Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements
This study aims to determine the mineral contribution to PM<sub>10</sub> in the central Mediterranean Sea, based on 7 yr of daily PM<sub>10</sub> samplings made on the island of Lampedusa (35.5° N, 12.6° E). <br><br> The chemical composition of the PM<sub>10...
| Main Authors: | , , , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2014-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/2039/2014/acp-14-2039-2014.pdf |
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| author | M. Marconi D. M. Sferlazzo S. Becagli C. Bommarito G. Calzolai M. Chiari A. di Sarra C. Ghedini J. L. Gómez-Amo F. Lucarelli D. Meloni F. Monteleone S. Nava G. Pace S. Piacentino F. Rugi M. Severi R. Traversi R. Udisti |
| author_facet | M. Marconi D. M. Sferlazzo S. Becagli C. Bommarito G. Calzolai M. Chiari A. di Sarra C. Ghedini J. L. Gómez-Amo F. Lucarelli D. Meloni F. Monteleone S. Nava G. Pace S. Piacentino F. Rugi M. Severi R. Traversi R. Udisti |
| author_sort | M. Marconi |
| collection | DOAJ |
| description | This study aims to determine the mineral contribution to
PM<sub>10</sub> in the central Mediterranean Sea, based on 7 yr of daily PM<sub>10</sub>
samplings made on the island of Lampedusa (35.5° N, 12.6° E).
<br><br>
The chemical composition of the PM<sub>10</sub> samples was determined by ion
chromatography for the main ions, and, on selected samples, by particle-induced
X-ray emission (PIXE) for the total content of crustal markers.
Aerosol optical depth measurements were carried out in parallel to the
PM<sub>10</sub> sampling.
<br><br>
The average PM<sub>10</sub> concentration at Lampedusa over the period June
2004–December 2010 is 31.5 μg m<sup>−3</sup>, with low interannual
variability. The annual means are below the EU annual standard for
PM<sub>10</sub>, but 9.9% of the total number of daily data exceeds the daily
threshold value established by the European Commission for PM
(50 μg m<sup>−3</sup>, European Community, EC/30/1999).
<br><br>
The Saharan dust contribution to PM<sub>10</sub> was derived by calculating the
contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides
in samples in which PIXE data were available. Cases in which crustal content
exceeded the 75th percentile of the crustal oxide content distribution were
identified as elevated dust events. Using this threshold, we obtained 175
events. Fifty-five elevated dust events (31.6%) displayed PM<sub>10</sub> higher
than 50 μg m<sup>−3</sup>, with dust contributing by 33% on average.
<br><br>
The crustal contribution to PM<sub>10</sub> has an annual average value of 5.42 μg m<sup>−3</sup>,
and reaches a value as high as 67.9 μg m<sup>−3</sup> (corresponding
to 49% of PM<sub>10</sub>) during an intense Saharan dust event.
<br><br>
The crustal content estimated from a single tracer, such as Al or Ca, is in
good agreement with the one calculated as the sum of the metal oxides.
Conversely, larger crustal contents are derived by applying the EU guidelines
for demonstration and subtraction of exceedances in PM<sub>10</sub> levels due to
high background of natural aerosol. The crustal aerosol amount and
contribution to PM<sub>10</sub> showed a very small seasonal dependence;
conversely, the dust columnar burden displays an evident annual cycle, with a
strong summer maximum (monthly average aerosol optical depth at 500 nm up to
0.28 in June–August). We found that 71.3% of the dust events identified
from optical properties over the atmospheric column display a high dust
content at the ground level. Conversely, the remaining 28.7% of cases
present a negligible or small impact on the surface aerosol composition due
to the transport processes over the Mediterranean Sea, where dust frequently
travels above the marine boundary layer, especially in summer.
