We present size-segregated measurements of cloud condensation nucleus (CCN) activity of aged aerosol sampled at Finokalia, Crete, during the Finokalia Aerosol Measurement Experiment of summer 2007 ...(FAME07). From analysis of the data, hygroscopicity and activation kinetics distributions are derived. The CCN are found to be highly hygroscopic, (expressed by a size- and time- averaged hygroscopicity parameter κ ∼ 0.22), with the majority of particles activating at ~0.5–0.6 % supersaturation. Air masses originating from Central-Eastern Europe tend to be associated with higher CCN concentrations and slightly lower hygroscopicity (κ ∼ 0.18) than for other airmass types. The particles were always well mixed, as reflected by the high activation ratios and narrow hygroscopicity distribution widths. Smaller particles (~40 nm) were found to be more hygroscopic (~0.1κ units higher) than the larger ones (~100 nm). The particles with diameters less than 80 nm exhibited a diurnal hygroscopicity cycle (with κ peaking at ~14 h local time), consistent with photochemical aging and volatilization of less hygroscopic material from the aerosol. Use of bulk chemical composition and the aerosol number distribution results in excellent CCN closure when applying Köhler theory in its simplest form. Using asymptotic and threshold droplet growth analysis, the "aged" organics present in the aerosol were found not to suppress or delay the water uptake kinetics of particles in this environment.
While cloud condensation nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this ...phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (the value of κ was lower by 0.2–0.4 for 60 nm particles compared with 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in the afternoon, which was very likely due to the higher sulfate-to-organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneous with the formation of new particles during daytime, particles formed during the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range-transported particles.
Water-soluble ions (Cl
−,
NO
3
−
,
SO
4
2
−
,
C
2
O
4
−
, Na
+,
NH
4
+
, K
+, Mg
2+,Ca
2+), water soluble organic carbon (WSOC), organic and elemental carbon (OC, EC) and trace metals (Al, Ca, Ti, V, ...Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb) were measured in aerosol PM
10 samples above the megacity of Istanbul between November 2007 and June 2009. Source apportionment analysis using Positive Matrix Factorization (PMF) indicates that approximately 80% of the PM
10 is anthropogenic in origin (secondary, refuse incineration, fuel oil and solid fuel combustion and traffic). Crustal and sea salt account for 10.2 and 7.5% of the observed mass, respectively. In general, anthropogenic (except secondary) aerosol shows higher concentrations and contributions in winter. Mean concentration and contribution of crustal source is found to be more important during the transitional period due to mineral dust transport from North Africa. During the sampling period, 42 events exceeding the limit value of 50 μg m
−3 are identified. A significant percentage (91%;
n = 38) of these exceedances is attributed to anthropogenic sources. Potential Source Contribution Function analysis highlights that Istanbul is affected from distant sources from Balkans and Western Europe during winter and from Eastern Europe during summer. On the other hand, Istanbul sources influence western Black Sea and Eastern Europe during winter and Aegean and Levantine Sea during summer.
Airborne particulate matter in the PM2.5 and PM1 size ranges has been sampled at three sites within the Mediterranean urban area of the Athens Basin, representing background, roadside-industrialized ...and coastal background locations. With the principal aim to identify the sources and discriminate the contribution of the regional input versus the local one, simultaneous chemical characterization with respect to carbonaceous and ionic species was also carried out on the collected samples. In general, the average recorded values were within the Mediterranean concentration range. The constant prevalence of the ionic mass (52%–79%) over one of the carbonaceous, being combined with the occurrence of its maximum rates at the coastal background environment (74%–79% and 73%–77% for PM2.5 and PM1, respectively) leads to the hypothesis that the fine PM pollution in the basin, especially for the remote locations, is evidently governed by the external intrusion. Even at the polluted atmosphere of the roadside-industrialized environment, the PM mass was regionally originated, with the corresponding input reaching up to 87% (northward flow). Applying factor analysis on the PM2.5 database it came obvious that the sources which were responsible for the configured PM burden were not fully differentiated not only between the different types of environment but also between the exceedances and the clean air events. The contribution of the secondary, marine and combustion processes was constant at all the stations of the network, while a continuous input of crustal particles characterized both the roadside-industrialized and the coastal atmosphere. Finally, the episodic values show a general common signal of secondary mixed ΡΜ emissions, high influence of both regional and local pollution spikes, confirming the earlier findings for the significance of transportation.
