Atmospheric Water Soluble Organic Nitrogen (WSON) over marine environments: A global perspective

To obtain a comprehensive picture of the spatial distribution of water-soluble organic nitrogen (WSON) in marine aerosols, samples were collected during research cruises in the tropical and southern Atlantic Ocean and also in the southern Indian Ocean (Amsterdam Island) for a 1-year period (2005). Samples were analyzed for both organic and inorganic forms of nitrogen, and the factors controlling their levels were examined. Fine-mode WSON was found to play a significant role in the remote marine atmosphere with enhanced biogenic activity, with concentrations of WSON (11.3 +/- 3.3 nmol N m(-3)) accounting for about 84% of the total dissolved nitrogen (TDN). Such concentrations are similar to those observed in the polluted marine atmosphere of the eastern Mediterranean (11.6 +/- 14.0 nmol N m(-3)). Anthropogenic activities were found to be an important source of atmospheric WSON as evidenced by the levels in the Northern Hemisphere (NH) being 10 times higher than in the remote Southern Hemisphere (SH). Furthermore, the higher contribution of fine-mode WSON to TDN (51 %) in the SH, compared to the NH (13 %), underlines the important role of organic nitrogen in remote marine areas. Finally, there was a strong association of WSON with dust in coarse-mode aerosols in the NH

Expiratory Aerosol pH: The Overlooked Driver of Airborne Virus Inactivation

Respiratory viruses, including influenza virus and SARS-CoV-2, are transmitted by the airborne route. Air filtration and ventilation mechanically reduce the concentration of airborne viruses and are necessary tools for disease mitigation. However, they ignore the potential impact of the chemical environment surrounding aerosolized viruses, which determines the aerosol pH. Atmospheric aerosol gravitates toward acidic pH, and enveloped viruses are prone to inactivation at strong acidity levels. Yet, the acidity of expiratory aerosol particles and its effect on airborne virus persistence have not been examined. Here, we combine pH-dependent inactivation rates of influenza A virus (IAV) and SARS-CoV-2 with microphysical properties of respiratory fluids using a biophysical aerosol model. We find that particles exhaled into indoor air (with relative humidity ≥ 50%) become mildly acidic (pH ∼ 4), rapidly inactivating IAV within minutes, whereas SARS-CoV-2 requires days. If indoor air is enriched with nonhazardous levels of nitric acid, aerosol pH drops by up to 2 units, decreasing 99%-inactivation times for both viruses in small aerosol particles to below 30 s. Conversely, unintentional removal of volatile acids from indoor air may elevate pH and prolong airborne virus persistence. The overlooked role of aerosol acidity has profound implications for virus transmission and mitigation strategies

Inactivation mechanisms of influenza A virus under pH conditions encountered in aerosol particles as revealed by whole-virus HDX-MS

Multiple respiratory viruses, including influenza A virus (IAV), can be transmitted via expiratory aerosol particles, and aerosol pH was recently identified as a major factor influencing airborne virus infectivity. Indoors, small exhaled aerosols undergo rapid acidification to pH ~4. IAV is known to be sensitive to mildly acidic conditions encountered within host endosomes; however, it is unknown whether the same mechanisms could mediate viral inactivation within the more acidic aerosol micro-environment. Here, we identified that transient exposure to pH 4 caused IAV inactivation by a two-stage process, with an initial sharp decline in infectious titers mainly attributed to premature attainment of the post-fusion conformation of viral protein haemagglutinin (HA). Protein changes were observed by hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) as early as 10 s post-exposure to acidic conditions. Our HDX-MS data are in agreement with other more labor-intensive structural analysis techniques, such as X-ray crystallography, highlighting the ease and usefulness of whole-virus HDX-MS for multiplexed protein analyses, even within enveloped viruses such as IAV. Additionally, virion integrity was partially but irreversibly affected by acidic conditions, with a progressive unfolding of the internal matrix protein 1 (M1) that aligned with a more gradual decline in viral infectivity with time. In contrast, no acid-mediated changes to the genome or lipid envelope were detected. Improved understanding of respiratory virus fate within exhaled aerosols constitutes a global public health priority, and information gained here could aid the development of novel strategies to control the airborne persistence of seasonal and/or pandemic influenza in the future. IMPORTANCE: It is well established that COVID-19, influenza, and many other respiratory diseases can be transmitted by the inhalation of aerosolized viruses. Many studies have shown that the survival time of these airborne viruses is limited, but it remains an open question as to what drives their infectivity loss. Here, we address this question for influenza A virus by investigating structural protein changes incurred by the virus under conditions relevant to respiratory aerosol particles. From prior work, we know that expelled aerosols can become highly acidic due to equilibration with indoor room air, and our results indicate that two viral proteins are affected by these acidic conditions at multiple sites, leading to virus inactivation. Our findings suggest that the development of air treatments to quicken the speed of aerosol acidification would be a major strategy to control infectious bioburdens in the air

