Dust Deposited on Snow Cover in the San Juan Mountains, Colorado, 2011–2016: Compositional Variability Bearing on Snow‐Melt Effects
Dust Deposited on Snow Cover in the San Juan Mountains, Colorado, 2011–2016: Compositional Variability Bearing on Snow‐Melt Effects
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DOI：
10.1029/2019jd032210
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
R. Reynolds;H. Goldstein;B. Moskowitz;R. Kokaly;S. Munson;P. Solheid;G. Breit;C. Lawrence;J. De
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文献类型：
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作者：
R. Reynolds;H. Goldstein;B. Moskowitz;R. Kokaly;S. Munson;P. Solheid;G. Breit;C. Lawrence;J. De
大气尘埃中的吸光粒子沉积在积雪上（雪上尘埃，DOS）降低了反照率，加速了雪融化的时间和速度。这些颗粒及其影响的识别与雪辐射模型和水资源管理有关。对美国圣胡安山脉DOS样品的实验室测量反射率与DOS的质量载荷、粒度、铁矿物学、碳质物质类型和含量以及化学成分进行了比较。在2011-2016年的水年里，每年春天都会收集样本，当时单个尘埃层在雪表面合并为一个（所有层合并）。6种样品在可见光波段（0.4-0.7 μm）内的平均反射率为0.2153 (sd, 0.0331)，在全测量范围（0.4-2.50 μm）内的平均反射率为0.3570 （sd, 0.0498）。反射率值与氧化铁、有机碳（1.4-10 wt.%）、磁铁矿（0.05-0.13 wt.%）和粉砂（PM63 - 3.9，中位粒径平均为21.4 μm）的浓度呈负相关，但与总铁和PM10含量缺乏对应关系。反射率、Mössbauer光谱和磁性能的测量表明，微晶赤铁矿和纳米针铁矿是可见光反射率降低的主要原因。化石燃料燃烧产生的有机碳和金属之间存在正相关关系，通过电镜观察表明，一些含碳物质以黑碳的形式出现。磁铁矿是相关吸光矿物、深色岩石颗粒和污染物的替代品。对其他地区DOS的类似分析将有助于评估不同沙尘源、风暴模式和人为输入对科罗拉多河流域内外融雪和水资源的影响。
Light‐absorbing particles in atmospheric dust deposited on snow cover (dust‐on‐snow, DOS) diminish albedo and accelerate the timing and rate of snow melt. Identification of these particles and their effects is relevant to snow‐radiation modeling and water‐resource management. Laboratory‐measured reflectance of DOS samples from the San Juan Mountains (USA) were compared with DOS mass loading, particle sizes, iron mineralogy, carbonaceous matter type and content, and chemical compositions. Samples were collected each spring for water years 2011–2016, when individual dust layers had merged into one (all layers merged) at the snow surface. Average reflectance values of the six samples were 0.2153 (sd, 0.0331) across the visible wavelength region (0.4–0.7 μm) and 0.3570 (sd, 0.0498) over the full‐measurement range (0.4–2.50 μm). Reflectance values correlated inversely to concentrations of ferric oxide, organic carbon (1.4–10 wt.%), magnetite (0.05–0.13 wt.%), and silt (PM63‐3.9; median grain sizes averaged 21.4 μm) but lacked correspondence to total iron and PM10 contents. Measurements of reflectance and Mössbauer spectra and magnetic properties indicated that microcrystalline hematite and nano‐size goethite were primarily responsible for diminished visible reflectance. Positive correlations between organic carbon and metals attributed to fossil‐fuel combustion, with observations from electron microscopy, indicated that some carbonaceous matter occurred as black carbon. Magnetite was a surrogate for related light‐absorbing minerals, dark rock particles, and contaminants. Similar analyses of DOS from other areas would help evaluate the influences of varied dust sources, wind‐storm patterns, and anthropogenic inputs on snow melt and water resources in and beyond the Colorado River Basin.