An official website of the United States government
Abstract Wind erosion and dust emissions affect regions of the world with sparse vegetation cover or affected by agricultural practices that expose the soil surface to wind action. Although several studies have investigated the impact of soil moisture, land use and land cover on soil susceptibility to wind erosion and dust emissions, the effect of surface soil salinity and sodicity on dust emissions, remains poorly understood. Salt accumulation in agricultural soils is a major concern in agroecosystems with high evaporative demand, shallow water tables or irrigated with water rich in dissolved solids. Recent studies have focused on the effect of soil salinity on soil erodibility in dry atmospheric conditions, while the effect of soil salinity and sodicity in more humid conditions still needs to be investigated. Here we use wind tunnel tests to study the effect of high atmospheric humidity on wind erodibility and particulate matter emissions under saline and sodic conditions. We find that the threshold velocity for wind erosion significantly increases with increasing soil salinity and sodicity, provided that the soil crust formed by soil salts is not disturbed. Indeed, with increasing soil salinity, the formation of a soil crust of increasing strength is observed, leading to an increase in the threshold wind velocity and a consequent decrease in particulate emissions. Interestingly, after the threshold velocity was exceeded, soil crusts were readily ruptured by saltating sand grains resulting in comparable or sometimes even higher particulate matter emissions in saline and sodic soils compared to their untreated (‘control’) counterparts which can be explained by salinity‐induced aggregation and sodicity‐driven clay dispersion effects. Lastly, understanding the role of atmospheric humidity under changing climate scenarios will help to modulate the wind erosion processes in saline‐sodic soils and will help mitigate better dust emissions and soil management policies in arid and semi‐arid climate zones.
more »
« less
This content will become publicly available on June 10, 2026
Drainage and lifetime of thin liquid films: the role of salinity and convective evaporation
We investigate experimentally the effect of salinity and atmospheric humidity on the drainage and lifetime of thin liquid films motivated by conditions relevant to air–sea exchanges. We show that the drainage is independent of humidity and that the effect of a change in salinity is reflected only through the associated change in viscosity. On the other hand, film lifetime displays a strong dependence on humidity, with more than a tenfold increase between low and high humidities: from a few seconds to tens of minutes. Mixing the air surrounding the film also has a very important effect on lifetime, modifying its distribution and reducing the mean lifetime of the film. From estimations of the evaporation rate, we are able to derive scaling laws that describe well the evolution of lifetime with a change of humidity. Observations of the black film, close to the top where the film ruptures, reveal that this region is very sensitive to local humidity conditions.
more »
« less
- Award ID(s):
- 2242512
- PAR ID:
- 10611002
- Publisher / Repository:
- Journal of Fluid Mechanics
- Date Published:
- Journal Name:
- Journal of Fluid Mechanics
- Volume:
- 1012
- ISSN:
- 0022-1120
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Air humidity is a vast, sustainable reservoir of energy that, unlike solar and wind, is continuously available. However, previously described technologies for harvesting energy from air humidity are either not continuous or require unique material synthesis or processing, which has stymied scalability and broad deployment. Here, a generic effect for continuous energy harvesting from air humidity is reported, which can be applied to a broad range of inorganic, organic, and biological materials. The common feature of these materials is that they are engineered with appropriate nanopores to allow air water to pass through and undergo dynamic adsorption–desorption exchange at the porous interface, resulting in surface charging. The top exposed interface experiences this dynamic interaction more than the bottom sealed interface in a thin‐film device structure, yielding a spontaneous and sustained charging gradient for continuous electric output. Analyses of material properties and electric outputs lead to a “leaky capacitor” model that can describe how electricity is harvested and predict current behaviors consistent with experiments. Predictions from the model guide the fabrication of devices made from heterogeneous junctions of different materials to further expand the device category. The work opens a wide door for the broad exploration of sustainable electricity from air.more » « less
-
