戈壁沙尘释放率及其对地表异质性响应机制的研究

Gobi sediment content of different particle size, coverage, and distribution form are the main factors to determine the surface dust release rate, using quantitative approaches to study the relationship between the Gobi surface heterogeneity and dust release rate is the main scientific question to be solved in arid areas. In this project, grid sampling technique, sediment particle size screening technology, digital photographing and image interpretation technology, and probability function will be applied in the western Gobi desert in Inner Mongolia to characterize the Gobi surface heterogeneity and dimension variation law quantitatively. Based on wind tunnel simulation and field observation the process of releasing dust from the original Gobi land-surface soil sample, particulate matter and micro pulse laser radar system, and on-line monitoring system will be used to measure the release of dust aerosol dynamics in spatial and temporal as well as the concentration of PM10, PM2.5 and PM1.0 under different intensity of shear wind speed to clarify the Gobi surface dust release power transmission process. The Gobi surface wind erosion and dust emission flux model will be built based on the effect of multi-scale dust release rate on the surface heterogeneity and wind power sensitivity analysis using more parameters. The Gobi desert dust release rate due to wind erosion will be calculated as well. This project will help understand the dust release mechanism in the Gobi surface, which will be beneficial to the correction of regional and global scales dust circulation model and provide theory basis for prevention and control of dust sources.

戈壁沉积物不同粒径颗粒含量、盖度及分布形式是决定其地表沙尘释放率的主要因素，定量研究戈壁地表异质性与沙尘释放率之间的关系是干旱区风沙物理学研究亟待解决的主要科学问题。以内蒙古西部戈壁为研究对象，采用网格化取样技术，沉积物粒度筛分技术，数字照相和图像解译技术，应用概率密度函数分析方法，定量表征戈壁地表异质性及其尺度变化规律。基于风蚀戈壁沙尘释放过程的风洞模拟和野外观测，利用颗粒物在线监测系统和微脉冲激光雷达系统，测定不同强度剪切风速下地表释放沙尘气溶胶PM10，PM2.5和PM1.0浓度的时空动态变化，阐明戈壁地表沙尘释放动力过程。通过多尺度沙尘气溶胶浓度对地表异质性和风动力多参数指标的敏感性分析，构建戈壁地表风蚀沙尘释放通量模型，计算戈壁沙尘释放率。本项目研究有助于认识戈壁地表沙尘释放机制，对校正全球及区域尺度沙尘循环模式都有重要意义，同时为沙尘源的确定提供理论依据。

戈壁沉积物不同粒径颗粒含量、盖度及分布形式是决定其地表沙尘释放率的主要因素，定量研究戈壁地表异质性与沙尘释放率之间的关系是干旱区风沙物理学研究亟待解决的主要科学问题。本项目围绕①定量表征戈壁地表空间异质性及其尺度变化规律，②阐明风蚀戈壁地表沙尘释放动力过程，③戈壁地表沙尘气溶胶浓度的小尺度时空变化规律，④构建风蚀戈壁地表沙尘释放通量模型为主要内容开展研究。获得以下主要结果：. ① 建立了沙砾质戈壁地表沉积物全粒径分布模式P(di) =Cdi-μ exp(-di/Dc)， 修正了沉积物分形维数计算模型，全粒径参数（μ，Dc）、分形维数值可定量表征戈壁地表空间异质性及其尺度变化规律。. ②沙粒碰撞磨蚀产尘气溶胶PM10, PM2.5和PM1.0浓度变化过程研究，表明沙粒碰撞磨蚀产尘是戈壁沙尘的主要来源,风速越高，达到最大磨蚀产尘率时间越短，且最大磨蚀产尘率越大。. ③不同风速尘暴过程，砾石盖度会显著影响风沙运动，并会在速度大于10m/s时，形成距地表1.5m~2.1m的两相流速度交点，交点上下表现为“风快沙慢”及“风慢沙快”现象, 且近地表沙尘浓度沿均值线呈“脉动”规律，表现为地表粉尘沉降与再释放循环过程. ④基于二维风-沙互馈模型构建了三维场流体-颗粒碰撞互馈模型能够较为理想的还原风沙两相流运动过程,计算沙尘释放率。. 本项目研究有助于认识戈壁地表沙尘释放机制，对校正全球及区域尺度沙尘循环模式都有重要意义，同时为沙尘源的确定提供理论依据。.