Synthesis and characterisation of peroxypinic acids as proxies for highly oxygenated molecules (HOMs) in secondary organic aerosol

Steimer, SS; Delvaux, A; Campbell, SJ; Gallimore, PJ; Grice, P; Howe, DJ; Pitton, D; Claeys, M; Hoffmann, T; Kalberer, M
2018 | Atmos. Chem. Phys. | 18 (15) (10973-10983)
air pollution , alpha-pinene , gas-phase , hplc/ms(/ms) , liquid chromatography , mass spectrometry , nmr , oxidative stress , ozonolysis , peroxides , peroxycarboxylic acids , tropospheric degradation
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Peroxy acids were recently found to be involved in new particle formation in the atmosphere and could also substantially contribute towards particle toxicity. However, a lack of suitable analytical methods for the detection and characterisation of peroxy acids in the particle phase is currently hindering the quantitative investigation of their contribution to these important atmospheric processes. Further development of appropriate techniques and relevant standards is therefore urgently needed. In this study, we synthesised three peroxypinic acids, developed a liquid chromatography separation method and characterised them with tandem mass spectrometry. The observed fragmentation patterns clearly distinguish the different peroxypinic acids from both the acid and each other, showing several neutral losses previously already observed for other peroxy acids. Both monoperoxypinic acids were found to be present in secondary organic aerosol generated from ozonolysis of alpha-pinene in laboratory experiments. The yield of monoperoxypinic acid formation was not influenced by humidity. Monoperoxypinic acid quickly degrades on the filter, with about 60% lost within the first 5 h. This fast degradation shows that time delays in traditional off-line analysis will likely lead to severe underestimates of peroxy compound concentrations in ambient particles.

Exploring the potential of nano-Köhler theory to describe the growth of atmospheric molecular clusters by organic vapors using cluster kinetics simulations

Kontkanen, J.; Olenius, T.; Kulmala, M.; Riipinen, I.
2018 | Atmos. Chem. Phys. | 18 (13733-13754)

How much of the global aerosol optical depth is found in the boundary layer and free troposphere?

Bourgeois, Q; Ekman, AML; Renard, JB; Krejci, R; Devasthale, A; Bender, FAM; Riipinen, I; Berthet, G; Tackett, JL
2018 | Atmos. Chem. Phys. | 18 (10) (7709-7720)
aerocom phase-ii , air pollution , caliop , calipso , cloud , models , ocean , satellite-observations , transport , vertical-distribution
The global aerosol extinction from the CALIOP space lidar was used to compute aerosol optical depth (AOD) over a 9-year period (2007-2015) and partitioned between the boundary layer (BL) and the free troposphere (FT) using BL heights obtained from the ERA-Interim archive. The results show that the vertical distribution of AOD does not follow the diurnal cycle of the BL but remains similar between day and night highlighting the presence of a residual layer during night. The BL and FT contribute 69 and 31 %, respectively, to the global tropospheric AOD during daytime in line with observations obtained in Aire sur l'Adour (France) using the Light Optical Aerosol Counter (LOAC) instrument. The FT AOD contribution is larger in the tropics than at mid-latitudes which indicates that convective transport largely controls the vertical profile of aerosols. Over oceans, the FT AOD contribution is mainly governed by long-range transport of aerosols from emission sources located within neighboring continents. According to the CALIOP aerosol classification, dust and smoke particles are the main aerosol types transported into the FT. Overall, the study shows that the fraction of AOD in the FT - and thus potentially located above low-level clouds - is substantial and deserves more attention when evaluating the radiative effect of aerosols in climate models. More generally, the results have implications for processes determining the overall budgets, sources, sinks and transport of aerosol particles and their description in atmospheric models.

