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1.
The isolation and characterisation of marine dissolved organic matter (DOM) are still not readily achieved today. The study of this chemically complex material is particularly difficult, especially as it is hindered by the high salinity of seawater. It is therefore essential to develop a method in which a sufficient quantity of marine organic matter can be collected for structural analyses. Reverse osmosis (RO) is often used for the concentration of DOM from freshwaters, due to the fact that DOM is not modified during RO and that DOC recoveries are high (about 80%). Unfortunately, RO cannot be used directly to isolate marine DOM, since both salts and organic matter are concentrated during the process. Therefore, marine samples have to be desalted before their concentration by RO. 相似文献
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3.
J. Hernández-Borges M. A. Rodríguez-Delgado F. J. García-Montelongo 《Chromatographia》2006,63(3-4):155-160
Several improvements in sample pretreatment for the determination of organic pollutants (i.e. n-alkanes, polycyclic aromatic hydrocarbons, PAHs) in marine biota (mussels) are presented. The use of liquid nitrogen and
homogenization of the samples are shown to be an alternative to the time consuming liophilization step required for the analysis
of biota samples. Microwave-assisted hydrolysis and extraction are combined to isolate organic pollutants (19 n-alkanes and 27 PAHs) from biota matrices. Experimental design (ED) and artificial neural networks (ANNs) were used to optimize
the experimental conditions. NIST-CRM 2978 was used to test the validity of the developed method which shows a good agreement
with certified values. 相似文献
4.
Organic peroxy radicals (often abbreviated RO(2)) play a central role in the chemistry of the Earth's lower atmosphere. Formed in the atmospheric oxidation of essentially every organic species emitted, their chemistry is part of the radical cycles that control the oxidative capacity of the atmosphere and lead to the formation of ozone, organic nitrates, organic acids, particulate matter and other so-called secondary pollutants. In this review, laboratory studies of this peroxy radical chemistry are detailed, as they pertain to the chemistry of the atmosphere. First, a brief discussion of methods used to detect the peroxy radicals in the laboratory is presented. Then, the basic reaction pathways - involving RO(2) unimolecular reactions and bimolecular reactions with atmospheric constituents such as NO, NO(2), NO(3), O(3), halogen oxides, HO(2), and other RO(2) species - are discussed. For each of these reaction pathways, basic reaction rates are presented, along with trends in reactivity with radical structure. Focus is placed on recent advances in detection methods and on recent advances in our understanding of radical cycling processes, particularly pertaining to the complex chemistry associated with the atmospheric oxidation of biogenic hydrocarbons. 相似文献
5.
溶解有机物对控制海洋和淡水水生系统的化学、生物和物理特性有重要的影响.光化学降解溶解有机物改变了生态体系的溶解有机碳、有机物的分子量及光学特性,并且产生复杂的反应性氧化合物、二氧化碳、一氧化碳、小分子量的有机酸、氨基酸、二硫化碳等,对生物过程有重要的影响.本文简要综述了光化学降解溶解有机物的过程机理及其对生物过程的影响. 相似文献
6.
《Arabian Journal of Chemistry》2014,7(1):5-9
For almost all of 4.5 billion years, natural forces have shaped Earth’s environment. But, during the past century, as a result of the Industrial Revolution, which has had enormous benefits for humans, the effects of human activities have become the main driver for climate change. The increase of atmospheric carbon dioxide caused by burning fossil fuels for energy to power the revolution causes an energy imbalance between incoming solar radiation and outgoing planetary emission. The imbalance is warming the planet and causing the atmosphere and oceans to warm, ice to melt, sea level to rise, and weather extremes to increase. In addition, dissolution of part of the carbon dioxide in the oceans is causing them to acidify, with possible negative effects on marine biota. As citizens of an interconnected global society and scientists who have the background to understand climate change, we have a responsibility first to understand the science. One resource that is available to help is the American Chemical Society Climate Science Toolkit, www.acs.org/climatescience. With this understanding our further responsibility as citizen scientists is to engage others in deliberative discussions on the science, to take actions ourselves to adapt to and mitigate human-caused climate change, and urge others to follow our example. 相似文献
7.