The potential impact of Saharan dust and polluted aerosols on microbial populations in the East Mediterranean Sea, an overview of a mesocosm experimental approach.

Recent estimates of nutrient budgets for the Eastern Mediterranean Sea (EMS) indicate that atmospheric aerosols play a significant role as suppliers of macro- and micro- nutrients to its Low Nutrient Low Chlorophyll water. Here we present the first mesocosm experimental study that examines the overall response of the oligotrophic EMS surface mixed layer (Cretan Sea, May 2012) to two different types of natural aerosol additions, “pure” Saharan dust (SD, 1.6 mg l-1) and mixed aerosols (A - polluted and desert origin, 1 mg l-1). We describe the rationale, the experimental set-up, the chemical characteristics of the ambient water and aerosols and the relative maximal biological impacts that resulted from the added aerosols. The two treatments, run in triplicates (3 m3 each), were compared to control-unamended runs. Leaching of approximately 2.1-2.8 and 2.2-3.7 nmol PO4 and 20-26 and 53-55 nmol NOx was measured per each milligram of SD and A, respectively, representing an addition of approximately 30% of the ambient phosphate concentrations. The nitrate/phosphate ratios added in the A treatment were twice than those added in the SD treatment. Both types of dry aerosols triggered a positive change (25-600% normalized per 1 mg l-1 addition) in most of the rate and state variables that were measured: bacterial abundance (BA), bacterial production (BP), Synechococcus (Syn) abundance, chlorophyll-a (chl-a), primary production (PP) and dinitrogen fixation (N2-fix), with relative changes among them following the sequence BP>PP≈N2-fix>chl-a≈BA≈Syn. Our results show that the ‘polluted’ aerosols triggered a relatively larger biological change compared to the SD amendments (per a similar amount of mass addition), especially regarding BP and PP. We speculate that despite the co-limitation of P and N in the EMS, the additional N released by the A treatment may have triggered the relatively larger response in most of the rate and state variables as compared to SD. An implication of our study is that a warmer atmosphere in the future may increase dust emissions and influence the intensity and length of the already well stratified water column in the EMS and hence the impact of the aerosols as a significant external source of new nutrients

Organic nitrogen in atmosphere: chemical characterization, sources and the role in the biochemical cycle of nitrogen