<br><br>
Based on backward trajectories, two regions, one in Algeria–Tunisia, and one
in Libya, are identified as main source areas for intense dust episodes
occurring mainly in autumn and winter. Data on the bulk composition of mineral
aerosol arising from these two source areas are scarce; results on
characteristic ratios between elements show somewhat higher values of
Ca / Al and (Ca + Mg) / Fe (2.5 ± 1.0, and 4.7 ± 2.0, respectively) for
Algeria–Tunisia than for Libyan origin (Ca / Al = 1.9 ± 0.7 and
(Ca + Mg) / Fe = 3.3 ± 1.1). |
| first_indexed | 2024-12-12T01:38:46Z |
| format | Article |
| id | doaj.art-396eb1c34cf1449b936eb4d87a156b42 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T01:38:46Z |
| publishDate | 2014-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-396eb1c34cf1449b936eb4d87a156b422022-12-22T00:42:46ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242014-02-011442039205410.5194/acp-14-2039-2014Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurementsM. Marconi0D. M. Sferlazzo1S. Becagli2C. Bommarito3G. Calzolai4M. Chiari5A. di Sarra6C. Ghedini7J. L. Gómez-Amo8F. Lucarelli9D. Meloni10F. Monteleone11S. Nava12G. Pace13S. Piacentino14F. Rugi15M. Severi16R. Traversi17R. Udisti18Department of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyENEA, Laboratory for Earth Observations and Analyses, 92010, Lampedusa, ItalyDepartment of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyENEA, Laboratory for Earth Observations and Analyses, 90141, Palermo, ItalyDepartment of Physics and Astronomy, University of Florence and I.N.F.N., Florence, Via Sansone 1, 50019 Sesto F.no, Florence, ItalyDepartment of Physics and Astronomy, University of Florence and I.N.F.N., Florence, Via Sansone 1, 50019 Sesto F.no, Florence, ItalyENEA Laboratory for Earth Observations and Analyses, 00123, Rome, ItalyDepartment of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyENEA Laboratory for Earth Observations and Analyses, 00123, Rome, ItalyDepartment of Physics and Astronomy, University of Florence and I.N.F.N., Florence, Via Sansone 1, 50019 Sesto F.no, Florence, ItalyENEA Laboratory for Earth Observations and Analyses, 00123, Rome, ItalyENEA, Laboratory for Earth Observations and Analyses, 90141, Palermo, ItalyDepartment of Physics and Astronomy, University of Florence and I.N.F.N., Florence, Via Sansone 1, 50019 Sesto F.no, Florence, ItalyENEA Laboratory for Earth Observations and Analyses, 00123, Rome, ItalyENEA, Laboratory for Earth Observations and Analyses, 90141, Palermo, ItalyDepartment of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyDepartment of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyDepartment of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyDepartment of Chemistry, University of Florence, Sesto Fiorentino, Florence, 50019, ItalyThis study aims to determine the mineral contribution to PM<sub>10</sub> in the central Mediterranean Sea, based on 7 yr of daily PM<sub>10</sub> samplings made on the island of Lampedusa (35.5° N, 12.6° E). <br><br> The chemical composition of the PM<sub>10</sub> samples was determined by ion chromatography for the main ions, and, on selected samples, by particle-induced X-ray emission (PIXE) for the total content of crustal markers. Aerosol optical depth measurements were carried out in parallel to the PM<sub>10</sub> sampling. <br><br> The average PM<sub>10</sub> concentration at Lampedusa over the period June 2004–December 2010 is 31.5 μg m<sup>−3</sup>, with low interannual variability. The annual means are below the EU annual standard for PM<sub>10</sub>, but 9.9% of the total number of daily data exceeds the daily threshold value established by the European Commission for PM (50 μg m<sup>−3</sup>, European Community, EC/30/1999). <br><br> The Saharan dust contribution to PM<sub>10</sub> was derived by calculating the contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides in samples in which PIXE data were available. Cases in which crustal content exceeded the 75th percentile of the crustal oxide content distribution were identified as elevated dust events. Using this threshold, we obtained 175 events. Fifty-five elevated dust events (31.6%) displayed PM<sub>10</sub> higher than 50 μg m<sup>−3</sup>, with dust contributing by 33% on average. <br><br> The crustal contribution to PM<sub>10</sub> has an annual average value of 5.42 μg m<sup>−3</sup>, and reaches a value as high as 67.9 μg m<sup>−3</sup> (corresponding to 49% of PM<sub>10</sub>) during an intense Saharan dust event. <br><br> The crustal content estimated from a single tracer, such as Al or Ca, is in good agreement with the one calculated as the sum of the metal oxides. Conversely, larger crustal contents are derived by applying the EU guidelines for demonstration and subtraction of exceedances in PM<sub>10</sub> levels due to high background of natural aerosol. The crustal aerosol amount and contribution to PM<sub>10</sub> showed a very small seasonal dependence; conversely, the dust columnar burden displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm up to 0.28 in June–August). We found that 71.3% of the dust events identified from optical properties over the atmospheric column display a high dust content at the ground level. Conversely, the remaining 28.7% of cases present a negligible or small impact on the surface aerosol composition due to the transport processes over the Mediterranean Sea, where dust frequently travels above the marine boundary layer, especially in summer. <br><br> Based on backward trajectories, two regions, one in Algeria–Tunisia, and one in Libya, are identified as main source areas for intense dust episodes occurring mainly in autumn and winter. Data on the bulk composition of mineral aerosol arising from these two source areas are scarce; results on characteristic ratios between elements show somewhat higher values of Ca / Al and (Ca + Mg) / Fe (2.5 ± 1.0, and 4.7 ± 2.0, respectively) for Algeria–Tunisia than for Libyan origin (Ca / Al = 1.9 ± 0.7 and (Ca + Mg) / Fe = 3.3 ± 1.1).http://www.atmos-chem-phys.net/14/2039/2014/acp-14-2039-2014.pdf |
| spellingShingle | M. Marconi D. M. Sferlazzo S. Becagli C. Bommarito G. Calzolai M. Chiari A. di Sarra C. Ghedini J. L. Gómez-Amo F. Lucarelli D. Meloni F. Monteleone S. Nava G. Pace S. Piacentino F. Rugi M. Severi R. Traversi R. Udisti Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements Atmospheric Chemistry and Physics |
| title | Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements |
| title_full | Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements |
| title_fullStr | Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements |
| title_full_unstemmed | Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements |
| title_short | Saharan dust aerosol over the central Mediterranean Sea: PM<sub>10</sub> chemical composition and concentration versus optical columnar measurements |
| title_sort | saharan dust aerosol over the central mediterranean sea pm sub 10 sub chemical composition and concentration versus optical columnar measurements |
| url | http://www.atmos-chem-phys.net/14/2039/2014/acp-14-2039-2014.pdf |
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