The effects of water content on diffuse reflectance spectrophotometry studies of deep-sea sediment cores
The effects of water content on diffuse reflectance spectrophotometry studies of deep-sea sediment cores
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DOI：
10.1016/s0025-3227(98)00033-4
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发表时间：
1998-08-01
期刊：
影响因子：
2.9
通讯作者：
Damuth, JE
中科院分区：
文献类型：
--
作者：
Balsam, WL;Deaton, BC;Damuth, JE
在 ODP 钻探作业期间回收的沉积物岩心通常使用 Minolta CM-2002 分光光度计进行扫描以获得光谱数据。 JOIDES Resolution 上的岩心处理程序要求在湿岩心上测量这些光谱数据。然而，改变水含量对海洋沉积物光谱的影响尚不清楚。我们研究了含水量变化对由粘土到有孔虫软泥组成的岩心样品的可见光 (VIS) 漫反射光谱的影响。测量干粉样品的光谱，然后将样品完全饱和（类似于 35% 的含水量），并随着样品逐渐干燥以设定的时间间隔测量光谱。完全饱和的样品比初始干燥样品明显更暗。在干燥的初始阶段，样品继续变暗，直到含水量从 35% 降至大约 20%。随着水含量继续降至 20% 以下，样品逐渐变轻，并在水含量接近 17% 时获得与完全饱和样品相似的光谱值。样品继续变浅直至完全干燥；然而，数值从未变得像初始润湿之前的干燥样品那样轻。反射率随水含量降低而变化的情况在整个 VIS 中并不均匀。如果水含量大于 5%，则相对于干燥样品的反射率下降在光谱红端更大。然而，当含水量小于5%时，湿沉积物和干沉积物的光谱曲线形状相似，但湿沉积物仍然颜色更深。将这些数据与使用粗粒海滩沙进行的类似饱和度实验获得的数据进行比较表明，饱和碳酸盐沉积物的最初变暗显然是由于沉积物物理性质的变化所致；降低水分含量显然会重新排列谷物。这些研究表明，当对尽可能干燥的样品进行光谱测量时，可以获得最大的信息。 (C) 1998 Elsevier Science B.V. 保留所有权利。
Sediment cores recovered during ODP drilling operations are commonly scanned using a Minolta CM-2002 spectrophotometer to obtain spectral data. Core processing procedures aboard the JOIDES Resolution require that these spectral data be measured on wet cores. However, the effects of changing water content on the spectra of marine sediments is unknown. We examined the effects of changing water content on visible light (VIS) diffuse reflectance spectra for core samples composed of clay to foraminiferal ooze. The spectra of dry powdered samples were measured, then the samples were completely saturated (similar to 35% water content) and spectra were measured at set time intervals as the samples progressively dried. The fully saturated samples were appreciably darker than the initial dry samples. The samples continued to darken during the initial phases of drying until the water content had decreased from 35% to similar to 20%. As the water content continued to decrease below 20%, the samples became progressively lighter and attained spectral values similar to the fully saturated samples at water contents of similar to 17%. Samples continued to lighten until they were totally dry; however, values never became as light as those of the dry samples prior to initial wetting. Changes in reflectance with decreasing water content are not uniform across the VIS. If the water content is greater than 5%, the reflectance decrease relative to a dry sample is greater at the red end of the spectrum. However, at water contents of less than 5%, the spectral curves of the wet and dry sediments are similar in shape, but the wet sediments are still darker. Comparison of these data with data obtained from similar saturation experiments using a coarse-grained beach sand suggest that the initial darkening of the saturated carbonate sediments apparently results from changing of the physical properties of the sediment; decreasing the water content apparently rearranges the grains. These studies suggest that maximum information will be obtained when spectral measurements are taken on samples that are allowed to dry as much as possible. (C) 1998 Elsevier Science B.V. All rights reserved.