This paper presents a new CAPRAM-GECKO-A protocol for mechanism auto-generation of aqueous-phase organic processes. For the development, kinetic data in the literature were reviewed and a database ...with 464 aqueous-phase reactions of the hydroxyl radical with organic compounds and 130 nitrate radical reactions with organic compounds has been compiled and evaluated. Five different methods to predict aqueous-phase rate constants have been evaluated with the help of the kinetics database: gas-aqueous phase correlations, homologous series of various compound classes, radical reactivity comparisons, Evans-Polanyi-type correlations, and structure-activity relationships (SARs). The quality of these prediction methods was tested as well as their suitability for automated mechanism construction. Based on this evaluation, SARs form the basis of the new CAPRAM-GECKO-A protocol. Evans-Polanyi-type correlations have been advanced to consider all available H atoms in a molecule besides the H atoms with only the weakest bond dissociation enthalpies (BDEs). The improved Evans-Polanyi-type correlations are used to predict rate constants for aqueous-phase NO.sub.3 and organic compounds reactions.
Particle hygroscopicity plays a key role in determining the particle deposition in the human respiratory tract (HRT). In this study, the effects of hygroscopicity and mixing state on regional and ...total deposition doses on the basis of the particle number concentration for children, adults, and the elderly were quantified using the Multiple-Path Particle Dosimetry
model, based on the size-resolved particle hygroscopicity measurements at
HRT-like conditions (relative humidity = 98 %) performed in the North China Plain. The measured particle population with an external mixing state was dominated by hygroscopic particles (number fraction = (91.5 ± 5.7) %, mean ± standard deviation (SD); the same below). Particle hygroscopic growth in the HRT led to a reduction by around 24 % in the total doses of submicron particles for all age groups. Such a reduction was mainly caused by the growth of hygroscopic particles and was more pronounced in the pulmonary and tracheobronchial regions. Regardless of hygroscopicity, the elderly group of people had the highest total dose among three age groups, while
children received the maximum total deposition rate. With 270 nm in
diameter as the boundary, the total deposition doses of particles smaller
than this diameter were overestimated, and those of larger particles were
underestimated, assuming no particle hygroscopic growth in the HRT. From the perspective of the daily variation, the deposition rates of hygroscopic
particles with an average of (2.88 ± 0.81) × 109 particles h−1 during the daytime were larger than those at night ((2.32 ± 0.24) × 109 particles h−1). On the contrary, hydrophobic particles interpreted as freshly emitted soot and primary organic aerosols exhibited higher deposition rates at nighttime ((3.39 ± 1.34) × 108 particles h−1) than those in the day ((2.58 ± 0.76) × 108 particles h−1). The traffic emissions during the rush hours enhanced the deposition rate of hydrophobic particles. This work provides a more explicit assessment of the impact of hygroscopicity and mixing state on the deposition pattern of submicron particles in the HRT.
Residential wood combustion is a widespread practice in
Europe with a serious impact on air quality, especially in mountainous
areas. While there is a significant number of studies conducted in deep
...urbanized valleys and basins, little is known about the air pollution
processes in rural shallow hollows, where around 30 % of the people in mountainous areas across Europe live. We aim to determine the influence of
ground temperature inversions on wood combustion aerosol pollution in hilly,
rural areas. The study uses Retje karst hollow (Loški Potok, Slovenia)
as a representative site for mountainous and hilly rural areas in central and south-eastern Europe with residential wood combustion. Sampling with a mobile
monitoring platform along the hollow was performed in December 2017 and
January 2018. The backpack mobile monitoring platform was used for the
determination of equivalent black carbon (eBC) and particulate matter
(PM) mass concentrations along the hollow. To ensure high quality of mobile measurement data, intercomparisons of mobile instruments with
reference instruments were performed at two air quality stations during
every run. Our study showed that aerosol pollution events in the relief
depression were associated with high local emission intensities originating
almost entirely from residential wood burning and shallow temperature
inversions (58 m on average). The eBC and PM mass concentrations showed
stronger associations with the potential temperature gradient (R2=0.8) than with any other meteorological parameters taken into account
(ambient temperature, relative humidity, wind speed, wind direction, and precipitation). The strong association between the potential temperature
gradient and pollutant concentrations suggests that even a small number of
emission sources (total 243 households in the studied hollow) in similar
hilly and mountainous rural areas with frequent temperature inversions can
significantly increase the levels of eBC and PM and deteriorate local air quality. During temperature inversions the measured mean eBC and
PM2.5 mass concentrations in the whole hollow were as high as 4.5±2.6 and 48.0 ± 27.7 µg m−3,
respectively, which is comparable to larger European urban centres.
