Response of dust emissions in southwestern North America to 21st century trends in climate, CO₂ fertilization, and land use: implications for air quality

Climate models predict a shift toward warmer and drier environments in southwestern North America. The consequences of such a shift for dust mobilization and dust concentration are unknown, but they could have large implications for human health, given the connections between dust inhalation and disease. Here we link a dynamic vegetation model (LPJ-LMfire) to a chemical transport model (GEOS-Chem) to assess the impacts of future changes in three factors – climate, CO2 fertilization, and land use practices – on vegetation in this region. From there, we investigate the impacts of changing vegetation on dust mobilization and assess the net effect on fine dust concentration (defined as dust particles less than 2.5 µm in diameter) on surface air quality. We find that surface temperatures in southwestern North America warm by 3.3 K and precipitation decreases by nearly 40 % by 2100 in the most extreme warming scenario (RCP8.5; RCP refers to Representative Concentration Pathway) in spring (March, April, and May) – the season of greatest dust emissions. Such conditions reveal an increased vulnerability to drought and vegetation die-off. Enhanced CO2 fertilization, however, offsets the modeled effects of warming temperatures and rainfall deficit on vegetation in some areas of the southwestern US. Considering all three factors in the RCP8.5 scenario, dust concentrations decrease over Arizona and New Mexico in spring by the late 21st century due to greater CO2 fertilization and a more densely vegetated environment, which inhibits dust mobilization. Along Mexico's northern border, dust concentrations increase as a result of the intensification of anthropogenic land use. In contrast, when CO2 fertilization is not considered in the RCP8.5 scenario, vegetation cover declines significantly across most of the domain by 2100, leading to widespread increases in fine dust concentrations, especially in southeastern New Mexico (up to ∼ 2.0 µg m−3 relative to the present day) and along the border between New Mexico and Mexico (up to ∼ 2.5 µg m−3). Our results have implications for human health, especially for the health of the indigenous people who make up a large percentage of the population in this region.

A Novel Facility to Investigate Dust Mobilization in Confined Environments with Applications to the Security of the Pharmaceutical Industry

Many pharmaceutical industries all around the world are facing the problem of dust mobilization during the productive process of medicines. This mobilization can be dangerous for the safety of the operators working in the factory and for the safety of the factory itself. It is therefore necessary to develop predictive models to simulate and forecast dust mobilization. The Quantum Electronics and Plasma Physics (QEP) Research Group of the University of Rome Tor Vergata has developed a facility to experimentally replicate dust mobilization in different critical conditions in an enclosed environment. The measurements performed with diagnostics available in the facility, provide the boundary conditions to run numerical simulations and to validate mobilization models . Even if the initial field of application of this novel facility is dust mobilization is nuclear fusion, the methodology developed can be used for the medicine industry, for the agribusiness and others. The authors will present the experimental and numerical results discussing new applications.

Numerical Simulations as Tool to Predict Chemical and Radiological Hazardous Diffusion in Case of Nonconventional Events

CFD (Computational Fluid Dynamics) simulations are widely used nowadays to predict the behaviour of fluids in pure research and in industrial applications. This approach makes it possible to get quantitatively meaningful results, often in good agreement with the experimental ones. The aim of this paper is to show how CFD calculations can help to understand the time evolution of two possible CBRNe (Chemical-Biological-Radiological-Nuclear-explosive) events: (1) hazardous dust mobilization due to the interaction between a jet of air and a metallic powder in case of a LOVA (Loss Of Vacuum Accidents) that is one of the possible accidents that can occur in experimental nuclear fusion plants; (2) toxic gas release in atmosphere. The scenario analysed in the paper has consequences similar to those expected in case of a release of dangerous substances (chemical or radioactive) in enclosed or open environment during nonconventional events (like accidents or man-made or natural disasters).

Density currents as a desert dust mobilization mechanism

The formation and propagation of density currents are well studied processes in fluid dynamics with many applications in other science fields. In the atmosphere, density currents are usually meso-β/γ phenomena and are often associated with storm downdrafts. These storms are responsible for the formation of severe dust episodes (haboobs) over desert areas. In the present study, the formation of a convective cool pool and the associated dust mobilization are examined for a representative event over the western part of Sahara desert. The physical processes involved in the mobilization of dust are described with the use of the integrated atmospheric-air quality RAMS/ICLAMS model. Dust is effectively produced due to the development of near surface vortices and increased turbulent mixing along the frontal line. Increased dust emissions and recirculation of the elevated particles inside the head of the density current result in the formation of a moving "dust wall". Transport of the dust particles in higher layers – outside of the density current – occurs mainly in three ways: (1) Uplifting of preexisting dust over the frontal line with the aid of the strong updraft (2) Entrainment at the upper part of the density current head due to turbulent mixing (3) Vertical mixing after the dilution of the system. The role of the dust in the associated convective cloud system was found to be limited. Proper representation of convective processes and dust mobilization requires the use of high resolution (cloud resolving) model configuration and online parameterization of dust production. Haboob-type dust storms are effective dust sources and should be treated accordingly in dust modeling applications.

Density currents as a desert dust mobilization mechanism

The formation and propagation of density currents are well studied processes in fluid dynamics with many applications to other science fields. In the atmosphere, density currents are usually meso-β/γ mechanisms and are often associated with storm downdrafts. These storms are responsible for the formation of severe dust episodes (haboobs) over desert areas. In the present study, the formation of a convective cool pool and the associated dust mobilization is examined for a representative event over the western part of Sahara desert. The physical processes involved in the mobilization of dust are described in the framework of the integrated atmospheric-air quality RAMS/ICLAMS model. Dust is effectively produced due to the development of near surface vortices and increased turbulence mixing along the frontal line. Increased dust emissions and recirculation of the elevated particles inside the density current head result in the formation of a moving "dust wall". Transport of the uplifted dust in higher layers – outside of the density current – occurs mainly in three ways: (1) uplifting of preexisting dust over the frontal line with the aid of the strong updraft (2) entrainment at the upper part of the density current head due to turbulent mixing (3) vertical mixing after the dilution of the system. The role of the produced dust in the associated convective cloud system was found to be limited. Proper representation of convective processes and dust fluxes requires the use of high resolution (cloud resolving) model configuration and online parameterization of dust production. Haboob-type of dust storms are effective dust sources and should be treated accordingly in dust modeling applications.