New particle formation and growth: Creating a new atmospheric phase interface

Olenius, T.; Yli-Juuti, T.; Elm, J.; Kontkanen, J.; Riipinen, I.
2018 | Elsevier Science Publishers | Physical Chemistry of Gas-Liquid Interfaces (315-352) | ISBN: 9780128136416

Production and turnover of microbial organic matter in surface intertidal sediments

Wu, WC; Meador, T; Hinrichs, KU
2018 | Org. Geochem. | 121 (104-113)
carbon fixation , deep pore waters , endospore abundance , fatty-acids , heavy-water , heterotrophic inorganic carbon assimilation , hydrogen isotopes , intertidal flat , microbial fatty acids , microbial production , stable isotope probing , sulfate-reducing bacteria , tidal-flat sediments , vertical-distribution , wadden sea
Benthic microorganisms play a significant role in the remineralization of sedimentary organic matter (OM). In order to constrain the growth rate, turnover and carbon metabolism of microbial communities in anoxic sandy sediments, we quantified the rate of inorganic carbon (IC) assimilation and of lipid production via a recently developed dual isotope-labelling assay that can differentiate autotrophic vs. heterotrophic production in a 22 cm sediment core from the Janssand tidal flat (Wadden Sea, Germany). Despite an extremely low concentration of total organic carbon (TOC) in the majority of samples (<0.3%), the concentration of total fatty acids (TFAs) was in the range 4.5 to 28.4 mu g/mg TOC, suggestive of a high contribution of fresh microbial and algal biomass to the TOC pool. This was corroborated by a production rate of microbial FAs, which ranged from 0.3 to 4.7 mu g TFAs/g(dw)/yr (where dw = dry wt) and the mean turnover time of microbial FAs was 6 +/- 5 yr. The enhanced production rate of iso- and anteiso-branched FAs was consistent with the presence of an active population of sulfate reducing Deltaproteobacteria. The assimilation rate of IC into bacterial lipids was relatively low (0.16 +/- 0.07 mu g C/g(dw)/yr) in OM-lean sandy sediments (i.e. upper 17 cm), such that the IC assimilation to lipid production ratio values was typically <0.3, indicating that heterotrophic bacteria were dominant and dark IC fixation played a minor role at the study site. The measured rates of FA production converted to an anaerobic heterotrophic C demand of 0.4-1.8 mu g C/g(dw)/d, assuming a bacterial growth efficiency of 10%. Such high biomass proportion, production rate and C demand suggested that dissolved OM must play a vital role in sustaining the active heterotrophic microbial populations in these sandy sediments. (C) 2018 Elsevier Ltd. All rights reserved.

Challenges and opportunities for managing aquatic mercury pollution in altered landscapes

Hsu-Kim, H; Eckley, CS; Acha, D; Feng, XB; Gilmour, CC; Jonsson, S; Mitchell, CPJ
2018 | Ambio | 47 (2) (141-169)
arctic alaskan lake , contamination , derelict chloralkali plant , dissolved organic matter , landcover , mercury synthesis , methylmercury , net methylmercury production , newly deposited mercury , oryza-sativa-l. , sediment pore waters , sulfate-reducing bacteria , water-level fluctuations , western north-america
The environmental cycling of mercury (Hg) can be affected by natural and anthropogenic perturbations. Of particular concern is how these disruptions increase mobilization of Hg from sites and alter the formation of monomethylmercury (MeHg), a bioaccumulative form of Hg for humans and wildlife. The scientific community has made significant advances in recent years in understanding the processes contributing to the risk of MeHg in the environment. The objective of this paper is to synthesize the scientific understanding of how Hg cycling in the aquatic environment is influenced by landscape perturbations at the local scale, perturbations that include watershed loadings, deforestation, reservoir and wetland creation, rice production, urbanization, mining and industrial point source pollution, and remediation. We focus on the major challenges associated with each type of alteration, as well as management opportunities that could lessen both MeHg levels in biota and exposure to humans. For example, our understanding of approximate response times to changes in Hg inputs from various sources or landscape alterations could lead to policies that prioritize the avoidance of certain activities in the most vulnerable systems and sequestration of Hg in deep soil and sediment pools. The remediation of Hg pollution from historical mining and other industries is shifting towards in situ technologies that could be less disruptive and less costly than conventional approaches. Contemporary artisanal gold mining has well-documented impacts with respect to Hg; however, significant social and political challenges remain in implementing effective policies to minimize Hg use. Much remains to be learned as we strive towards the meaningful application of our understanding for stakeholders, including communities living near Hg-polluted sites, environmental policy makers, and scientists and engineers tasked with developing watershed management solutions. Site-specific assessments of MeHg exposure risk will require new methods to predict the impacts of anthropogenic perturbations and an understanding of the complexity of Hg cycling at the local scale.

