Evaluation of minerals being deposited in the Red Sea using gravimetric, size distribution, and mineralogical analysis of dust deposition samples collected along the Red Sea coastal plain

The effect of atmospheric dust on the Earth's climate and air quality is especially severe in the major dust-source regions of the globe, such as the Arabian Peninsula. To better quantify the impact of dust over this region, we established the dust deposition measurement sites at King Abdullah University of Science and Technology (KAUST) and an AErosol RObotic NETwork (AERONET) station. We measured and analyzed dust deposition for 61 months from 2014 to 2019, totaling 442 samples, in 6 different locations on the KAUST campus (22.3 N; 39.1E). The analyses include gravimetric measurements, X-Ray Diffraction (XRD) mineral analyses, and particle size distribution measurements. The intercomparisons of the samples collected from different sampling sites show that the dust deposition rates on campus are spatially uniform. Particle size and mass measurements of deposition dust samples are found to be uncorrelated with the concurrent AERONET measurements. Deposition sample sieving (D < 56 µm), applied since May 2019, make the measurements more consistent but do not significantly affect particles' size distribution with diameters D < 20 μm. Large particles with D > 20 µm are typically of local origin, since they deposit quickly. The annual mean deposition rate is about 11 g m-2 mo-1, with higher spring and fall rates and reduced rates in summer. The mineralogical analysis shows an abundance of quartz and feldspar with lesser amounts of micas, gypsum, clays, carbonate, halite, and iron oxides. Gypsum traces are probably produced either in the atmosphere or in the deposited sample by the reaction between carbonates and sulfur dioxide. The deposition of dust particles with D < 20 µm in the Red Sea totals 8.6 Mt annually. This comprises 1.05 Mt of quartz, 0.88 Mt of feldspars, 0.22 Mt of carbonates, 1.39 Mt of clays, and 0.06 Mt of hematite, which plays a vital role in maintaining the Red Sea nutrient balance.