Magnetic signatures of natural and anthropogenic sources of urban dust aerosol

Abstract

Abstract. The characteristics of urban dust aerosols and the contributions of their natural and anthropogenic sources are of scientific interest as well as being of substantial sociopolitical and economic concern. Here we present a comprehensive study of dust flux, magnetic parameters, magnetic particulate morphology, and elemental compositions of atmospheric dustfall originating from natural dust sources in East Asia and local anthropogenic sources in Xi'an, China. The results reveal a significant inverse relationship between seasonal variations of dust flux and magnetic susceptibility (χ). By comparing dust flux and χ records, the relative contributions of dust from local anthropogenic sources are estimated. Analyses using scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) indicate that magnetic particulate from different sources has distinct morphological and elemental characteristics. Detrital magnetic particles originating from natural sources are characterized by relatively smooth surfaces with Fe and O as the major elements and a minor contribution from Ti. The anthropogenic particles have angular, spherical, aggregate, and porous shapes with distinctive contributions from marker elements, including S, Cr, Cu, Zn, Ni, Mn, and Ca. Our results demonstrate that this multidisciplinary approach is effective in distinguishing dust particles derived from distant natural sources and local anthropogenic sources and for the quantitative assessment of contributions from the two end-members.

PM2.5 Magnetic Properties in Relation to Urban Combustion Sources in Southern West Africa

“…All sites present iron oxides, among soot and/or aggregates containing crustal elements (Al, Ca, K, Zr), sea salt (Na, Cl) and elements from anthropogenic activities (S, Pb) [65] detected via magnetic and microscopic methods (Figure 7). The detected fly-ash spherules are a marker of anthropogenic combustion emissions, on the sub-micron size range (Figure 7).…”

Orbital climate variability on the northeastern Tibetan Plateau across the Eocene–Oligocene transition

“…Finally, the flat polished specimens were coated with a gold layer using an evaporative coater. The polished magnetic extract specimens were then used to determine the morphology of individual particles (including shape and size distributions) and their mineral compositions using the SEM-EDS system 69,70 . Each backscattered electron (BSE) image was obtained with an accelerating voltage of 20 kV and a beam current of 100 μA.…”

Dust-Dominated Coarse Particles as a Medium for Rapid Secondary Organic and Inorganic Aerosol Formation in Highly Polluted Air

“…Field studies on SA formation mostly focused on fine particles (PM 1 ) partly because of instrument limitations, while that formed on coarse particles was mostly neglected unless upon the occurrence of dust storms. However, dust (both natural and anthropogenically emitted dust) is constantly present in the atmosphere , and is one of the largest contributors to aerosol mass in the troposphere, exerting a significant impact on global climate by modulating radiative balance. Freshly emitted dust particles mainly consist of aluminosilicate, SiO 2 , CaCO 3 , and so forth, while aged dust particles are usually coated with secondary organic and inorganic aerosol components under an ambient environment, − for example, ammonium (NH 4 + ), sulfate (SO 4 2– ), nitrate (NO 3 – ), and secondary organic aerosols (SOAs) because dust can serve as reactive surfaces for atmospheric trace gases and hence might have significant impacts on atmospheric chemistry. − …”