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Frequent wind erosion events in semi‐arid regions can lead to significant atmospheric microplastic (MP) emissions from croplands. We examine observed and predicted characteristics of atmospheric MPs over cropland in Northern China. Measurements showed that fibers were the predominant morphology, accounting for 69% of the 198 observed MPs. The observed atmospheric MP abundance varied widely, averaging 0.088 # m−3 in the absence of air masses passing through near‐surface croplands and increasing significantly to 0.26 # m−3 when such air masses were present. The predictions of deposition flux for atmospheric MPs over croplands indicated a spatial variation ranging from less than 0.5 g km−2 day−1 in the north to over 15 g km−2 day−1 in the south, corresponding to an average of approximately 13.3 g km−2 day−1. Our findings highlight the dual role of surface soil as both a potential source and sink of atmospheric MPs, underscoring the need for further research on the regional dynamics of wind‐driven MP emissions and their associated ecosystem health risks in semi‐arid croplands. Plain Language Summary: We studied the presence and characteristics of atmospheric MPs over cropland in Northern China by measuring and predicting their distribution. Our measurements showed that fibers comprised 69% of the 198 observed MPs. The observed abundance of atmospheric MPs increased from 0.088 to 0.26 # m−3 when influenced by air masses passing near‐surface croplands. Predictions showed that the deposition flux of MPs varies across the region, ranging from less than 0.5 to more than 15 g km−2 day−1. This study indicates that cropland soils can release MPs into the air and capture them from the atmosphere. It calls for more research on how wind‐driven MP emissions impact the environment and health in semi‐arid regions. Key Points: Fibers were the most prevalent of atmospheric MPs over cropland of Northern ChinaObserved atmospheric MP abundance increased from 0.088 to 0.26 # m−3 when influenced by air masses passing through near‐surface croplandsCropland surface soil serves as both an emission potential source and a sink for atmospheric MPs [ABSTRACT FROM AUTHOR]

Soil erodibility by wind is not only affected by the basic physical and chemical properties of the soil but also the functional traits of plant roots. However, the roles played by the morphological and architectural traits of plant roots on wind-based soil erodibility in the Bashang region of China are still unclear. Therefore, two typical tree shelterbelts and two shrub shelterbelts in the Bashang region were selected to assess and determine how the root traits affected soil erodibility, especially characteristics such as dry aggregate, soil organic matter, and shearing resistance. The results showed that the soil dry aggregates of the two shrubs (Lycium barbarum and Caragana korshinskii) had higher geometric mean diameters (0.40 ± 0.03 mm) and mean weight diameters (0.82 ± 0.08 mm) but a lower erodible fraction (81.81% ± 1.62%) compared to the two trees (Populus simonii and Ulmus pumila). The mean weight diameter (MWDd) and geometric mean diameter (GMDd) of dry soil aggregates were negatively correlated with the soil erodible fraction (EFd), but these parameters were positively correlated with shearing resistances. The specific root length (SRL) and surface area (SSA) of plant roots were positively correlated with the GMDd of the soils, though these two parameters negatively correlated with the soil erodible fraction. The root branching intensity (BI) was negatively correlated with the MWDd and GMDd of dry soil aggregates. The total carbon or nitrogen of the soil displayed significantly positive and negative correlations to the geometric mean diameters and erodible fractions of the soils, respectively. The findings showed that plant roots with higher SRLs, as well as lower root diameters and BIs, played positive key roles in soil stability. The same applied to soils with higher nitrogen, carbon, and water content. The results from this study suggest that L. barbarum is superior to the other three species based on root traits and wind erosion resistance. These findings provide critical information for selecting plants for the sustainable management of windbreak and sand fixation. [ABSTRACT FROM AUTHOR]

Dust emission depends directly and indirectly on soil particle distribution, but little information is available that examines dust emission potential and its relationship with wind erosion for different soils. This study aimed to elucidate the difference in wind erosion characteristics between loamy farmland (LF) and sandy farmland (SF) and discuss the influence of this difference on dust emission potential. Field observations were conducted during 2012–2016 in Bashang district, North China. With increasing friction wind speed, the horizontal mass flux increased exponentially in LF but obeyed the power function in SF. The horizontal mass flux was higher in SF than in LF, but the gap narrowed from 766 times at friction wind speed of 0.3 m s−1 to 50 times at 0.6 m s−1. The dry aggregate size distribution of sediment in LF was finer than in SF. Fine particle content (diameter < 0.05 mm) in windblown sediment was much higher in LF (31.39%) than in SF (5.92%), which was influenced by parent soils. With height increasing, the mass percentage of sediment decreased more rapidly in SF than in LF, with 86% and 66% of sediment clustering at height 0–20 cm, respectively. Because the horizontal mass flux and dust content in sediment both increased more quickly in LF than in SF with increasing friction wind speed, the dust emission potential was larger in LF than in SF under strong winds. The adverse effect of dust emission in loamy soils on atmospheric pollution should receive more attention in strong wind erosion events. [ABSTRACT FROM AUTHOR]

