首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
阎雪姣  王江涛 《海洋科学》2012,36(5):103-108
对测量海水中总溶解氮(TDN)的两种常用方法——高温燃烧法和过硫酸钾氧化法进行了比较。结果表明,两种方法在空白、精密度和准确度实验中不存在显著差异。对不同化合物的回收率均在92%～107%之间,加标回收实验回归曲线的斜率分别为0.93和0.92。对于现场海水样品的测定结果,两个断面拟合的斜率分别为0.92和0.97。HTC法比PO法对实际海水样品的氧化效率略高,在操作上也更方便、快捷。因此,高温燃烧法更适合海水中总溶解氮(TDN)的测定。  相似文献   

2.
A broad community intercalibration exercise for accurate measurement of dissolved organic carbon (DOC) in seawater has been carried out over a period of 5 years. A set of 10 natural samples with DOC content from 40 to 200 μM C were accompanied by two glucose standards and a “zero C” blank; all sealed in glass ampoules. Samples were sent to all interested analysts for “blind” analysis; 62 laboratories in 17 countries participated. A total of 59 separate analyses were determined to be acceptable by screening criteria based on standards and blank; another nine sets of analyses did not pass the screening. The majority of the analyses, both those passing and those that did not, were performed with high temperature combustion (HTC) methods, six sets of analyses were done using wet chemical oxidation methods.From the 53 sets of acceptable HTC analyses, the coefficient of variation (%CV) for analytical comparability of the samples was 10% (“community precision”). It is estimated that the individual replicate injection precision for most instruments was approximately 2% and that no additional variability was caused by differences within the ampoules of individual samples. The additional variability over 2% was likely a result of both random and systematic differences in analytical capabilities from instrument to instrument and from day to day for individual instruments. With an arbitrary selection after the fact, smaller subsets of analysts can show comparability better than 10% and duplicate or triplicate runs on different days of the full sets of samples in several laboratories showed comparability in the 2–6.5% range. Experienced oceanic analysts, with internal or shared reference materials, can now show reproducibility and comparability at a level closer to 2%.Preliminary use of DOC reference materials by 14 participants showed day-to-day reproducibilities for their laboratories in the 2–6% range in most cases; several with poorer reproducibility do not normally perform DOC analyses on samples with concentrations as low as the deep ocean reference used here. Use of these reference materials can also give a demonstration of comparability between laboratories. For credibility of DOC analyses, it is necessary for analysts to use community reference materials and report results of their analytical performance with these references.This paper does not identify individual data nor should it be considered an evaluation of individual laboratories or analysts. The purpose is to show the summary picture of the international community of DOC analysts as it existed in the mid- to late 1990s.  相似文献   

3.
Nitrogen loadings to coastal waters have increased over the last century, resulting in deterioration in water quality. In this study we investigated the distributions and seasonality of dissolved organic nitrogen (DON), and its relationship to total dissolved nitrogen (TDN), for two anthropogenically influenced estuarine systems in southwest England. Concentrations of DON in both estuaries were generally < 80 μM. DON showed non-conservative distributions, resulting from external and internal inputs and in situ reactivity. DON contributed 38 ± 22% (range 4–79%, Yealm) and 36 ± 17% (range 4–84%, Plym) to the TDN pool, with lower values generally observed in the fresher samples relative to the more saline samples. DON was a larger fraction of the TDN pool during the summer and autumn relative to winter and spring, indicating the influence of bacterioplankton release on nitrogen cycling in the estuaries. Ammonification and nitrification were observed in the estuaries, processes which were reproduced in incubation experiments using bioreactors. The bioreactor experiments showed that 12% h− 1 of the DON flux from the River Plym may be available to bacteria, indicating significant removal of DON during the residence time of the water in the estuary (a few days). The bioavailable nature of the DON means that this N fraction significantly adds to the eutrophication burden of the receiving coastal waters, and therefore cannot be ignored in environmental assessments.  相似文献   

