scholarly journals Insights into tropical cloud chemistry in Réunion (Indian Ocean): results from the BIO-MAÏDO campaign

2022 ◽  
Vol 22 (1) ◽  
pp. 505-533
Author(s):  
Pamela A. Dominutti ◽  
Pascal Renard ◽  
Mickaël Vaïtilingom ◽  
Angelica Bianco ◽  
Jean-Luc Baray ◽  
...  
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Chemical Composition ◽  
Aqueous Phase ◽  
Cloud Water ◽  
Sea Salt ◽  
Emission Sources ◽  
Air Mass ◽  
Low Solubility

Abstract. We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAÏDO” (Bio-physico-chemistry of tropical clouds at Maïdo (Réunion Island): processes and impacts on secondary organic aerosols' formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March–April 2019 in Réunion (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. Comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-solubility volatile organic compounds, VOCs). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g. chloride, sodium) demonstrating ocean–cloud exchanges. Indeed, Na+ and Cl− dominate the inorganic composition contributing to 30 % and 27 %, respectively, to the average total ion content. The strong correlations between these species (r2 = 0.87, p value: < 0.0001) suggest similar air mass origins. However, the average molar Cl-/Na+ ratio (0.85) is lower than the sea-salt one, reflecting a chloride depletion possibly associated with strong acids such as HNO3 and H2SO4. Additionally, the non-sea-salt fraction of sulfate varies between 38 % and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 ± 18.4 mg C L−1), with levels reaching up to 62 mg C L−1. This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with the land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Even though a minor contribution of VOCs (oxygenated and low-solubility VOCs) to the total dissolved organic carbon (DOC) (0.62 % and 0.06 %, respectively) has been observed, significant levels of biogenic VOC (20 to 180 nmol L−1) were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed by measurements obtained in both the gas and aqueous phases and deduced experimental gas-/aqueous-phase partitioning was compared with Henry's law equilibrium to evaluate potential supersaturation or unsaturation conditions. The evaluation reveals the supersaturation of low-solubility VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, evidencing a deviation from thermodynamically expected partitioning in the aqueous-phase chemistry in this highly impacted tropical area.

scholarly journals Insights into tropical cloud chemistry at Reunion Island (Indian Ocean): results from the BIO-MAÏDO campaign

2021 ◽  
Author(s):  
Pamela A. Dominutti ◽  
Pascal Renard ◽  
Mickaël Vaïtilingom ◽  
Angelica Bianco ◽  
Jean-Luc Baray ◽  
...  
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Chemical Composition ◽  
Indian Ocean ◽  
Aqueous Phase ◽  
Cloud Water ◽  
Emission Sources ◽  
Reunion Island ◽  
Réunion Island

Abstract. We present here the results obtained during an intensive field campaign conducted in the framework of the French “BIO-MAÏDO” (Bio-physico-chemistry of tropical clouds at Maïdo (Réunion Island): processes and impacts on secondary organic aerosols’ formation) project. This study integrates an exhaustive chemical and microphysical characterization of cloud water obtained in March–April 2019 at Reunion Island (Indian Ocean). Fourteen cloud samples have been collected along the slope of this mountainous island. A comprehensive chemical characterization of these samples is performed, including inorganic ions, metals, oxidants, and organic matter (organic acids, sugars, amino acids, carbonyls, and low-soluble volatile organic compounds (VOCs)). Cloud water presents high molecular complexity with elevated water-soluble organic matter content partly modulated by microphysical cloud properties. As expected, our findings show the presence of compounds of marine origin in cloud water samples (e.g., chloride, sodium) demonstrating ocean–cloud exchanges. However, the non-sea salt fraction of sulphate varies between 38 and 91 %, indicating the presence of other sources. Also, the presence of amino acids and for the first time in cloud waters of sugars, clearly indicates that biological activities contribute to the cloud water chemical composition. A significant variability between events is observed in the dissolved organic content (25.5 ± 18.4 mgC L−1), with levels reaching up to 62 mgC L−1. This variability was not similar for all the measured compounds, suggesting the presence of dissimilar emission sources or production mechanisms. For that, a statistical analysis is performed based on back-trajectory calculations using the CAT (Computing Atmospheric Trajectory Tool) model associated with land cover registry. These investigations reveal that air mass origins and microphysical variables do not fully explain the variability observed in cloud chemical composition, highlighting the complexity of emission sources, multiphasic transfer, and chemical processing in clouds. Additionally, several VOCs (oxygenated and low-soluble VOCs) were analysed in both gas and aqueous phases. Significant levels of biogenic low-soluble VOCs were detected in the aqueous phase, indicating the cloud-terrestrial vegetation exchange. Cloud scavenging of VOCs is assessed and compared to Henry’s law equilibrium to evaluate potential super or sub saturation conditions. The evaluation reveals the supersaturation of low-soluble VOCs from both natural and anthropogenic sources. Our results depict even higher supersaturation of terpenoids, suggesting their importance in the aqueous phase chemistry in highly impacted tropical areas.

