Dust–air pollution dynamics over the eastern Mediterranean

Abstract. Interactions of desert dust and air pollution over the eastern Mediterranean (EM) have been studied, focusing on two distinct dust transport events on 22 and 28 September 2011. The atmospheric chemistry–climate model EMAC has been used at about 50 km grid spacing, applying an online dust emission scheme and calcium as a proxy for dust reactivity. EMAC includes a detailed tropospheric chemistry mechanism, aerosol microphysics and thermodynamics schemes to describe dust "aging". The model is evaluated using ground-based observations for aerosol concentrations and aerosol optical depth (AOD) as well as satellite observations. Simulation results and back trajectory analysis show that the development of synoptic disturbances over the EM can enhance dust transport from the Sahara and Arabian deserts in frontal systems that also carry air pollution to the EM. The frontal systems are associated with precipitation that controls the dust removal. Our results show the importance of chemical aging of dust, which increases particle size, dust deposition and scavenging efficiency during transport, overall reducing the lifetime relative to non-aged dust particles. The relatively long travel periods of Saharan dust result in more sustained aging compared to Arabian dust. Sensitivity simulations indicate 3 times more dust deposition of aged relative to pristine dust, which significantly decreases the dust lifetime and loading.

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Dust–air pollution dynamics over the Eastern Mediterranean

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-7493-2015 ◽

2015 ◽

Vol 15 (5) ◽

pp. 7493-7534

Author(s):

M. Abdelkader ◽

S. Metzger ◽

M. Astitha ◽

Z. Levin ◽

J. Lelieveld

Keyword(s):

Air Pollution ◽

Atmospheric Chemistry ◽

Climate Model ◽

Eastern Mediterranean ◽

Tropospheric Chemistry ◽

Saharan Dust ◽

Back Trajectory ◽

Dust Deposition ◽

Dust Transport ◽

Frontal Systems

Abstract. Interactions of desert dust and air pollution over the Eastern Mediterranean (EM) have been studied, focusing on two distinct dust transport events on 22 and 28 September 2011. The atmospheric chemistry–climate model EMAC has been used at about 50 km grid spacing, applying an online dust emission scheme and calcium as a proxy for dust reactivity. EMAC includes a detailed tropospheric chemistry mechanism, aerosol microphysics and thermodynamics schemes to describe dust "aging". The model is evaluated using ground-based observations for aerosol concentrations and aerosol optical depth as well as satellite observations. Simulation results and back trajectory analysis show that the development of synoptic disturbances over the EM can enhance dust transport from the Sahara and Arabian deserts in frontal systems that also carry air pollution to the EM. The frontal systems are associated with precipitation that control the dust removal. Our results show the importance of chemical aging and deposition of the dust during transport. The relatively long travel periods of Saharan dust result in more sustained aging compared to Arabian dust. Sensitivity simulations indicate three times more rapid dust deposition of aged relative to pristine dust, which significantly decreases the dust lifetime and loading.

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Saharan dust and giant quartz particle transport towards Iceland

Scientific Reports ◽

10.1038/s41598-021-91481-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

György Varga ◽

Pavla Dagsson-Walhauserová ◽

Fruzsina Gresina ◽

Agusta Helgadottir

Keyword(s):

Numerical Models ◽

Saharan Dust ◽

Atmospheric Environment ◽

The Arctic ◽

Dust Particles ◽

Atmospheric Flow ◽

Dust Transport ◽

Strong Winds ◽

Dust Events ◽

Local Dust

AbstractMineral dust emissions from Saharan sources have an impact on the atmospheric environment and sedimentary units in distant regions. Here, we present the first systematic observations of long-range Saharan dust transport towards Iceland. Fifteen Saharan dust episodes were identified to have occurred between 2008 and 2020 based on aerosol optical depth data, backward trajectories and numerical models. Icelandic samples from the local dust sources were compared with deposited dust from two severe Saharan dust events in terms of their granulometric and mineralogical characteristics. The episodes were associated with enhanced meridional atmospheric flow patterns driven by unusual meandering jets. Strong winds were able to carry large Saharan quartz particles (> 100 µm) towards Iceland. Our results confirm the atmospheric pathways of Saharan dust towards the Arctic, and identify new northward meridional long-ranged transport of giant dust particles from the Sahara, including the first evidence of their deposition in Iceland as previously predicted by models.

