New insights into dust emission mechanism in natural environments based on a series of field observations.

Most scholars have suggested that dust emission mainly depends on the bombardment of saltation particles based on wind tunnel experiments, because the cohesive forces between finer particles. However, in recent years, researchers have found that dust can be entrained directly in field. To detect the dust emission mechanism in natural environments, two types of field observations were carried out. Long-term observations were implemented on the shore of the Zu Lake, and the results show that the sediments contain large fractions of particulate matter <10 µm (PM10), which indicates that the entrainment of PM10 in sediment cannot solely depend on saltation bombardment. Short-term observations were conducted across the Desert Steppe, the Mu Us Sandy Land, and the shore of the Zu Lake, and a total of 31 plots were observed, which revealed that in most of the plots, the threshold of the friction velocities (TFVs) for PM10 entrainment was lower than for the entrainment of saltation particles, indicating that the PM10 was easier to entrain than the saltation particles. Large fractions of emitted PM10 were directly entrained, especially when the PM10 emission was continuous regardless of whether the PM10 contents of the soils were low or high, because the strong wind environment could renew the surface frequently and provided sufficient PM10 to be emitted. Based on our observations, we concluded that in natural environments, direct dust entrainment is the dominant dust emission mechanism, especially in continuous emission processes. Herein, we developed a parameterization scheme for continuous dust emission in natural environments, and this scheme can accurately simulate dust emission on different surfaces. The results of this study provide robust validation for the fact that direct dust entrainment dominates the dust emission mechanism in natural environments. In addition, the results provide valuable observation data for parameterization of dust emission.

Sand fixation and human activities on the Qinghai-Tibet Plateau for ecological conservation and sustainable development.

The sand fixation ecosystem services and human activities on the Qinghai-Tibet Plateau (QTP) play a crucial role in local sustainable development and ecosystem health, with significant implications for surrounding regions and the global ecological environment. We employed an improved integrated wind erosion modeling system (IWEMS) model for the QTP to simulate sand fixation quantities under the unique low temperature and low pressure conditions prevalent on the plateau. Using the human footprint index (HFI), the intensity of human activities on the plateau was quantified. Additionally, an econometric model was constructed to analyze the impacts of the natural factors, the HFI, and policy factors on the sand fixation capacity. The results revealed that the average sand fixation quantity was 1368.0 t/km2/a, with a standard deviation of 1725.4 t/km2/a, and the highest value during the study period occurred in 2003. The average value of the HFI for 2020 was 6.69 with a standard deviation of 6.61, and the HFI exhibited a continuous growth trend from 2000 to 2020. Despite this growth, the average human activity intensity remained at a low level, with over 50 % of the area having an index value of <4.84. Overall, a strong negative correlation was observed between the sand fixation ecological capacity and the HFI on the QTP. However, extensive regions exhibited high values or low values for both indicators. The sand fixation capacity on the QTP is influenced by both natural and human factors. In light of these findings, suggestions are made for optimizing protected area design, rational control of human activity scales, and targeted human activity aggregation within certain regions as part of ecological conservation strategies. This study has implications for assessing sand fixation ecological functions in high-altitude regions and enhancing sand fixation capacity within the region, providing valuable practical guidance.

Regional Potential Wind Erosion Simulation Using Different Models in the Agro-Pastoral Ecotone of Northern China.