Advances in water chemistry in the last decade have improved our knowledge about the genesis, composition, and structure of dissolved organic matter, and its effect on the environment. Improvements in analytical technology, for example Fourier-transform ion cyclotron (FT-ICR) mass spectrometry (MS), homo and hetero-correlated multidimensional nuclear magnetic resonance (NMR) spectroscopy, and excitation emission matrix fluorimetry (EEMF) with parallel factor (PARAFAC) analysis for UV–fluorescence spectroscopy have resulted in these advances. Improved purification methods, for example ultrafiltration and reverse osmosis, have enabled facile desalting and concentration of freshly collected DOM samples, thereby complementing the analytical process. Although its molecular weight (MW) remains undefined, DOM is described as a complex mixture of low-MW substances and larger-MW biomolecules, for example proteins, polysaccharides, and exocellular macromolecules. There is a general consensus that marine DOM originates from terrestrial and marine sources. A combination of diagenetic and microbial processes contributes to its origin, resulting in refractory organic matter which acts as carbon sink in the ocean. Ocean DOM is derived partially from humified products of plants decay dissolved in fresh water and transported to the ocean, and partially from proteinaceous and polysaccharide material from phytoplankton metabolism, which undergoes in-situ microbial processes, becoming refractory. Some of the DOM interacts with radiation and is, therefore, defined as chromophoric DOM (CDOM). CDOM is classified as terrestrial, marine, anthropogenic, or mixed, depending on its origin. Terrestrial CDOM reaches the oceans via estuaries, whereas autochthonous CDOM is formed in sea water by microbial activity; anthropogenic CDOM is a result of human activity. CDOM also affects the quality of water, by shielding it from solar radiation, and constitutes a carbon sink pool. Evidence in support of the hypothesis that part of marine DOM is of terrestrial origin, being the result of a long-term carbon sedimentation, has been obtained from several studies discussed herein. 相似文献
8.
Martínez Vidal JL Belmonte Vega A Garrido Frenich A Egea González FJ Arrebola Liebanas FJ 《Analytical and bioanalytical chemistry》2004,379(1):125-130
This work describes the optimisation of a method to determinate fifteen phenolic compounds in waters, sediments and biota (green marine algae) by liquid chromatography coupled to mass spectrometry (LC-MS) with atmospheric pressure chemical ionisation (APCI) in the negative mode. The LC separations of the studied compounds and their MS parameters were optimised in order to improve selectivity and sensitivity. Separation was carried out with a C18 column using methanol and 0.005% acid acetic as mobile phase in gradient mode. The molecular ion was selected for the quantitation in selective ion monitoring (SIM) mode. A solid-phase extraction (SPE) method was applied in order to preconcentrate the target analytes from water samples. However, extraction of the compounds from sediment and biota samples was carried out by liquid–solid extraction with methanol/water after studying the influence of other organic solvents. In addition, a clean-up step by SPE with HLB Oasis cartridges was necessary for sediments and biota. The proposed analytical methodology was validated in the target environmental matrices by the analysis of spiked blank matrix samples. Detection limits were 10–50 ng L–1 for water, 1–5 g kg–1 for sediments and 2.5–5 g kg–1 for biota samples. Good recoveries and precision values were obtained for all matrices. This methodology has been successfully applied to the analysis of incurred water, sediment and biota samples from Andalusia (Spain). 相似文献
9.
P Fernández C Porte D Barceló J M Bayona J Albaigés 《Journal of chromatography. A》1988,456(1):155-164
An improved two-step clean up procedure involving alumina-silica column chromatography and gel permeation chromatography (GPC) of air particulate matter (NBS SRM 1648) and river sediment extracts and a GPC clean up procedure for marine biota samples are described for the determination of polycyclic aromatic hydrocarbons with two to five rings and selected polychlorinated biphenyl congeners, respectively. Bio-Beads SX-12 and SX-3 were used as packing materials. The recoveries obtained varied from 52 to 78% depending on the compound. Quantitative data for NBS SRM 1648 were comparable with those described previously for this sample. 相似文献
10.
K. Delbeke L. Zhu M. Muqtadir M. Khaled 《International journal of environmental analytical chemistry》2013,93(1-4):131-145
Abstract Important seasonal variations in contamination levels of marine biota by lipophile organic compounds are noted when overviewing pollution data, even when data are normalized on lipid content. We therefore tried to understand part of the observed variations in contamination levels between watermasses (different geographic areas or seasons) by studying lipophile pollutant bioconcentration at the origin of the food chain. The uptake kinetics and bioconcentration of 14C-DDT, by five species of marine phytoplankton were investigated in laboratory experiments. An inverse relationship, representative for all species studied, was noted between the phytoplankton bioconcentration factor and the phytoplankton biomass (both normalized on organic carbon). No differences in bioconcentration factors among different phytoplankton species, with different cell sizes and biochemical characteristics, were noted, when data were standardized on organic carbon content. The importance of the Particle Concentration Effect (PCE) on the bioconcentration factor of micro-organic pollutants is, in this study, further illustrated with data on pollution of North Sea field samples. It is shown that within a specific range of organic matter, normalization of pollution data on particulate or phytoplankton biomass will account for part of the geographic and seasonal differences in organochlorine contamination levels noted for marine watermasses. 相似文献
11.