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Saharan dust levels in Greece and received inhalation doses

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-11967-2008 ◽

2008 ◽

Vol 8 (3) ◽

pp. 11967-11996 ◽

Cited By ~ 3

Author(s):

C. Mitsakou ◽

G. Kallos ◽

N. Papantoniou ◽

C. Spyrou ◽

S. Solomos ◽

...

Keyword(s):

Urban Areas ◽

Particle Deposition ◽

Mineral Dust ◽

Weather Conditions ◽

Pm10 Concentration ◽

Saharan Dust ◽

Dust Particles ◽

Annual Number ◽

Human Respiratory Tract ◽

Dust Transport

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in all south European areas and especially urban. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by much more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

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Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara

10.5194/egusphere-egu2020-5722 ◽

2020 ◽

Author(s):

Claire Ryder ◽

Eleanor Highwood ◽

Adrian Walser ◽

Petra Walser ◽

Anne Philipp ◽

...

Keyword(s):

Mass Concentration ◽

Size Range ◽

State Of The Art ◽

Chem Phys ◽

Saharan Dust ◽

Dust Particles ◽

Field Campaign ◽

Dust Transport ◽

Coarse Mode ◽

Significant Underestimation

Mineral dust is an important component of the climate system, interacting with radiation, clouds, and biogeochemical systems and impacting atmospheric circulation, air quality, aviation, and solar energy generation. These impacts are sensitive to dust particle size distribution (PSD), yet models struggle or even fail to represent coarse (diameter (d)&#160;>2.5&#8201;&#181;m) and giant (d>20&#8201;&#181;m) dust particles and the evolution of the PSD with transport. Here we examine three state-of-the-art airborne observational datasets, all of which measured the full size range of dust (d=0.1&#160;to&#160;>100&#8201;&#181;m) at different stages during transport with consistent instrumentation. We quantify the presence and evolution of coarse and giant particles and their contribution to optical properties using airborne observations over the Sahara (from the Fennec field campaign) and in the Saharan Air Layer (SAL) over the tropical eastern Atlantic (from the AER-D field campaign).Observations show significantly more abundant coarse and giant dust particles over the Sahara compared to the SAL: effective diameters of up to 20&#8201;&#181;m were observed over the Sahara compared to 4&#8201;&#181;m in the SAL. Excluding giant particles over the Sahara results in significant underestimation of mass concentration (40&#8201;%), as well as underestimates of both shortwave and longwave extinction (18&#8201;% and 26&#8201;%, respectively, from scattering calculations), while the effects in the SAL are smaller but non-negligible. The larger impact on longwave extinction compared to shortwave implies a bias towards a radiative cooling effect in dust models, which typically exclude giant particles and underestimate coarse-mode concentrations.A compilation of the new and published effective diameters against dust age since uplift time suggests that two regimes of dust transport exist. During the initial 1.5&#8201;d, both coarse and giant particles are rapidly deposited. During the subsequent 1.5 to 10&#8201;d, PSD barely changes with transport, and the coarse mode is retained to a much greater degree than expected from estimates of gravitational sedimentation alone. The reasons for this are unclear and warrant further investigation in order to improve dust transport schemes and the associated radiative effects of coarse and giant particles in models.This work has been recently published in ACP (Ryder, C. L., Highwood, E. J., Walser, A., Seibert, P., Philipp, A., and Weinzierl, B.: Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara, Atmos. Chem. Phys., 19, 15353&#8211;15376, https://doi.org/10.5194/acp-19-15353-2019, 2019).

