Saharan Dust Storms Research Articles

Investigations of the March 2006 African dust storm using ground‐based column‐integrated high spectral resolution infrared (8–13 μm) and visible aerosol optical thickness measurements: 2. Mineral aerosol mixture analyses

The mineral aerosol mixture composition for the March 2006 Saharan dust storm is assessed in this paper on the basis of the analysis of visible to near‐infrared (VIS‐NIR) and infrared (IR) aerosol optical thickness (AOT) spectra obtained during the Portable Infrared Aerosol Transmission Experiment (PIRATE). The AOT spectra from 8 to 13 μm were determined using column‐integrated solar transmission measurements using a Fourier transform infrared spectrometer. To determine the mineralogy and mixture composition of the dust, we determined the expected mineralogy of dust from the Algerian source region in a dust storm environment. Then we computed the modeled VIS‐IR AOT spectra using Mie theory for external and internal mixtures. We compared the modeled VIS‐NIR AOT spectra and derived index of refraction and single‐scattering albedo with the measured values from AERONET and compared the modeled IR AOT spectra with the values from our IR measurements. The fit between the measured and modeled values was best when we used an extinction resonance correction to the Mie theory results to better account for the exact wavelengths and shapes of some of the AOT peaks for mineral particles. The mineralogy and mixture composition of the best dust model includes external mixtures, internal mixtures, and mineralogy dominated by quartz, illite, and calcite. The modeled mean radius was determined, and several modes were computed in agreement with AERONET results.

Characterization of African Dust (PM 2.5) across the Atlantic Ocean during AEROSE 2004

An Aerosol and Oceanographic Science Expedition (AEROSE) on the NOAA Ship Ronald H. Brown collected PM 2.5 particles from a Saharan dust storm in March 2004. High levels of PM 2.5 (120 μg m −3) were measured during this Saharan storm over the Atlantic Ocean. The particles were characterized for trace element content, with Al and Fe the most abundant metals. These metals were detected in high concentrations during the Saharan event and exhibited good correlations with PM 2.5, suggesting its soil origin. Other elements (Pb, Ni, Cd) did not correlate with Al and Fe, indicating their anthropogenic origin. Enrichment factor calculation conducted on these trace elements support our findings. Trace element analyses performed on particulate matter from a reference site on land in Puerto Rico (Fajardo), demonstrated similar results to those obtained in the AEROSE expedition, where high concentrations of PM 2.5 and Fe were present concomitantly with Saharan events at this station.

The chemical composition and sources of the bulk deposition on Lake Kinneret (The Sea of Galilee), Israel

The chemical composition of the bulk deposition into Lake Kinneret, Israel was determined for the three hydrological years from 1992 to 1995. The fluxes of the elements and ions in the bulk deposition around the lake are fairly uniform although some local effects due to anthropogenic activity are observed; temporal effects are more pronounced. Na and Cl fluxes are greatly affected by rainfall that has passed over the Mediterranean Sea whilst Ca fluxes increase during dust storm episodes. The amount of each of the determined constituents entering the lake was calculated. The major chemical constituent entering the lake (except Ca) is SO4 whose main source is long-range transport from Europe. Enrichment factor analysis shows that the insoluble portion of the bulk deposition has the same characteristics as regional (and Saharan) dust storms, whilst the soluble portion is strongly affected by the marine environment. Significant additions to the previously known input of nitrogen and phosphorous enter the lake due to bulk deposition: 10% for nitrogen and 40% for phosphorous. The Pb content of the lake sediments correlates with Pb usage in petrol. Full experimental results are given in the electronic appendices.