A climatology of cloud chemistry for the eastern United States derived from the mountain cloud chemistry project

1993 ◽  
Vol 1 (1) ◽  
pp. 38-54 ◽  
Author(s):  
Volker A. Mohnen ◽  
Richard J. Vong
Keyword(s):  
United States ◽  
Chemical Composition ◽  
Chemical Analysis ◽  
Cloud Water ◽  
Cloud Base ◽  
Eastern United States ◽  
Cloud Chemistry ◽  
Air Mass ◽  
Ion Concentrations ◽  
Air Mass Trajectories

The chemical composition of clouds collected in the eastern United States has been intensely monitored over a 4-year period as part of the Mountain Cloud Chemistry Project. On the basis of these measurements we prepared a climatology for cloud chemistry, using simple statistical analyses tools and incorporating meteorological and cloud physical and chemical information. Five mountain stations have been established for cloud collection covering the northern and southern Appalachian Mountain range: Whiteface Mountain, New York; Mount Moosilauke, New Hampshire; Shenandoah Mountain, Virginia; Whitetop Mountain, Virginia; and Mount Mitchell, North Carolina. This review presents the major result from this 4-year measurement program. Cloud cover and cloud base over the eastern United States were deduced from the global real-time nephanalysis archives produced by the U.S. Air Force, augmented by local observations. Both active and passive cloud collectors were deployed to sample cloud water on an hourly basis, i.e., with sufficient time resolution to resolve synoptic scale phenomena. Chemical analysis of cloud water was performed by a central analytical laboratory with occasional on-site analysis to satisfy quality control procedures. Reliable methods now exist for collecting cloud-water samples in sufficient quantities for detailed chemical analysis. The chemical composition of cloud water varied significantly between sites. However, the differences in cloud-water ion concentration do not necessarily establish a geographic gradient between the sites but rather reflect differences in air-mass trajectories associated with the synoptic air-flow pattern and differences in sample location above cloud base. The dependence of cloud-water ion concentrations on synoptic weather type and observed differences in relative frequencies of warm sector, marine flow, and post-cold frontal synoptic types between northern and southern sites suggest that the north–south differences in cloud-water ion concentrations are related to cloud climatology at the northern sites. When air-mass trajectories shift from southwest to northwest, the concentrations of H+, SO42−, NO3− and NH4+ normally decrease but the southern sites continue to receive high concentrations under northwest flow. The height of cloud-water sample collection above cloud base was found to be an additional source of variability in both cloud-water chemistry and liquid-water content. Seasonal variation in cloud-water chemical composition was investigated at one site only. Sulfate levels were found to be significantly lower in supercooled clouds (i.e., during the 'cold' season) than in 'warm' clouds, but nitrate levels remained about the same.Key words: cloud chemistry, cloud frequency, air-mass trajectories, ANOVA.

scholarly journals On the relationship between cloud water composition and cloud droplet number concentration

2020 ◽  
Vol 20 (13) ◽  
pp. 7645-7665 ◽  
Author(s):  
Alexander B. MacDonald ◽  
Ali Hossein Mardi ◽  
Hossein Dadashazar ◽  
Mojtaba Azadi Aghdam ◽  
Ewan Crosbie ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Environmental Factors ◽  
Cloud Droplet ◽  
Cloud Water ◽  
Number Concentration ◽  
Sea Salt ◽  
Cloud Base ◽  
Cloud Height ◽  
Cloud Droplet Number Concentration ◽  
Total Sulfate