4.
Dissolved organic nitrogen (DON), dissolved organic carbon (DOC) and inorganic nutrient concentrations were determined in samples from an area encompassing the Northeast Water Polynya from June to August 1993. In June, still ice-covered polynya area surface waters (PySW) had significantly higher (p<0.05) DOC concentrations (110 μM, n=68) than surface water outside the polynya area (96 μM, n=6). Melting ice and ice algae are suggested as DOC sources. DOC concentrations found in this study are consistent with other studies showing higher DOC concentrations in the Arctic than in other ocean areas. As the productive season progressed, DOC concentrations in Polynya surface water (PySW) decreased (p<0.05) from 110 to 105 μM, while DON concentrations increased (p<0.05) from 5.6 to 6.1 μM, causing a significant decrease (p<0.05) in the C : N ratios of DOM from spring (C : N ratio 20) to summer (C : N ratio 17). We found a significant (p<0.05) decrease in the DOM C : N ratio in all water masses within the polynya area as the productive season progressed. DON was the largest fraction of total dissolved nitrogen (TDN) in PySW and surface waters outside the polynya area. TDN was calculated as the sum of DON, nitrate, nitrite and ammonium concentrations. DON increased (p<0.05) from 62% to 73% of TDN in PySW from spring to summer, a result of increasing DON concentrations and decreasing inorganic nitrogen concentrations over the productive season. The seasonal accumulation of DON and the corresponding decrease in nitrate concentrations in waters with primary production indicate that it is important to take the DON pool into account when estimating export production from nitrate concentration decreases in surface waters. PySW TDN concentrations decreased (p<0.05) from 9.1 (n=61) to 8.6 μM (n=60) from spring (May 25 through June 19) to summer (July 1 through July 27). The seasonal decrease in surface water TDN concentrations corresponded to increases in TDN concentrations in deeper water masses within the Polynya. Most of the TDN increase in deep water was in the form of DON. A possible explanation is that PON was dissolved (partially remineralized) in the water column at mid depths, causing increases in the DON concentration. Transfer of N from PySW (with a short residence time in the polynya area) to Polynya Intermediate Water and deep waters of the Norske and Westwind Trough with multi-year residence times keeps N from leaving the polynya area. In spring, nutrients from degradation of OM in PyIW could support primary production. The role of PyIW as an OM trap could be important in supporting primary production in the polynya area.  相似文献   

5.
IrocrIowThere is a linkage in shallow marine systerns between sea-noor biOgaxhemical pmeessesand water column pnductivity (Bereson et al., l998). Benthic fluxes provide a significantsource of nutrients to the overlying water tO supPOrt primary pnduction and play a role in de-.creasing oxygen concentrations (van et al., l999; Cowan and Boynton, l996; Berelson etal., 1998; Friedl et al., l998; Zabel et al., l998). TherefOre, it is imPOrtant to define theediment di8genetic pathways for the …  相似文献   

6.
细菌对海水中各形态氮的影响   总被引：1，自引：0，他引：1  
海洋细菌生长过程中,不但能利用体系中的有机物质,而且也能利用无机营养盐。本论文通过小麦岛细菌接种实验发现,细菌大量繁殖时吸收利用体系中的营养物质,生成颗粒态氮(PN)和溶解有机氮(DON),体系中溶解无机氮(DIN)、总溶解氮(TDN)降低至最低值。进入细菌指数生长期和稳定期后,颗粒态和有机态氮不断降解向体系中释放出无机营养盐,DIN和TDN呈现回升趋势,颗粒氮(PN)与细菌数量变化正相关。体系中,初始氮源的量决定了细菌体内POC/PN的比值,氮源充足,细菌繁殖数量多,POC/PN值低,氮源不足,细菌数量相对较少,POC/PN比值高。  相似文献   

7.
A nitrogen and phosphorus dynamic model of mesocosm pelagic ecosystem was established according to the summary and synthesis of the models available, in which seven state variables （DIN, PO4-P, DON, DOP, phytoplankton, zooplankton and detritus） were included. Logically it had five modules--phytoplankton, zooplankton, dissolved inorganic nutrients, dissolved organic nutrients and detritus. The results showed that this model could simulate the variations of DIN, PO4-P, DON, DOP, POC and phytoplankton biomass in pelagic ecosystem in mesocosm properly, based on the site experiment data in the Jiaozhou Bay in the autumn of 1999 and the summer of 2000. Not only the logical structure but also the model parameters were feasible, and about 20 parameters were made to fit for the Jiaozhou Bay during the simulation. All of these are necessary to study the control mechanism of nutrients biogeochemical cycling in the Jiaozhou Bay and other China＇ s coastal waters.  相似文献   

8.
Dissolved organic nitrogen (DON) dynamics in the North Sea was explored by means of long-term time series of nitrogen parameters from the Dutch national monitoring program. Generally, the data quality was good with little missing data points. Different imputation methods were used to verify the robustness of the patterns against these missing data. No long-term trends in DON concentrations were found over the sampling period (1995–2005). Inter-annual variability in the different time series showed both common and station-specific behavior. The stations could be divided into two regions, based on absolute concentrations and the dominant times scales of variability. Average DON concentrations were 11 μmol l−1 in the coastal region and 5 μmol l−1 in the open sea. Organic fractions of total dissolved nitrogen (TDN) averaged 38 and 71% in the coastal zone and open sea, respectively, but increased over time due to decreasing dissolved inorganic nitrogen (DIN) concentrations. In both regions intra-annual variability dominated over inter-annual variability, but DON variation in the open sea was markedly shifted towards shorter time scales relative to coastal stations. In the coastal zone a consistent seasonal DON cycle existed with high values in spring–summer and low values in autumn–winter. In the open sea seasonality was weak. A marked shift in the seasonality was found at the Dogger Bank, with DON accumulation towards summer and low values in winter prior to 1999, and accumulation in spring and decline throughout summer after 1999. This study clearly shows that DON is a dynamic actor in the North Sea and should be monitored systematically to enable us to understand fully the functioning of this ecosystem.  相似文献   

