Molecular Speciation of Size Fractionated Particulate Water-Soluble Organic Carbon by Two-Dimensional Nuclear Magnetic Resonance (NMR) Spectroscopy

Particulate matter is associated with increased morbidity and mortality; its effects depend on particle size and chemical content. It is important to understand the composition and resultant toxicological profile of particulate organic compounds, the largest and most complex fraction of particulate matter. The objective of the study was to delineate the nuclear magnetic resonance (NMR) spectral fingerprint of the biologically relevant water-soluble organic carbon (WSOC) fraction of size fractionated urban aerosol. A combination of one and two-dimensional NMR spectroscopy methods was used. The size distribution of particle mass, water-soluble extract, non-exchangeable organic hydrogen functional types and specific biomarkers such as levoglucosan, methane sulfonate, ammonium and saccharides indicated the contribution of fresh and aged wood burning emissions, anthropogenic and biogenic secondary aerosol for fine particles as well as primary traffic exhausts and pollen for large particles. Humic-like macromolecules in the fine particle size range included branched carbon structures containing aromatic, olefinic, keto and nitrile groups and terminal carboxylic and hydroxyl groups such as terpenoid-like polycarboxylic acids and polyols. Our study show that 2D-NMR spectroscopy can be applied to study the chemical composition of size fractionated aerosol

Trends of Ground-Level Ozone in New York City Area during 2007–2017

The spatiotemporal patterns of ground level ozone (O3) concentrations in the New York City (NYC) metropolitan region for the 2007–2017 period were examined conjointly with local emissions of O3 precursors and the frequency of wildfires. Daily 8-h and 1-h O3 and nitric oxide (NO) concentrations were retrieved from the US Environmental Protection Agency (EPA) Air Data. Annual emission inventories for 2008 and 2017 were acquired from EPA National Emissions Inventory (NEI). The number and area burnt by natural and human-ignited wildfires were acquired from the National Interagency Fire Center (NIFC). The highest daily 8-h max O3 concentrations varied from 90 to 111 parts per billion volume (ppbv) with the highest concentrations measured perimetrically to NYC urban agglomeration. The monthly 8-h max O3 levels have been declining for most of the peri-urban sites but increasing (from +0.18 to +1.39 ppbv/year) for sites within the urban agglomeration. Slightly higher O3 concentrations were measured during weekend than those measured during the weekdays in urban sites probably due to reduced O3 titration by NO. Significant reductions of locally emitted anthropogenic nitrogen oxides (NOx) and volatile organic compounds (VOCs) may have triggered the transition from VOC-limited to NOX-limited conditions, with downwind VOCs sources being critically important. Strong correlations between the monthly 8-h max O3 concentrations and wildfires in Eastern US were computed. More and destructive wildfires in the region were ignited by lightning for years with moderate and strong La Niña conditions. These findings indicate that climate change may counterbalance current and future gains on O3 precursor’s reductions by amending the VOCs-to-NOx balance

Trends of Ground-Level Ozone in New York City Area during 2007–2017

The spatiotemporal patterns of ground level ozone (O3) concentrations in the New York City (NYC) metropolitan region for the 2007–2017 period were examined conjointly with local emissions of O3 precursors and the frequency of wildfires. Daily 8-h and 1-h O3 and nitric oxide (NO) concentrations were retrieved from the US Environmental Protection Agency (EPA) Air Data. Annual emission inventories for 2008 and 2017 were acquired from EPA National Emissions Inventory (NEI). The number and area burnt by natural and human-ignited wildfires were acquired from the National Interagency Fire Center (NIFC). The highest daily 8-h max O3 concentrations varied from 90 to 111 parts per billion volume (ppbv) with the highest concentrations measured perimetrically to NYC urban agglomeration. The monthly 8-h max O3 levels have been declining for most of the peri-urban sites but increasing (from +0.18 to +1.39 ppbv/year) for sites within the urban agglomeration. Slightly higher O3 concentrations were measured during weekend than those measured during the weekdays in urban sites probably due to reduced O3 titration by NO. Significant reductions of locally emitted anthropogenic nitrogen oxides (NOx) and volatile organic compounds (VOCs) may have triggered the transition from VOC-limited to NOX-limited conditions, with downwind VOCs sources being critically important. Strong correlations between the monthly 8-h max O3 concentrations and wildfires in Eastern US were computed. More and destructive wildfires in the region were ignited by lightning for years with moderate and strong La Niña conditions. These findings indicate that climate change may counterbalance current and future gains on O3 precursor’s reductions by amending the VOCs-to-NOx balance

In-situ study of the mechanism of secondary aerosol formation via the photo-oxidation of monoterpenes

