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Volume 15, issue 14
Atmos. Chem. Phys., 15, 7961-7976, 2015
https://doi.org/10.5194/acp-15-7961-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: CHemistry and AeRosols Mediterranean EXperiments (ChArMEx)...

Atmos. Chem. Phys., 15, 7961-7976, 2015
https://doi.org/10.5194/acp-15-7961-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 20 Jul 2015

Research article | 20 Jul 2015

Primary marine aerosol emissions from the Mediterranean Sea during pre-bloom and oligotrophic conditions: correlations to seawater chlorophyll a from a mesocosm study

A. N. Schwier1, C. Rose1, E. Asmi1,a, A. M. Ebling2, W. M. Landing2, S. Marro3,4, M.-L. Pedrotti3,4, A. Sallon3,4, F. Iuculano5, S. Agusti5,6, A. Tsiola7, P. Pitta7, J. Louis3,4, C. Guieu3,4, F. Gazeau3,4, and K. Sellegri1 A. N. Schwier et al.
  • 1Laboratoire de Météorologie Physique CNRS UMR6016, Observatoire de Physique du Globe de Clermont-Ferrand, Université Blaise Pascal, 63171 Aubière, France
  • 2Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306-4520, USA
  • 3Laboratoire d'Océanographie de Villefranche (LOV), CNRS UMR7093, Observatoire océanologique, 06230 Villefranche-sur-mer, France
  • 4Sorbonne Universités, UPMC Univ Paris 06, UMR7093, LOV, Observatoire océanologique, 06230 Villefranche-sur-mer, France
  • 5Instituto Mediterráneo de Estudios Avanzados (IMEDEA CSIC-UIB), 07190 Esporles, Mallorca, Spain
  • 6The UWA Oceans Institute and School of Plant Biology, University of Western Australia, 35 Stirling Highway, Crawley 6009, Australia
  • 7Hellenic Centre for Marine Research (HCMR), P.O. Box 2214, 71003 Heraklion, Crete, Greece
  • anow at: Finnish Meteorological Institute, P.O. Box 503, 00101, Helsinki, Finland

Abstract. The effect of ocean acidification and changing water conditions on primary (and secondary) marine aerosol emissions is not well understood on a regional or a global scale. To investigate this effect as well as the indirect effect on aerosol that changing biogeochemical parameters can have, ~ 52 m3 pelagic mesocosms were deployed for several weeks in the Mediterranean Sea during both winter pre-bloom and summer oligotrophic conditions and were subjected to various levels of CO2 to simulate the conditions foreseen in this region for the coming decades. After seawater sampling, primary bubble-bursting aerosol experiments were performed using a plunging water jet system to test both chemical and physical aerosol parameters (10–400 nm). Comparing results obtained during pre-bloom and oligotrophic conditions, we find the same four log-normal modal diameters (18.5 ± 0.6, 37.5 ± 1.4, 91.5 ± 2.0, 260 ± 3.2 nm) describing the aerosol size distribution during both campaigns, yet pre-bloom conditions significantly increased the number fraction of the second (Aitken) mode, with an amplitude correlated to virus-like particles, heterotrophic prokaryotes, TEPs (transparent exopolymeric particles), chlorophyll a and other pigments. Organic fractions determined from kappa closure calculations for the diameter, Dp ~ 50 nm, were much larger during the pre-bloom period (64 %) than during the oligotrophic period (38 %), and the organic fraction decreased as the particle size increased. Combining data from both campaigns together, strong positive correlations were found between the organic fraction of the aerosol and chlorophyll a concentrations, heterotrophic and autotrophic bacteria abundance, and dissolved organic carbon (DOC) concentrations. As a consequence of the changes in the organic fraction and the size distributions between pre-bloom and oligotrophic periods, we find that the ratio of cloud condensation nuclei (CCN) to condensation nuclei (CN) slightly decreased during the pre-bloom period. The enrichment of the seawater samples with microlayer samples did not have any effect on the size distribution, organic content or the CCN activity of the generated primary aerosol. Partial pressure of CO2, pCO2, perturbations had little effect on the physical or chemical parameters of the aerosol emissions, with larger effects observed due to the differences between a pre-bloom and oligotrophic environment.

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The effect of ocean acidification and changing water conditions on primary (and secondary) marine aerosol emissions is not well understood on a regional or a global scale. To investigate this effect, we deployed mesocosms in the Mediterranean Sea for several weeks during both winter pre-bloom and summer oligotrophic conditions and subjected them to various levels of CO2. We observed larger effects due to the differences between a pre-bloom and oligotrophic environment than due to CO2 levels.
The effect of ocean acidification and changing water conditions on primary (and secondary)...
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