Dust Storm Fallout: Tiniest Travelers Pose Greatest Infection Threat

Vol. 116, No. 3 EnvironewsOpen AccessDust Storm Fallout: Tiniest Travelers Pose Greatest Infection Threat Angela Spivey Angela Spivey Search for more papers by this author Published:1 March 2008https://doi.org/10.1289/ehp.116-a128bAboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit Dust isn’t just a nuisance—its ability to clog human airways and carry pathogens poses a human health problem. In the sub-Saharan region of Africa, the World Health Organization pinpointed dust storms exacerbated by the dry season and drought as a cause of outbreaks of meningococcal meningitis. Dust from Saharan storms can reach as far away as Florida, with particles smaller than 2.5 μm traveling the greatest distances. Studies have shown that human exposure to these tiny particles is associated with human mortality, and new research now shows that such particles are also more likely to carry health-threatening bacteria [EHP 116:292–296; Polymenakou et al.].During a strong Saharan dust storm in 2006, researchers collected air samples in Heraklion, Crete, an area that often feels the effects of such storms. Particles from the samples were separated according to size (> 7.9 μm, 3.3–7.9 μm, 1.6–3.3 μm, 1.0–1.6 μm, 0.55–1.0 μm, or <0.55 μm) using a machine called a high-volume cascade impactor. The researchers characterized the bacteria traveling on particles of various sizes by taking samples from the machine’s filters, then cloning and sequencing a strand of DNA commonly used to identify bacteria. This process created an inventory of the bacterial gene sequences present in each of the six particle-size ranges. The creation of large clone libraries allows investigators to detect bacteria that are missed using culture methods, as some bacteria are difficult to grow.The researchers identified clones that were genetically related to pathogens linked to human diseases such as pneumonia, meningitis, and bacteremia, or to pathogens suspected of inducing infections such as endocarditis. Of the sequenced clones related to bacteria that are dangerous to humans, almost half (43%) were found at particle sizes less than 3.3 μm. Spore-forming bacteria such as Firmicutes dominated the particle sizes larger than 3.3 μm. Most of these bacteria are nonpathogenic.The authors conclude that the prevalence of breathable bacteria on small dust particles may pose a significant, widespread health risk to humans, given that dust, especially the smallest particles, is known to travel across continents. To determine just how much of a threat these tiny travelers pose, long-term studies are needed to further investigate how pathogens are distributed across dust particle size, and the distances these pathogens can travel and still survive.The dust storm that provided samples for Polymenakou et al. obscures the eastern Mediterranean Sea, 25 February 2006FiguresReferencesRelatedDetails Vol. 116, No. 3 March 2008Metrics About Article Metrics Publication History Originally published1 March 2008Published in print1 March 2008 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Saharan dust storm detection using moderate resolution imaging spectroradiometer thermal infrared bands

This paper investigates the approaches of Saharan dust storm detection with the Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared bands and presents an index, thermal-infrared dust index, through quantitative analysis of MODIS data for major dust events over the Atlantic Ocean during year 2004-2006. It is found that aerosol optical thickness (AOT) at 550nm has close relationships with the brightness temperature of MODIS bands 20, 30, 31, and 32. The proposed thermal-infrared dust index matches MODIS AOT very well with a squared correlation coefficient of 0.7646. Case study and statistical analysis suggest the potential to use 1km thermal-infrared dust index data for detecting dust storms and evaluating the potential impacts of regional weather, such as Atlantic hurricanes, and climate in the near future.

CHIKUNGUNYA FEVER RESURGENCE AND GLOBAL WARMING

CHIKUNGUNYA FEVER RESURGENCE AND GLOBAL WARMING

Observations of the impact of a major Saharan dust storm on the atmospheric radiation balance

Saharan dust storms have often been observed from space, but the full impact on the Earth's radiation balance has been difficult to assess, due to limited observations from the surface. We present the first simultaneous observations from space and from a comprehensive new mobile facility in Niamey, Niger, of a major dust storm in March 2006. The results indicate major perturbations to the radiation balance both at the top of the atmosphere and at the surface. Combining the satellite and surface data, we also estimate the impact on the radiation balance of the atmosphere itself. Using independent data from the mobile facility, we derive the optical properties of the dust and input these and other information into two radiation models to simulate the radiative fluxes. We show that the radiation models underestimate the observed absorption of solar radiation in the dusty atmosphere.

