Thematic Articles

Global dust events have been part of much of Earth’s history. As in the geological past, mineral dust deflated off weathered crustal material in arid regions is continually being lofted kilometres into the atmosphere, where it circles the globe until physical and chemical processes favour precipitation in the ocean or on land. Mineral dust aerosols affect the environment both directly and indirectly by impacting the chemical and physical properties of the atmosphere and by interfering with biogeochemical cycles, all on a global scale. The most important source regions of dust are all in the Northern Hemisphere and include North Africa, the Middle East, the northwestern Indian subcontinent, central Asia, and northwestern China.

Volcanic emissions consist of a mixture of gases, aerosol, and silicate particles, which collectively span seven orders of magnitude in size. Airborne ash and sulfate aerosol in the lower atmosphere has shortlived atmospheric and climatic effects. Volcanic aerosol injected high into the stratosphere impacts atmospheric chemical cycles and the solar and terrestrial radiation budgets, and may influence climate over longer timescales than aerosol particles in the lower atmosphere. Once at the surface, the impacts on local environments can be substantial through transport of halogens, trace metals, and metalloids, and subsequent leaching in aqueous solutions. Volcanic emissions may cause disruption to travel and aviation, and may damage surface infrastructure, potentially causing large economic losses.

Particulate matter is an important constituent of our atmosphere and has a critical impact on natural processes and human health. Although they are a minor component of the average global mass flux, anthropogenic particles are abundant in the urban environment, where they contribute substantially to air pollution. Particulate matter is routinely monitored in urban areas, but different particle types can be distinguished only by combining single-particle chemical analysis with bulk analysis of trace elements and measurement of isotope ratios. Such chemical tracers also allow for source identification and thus for targeted mitigation of anthropogenic particle pollution.

Atmospheric brown clouds are atmospheric accumulations of carbonaceous aerosol particles spanning vast areas of the globe. They have recently gained much attention, from the scientific community and from the general population, as they severely impact several aspects of everyday life. Aside from affecting regional air quality and negatively impacting human health, these clouds affect biogeochemical cycles and profoundly influence the radiation budget of the Earth, resulting in severe climatic and economic consequences. Carbonaceous aerosol particles are generated primarily by combustion processes, including biomass and fossil fuel burning. Natural emissions and transformations of volatile organic species in the atmosphere also contribute to the development of atmospheric brown clouds.

Atmospheric particulates—tiny particles in the air—represent an exciting new research area for mineralogists and geochemists. Emitted directly into or formed within the atmosphere, these particles are generated by both natural processes and human activity. Although derived mostly from sources that are spatially and temporally confined, the particles are ubiquitous globally due to atmospheric circulation. Depending on their physical and chemical properties, these small particles have local- to planetary-scale environmental impacts, influencing the radiative properties of the atmosphere and the cryosphere, the nucleation of both warm and ice clouds, and the nutrient contents of oceans and soils. Because airborne particles can affect human health and transportation, mainly aviation, they have become a focus of government attention and regulation.