Here we report results of a detailed analysis of the urban and non-urban
contributions to particulate matter (PM) concentrations and source contributions in five European
cities, namely Schiedam (the ...Netherlands, NL), Lens (France, FR), Leipzig
(Germany, DE), Zurich (Switzerland, CH) and Barcelona (Spain, ES). PM
chemically speciated data from 12 European paired monitoring sites (one
traffic, five urban, five regional and one continental background) were analysed by
positive matrix factorisation (PMF) and Lenschow's approach to assign
measured PM and source contributions to the different spatial levels. Five
common sources were obtained at the 12 sites: sulfate-rich (SSA) and nitrate-rich (NSA) aerosols,
road traffic (RT), mineral matter (MM), and aged sea salt (SS). These sources explained from 55 % to 88 % of PM
mass at urban low-traffic-impact sites (UB) depending on the country. Three
additional common sources were identified at a subset of sites/countries,
namely biomass burning (BB) (FR, CH and DE), explaining an additional 9 %–13 % of PM
mass, and residual oil combustion (V–Ni) and primary industrial (IND) (NL and ES), together explaining an additional
11 %–15 % of PM mass. In all countries, the majority of PM measured at UB
sites was of a regional+continental (R+C) nature (64 %–74 %). The R+C PM
increments due to anthropogenic emissions in DE, NL, CH, ES and FR
represented around 66 %, 62 %, 52 %, 32 % and 23 %, respectively,
of UB PM mass. Overall, the R+C PM increments due to natural and
anthropogenic sources showed opposite seasonal profiles with the former
increasing in summer and the latter increasing in winter, even if exceptions
were observed. In ES, the anthropogenic R+C PM increment was higher in
summer due to high contributions from regional SSA and V–Ni sources, both
being mostly related to maritime shipping emissions at the Spanish sites.
Conversely, in the other countries, higher anthropogenic R+C PM increments
in winter were mostly due to high contributions from NSA and BB regional
sources during the cold season. On annual average, the sources showing
higher R+C increments were SSA (77 %–91 % of SSA source contribution at the
urban level), NSA (51 %–94 %), MM (58 %–80 %), BB (42 %–78 %) and IND (91 %
in NL). Other sources showing high R+C increments were photochemistry and coal combustion (97 %–99 %;
identified only in DE). The highest regional SSA increment was observed in
ES, especially in summer, and was related to ship emissions, enhanced
photochemistry and peculiar meteorological patterns of the Western
Mediterranean. The highest R+C and urban NSA increments were observed in
NL and associated with high availability of precursors such as NOx and
NH3. Conversely, on average, the sources showing higher local
increments were RT (62 %–90 % at all sites) and V–Ni (65 %–80 % in ES and
NL). The relationship between SSA and V–Ni indicated that the contribution
of ship emissions to the local sulfate concentrations in NL has strongly
decreased since 2007 thanks to the shift from high-sulfur- to low-sulfur-content fuel used by ships. An improvement of air quality in the five cities
included here could be achieved by further reducing local (urban) emissions
of PM, NOx and NH3 (from both traffic and non-traffic sources) but
also SO2 and PM (from maritime ships and ports) and giving high
relevance to non-urban contributions by further reducing emissions of
SO2 (maritime shipping) and NH3 (agriculture) and those from
industry, regional BB sources and coal combustion.
Fine particulate matter (PM2.5) samples collected at Mount (Mt.) Tai in the North China Plain during summer 2014 were analyzed for dicarboxylic acids and related compounds (oxocarboxylic acids and ...α-dicarbonyls) (DCRCs). The total concentration of DCRCs was 1050±580 and 1040±490 ng m-3 during the day and night, respectively. Although these concentrations were about 2 times lower than similar measurements in 2006, the concentrations reported here were about 1–13 times higher than previous measurements in other major cities in the world. Molecular distributions of DCRCs revealed that oxalic acid (C2) was the dominant species (50 %), followed by succinic acid (C4) (12 %) and malonic acid (C3) (8 %). WRF modeling revealed that Mt. Tai was mostly in the free troposphere during the campaign and long-range transport was a major factor governing the distributions of the measured compounds at Mt. Tai. A majority of the samples (79 %) had comparable concentrations during the day and night, with their day–night concentration ratios between 0.9 and 1.1. Multi-day transport was considered an important reason for the similar concentrations. Correlation analyses of DCRCs and their gas precursors and between C2 and sulfate indicated precursor emissions and aqueous-phase oxidations during long-range transport also likely play an important role, especially during the night. Source identification indicated that anthropogenic activities followed by photochemical aging accounted for about 60 % of the total variance and were the dominant source at Mt. Tai. However, biomass burning was only important during the first half of the measurement period. Measurements of potassium (K+) and DCRCs were about 2 times higher than those from the second half of the measurement period. The concentration of levoglucosan, a biomass burning tracer, decreased by about 80 % between 2006 and 2014, indicating that biomass burning may have decreased between 2006 and 2014.