Soils of croplands especially where plastic film mulch is commonly applied, are normally contaminated by Microplastics (MPs). Microplastics can threaten air quality, food and water health, as well as human health by wind erosion processes. In this research, we investigated MPs collected in four wind erosion events at sampling heights between 0 and 60 cm in typical semiarid farmlands in northern China that employ plastic film mulch. Height distribution and enrichment heights of the MPs were measured. The results revealed that the average amounts of MPs for 0–20 cm, 20–40 cm and 40–60 cm sampling heights were 868.71 ± 249.21, 799.87 ± 271.25, 1102.54 ± 317.44 particles kg−1. The average enrichment ratios of MPs for the different heights were 0.89 ± 0.54, 0.85 ± 0.56, 1.15 ± 0.73. Height distribution of MPs was combined affected by shape (fiber and non-fiber) and size of MPs, wind speed and soil aggregate stability. The amount of fibers approximately <4 mm in size and non-fibers <2 mm in size increased with sampling height, while both shapes of larger MPs than these two sizes was almost independent of the sampling height. Enrichment ratios of microfibers were positively related to wind speed but negatively related to soil aggregate stability at each sampling height. The results revealed that although MPs have similar density to organic matter (OM), the MPs' amount and enrichment were independent of height but the OM content and enrichment ratios increased with height. These results suggested that more attention should be paid to the exploration of the influence of higher sampling heights (>60 cm) on the distribution of MPs in the future and the MPs characteristics for different sampling heights require carefully parameterization in detailed models of atmospheric MPs transport by wind erosion. [Display omitted] • The microplastics enrichment ratio in wind-blown sediment are independent of sampling height. • The organic matter enrichment ratio in wind-blown sediment are dependent on sampling height. • The microplastics characteristics at different sampling heights depend on its shape and size. [ABSTRACT FROM AUTHOR]

• We first evaluated six popular deterministic hourly wind speed generation models. • All the generation models tend to underestimate hourly wind speeds. • Diurnal hourly wind speed patterns governed model performance. • A scheme to improve wind speed generation models was proposed. The diurnal patterns of hourly wind speed data are fundamentally important in precise wind erosion modeling. Several deterministic wind speed simulation models, including the Guo (1/π), Guo (1/2), wind generator (WINDGEN), Ephrath, Debele, and Goudriaan models, have been developed to quantitatively generate hourly wind speed data. In this study, the performances of these popular deterministic wind speed generation models were investigated using observed hourly wind speed data obtained from 191 climate stations in arid and semi-arid areas of China. The performances of the Guo (1/π), Guo (1/2) and WINDGEN models were the best for hourly wind speed generation. Linear regression analysis revealed that all models tended to underestimate wind speeds. The patterns of diurnal variation and the amplitude of the measured hourly wind speed data generally governed the model performance. The performances of the Guo (1/π), WINDGEN, Guo (1/2), Goudriaan, Debele, and Ephrath models successively decreased for the daily average erosive wind power density (AWPD) estimation. To improve the Guo (1/π) and Guo (1/2) models for AWPD evaluation, the calibrated parameters (π and 2) of the second term in the Guo (1/π) and Guo (1/2) models showed different values for each station. The accuracy of the AWPD obtained by the Guo (1/π) and Guo (1/2) models with the calibrated parameters were significantly improved, which could further influence the accuracy of wind erosion modeling. More studies are required to investigate the relationship between the calibrated parameters in the Guo (1/π) and Guo (1/2) models and geographic conditions linked with wind erosion. [ABSTRACT FROM AUTHOR]

