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Dry aggregate stability (DAS) is an important factor that influences soil erodibility. The purpose of this study was to measure DAS of soil, as well as assess the effect of crop rotation, soil amendment, and tillage on DAS in the main wind erosion area across the inland Pacific Northwest United States (iPNW). The stability of dry aggregates was measured using a commercial penetrometer and was found to be lower for soils in the iPNW than previously reported in other regions. Significant differences in DAS were found between tillage treatments at all locations. Dry aggregate stability was 24 to 114% higher for no-tillage summer fallow than tillage-based summer fallow treatments. Although not significant, DAS for a winter wheat-summer fallow (WW-SF) rotation was consistently higher than winter wheat-camelina-summer fallow (WW-C-SF) or winter wheat-safflower-summer fallow (WW-S-SF) rotations at two sites in central Washington. In contrast, when green manure or biosolids were applied as an amendment, there was no difference in DAS. Dry aggregate stability was more closely related to clay content than other soil properties (i.e. sand content and surface area of primary particles). Clay content, in the range 9 to 14%, can therefore be used to estimate DAS of soils in the iPNW. No-tillage management practices was beneficial to maintain greater DAS, thereby making soil aggregates more resistant to erosion and degradation.

Soil crusts provide stability and protection against wind erosion from semiarid and arid lands. Although erosion is initiated when the friction velocity (U*) exceeds the threshold friction velocity (U*ₜ) of soils, there is little information available on the effect of soil crust cover on U*ₜ. The objective of this study was therefore to evaluate the effect of soil crust cover on the U*ₜ of five loessial soils of the Columbia Plateau, United States. Soil samples were sieved and the erodible fraction was placed in 1 by 0.2 by 0.015 m trays. Water drops 4.5 mm in diameter were applied to the soil surface at a known density, which, after drying, created various percentages of crust cover. The trays were placed inside a wind tunnel to assess U*ₜ. which was determined by systematically wind speed until an increase was observed in total suspended particulate concentration inside the tunnel. No significant differences in U*ₜ were found among 0, 15, and 30% cover but significant differences in U*ₜ were found between 60 and 100% cover. The U*ₜ of 100% crust cover was about twice that of 0% cover. Crust crushing energy, which influences abrasion, did not vary across crust cover treatments. The Single-event Wind Erosion Evaluation Program (SWEEP) revealed the similar influence of crust cover on U*ₜ. The SWEEP adequately simulated U*ₜ for 0, 15, and 30% crust cover but overestimated U*ₜ for 60 and 100% cover. These results suggest that crusts effectively protect the soil from wind erosion by increasing U*ₜ.

Instruments capable of measuring PM10 (particulate matter ≤10 µm in aerodynamic diameter) concentrations may vary in performance as a result of different technologies utilized in measuring PM10. Therefore, the performance of five instruments capable of measuring PM10 concentrations above eroding soil surfaces was tested during high wind events at field sites in the Columbia Plateau and inside a wind tunnel. Comparisons among the Big Spring Number Eight (BSNE) sampler, DustTrak monitor, E-sampler, High-Volume sampler, and Tapered Element Oscillating Microbalance (TEOM) monitor were made at field sites during nine wind erosion events and inside a wind tunnel at two wind speeds (7 and 12 m s−1) and two ambient PM10 concentrations (2 and 50 mg m−3). PM10 concentrations were similar for the High-Volume sampler and TEOM monitor as well as for the BSNE samplers and DustTrak monitors but higher for the High-Volume sampler and TEOM monitor than the E-sampler during field erosion events. Based upon wind tunnel experiments, the TEOM monitor measured the highest PM10 concentration while the DustTrak monitor typically measured the lowest PM10 concentration as compared with other instruments. In addition, PM10 concentration appeared to lower for all instruments at a wind speed of 12 as compared with 7 m s−1 inside the wind tunnel. Differences in the performance of instruments in measuring PM10 concentration poses risks in comparing PM10 concentration among different instrument types or using multiple instrument types to jointly measure concentrations in the field or laboratory or even the same instrument type subject to different wind speeds.