Assessing the effect of a Saharan dust storm on oxygenated organic compounds at Izaña, Tenerife (July–August 2002)

In July–August 2002 the field measurement campaign Mineral Dust and Tropospheric Chemistry (MINATROC) was carried out at the Global Atmosphere Watch station at Izaña, Tenerife, to study the interaction of mineral dust aerosol and tropospheric chemistry. Organic trace gas mixing ratios were determined for the following: alkanes (e.g., propane); alkenes (isoprene); aromatic compounds (toluene); and oxygenated species (CO, methanol, formaldehyde, acetaldehyde, and acetone) simultaneously with aerosol measurements of dust. Local emissions of biogenic (isoprene and methanol) and anthropogenic compounds (CO and toluene) were observed at Izaña by day. Nighttime mixing ratios of organic species were interpreted as representative of the Atlantic free troposphere. A local production and loss budget for formaldehyde suggested that isoprene dominates production by day, and a significant dry deposition velocity is estimated at night of 0.74 cm/s. The total reactivity of the organic trace gases measured to OH is estimated as 1.7 s−1 by day and 0.7 s−1 by night. During the campaign a dense Saharan dust plume, with aerosol masses exceeding 500 μg m−3, persisted for 3 days. Air masses containing dust appeared to be generally more polluted (in acetone and CO) than the prevailing westerly flow, but local biogenic emissions were little affected (e.g., methanol and isoprene). Although during the dust period the daily cycles and the absolute concentrations of some oxygenated species are different (e.g., acetaldehyde), these changes could not be attributed unequivocally to heterogeneous reactions on dust.

Characterization of fine particle sources in the Great Smoky Mountains area

A source apportionment study to characterize sources of fine particles in the Great Smoky Mountains area was conducted analyzing ambient PM2.5 (particulate matter≤2.5 μm in aerodynamic diameter) speciation data collected at a Interagency Monitoring of Protected Visual Environments (IMPROVE) monitoring site. A total of 1442 samples collected between March 1988 and December 2003 analyzed for 30 elemental species were analyzed with the application of the positive matrix factorization (PMF). Eight major sources were extracted: summer-high secondary sulfate (55%), carbon-rich secondary sulfate (16%), summer-low secondary sulfate (2%), gasoline vehicle emissions (13%), diesel emissions (1%), airborne soil (6%), industry (5%), and secondary nitrate (2%). The contributions from the carbon-rich secondary sulfate particles are likely a combination of local and regional influences of the biogenic as well as anthropogenic secondary particles. The compositional profiles for gasoline vehicle and diesel emissions are similar to those identified in other US areas. Backward trajectories indicate that the high impacts of airborne soil were likely caused by Asian and Saharan dust storms. This study would assist in the implementation plan development for attaining the air quality standards for PM2.5, regional haze rule planning, and source-specific community epidemiology.

Source identification for fine aerosols in Mammoth Cave National Park

In this study, positive matrix factorization (PMF) was applied to the chemical composition data of the ambient PM 2.5 collected at the Mammoth Cave National Park, an IMPROVE site in Kentucky. Eight individual carbon fractions, four organic carbons (OCs), pyrolyzed organic carbon (OP) and three elemental carbons (ECs), were provided to the analysis. Nine sources including the well-distinguished gasoline emission and diesel emission were identified. Also, the back trajectories indicated the crustal factor in this study were likely caused by Saharan dust storms in the summer. The apportionment of nine sources was: gasoline emission (6.7%), diesel emission (3.1%), summer secondary sulfate (49.0%), winter secondary sulfate (0.6%), OP-rich secondary sulfate (16.2%), secondary nitrate (2.8%), Intercontinental dust plus soil (4.9%), wood smoke (13.6%), and aged sea salt (3.2%). The results of this study will help regularize the pollution control strategies in rural areas of Kentucky and upper mid-western US while demonstrating the feasibility of applying carbon fractions to the source apportionment of rural upper-Midwestern areas.

Response of East Mediterranean surface water to Saharan dust: On-board microcosm experiment and field observations