Abstract. Aerosol–cloud interactions are the largest source of uncertainty in quantifying anthropogenic radiative forcing. The large uncertainty is, in part, due to the difficulty of predicting cloud microphysical parameters, such as the cloud droplet number concentration (Nd). Even though rigorous first-principle approaches exist to calculate Nd, the cloud and aerosol research community also relies on empirical approaches such as relating Nd to aerosol mass concentration. Here we analyze relationships between Nd and cloud water chemical composition, in addition to the effect of environmental factors on the degree of the relationships. Warm, marine, stratocumulus clouds off the California coast were sampled throughout four summer campaigns between 2011 and 2016. A total of 385 cloud water samples were collected and analyzed for 80 chemical species. Single- and multispecies log–log linear regressions were performed to predict Nd using chemical composition. Single-species regressions reveal that the species that best predicts Nd is total sulfate (Radj2=0.40). Multispecies regressions reveal that adding more species does not necessarily produce a better model, as six or more species yield regressions that are statistically insignificant. A commonality among the multispecies regressions that produce the highest correlation with Nd was that most included sulfate (either total or non-sea-salt), an ocean emissions tracer (such as sodium), and an organic tracer (such as oxalate). Binning the data according to turbulence, smoke influence, and in-cloud height allowed for examination of the effect of these environmental factors on the composition–Nd correlation. Accounting for turbulence, quantified as the standard deviation of vertical wind speed, showed that the correlation between Nd with both total sulfate and sodium increased at higher turbulence conditions, consistent with turbulence promoting the mixing between ocean surface and cloud base. Considering the influence of smoke significantly improved the correlation with Nd for two biomass burning tracer species in the study region, specifically oxalate and iron. When binning by in-cloud height, non-sea-salt sulfate and sodium correlated best with Nd at cloud top, whereas iron and oxalate correlated best with Nd at cloud base.

scholarly journals Chemical composition and source attribution of sub-micrometre aerosol particles in the summertime Arctic lower troposphere

2021 ◽  
Vol 21 (8) ◽  
pp. 6509-6539
Author(s):  
Franziska Köllner ◽  
Johannes Schneider ◽  
Megan D. Willis ◽  
Hannes Schulz ◽  
Daniel Kunkel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Organic Matter ◽  
Chemical Composition ◽  
Dicarboxylic Acids ◽  
The Arctic ◽  
Source Attribution ◽  
Arctic Boundary Layer ◽  
Air Mass ◽  
Particle Composition ◽  
Aerosol Mass

Abstract. Aerosol particles impact the Arctic climate system both directly and indirectly by modifying cloud properties, yet our understanding of their vertical distribution, chemical composition, mixing state, and sources in the summertime Arctic is incomplete. In situ vertical observations of particle properties in the high Arctic combined with modelling analysis on source attribution are in short supply, particularly during summer. We thus use airborne measurements of aerosol particle composition to demonstrate the strong contrast between particle sources and composition within and above the summertime Arctic boundary layer. In situ measurements from two complementary aerosol mass spectrometers, the Aircraft-based Laser Ablation Aerosol Mass Spectrometer (ALABAMA) and an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), are presented alongside black carbon measurements from an single particle soot photometer (SP2). Particle composition analysis was complemented by trace gas measurements, satellite data, and air mass history modelling to attribute particle properties to particle origin and air mass source regions. Particle composition above the summertime Arctic boundary layer was dominated by chemically aged particles, containing elemental carbon, nitrate, ammonium, sulfate, and organic matter. From our analysis, we conclude that the presence of these particles was driven by transport of aerosol and precursor gases from mid-latitudes to Arctic regions. Specifically, elevated concentrations of nitrate, ammonium, and organic matter coincided with time spent over vegetation fires in northern Canada. In parallel, those particles were largely present in high CO environments (> 90 ppbv). Additionally, we observed that the organic-to-sulfate ratio was enhanced with increasing influence from these fires. Besides vegetation fires, particle sources in mid-latitudes further include anthropogenic emissions in Europe, North America, and East Asia. The presence of particles in the Arctic lower free troposphere, particularly sulfate, correlated with time spent over populated and industrial areas in these regions. Further, the size distribution of free tropospheric particles containing elemental carbon and nitrate was shifted to larger diameters compared to particles present within the boundary layer. Moreover, our analysis suggests that organic matter, when present in the Arctic free troposphere, can partly be identified as low molecular weight dicarboxylic acids (oxalic, malonic, and succinic acid). Particles containing dicarboxylic acids were largely present when the residence time of air masses outside Arctic regions was high. In contrast, particle composition within the marine boundary layer was largely driven by Arctic regional processes. Air mass history modelling demonstrated that alongside primary sea spray particles, marine biogenic sources contributed to secondary aerosol formation via trimethylamine, methanesulfonic acid, sulfate, and other organic species. Our findings improve our knowledge of mid-latitude and Arctic regional sources that influence the vertical distribution of particle chemical composition and mixing state in the Arctic summer.