Biosolids are frequently applied to agricultural lands in dry regions, but wind erosion of these lands might transport biosolids particulates offsite and impact environmental quality. Our objective was to measure concentrations of EPA-regulated metals as well as macronutrients and micronutrients in soil and windblown sediment from a biosolids field experiment. A wind tunnel was used to generate windblown sediment from experimental plots subject to traditional (disk) or conservation (undercutter) tillage and application of biosolids or synthetic fertilizer on two measurement dates during the summer fallow phase of a winter wheat-summer fallow (WW-SF) rotation at Lind, WA in 2015 and 2016. Application of biosolids or use of undercutter tillage resulted in higher concentrations of heavy metals in the soil. For example, zinc (Zn) concentration in soil was 14% higher for undercutter than disk tillage and 21% higher for biosolids than synthetic fertilizer on the first measurement date in 2015. Differences in metal concentrations between treatments, however, were not as evident in windblown sediment. Similar results were found for nutrient concentrations in soil, but concentrations in windblown sediment were at least 10% lower for biosolids than synthetic fertilizer and undercutter than disk tillage on at least one measurement date. Little difference was found in loss of heavy metals and nutrients in windblown sediment between biosolids and synthetic fertilizer treatments. Our results suggest similar loss of metals and other elements from agriculture land after application of biosolids and synthetic fertilizer. Biosolids, however, are beneficial for increasing C and N content in soil.

Conservation tillage is a viable management strategy to control soil wind erosion, but other strategies such as land application of biosolids that enhance soil quality may also reduce wind erosion. No studies have determined the effects of biosolids on wind erosion. Wind erosion potential of a silt loam was assessed using a portable wind tunnel after applying synthetic and biosolids fertilizer to traditional (disk) and conservation (undercutter) tillage practices during the summer fallow phase of a winter wheat-summer fallow (WW-SF) rotation in 2015 and 2016 in east-central Washington. Soil loss ranged from 12 to 61% lower for undercutter than disk tillage, possibly due to retention of more biomass on the soil surface of the undercutter versus disk tillage treatment. In contrast, soil loss was similar to or lower for biosolids as compared with synthetic fertilizer treatment. Our results suggest that biosolids applications to agricultural lands will have minimal impact on wind erosion.

The Tarim Basin is regarded as one of the most highly erodible areas in China. Desert comprises 64% of the land use in the Basin, but the desert–oasis ecotone plays a prominent role in maintaining oasis ecological security and stability. Yet, little is known concerning the magnitude of windblown sediment transport in a desert-oasis ecotone. Therefore, aeolian sediment transport and loss was assessed from a desert-oasis experimental site located near Alaer City in the northwestern Tarim Basin. Sediment transport and factors governing transport were measured during three high wind events in 2012 and four events in 2013. Sediment transport was measured to a height of 10 m using passive aeolian airborne sediment samplers. The mass flux profile over the eroding surface was well represented by the power-law (R2 > 0.77). Sediment loss from the site ranged from 118 g m−2 for the 20–24Apr 2012 wind event to 2925 g m−2 for the 31Mar–11Apr 2012 event. Suspension accounted for 67.4 to 84.8% of sediment loss across all high wind events. Our results indicate the severity of wind erosion in a desert-oasis ecotone and thus encourage adoption of management practices that will enhance oasis ecological security.

Xinjiang Province in northwest China is one of the most important source regions of atmospheric dust in the world. Spatial-temporal characteristics of dust events in the province were investigated by time series analysis of annual dust event frequency and meteorological data collected at 101 meteorological stations from 1960 to 2007. Blowing dust frequency (BDF) and dust storm frequency (DSF) decreased with time in North, South, and East Xinjiang whereas floating dust frequency (FDF) decreased with time only in South and East Xinjiang. Dust concentrations were lower in North than in South Xinjiang and decreased with time in East Xinjiang. Wind significantly influenced the temporal trend in FDF, BDF, and DSF in South Xinjiang and DSF in North Xinjiang. Frequency of dust events was smaller by an order of magnitude in North (10.9 d yr−1) than in South Xinjiang (111.3 d yr−1), possibly due in part to higher annual precipitation in North Xinjiang. Floating dust was most frequently observed in East and South Xinjiang, while blowing dust was most frequently observed in North Xinjiang. The high frequency of floating dust in East and South Xinjiang is likely due to the enclosed terrain that characterizes these regions. Land use and soil type also influenced dust events. Although climate influences frequency of dust events, the occurrence of these events may be reduced most effectively by imposing better land management practices in deciduous forests or orchards characterized by saline soils in respectively North and East Xinjiang and meadows characterized by Guanyu soils in South Xinjiang.