Η μελέτη της πορείας των πτητικών υδρογονανθράκων αποτελεί αντικείμενο έντονου ενδιαφέροντος εξαιτίας της συνειδφοράς τους στην οξειδωτική ικανότητα της ατμόσφαιρας και στην παραγωγή νέων σωματιδίων. Η φωτο-οξείδωση των πτητικών υδρογονανθράκων με τις ρίζες ΟΗ και το όζον λαμβάνει χώρα κατά την διάρκεια της ηλιοφάνειας ενώ κατά την διάρκεια της νύχτας, η ύπαρξη των ΝΟ3 ριζών αποτελεί την κύρια αιτία. Παρά την σπουδαιότητα τους, οι εργασίες που πραγματοποιήθηκαν ως τώρα περιορίζονται στην μελέτη ορισμένων παραμέτρων υπό συνθήκες ατμοσφαιρικής προρομοίωσης, ενώ δεν υπάρχουν ολοκληρωμένες εργασίες σε πραγματικές συνθήκες. Για την κατανόηση της σπουδαιότητας των δασικών ατμοσφαιρικών συστημάτων μελετήθηκε η σύσταση των οργανικών αερολύματων σε αστική, μη-αστική και δασική περιοχή όπου παρατηρήθηκαν έντονες διαφοροποιήσεις. Οι ανρωπογενείς δραστηριότητες εμπλουτίζουν τα μικρότερα σωματίδια σε αστικές περιοχές, με σημαντική συνεισφορά του καπνού των τσιγάρων ενώ τα μεγαλύτερα σωματίδια προέρχονται από άμεσες εκπομπές από την εφυμενίδα των φύλλων των ανώτερων φυτών. Αντιθέτως, η συσσώρευση της οργανικής ύλης στα σωματίδια με διάμετρο από 1.5 ως 7.2 μm υποδεικνύει ότι η σύσταση των οργανικών αερολυμάτων σε μη-αστικές περιοχές επηρεάζεται κυρίως από την προέλευση της αέριας μάζας. Τέλος, μεγάλες διαφοροποιήσεις παρατηρήθηκαν στην σύσταση των οργανικών αερολυμάτων σε δασική περιοχή, όπου πιστοποιήθηκε για πρώτη φορά σε πραγματικές συνθήκες, η παραγωγή νέων αερολυμάτων και κυρίως η χιμική σύσταση τους. Για την μελέτη της παραγωγής των νέων αερολυμάτων σε δασικές περιοχές πραγματοποιήθηκαν δειγματοληψίες σε δύο δάση. Ο προσδιορισμός της σύστασης του οργανικού κλασματος σε αέρια και σωματιδιακή φάση είχε ως αποτέλεσμα την ανίχνευση οργανικών ενώσεων που προέρχονται από την φωτο-οξείδωση των μονοτερπενίων με την βοήθεια της φασματοσκοπίας μάζας. Πιό συγκεκριμένα, επιβεβαιώθηκε η ύπαρξη των δύο ισομερών μορφών (cis- και trans-) του 2,2-διμέθυλ-3-ακέτυλ-κυκλοβουτάνο-οξικού οξέος (πινονικό οξύ), του cis-2,2-διμέθυλ-3-καρβόξυ-κυκλοβουτάνο-οξικού οξέος (πινικό οξύ) και της 2,2-διμέθυλ-3-ακέτυλ-κυκλοβουτάνο-ακεταλδεΰδης (πινοναλδεΰδη) που προέρχονται από την φωτοοξείδωση του α-πινενίου ενώ ανιχνεύθηκε και η 6,6-διμέθυλ-δικυκλο[3.1.1]-επταν-2-όνη (νοπινόνη) που παράγεται από την φωτο-οξείδωση του β-πινενίου. Οι συγκεντρώσεις του πινονικού οξέος στην σωματιδιακή φάση και ο αριθμός των σωματιδίων αυξάνονατι με ταυτόχρονη μείωση της διαμέτρου των παραγώμενων σωματιδίων υποδηλώνοντας την συμμετοχη του οξέος στην παραγωγή των νέων σωματιδίων. Οι συγκεντρώσεις του πινονικού οξέος στην αέρια φάση αυξάνονται κατά τις μεσημεριανές ώρες όπου η φωτοχημεία είναι έντονη αλλά η δημιουργία νέων σωματιδίων δεν είναι εφικτή λόγω υψηλής θερμοκρασίας. Το πινικό οξύ παρουσιάζει αντίθετη ημερήσια κατανομή σε σύγκριση με το πινονικό οξύ υποδεικνύοντας ότι υποβοηθά την συμπύκνωση των πυρήνων που έχουν δημιουργηθεί. Αντίθετα, η πινοναλδεΰδη και η νοπινόνη δεν συνιστούν πυρήνες για δημιουργία νέων σωματιδίων αλλά συνεισφέρουν στην συσσωμάτωση τους δημιουργόντας μεγαλύτερα σωματίδια. Ο λόγος κατανομής των ενώσεων ανάμεσα στις δύο φάσεις (Κom) για το cis-πινονικό οξύ είναι 0.188, για το trans-πινονικό οξύ είναι 0.118, για το cis-πινικό οξύ είναι 0.170, για την πινοναλδεΰδη είναι 0.075 και για την νοπινόνη είναι 0.032 υποδεικνύοντας επίσης την συμμετοχή των καρβοξυλικών ενώσεων στον σχηματισμό νέων σωματιδίων.Large amounts of biogenic, compared to anthropic, non-methane hydrocarbons (NMHCs) are emitted into the atmosphere from a variety of sources. Estimates of biogenic NMHCs emission have been of interest the last two decades because of their potential role in shaping regional photochemical oxidant and aerosol formation and thus balancing global tropospheric chemistry. The atmospheric chemistry of biogenic NMHCs is initiated by the highly reactive O3 and the ubiquitous, transient OH and NO3 radicals. There are few data available concerning the products of these reactions and the reaction mechanisms under simulated atmospheric conditions and even fewer under real atmospheric conditions. In order to study the importance of forested areas and to understand the local chemistry we