Spectrofluorometric Applications in Studying Macroalgal Exudates*     

Jozo Dujmov  Perica Su evi&#x;  Boris Antoli&#x; 《Marine Ecology》1996,17(1-3):501-508

Abstract. In this paper we present a one-year investigation on the fluorescence characteristics of released products of selected Adriatic seaweeds. The technique chosen was UV-fluorescence spectroscopy with the synchronous mode, which involves the stepping of the excitation and emission monochromators. The five species, of representative macrophytes, Cystoseira compressa, Dictyopreris polypodioides, Gracilaria bursapastoris, Pterocladia capillacea, and Ulva rigida, were chosen on the basis of their dominance in the plant communities typical for the area near Split - Central Adriatic. Our results suggest that macroalgal-related dissolved fluorescent matter can be categorized into two distinct groups of fluorescing compounds with the following excitation wavelengths: one from 320–360 nm, probably for compounds with 2 fused aromatic rings, and another from 360–420 nm, corresponding with 3 & 4 fused rings. The contribution of aromatics with 2 and with 3 & 4 rings was very similar in the brown algae Cysroseira compressa and Dictyopteris polypodioides, while in the red algae Gracilaria bursapastoris and Pterocludia capillacea as well in the green alga Ulva rigida the group with 2 rings dominated.  相似文献   

Development of a fluorescence quenching assay to measure the fraction of organic carbon present in self-assembled gels in seawater     

Yong-Xue Ding  Wei-Chun Chin  Pedro Verdugo   《Marine Chemistry》2007,106(3-4):456-462

The dissolved organic carbon pool (DOC) is among the largest reservoir of reduced carbon on our planet. The demonstration that DOC polymers remain in assembly/dispersion equilibrium forming microscopic hydrogels has a broad range of critical implications. Previous studies estimate that  10% of DOC could be assembled as gels, yielding values of  7 × 10¹⁶ g of organic carbon present as microscopic hotspots of high substrate concentration. This huge mass of reduced carbon emphasizes the need to develop reliable methods to systematically investigate the budget of self-assembled marine gels (SAG), and their role in biogeochemical cycling. However, a quantitative method to measure SAG in seawater has not been available. Here we present the validation of a simple assay to measure the mass of organic carbon assembled as microgels in native seawater. This method is based on the ratio of Chlortetracycline (CTC) fluorescence quenching between Ca bound to non-assembled organic molecules and molecules assembled as microgels. This assay can be readily implemented on board using a low cost fluorometer and provisions to measure TOC.  相似文献   

腾格里沙漠昂格尔图湖记录的988 AD以来的古气候变化          下载免费PDF全文

曹志宏  安成邦  尹丽颖  段阜涛  郝盛吞  周爱锋 《干旱区地理》2018,41(6):1251-1259

通过对腾格里沙漠东南部昂格尔图湖岩芯AGE15A的粒度、碳酸盐的百分含量和主要化学元素等多项沉积学气候代用指标及精确定年的综合分析,重建了该区域988 AD以来的古气候变化序列。结果表明：988 AD以来的研究区的气候环境的演化过程与我国西北西风区古气候变化基本一致,呈现"冷湿-暖干"交替变化的特征,但在时间上存在一定的延迟。具体表现为：988~1383 AD,昂格尔图湖由洼地发育成小型湖泊,化学风化作用弱,湖区气候环境整体偏冷湿,期间出现几次暖波动;1383~1560 AD,研究区处在中世纪暖期,为温暖、干旱的气候特征,此时湖泊扩张,湖中水生植物生长茂盛,呼吸作用增强,造成大量的碳酸盐沉淀,最高值达到8.16%;1560~1700 AD,致使气候在昂格尔图湖形成之后出现最寒冷的时期,降水增加,气候湿冷,此时段与小冰期最盛期相对应;1700 AD之后,温度开始上升,气候回暖,在1900 AD左右达到最甚,此时沉积物中碳酸盐的百分含量也达到最大值,为10.15%,此期间湖泊继续扩张,出现几次气候冷波动。基于我国古代文献重建的历史时期气候变化基本不包括沙漠地区,所以本文利用湖相沉积记录来反演腾格里沙漠昂格尔图湖历史时期的气候环境演变,对中国沙漠研究有着重要参考价值,同时也为中国西北历史时期的气候重建提供科学依据。  相似文献   

Assessing the benefit of satellite-based Solar-Induced Chlorophyll Fluorescence in crop yield prediction     