Effect of diet and probiotic addition on chemical composition of free or particle-associated bacterial populations of the rumen

1998 ◽  
Vol 78 (1) ◽  
pp. 115-120 ◽  
Author(s):  
J. Chiquette ◽  
C. Benchaar
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Amino Acid ◽  
Chemical Composition ◽  
Volatile Fatty Acids ◽  
Solid Phase ◽  
Organic Matter Content ◽  
Latin Square ◽  
Matter Content ◽  
Bacterial Populations

Eight dairy heifers (297 ± 11 kg) fitted with a ruminal cannula were used in this study. The following diets were fed in a replicated, concurrently run 4 × 4 Latin square design: 1) 80% chopped timothy hay + 20% rolled barley (HF); 2) HF + 10 g head d−1 of a mixture of Saccharomyces cerevisiae and Aspergillus oryzae (HF + SA); 3) 50% chopped timothy hay + 47.6% rolled barley and 2.4% soya supplement (HC); 4) HC + SA. Feed was offered every 2 h. A sample of whole rumen contents (liquid and solid) was collected 1 h after the 07:00 h feeding to isolate the bacteria associated with the liquid phase (BAL) and the bacteria adherent to the solid phase (BAS). Organic matter (OM) content of BAS was greater (P ≤ 0.0001) than that of BAL, independently of the type of diet fed and of the presence or absence of the pro-biotic mixture. Oppositely, total nitrogen content (N), expressed as g 100 g−1 OM, was greater (P ≤ 0.0001) in the BAL fraction than in the BAS fraction, the difference in N between the two bacterial fractions being more pronounced with the HF diet (P ≤ 0.05). Organic matter content in both bacterial fractions was greater (P ≤ 0.05) when heifers were fed the HC diet. Addition of probiotic had no effect on OM or N content of each bacterial fraction. Significant differences between amino acid composition of BAL and BAS were observed for 10 out of 16 amino acids studied. For most amino acids, differences in content observed between BAL and BAS were maintained independently of the probiotic supplementation whereas diet affected the relative composition of the bacterial fractions for five amino acids. Finally, addition of probiotics did not affect molar proportions of ruminal volatile fatty acids, which were affected by the diet. Key words: Rumen bacteria, chemical composition, probiotic, amino acid

scholarly journals On the Relationship Between Cloud Water Composition and Cloud Droplet Number Concentration

2020 ◽  
Author(s):  
Alexander B. MacDonald ◽  
Ali Hossein Mardi ◽  
Hossein Dadashazar ◽  
Mojtaba Azadi Aghdam ◽  
Ewan Crosbie ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Environmental Factors ◽  
Cloud Droplet ◽  
Cloud Water ◽  
Number Concentration ◽  
Sea Salt ◽  
Cloud Base ◽  
Cloud Height ◽  
Cloud Droplet Number Concentration ◽  
Total Sulfate

Abstract. Aerosol-cloud interactions are the largest source of uncertainty in quantifying anthropogenic radiative forcing. The large uncertainty is, in part, due to the difficulty of predicting cloud microphysical parameters, such as the cloud droplet number concentration (Nd). Even though rigorous first-principle approaches exist to calculate Nd, the cloud and aerosol research community also relies on empirical approaches such as relating Nd to aerosol mass concentration. Here we analyze relationships between Nd and cloud water chemical composition, in addition to the effect of environmental factors on the degree of the relationships. Warm, marine, stratocumulus clouds off the California coast were sampled throughout four summer campaigns between 2011 and 2016. A total of 385 cloud water samples were collected and analyzed for 79 chemical species. Single- and multi-species log-log linear regressions were performed to predict Nd using chemical composition. Single-species regressions reveal that the species that best predicts Nd is total sulfate (R2adj = 0.40). Multi-species regressions reveal that adding more species does not necessarily produce a better model, as six or more species yield regressions that are statistically insignificant. A commonality among the multi-species regressions that produce the highest correlation with Nd was that most included sulfate (either total or non-sea salt), an ocean emissions tracer (such as sodium), and an organic tracer (such as oxalate). Binning the data according to turbulence, smoke influence, and in-cloud height allowed examination of the effect of these environmental factors on the composition-Nd correlation. Accounting for turbulence, quantified as the standard deviation of vertical wind speed, showed that the correlation between Nd with both total sulfate and sodium increased at higher turbulence conditions, consistent with turbulence promoting the mixing between ocean surface and cloud base. Considering the influence of smoke significantly improved the correlation with Nd for two biomass burning tracer species in the study region, specifically oxalate and iron. When binning by in-cloud height, non-sea salt sulfate and sodium correlated best with Nd at cloud top, whereas iron and oxalate correlate best with Nd at cloud base.

