甘肃民勤沙尘暴源区沙尘输运规律与理化特征及下垫面对其影响的实验观测研究

Dust is an important component of atmospheric particles, which received much concern because of its influence on biogeochemical cycle, atmosphere radiation balance, air quality and human health. Researching on the transport, physical and chemical characteristics of the aeolian dust has important significance for learning occurrence and development of dust weather procession, modifying dust weather forecast model and source apportionment. The layer form 0-50 m of sandstorm dust source area is the main distribution area of dust particles during the sandstorm procession, which is the most important region for human life. The previous study found that the dust-storm particles in different regions have distinguished differences in their physical and chemical properties, which is important and lack of research fields for sandstorm. We intended to take the sandstorm observation towers which were constructed in the desert, edge of oasis, oasis and dried up lake as a platform to monitoring and collect dust samples at different height in the layer of 0-50 m on different surface conditions, to clarify the transport，physical, chemical characteristics and spatial distribution law in the layer of 0-50 m during different sandstorm process, analysis the relation of the physical and chemical characteristics of particles with the underlying surface and relatively air dynamics parameter, which were collected in the surface of particle source area and sandstorm procession in the lower reaches of the Shiyan river area, set up a foundation database of the physical and chemical characteristics and source regions of the sandstorm particles in the lower reaches of Shiyan river area, provide scientific basis for the hazard assessment of the sandstorm.

沙尘是大气颗粒物的重要组成部分，因其对地球生物化学循环、地气辐射平衡、空气质量和人类健康等多方面的影响而备受关注，研究沙尘的输运规律及其理化特征对于深入了解沙尘天气的发生发展规律、改进沙尘天气预报模式、确定沙尘源地都具有重要意义。沙尘暴尘源区近地面0-50m是沙尘暴发生发展过程中沙尘颗粒物的主要分布区，也是影响人类生活最重要的区域。前期的研究发现沙尘颗粒物理化特征在近地面0-50范围存在可分辨的区域性差异，对沙尘暴研究是重要且十分缺乏的领域。本项目以建在民勤县境内不同下垫面上的近地面沙尘观测系统为观测平台，研究不同沙尘暴过程中近地面0-50m范围内沙尘输运规律及其理化特征，阐明沙尘输运规律及其理化特征的垂直梯度变化特征和水平空间分布规律所对应的下垫面特征及空气动力学参数，分析下垫面条件变化对沙尘输运规律和颗粒物理化特征的影响，为区域沙尘暴危害评估并据此提出有效的抑沙滞尘措施提供科学依据。

近地面0-50m是沙尘天气过程中沙尘颗粒物主要分布区，也是影响人类生活最重要的区域，前期研究发现沙尘颗粒物理化特征在此范围内存在可分辨的区域性差异，对沙尘暴研究是重要且十分缺乏的领域。项目严格按照任务书既定内容实施，基于近地面沙尘观测系统测量并分析了不同下垫面0-50m范围内不同高度沙尘通量、浓度(全粒径、pm10)，以及风速、湍流强度输运特征，阐明了沙尘颗粒物理化特征的垂直变化特征、水平空间分布规律及其随时间的变化关系。结果表明：（1）随高度增加颗粒物粒径及其随下垫面变化而产生的差异均逐渐减小；携沙尘气流途径下垫面特征对近地面风场结构、流体湍流特征、沙尘输运强度、输运模式及粒度的空间分布规律具有决定性影响。（2）荒漠、荒漠绿洲过渡带及绿洲内部0-50m范围内沙尘颗粒物金属元素均以Al、Na、Mg、Si、K、Ca、Fe氧化物为主，且与上风向荒漠区沙丘表面0-5cm沙粒之间存在显著的正相关性；沙尘颗粒物在传输过程中因下垫面不均一引起的各粒径级在不同高度处的沉降率差异使金属元素和重矿物含量随下垫面表现出明显的规律性变化。（3）在农田防护林林带高度以下，带间局地风速消减率在与上风向林带数量、测量点上\下风向两条林带的带间距离均有密切的关系；在林带高度以上，林带分布区U*和Z0具有区域性特征；风速沿流向的变化会在林带前后呈现突变趋势。（4）荒漠区和绿洲内部两地不同高度处风速功率谱线均随着频率增加而逐渐减低，且自荒漠区至绿洲内部惯性对流子区扩大、粘性对流子区缩小。（5）绿洲内部pm10浓度随时间的变化趋势取决于上风向沙尘源区pm10浓度。（6）建成区域性沙尘颗粒物理化特征基础数据库，对采集到的沙尘样品进行分类长期保存，为后续研究的开展积累了重要的基础资料。研究结果可以为沙尘起沙模式以及沙尘气候强迫的参数化研究及其验证提供基础资料，也将为沙尘天气尘源区的确定及区域沙尘天气危害评估并据此提出有效的抑沙滞尘措施提供科学依据。