Orilall MC Abrams NM Lee J DiSalvo FJ Wiesner U 《Journal of the American Chemical Society》2008,130(28):8882-8883
A combined assembly of soft and hard chemistries is employed to generate highly crystalline three-dimensionally ordered macroporous (3DOM) niobia (Nb2O5) and titania (TiO2) structures by colloidal crystal templating. Polystyrene spheres with sp2 hybridized carbon are used in a reverse-template infiltration technique based on the aqueous liquid phase deposition of the metal oxide in the interstitial spaces of a colloidal assembly. Heating under inert atmosphere as high as 900 degrees C converts the polymer into sturdy carbon that acts as a scaffold and keeps the macropores open while the oxides crystallize. Using X-ray diffraction it is demonstrated that for both oxides this approach leads to highly crystalline materials while heat treatments to lower temperatures commonly used for polymer colloidal templating, in particular for niobia, results in only weakly crystallized materials. Furthermore it is demonstrated that heat treatment directly to higher temperatures without generating the carbon scaffold leads to a collapse of the macrostructure. The approach should in principle be applicable to other 3DOM materials that require heat treatments to higher temperatures. 相似文献
12.
Arne Krtzinger 《Chemie in Unserer Zeit》2010,44(2):118-129
By burning of fossil fuels humankind emits more than 8 billion tons of carbon (Gt C) in the form of CO2 to the atmosphere. Since the onset of the industrial revolution the cumulative emissions have led to an increase of the atmospheric CO2 concentration which corresponds to an additional radiative forcing in the atmosphere. Of the three reservoirs which exchange carbon on the time scale of centuries – atmosphere, terrestrial biosphere, and ocean – the ocean is by far the largest. The marine CO2 system comprises the chemical species HCO3–, CO32–, and CO2(aq). This gives rise to the pH‐buffering nature of seawater as well as its high uptake capacity for anthropogenic CO2. Four measurement parameters of the marine CO2 system are available for an accurate analytical characterization. These parameters also provide a means of sensing the role of physical, chemical, and biological drivers for the marine carbon cycle. The marine carbon cycle features major natural processes that exchange carbon with the atmosphere and re‐distribute it throughout the ocean. These are known as “pumps” and driven by physical and biological factors. While the “physical pump” is inevitably enhanced by the oceanic uptake of anthropogenic CO2, even the sign of the response is currently not clear for the “biological pumps”. A host of potential consequences of global change (temperature rise, ocean carbonation, ocean acidification) have been identified. These are currently studied intensively with respect to their climate sensitivity as well as the climate feedback potential. 相似文献
13.
Guang-hua Wang You-shi Zeng Jian Yao Yuan Qian Yu Huang Ke Liu Wei Liu Yan Li 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1545-1552
A method was established to quantitatively estimate sources of atmospheric carbonaceous matter, using a combination of radiocarbon technology, linear regression of organic carbon (OC) -K+ and elemental carbon (EC) tracer method. Fractional contributions of fossil fuels, biomass burning, biogenic secondary organic carbon (BSOC) and soil dust to the atmospheric size-resolved carbonaceous matters in Shanghai suburb were estimated using this new method. The fossil carbon contributed most of the OC in particles smaller than 0.49 μm, and its fraction decreased with the increase of particle size. Biomass burning contributed 17–28 % to the OC. The BSOC contributed comparable proportions to the OC in particles smaller than 3.0 μm with the biomass burning, but larger in the particles lager than 3.0 μm. The soil dust contributed least fraction to the OC of each size with a proportion of 2–13 %. The biomass burning and fossil sources shared comparable fraction of the EC in all size range. 相似文献
14.
