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Jesús M. Mercado Teodoro Ramírez Dolores Corts Marta Sebastin Andreas Reul Begoa Bautista 《Estuarine, Coastal and Shelf Science》2006,69(3-4):459
The changes in the phytoplankton absorption properties during a diurnal cycle were investigated at one station located in the north-western area of the Alborán Sea. The experiment was performed in spring when the water column was strongly stratified. This hydrological situation permitted the establishment of a deep chlorophyll a (chl a) fluorescence maximum (DFM) which was located on average close to the lower limit of the mixed layer and the nutricline. The relative abundance of pico-phytoplankton (estimated as its contribution to the total chl a) was higher in the surface, however, micro-phytoplankton dominated the community at the DFM level. Chl a specific absorption coefficient (a*(λ)) also varied with optical depth, with a* (the spectrally average specific absorption coefficient) decreasing by 30% at the DFM depth with respect to the surface. A significant negative correlation between the contribution of the micro-phytoplankton to the total chl a and a* was obtained indicating that a* reduction was due to changes in the packaging effect. Below the euphotic layer, a* increased three-fold with respect to the DFM, which agrees with the expected accumulation of accessory pigments relative to chl a as an acclimation response to the low available irradiance. The most conspicuous change during the diurnal cycle was produced in the euphotic layer where the chl a concentration decreased significantly in the afternoon (from a mean concentration of 1.1 μg L−1 to 0.7 μg L−1) and increased at dusk when it averaged 1.4 μg L−1. In addition, a* and the blue-to-red absorption band ratio increased in the afternoon. These results suggest that a*(λ) diurnal variability was due to increase in photo-protective and accessory pigments relative to chl a. The variation ranges of a*(λ) at 675 and 440 nm (the absorption peaks in the red and blue spectral bands, respectively) in the euphotic layer were 0.01–0.04 and 0.02–0.10 m2 mg−1 chl a, respectively. Approximately 30% out of this variability can be attributed to the diurnal cycle. This factor should therefore be taken into account in refining primary production models based on phytoplankton light absorption. 相似文献
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冯一丁 《中国海洋大学学报(自然科学版)》1994,(3)
采用发送一束线偏振激光产生散斑的方法,研究线偏振激光散斑、"平均椭圆偏振"激光散斑以及非偏振激光散斑的相关性和精细结构。指出:当漫射器为一片毛玻璃时,散斑激光是线偏振的.其方向与入射激光束相同;当漫射器为涂无光白漆的毛玻璃时,散斑激光是部分或全部退偏的,涂层越厚,退偏越甚。对于强线偏振散斑场,当偏振方向改变时,散斑的精细结构无明显变化,即使是两个正交方向上的散斑图,也保持良好的相关性。对于非偏振散斑场,当照明激光束的偏振方向改变时.散斑精细结构有明显变化。 相似文献
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Martin Hassellv 《Marine Chemistry》2005,94(1-4):111
A new method for the characterization of chromophoric colloidal organic matter in seawater has been applied to samples from the Baltic Sea, Kattegatt and Skagerrak seas. Size fractionation of the sample by Flow Field-Flow Fractionation and measurement of the fluorescent and UV absorbing properties of the individual size fractions result in a relative molar mass distribution (RMM) of the optical properties. The RMM distributions have been used to estimate number and weight average relative molar masses, and polydispersity indices. At least two sources of coloured organic matter were identified from the ratio of fluorescence to UV: the Baltic surface water and the Skagerrak deep water. The dominating processes were mixing and dilution, but processes such as photo bleaching of fluorescence are also believed to be important. The RMM distribution derived from UV detection (1150–1300 Dalton) increased with increasing salinity while that derived for fluorescence (1500–1250 Dalton) decreased with increasing salinity. The specific UV absorbance taken as a proxy of the aromaticity of the chromophoric organic material showed decreasing trend with both increasing salinity and increasing UV derived weight average relative molar mass. Increasing polydispersity of the colloidal material was also observed as a function of salinity. 相似文献
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黄河口附近海域化学需氧量和石油烃分布及其关键控制环境因子分析 总被引:1,自引:0,他引:1
于2009年12月、2010年5月、2011年9月、2013年5月和2014年10月,在黄河口附近海域进行了5个航次调查,研究了该海域的化学需氧量(COD)和石油烃的分布情况以及季节变化。结果表明,COD整体呈冬季低、春季高的趋势,而石油烃无明显季节变化趋势。平面分布上,春季和秋季COD高值主要分布在靠近黄河口海域。春季和冬季石油烃高值主要位于调查海域的东北部区域。相关分析结果表明盐度、温度、pH、悬浮物、溶解氧及磷酸盐是影响COD的主要环境因素,而石油烃主要受盐度、温度、pH、无机氮、磷酸盐的影响。进一步多元回归分析结果表明,p H、盐度和溶解氧是影响COD的关键因子,温度是影响石油烃的关键因子。 相似文献
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应用勘探层分析及石油资源专家系统对XH凹陷下第三系勘探目的层的三个勘探层烃资源量作出了综合预测,结果表明,凹陷内各勘探层,尤其是渐新统勘探层,烃资源量相当可观。提出在渐新统内的地层圈闭中可进一步作详细的勘探工作。 相似文献
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The Kimmeridge Clay is considered a major oil source rock for the North Sea hydrocarbon province. The formation is also developed onshore in an organic-rich mudstone facies. This paper examines the possibility of onshore oil generation from the Kimmeridge Clay. Geochemically, onshore basin margin sediments contain rich, potential source horizons with mainly Type l/Type ll oil-prone kerogen, but are immature. Some deeper Cleveland Basin sediments have reached marginal maturity. Burial history reconstruction suggests significant formation palaeoburial depths in central areas of the Cleveland and Wessex Basins. Computed vitrinite isoreflectance contours show the Wealden and Isle of Wight Kimmeridge Clay to be thermally mature. Basin modelling suggests an early Palaeogene onset of oil generation in parts of the Cleveland Basin, while maximum oil generation could have been reached by the formation base in the Isle of Wight area during the late Cretaceous. Although basin subsidence ceased in the Neogene, in the Weald and Isle of Wight, where the formation is still deeply buried, oil generation probably continued for some time during uplift. Thus significant quantities of oil could have been generated. Whether or not this oil is present today however, would depend on the correct timing of suitable migration and trap structures. 相似文献
20.
在南海北部利用地球化学方法作为油气勘探的一种辅助手段。在6个航次中采集了沉积物、底层海水及海面大气样品,测定了近50种化探指标,并采用稳健统计方法进行了数据处理和异常圈定。化探结果在油气藏上方发现了清晰的、具不同指标组合的综合化探异常,与邻近空构造形成鲜明的对照。圈闭顶部的块状异常和圈闭周绿的环状、半环状异常是下伏油气藏的良好指示,而剖面上呈锯齿状、平面上呈线状的异常则与断裂带有关。实践表明,建立已知油气藏上方的化探异常模式及解剖已知空构造上方的地球化学特征对于指导本区或邻区的化探异常评价是十分必要的。 相似文献