Multicomponent new particle formation from sulfuric acid, ammonia, and biogenic vapors

Lehtipalo, K; Yan, C; Dada, L; Bianchi, F; Xiao, M; Wagner, R; Stolzenburg, D; Ahonen, LR; Amorim, A; Baccarini, A; Bauer, PS; Baumgartner, B; Bergen, A; Bernhammer, AK; Breitenlechner, M; Brilke, S; Buchholz, A; Mazon, SB; Chen, DX; Chen, XM; Dias, A; Dommen, J; Draper, DC; Duplissy, J; Ehn, M; Finkenzeller, H; Fischer, L; Frege, C; Fuchs, C; Garmash, O; Gordon, H; Hakala, J; He, XC; Heikkinen, L; Heinritzi, M; Helm, JC; Hofbauer, V; Hoyle, CR; Jokinen, T; Kangasluoma, J; Kerminen, VM; Kim, C; Kirkby, J; Kontkanen, J; Kurten, A; Lawler, MJ; Mai, HJ; Mathot, S; Mauldin, RL; Molteni, U; Nichman, L; Nie, W; Nieminen, T; Ojdanic, A; Onnela, A; Passananti, M; Petaja, T; Piel, F; Pospisilova, V; Quelever, LLJ; Rissanen, MP; Rose, C; Sarnela, N; Schallhart, S; Schuchmann, S; Sengupta, K; Simon, M; Sipila, M; Tauber, C; Tome, A; Trostl, J; Vaisanen, O; Vogel, AL; Volkamer, R; Wagner, AC; Wang, MY; Weitz, L; Wimmer, D; Ye, PL; Ylisirnio, A; Zha, QZ; Carslaw, KS; Curtius, J; Donahue, NM; Flagan, RC; Hansel, A; Riipinen, I; Virtanen, A; Winkler, PM; Baltensperger, U; Kulmala, M; Worsnop, DR
2018 | Sci. Adv. | 4 (12)
A major fraction of atmospheric aerosol particles, which affect both air quality and climate, form from gaseous precursors in the atmosphere. Highly oxygenated organic molecules (HOMs), formed by oxidation of biogenic volatile organic compounds, are known to participate in particle formation and growth. However, it is not well understood how they interact with atmospheric pollutants, such as nitrogen oxides (NOx) and sulfur oxides (SOx) from fossil fuel combustion, as well as ammonia (NH3) from livestock and fertilizers. Here, we show how NOx suppresses particle formation, while HOMs, sulfuric acid, and NH3 have a synergistic enhancing effect on particle formation. We postulate a novel mechanism, involving HOMs, sulfuric acid, and ammonia, which is able to closely reproduce observations of particle formation and growth in daytime boreal forest and similar environments. The findings elucidate the complex interactions between biogenic and anthropogenic vapors in the atmospheric aerosol system.

