Atmospheric Chemistry and Physics Discussions
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2003
10.5194/acpd-3-3869-2003
http://www.atmos-chem-phys-discuss.net/3/3869/2003/
http://www.atmos-chem-phys-discuss.net/3/3869/2003/acpd-3-3869-2003.html
http://www.atmos-chem-phys-discuss.net/3/3869/2003/acpd-3-3869-2003.pdf
3869
3906
2003-07-25
Gaseous (DMS, MSA, SO<sub>2</sub>, H<sub>2</sub>SO<sub>4</sub> and DMSO) and particulate (sulfate and methanesulfonate) sulfur species over the northeastern coast of Crete
H. Bardouki
H. Berresheim
M. Vrekoussis
J. Sciare
G. Kouvarakis
K. Oikonomou
J. Schneider
N. Mihalopoulos
Environmental Chemical Processes Laboratory (ECPL), Department of Chemistry, University of Crete, P.O Box 1470, 71409 Heraklion Greece
Deutscher Wetterdienst (DWD), Meteorological Observatory, Hohenpeissenberg, Germany
Max-Planck Institute for Chemistry, Biogeochemistry Division, Mainz, Germany
now at LSCE, Orme des Merisiers, Bat 709, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
A detailed study of the levels, the temporal and diurnal variability of the main
compounds involved in the biogenic sulfur cycle was carried out in Crete (Eastern
Mediterranean) during the Mediterranean Intensive Oxidant Study (MINOS) field
experiment in July-August 2001. Intensive measurements of gaseous dimethylsulfide
(DMS), dimethylsulfoxide (DMSO), sulfur dioxide (SO<sub>2</sub>), sulfuric
(H<sub>2</sub>SO<sub>4</sub>) and methanesulfonic acids (MSA) and particulate sulfate
(SO<sub>4</sub><sup>2−</sup>) and methanesulfonate (MS<sup>−</sup>) have been performed during the campaign.<br>
<br>
Dimethylsulfide (DMS) levels ranged from 2.9 to 136 pmol · mol<sup>-1</sup> (mean value of
21.7 pmol · mol<sup>−1</sup>) and showed a clear diurnal variation with daytime maximum. During
nighttime DMS levels fall close or below the detection limit of 2 pmol
·mol<sup>−1</sup>. Concurrent measurements of OH and NO<sub>3</sub> radicals during the campaign indicate that
NO<sub>3</sub> levels can explain most of the observed diurnal variation of DMS. Dimethylsulfoxide
(DMSO) ranged between 0.02 and 10.1 pmol · mol<sup>−1</sup> (mean value of
1.7 pmol · mol<sup>−1</sup>) and presents a diurnal variation similar to that of
DMS. SO<sup>2</sup> levels ranged from 220 to 2970 pmol · mol<sup>−1</sup>
(mean value of 1030 pmol · mol<sup>−1</sup>), while nss-SO<sub>4</sub><sup>2−</sup> and
MS<sup>−</sup> ranged from 330 to 7100 pmol · mol<sup>−1</sup>, (mean value of
1440 pmol · mol<sup>−1</sup>) and 1.1 to 37.5 pmol · mol<sup>−</sup> (mean value of
11.5 pmol · mol<sup>−1</sup>) respectively.<br>
<br>
Of particular interest are the measurements of gaseous MSA and H<sub>2</sub>SO<sub>4</sub>. MSA ranged
from below the detection limit (3×10<sup>4</sup>) to 3.7×10<sup>7</sup>
molecules cm<sup>−3</sup>, whereas H<sub>2</sub>SO<sub>4</sub> ranged between
1×10<sup>5</sup> and 9.0×10<sup>7</sup> molecules cm<sup>−3</sup>. The measured
H<sub>2</sub>SO<sub>4</sub> maxima are among the highest reported in literature and can be attributed to high insolation, absence
of precipitation and increased SO<sub>2</sub> levels in the area. From the concurrent
SO<sub>2</sub>, OH, and H<sub>2</sub>SO<sub>4</sub> measurements a sticking coefficient of
0.52±0.28 was calculated for H<sub>2</sub>SO<sub>4</sub>.
From the concurrent MSA, OH, and DMS measurements the yield of gaseous MSA from
the OH-initiated oxidation of DMS was calculated to range between
0.1–0.4%. This low MSA yield implies that gaseous MSA levels can not account for the observed
MS<sup>−</sup> levels. Heterogeneous reactions of DMSO on aerosols should be considered to explain the
observed levels of MS<sup>−</sup>.