The chemistry and the sources of water-soluble organic nitrogenous compounds have been poorly studied, although are considered as an important piece of biogeochemical cycle of nitrogen. Many organic nitrogenous compounds play an important role to the oxidation capacity of the atmosphere such as peroxyacetyl nitrate (PAN) and related alkyl nitrates (RONO2). Nitro-PAH is subject to research attention because of their toxicity while alkyl amines are precursor for SOA formation. Additionally urea and amino acids are considered particularly bioavailable to aquatic ecosystems, enhancing the importance of atmospheric deposition of WSON to marine ecosystem. Goal of this study is to understand the role of WSON in the atmospheric nitrogen cycle, including the sources and the chemical composition of WSON fraction. During this study, size segregated atmospheric particles have been collected from North and South Hemisphere. Comparing the concentration levels of atmospheric WSON in fine mode in both Hemispheres, concluded that ten-fold higher was the estimated concentration in N. Hemisphere enhanced the important role of anthropogenic origin of organic nitrogenous compounds. On the other hand in remote marine areas in S. Hemisphere much substantial was the role of atmospheric WSON because the absence of Inorganic Nitrogen increases the contribution of WSON to TDN. Additionally, important role to the atmospheric concentration levels of WSON play the marine bloom areas since the intense biological activity produce organic nitrogenous compounds. This natural source of WSON seems to be the same order with anthropogenic activities in fine particles. Another important source of WSON particularly in coarse atmospheric particles is the dust. It was estimated that approximately 2.9±1.0 Tg Ν yr⁻¹ of organic nitrogenous compounds were transferred from the Sahara desert. This quantity is comparable with the Inorganic nitrogen that produced naturally by lightning. Atmospheric deposition of water-soluble N-containing organic compounds has been measured in the Eastern Mediterranean during a four years period. Almost 23% and 38.6% of TDN deposition flux in the area attributed to WSON for wet and dry deposition respectively. The concentrations of WSON are associated strongly with the meteorological patterns encountered in the area. Furthermore, the estimated fluxes of WSON depend not only on the amount of rain but also on the air mass origin since the influence of anthropogenic emissions on WSON levels (E/NE winds) could be of comparable importance with the natural sources i.e dust (SW/S winds). Additionally, the fraction of WSON can also participate in the neutralisation of the atmospheric acidity. Atmospheric deposition of WSON was mainly governed by dry deposition as 78% of total WSON is deposited through this pathway. Thus during summer when the water column stratification prevails, the impact of atmospheric deposition to the marine environment is maximized. Finally, 20-30% of the new production due to atmospheric nitrogen deposition can be attributed to water-soluble organic N-containing compounds in E. Mediterranean basin. Krom et al. (2004) estimated that 70% of the nitrogen budget in the Eastern Mediterranean is due to atmospheric deposition of DIN. As WSON can provide nitrogen in bioavailable form, atmospheric deposition of both DIN and WSON can account for up to 90% of the nitrogen budget in areas far from the continental slope highlighting the important role of atmospheric deposition in the biogeochemical nitrogen cycle in the Eastern Mediterranean. Among organic nitrogenous compounds analyzed in the E. Mediterranean were urea, amines (dimethylamine & trimethylamine) and free amino