Abstract An on-board microcosm experiment was performed during the CYCLOPS May 2002 cruise to track the biogeochemical response of Eastern Mediterranean surface seawater to a gradient addition of fresh and pre-leached Saharan dust, mimicking the potential fertilization effect as opposed to the impact of adding particles alone. Response parameters examined were P-turnover time, bacterial production and abundance, chlorophyll a, other phytopigments, abundance of different pico and nanophytoplankton groups, primary production rates, abundance of heterotrophic nanoflagellates and ciliates. The addition of fresh Saharan dust (range: 0.2– 4.9 mg l - 1 ) and the subsequent nutrient release triggered an increase in phytopigments and primary production, while no response was detected for pre-leached dust particles. Most responses were linearly related to the amount of fresh dust added. Synechococcus and prymnesiophytes increased in abundance along with cellular pigment content while Prochlorococcus disappeared, heterotrophic bacteria increased production rates, and ciliates showed a small increase in cell density. A less clear response was recorded by in situ measurements following a Saharan dust storm during a cruise in the Levantine Basin in May 2001. The calculated amount of nutrients and dust particles delivered by such an event to a 15-m thick mixed surface layer is low ( ∼ 0.3 nmol P l - 1 , ∼ 9 nmol N l - 1 and 0.06 mg dust l - 1 ) , falling close to the lowest dust addition in our microcosm experiment. Even so, an enhancement of phosphate turnover time, a sharp decline of Prochlorococcus abundance, and slight increases in chlorophyll a and bacterial activity were observed in response to the dust storm. Considering the linear effect of fresh dust concentrations on the bacterial activity, primary production and pigment concentration (total and per cell), and the likely stimulation of grazing, it is not surprising that changes due to moderate strength dust storms are mostly close to detection limit of either field or remote sensing measurements.

Organic-walled dinoflagellate cyst production in relation to upwelling intensity and lithogenic influx in the Cape Blanc region (off north-west Africa)

SUMMARY Fossil dinoflagellate cyst assemblages are increasingly used in paleoclimatic research to establish paleoenvi-ronmental reconstructions. To obtain reliable reconstructions, it is essential to know which physical factors influence the cyst production. Most information about the relationship between variations in physical parameters and cyst production is known from middle and higher latitudes. Information from the (sub)tropics is rare. To increase this information, the temporal variation in cyst assemblages from the upwelling area off north-west Africa (off Mauritania) has been compared to environmental conditions of the upper water column. Samples were collected by the sediment trap CB9, off north-west Africa (Cape Blanc, 21°15′2″N, 20°42′2″W) between 11 June 1998 and 7 November 1999 at 27.5-day intervals. Off Cape Blanc, upwelling occurs throughout the year with variable intensity. This region is also characterized by frequently occurring Saharan dust storms. Seasonal variations in dust input, upwelling intensity and sea surface temperature are reflected by the production of organic-walled dinoflagellate cyst assemblages. Several cyst taxa are produced throughout the sampling interval, with the highest fluxes at times of strongest upwelling relaxation and/or dust input (Echinidinium aculeatum Zonneveld, Echini-din ium delicatum Zonneveld, Echinidinium granulaturn Zonneveld, Echinidinium spp., Impagidinium aculeatum (Wall) Lentin et Williams, Impagidinium sphaeri-cum (Wall) Lentin et Williams, Protoperidinium americanum (Gran et Braarud) Balech, Protoperidinium stellatum (Wall in Wall et Dale) Rochon etal., Protoperidinium spp., Selenopemphix nephroides (Benedek) Benedek et Sarjeant and Selenopemphix quanta (Bradford) Matsuoka). Species such as, for example, Bitectatodinium spongium (Zonneveld) Zonneveld et Jurkschat and Impagidinium patulum (Wall) Stover et Evitt do not show any production pattern related to a particular season of the year or to specific environmental conditions in the upper water column. The production of cysts of Protoperidinium monospinum (Paulsen) Zonneveld et Dale is restricted to intervals with increased nutrient concentrations in upper waters when sea surface temperatures at the sampling site is below approximately 24°C.

Sources of Fine Particles in a Rural Midwestern U.S. Area

Ambient PM2.5 (particulate matter < or = 2.5 microm in aerodynamic diameter) samples collected at a rural monitoring site in Bondville, IL on every third day using Interagency Monitoring of Protected Visual Environments (IMPROVE) sampler were analyzed through the application of the positive matrix factorization (PMF). The particulate carbon fractions were obtained from the thermal optical reflectance method that divides particulate carbon into four organic carbon, pyrolyzed organic carbon (OP), and three elemental carbon fractions. A total of 257 samples collected between March 2001 and May 2003 analyzed for 35 species were used and eight sources were identified: summer-high secondary sulfate aerosol (40%), secondary nitrate aerosol (32%), gasoline vehicle (9%), OP-high secondary sulfate aerosol (7%), selenium-high secondary sulfate aerosol (4%), airborne soil (4%), aged sea salt (2%), and diesel emissions (2%). The compositional profiles for gasoline vehicle and diesel emissions are similar to those estimated in other U.S. areas. Backward trajectories indicate that the highly elevated airborne soil impacts were likely caused by Asian and Saharan dust storms. Potential source contribution function analyses show the potential source areas and pathways of secondary sulfate aerosols, especially the regional influences of the biogenic as well as anthropogenic secondary aerosol.