Wind erosion is crucial for assessing regional ecosystem services and sustainable development. The Agro-Pastoral Ecotone of northern China (APEC) is a typical region undergoing wind erosion and soil degradation. In this study, the National Wind Erosion Survey Model of China, the Integrated Wind Erosion Modeling System, and the regional versions of the Revised Wind Erosion Equation and Wind Erosion Prediction System were used to evaluate the regional potential wind erosion of the APEC during 2000 and 2012. The results showed that the potential wind erosion predicted by National Wind Erosion Survey Model of China (NWESMC), Revised Wind Erosion Equation (RWEQ), Wind Erosion Prediction System (WEPS), and Integrated Wind Erosion Modeling System (IWEMS) were significantly related to the observed wind erosion collected from published literature, but the observed data were generally smaller than the predicted values. The average potential wind erosions were 12.58, 25.87, 52.63, and 58.72 t hm-2 a-1 for NWESMC, RWEQ, WEPS, and IWEMS, respectively, while the spatial pattern and temporal trend of annual potential wind erosion were similar for different wind erosion models. Wind speed, soil moisture, and vegetation coverage were the dominant factors affecting regional wind erosion estimation. These results highlight that it is necessary to comprehensively calibrate and validate the selected wind erosion models. A long-term standard wind erosion monitoring network is urgently required. This study can serve as a useful reference for improving wind erosion models.

Soil organic carbon (SOC) enrichment in aeolian sediments and SOC loss by dust emission in the desert steppe, China.

Dust emission is an important mechanism for carbon exchange between terrestrial and atmospheric carbon pools. However, undetermined soil organic carbon (SOC) enrichment in aeolian sediment limits the accurate estimation of SOC loss induced by wind erosion. Herein, we examined wind erosion and SOC loss measurements in the desert steppe of Inner Mongolia, China. By testing the particle size distributions (PSDs) and SOC contents across different particle size groups of the soil samples and aeolian sediments, we found that the finer soil particles generally had higher SOC contents. According to the measured results, we recognized that the mechanism of SOC enrichment in aeolian sediment is the inconstant distribution of SOC across the different soil particle size groups and the differences between the PSDs of soils and aeolian sediments. Based on the mechanism, we proposed a method to calculate the SOC content in aeolian sediment, and the calculated results are highly consistent with the measured results. Compared with the previous method, our calculation method provided a more precise result. Integrating our method for estimating SOC content in dust (diameter less than 50 µm) and a dust emission model, we simulated the SOC loss induced by wind erosion in this region by a wind erosion model, and the results show SOC loss induced by dust emissions ranging from 0 to 39 g/m2/y during the period of 2001 to 2017. We believe the study method of dust SOC content calculation we proposed could be interested by the scholars in the field of carbon cycling, and the simulated results of SOC loss could provide robust data for the estimation of carbon budget in the desert steppe.

Estimation of saltation emission in the Kubuqi Desert, North China.

The Kubuqi Desert suffered more severe wind erosion hazard. Every year, a mass of aeolian sand was blown in the Ten Tributaries that are tributaries of the Yellow River. To estimate the quantity of aeolian sediment blown into the Ten Tributaries from the Kubuqi Desert, it is necessary to simulate the saltation processes of the Kubuqi Desert. A saltation submodel of the IWEMS (Integrated Wind-Erosion Modeling System) and its accompanying RS (Remote Sensing) and GIS (Geographic Information System) methods were used to model saltation emissions in the Kubuqi Desert. To calibrate the saltation submodel, frontal area of vegetation, soil moisture, wind velocity and saltation sediment were observed synchronously on several points in 2011 and 2012. In this study, a model namely BEACH (Bridge Event And Continuous Hydrological) was introduced to simulate the daily soil moisture. Using the surface parameters (frontal area of vegetation and soil moisture) along with the observed wind velocities and saltation sediments for the observed points, the saltation model was calibrated and validated. To reduce the simulate error, a subdaily wind velocity program, WINDGEN was introduced in this model to simulate the hourly wind velocity of the Kubuqi Desert. By incorporating simulated hourly wind velocity, and model variables, the saltation emission of the Kubuqi Desert was modeled. The model results show that the total sediment flow rate was 1-30.99 tons/m over the last 10years (2001-2010). The saltation emission mainly occurs in the north central part of the Kubuqi Desert in winter and spring. Integrating the wind directions, the quantity of the aeolian sediment that deposits in the Ten Tributaries was estimated. Compared with the observed data by the local government and hydrometric stations, our estimation is reasonable.