Snowmelt water is essential to the water resources management over the Three-River Headwater Region (TRHR), where hydrological processes are influenced by snowmelt runoff and sensitive to climate change. The objectives of this study were to analyse the contribution of snowmelt water to the total streamflow (fQ,snow) in the TRHR by applying a snowmelt tracking algorithm and Variable Infiltration Capacity (VIC) model. The ratio of snowfall to precipitation, and the variation of the April 1 snow water equivalent (SWE) associated with fQ,snow, were identified to analyse the role of snowpack in the hydrological cycle. Prior to the simulation, the VIC model was validated based on the observed streamflow data to recognize its adequacy in the region. In order to improve the VIC model in snow hydrology simulation, Advanced Scanning Microwave Radiometer E (ASMR-E) SWE product data was used to compare with VIC output SWE to adjust the snow parameters. From 1971 to 2007, the averaged fQ,snow was 19.9% with a significant decreasing trend over entire TRHR (PQ,snow which were different for each sub-basin TRHR. The decreasing rate of fQ,snow was highest of 0.24%/year for S_Lantsang, which should be due to the increasing streamflow and the decreasing snowmelt water. For the S_Yangtze, the increasing streamflow contributed more than the stable change of snowmelt water to the decreasing fQ,snow with a rate of 0.1%/year. The April 1 SWE with the minimum value appearing after 2000 and the decreased ratio of snowfall to precipitation during the study period, suggested the snow solid water resource over the TRHR was shrinking. Our results imply that the role of snow in the snow-hydrological regime is weakening in the TRHR in terms of water supplement and runoff regulation due to the decreased fQ,snow and snowfall.

The Aksu region within the Tarim Basin is a major source of windblown dust in China due to the arid climate and vast areas under intensive irrigated crop production. Despite the importance of crop production to human subsistence and the local economy, little is known about the amount of soil eroded by wind from agricultural lands in the region. Passive aeolian sediment collectors were used to measure soil loss from an irrigated cotton (Gossypium spp.) field and red date (Ziziphus jujuba Mill.) orchard in the Aksu Oasis during high wind events in 2012 and 2013. Mass of sediment trapped by the collectors was best described as a power function of height above the surface in the cotton field and red date orchard. Soil loss from the cotton field ranged from 0 to 142 g m⁻², whereas soil loss from the red date orchard ranged from 0 to 71 g m⁻² for single- or multiple-day high wind events. Total soil loss from the cotton field and red date orchard, for the high wind events observed in this study, was 130 and 96 g m⁻², respectively, in 2012 and 305 and 165 g m⁻², respectively, in 2013. Soil loss was similar to that reported from agricultural lands in other regions of the world. Although soil loss is relatively small compared with the Gobi Desert in China, poor air quality in the Tarim Basin necessitates identifying crop and soil management practices for reducing windblown dust and conserving the soil resource.

Wind erosion in the desert–oasis ecotone can accelerate desertification, but little is known about the susceptibility of the ecotone to wind erosion in the Tarim Basin despite being a major source of windblown dust in China. The objective of this study was to test the performance of the Single-event Wind Erosion Evaluation Program (SWEEP) in simulating soil loss as creep, saltation, and suspension in a desert–oasis ecotone. Creep, saltation, and suspension were measured and simulated in a desert–oasis ecotone of the Tarim Basin during discrete periods of high winds in spring 2012 and 2013. The model appeared to adequately simulate total soil loss (ranged from 23 to 2272 g m−2 across sample periods) according to the high index of agreement (d = 0.76). The adequate agreement of the SWEEP in simulating total soil loss was due to the good performance of the model (d = 0.71) in simulating creep plus saltation. The SWEEP model, however, inadequately simulated suspension based upon a low d (⩽0.43). The slope estimates of the regression between simulated and measured suspension and difference of mean suggested that the SWEEP underestimated suspension. The adequate simulation of creep plus saltation thus provides reasonable estimates of total soil loss using SWEEP in a desert–oasis environment.