scholarly journals Investigation of peloid from some lake in Zavkhan province

2018 ◽  
pp. 26-32
Author(s):  
Bayaraa B ◽  
Nomintsetseg B ◽  
Ganzaya G ◽  
Ankhzaya A` ◽  
Dolmaa G
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Bottom Sediment ◽  
Humic Substances ◽  
Polar Solvents ◽  
Total Extract ◽  
X Ray ◽  
Sea Bottom ◽  
Physicochemical Methods

The purpose of study was to determine chemical composition and organic matter of peloids from lakes located named as Tsagaan Lake and toirom of Tsagaan Lake in Zavkhan province by chemical and modern physicochemical methods, including (X-ray, IR and ICP-AES). From the result, peloid from Tsagaan Lake was identified that peloid belongs to silt sulphide muddy type whereas characterization of peloid from toirom of Tsagaan Lake was almost similar with peloid knoll, but it is not possible to use the treatment and peloid solution was 5 to 6 times higher than the category of much pollutant. 45 elements determined in two Lakes peloid´s samples. The content of some macro elements (Al, Fe, Mg, P, Ba and K) were lower than Clark elements of sea bottom sediment whereas the content of Na, Ba were higher than it. Lipid and carbohydrate contains were between 0.03 - 0.29%, and 0.005-0.04%. Humic substances content varied between 0.19 % - 0.71% in these peloids. Organic matters, which are free, associated with minerals and absorbed extracted in peloids using non-polar and polar solvents; yield of total extract in peloids were 0.2781%, 0.4161% respectively. Завхан аймгийн зарим нуурын шаврын судалгааны дүнгээс Хураангуй: Завхан аймгийн Цагаан нуурын тойром, Цагаан нуурын шавар, шаврын уусмалын ерөнхий үзүүлэлтүүд, органик бодисын агуулга, эрдэс, элементийн найрлагыгхимийн болон физик-химийн орчин үеийн судалгааны аргуудыг (ИК, РД, ICP-AES) ашиглан судлахад Цагаан нуурын шавар нь хүхэртустөрөгчит лаг шаврын ангилалын үзүүлэлттэй, Цагаан нуурын тойрмын шавар нь бялхамал шаврын үзүүлэлтүүдтэй ойролцоо байгаа ч эмчилгээнд хэрэглэх боломжгүй бөгөөд шаврын уусмал нь маш их бохирдолттой гэсэн ангилалаас 5-6 дахин их байгааг илрүүлэн тогтоов. Судалгаанд хамрагдсан 2 нуурын эмчилгээний шаварт нийт 45 элемент бүртгэгдсэнээс зарим макроэлементүүд (Al, Fe, Mg, P, Ba, K) далайн ёроолын тунамал хурдасын кларк хэмжээнээс бага, харин Na, Ba агуулга их байна. Цагаан нуурын шаварт гумины бодис 0.71 %, липид 0.03 %, нүүрс-ус 0.04 %, Цагаан нуурын тойрмын шаварт гумины бодис 0.19 %, липид 0.29 %, нүүрс-ус 0.005 % тус тус агуулгатай байна. Шаврын чөлөөт органик нэгдэл, эрдэстэй холбогдсон болон тэдгээрт шингээгдсэн органик бодисын нийлбэр агуулга Цагаан нуурын шаварт 0.2781 %, Цагаан нуурын тойрмын шаварт 0.4161 % байгааг судлан тогтоов. Түлхүүр үг: пелоид, гумины бодис, липид, бальнеологи

scholarly journals Improving the characterization of dissolved organic carbon in cloud water: Amino acids and their impact on the oxidant capacity

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Angelica Bianco ◽  
Guillaume Voyard ◽  
Laurent Deguillaume ◽  
Gilles Mailhot ◽  
Marcello Brigante
Keyword(s):  
Amino Acids ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Cloud Water

Characterization of Organic Matter in PM2.5 sampled on different filter by FITR and Electrospray ATR-FTIR

2021 ◽  
Author(s):  
Andrea Arangio ◽  
Amir Yazdani ◽  
Matteo Reggente ◽  
Claudia Zellweger-Fasi ◽  
Athanasios Nenes ◽  
...  
Keyword(s):  
Organic Matter ◽  
Fourier Transform ◽  
Chemical Composition ◽  
Surrounding Medium ◽  
Chemical Characterization ◽  
Fourier Transform Infrared ◽  
Incident Radiation ◽  
Atmospheric Particulate Matter ◽  
Transmission Mode