• A new model was proposed for dry soil aggregate size distribution. • The performance of the new model is better than the existed models. • Dry soil aggregate size distribution patterns affect the accuracy of these models. • The choice of screen openings affects dry soil aggregate size distributions. • A parameter in the new model (d r) was significantly related to wind erosion rate. Dry soil aggregate size distribution (DASD) is an important parameter in evaluating soil management practices or modeling of wind erosion and dust emissions. Several models including Lognormal, Fractal and Weibull distributions have been developed to quantitatively describe the DASD. In this study, a new model combining power-law and exponential distributions was proposed to characterize DASD. The performances of the Fractal, Weibull and modified Lognormal distributions and the new model were investigated using 253 DASD data from published documents across five countries. The new model best described the observed DASD data across different soil texture, land use and sieving cuttings. The patterns of DASD generally governed the goodness of fit of these DASD models. The Fractal and Weibull distributions could not well depict the right-skewing unimodal and multimodal DASD data. The modified Lognormal distribution could not well describe the multimodal DASD data. The larger aggregate size distribution was better dictated by the power-law distribution, whereas the smaller aggregate size distribution was characterized by the power-law and exponential distributions for the new model. The choice of screen opening for sieving procedure could affect the patterns of the apparent DASD, and further influence the accuracy of the DASD models. The d r , a parameter in the new model, was significantly related to rock fragments, soil aggregate stability and wind erosion rate. More studies are required to investigate the relationship between the parameters of the new model and soil properties linked with wind erosion. [ABSTRACT FROM AUTHOR]

Soil wind erosion can alter soil texture, reduce land productivity, and adversely affect agricultural production. Gravel cover is a conventional tillage method applied to mitigate wind erosion, enhance soil moisture content, and regulate soil wind erosion rate (q) by varying the shear stress on the exposed soil surface (τ a) surrounding the gravel. However, the relationship between the spatial heterogeneity of τ a and q remains unclear. To address this knowledge gap, 125 wind tunnel experiments were conducted in this study to determine the distribution of τ a and q at five inlet wind friction velocities (u * ∞ = 0.31, 0.39, 0.46, 0.54, and 0.62 m s−1), five gravel diameters (D= 1.6, 2.0, 3.15, 4.0, and 5.0 cm), and five degrees of gravel coverage (GC= 5 %, 10 %, 20 %, 30 %, and 40 %). The results indicated that the spatial distribution of τ a is influenced by u *∞ , D , and GC. High τ a values were observed on both sides of the gravel, whereas low τ a values occurred in the narrow areas immediately upwind and downwind of the gravel coverage. The probability density function of τ a follows a logistic function. Furthermore, the combined effects of D and GC can be assessed using lateral coverage (λ). When gravel distribution is sparse (λ ≤ 0.04), gravel cover exacerbates wind erosion with an increase in u *∞. When the gravel distribution is dense (λ > 0.16), the inhibitory effect of gravel cover on q stabilizes. The spatial heterogeneity of τ a contributes to the spatial differentiation of q around the gravels. By incorporating the probability density function of τ a , the soil wind erosion rate equation can be used to accurately calculate q under all u *∞ , D , and GC conditions applied in this study. These findings significantly advance our understanding of the influence of gravel cover on q and provide initial resolutions to two long-standing challenges: the spatial heterogeneity of τ a and the upscaling of point-scale process models of soil wind erosion. • Spatial heterogeneity of shear-stress affects spatial differentiation of erosion. • Gravels with diameter <3.15 cm and coverage ≥30 % can effectively control erosion. • Soil wind erosion rate equation based on probability density function was developed. [ABSTRACT FROM AUTHOR]

• We introduced a family of logistic growth models that describe the fetch process of aeolian sand flux. • The logistic models best describe the observed sand flux data of wind tunnel and field. • The patterns of sand flux across a sand bed generally govern the goodness of fit of the fetch models. Soil loss and dust emissions due to wind erosion result in soil degradation. The fetch effect, referring to an increase in aeolian sand transport with downstream distance over an eroding surface, is important in modeling wind erosion and parameterizing sand dunes and ripples. Several fetch models have been developed to quantitatively depict the variation of sand flux over a sand bed. The present study first verifies that the family of logistic growth models extensively used in biological systems can be used to describe the fetch process of sand flux. The performances of Fryrear (Fryrear and Selah, 1996), Visser (Visser et al., 2004), Stout (Stout, 1990), Andreotti (Andreotti et al., 2010), and logistic fetch models are investigated using data for 39 wind tunnel experiments across six countries and 51 field measurements across four countries. Results reveal that the patterns of sand flux across a sand bed generally govern the goodness of fit of these fetch models. The logistic models best describe the observed sand flux data and well simulate the maximum sand flux (fmax) and corresponding critical fetch length (L sat). Generally, the Fryrear, Visser, and logistic models yielded similar fmax and L sat while the Stout, and Andreotti models overestimate fmax and L sat. The magnitudes of the L sat and saturation length (b) varied considerably under different environments. More studies are required to explore the domain of L sat across various environments and what factors affect these fitting coefficients (such as fmax and L sat) and how for the logistic models. [ABSTRACT FROM AUTHOR]