acids. Furthermore, the presence of urea in coarse mode attributed to dust and the average concentration was estimated 1.0±2.0 nmol N m⁻³. The average concentration of urea in fine mode was estimated 2.2±3.0 nmol N m⁻³, while it was found statistical significant correlation with ammonium ions, indicating same sources as both are end products of mammals metabolism. The average concentration of free amino acids in fine atmospheric particles in E. Mediterranean was estimated 0.8±1.3 nmol N m⁻³ and the average percentage contribution to WSON was 3.8%, while the most abundant free amino acid was glycine with 66% percentage contribution to total free amino nitrogen. Only dimethylamine was detected with average concentration in fine mode 0.20±0.81 nmol N m⁻³ and average percentage contribution to WSON 0.91%.Είναι γεγονός ότι υπάρχουν αρκετές μελέτες που αφορούν το γίγνεσθαι του ανόργανου αζώτου και τον ρόλο του στο ατμοσφαιρικό κύκλο του αζώτου. Αντίθετα για το οργανικό άζωτο οι διαθέσιμες μελέτες είναι ελάχιστες, παρόλο που έχει αναγνωρισθεί ως ένα σημαντικό κομμάτι του κύκλου του αζώτου στην ατμόσφαιρα. Έτσι πολλές οργανικές αζωτούχες ενώσεις θεωρούνται ρυπαντές όπως είναι τα περοξυακετυλο νιτρίλια και οι νιτρο-PAH, επίσης αζωτούχες ενώσεις όπως οι αμίνες θεωρούνται πρόδρομες ενώσεις για το σχηματισμό δευτερογενών σωματιδίων, ενώ ενώσεις όπως η ουρία και τα αμινοξέα αποτελούν άμεσα θρεπτικά συστατικά κατά την εναπόθεση τους σε θαλάσσια οικοσυστήματα. Αντικείμενο της παρούσας μελέτης είναι η κατανόηση των χημικών και φυσικών διεργασιών που ελέγχουν το γίγνεσθαι των υδατοδιαλυτών οργανικών αζωτούχων ενώσεων (WSON) στο ατμοσφαιρικό περιβάλλον, έχοντας ως απώτερο στόχο να καθοριστούν οι πηγές των ενώσεων αυτών στην ατμόσφαιρα αλλά και να διερευνηθούν οι πιθανές χημικές μορφές τους. Ειδικότερα, η παρούσα μελέτη διαπραγματεύεται το γίγνεσθαι των υδατοδιαλυτών οργανικών αζωτούχων ενώσεων στην ατμόσφαιρα, μελετώντας την συμπεριφορά τους στα αδρά και λεπτά σωματίδια που εκλύονται από περιοχές με διαφορετικά χαρακτηριστικά τόσο του Βόρειου όσο και του Νότιου Ημισφαιρίου. Συγκρίνοντας τα επίπεδα συγκέντρωσης του WSON που προσδιορίστηκαν στα λεπτά σωματίδια βρέθηκε ότι στις περιοχές του Β. Ημισφαιρίου (Α. Μεσόγειος & Τροπικός Ατλαντικός Ωκεανός) τα επίπεδα συγκέντρωσης του ήταν περίπου 10 φορές υψηλότερα συγκριτικά με τις περιοχές του Ν. Ημισφαιρίου Το γεγονός αυτό οφείλεται στην εντονότερη παρουσία των ανθρωπογενών δραστηριοτήτων οι οποίες εμπλουτίζουν την ατμόσφαιρα με ανθρωπογενούς προέλευσης οργανικές αζωτούχες ενώσεις. Παρόλα αυτά, στις απομακρυσμένες θαλάσσιες περιοχές του Νοτίου Ημισφαιρίου (K. Ν. Ατλαντικός Ωκεανός & Ινδικός Ωκεανός) το ποσοστό συμμετοχής του WSON είναι της τάξης του 40%, γεγονός που οφείλεται στην μικρότερη παρουσία του ανόργανου αζώτου, δεδομένου ότι οι περιοχές αυτές δέχονται λιγότερες επιδράσεις από ανθρωπογενείς δραστηριότητες. Επομένως σε περιοχές με τέτοια χαρακτηριστικά το WSON κατέχει καθοριστικότερο ρόλο στον βιογεωχημικό κύκλο του αζώτου. Εκτός από τις ανθρωπογενείς δραστηριότητες εξίσου σημαντική πηγή των οργανικών αζωτούχων ενώσεων είναι και οι θαλάσσιες περιοχές με άνθηση του φυτοπλαγκτού, δηλαδή περιοχές με έντονη θαλάσσια βιολογική δραστηριότητα. Η παρουσία των οργανικών αζωτούχων ενώσεων στην ατμόσφαιρα πάνω από νερά πλούσια σε θρεπτικά συστατικά, οφείλεται σε βιογενείς διεργασίες. Τα επίπεδα συγκέντρωσης του WSON στην ατμόσφαιρα τέτοιων θαλάσσιων περιοχών βρέθηκαν παρόμοια με τα επίπεδα συγκέντρωσης της Α. Μεσογείου. Επομένως μπορούμε να θεωρήσουμε εξίσου σημαντική πηγή των οργανικών αζωτούχων ενώσεων με τις ανθρωπογενείς δραστηριότητες και τους Ωκεανούς και ειδικότερα τις περιοχές με έντονη βιολογική δραστηριότητα. Σημαντική πηγή του