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Lidar Measuremnt on Dust Transport from the Saharan Desert to the Iran Plateau

EPJ Web of Conferences ◽

10.1051/epjconf/202023702020 ◽

2020 ◽

Vol 237 ◽

pp. 02020

Author(s):

Hossein Panahifar ◽

Ruhollah Moradhaseli ◽

Hadi Bourzoie ◽

Mahdi Gholami ◽

Hamid Reza Khalesifard

Keyword(s):

Trajectory Analysis ◽

Saharan Dust ◽

Dust Particles ◽

Raman Lidar ◽

Dust Layer ◽

Mean Values ◽

Dust Transport ◽

Lidar Ratio ◽

532 Nm ◽

Iran Plateau

Optical properties of long-range Saharan dust particles transported to the Iran Plateau have been investigated. The results were derived from the measurements of a dual-wavelength Depolarized backscatter/Raman lidar and a Cimel CE318-2 sunphotometer. Observations were performed in Zanjan, Northwest Iran. The backward trajectory analysis show that the lofted dust plumes come from the Saharan desert and travel along Mediterranean Sea and Turkey toward Iran. The lidar ratio within the lofted dust layer has been found with mean values of 50 sr at 532 nm. For the depolarization ratio, mean values of 25% have been found.

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Saharan Dust Deposition Effects on the Microbial Food Web in the Eastern Mediterranean: A Study Based on a Mesocosm Experiment

Frontiers in Marine Science ◽

10.3389/fmars.2017.00117 ◽

2017 ◽

Vol 4 ◽

Cited By ~ 11

Author(s):

Paraskevi Pitta ◽

Maria Kanakidou ◽

Nikolaos Mihalopoulos ◽

Sylvia Christodoulaki ◽

Panagiotis D. Dimitriou ◽

...

Keyword(s):

Food Web ◽

Eastern Mediterranean ◽

Mesocosm Experiment ◽

Saharan Dust ◽

Microbial Food Web ◽

Dust Deposition

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Introduction to project DUNE, a DUst experiment in a low Nutrient, low chlorophyll Ecosystem

Biogeosciences ◽

10.5194/bg-11-425-2014 ◽

2014 ◽

Vol 11 (2) ◽

pp. 425-442 ◽

Cited By ~ 35

Author(s):

C. Guieu ◽

F. Dulac ◽

C. Ridame ◽

P. Pondaven

Keyword(s):