Crop residue is an important factor influencing wind erosion of cultivated soils. Establishing soil surface protection afforded by standing crop residue is critical for land managers seeking to reduce or prevent soil loss by wind erosion and the impacts of blowing dust from agricultural lands. The objectives of this study were to evaluate the effect of standing residue on soil wind erosion in the inland Pacific Northwest (iPNW), USA, and test the performance of the plant factor algorithm of the Agricultural Policy/Environmental eXtender (APEX) and Revised Wind Erosion Equation (RWEQ) models in influencing soil loss. The effect of standing winter wheat (Triticum aestivum L.), spring canola (Brassica napus L.), and chickpea (Cicer arietinum) residue on wind erosion, remaining from major commodity crops in the region, was tested in a laboratory wind tunnel using four levels of residue density. The impact of standing residue in controlling wind erosion was compared and analyzed in terms of residue density and their respective frontal area index. Our results show that residue at a density characteristic of the production environment (110 standing residue elements m−1 for winter wheat, 20 standing elements m−1 for canola, and 16 standing elements m−1 for chickpea) provided significant protection to the soil surface from wind erosion. Soil loss at this level of residue density was reduced by 73.3, 53.4, and 60.9% for respectively winter wheat, spring canola, and chickpea (frontal area indexes are 0.172, 0.104, and 0.026 respectively) compared with a surface without residue. The soil surface was found to be at significant risk from wind erosion when residue densities of the three crop types were

Soil wind erosion is initiated when the surface friction velocity (u*) exceeds the threshold friction velocity (u*t) of soils. Soil clay content is a primary soil component influencing soil erosion. Few studies have tested the effect of clay amendment on u*t, especially in the inland Pacific Northwest (iPNW) where there is a high wind erosion risk due to the arid and semi-arid environment. The objective of this study was therefore to evaluate the effect of soil clay amendment (Wyoming bentonite) on u*t. Bentonite clay was added to four soil types prior to wetting the treated soil to create complete crust cover. The treated soil was then subject to simulated tillage to create an erodible soil surface before determining u*t in a wind tunnel. Clay amendment did not directly impact u*t, but did impact crust and aggregate properties. Crust crushing energy appeared to increase binomially with increasing clay amendment. Statistically significant relationships were found between crust crushing energy and aggregate geometric mean diameter (GMD) and between aggregate GMD and u*t. Clay amendment therefore appeared to indirectly impact u*t due to its impact on aggregate GMD. Our results were similar to previous studies that clay amendment can be effective in stabilizing erosive sandy soil ecosystems.

Dry aggregate stability (DAS) is an important factor influencing soil wind erosion, dust emission and crop production. Historically and to the present, DAS has been determined using a horizontal- or vertical-plate crushing meter (Soil-Aggregate Crushing-Energy Meter, hereafter SACEM). The intent of this paper was to compare the performance of horizontal-plate SACEM with a commercial penetrometer (Mohr Digi-Test, hereafter MDT). The performance of both instruments was tested on aggregates collected from various soil types, crop rotations, soil amendments, and tillage systems across the inland Pacific Northwest United States (iPNW). Results indicated no consistently significant difference in DAS measured by the MDT and SACEM. However, there was evidence that SACEM under-estimated or MDT over-estimated DAS by 74 to 368% in measuring the stability of strong aggregates (DAS > 3 J kg⁻¹). Both instruments measured higher DAS for no-tillage summer fallow, winter wheat-summer fallow (WW-SF) rotations, and no green manure treatments compared with other tillage practices, oilseed rotations, and green manure treatments. The SACEM that has historically been used in measuring soil DAS can be replaced by the commercial penetrometer (MDT). Nonetheless, differences in the performance of instruments in measuring the stability of strong aggregates poses risks.