WSON είναι η μεταφορά σκόνης, κυρίως στα αδρά σωματίδια της ατμόσφαιρας, από τις ερήμους και ειδικότερα από την έρημο της Αφρικής, μια και η υπό μελέτη περιοχή της Α. Μεσογείου δέχεται έντονα την επίδραση της. Μάλιστα σε ετήσια παγκόσμια κλίμακα η ποσότητα του WSON που μεταφέρεται από την αφρικανική σκόνη υπολογίστηκε κατά προσέγγιση ίση με 2.9±1.0 Tg Ν yr⁻¹, η οποία είναι συγκρίσιμη με την ποσότητα του ανόργανου αζώτου που παράγεται στην ατμόσφαιρα μέσω της δημιουργίας κεραυνών. Ένας από τους σημαντικότερους στόχους της μελέτης αυτής ήταν να διερευνηθεί ο ρόλος της ατμοσφαιρικής εναπόθεσης των υδατοδιαλυτών οργανικών αζωτούχων ενώσεων στα θαλάσσια οικοσυστήματα. Η εναπόθεση του WSON μελετήθηκε κατά κύριο λόγο στην περιοχή της Α. Μεσογείου για χρονικό διάστημα τεσσάρων ετών (2003-2006). Αποδείχθηκε ότι τα επίπεδα εναπόθεσης του WSON επηρεάζονται άμεσα από την μετεωρολογία της περιοχής όπως είναι το ύψος της βροχόπτωσης αλλά και η προέλευση των αέριων μαζών. Η μέση τιμή της υγρής εναπόθεσης του WSON προσδιορίστηκε ίση με 4.8 mmol/m² ενώ η μέση ετήσια ξηρή εναπόθεση του WSON ήταν 17.4 mmol/m². Κύριος μηχανισμός της ατμοσφαιρικής εναπόθεσης του WSON βρέθηκε να είναι η ξηρή εναπόθεση, η οποία μάλιστα καταλαμβάνει το 78% της συνολικής εναπόθεσης. Το γεγονός αυτό προσδίδει σημαντικό ρόλο στην ατμοσφαιρική εναπόθεση σε ένα θαλάσσιο οικοσύστημα όπως είναι εκείνο της Α. Μεσογείου δεδομένου ότι την καλοκαιρινή περίοδο η στρωματοποίηση των υδάτων δεν επιτρέπει τον εμπλουτισμό των επιφανειακών νερών με θρεπτικά συστατικά από τα βαθύτερα υδάτινα στρώματα. Επιπλέον βρέθηκε ότι το 20 με 30% της νέας παραγωγής άνθρακα του θαλάσσιου οικοσυστήματος της Α. Μεσογείου που οφείλεται στην ατμοσφαιρική εναπόθεση του αζώτου, αποδίδεται στο κλάσμα των υδατοδιαλυτών αζωτούχων οργανικών ενώσεων, αποδεικνύοντας έτσι ότι η συμμετοχή του WSON στην εναπόθεση του συνολικού αζώτου αυξάνει ακόμα περισσότερο (πάνω από 90%) την συνολική ατμοσφαιρική εναπόθεση του αζώτου στην λεκάνη της Α. Μεσογείου. Δεδομένου τον σημαντικό ρόλο των υδατοδιαλυτών οργανικών αζωτούχων ενώσεων στην χημεία της ατμόσφαιρας, στην μελέτη αυτή έγινε ένα πρώτο βήμα να ταυτοποιηθεί χημικά το κλάσμα των οργανικών αζωτούχων ενώσεων. Ανάμεσα στις οργανικές αζωτούχες ενώσεις που αναλύθηκαν σε δείγματα από την περιοχή της Α. Μεσογείου ήταν η ουρία, οι αμίνες (τριμεθυλαμίνη & διμεθυλοαμίνη) και τα α-ελεύθερα αμινοξέα. Όσον αφορά την ουρία στα λεπτά σωματίδια η συγκέντρωση της προσδιορίστηκε ίση με 2.2±3.0 nmol Ν/m³, ενώ στα αδρά βρέθηκε ίση με 1.0±2.0 nmol Ν/m³. Η παρουσία της ουρίας στα αδρά σωματίδια οφείλεται κυρίως στην μεταφορά της μέσω της σκόνης, ενώ η ουρία που υπάρχει στο λεπτό κλάσμα φαίνεται να έχει κοινές πηγές με τα αμμωνιακά ιόντα δεδομένου ότι αποτελούν κοινά τελικά προϊόντα του μεταβολισμού των θηλαστικών. Η συγκέντρωση των ελεύθερων αμινοξέων στα λεπτά σωματίδια της Α. Μεσογείου (PM1) κυμάνθηκε μεταξύ 0.01 και 7.89 nmol m⁻³, με μέση τιμή ίση με 0.8±1.3 nmol m⁻³, ενώ αποδόθηκε το 3.8% του WSON στο άζωτο των ελεύθερων α-αμινοξέων. Επικρατέστερα στο σύνολο των ελεύθερων α-αμινοξέων στην ατμόσφαιρα ήταν η γλυκίνη, η οποία λόγω του μεγάλου χρόνου ημιζωής της στην ατμόσφαιρα είναι δυνατόν να μεταφερθεί από μεγαλύτερες αποστάσεις, ενώ σημαντική πηγή της φαίνεται να είναι οι καύσεις. Η μέση συγκέντρωση της διμεθυλοαμίνης προσδιορίστηκε ίση με 0.20±0.81 nmol m⁻³ ενώ παρουσίασε διακύμανση μεταξύ των τιμών 0 και 4.96 nmol m⁻³. Η ποσοστιαία συμμετοχή της στο WSON εκτιμήθηκε ίση με 0.91%. Η παρουσία της διμεθυλοαμίνης στα λεπτά σωματίδια στην ατμόσφαιρα της Α. Μεσογείου οφείλεται κυρίως σε τοπικές αγροτικές και κτηνοτροφικές δραστηριότητες, αφού δεν δύναται να μεταφερθεί από μεγάλες αποστάσεις λόγω του μικρού χρόνου ημιζωής της