Contribution of dust transport and resuspension to particulate matter levels in the Mediterranean atmosphere

Abstract A sampling site at Herceg-Novi (Montenegro) is included in the network for the monitoring of airborne pollutants along the Mediterranean coast. The 24-h concentrations of total suspended particles (TSP) were measured by a standardized gravimetric method in a 1-in-6 day schedule program. The available data set from the period 1995–2000 was chosen for statistical analysis. The 3-parameter Weibull probability model successfully described the distributions of TSP concentrations as the total population and the part of them transported from the continental side. However, in the concentration set from the southern segment, outliers were found indicating the appearance of the highest concentrations from the open Adriatic Sea. The collected particles mostly constituted of PM10 and the ratio PM10/TSP reached value of 0.9. An analysis of the filter samples by scanning electron microscopy (SEM) confirmed the presence of marine aerosol, crustal and amorphous material. The Fe content of >2% in the TSP samples was accepted for the identification of genuine Saharan dust transport. The frequency of these events of 7% a year contributed to an increase of the annual TSP concentrations of 10%–15%. The amorphous material was found in the sample of 31 May/1 June 1999 after the bombing of Cape Arza on the Lustica Peninsula, which is situated 5 km away from the sampling site. The attack occurred on 30 May and depleted uranium ammunition was used. The 238U radioactivity was at the background level, but the pulverous material found in that sample most likely originated from dust and soil transported from Cape Arza to Herceg-Novi on 31 May as the backward trajectory analysis by the Eta model showed. Resuspension was the dominant process affecting the TSP concentration, but this episode did not reflect significantly on the annual TSP levels, as is the case with the Saharan dust storms. The methodology applied in this work allowed a fugitive source of PM from destroyed objects and bombed terrain to be discovered.

Analysis of the Saharan dust regional transport

The Balkan Peninsula is situated in the impact zone of Saharan dust storms. The case of Saharan dust transport to Belgrade in the period of 14–17 April 1994 is analyzed using the Eta model for synoptic and meso scale processes. Air back trajectories are calculated at six model levels from 434 up to 5129 m with horizontal grid resolutions of 1°×1° and 10′×10′. Following cyclonic circulation the dust was picked up from North Africa, and transported over Mediterranean. Simultaneously, according to the analysis of the three lowest trajectories, transport of trace metals from Macedonia and southern Serbia by the Koshava wind might be dominant in the observed episode. Turbulent flow enhanced the coagulation process of initially clean dust particles with particles containing Pb and Cd. The coagulation and scavenging processes below and in clouds increased deposition rates of Pb and Cd in Belgrade in the course of wet removal, and consequently trough resuspension processes. Dry deposition samples contained characteristic particles up to 30 µm in diameter with Fe content of 11 to 15 atomic% and significant ratio Si/Fe of 3 to 5, determined for selected single particles by the SEM/EDX method. Following dry and wet deposition of Cd and Pb, a residual effect of dustfall is noticed throughout the vegetational period.

Saharan dust storms and indirect aerosol effects on clouds: CRYSTAL‐FACE results

A recent field experiment in southern Florida using aircraft and polarization lidar shows that mineral dust particles transported from Saharan Africa are effective ice nuclei, apparently capable of glaciating a mildly supercooled (−5.2° to −8.8°C) altocumulus cloud. These results are similar to those from Asian dust storm particles observed over the western US, suggesting that in the northern hemisphere major dust storms play a role in modulating climate through the indirect aerosol effect on cloud properties. If this is true of desert dusts in general, then even minor aeolian emissions could have an effect on regional weather and climate.