《International Journal of Applied Earth Observation and Geoinformation》2020

Large-scale crop yield prediction is critical for early warning of food insecurity, agricultural supply chain management, and economic market. Satellite-based Solar-Induced Chlorophyll Fluorescence (SIF) products have revealed hot spots of photosynthesis over global croplands, such as in the U.S. Midwest. However, to what extent these satellite-based SIF products can enhance the performance of crop yield prediction when benchmarking against other existing satellite data remains unclear. Here we assessed the benefits of using three satellite-based SIF products in yield prediction for maize and soybean in the U.S. Midwest: gap-filled SIF from Orbiting Carbon Observatory 2 (OCO-2), new SIF retrievals from the TROPOspheric Monitoring Instrument (TROPOMI), and the coarse-resolution SIF retrievals from the Global Ozone Monitoring Experiment-2 (GOME-2). The yield prediction performances of using SIF data were benchmarked with those using satellite-based vegetation indices (VIs), including normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and near-infrared reflectance of vegetation (NIRv), and land surface temperature (LST). Five machine-learning algorithms were used to build yield prediction models with both remote-sensing-only and climate-remote-sensing-combined variables. We found that high-resolution SIF products from OCO-2 and TROPOMI outperformed coarse-resolution GOME-2 SIF product in crop yield prediction. Using high-resolution SIF products gave the best forward predictions for both maize and soybean yields in 2018, indicating the great potential of using satellite-based high-resolution SIF products for crop yield prediction. However, using currently available high-resolution SIF products did not guarantee consistently better yield prediction performances than using other satellite-based remote sensing variables in all the evaluated cases. The relative performances of using different remote sensing variables in yield prediction depended on crop types (maize or soybean), out-of-sample testing methods (five-fold-cross-validation or forward), and record length of training data. We also found that using NIRv could generally lead to better yield prediction performance than using NDVI, EVI, or LST, and using NIRv could achieve similar or even better yield prediction performance than using OCO-2 or TROPOMI SIF products. We concluded that satellite-based SIF products could be beneficial in crop yield prediction with more high-resolution and good-quality SIF products accumulated in the future.  相似文献   

Size fractionation and optical properties of colloids in an organic-rich estuary (Thurso, UK)   总被引：2，自引：0，他引：2  

Silvia Batchelli  Franois L.L. Muller  Mohamed Baalousha  Jamie R. Lead 《Marine Chemistry》2009,113(3-4):227-237

The optical characteristics of a black water river estuary from the north coast of Scotland were examined in the filtered (0.4 µm), ultrafiltered (5 kDa) and colloid-enriched fractions of estuarine samples. The samples were collected over the full salinity range during a period when the pH was relatively constant (8.2–8.5) throughout the estuary, allowing the influence of salinity on estuarine colloidal processes to be distinguished. The properties examined in the bulk, the low molecular weight (LMW) and the colloidal fraction (HMW) were UV–visible absorption, 3-D fluorescence excitation–emission matrix (EEM) spectrum, inorganic and organic carbon, mean size (by dynamic light scattering), and size distribution by flow field-flow fractionation analysis (FlFFF). The combined results of these analyses support the view that river-borne, humic-rich colloids underwent two types of transformation upon mixing with the seawater end member. The first one resulted in an apparent increase in the abundance of LMW constituents and may be explained by coiling of the individual humic macromolecules. The second one resulted in an increase in the mean size measured in both the lower and higher colloidal size ranges, and may be explained by aggregation of colloids to form entities that were still mostly colloidal i.e., smaller than 0.4 µm. The LMW contribution to the bulk optical properties increased with increasing salinity. Very similar findings were obtained from simulated mixing experiments using a Nordic Reference NOM extract as a source of freshwater colloids. This indicates that changes in the molecular architecture and molar mass of river-borne colloids—not changes in their chemical nature—were responsible for the observed variations in the spectral characteristics of CDOM in this estuary.  相似文献   