Source apportionment of atmospheric P using the Positive Matrix Factorization (PMF) model

The PMF receptor model was applied to a combined dataset using specific markers such as phospholipids and sugars together with other metals (e.g. Al, Pb, V) and ions (e.g. K+, Ca2+, SO42-, NO3-) as tracers of main aerosol sources in order to characterize the sources of P in atmospheric particles. The samples were collected from East Mediterranean; an oligotrophic region, strongly P-limited, with atmospheric nutrients deposition affecting its primary productivity. The results revealed that dominant sources of P compounds are the dust (43%) and the bioaerosols (34%). The coexistence of these sources in the spring period increased the organic P up to 53% of total P with more than a half to originate from bioaerosols. Dust is the major source of inorganic P forms with almost equal contribution to the phosphate ions and to the condensed P forms (e.g pyrophosphate or phosphorous minerals). Based on the results of source apportionment analysis and the atmospheric concentration of P species, the maximum annual deposition scaled to the East Mediterranean surface was 21.5 Gg P with almost equal deposition of org-P and phosphate ions. The soluble P content from dust aerosols is the similar magnitude of potential bioavailable organic P emitted from bioaerosols (~4 Gg P y-1), especially during the stratification period, when surface water is mostly nutrient starved. Anthropogenic pollution contributes slightly higher to organic P comparing with phosphate ions, while the latter is produced mainly secondary. Biomass burning emissions in the area are associated mainly with the more soluble P.LAP