Wittmann G Huybrechts T Van Langenhove H Dewulf J Nollet H 《Journal of chromatography. A》2003,993(1-2):71-78
An analytical method consisting of extraction, clean-up, and analysis by gas chromatography-electron-capture detection (GC-ECD) was developed for the determination of trichlorobenzenes (TCBs) in fish samples. Two extraction methods, saponification and liquid-liquid extraction (S-LLE), and microwave-assisted extraction (MAE), were evaluated. In both cases, n-pentane was used as the extraction solvent. For S-LLE, the recoveries ranged from 66.6+/-9.1% for 1-bromo-4-chlorobenzene (4-BCB) to 93.5+/-4.9% for 1,2,4-trichlorobenzene (1,2,4-TCB). The recoveries were significantly lower, between 31.0+/-3.9% for 1,2,3-trichlorobenzene (1,2,3-TCB) and 52.3+/-3.0% for 1,3,5-trichlorobenzene (1,3,5-TCB), in the absence of fish. Proteins and glycerides of the fish tissue seemed to compete with TCBs for the base, and hence decreased their decomposition rate. In the case of MAE, the recoveries were highly dependent on the pressure applied during extraction. At 5 bar, much higher recoveries were obtained, from 66.7+/-15.6% for 4-BCB to 79.9+/-13.6% for 1,2,4-TCB, than at 1 bar. Sulfur formation was, however, observed at 5 bar, and interfered with the GC-ECD analysis of TCBs. Sulfur was adequately removed by copper powder treatment, which was shown not to affect the recovery of analytes. The recoveries of target analytes by S-LLE and MAE did not differ statistically (t-test, alpha = 0.01). Both methods were appropriate for the detection of TCBs at concentration levels typically observed in marine biota, i.e. approximately 1 ng/g. S-LLE was, however, more time consuming, and required larger volumes of high-purity organic solvents than MAE. 相似文献
15.
Investigating sorption-driven dissolved organic matter fractionation by multidimensional fluorescence spectroscopy and PARAFAC 总被引:1,自引:0,他引:1
Banaitis MR Waldrip-Dail H Diehl MS Holmes BC Hunt JF Lynch RP Ohno T 《Journal of colloid and interface science》2006,304(1):271-276
Soil organic matter is involved in many ecosystem processes, such as nutrient supply, metal solubilization, and carbon sequestration. This study examined the ability of multidimensional fluorescence spectroscopy and parallel factor analysis (PARAFAC) to provide detailed chemical information on the preferential sorption of higher-molecular-weight components of natural organic matter onto mineral surfaces. Dissolved organic matter (DOM) from soil organic horizons and tree leaf tissues was obtained using water extracts. The suite of fluorescence spectra was modeled with PARAFAC and it was revealed that the DOM extracts contained five fluorescing components: tryptophan-like (peak location at excitation <255 nm:emission 342 nm), tyrosine-like (276 nm:312 nm), and three humic-substance-like components (<255 nm:456 nm, 309 nm:426 nm, <255 nm:401 nm). In general, adsorption onto goethite and gibbsite increased with increasing DOM molecular weight and humification. PARAFAC analysis of the pre- and post-sorption DOM indicated that the ordering of sorption extent was humic-like components (average 91% sorption) > tryptophan-like components (52% sorption) > tyrosine-like components (29% sorption). This differential sorption of the modeled DOM components in both the soil organic horizon and leaf tissue extracts led to the fractionation of DOM. The results of this study demonstrate that multidimensional fluorescence spectroscopy combined with PARAFAC can quantitatively describe the chemical fractionation process due to the interaction of DOM with mineral surfaces. 相似文献
16.
We assessed the accuracy and utility of a modified high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS) system for measuring the amount and stable carbon isotope signature of dissolved organic matter (DOM) <1 μm. Using a range of standard compounds as well as soil solutions sampled in the field, we compared the results of the HPLC/IRMS analysis with those from other methods for determining carbon and (13)C content. The conversion efficiency of the in-line wet oxidation of the HPLC/IRMS averaged 99.3% for a range of standard compounds. The agreement between HPLC/IRMS and other methods in the amount and isotopic signature of both standard compounds and soil water samples was excellent. For DOM concentrations below 10 mg C L(-1) (250 ng C total) pre-concentration or large volume injections are recommended in order to prevent background interferences. We were able to detect large differences in the (13)C signatures of soil solution DOM sampled in 10 cm depth of plots with either C3 or C4 vegetation and in two different parent materials. These measurements also demonstrated changes in the (13)C signature that demonstrate rapid loss of plant-derived C with depth. Overall the modified HLPC/IRMS system has the advantages of rapid sample preparation, small required sample volume and high sample throughput, while showing comparable performance with other methods for measuring the amount and isotopic signature of DOM. 相似文献
17.