Atmospheric Deposition ◽

Surface Waters ◽

Wet Deposition ◽

Initial Conditions ◽

Sediment Traps ◽

Saharan Dust ◽

Dust Particles ◽

Dust Deposition ◽

Mesocosm Experiments ◽

Atmospheric Inputs

Abstract. The main goal of project DUNE was to estimate the impact of atmospheric deposition on an oligotrophic ecosystem based on mesocosm experiments simulating strong atmospheric inputs of eolian mineral dust. Our mesocosm experiments aimed at being representative of real atmospheric deposition events onto the surface of oligotrophic marine waters and were an original attempt to consider the vertical dimension after atmospheric deposition at the sea surface. This introductory paper describes the objectives of DUNE and the implementation plan of a series of mesocosm experiments conducted in the Mediterranean Sea in 2008 and 2010 during which either wet or dry and a succession of two wet deposition fluxes of 10 g m−2 of Saharan dust have been simulated based on the production of dust analogs from erodible soils of a source region. After the presentation of the main biogeochemical initial conditions of the site at the time of each experiment, a general overview of the papers published in this special issue is presented. From laboratory results on the solubility of trace elements in dust to biogeochemical results from the mesocosm experiments and associated modeling, these papers describe how the strong simulated dust deposition events impacted the marine biogeochemistry. Those multidisciplinary results are bringing new insights into the role of atmospheric deposition on oligotrophic ecosystems and its impact on the carbon budget. The dissolved trace metals with crustal origin – Mn, Al and Fe – showed different behaviors as a function of time after the seeding. The increase in dissolved Mn and Al concentrations was attributed to dissolution processes. The observed decrease in dissolved Fe was due to scavenging on sinking dust particles and aggregates. When a second dust seeding followed, a dissolution of Fe from the dust particles was then observed due to the excess Fe binding ligand concentrations present at that time. Calcium nitrate and sulfate were formed in the dust analog for wet deposition following evapocondensation with acids for simulating cloud processing by polluted air masses under anthropogenic influence. Using a number of particulate tracers that were followed in the water column and in the sediment traps, it was shown that the dust composition evolves after seeding by total dissolution of these salts. This provided a large source of new dissolved inorganic nitrogen (DIN) in the surface waters. In spite of this dissolution, the typical inter-elemental ratios in the particulate matter, such as Ti / Al or Ba / Al, are not affected during the dust settling, confirming their values as proxies of lithogenic fluxes or of productivity in sediment traps. DUNE experiments have clearly shown the potential for Saharan wet deposition to modify the in situ concentrations of dissolved elements of biogeochemical interest such as Fe and also P and N. Indeed, wet deposition yielded a transient increase in dissolved inorganic phosphorus (DIP) followed by a very rapid return to initial conditions or no return to initial conditions when a second dust seeding followed. By transiently increasing DIP and DIN concentrations in P- and N-starved surface waters of the Mediterranean Sea, wet deposition of Saharan dust can likely relieve the potential P and/or N limitation of biological activity; this has been directly quantified in terms of biological response. Wet deposition of dust strongly stimulated primary production and phytoplanktonic biomass during several days. Small phytoplankton (< 3 μm) was more stimulated after the first dust addition, whereas the larger size class (> 3 μm) significantly increased after the second one, indicating that larger-sized cells need further nutrient supply in order to be able to adjust their physiology and compete for resource acquisition and biomass increase. Among the microorganisms responding to the atmospheric inputs, diazotrophs were stimulated by both wet and dry atmospheric deposition, although N2 fixation was shown to be only responsible for a few percent of the induced new production. Dust deposition modified the bacterial community structure by selectively stimulating and inhibiting certain members of the bacterial community. The microbial food web dynamics were strongly impacted by dust deposition. The carbon budget indicates that the net heterotrophic character (i.e., ratio of net primary production to bacteria respiration < 1) of the tested waters remained (or was even increased) after simulated wet or dry deposition despite the significant stimulation of autotrophs after wet events. This indicates that the oligotrophic tested waters submitted to dust deposition are a net CO2 source. Nonetheless, the system was able to export organic material, half of it being associated with lithogenic particles through aggregation processes between lithogenic particles and organic matter. These observations support the "ballast" hypothesis and suggest that this "lithogenic carbon pump" could represent a major contribution of the global carbon export to deep waters in areas receiving high rates of atmospheric deposition. Furthermore, a theoretical microbial food web model showed that, all other things being equal, carbon, nitrogen and phosphorus stoichiometric mismatch along the food chain can have a substantial impact on the ecosystem response to nutrient inputs from dusts, with changes in the biomass of all biological compartments by a factor of ~ 2–4, and shifts from net autotrophy to net heterotrophy. Although the model was kept simple, it highlights the importance of stoichiometric constrains on the dynamics of microbial food webs.

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Sensitivity of the WRF-Chem (V3.6.1) model to different dust emission parametrisation: assessment in the broader Mediterranean region

Geoscientific Model Development ◽

10.5194/gmd-10-2925-2017 ◽

2017 ◽

Vol 10 (8) ◽

pp. 2925-2945 ◽

Cited By ~ 17

Author(s):

Emmanouil Flaounas ◽

Vassiliki Kotroni ◽

Konstantinos Lagouvardos ◽

Martina Klose ◽

Cyrille Flamant ◽

...

Keyword(s):

North Africa ◽

Eastern Mediterranean ◽

Dust Emission ◽

Model Performance ◽

Dust Particles ◽

Dust Transport ◽

Dust Emissions ◽

Extinction Coefficients ◽

Airborne Measurements ◽

Model Aerosol

Abstract. In this study we aim to assess the WRF-Chem model capacity to reproduce dust transport over the eastern Mediterranean. For this reason, we compare the model aerosol optical depth (AOD) outputs to observations, focusing on three key regions: North Africa, the Arabian Peninsula and the eastern Mediterranean. Three sets of four simulations have been performed for the 6-month period of spring and summer 2011. Each simulation set uses a different dust emission parametrisation and for each parametrisation, the dust emissions are multiplied with various coefficients in order to tune the model performance. Our assessment approach is performed across different spatial and temporal scales using AOD observations from satellites and ground-based stations, as well as from airborne measurements of aerosol extinction coefficients over the Sahara. Assessment over the entire domain and simulation period shows that the model presents temporal and spatial variability similar to observed AODs, regardless of the applied dust emission parametrisation. On the other hand, when focusing on specific regions, the model skill varies significantly. Tuning the model performance by applying a coefficient to dust emissions may reduce the model AOD bias over a region, but may increase it in other regions. In particular, the model was shown to realistically reproduce the major dust transport events over the eastern Mediterranean, but failed to capture the regional background AOD. Further comparison of the model simulations to airborne measurements of vertical profiles of extinction coefficients over North Africa suggests that the model realistically reproduces the total atmospheric column AOD. Finally, we discuss the model results in two sensitivity tests, where we included finer dust particles (less than 1 µm) and changed accordingly the dust bins' mass fraction.