9.
Heterotrophic mineralization of dissolved organic nitrogen (DON) can be a major source of N for primary producers. During the summer growing season in mesooligotrophic Castle Lake, dissolved inorganic nitrogen (DIN) is often below detection (<0.1 μg-atom N l−1) whereas DON can vary between 7 and 17 μg-atom N. The heterotrophic metabolism of glutamate resulted in the recycling of both carbon and nitrogen, but not at the same rate. The uptake of 15N- and 14C-labeled glutamate showed that C was preferentially assimilated relative to N resulting in an N-mineralization rate of 2.5–3.0 ng-atom N l−1 h−1. This suggests that heterotrophs in Castle Lake are not N-deficient, and metabolism of organic compounds results in the release of DIN which is available for primary production.  相似文献   

10.
On the basis of mass balance calculations performed for nitrogen (N) uptake experiments in the Southern California Bight (SCB), it has been suggested that a significant portion of dissolved inorganic N (DIN) uptake results in the production of dissolved organic N (DON). To investigate this process, the fate of ammonium (NH4+) and nitrate (NO3−) uptake was quantified within the euphotic zone at three coastal stations in the SCB using 15N tracer techniques. Several trends in the fate of DIN and the production of DON were observed. First, production of particulate N (PN), from both NH4+ and NO3−, was quantitatively more important in near surface waters, while DON release dominated within the nitracline. Second, the percentage of gross N uptake released as DON was generally higher when NO3−, rather than NH4+, was the substrate. Third, the percentage of N released as DON was higher at night, relative to the day. Fourth, rates of DON release were significantly correlated to NH4+ regeneration, suggesting that similar mechanisms are responsible for both processes—presumably grazing. The results of this study indicate that the DON pool is a sink for DIN uptake on the time scale of hours. One implication of this finding is that new production estimates based on 15NO3− uptake rates will likely underestimate particle flux out of the surface layer because the rate of NO3− uptake is underestimated due to loss of DO15N during the incubation. On time scales of months to years, however, the N that is taken up as NO3− and released as DON will likely contribute to export flux via incorporation of the dissolved phase during seasonal mixing into sinking particles or transport. The export of DON on these time scales argues for the use of gross uptake rates to calculate f-ratios.  相似文献   

11.
The concentration and distribution of dissolved nitrogenous compounds was studied in the Greenland Sea in June 1991. Dissolved organic (DON) and inorganic nitrogen (DIN) were determined in seawater of different origin and depth. Dissolved organic matter was isolated on XAD-2 resin and fractionated into its non-humic hydrophilic (H1), and so-called humic components (hydrophobic acid, HbA, and hydrophobic neutral, HbN). From all fractions the DON content was subsequently determined. Total DON concentrations were about 5 μmol Ni−1 in the surface and 3 μmol NI−1 below depths of 150–200 m. DIN varied between 1.5 and 1.6 μmol NI−1. There was a highly significant inverse correlation (r = −0.75) between DON and DIN suggesting a close coupling in the uptake and release of the different forms of nitrogen. The mean DON concentrations of the XAD-fractions were for HI = 2.3 μmol Ni−1, for HbA = 0.8 μmol NI− and for HbN = 1.0 μmol NI−1. The average percentage contributions were, respectively, 56%, 19% and 25%. This means that about 56% of the total DON does not belong to the ‘humic fraction’. The HbN fraction was evenly distributed in the water column, without any obvious relationship with water masses, depth, or nutrient status. In contrast, the HbA fraction showed a significant correlation with total DON.  相似文献   

12.
The stable isotopes of dissolved organic carbon (DOC) are a powerful tool for distinguishing sources and inputs of organic matter in aquatic systems. While several methods exist to perform these analyses, no labs routinely utilize a high temperature combustion (HTC) instrument. Advantages of HTC instruments include rapid analysis, small sample volumes and minimal sample preparation, making them the favored devices for most routine oceanic DOC concentration measurements. We developed a stable carbon DOC method based around an HTC system. This method has the benefit of a simple setup, requiring neither vacuum nor high pressures. The main drawback of the method is a significant blank, requiring careful accounting of all blank sources for accurate isotopic and concentration values. We present here a series of experiments to determine the magnitude, source and isotopic composition of the HTC blank. Over time, the blank is very stable at  20 ng of carbon with a δ13C of − 18.1‰ vs. VPDB. The similarity of the isotopic composition of the blank and seawater samples makes corrections relatively minor. The precision of the method was determined by oxidizing organic standards with a wide isotopic and concentration range (− 9‰ to − 39‰; 18 μM to 124 μM). Analysis of seawater samples demonstrates the accuracy for low concentration, high salinity samples. The overall error on the measurement is approximately ± 0.8‰.  相似文献   