&lt;p&gt;Atmospheric particulate matter (PM) is composed of up to 90% of organic matter [1]. Chemical characterization of PM organic fraction can be achieved by transmission mode Fourier transform infrared spectroscopy (TM-FTIR). FTIR is fast and inexpensive for qualitative and quantitative analysis of functional groups (FG) [2]. However, the applicability of TM-FTIR strongly depends on the filter support properties onto which particles are collected. Indeed, Teflon filters may negatively affect the effectiveness of the technique because of the symmetric and asymmetric stretching of -CF2 bonds covering the spectral range of&amp;#160; 1100-1300 cm&lt;sup&gt;-1&lt;/sup&gt;, and the polymeric matrix causes diffusion of the incident radiation leading to baseline distortion in the 1500 - 4000 cm&lt;sup&gt;-1&lt;/sup&gt; region. Additionally, high loads of NH&lt;sub&gt;4&lt;/sub&gt;NO&lt;sub&gt;3 &lt;/sub&gt;cause the &amp;#8220;Christiansen peak effects&amp;#8221; - refractive index of the samples matches that of the surrounding medium - which produces an anomalous transmittance of radiation and a distorted absorbance [3]. Moreover, FTIR analysis cannot be directly applied on quartz filters (QF) due to their strong IR absorbance that prevents the radiation source to cross the filter.&amp;#160;&lt;/p&gt;&lt;p&gt;In order to overcome these drawbacks, we applied attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopy on solvent extracts of PM&lt;sub&gt;2.5&lt;/sub&gt; directly transferred onto a ZnSe crystall employing electrospray (ES). The ES-ATR-FTIR technique is characterized by a rapid solvent evaporation favouring the formation of thin films [4]. This enables us to improve the sensitivity and efficiency of the technique obtaining transmission-mode-like spectra of methanol extracted samples characterized by a high solvent/analyte ratio.&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;In this work, 403 samples of atmospheric PM&lt;sub&gt;2.5 &lt;/sub&gt;collected in Z&amp;#252;rich-Kaserne site from March 2016 to April 2017 are analyzed using TM-FTIR. The spectra were initially employed to evaluate the FGs composition of PM&lt;sub&gt;2.5&lt;/sub&gt; and the fraction of organic matter (OM) which resulted into an average of 40-50%. Successively, PM&lt;sub&gt;2.5&lt;/sub&gt; co-sampled on QF filters from Z&amp;#252;rich-Kaserne site were analysed by ES-ATR-FTIR. The technique was performed on a reduced number of representative samples selected from clusters with different FGs profile. The ES-ATR-FTIR spectra of ambient samples were collected and compared to those obtained by TM-FTIR on Teflon filters. While the OM/OC for each cluster is comparable to the OM/OC estimated from the Teflon filters, both OM and OC estimes of ATR mode are 40% of the transmission estimates due to the extraction limitation.&lt;/p&gt;&lt;p&gt;Further insights on the PM chemical composition are explored by appying non-negative matrix factorization (NMF) to ATR spectra.&lt;span&gt;&amp;#160;&lt;/span&gt;Throught NMF analysis, inorganic and organic spectral features and they relative contributions are identified and quantified over the year and indicating the contribution of biogenic sources in summer and residential wood burning in winter.&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;In conclusion, ES-ATR-FTIR enables the acquisition of spectra of PM&lt;sub&gt;2.5&lt;/sub&gt; samples without interference of supporting material. Additionally, further insights on the PM chemical composition due to extended accessible spectral region are discussed.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Bibliography&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] J. L. Jimenez et al.&lt;em&gt;, Sci.&lt;/em&gt;, 326, 5959,1525-1529&lt;/p&gt;&lt;p&gt;[2] S. Takahama. et al., &lt;em&gt;Aer. Sci. Tech. &lt;/em&gt;47, 310, 325, 2013.&lt;/p&gt;&lt;p&gt;[3] M. A. Jarzembski. et al., &lt;em&gt;Appl. Opt.&lt;/em&gt;, 42, 2003.&lt;/p&gt;&lt;p&gt;[4] A. M. Arangio et al., &lt;em&gt;App. Spec&lt;/em&gt;., 73, &amp;#160;6, 638-65.&lt;/p&gt;

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