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1.
海水中胶体有机碳的测定──高温燃烧法和紫外/过硫酸钾法的比较 总被引：5，自引：0，他引：5
利用切向超滤(cross-flow ultrafiltration)技术对海水中胶体有机碳(COC)和真溶解有机碳(UOC)进行了分离,并分别用高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳进行了测定。测定结果表明,切向超滤能定量分离海水中的胶体有机碳,高温燃烧法和紫外/过硫酸钾法对胶体有机碳和真溶解有机碳的测定结果没有明显的系统误差,表明这两种方法的氧化效率基本相同,胶体粒子的存在,对紫外/过硫酸钾法的氧化效率没有显着影响。 相似文献
2.
We describe an investigation into the reactivity of dissolved organic carbon (DOC), produced from marine algae, to conventional persulphate and ultraviolet (UV) oxidation methods. Marine algae were grown in batch culture in the presence of 14C bicarbonate and filtered samples of the phytoplankton dissolved organic carbon (PDOC) were oxidized with persulphate and UV techniques. The amount of fixed label found in solution after the oxidation procedures was compared with the initial amount of labelled DOC. Marine algae examined in this way included: the diatoms, Chaetoceros gracilis, Skeletonema costatum, Phaeodactylum tricornutum; the flagellate, Isochrysis galbana; and the cyanobacterium, Synechococcus strain DC2. It was found that 5–18% of the DOC produced by these phytoplankton resisted persulphate oxidation. Samples were also measured for their resistance to UV oxidation by an autoanalyzer method. It was found that 15–27% of these samples resisted UV oxidation. However, 95% of PDOC was oxidized after exposure for 6 h to high intensity UV irradiation using a variable exposure time system. P. tricornutum and Synechococcus PDOC samples were ultrafiltered into low molecular weight (< 10 000 Da) and colloidal (> 10 000 Da) size fractions. Both species produced mainly (> 68%) low molecular weight material. Slightly greater resistance to persulphate oxidation was generally found for the colloidal Synechococcus PDOC (15–22%) than for the low molecular weight material (14–17%). However, the opposite was found for the P. tricornutum PDOC which generally showed less resistance for the colloidal fraction (5–12%) than for the low molecular weight fraction (10–15%).Experiments were also conducted to determine the effects of short-term (days) and long-term (months) ageing of PDOC solutions in the presence of microbial populations from coastal seawater. Long-term ageing decreased the amount of PDOC that resisted oxidation in all cases. However, the fraction of PDOC resisting persulphate oxidation increased by small amounts over a short-term experiment. Increased resistance was attributed to preferential degradation of biologically and chemically labile components of PDOC by bacteria.The percentages of phytoplankton-produced (and microbially aged) DOC found in this study to resist UV or persulphate oxidation were low (5–27%), compared with those values (50–65%) reported for DOC in surface seawater on the basis of recent high temperature catalytic oxidation analyses. 相似文献
3.
Continuous flow analysis of dissolved total phosphorus in seawater by UV-K2S2O8 online digestion method 总被引：1，自引：0，他引：1
Several methods for analysis of dissolved total phosphorus in seawater were reviewed. Discussions were focused on UV irradiation and persulphate oxidation methods which are the most popular dissolved organic phosphorus determination methods presently. The compounds used for the phosphorus recovery test were categorized into three groups according to their chemical structure. It was found that low power UV irradiation can decompose P-O-C or P-C bonds efficiently but may be inefficient for P-O-P bonds. Heating-bath in acid condition is useful for decomposing P-O-P bonds. Using the continuous flow analysis system (Auto-analyzer Ⅱ), UV digestion and heating-bath, series experiments were carried out based on the above analysis. Eleven model compounds were employed for the phosphorus recovery test and the factors influencing the decomposition efficiency of dissolved compounds containing phosphorus were clarified. Finally, the optimal design for determination of dissolved total phosphorus in seawater based on the routine continuous flow analysis system was presented. For the organic mono-phosphate, the recovery is more than 90% and a recovery of 33%～51% was obtained for inorganic or organic polyphosphates. Up to now, this is the highest decomposition efficiency for dissolved phosphorus based on the continuous flow analysis system. 相似文献
4.
过硫酸盐氧化法测定海水中溶解总磷 总被引：6，自引：0，他引：6
实验研究在碱性和酸性条件下过二硫酸钾高温氧化四种不同类型含磷标准化合物在海水中的回收率和影响回收率的因素。结果表明 :在碱性条件下过二硫酸钾高温氧化可使海水中非聚磷类化合物完全回收 ,而聚磷类化合物回收率不高 ,延长消化时间聚磷类化合物的回收率有一定提高。除个别化合物外 ,各类含磷化合物在酸性条件下可被定量回收。依此 ,建立酸性过硫酸盐氧化法分解测定海水中溶解态总磷的方法。 相似文献
5.
