Mineral Dust Deposition Research Articles

Mineral dust concentrations, deposition fluxes and deposition velocities in dust episodes over Israel

Total suspended particles (TSP) and dustfall were simultaneously sampled in Jerusalem (1969–1973) and in Tel Aviv (1976–1995) to determine the deposition flux, particle concentration, and deposition velocity of the mineral dust. In addition, the deposition flux of dustfall was measured throughout Israel and in the Sinai Desert during the years 1970–1973. TSP concentrations during dust pulses (“episodes”) were from 10 to 120 times higher than the background values of ∼100 μg m−3; the maximum concentration measured was 24,000 μg m−3. The annual deposition flux (from pulses only) decreased from 90 g m−2 yr−1 in the south to 30 g m−2 yr−1 in the north. The local contribution to the annual deposition flux was ∼50% in the south and near the Judean Desert in the east but decreased to 25% in the north. Deposition velocities of the dustfall during months without dust episodes were on the order of 1.0 cm s−1, while during months when dust storms occurred, deposition velocities are from 2 to 6 times greater than the background, depending on the location. Monthly mean deposition velocities during dust episodes varied between 2.6 cm s−1 and 9.0 cm s−1; short term (1 hour) values up to 27 cm s−1 have been measured.

An autonomous aerosol sampler/elemental analyzer designed for ocean buoys and remote land sites

An autonomous aerosol sampler/elemental analyzer, that employs energy dispersive X-ray fluorescence spectrometry to determine the elemental (Fe, Si, S, Ca and K) concentrations of aerosols in near real time, has been designed, built and successfully tested on a roof. The ultimate technical goal is to deploy a buoy-mounted aerosol sampler/analyzer in order to make the long-term measurements necessary to quantify the deposition of mineral dust to the oceans. A major scientific goal is to address the question of enhanced biological production due to the release of dissolved iron from the deposition of mineral dust. Design and operating features are discussed and illustrated. This instrument has the sensitivity to measure the concentrations of mineral dust and Fe over the oceans with a time resolution of a few days during periods of moderate to high dust deposition.

An illustration of the transport and deposition of mineral dust onto the eastern Mediterranean

The analyses of aerosol samples and deposition (wet) measurements during August 1991–December 1992 at Erdemli (36°N, 34°E) located on the Turkish coast of the eastern Mediterranean has shown higher dust concentration and total deposition during transitional seasons (spring and autumn) compared to summer and winter seasons. The data, complemented by three-dimensional (3D) air mass back trajectories and satellite observations suggest that North African and Middle East desert derived dust particles are transported to the region during transitional seasons. Transport events in the last part of March 1992 and early October 1992 are studied through combined analyses of ground based and satellite observations and modelling results. It is shown that dust transport constitutes a large fraction of the annual atmospheric deposition in the eastern Mediterranean, with two deposition events of short duration accounting up to 30% of the total annual flux. Therefore, the dissolved and particulate species associated with dust could be extremely variable in the mixing layer during large deposition events and could easily be missed in a short-term sampling program. The possible impact of large pulses on biological productivity of the sea also warrants consideration.

Aeolian sources of rare earth elements to the Western Pacific Ocean

Abstract Rare earth element (REE) determinations have been made on 25 surface seawater samples on a longitudinal transect from Asia to North America within a latitudinal band of 24–32°N. REE concentrations are significantly higher close to Asia and decrease to the lowest recorded for surface waters in the world's oceans at the 180° International Dateline. REE patterns also vary systematically and near Asia are similar to patterns for Chinese Loess. Thus, contrary to previous inferences based on Nd isotopes, atmospheric deposition of mineral dust from the Asian continent significantly affects the REE composition of western Pacific Ocean sea water.

The distributions of particulate atmospheric trace metals and mineral aerosols over the Indian Ocean