•Discrimination of the external PM input versus the local one•Chemical mass closure•Factor analysis: source identification•Impact of meteorology on the PM burden (origin, profile)
Aged organic aerosol (OA) was measured at a remote coastal site on the island of Crete, Greece during the Finokalia Aerosol Measurement Experiment-2008 (FAME-2008), which was part of the EUCAARI ...intensive campaign of May 2008. The site at Finokalia is influenced by air masses from different source regions, including long-range transport of pollution from continental Europe. A quadrupole aerosol mass spectrometer (Q-AMS) was employed to measure the size-resolved chemical composition of non-refractory submicron aerosol (NR-PM1), and to estimate the extent of oxidation of the organic aerosol. Factor analysis was used to gain insights into the processes and sources affecting the OA composition. The particles were internally mixed and liquid. The largest fraction of the dry NR-PM1 sampled was ammonium sulfate and ammonium bisulfate, followed by organics and a small amount of nitrate. The variability in OA composition could be explained with two factors of oxygenated organic aerosol (OOA) with differing extents of oxidation but similar volatility. Hydrocarbon-like organic aerosol (HOA) was not detected. There was no statistically significant diurnal variation in the bulk composition of NR-PM1 such as total sulfate or total organic aerosol concentrations. However, the OA composition exhibited statistically significant diurnal variation with more oxidized OA in the afternoon. The organic aerosol was highly oxidized, regardless of the source region. Total OA concentrations also varied little with source region, suggesting that local sources had only a small effect on OA concentrations measured at Finokalia. The aerosol was transported for about one day before arriving at the site, corresponding to an OH exposure of approximately 4×1011 molecules cm−3 s. The constant extent of oxidation suggests that atmospheric aging results in a highly oxidized OA at these OH exposures, regardless of the aerosol source.
A large fraction of atmospheric organic aerosol (OA) originates from natural emissions that are oxidized in the atmosphere to form secondary organic aerosol (SOA). Isoprene (IP) and monoterpenes (MT) ...are the most important precursors of SOA originating from forests. The climate impacts from OA are currently estimated through parameterizations of water uptake that drastically simplify the complexity of OA. We combine laboratory experiments, thermodynamic modeling, field observations, and climate modeling to (1) explain the molecular mechanisms behind RH‐dependent SOA water‐uptake with solubility and phase separation; (2) show that laboratory data on IP‐ and MT‐SOA hygroscopicity are representative of ambient data with corresponding OA source profiles; and (3) demonstrate the sensitivity of the modeled aerosol climate effect to assumed OA water affinity. We conclude that the commonly used single‐parameter hygroscopicity framework can introduce significant error when quantifying the climate effects of organic aerosol. The results highlight the need for better constraints on the overall global OA mass loadings and its molecular composition, including currently underexplored anthropogenic and marine OA sources.
Plain Language Summary
The interaction of airborne particulate matter (“aerosols”) with water is of critical importance for processes governing climate, precipitation, and public health. It also modulates the delivery and bioavailability of nutrients to terrestrial and oceanic ecosystems. We present a microphysical explanation to the humidity‐dependent water uptake behavior of organic aerosol, which challenges the highly simplified theoretical descriptions used in, e.g., present climate models. With the comprehensive analysis of laboratory data using molecular models, we explain the microphysical behavior of the aerosol over the range of humidity observed in the atmosphere, in a way that has never been done before. We also demonstrate the presence of these phenomena in the ambient atmosphere from data collected in the field. We further show, using two state‐of‐the‐art climate models, that misrepresenting the water affinity of atmospheric organic aerosol can lead to significant biases in the estimates of the anthropogenic influence on climate.
Key Points
Phase separation effects explain differences in water affinity of biogenic secondary organic aerosol (SOA) at subsaturation and supersaturation
Laboratory data for monoterpene and isoprene SOA are representative of field observations with corresponding gas‐phase organic profiles
Importance of organic aerosol‐water interactions for global climate is governed by highly uncertain organic aerosol budgets
Aerosol chemical composition over Istanbul Theodosi, C.; Im, U.; Bougiatioti, A. ...
The Science of the total environment,
05/2010, Letnik:
408, Številka:
12
Journal Article
Recenzirano
This study examines the chemical composition of aerosols over the Greater Istanbul Area. To achieve this 325 (PM
10) aerosol samples were collected over Bosphorus from November 2007 to June 2009 and ...were analysed for the main ions, trace metals, water-soluble organic carbon (WSOC), organic (OC) and elemental carbon (EC).