海水中总氮和总磷的同时测定 总被引：24，自引：0，他引：24
早期总氮和总磷的过硫酸钾法氧化分析分别是在碱性和酸性介质中进行［１,２］,样品分别保存,然后分别氧化测定,工作较繁琐。１９７７年Ｋｏｒｏｌｅｆｆ用过硫酸钾氧化法同时氧化水体中的总氮和总磷,使样品的保存和氧化分析工作简化。１９８１年Ｖａｌｄｅｒｒａｍａ对该方法测定天然海水中的总氮和总磷做了进一步研究,总氮和总磷同时氧化后,水样中的硝酸盐和磷酸盐用手工分别进行分析。Ｗａｌｓｈ１９８９年和Ｋａｒｌ等１９９３年曾采用ＵＶ光氧化法对海水中总溶解氮和总溶解磷进行同时氧化后,用自动分析对氧化后的无机氮和磷进行… 相似文献
6.
Patrick Raimbault Wilfried Pouvesle Frdric Diaz Nicole Garcia Richard Sempr 《Marine Chemistry》1999,66(3-4)
We developed a simple and reliable method which allows simultaneous determination of organic forms of carbon (DOC), nitrogen (DON) and phosphorus (DOP) dissolved in seawater. Conversion of dissolved organic matter (DOM) to inorganic products (carbon dioxide, nitrate+nitrite and soluble reactive phosphate) is performed by a persulfate wet-oxidation in low alkaline condition. After oxidation, the concentration of the inorganic products dissolved in the sample was measured automatically by colorimetry using a 3-channel Technicon AutoAnalyzer system. A number of pure organic compounds were tested in the concentration range encountered in coastal and open ocean, indicating a high efficiency of the digestion procedure. The recovery range is similar to that obtained by other wet-oxidation procedures and by high-temperature catalytic oxidation techniques. Direct comparisons with usual methods used for separate determination of DOC, DON and DOP indicated a high efficiency of the procedure. Reproducibility tests demonstrated a very good precision (around 5%) for lagoonal and coastal waters, while precision was sometimes around 10–25% in oligotrophic oceanic waters, especially for DOP where values approached limits of detection for measuring phosphate. This method is highly suitable for routine analysis and especially appropriate for shipboard work. 相似文献
7.
A detailed examination of a high-temperature catalytic oxidation method for liquid samples in the analysis of total nitrogen dissolved in seawater is reported. The nitrogenous compounds in liquid samples are oxidized on a platinum catalyzer at 680°C under oxygen atmosphere and the generated NO2 is absorbed into a chromogenic reagent, followed by a spectrophotometric determination. The results of this method are much higher than those of wet oxidation methods. Molecular size dependency of the results clearly indicates that the above discrepancy is caused by the low oxidation capacity of the wet oxidation method against high-polymer organic matter dissolved in seawater. The results revealed that the concentration of total nitrogen in seawater is nearly constant from surface to bottom, ranging from 30 to 40 μM 1?1, which organic nitrogen concentration higher in the surface layer, and a rapid decrease with depth. An examination of molecular size distribution indicates that the concentration of high-polymer organic nitrogen decreases rapidly from surface to deeper layers, with molecular sizes ranging from 5 × 103 to 3 × 104. Because of the well-defined principle of the oxidation process, its reliability, ease of sample handling and of analytical procedure on board or in the land laboratory, the present method is much more suitable for the marine analytical chemistry of total and organic nitrogen than the other previous methods. 相似文献
8.
Absorption and fluorescence of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) measurements were performed during three oceanographic surveys in 1994 in the southern Baltic Sea (Polish area of the Baltic Proper). DOC was measured both by high-temperature catalytic oxidation (HTCO) and low-temperature oxidation (LTO) conventional persulphate methods. CDOM fluorescence was shown to be highly correlated with absorption, with the same regression parameters, despite the seasonal change in different hydrographic conditions and the fluorescence quantum yield variations (1.23 ± 0.07 in April and 0.97 ± 0.12 in September). The results show a good correlation between the optical parameters and DOC although ˜ 70% of the DOC does not display significant absorption in the UV-visible range (350–750 nm). The non-absorbing DOC measured with HTCO method appears unaffected by seasonal changes. Consequently, total DOC can be predicted by optical methods using remote sensing techniques. The non-absorbing DOC measured by LTO method varies from 62% (April) to 76% (September), which implies that there is requirement for estimates on a seasonal basis. 相似文献
9.