To fight against the first wave of coronavirus disease 2019
(COVID-19) in 2020, lockdown measures were implemented in most European
countries. These lockdowns had well-documented effects on human ...mobility. We
assessed the impact of the lockdown implementation and relaxation on air
pollution by comparing daily particulate matter (PM), nitrogen dioxide
(NO2) and ozone (O3) concentrations, as well as particle number
size distributions (PNSDs) and particle light absorption coefficient in situ
measurement data, with values that would have been expected if no COVID-19 epidemic had occurred
at 28 sites across Europe for the period 17 February–31 May 2020.
Expected PM, NO2 and O3 concentrations were calculated from the
2020 Copernicus Atmosphere Monitoring Service (CAMS) ensemble forecasts,
combined with 2019 CAMS ensemble forecasts and measurement data. On average,
lockdown implementations did not lead to a decrease in PM2.5 mass
concentrations at urban sites, while relaxations resulted in a +26 ± 21 % rebound. The impacts of lockdown implementation and relaxation on
NO2 concentrations were more consistent (−29 ± 17 and +31 ± 30 %, respectively). The implementation of the lockdown measures
also induced statistically significant increases in O3 concentrations
at half of all sites (+13 % on average). An enhanced oxidising capacity
of the atmosphere could have boosted the production of secondary aerosol at
those places. By comparison with 2017–2019 measurement data, a
significant change in the relative contributions of wood and fossil fuel
burning to the concentration of black carbon during the lockdown was
detected at 7 out of 14 sites. The contribution of particles smaller than 70 nm to the total number of particles significantly also changed at most of
the urban sites, with a mean decrease of −7 ± 5 % coinciding with
the lockdown implementation. Our study shows that the response of PM2.5
and PM10 mass concentrations to lockdown measures was not systematic at
various sites across Europe for multiple reasons, the relationship between
road traffic intensity and particulate air pollution being more complex than
expected.
The aerosol size-segregated chemical composition was analyzed at an urban (Bologna) and a rural (San Pietro Capofiume) site in the Po Valley, Italy, during June and July 2012, by ion-chromatography ...(major water-soluble ions and organic acids) and evolved gas analysis (total and water-soluble carbon), to investigate sources and mechanisms of secondary aerosol formation during the summer. A significant enhancement of secondary organic and inorganic aerosol mass was observed under anticyclonic conditions with recirculation of planetary boundary layer air but with substantial differences between the urban and the rural site. The data analysis, including a principal component analysis (PCA) on the size-resolved dataset of chemical concentrations, indicated that the photochemical oxidation of inorganic and organic gaseous precursors was an important mechanism of secondary aerosol formation at both sites. In addition, at the rural site a second formation process, explaining the largest fraction (22 %) of the total variance, was active at nighttime, especially under stagnant conditions. Nocturnal chemistry in the rural Po Valley was associated with the formation of ammonium nitrate in large accumulation-mode (0.42–1.2 µm) aerosols favored by local thermodynamic conditions (higher relative humidity and lower temperature compared to the urban site). Nocturnal concentrations of fine nitrate were, in fact, on average 5 times higher at the rural site than in Bologna. The water uptake by this highly hygroscopic compound under high RH conditions provided the medium for increased nocturnal aerosol uptake of water-soluble organic gases and possibly also for aqueous chemistry, as revealed by the shifting of peak concentrations of secondary compounds (water-soluble organic carbon (WSOC) and sulfate) toward the large accumulation mode (0.42–1.2 µm). Contrarily, the diurnal production of WSOC (proxy for secondary organic aerosol) by photochemistry was similar at the two sites but mostly affected the small accumulation mode of particles (0.14–0.42 µm) in Bologna, while a shift to larger accumulation mode was observed at the rural site. A significant increment in carbonaceous aerosol concentration (for both WSOC and water-insoluble carbon) at the urban site was recorded mainly in the quasi-ultrafine fraction (size range 0.05–0.14 µm), indicating a direct influence of traffic emissions on the mass concentrations of this range of particles.