Abstract Data are presented for the concentrations of Al, Fe, Mn, Ni, Co, Cr, V, Cu, Zn, Pb and Cd in aerosols collected over two contrasting regions of the Indian Ocean. These are: (1) the northern Arabian Sea (AS), from which samples were collected in the northeast monsoon, during which the region receives an input of crustal material from the surrounding arid land masses; and (2) the Tropical Southern Indian Ocean (TSIO), a remote region from which samples were collected from air masses for which there were no large-scale up-wind continental aerosol sources. The TSIO samples can be divided into two populations: Population I aerosols, collected from air masses which have probably impinged on Madagascar, and Population II aerosols, which have been confined to open-ocean regions to the south of the area. The data indicate that there are strong latitudinal variations in the chemical signatures of aerosols over the Indian Ocean. The input of crustal material to the Arabian Sea gives rise to an average Al concentration of about 1000 ng m −3 of air in the northeast monsoon regime. As a result, the concentrations of all trace metals are relatively high, and the values of crustal enrichment factors are less than 10 for most metals, in the AS aerosols. In contrast, TSIO Population II ‘open-ocean southern air’ sampled during the southwest monsoon season, has an average Al concentration of only about 10 ng m −3 of air. Trace metal concentrations in the TSIO ‘open-ocean southern air’ during the southwest monsoon season are representative of ‘clean’ remote marine air and are generally similar to those reported over the central North Pacific. Mineral dust concentrations over the Indian Ocean decrease in a north to south direction, from about 15–20 μg m −3 of air in the extreme north to about 0.01–0.25 μg m −3 of air in the far south. The deposition of mineral dust over the northern Arabian Sea can account for approximately 75% of the non-carbonate material incorporated into the underlying sediments. In the Arabian Sea the dissolved atmospheric inputs of all the trace metals, with the exception of Cu and Co, exceed those from fluvial run-off by factors which range from 9.6 for Pb to 1.6 for Cr.

Dry deposition of Asian mineral dust over the central North Pacific

Dry deposition of mineral particles was investigated on the windward coast of Oahu (Hawaii) using a surrogate surface technique. The collected particles were analyzed microscopically for the number of particles in different size classes. These data were used to estimate deposition rates to the deposition plate. Relating these fluxes to the corresponding concentrations of mineral particles in air, mean dry deposition velocities were determined. For the size classes 2–4, 4–8, and 8–15 μm these were 0.3, 1.2, and 2.6 cm s−1, respectively. Additionally, the dry deposition velocity curve in the range between 2 and 15 μm was determined on the assumption that the mineral particle mass size distributions in the air and in dry deposition were lognormal. This curve was compared with theoretical data calculated by a model for the deposition of particles to the sea surface. The discrepancies, in particular for smaller particles, are probably due to the different deposition conditions at the sea surface and the deposition plate. Also, the aggregates that were found in some samples and which consist of sea salt and mineral particles will affect the experimentally derived dry deposition curve.

Antibody producing cells in the spleens of mice treated with pathogenic mineral dust.

Experiments were carried out to assess the effect of intraperitoneal injection of the mineral dusts, titanium dioxide, quartz, or asbestos, on splenic lymphocyte antibody forming cells in immunised mice. Titanium dioxide and quartz caused similar, about one third, reductions in plaque forming cells; asbestos caused substantial reduction to about a quarter of the number found in control spleens. The inhibition of antibody forming cells in the spleen found with chrysotile was dose dependent and both chrysotile and crocidolite asbestos were similar in activity. Systemic immunomodulation after local deposition of mineral dust may be important to the development of disease.

Seasonal and areal variation of continental aerosol in the surface air over the western North Pacific region

Weekly aerosol samples were collected for two years from 1981 at six stations in the western North Pacific region. The samples were analyzed for aluminum to determine the mineral dust concentration in the air. By combining our data with observations in the central and eastern North Pacific by a US research group, the following results and conclusions have been obtained. Spring peaks in atmospheric mineral dust were observed at all the stations accompanied byKosa episodes (hazes due to mineral dust of Chinese origin). The spring peaks, however, varied from year to year. The mean concentration of mineral dust depends not only on the distance from the Asian coast but also on the latitude of the sampling station. The half-decrease distance of the atmospheric mineral dust turned out to be 500–600 km for all latitudes in the western North Pacific. This indicates that the rate of deposition of mineral dust in the western North Pacific is much larger than that in the central and eastern North Pacific.

The detection of etiologic agents in interstitial pulmonary fibrosis

A multiplicity of etiologic factors can induce interstitial pulmonary fibrosis. A number of cases are associated with the inhalation and deposition of mineral dust and fumes. Many of these are apparently not related to occupational environmental pollution. Systematic investigations of lung tissue (autopsy and biopsy material) from patients suffering from interstitial pulmonary fibrosis of primarily unknown causes often discloses the presence of small amounts of mineral deposits. The methods used for the detection and identification of these substances in isolated lung dust and in thin tissue sections include electron microscopy, electron and x-ray diffraction, and x-ray fluorescence and infrared spectroscopy.