M.D. MacKinnon 《Marine Chemistry》1978,7(1):17-37
A high-temperature oxidation method is described for the accurate and precise determination of the total organic carbon (TOC) in seawater. Problems of contamination in sample storage, preparation, and oxidation which are evident in previous dry oxidation methods have been controlled. The TOC results from different areas are determined and compared directly with the results obtained on duplicate samples with the persulfate oxidation method. Significantly higher TOC values (15–20%) are obtained with the dry oxidation procedure, but the relative difference in the methods is relatively constant over depth and geographic areas. A high correlation between the methods was obtained. For accurate results, the dry method is recommended but conclusions based on profiles of TOC determined by either method should be similar if the proper precautions in analysis are followed. 相似文献
10.
海水中溶解有机碳（DOC）的测定 总被引：18，自引：0，他引：18
本文论述了海水中溶解有机碳(DOC)的测定方法,对DOC的测定原理及氧化方法进行了讨论,并提出了妨碍海水中DOC测定准确度提高的因素,这对于建立高准确度和精密度的新分析方法具有重要的意义。 相似文献
11.
An improved method for the bulk characterization of particulate and dissolved combined carbohydrates in seawater is presented. Seawater samples are dried under vacuum and the residue is hydrolyzed with 12 M H2SO4. Carbohydrates in the hydrolysate are subsequently quantified spectrophotometrically by MBTH (3-methyl-2-benzothiazolinone hydrazone hydrochloride) analysis. Sulfuric acid was more effective in hydrolyzing high-molecular-weight structural carbohydrates (cellulose, chitin, and alginic acid) than weak (0.09 N) hydrochloric acid. Sulfuric acid hydrolysis of dissolved and particulate samples yielded estimates of carbohydrates equal to or greater (two- to four-fold) than those resulting from dilute (0.09 N) HCl hydrolysis. In samples from the Gulf of Mexico, total dissolved carbohydrates determined after sulfuric acid hydrolysis varied from 20 to 56 μM C and from 10 to 28% of the dissolved organic carbon determined by high-temperature catalytic oxidation. 相似文献
12.
M.D. MacKinnon 《Marine Chemistry》1979,8(2):143-162
A method based on a dynamic head-space extraction and high-temperature oxidation of the trapped organic matter is described for the determination of the volatile organic carbon (VOC) concentration in seawater. The VOC concentrations in various geographic regions have been measured and calculated as a fraction of the total organic carbon (VOC/TOC). The VOC concentrations ranged from 15–60 μg C/liter in most oceanic areas. This volatile component was found to be a small fraction (1.5–6%) of the TOC. The VOC concentrations are highest in coastal regions and in the surface zone while the VOC/TOC ratio is relatively constant with depth and location. The volatile organic components may be important to the cycling of organic matter in sea water and the dynamics of this role have been postulated. 相似文献
13.
Dimethylsulfide(DMS) is generally thought to be lost from the surface oceans by evasion into the atmosphere as well as consumption by microbe.However,photochemical process might be important in the removal of DMS in the oceanic photic zone.A kinetic investigation into the photochemical oxidation of DMS in seawater was performed.The photo-oxidation rates of DMS were influenced by various factors including the medium,dissolved oxygen,photosensitizers,and heavy metal ions.The photo-oxidation rates of DMS were higher in seawater than in distilled water,presumably due to the effect of salinity existing in seawater.Three usual photosensitizers(humic acid,fulvic acid and anthroquinone),especially in the presence of oxygen,were able to enhance the photo-oxidation rate of DMS,with the fastest rate observed with anthroquinone.Photo-oxidation of DMS followed first order reaction kinetics with the rate constant ranging from 2.5×10-5 to 34.3×10-5 s-1.Quantitative analysis showed that approximately 32% of the photochemically removed DMS was converted to dimethylsulfoxide.One of the important findings was that the presence of Hg2 could markedly accelerate the photo-oxidation rate of DMS in seawater.The mechanism of mercuric catalysis for DMS photolysis was suggested according to the way of CTTM(charge transfer to metal) of DMS-Hg2 complex. 相似文献
14.
Jonathan H. Sharp 《Marine Chemistry》1973,1(3):211-229
A method is described for the determination of organic carbon in liquid seawater samples by combustion at a high temperature. Although the method is not easy to perform, it has been successfully employed for a direct comparison to the standard method of persulfate oxidation. With seawater from the central western North Atlantic Ocean, the standard method measured an average of 78% as much carbon as the high temperature method. This indicates organic matter in seawater that is resistant to oxidation by persulfate; some of it appears to be of a colloidal nature. The persulfate resistant organic matter is most noticeable in a region below the surface 100 m and seems to decrease slowly with depth, indicating deep ocean biological utilization of organic matter. Due to a possible procedural error in the standard persulfate oxidation method, the differences indicated here may actually be conservative and the content of total organic carbon in the sea may be as much as twice as high as has been indicated by previous estimates. 相似文献
15.
