关键词:
青藏高原
沙尘铁
CCSEM
粒径分布
矿物组成
摘要:
长距离传输的含铁沙尘不但能够改变区域乃至全球辐射平衡,还是海洋初级生产所需营养物质的主要来源,对全球气候和环境变化有重要影响。矿物分析显示不同源区沙尘铁的空间分布和效应存在显著差异,但量化粒径相关的沙尘铁矿物组成尚缺乏有效手段。本研究借助计算机控制扫描电子显微镜(CCSEM)测定青藏高原地表风蚀释放的27,190个沙尘单颗粒,定量获得沙尘铁的数量丰度、粒径、形貌特征,及其矿物组成等信息。结果显示:(1) 高原沙尘铁单个粒子的粒径分布和形貌参数存在地域差异;(2) 绿泥石、伊利石和蛭石是高原含铁沙尘粒子的主要矿物类型,共占含铁颗粒总数的80.3%~84.1%;(3) 高原沙尘铁粒度分布的峰值粒径介于1.3~2.0 μm,而质量则富集在较粗粒子部分(3.2~7.9 μm)。CCSEM提供的微观理化定量数据可用于模式研究,提高气候和生物地球化学循环模拟的准确性。Iron-containing mineral dust aerosols can induce perturbation of regional and global radiation balance, and impact the global carbon cycle and climate change by acting as a major source of nutrients for marine primary production. The characterization of mineral dust showed spatial variations in the distributions of iron-containing particles and their potential effects on climate and environment. However, a knowledge gap remains in the size-resolved mineralogical compositions of iron-containing particles due to the lack of effective analytical methods. In this study, 27,190 individual mineral dust particles released by a simulated wind erosion process on the surface soil from the Qinghai-Xizang Plateau were determined by a computer controlled scanning electron microscopy (CCSEM) system. The quantitative results of particle size, morphology and mineral compositions of iron-containing mineral dusts show that: (1) A spatial variation remained in the particle size distribution and morphological properties of the iron-containing mineral dust particles all over the Plateau. (2) Chlorite, illite and vermiculite predominated iron-containing mineral dusts of the plateau, accounting for 80.3%~84.1% in numbers;(3) The amount of iron-containing mineral dusts is enriched in the fine particle size mode (peak size range 1.3~2.0 μm), whilst their mass is enriched in the coarse particles (3.2~7.9 μm). CCSEM is capable to provide quantitative data on the microphysical and chemical properties of iron-containing mineral dusts, which may improve the accuracy of climate and biogeochemical models.