Dry deposition is one of the two major routes for aerosol particles to be removed from the atmosphere and be transferred into another environment. Aerosol dry deposition processes are not yet fully understood, as well as aerosols impact on cloud processes and earth’s radiation budget. For these reasons, measurements of size distribution, composition and mixing state on single aerosol particles are mandatory. Results from a dry deposition measurement network across the Mediterranean (XMed-Dry) will be discussed. For the first phase of XMed-Dry (April 2017–March 2018), a set of seven newly developed dry deposition-only collectors were installed at different locations across the Mediterranean (two sites in Spain, one in France, Malta, Italy, Greece, and Cyprus) to capture spatial and temporal variability. The second phase of XMed-Dry is aiming for long-term monitoring at three sites: Lecce (Italy), Nicosia (Cyprus), and a new one at Alicante (Spain). Particles deposited were collected on pure carbon adhesive that was subject to SEM–EDX analysis to obtain size, shape, and elemental composition of single particles. Results show that dry deposition consists of a highly variable mixture of sea-salt, sulfate, mineral dust, metal oxides, and biological material, depending on location, season and meteorological situation. Results of samples collected in Lecce during the first one and a half years show total aerosol deposition in the range of 4–25 mg m−2 d−1, which is comparable to other locations in the medium range outflow of a desert. Expectedly, during Saharan intrusions the values are at the upper end of the range. Most of the mass is contributed by particles >15 µm in diameter, whereas the super-micron (coarse) PM10 size range contributes approximately 10%. Most of the particles are silicates with a comparatively high 20% of carbonates, which might be in part of local origin. In the coarse PM10 range, sea-salt contributes about half of the mass between 2 and 10 µm, and sulfate contributes half in the range 1–2 µm. In particular, the sulfate contribution is highly variable. Measurements of dry deposition with sub-weekly time resolution are rare. In our study, a data set of more than 150 samples of dry deposition collected in Lecce and analyzed for size, shape, and composition for single particle provide relevant information not only for spatial and temporary variability, but also for deposition processes and its sources provenance.

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XMed-Dry Network: Results of the First Year and a Half of Sampling in Lecce

  • Pierina Ielpo,
  • Kilian Schneiders,
  • Melanie Eknayan,
  • Ferdinando De Tomasi,
  • Konrad Kandler

摘要

Dry deposition is one of the two major routes for aerosol particles to be removed from the atmosphere and be transferred into another environment. Aerosol dry deposition processes are not yet fully understood, as well as aerosols impact on cloud processes and earth’s radiation budget. For these reasons, measurements of size distribution, composition and mixing state on single aerosol particles are mandatory. Results from a dry deposition measurement network across the Mediterranean (XMed-Dry) will be discussed. For the first phase of XMed-Dry (April 2017–March 2018), a set of seven newly developed dry deposition-only collectors were installed at different locations across the Mediterranean (two sites in Spain, one in France, Malta, Italy, Greece, and Cyprus) to capture spatial and temporal variability. The second phase of XMed-Dry is aiming for long-term monitoring at three sites: Lecce (Italy), Nicosia (Cyprus), and a new one at Alicante (Spain). Particles deposited were collected on pure carbon adhesive that was subject to SEM–EDX analysis to obtain size, shape, and elemental composition of single particles. Results show that dry deposition consists of a highly variable mixture of sea-salt, sulfate, mineral dust, metal oxides, and biological material, depending on location, season and meteorological situation. Results of samples collected in Lecce during the first one and a half years show total aerosol deposition in the range of 4–25 mg m−2 d−1, which is comparable to other locations in the medium range outflow of a desert. Expectedly, during Saharan intrusions the values are at the upper end of the range. Most of the mass is contributed by particles >15 µm in diameter, whereas the super-micron (coarse) PM10 size range contributes approximately 10%. Most of the particles are silicates with a comparatively high 20% of carbonates, which might be in part of local origin. In the coarse PM10 range, sea-salt contributes about half of the mass between 2 and 10 µm, and sulfate contributes half in the range 1–2 µm. In particular, the sulfate contribution is highly variable. Measurements of dry deposition with sub-weekly time resolution are rare. In our study, a data set of more than 150 samples of dry deposition collected in Lecce and analyzed for size, shape, and composition for single particle provide relevant information not only for spatial and temporary variability, but also for deposition processes and its sources provenance.