Growth of sedimentary Bathyarchaeota on lignin as an energy source

Yu, TT; Wu, WC; Liang, WY; Lever, MA; Hinrichs, KU; Wang, FP
2018 | Proc. Natl. Acad. Sci. U.S.A. | 115 (23) (6022-6027)
bathyarchaeota , carbon fixation , group lineage , lignin degradation , lipid , marine-sediments , mass spectrometry , mcg archaea , methane , microbial communities , miscellaneous crenarchaeotal group , organic-matter , sedimentary carbon cycling , subseafloor sediments
Members of the archaeal phylum Bathyarchaeota are among the most abundant microorganisms on Earth. Although versatile metabolic capabilities such as acetogenesis, methanogenesis, and fermentation have been suggested for bathyarchaeotal members, no direct confirmation of these metabolic functions has been achieved through growth of Bathyarchaeota in the laboratory. Here we demonstrate, on the basis of gene-copy numbers and probing of archaeal lipids, the growth of Bathyarchaeota subgroup Bathy-8 in enrichments of estuarine sediments with the biopolymer lignin. Other organic substrates (casein, oleic acid, cellulose, and phenol) did not significantly stimulate growth of Bathyarchaeota. Meanwhile, putative bathyarchaeotal tetraether lipids incorporated C-13 from C-13-bicarbonate only when added in concert with lignin. Our results are consistent with organoautotrophic growth of a bathyarchaeotal group with lignin as an energy source and bicarbonate as a carbon source and shed light into the cycling of one of Earth's most abundant biopolymers in anoxic marine sediment.

Simulation of the size-composition distribution of atmospheric nanoparticles over Europe

Patoulias, D; Fountoukis, C; Riipinen, I; Asmi, A; Kulmala, M; Pandis, SN
2018 | Atmos. Chem. Phys. | 18 (18) (13639-13654)
PMCAMx-UF, a three-dimensional chemical transport model focusing on the simulation of the ultrafine particle size distribution and composition has been extended with the addition of the volatility basis set (VBS) approach for the simulation of organic aerosol (OA). The model was applied in Europe to quantify the effect of secondary semi-volatile organic vapors on particle number concentrations. The model predictions were evaluated against field observations collected during the PEGASOS 2012 campaign. The measurements included both ground and airborne measurements, from stations across Europe and a zeppelin measuring above Po Valley. The ground level concentrations of particles with a diameter larger than 100 nm (N-100) were reproduced with a daily normalized mean error of 40% and a daily normalized mean bias of -20 %. PMCAMx-UF tended to overestimate the concentration of particles with a diameter larger than 10 nm (N-10) with a daily normalized mean bias of 75 %. The model was able to reproduce, within a factor of 2, 85% of the N-10 and 75% of the N-100 zeppelin measurements above ground. The condensation of organics led to an increase (50 %-120 %) in the N-100 concentration mainly in central and northern Europe, while the N-10 concentration decreased by 10 %-30 %. Including the VBS in PMCAMx-UF improved its ability to simulate aerosol number concentration compared to simulations neglecting organic condensation on ultrafine particles.

Facing the rain after the phase out: Performance evaluation of alternative fluorinated and non-fluorinated durable water repellents for outdoor fabrics

Schellenberger, S.; Gillgard, P.; Stare, A.; Hanning, A.; Levenstam, O.; Roos, S.; Cousins, I.T.
2018 | Chemosphere | 193 (675-684)

Cloud droplet activation of black carbon particles coated with organic compounds of varying solubility

Dalirian, M; Ylisirnio, A; Buchholz, A; Schlesinger, D; Strom, J; Virtanen, A; Riipinen, I
2018 | Atmos. Chem. Phys. | 18 (16) (12477-12489)
Atmospheric black carbon (BC) particles are a concern due to their impact on air quality and climate. Their net climate effect is, however, still uncertain. This uncertainty is partly related to the contribution of coated BC particles to the global cloud condensation nuclei (CCN) budgets. In this study, laboratory measurements were performed to investigate CCN activity of BC (REGAL 400R pigment black) particles, in pure state or coated through evaporating and subsequent condensation of glutaric acid, levoglucosan (both water-soluble organics) or oleic acid (an organic compound with low solubility). A combination of soot particle aerosol mass spectrometer (SP-AMS) measurements and size distribution measurements with a scanning mobility particle sizer (SMPS) showed that the studied BC particles were nearly spherical agglomerates with a fractal dimension of 2.79 and that they were coated evenly by the organic species. The CCN activity of BC particles increased after coating with all the studied compounds and was governed by the fraction of organic material. The CCN activation of the BC particles coated by glutaric acid and levoglucosan were in good agreement with the theoretical calculations using the shell-and-core model, which is based on a combination of the CCN activities of the pure compounds. The oleic acid coating enhanced the CCN activity of the BC particles, even though the pure oleic acid particles were CCN inactive. The surprising effect of oleic acid might be related to the arrangement of the oleic acid molecules on the surface of the BC cores or other surface phenomena facilitating water condensation onto the coated particles. Our results show that present theories have potential for accurately predicting the CCN activity of atmospheric BC coated with organic species, given that the identities and amounts of the coating species are known. Furthermore, our results suggest that even relatively thin soluble coatings (around 2 nm for the compounds studied here) are enough to make the insoluble BC particles CCN active at typical atmospheric supersaturations and thus be efficiently taken up by cloud droplets. This highlights the need for an accurate description of the composition of atmospheric particles containing BC to unravel their net impact on climate.