Atmospheric phosphorus characterization by 31P-NMR during dust events and bioavailability implications

International audiencePhosphorus is a critical nutrient affecting primary productivity in large areas of oceanic oligotrophic and ultraoligotrophic ecosystems. The principal source of externally supplied inorganic-P in such ecosystems is the atmosphere with dust considered as an important source. However, recent work showed that organic-P originating from bioaerosols and dust can supply as much bioavailable P as inorganic P in dust, and is thus critical for primary productivity. The presence of organic-P in atmospheric samples is typically inferred by subtraction of the amount of inorganic phosphorus from the total amount of phosphorus. At present, there is no direct method for organic-P determination. Direct speciation methods point to important sources (e.g., phospholipids from bioaerosol), but cannot account for the total amount of P in organic from. There is a need therefore to develop a method to directly identify P that are associated with organic compounds. Nuclear magnetic resonance (31P-NMR) spectroscopy can provide such a capability, as it has proven to be a powerful analytical tool for the molecular characterization of organic-P in marine plankton, sinking particles, high molecular weight dissolved organic matter and sediment. The 31P-NMR technique, however, has never been applied to atmospheric samples and is the focus of this study. Here we analyze Total Suspended atmospheric Particles (TSP) collected during dust events (n=5) in the eastern Mediterranean by using a high-volume air sampler. These particles were then analyzed using magic angle spinning solid-state 31P-NMR. The results showed the typical functional groups in P speciation which were: orthophosphate and monophosphate esters sharing the same chemical shift (H3PO4 and RH2-PO4), phosphate diesters (R1R2 HPO4) and pyrophosphate (H4P2O7). No phosphonates were detected (C-P bond) in TSP samples. Monophosphate esters and diesters are mainly found in nucleotides and their derivatives (e.g., DNA, RNA, AMP, ADP, and ATP), phospholipids and flame retardants (OPEs), and as such they constitute the majority of atmospheric organic-P. The above-mentioned P-organic compounds have C-O-P bonds therefore they are easily hydrolysable in the marine environment by the alkaline phosphatase enzyme providing an important source of P in aquatic ecosystems. Finally, the results showed that the amount of organic-P estimated colorimetrically is about equal to that estimated by 31P NMR indicating that the latter technique can be successfully employed in atmospheric studies for P speciation

Spatial and temporal patterns of organophosphate Esters flame retardants and plasticizers in airborne particles over the Mediterranean sea

International audienceWe studied the co-occurrence of OPEs and other constituents in atmospheric particles at the two edges of the Mediterranean Sea, under the influence of the transport of polluted air from Europe and dust from the Sahara. The highest OPE concentrations were observed during the summer period in the East Mediterranean and in spring for the NW Mediterranean. The total average atmospheric concentration of Σ6OPEs in the NW Mediterranean was 2103 ± 2020 pg m−3 (n = 23) with EHDPP and TCPP to be the predominant OPEs, accounting on average for 46% and 37% of the total Ʃ6OPEs concentrations, respectively. The average concentration of Σ6OPEs in East Mediterranean was 156.4 ± 170.3 pg m−3 (n = 67) with TCPP showing the highest concentration (116.1 ± 92.8 pg m−3), followed by TCEP (67.5 ± 55.8 pg m−3). In both areas, OPEs were mostly associated with fossil fuel combustion and road traffic, while the air masses from Saharan desert influenced the concentration of EHDPP, TCEP in NW Mediterranean and the TCEP concentration levels in the East Mediterranean. The total annual deposition of reported OPEs to the Mediterranean basin was estimated to be 584 tonnes, accounting for about 8.5% of the total deposited anthropogenic phosphorus

Bioaerosols and dust are the dominant sources of organic P in atmospheric particles

Several studies assessed the impact of inorganic P in fertilizing oligotrophic areas, however, the importance of organic P in such fertilization processes received far less attention. In this study, the amount and origin of organic P delivered to the eastern Mediterranean Sea were characterized in atmospheric particles using the positive matrix factorization model (PMF). Phospholipids together with other chemical compounds (sugars, metals) were used as tracers in PMF. The model revealed that dominant sources of organic P are bioaerosols and dust. The amount of organic P from bioaerosols (similar to 4 Gg P y(-1)) is similar to the amount of soluble inorganic P originating from dust aerosols; this is especially true during highly stratified periods when surface waters are strongly P-limited. The deposition of organic P from bioaerosols can constitute a considerable flux of bioavailable P-even during periods of dust episodes, implying that airborne biological particles can potentially fertilize marine ecosystems.LAP