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Saharan dust levels in Greece and received inhalation doses

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-7181-2008 ◽

2008 ◽

Vol 8 (23) ◽

pp. 7181-7192 ◽

Cited By ~ 65

Author(s):

C. Mitsakou ◽

G. Kallos ◽

N. Papantoniou ◽

C. Spyrou ◽

S. Solomos ◽

...

Keyword(s):

Urban Areas ◽

Particle Deposition ◽

Mineral Dust ◽

Pm10 Concentration ◽

Saharan Dust ◽

Anthropogenic Sources ◽

Dust Particles ◽

Annual Number ◽

Human Respiratory Tract ◽

Dust Transport

Abstract. The desert of Sahara is one of the major sources of mineral dust on Earth, producing around 2×108 tons/yr. Under certain weather conditions, dust particles from Saharan desert get transported over the Mediterranean Sea and most of Europe. The limiting values set by the directive EC/30/1999 of European Union can easily be exceeded by the transport of desert dust particles in the south European Region and especially in urban areas, where there is also significant contribution from anthropogenic sources. In this study, the effects of dust transport on air quality in several Greek urban areas are quantified. PM10 concentration values from stationary monitoring stations are compared to dust concentrations for the 4-year period 2003–2006. The dust concentration values in the Greek areas were estimated by the SKIRON modelling system coupled with embedded algorithms describing the dust cycle. The mean annual dust contribution to daily-averaged PM10 concentration values was found to be around or even greater than 10% in the urban areas throughout the years examined. Natural dust transport may contribute by more than 20% to the annual number of exceedances – PM10 values greater than EU limits – depending on the specific monitoring location. In a second stage of the study, the inhaled lung dose received by the residents in various Greek locations is calculated. The particle deposition efficiency of mineral dust at the different parts of the human respiratory tract is determined by applying a lung dosimetry numerical model, which incorporates inhalation dynamics and aerosol physical processes. The inhalation dose from mineral dust particles was greater in the upper respiratory system (extrathoracic region) and less significant in the lungs, especially in the sensitive alveolar region. However, in cases of dust episodes, the amounts of mineral dust deposited along the human lung are comparable to those received during exposure in heavily polluted urban or smoking areas.

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Saharan dust transport and deposition towards the tropical northern Atlantic

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-1173-2009 ◽

2009 ◽

Vol 9 (4) ◽

pp. 1173-1189 ◽

Cited By ~ 105

Author(s):

K. Schepanski ◽

I. Tegen ◽

A. Macke

Keyword(s):

Dust Emission ◽

Source Area ◽

Saharan Dust ◽

Dust Deposition ◽

Deposition Rates ◽

Dust Transport ◽

Tropical North Atlantic ◽

Different Seasons ◽

Northern Atlantic ◽

Dust Distribution

Abstract. We present a study of Saharan dust export towards the tropical North Atlantic using the regional dust emission, transport and deposition model LM-MUSCAT. Horizontal and vertical distribution of dust optical thickness, concentration, and dry and wet deposition rates are used to describe seasonality of dust export and deposition towards the eastern Atlantic for three typical months in different seasons. Deposition rates strongly depend on the vertical dust distribution, which differs with seasons. Furthermore the contribution of dust originating from the Bodélé Depression to Saharan dust over the Atlantic is investigated. A maximum contribution of Bodélé dust transported towards the Cape Verde Islands is evident in winter when the Bodélé source area is most active and dominant with regard to activation frequency and dust emission. Limitations of using satellite retrievals to estimate dust deposition are highlighted.

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