A method is presented to quantify the low-molecular-weight organic acids such
as
formic, acetic, propionic, butyric, pyruvic, glycolic, oxalic,
malonic, succinic, malic, glutaric, and methanesulfonic ...acid in the
atmospheric gas and particle phases, based on a combination of the Monitor for
AeRosols and Gases in ambient Air (MARGA) and an additional ion
chromatography (Compact IC) instrument. Therefore, every second hourly
integrated MARGA gas and particle samples were collected and analyzed by the
Compact IC, resulting in 12 values per day for each phase. A proper separation
of the organic target acids was initially tackled by a laboratory IC
optimization study, testing different separation columns, eluent compositions
and eluent flow rates for both isocratic and gradient elution. Satisfactory
resolution of all compounds was achieved using a gradient system with two
coupled anion-exchange separation columns. Online pre-concentration with an
enrichment factor of approximately 400 was achieved by solid-phase extraction
consisting of a methacrylate-polymer-based sorbent with quaternary ammonium
groups. The limits of detection of the method range between 0.5 ng m−3
for malonate and 17.4 ng m−3 for glutarate. Precisions are below
1.0 %, except for glycolate (2.9 %) and succinate (1.0 %).
Comparisons of inorganic anions measured at the TROPOS research site in
Melpitz, Germany, by the original MARGA and the additional Compact IC are in
agreement with each other (R2 = 0.95–0.99). Organic acid concentrations
from May 2017 as an example period are presented. Monocarboxylic acids were
dominant in the gas phase with mean concentrations of 306 ng m−3 for
acetic acid, followed by formic (199 ng m−3), propionic
(83 ng m−3), pyruvic (76 ng m−3), butyric (34 ng m−3)
and glycolic acid (32 ng m−3). Particulate glycolate, oxalate and
methanesulfonate were quantified with mean concentrations of 26, 31 and
30 ng m−3, respectively. Elevated concentrations
of gas-phase formic acid and particulate oxalate in the late afternoon indicate photochemical
formation as a source.
Abstract
Large airports are a major source of ultrafine particles, which spread across densely populated residential areas, affecting air quality and human health. Jet engine lubrication oils are ...detectable in aviation-related ultrafine particles, however, their role in particle formation and growth remains unclear. Here we show the volatility and new-particle-formation ability of a common synthetic jet oil, and the quantified oil fraction in ambient ultrafine particles downwind of Frankfurt International Airport, Germany. We find that the oil mass fraction is largest in the smallest particles (10-18 nm) with 21% on average. Combining ambient particle-phase concentration and volatility of the jet oil compounds, we determine a lower-limit saturation ratio larger than 1 × 10
5
for ultra-low volatility organic compounds. This indicates that the oil is an efficient nucleation agent. Our results demonstrate that jet oil nucleation is an important mechanism that can explain the abundant observations of high number concentrations of non-refractory ultrafine particles near airports.
Residential wood combustion contributing to airborne particulate matter (PM10) was studied for 1 year at two sites in the village of Melpitz. Significant excess pollution was observed at the Melpitz ...center compared to that at the TROPOS research station Melpitz reference site, situated only 700 m away. Local concentration increments at the village site for the combustion PM constituents organic carbon, elemental carbon, levoglucosan, and benzoapyrene were determined under appropriate wind directions, and their winter mean values were 0.7 μg m–3, 0.3 μg m–3, 0.1 μg m–3, and 0.4 ng m–3, representing relative increases over the regional background concentration of 24, 70, 61, and 107%, respectively. Yearly, weekly, and diurnal profiles of village increments suggest residential heating as the dominant source of this excess pollution, mainly originating from wood combustion. Receptor modeling using positive matrix factorization quantified 4.5 μg m–3 wood combustion PM at the village site, representing an increment of 1.9 μg m–3 and an increase of ∼75% over the 2.6 μg m–3 regional background wood combustion PM. This increment varied with season, temperature, and boundary layer height and reached daily mean values of 4–6 μg m–3 during unfavorable meteorological conditions. Potential health effects were estimated and resulted in an all-cause mortality from short-term exposure to wood combustion PM of 2.1 cases per 100,000 inhabitants and year for areas with similar wood smoke levels as observed in Melpitz. The excess cancer risk from the concentrations of polycyclic aromatic hydrocarbons was 6.4 per 100,000. For both health metrics, the very local contributions from the village itself were about 40–50%, indicating a strong potential for mitigation through local-scale policies. A compilation of literature data demonstrates wood combustion to represent a major source of PM pollution in Germany, with average winter-time contributions of 10–20%. The present study quantifies the negative impacts of heating with wood in rural residential areas, where the continuous monitoring of air quality is typically lacking. Further regulation of this PM source is warranted in order to protect human health.
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