Black carbon emission and transport mechanisms to the free troposphere at the La Paz/El Alto (Bolivia) metropolitan area based on the Day of Census (2012)

Wiedensohler, A; Andrade, M; Weinhold, K; Muller, T; Birmili, W; Velarde, F; Moreno, I; Forno, R; Sanchez, MF; Laj, P; Ginot, P; Whiteman, DN; Krejci, R; Sellegri, K; Reichler, T
2018 | Atmos Environ | 194 (158-169)
aerosol , black carbon , free troposphere , high-altitude station , network , particle-size spectrometers , pollution transport , range , traffic emissions , variability
Urban development, growing industrialization, and increasing demand for mobility have led to elevated levels of air pollution in many large cities in Latin America, where air quality standards and WHO guidelines are frequently exceeded. The conurbation of the metropolitan area of La Paz/El Alto is one of the fastest growing urban settlements in South America with the particularity of being located in a very complex terrain at a high altitude. As many large cities or metropolitan areas, the metropolitan area of La Paz/El Alto and the Altiplano region are facing air quality deterioration. Long-term measurement data of the equivalent black carbon (eBC) mass concentrations and particle number size distributions (PNSD) from the Global Atmosphere Watch Observatory Chacaltaya (CHC; 5240 m a.s.l., above sea level) indicated a systematic transport of particle matter from the metropolitan area of La Paz/El Alto to this high altitude station and subsequently to the lower free troposphere. To better understand the sources and the transport mechanisms, we conducted eBC and PNSDs measurements during an intensive campaign at two locations in the urban area of La Paz/El Alto from September to November 2012. While the airport of El Alto site (4040 m a.s.l.) can be seen as representative of the urban and Altiplano background, the road site located in Central La Paz (3590 m a.s.l.) is representative for heavy traffic-dominated conditions. Peaks of eBC mass concentrations up to 5 mu g m(-3) were observed at the El Alto background site in the early morning and evening, while minimum values were detected in the early afternoon, mainly due to thermal convection and change of the planetary boundary layer height. The traffic-related eBC mass concentrations at the road site reached maximum values of 10-20 mu g m(-3). A complete traffic ban on the specific Bolivian Day of Census (November 21, 2012) led to a decrease of eBC below 1 mu g m(-3) at the road site for the entire day. Compared to the day before and after, particle number concentrations decreased by a factor between 5 and 25 over the particle size range from 10 to 800 nm, while the submicrometer particle mass concentration dropped by approximately 80%. These results indicate that traffic is the dominating source of BC and particulate air pollution in the metropolitan area of La Paz/El Alto. In general, the diurnal cycle of eBC mass concentration at the Chacaltaya observatory is anti-correlated to the observations at the El Alto background site. This pattern indicates that the traffic-related particulate matter, including BC, is transported to higher altitudes with the developing of the boundary layer during daytime. The metropolitan area of La Paz/El Alto seems to be a significant source for BC of the regional lower free troposphere. From there, BC can be transported over long distances and exert impact on climate and composition of remote southern hemisphere.

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