Saharan dust storms over the Canary Islands during winter 1998 as depicted from the advanced very high-resolution radiometer

One of the largest Saharan dust outbreaks of the decade, over the Canarian Archipelago, took place between January and March 1998. A series of advanced very high-resolution radiometer (AVHRR) images corresponding to this event were studied to characterize short-term (days) variability of aerosol atmospheric load. Multispectral radiometric performance of this type of aerosol was analysed to define a classification strategy for dust detection. Optical parameters related to size distribution were calculated from the images. The monitoring of the Angstrom exponent during this event shows how its variability is correlated to the short-term history of the aerosols. Assuming that Saharan aerosol behaves optically as a typical Junge size distribution, the variance of the Angstrom exponent is interpreted in terms of the variability in the particle size distribution and related to intesifications and relaxations of dust conditions.

Chemical characteristics of atmospheric aerosols in a rural site of northwestern Anatolia

Aerosol samples were collected daily at a rural mountainous site of northwestern Anatolia during September 1993–April 1994. Concentrations of SO 4 2−, NO 3 −, Cl −1, NH 4 +, Na +, K +, Ca 2+ and Mg 2+ have been determined. Sulfate made up the 30% analyzed aerosol mass with a 2.14 μm −3 average concentration. Measured concentrations were comparable with other rural area data except Ca 2+ which was higher in our station with an average concentration of 1.12 μg m −3 Monthly concentrations of major ions fluctuate depending on meteorological factors, seasons and source strengths. Saharan dust storms affected the sampling site especially in autumn and spring seasons. Wind sector analysis indicated that the most important source regions were located both to the south and north of the station. However, air masses from southerly direction at which a power plant is located have been concluded to bring the greatest amount of anthropogenic pollutants to the sampling site.

Determination of elemental composition of settling particles in Israel following Saharan dust storms by neutron activation analysis

Several cases of transporation and deposition of settling particles following dust storms over Israel, occurring between 1973 and 1987, were experimentally investigated. The storm particles were collected in Jerusalem and Ramat Hasharon, north of Tel Aviv. Meteorological conditions during the storms were examined and classified according to their trajectories into two types: (a) North African and (b) Arabian Desert. The North African type is by far the most common. In the present work, the concentrations of 26 elements (Al, Ba, Br, Ca, Ce, Co, Cl, Cr, Eu, Fe, Hf, K, La, Mg, Mn, Na, Rb, Sb, Sc, Si, Ta, Th, Ti, U, V, and Yb) in settling particles were determined by instrumental neutron activation analysis. The validity of the method was checked by analyzing U.S. NBS Standard Reference Material SRM-1633a; the elemental content found agreed well with the published certified data. Since Al as well as Si were determined through the reactions27Al(n, γ)28Al(2.24 min) and28Si(n, p)28Al, respectively, thermal and epithermal neutron activation was applied in order to determine the contribution of silicon to the total28Al activity. Interpretation of the chemical analyses using Enrichment Factors reveals that settling particles are relatively enriched in Ca probably from the local terrain and in Cl derived from the Mediterranean Sea.

Modelling the biogenic transport of atmospheric particles in the Medittrranean Sea

To help the assessment of the geochemical impact of sporadic events such as Saharan dust storms on the biogeochemical cycles of trace elements in the Mediterranean Sea, a one-dimensional multilayered model of tre transport af atmospheric particles in the water column was developed. The model used data of the DYFAMED programme. Particulate aluminium was taken as a tracer of mineral particles. The Al atmospheric-source function was based on time-series data obtained at a coastal station in the Ligurian Sea. The response time throughout the water column was modulated by zooplankton grazing and water stratification. Stratification varies during the course of the year and induces variations of the eddydiffusivity coefficients which were calculated for the surface and deep layers. Runs of the model over one year displayed strong seasonal variations in particulate aluminium concentration and flux which agree with experimental data. Saharan dust events may happen at any time during the year but are often seen during the spring time. When they occur simultaneously with high biological activity, a rapid transport of the dust (within a few days) to the 200-m level is observed. When biological activity is low, the short-term effect is first a strong increase of suspended-aluminium concentrations followed by an export flux to deep waters, delayed by several weeks: the temporal pattern of the dust flux throughout the water column however, is primarily related to changes in primary productivity. Nevertheless, temporal changes of the particulate flux out of the euphotic zone are also afearly affected by the intensity and duration of the dust storm. Thus, the higeest values of particulate flux occur as a consequence of the removal of dust particles from the surface layer when biological activity is high. Finally the model indicates that during autumn and early winter, vertical mixing can be a dominant factor in the removal of atmospheric particles from the upper water column.