Tzortziou Maria, Osburn Christopher L, Neale Patrick J
Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA.
Photochem Photobiol. 2007 Jul-Aug;83(4):782-92. doi: 10.1111/j.1751-1097.2007.00142.x.
Wetlands and tidal marshes in the Rhode River estuary of the Chesapeake Bay act as important sources of dissolved organic carbon and strongly absorbing dissolved organic matter (DOM) for adjacent estuarine waters. The effects of solar exposure on the photochemical degradation of colored DOM (CDOM) were examined for material derived from different sources (estuarine and freshwater parts of the Rhode River, sub-watershed stream, marshes) in this estuarine ecosystem. Consistent with changes in fluorescence emission, absorption loss upon exposure to different portions of the solar spectrum (i.e. different long-pass cut-off filters) occurred across the entire spectrum but the wavelength of maximum photobleaching decreased as the cut-off wavelength of the filter decreased. Our results illustrate that solar exposure can cause either an increase or a decrease in the CDOM absorption spectral slope, S(CDOM), depending on the spectral quality of irradiation and, thus, on the parameters (e.g. atmospheric composition, concentration of UV-absorbing water constituents) that affect the spectral characteristics of the light to which CDOM is exposed. We derived a simple spectral model for describing the effects of solar exposure on CDOM optical quality. The model accurately, and consistently, predicted the observed dependence of CDOM photobleaching on the spectral quality of solar exposure.
切萨皮克湾罗德河河口的湿地和潮汐沼泽是溶解有机碳的重要来源，并且对邻近河口水体中的溶解有机物（DOM）具有很强的吸附作用。在这个河口生态系统中，研究了太阳光照对来自不同来源（罗德河河口和淡水区域、次流域溪流、沼泽）的有色溶解有机物（CDOM）光化学降解的影响。与荧光发射的变化一致，暴露于太阳光谱的不同部分（即不同的长波截止滤光片）时，整个光谱范围内都会发生吸收损失，但最大光漂白波长会随着滤光片截止波长的减小而降低。我们的研究结果表明，根据辐照的光谱质量，进而取决于影响CDOM所暴露光的光谱特性的参数（例如大气成分、吸收紫外线的水体成分浓度），太阳光照可能会导致CDOM吸收光谱斜率S(CDOM)增加或减少。我们推导了一个简单的光谱模型来描述太阳光照对CDOM光学质量的影响。该模型准确且一致地预测了观察到的CDOM光漂白对太阳光照光谱质量的依赖性。