高原湖泊溶解有机质的三维荧光光谱特性初步研究   总被引：9，自引：0，他引：9  

傅平青  吴丰昌  刘丛强  黎文  白英臣  廖海清  陈静 《海洋与湖沼》2007,38(6):512-520

提要近年来,荧光光谱技术被广泛应用于研究天然水体中溶解有机质(Dissolved Organic Matter,DOM)的物理化学特性。为了理解高原湖泊中DOM的组成、荧光光谱特性及其在湖泊水体中的垂直分布情况,作者利用荧光发射光谱、三维荧光光谱研究云贵高原湖泊红枫湖和百花湖中的DOM。结果显示,高原湖泊DOM主要表现为类富里酸荧光,包括可见区和紫外区两种类型的荧光峰,各种天然水体中都有报道的类蛋白荧光在红枫湖DOM中并不明显,而在百花湖DOM中则有较强的类蛋白荧光。溶解有机质所含三种类型荧光峰(PeakA:紫外区类富里酸荧光峰;PeakB:可见区类富里酸荧光峰;PeakC:类蛋白荧光峰)的荧光强度与溶解有机碳之间没有明显的线性相关关系,可能与高原湖泊水体pH值、DOM在湖泊不同深度由于受到光降解、微生物降解等作用存在差异等因素有关。与有机质结构和成熟度有关的荧光峰比值r(A,C)在1.40—2.09范围内,红枫湖南湖、百花湖DOM样品的r(A,C)值随着水体深度有下降的趋势,而红枫湖北湖DOM的r(A,C)值则随着水体深度有较大起伏,揭示了高原湖泊水体中DOM的结构以及分布情况存在差异。另外,r(A,C)值与pH之间具有良好的正相关关系,其相关系数红枫湖南湖DOM为0.95,百花湖两个采样点DOM分别为0.67、0.75,而红枫湖北湖DOM则显示出一定的负相关性(R2=0.45)。  相似文献   

海水黄色物质荧光特性的初步研究   总被引：17，自引：5，他引：17  

夏达英  李宝华  吴永森  张绪琴  吴隆业  张士魁 《海洋与湖沼》1999,30(6):719-725

用荧光测量方法,对被认为可作本底水样的几种水体进行了荧光特性的测量研究。确认了即时处理的Ｍｉｌｌｉ－Ｑ我荧光效应的高纯度水,可作为本研究的本底水样。同时,对海水黄色ｉｌｌｉ－Ｑ水溶液,市售草炭腐殖质Ｍｉｌｌｉ－Ｑ水溶液,青岛近岸海水和褐藻培养液样品进行了光谱特性测量研究。结果表明,海水黄色物质和培养液的黄色物质的激发光谱峰值波长在３４０ｎｍ附近,荧光光谱峰值波长在４３５ｎｍ附近,而草炭腐殖质的激发  相似文献   

高碳铬铁EDXRF分析中的制样条件优化          下载免费PDF全文

李欣倩  冯海涛  李波  高丹丹  张波  董亚萍  李武 《盐湖研究》2021,29(2):102-108

利用能量色散X射线荧光光谱分析技术(EDXRF)检测高碳铬铁,能实现对主次组分的同时测量,且无需对铬铁样品进行化学处理.实验以荧光强度和测试精密度为指标,采用单因素试验考察了粉末压片制样过程中称样量、粘结剂种类与用量、研磨时间、压片压力、保压时间等制样条件对测量结果的影响趋势,并将优化后的条件用于对高碳铬铁的检测.结果...  相似文献   

Yellow fluorescence from baghdadite and synthetic Ca3(Zr,Ti)Si2O9     

Aierken Sidike  I. Kusachi  N. Yamashita 《Physics and Chemistry of Minerals》2006,32(10):665-669

Baghdadite from Fuka, Okayama Prefecture, Japan shows a bright yellow fluorescence under UV (Hg 253.7 nm) excitation. The photoluminescence (PL) spectrum at 300 K consists of one large band near 580 nm and two small UV bands at 318 and 397 nm. The optical excitation spectrum of the bright yellow fluorescence consists of two bands near 220 and 250 nm. The temperature dependence of the PL intensity exhibits linear thermal quenching. To reveal the origin of the bright yellow fluorescence from baghdadite, powder Ca₃(Zr,Ti)Si₂O₉ crystals are synthesized. Synthetic Ca₃(Zr,Ti)Si₂O₉ shows luminescence spectra similar to those of baghdadite, and the intensity of the yellow fluorescence is markedly increased by titanium addition. The origin of the bright yellow fluorescence from baghdadite is ascribed to the existence of titanium.  相似文献   

原子荧光光度法测定土壤样品中砷的不确定度评定   总被引：1，自引：0，他引：1  

蔡玉曼  赵斌徐霞 《江苏地质》2005,29(4):228-231

通过原子荧光光度法对土壤样品中砷重复测定6次，计算实验标准差，同时对测试过程系统效应产生的不确定度分量进行评估，从而评定其不确定度。  相似文献