16.
Appropriate conditions have been achieved for the accurate, rapid, and highly precise shipboard simultaneous determination of dissolved organic carbon and total dissolved nitrogen in seawater by high temperature catalytic oxidation. A nitrogen-specific Antek 705D chemiluminescence detector and a CO2-specific LiCor Li6252 IRGA have been coupled in-series with a Shimadzu TOC-5000 organic carbon analyser. Precision of both simultaneous measurements is ≤1.5%, i.e. ±1 μmol C l−1 and ±0.3 μmol N l−1, respectively. Quality of analysis is not compromised by vibrations associated with ocean going research vessels. 相似文献
17.
Aerated solutions of potassium iodide in de-ionised water, of between 5–20% (w/v), were exposed to ambient spring sunlight to estimate the rate of photochemical production of molecular iodine from iodide and oxygen in seawater. This rate cannot be measured directly as other reactions, for example the reduction of molecular iodine by organic matter, interfere. Also, a parallel photo-oxidation, initiated by organic matter in real seawater, may also occur. The experiments yield a half-life for iodide in tropical surface waters of about 29 months suggesting that the reaction is insignificant. At this rate it will not compete effectively against the reduction of molecular iodine by organic matter, and hence molecular iodine should not appear. The experiments also consider the photo-oxidation by nitrate, and iodate, a combination of nitrite and oxygen, and eliminate significant interference by chloride, bromide and the phosphate buffer. The rate of photo-oxidation with each of the first three oxidations is found to be first order with respect to oxidant concentration. The variation of photo-oxidation rate with pH is also studied, with a brief investigation without conventional oxidant, where electron cage complexes still promote photo-oxidation. The photochemical action spectrum for these reactions in sunlight is shown to extend between 300 and 425 nm. The photo-oxidation of iodide by iodate is more interesting to marine chemistry as the photo-reduction of iodate. Nevertheless, the reduction-rate is judged to be several orders too low to be significant in seawater. The mechanism of the reactions are discussed and lessons drawn on the stability of potassium iodide solutions used in iodate analysis. The KI actinometer is recommended to those studying other photochemical systems activated by UV-A light as it is linear and very simple and reliable. 相似文献
18.
A new dry combustion method for the simultaneous determination of total organic carbon and nitrogen in seawater is presented. Concentrations of total organic carbon obtained using this method average about 2.0 mg/l in surface water and 1.5 mg/l in deep water in the Northwest Atlantic. These concentrations are significantly greater than those reported using wet oxidation and wet combustion methods, but are comparable to concentrations reported by Russian workers using a similar dry combustion method. Organic nitrogen concentrations average 0.44 mg/l in surface water and 0.12 mg/l in deep water, yielding CN ratios for total organic matter of 5 and 12 respectively. 相似文献
19.
Several homologous monoalkylated benzenes were photo-oxidized as surface films on and dissolved in pure water and purified natural seawater by solar and equivalent artificial UV irradiation in the presence of anthraquinone as photo-sensitizer. The main reaction products were the 1-phenylalkanones, the corresponding secondary alcohols, benzaldehyde and, when the side chain contained four or more carbon atoms, the products of what appears to be a Norrish type II photo-degradation. The detection among the reaction products of an aldehyde with one carbon atom less than the olefin produced by the Norrish type II photo-degradation suggests a photolytic decomposition of 1-alkenes, resulting in the formation of highly reactive compounds capable of abiotic reactions in the electronic ground state with a variety of organic compounds occurring in seawater. 相似文献
20.
This study examines the mechanism of oxidation of dissolved organic matter (DOM) in a high-temperature combustion (HTC) carbon analyzer. The HTC analyzer, which is commonly used to measure the concentration of dissolved organic carbon (DOC) in seawater, is still largely empirical in its operation, and little information is yet available on the chemical and physical mechanisms responsible for oxidation of DOM. To examine the role of water, which has been hypothesized to be a source of reactive oxidants in HTC analyzers, several experiments were conducted using gaseous hexane samples and several wet/dry carrier gases. Because the quantity of O2(g) needed to oxidize an injected sample of DOM is quite small, a substantial effort has been made to exclude O2(g) from the combustion furnace of the HTC instrument. In this modified, “air-tight” instrument, the efficiency of conversion of hexane into CO2 was greatest in dry O2 and slightly lower in moist O2. Hexane was only slightly oxidized in dry N2, but it was largely converted into CO2 when moist N2 was used as the carrier gas. These experiments confirm that water provides reactive oxidizing species (perhaps hydroxyl radical) that rapidly convert hexane into CO2 in the combustion tube of a carbon analyzer. Additional experiments with aqueous solutions of potassium hydrogen phthalate and a variety of carrier gases support this basic hypothesis. 相似文献