 - 120931) (1472 - 21142) (647 - 26860) (213 - 8854)
• Large and significant differences for the UFPs number concentration, both indoors (Ifront/Iback = 2.2; p < 0.001) and outdoors (Ofront/Oback = 3.4; p < 0.001)
• Higher differences during the cold season
• I/O UFPs ratios < 1 and lower than I/O PM2.5 ratios (electrostatic deposition)
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Results - UFPs Number Concentration and Size Distribution 12
• Multimodal distribution at the outdoor front-side • Sharp peaks – higher during the cold season – at about
20 and 30-40 nm - Particles directly emitted by vehicles - Freshly nucleated particles formed when the hot
exhaust gases expelled from the tailpipe of a vehicle are diluted with ambient air
• Less pronounced peak in the 30-40 nm size range at the outdoor back-side
• Plateau in the indoor distributions - Aitken mode (40-50 nm) - Accumulation mode (100-150 nm)
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Results – Gaseous pollutants 13
Front-side Back-side Outdoor Indoor
I/O
Outdoor Indoor
I/O n
Mean n
Mean n
Mean n
Mean (min - max) (min - max) (min - max) (min - max)
1-h CO (ppm)
Winter 452 1.28 452 1.11 0.87 124 0.51 117 0.24 0.47
(0.25 – 2.85) (0.34 – 2.37) (0.21 – 1.29) (0.01 – 0.55)
NO2 (µg/m3)
Summer 1 61.8 2 47.6* 0.77 Data missing 2 38.0*
Winter 4 97.0** 4 50.8** 0.52 4 77.2** 4 48.9** 0.63
Total 5 78.9 6 49.6 0.63 4 77.2 6 43.5 0.56 *Concentration value obtained as mean value of diffusive samplers exposed in duplicate for 15 days **Concentration value obtained as mean value of duplicates exposed during two one-week samplings Precision, expressed as coefficient of variability (CV%) from duplicate measurements, was always good (3.0 – 10.6 %)
CO • I/O ratios < 1 (absence of indoor CO sources) • Marked differences between front- and back-
side (Ifront/Iback = 4.6; Ofront/Oback = 2.5) • Strong and significant correlation (r = 0.93; p <
0.05) between both hourly and daily concentrations of CO and UFPs at the front-side
NO2
• NO2 winter levels higher than those monitored during summer
• I/O ratios < 1 • Slight gradient in relation to the proximity to
the traffic source
Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Conclusions 14
• Study focused on the assessment of differences and trends between the two opposite sides of a building for typical traffic-related air pollutants
• Marked and significant differences for UFPs, CO and elements as EC, Mn, Sn, Fe in relation to the proximity to the traffic source
• Significant, but less relevant, the spatial gradients for PM2.5 and NO2
• Important differences also in the shape of the outdoor particle size distribution
• Indoor levels much lower than outdoors, especially for UFPs, CO, nitrates, ammonium and indoor trends quite similar to those found outdoors
- Potentially high and not negligeable variability in the human exposure to outdoor airborne pollutants also for people living in the same building, due to a different
proximity to traffic sources
- Valid support in epidemiological studies Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area
European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
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Indoor and outdoor airborne pollutants levels on the street- and back-side of a building in a trafficked urban area European Aerosol Conference, 2015 – Milan (Italy), September 6-11, 2015
Sabrina Rovelli, Ph.D. Student Department of Science and High Technology University of Insubria Via Valleggio 11, 22100 Como - Italy sabrina.rovelli@uninsubria.it
Thanks for your attention