PM
10 levels were found to be in good agreement with those measured by the Istanbul Municipality air quality network, indicating that the sampling site is representative of the Greater Istanbul Area. The main ions measured in the PM
10 samples were Na
+, Ca
2+ and non-sea-salt sulphates (nss-SO
4
2−). On average, 31% of Ca
2+ was found to be associated with carbonates. Trace elements related to human activities (as Pb, V, Cd and Ni) obtained peak values during winter due to domestic heating, whereas natural origin elements like Al, Fe and Mn peaked during the spring period due to dust transport from Northern Africa. Organic carbon was found to be mostly primary and elemental carbon was strongly linked to fuel oil combustion and traffic. Both OC and EC concentrations increased during winter due to domestic heating, while the higher WSOC to OC ratio during summer can be mostly attributed to the presence of secondary, oxidised and more soluble organics. Factor analysis identified six components/sources for aerosol species in PM
10, namely traffic/industrial, crustal, sea-salt, fuel–oil combustion, secondary and ammonium sulfate.
To assess the origin and transformation of carbonaceous material in the marine boundary layer of the Eastern Mediterranean, a total of 111 size segregated aerosol samples have been collected using a ...12-stage Small-Deposit-area low-volume-Impactor (SDI) covering an almost 3 year period. The samples have been analyzed for organic (OC), elemental (EC), water-soluble organic carbon (WSOC) and ionic components. Maxima of OC, EC and WSOC mass size distributions were found in the accumulation mode (0.449 μm) with occasionally a minor, secondary peak in the coarse mode (2.68 μm). OC and WSOC concentrations peak during summertime due to photochemistry, while EC during autumn, and spring. In general, almost 2/3 of OC and EC concentrations are found in the PM1 fraction of the aerosol with OC being mostly secondary and therefore highly oxidized and water-soluble to a great extent (∼70%). Using the EC-tracer method, it was found that 83 ± 11% of the PM10 organic carbon is secondary, with the percentage reaching ∼70% for the PM1 fraction, a value in very good accordance to WSOC/OC ratio. Ammonium sulfate accounts for 75.5 ± 21.7% and 9.3 ± 1.9% of the aerosol mass in the fine and coarse fraction respectively, exhibiting maximum concentrations also in the accumulation mode. It was estimated that, on average, sea salt and mineral dust account for 33% and 45% of the coarse inorganic mass fraction, respectively.
► Carbonaceous aerosol constitutes a significant part of submicron mass fraction. ► Size distribution of OC, EC, WSOC and ions was performed during a 3 year period. ► OC, EC and WSOC exhibit bimodal distribution with maximum in the accumulation mode. ► 83.5 ± 11% of the PM10 OC is secondary. ► 70% of the fine mode OC is water-soluble with high summer and low winter values.
A carefully designed experimental study based on the monitoring of fine airborne particles, was carried out at three different locations (suburban background, traffic-industrial, coastal background) ...of an urban Mediterranean area, the Athens Basin. Understanding of the PM2.5 and PM1 nature has an important policy implication. In total, five hundred and nineteen samples were chemically analyzed with respect to carbonaceous (organic/elemental carbon) and ionic (NH4+, K+, Mg2+, Ca2+, NO3−, Cl−, SO42−) species. The dataset consists one of the very few in the Mediterranean which simultaneously deals with the carbonaceous and ionic components of fine aerosol fractions, especially for PM1. Daily PM2.5 averages often exceeded the E.U. limit values, with their mass being mainly composed of PM1. The most important constituents of secondary particles were SO42− and organic carbon, with both accounting for 56.4%–64.3% and 60.5%–62.3% of the total PM2.5 and PM1 mass, respectively. Regional sources, marine/crustal elements, combustion sources and traffic were indicated by factor analysis as the greatest contributors to the mass of both PM2.5 and PM1 fractions, accounting for 85.3% and 83.6%, respectively of the total variance in the system. It is worthy to note, the key role of the prevailing atmospheric conditions to the configuration of the obtained picture of the particulate pollution.
► One of the very few Mediterranean PM2.5, PM1 ionic and carbonaceous species datasets. ► Factor analysis indicated 4 sources. ► PM fractions are mainly composed of sulfates and organic carbon. ► Aerosols patterns are related to both regional and local sources. ► Atmospheric conditions have obvious impact on the pollution picture of an area.
PDF