The Wind Erosion Prediction System (WEPS) is a process-based model and needs to be verified under a broad range of climates, soils, and land management practices. Occasional poor performance of the WEPS erosion submodel (Single-event Wind Erosion Evaluation Program, or SWEEP) in simulating small amounts of erosion of loessial soils, which contribute to poor air quality in the Columbia Plateau region of the U.S. Pacific Northwest, has been partly attributed to overestimation of threshold friction velocity (u*t). Few studies have been conducted to improve the poor performance of the SWEEP in this region. Therefore, the objective of this study was to test the performance of the SWEEP in simulating the occurrence of erosion when the simulated u*t (SWEEP u*t) was replaced with measured values of u*t or with estimates of u*t derived from algorithms used in the Lu and Shao model, Shao model, Texas Tech Erosion Analysis Model (TEAM), and Wind Erosion on European Light Soils (WEELS) model. The occurrence of erosion from agricultural lands was better estimated by the SWEEP when SWEEP u*t was replaced with the u*t algorithm used in the Lu and Shao model. However, soil loss was better estimated by the SWEEP when using SWEEP u*t rather than the measured u*t or other u*t algorithms. Since prediction of both the occurrence and magnitude of wind erosion is important to overall model performance, there is a need to further improve the SWEEP in the Columbia Plateau and other regions where small amounts of erosion can impact soil resources and environmental quality.

The Tarim Basin is an important source of airborne particulate matter that contributes to poor air quality in China. However, little attention has been given to estimating wind erodibility of soils in the region. The objective of this study was to determine the soil wind erodibility for four land use types in the Tarim Basin. Wind erodibility was determined from the dry aggregate size distribution of soils collected from desert, farmland, forest, and shrubland environments in spring 2013. Our analysis revealed that the percentage of soil mass composed of aggregates

The Tarim Basin is a major source of windblown dust in China. Land management and use can greatly impact windblown dust, thus, models such as the Wind Erosion Prediction System (WEPS) are important for identifying management practices that reduce the emission of dust. The objective of this study was to test the performance of the WEPS erosion submodel (the Single-event Wind Erosion Evaluation Program (SWEEP)) under contrasting agricultural land use types in the Tarim Basin of northwest China. Wind erosion of a sandy soil was measured and simulated in a cotton (Gossypium hirsutum L.) field and red date (Ziziphus jujuba L.) orchard during the spring of 2012 and 2013. The SWEEP did not simulate differences in soil loss for contrasting agricultural land use types, although measured soil loss was typically smaller than that considered to be of consequence (>100 g m) in the original design of the SWEEP. In fact, the model simulated no erosion for all six high wind events in which we observed erosion in the cotton field and red date orchard. The insensitivity of SWEEP to simulate erosion was caused by the simulated friction velocity being consistently lower than the threshold friction velocity for the loess soil at the cotton field and red date orchard. Because SWEEP is being used to assess wind erodibility of lands and simulate regional air quality in China, SWEEP must be improved for application to lands that emit large and small amounts of windblown dust.

Total suspended particulate (TSP, particle diameter≤100 μm) was the dominant air pollutant and significantly influenced local air quality. In this paper, we investigated the interannual and seasonal variations of TSP and dustfall of the atmosphere over Urumqi, the capital city of Xinjiang Uygur autonomous region, northwestern China, basing on environmental monitoring records and meteorological data from 1986–2012. The results showed that during the study period, annual average TSP concentration decreased from 716 to 260 μg/m3, with an average level of 422.9 μg/m3, while dustfall intensity reduced from 350.4 to 166.6 t/(km2·a), with an average level of 259 t/(km2·a). Over 50% of the annual pollution days were induced mainly by TSP. Spring and winter had relatively higher dustfall intensities, and dense traffic and residential areas had the highest dustfall intensities in the Urumqi metropolitan area. With an annual average precipitation of less than 300 mm, atmospheric particulates in Urumqi could be hardly removed through wet deposition. During spring and summertime prevailing winds from northwest and northeast could carry aeolian dust particles from sandy deserts to Urumqi. Aeolian dusts from deserts would remain to be a priority regarding air pollution control in arid oasis cities.