A procedure is described for the determination of organic compounds in aerosols and rain from the remote marine atmosphere. Five classes of naturally occuring lipids (n-alkanes, was esters, fatty alcohols, sterols, and fatty acids) were quantified in the samples. Air samples (4000–10 000 m3) were collected on glass-fiber filters under authomatic control. Rain samples (1–5 l) were collected on an event basis. Filter and rain samples were extracted with dichloromethane and the extracts were fractionated into discrete chemical classes by adsorption chromatography with silica gel. The fractions were derivatized (if necessary) and quantified by high-resolution glass-capillary gas chromatography (HRGC) and HRGC/mass spectrometry. A second filter extraction was required for quantitation of fatty acid salts. On-column injection of the fractions provided identification and quantification of a wide range of homologs within each compound class: C15–C44 for n-alkanes, C36–C62 for was esters, and C13–C36 for fatty alcohols and fatty acids. Internal standards were used to quantify recoveries and concentratins. Mean recoveries relative to the internal standares were 96.5% for C15–C36 n-alkanes, 96.4% for C20–C30 n-fatty acids, 92.5% for C14–C30 n-fatty alcohols and 93.3% for cholesterol. The procedural blanks for the remote marine aerosol samples allow detection limits of 0.1–1.0 pg m?3 for most compounds. These values are lower than any other method used at coastal marine, rural or suburban sampling locations. 相似文献
18.
We describe a novel solution-based method for the determination of dissolved organic matter (DOM) relying on the formation of silver nanoparticles (AgNPs) via photo-stimulated reduction of silver ions by humic and fulvic acids. The method is based on natural driven formation of nanoscale materials yielding a direct relationship between DOM concentration and AgNPs formation. The aqueous dispersion of the formed AgNPs show strong and uniform UV–Vis absorption bands between 450 and 550 nm irrespectively of DOM nature and properties (i.e. humic or fulvic acids). The ensuing chromatic shift accompanying the appearance of the new absorption bands is easily conceivable by a simple spectrophotometer and the bare eye, holding great promise for the on-site, instrumental-free screening of DOM levels. Under the optimum experimental conditions the determination of DOM was successfully demonstrated to various water samples with high sensitivity (<1.0 mg L−1), satisfactory recoveries (87.5–123.5%) and reproducibility (5.87–6.73%). 相似文献
19.
Palma Orlović-Leko Kristijan Vidović Marta Plavšić Irena Ciglenečki Ivan Šimunić Tatiana Minkina 《Journal of Solid State Electrochemistry》2016,20(11):3097-3105
This study demonstrates the potential of the electrochemical methods for the characterization of dissolved organic matter (DOM) in the drainage water of hydroameliorated agricultural areas. A study of drainage water could lead to a better understanding of the distribution and fate of terrestrial DOM in the freshwater systems. We have applied the voltammetric techniques which were developed by our group for the characterization of organic matter in the natural waters in general. Studied samples were collected in the experimental amelioration fields in the Sava river valley (45° 33′ 52″ N/16° 31′ 33″ E, 100 m above sea level), in the hydroameliorated agricultural areas in Croatia. The rough characterization of the type, nature and reactivity of DOM was done through the study of surface activity (SA) of dissolved organic carbon (DOC), copper complexing capacity (CuCC) and apperent stability constants, and measurements of organic and inorganic reduced sulfur species (RSS) fractions. The results confirm that the electrochemical approach gives a valuable and comprehensive insight into physicochemical characteristics of DOM in the drainage water and could be successfully applied to temporal studies in different terrestrial ecosystem. 相似文献
20.
Vase KH Holm AH Norrman K Pedersen SU Daasbjerg K 《Langmuir : the ACS journal of surfaces and colloids》2007,23(7):3786-3793
The applicability and versatility of the recently communicated procedure for the grafting of conducting carbon substrates by diaryliodonium salts is expanded. We have found that several types of organic arylic layers can be formed on the carbon surface and that the chemical functionalities of the thus formed layers can be varied extensively over electron withdrawing (for example, -NO2) to electron donating (for example, -OMe) groups. A comparative study involving the grafting of aryldiazonium salts reveals that, despite the two approaches being similar, iodonium salts exhibit spontaneous grafting to a significantly lower extent. Nevertheless, the grafted layer becomes less accessible to proton transport as visualized from a greater reluctance toward the reduction of surface-confined nitro groups to amino groups in acidic medium. Employment of unsymmetrical iodonium salts opens up the interesting possibility of forming organic films consisting of a mixture of two different aryl groups. Alternatively, such composite layers may be prepared by selecting iodonium and diazonium salts with comparable reduction properties. Analysis of the surfaces is carried out by means of cyclic voltammetry, X-ray photoelectron spectroscopy, and ToF-SIMS (time-of-flight secondary-ion mass spectrometry). The ToF-SIMS analysis primarily serves to provide unambiguous evidence for the covalent attachment of the organic layers to the surface. 相似文献