Peng Feng, Effler Steven W, O'Donnell David, Perkins Mary Gail, Weidemann Alan
Upstate Freshwater Institute, Syracuse, NY 13214, USA.
Appl Opt. 2007 Sep 10;46(26):6577-94. doi: 10.1364/ao.46.006577.
The role of minerogenic particles in light scattering in several lakes and a river (total of ten sites) in central New York, which represent a robust range of scattering conditions, was evaluated based on an individual particle analysis technique of scanning electron microscopy interfaced with automated x-ray microanalysis and image analysis (SAX), in situ bulk measurements of particle scattering and backscattering coefficients (bp and bbp), and laboratory analyses of common indicators of scattering. SAX provided characterizations of the elemental x-ray composition, number concentration, particle size distribution (PSD), shape, and projected area concentration of minerogenic particles (PAVm) of sizes>0.4 microm. Mie theory was applied to calculate the minerogenic components of bp (bm) and bbp (bb,m) with SAX data. Differences in PAVm, associated primarily with clay minerals and CaCO3, were responsible for most of the measured differences in both bp and bbp across the study sites. Contributions of the specified minerogenic particle classes to bm were found to correspond approximately to their contributions to PAVm. The estimates of bm represented substantial fractions of bp, whereas those of bb,m were the dominant component of bbp. The representativeness of the estimates of bm and bb,m was supported by their consistency with the bulk measurements. Greater uncertainty prevails for the bb,m estimates than those for bm, associated primarily with reported deviations in particle shapes from sphericity. The PSDs were well represented by the "B" component of the two-component model or a three parameter generalized gamma distribution [Deep-Sea Res. Part I 40, 1459 (1993)]. The widely applied Junge (hyperbolic) function performed poorly in representing the PSDs and the size dependency of light scattering in these systems, by overrepresenting the concentrations of submicrometer particles especially. Submicrometer particles were not important contributors to bm or bb,m.
在纽约中部的几个湖泊和一条河流(共十个地点)中,基于扫描电子显微镜与自动X射线微分析和图像分析(SAX)的个体颗粒分析技术、颗粒散射和后向散射系数(bp和bbp)的原位总体测量以及散射常见指标的实验室分析,评估了成矿颗粒在光散射中的作用,这些地点代表了广泛的散射条件范围。SAX提供了尺寸大于0.4微米的成矿颗粒(PAVm)的元素X射线组成、数量浓度、颗粒大小分布(PSD)、形状和投影面积浓度的特征。利用SAX数据,应用米氏理论计算bp(bm)和bbp(bb,m)的成矿成分。PAVm的差异主要与粘土矿物和碳酸钙有关,是研究地点间bp和bbp测量差异的主要原因。发现特定成矿颗粒类别对bm的贡献与其对PAVm的贡献大致相当。bm的估计值占bp的很大比例,而bb,m的估计值是bbp的主要组成部分。bm和bb,m估计值的代表性得到了它们与总体测量结果一致性的支持。bb,m估计值的不确定性比bm估计值更大,这主要与报道的颗粒形状偏离球形有关。PSD由双组分模型的“B”组分或三参数广义伽马分布很好地表示[《深海研究》第一部分40, 1459 (1993)]。广泛应用的容格(双曲线)函数在表示这些系统中的PSD和光散射的尺寸依赖性方面表现不佳,尤其是过度表示了亚微米颗粒的浓度。亚微米颗粒对bm或bb,m的贡献不大。