Wind erosion and dust emissions affect regions of the world with sparse vegetation cover or affected by agricultural practices that expose the soil surface to wind action. Research in this field has investigated the impact of soil moisture, land use, and land cover on soil susceptibility to wind erosion and dust emissions. The effect of soil salinity and sodicity, however, remains poorly appreciated. Salt accumulation in agricultural soils is a major concern in agroecosystems with high evaporative demand, shallow water tables or irrigated with water rich in dissolved solids. The understanding of how salts can affect aeolian processes in arid and hyper-arid landscapes remains incomplete. Recent studies focused on the effect of soil salinity on soil erodibility in dry atmospheric conditions, while the effect of soil sodicity and more humid conditions still needs to be investigated. Here we use wind tunnel tests to detect the effect of varying atmospheric humidity on wind erodibility and particulate matter emissions under saline and sodic conditions.Through a series of controlled wind tunnel experiments of soils treated with different concentrations of saline and sodic water, we find that the threshold velocity for wind erosion significantly increases with increasing soil salinity and sodicity, provided that the soil crust formed by soil salts is not disturbed. Indeed, with increasing soil salinity, the formation of a soil crust of increasing strength is observed, leading to an increase in the threshold wind velocity and a consequent decrease in particulate emissions. However, if the crust is destroyed by trampling, no significant changes in threshold velocity for wind erosion are found with increasing salinity and sodicity levels. Interestingly, after the threshold velocity was exceeded, soil crusts were readily ruptured by saltating sand grains resulting in comparable or sometimes even higher particulate matter emissions in saline and sodic soils compared to their untreated ('control') counterparts. Finally, understanding the role of atmospheric humidity under changing climate scenarios will help to modulate the wind erosion processes in saline-sodic soils and will help mitigate better dust emissions and soil management policies in arid and semi-arid climate zones.more » « less
-
Abstract This study examines the effect of surface moisture flux on fog formation, as it is an essential factor of water vapor distribution that supports fog formation. A one‐way nested large‐eddy simulation embedded in the mesoscale community Weather Research and Forecasting model is used to examine the effect of surface moisture flux on a cold fog event over the Heber Valley on January 16, 2015. Results indicate that large‐eddy simulation successfully reproduces the fog over the mountainous valley, with turbulent mixing of the fog aloft in the valley downward. However, the simulated fog is too dense and has higher humidity, a larger mean surface moisture flux, more extensive liquid water content, and longer duration relative to the observations. The sensitivity of fog simulations to surface moisture flux is then examined. Results indicate that reduction of surface moisture flux leads to fog with a shorter duration and a lower height extension than the original simulation, as the decrease in surface moisture flux impairs water vapor transport from the surface. Consequently, the lower humidity combined with the cold air helps the model reproduce a realistic thin fog close to the observations. The outcomes of this study illustrate that a minor change in moisture flux can have a significant impact on the formation and evolution of fog events over complex terrain, even during the winter when moisture flux is typically very weak.more » « less
-
Abstract This article investigates the effect of urban expansion and climate change impacts on heat stress (HS) for Arizona's (AZ; USA) two largest urban agglomerations, the Phoenix and Tucson metropolitan areas, under relatively dry and moist warm conditions with the Weather Research and Forecasting (WRF)‐urban modeling system. We dynamically downscale two contemporary summers, one dry and one moist, relatively to their respective seasonal‐mean specific humidity across AZ. Urban expansion impacts on HS are assessed by performing two identical simulations for each contemporary summer using different land use‐land cover representations: one simulation with the current urban landscape, and one simulation replaces the urban cover with the region's most representative MODIS vegetation type. Climate change impacts on HS are evaluated by performing four additional future simulations, two via dynamical downscaling of relatively dry conditions (one summer under the RCP8.5 and one summer under the RCP4.5 emissions pathways) and two of relatively moist conditions (one summer for each RCP pathway). The selection of future summers is based on their respective seasonal‐mean specific humidity across AZ from an end‐of‐century analysis of 2086–2100. We characterize impacts on HS by examining changes in near‐surface air temperature, Heat Index (HI), and the Universal Thermal Climate Index (UTCI) across urban areas under dry and moist warm conditions. Our results demonstrate that climate change impacts on HS are not well captured by examining only the projected changes in air temperature and are dependent on the bioclimate index considered. Additionally, we apply a new human heat balance (HHB) approach to evaluate the number of hours per day that an acclimatized and non‐acclimatized person would experience uncompensable HS and compare these results (with the number of hours per day) that we obtain when the HI and UTCI surpass commonly used thresholds considered “dangerous” and of “extreme heat stress”, respectively. The HI and UTCI overestimate the number of hours per day that a healthy, acclimatized person would experience uncompensable HS and underestimate dangerous HS for a non‐acclimatized person under both dry and moist conditions, emphasizing that standard metrics may not produce the most informative physiological estimates of HS.more » « less