investigated: a) the composition of the size distributed organic compounds in an urban, non-urban and a forested area b) the secondary organic aerosols formed in the atmosphere by the condensation of low vapor pressure products of isoprene and terpenes photo-oxidation such as α- and β- pinene c) the chemical structure of these products and their ability in new particle formation and d) the gas-to-particle partitioning of secondary organic compounds. The composition of particle-associated organic compounds in urban, non-urban and forest ares was studied. Significant differences were observed among these areas. Anthropogenic activities as well as environmental tobacco smoke are the major sources of finer aerosol in urban areas while direct emissions of leaves epicuticular waxes enrich coarser particles. On the other hand, non-urban otganic mass is concentrated in particles having diameter from 1.5 to 7.2 μm as a consequence of condensation processes. Air masses origin was determined as the most important factor controlling the composition of non-urban areas. In forested areas, aerosol chemical composition and chemical properties are extensively controlled by the photo-oxidation of α- and β- pinene. In order to study the mechanism of aerosol formation in-situ, intensive sampling for both gas and particulate phases were performed inside the forest canopy at two different forests. The identification of the two isomers of 2,2-dimethyl-3-acetyl-cyclobutane-ethanoic acid (pinonic acid), cis-2,2-dimethyl-3-carboxyl-cyclobutane-ethanoic acid (cis-pinic acid) and 2,2-dimethyl-3-acetyl-cyclobutane-acetaldehyde (pinonaldehyde) (photo-oxidation products of a α-pinene) and 6,6-dimethyl-bicyclo[3,1,1]-heptan-2-one (nopinone;photo-oxidation product of β-pinene) has been done by means of their mass spectra. The diurnal distribution pattern of particulate cis- and trans-pinonic acid follows exactly the same pattern as the corresponding variation of Aitken nuclei concentration, supporting that hese rwo acids are chemically coupled with new particle formes over the forests. Although, pinic acid is a dicarboxylic acid, its diurnal pattern follows an unclear pattern. Since, the mechanism is not clear, we can assume that other oxidants such as HO2 and NOx as well as temperature and humidity could influence at pinic acid formation. In addition, the presence of pinonaldehyde and nopinone, despite their high vapor pressure, in the particulate phase can be only explained by the assumption that vapor-phase products condense onto existing particles due to the formation of an intermediate external organic layer of Aitken nuclei. Gas phase concentrations of pinonic and pinic acid, pinonaldehyde and nopinone increased during daytime due to rapid photo-oxidation of α- and β-pinene. Finally, partitioning ratio (Kom) between gas and particulate phases of above compounds has been calculated (cis-pinonic acid: 0.188; trans-pinonic acid: 0.118; cis-pinic acid: 0.170; pinonaldehyde: 0.075; nonpinone: 0.032). These values verify the importance of carboxylic compounds contribution to secondary organic aerosol formation

On the Role of Atmospheric Weathering on Paint Dust Aerosol Generated by Mechanical Abrasion of TiO2 Containing Paints

In recent years, the introduction and use of new nanomaterials in construction has increased at a rapid rate. Exterior surface paints have been a product that have had these nanomaterials added to them. In this study, the effects of natural weathering and exposure to atmospheric agents was examined to determine the detrimental effects on outdoor paint that has been created with nanomaterials. Data collected over the course of the yearlong study indicate that the nanoparticles of the titanium dioxide were eliminated rapidly. Further testing indicated that various elements of weathering were affecting the physical integrity of the paint. The weathering agents that appeared to have the greatest effect on the samples were acid deposition and total precipitation. There was a strong association between carbon monoxide and the effects on the panels. These results can lead to new plans for assessments involving the synergistic effects of all weathering agents