13.
We observed the origin, behavior, and flux of dissolved organic carbon (DOC), dissolved organic nitrogen (DON), colored dissolved organic matter (CDOM), and dissolved inorganic nitrogen (DIN) in the subterranean estuary of a volcanic island, Jeju, Korea. The sampling of surface seawater and coastal groundwater was conducted in Hwasun Bay, Jeju, in three sampling campaigns (October 2010, January 2011, and June 2011). We observed conservative mixing of these components in this subterranean environment for a salinity range from 0 to 32. The fresh groundwater was characterized by relatively high DON, DIN, and CDOM, while the marine groundwater showed relatively high DOC. The DON and DIN fluxes through submarine groundwater discharge (SGD) in the groundwater of Hwasun Bay were estimated to be 1.3 × 105 and 2.9 × 105 mol d− 1, respectively. In the seawater of Hwasun Bay, the groundwater-origin DON was almost conservative while about 91% of the groundwater-origin DIN was removed perhaps due to biological production. The DON flux from the entire Jeju was estimated to be 7.9 × 108 mol yr− 1, which is comparable to some of the world's large rivers. Thus, our study highlights that DON flux through SGD is potentially important for delivery of organic nitrogen to further offshore while DIN is readily utilized by marine plankton in near-shore waters under N-limited conditions.  相似文献   

14.
高温燃烧法测定海水中的溶解有机碳   总被引：5，自引：2，他引：3  
１９９７年５月在莱州湾,１９９７年７月在东海,１９９７年１１月在胶州湾采集了海水样品,高温燃烧法测定了这些水样中的溶解有机碳浓度,了系统空白和标准曲线的选择对高温燃烧法测定结果的影响,并与紫外／硫酸钾法的测定进行了比较。  相似文献   

15.
厦门潘涂虾池及其附近内湾各态氮的季节性变化特征   总被引：9，自引：0，他引：9  
1996年6月至1997年2月，对厦门市潘涂垦区两口虾池及附近内湾不同形态氮的含量与动态进行调查。结果显示虾池的可溶性有机氮（DON）含量明显高于邻近内湾，颗粒有机氮（PN）多数时间也高于内湾，而邻近内湾可溶性无机氮（DIN）含量则明显比池内的高。虾池中的氮主要以DON形态存在（59．76％），DIN，PN含量较少（9．37％和20．87％）；邻近内湾则是以DIN为主（59．97％），其次为DON（29．55％），PN所占比例最小（10．48％）。吓池与邻近内湾不同形态氮的季节变化也存在一定差异。  相似文献   

16.
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   

17.
Detailed vertical profiles of dissolved organic carbon (DOC), nitrogen (DON) and DOC/DON ratios in the Australian sector of the Southern Ocean (56°–65°S around 140°W transect) were obtained by a high-temperature catalytic oxidation method with a modified Shimadzu TOC-5000 unit. The simultaneous analyses of DOC and total dissolved nitrogen (TDN) gave high precision results (±0.7 μMC and ±0.3 μMN). In surface layers, DOC concentrations were lower (45–55 μM) than those generally obtained from other oceanic environments (60–90 μM). The surface concentrations of DON varied from 4 to 9 μM, but within the range generally reported for other ocean regions. Surface excesses of DOC and DON were calculated against nearly constant subsurface concentrations. A consistent contribution of low C/N ratio (2.7–5.0) was found in the mid-surface layer (30–75 m), suggesting more extensive degradation of carbon-enriched materials and/or enhanced supply of nitrogen-enriched ones.  相似文献   

18.
The rapidly expanding industry of marine cage fish farming of sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) in the Mediterranean Sea over the last decade has often had damaging effects on the benthic aquatic environment near the fish farm installations. It has been observed that the food-remains, together with the pellets and metabolic products from fish, frequently form a “nepheloid” sediment layer covering large areas of the seabed. Under these conditions anoxia and/or hypoxia develop and affect benthic communities while the quality of the marine environment deteriorates for long periods, extending even beyond the life span of the fish farm itself. In most cases the affected areas act initially as sediment traps and in a second phase as secondary sources of organic carbon, nutrients and other substances.The aim of this paper is to explore the behaviour of such an affected area under different redox regimes by measuring the fluxes of ammonium, nitrite, nitrate, TDN, phosphate, TDP and silicate between the surface sediment and the overlying waters. To achieve this goal we constructed a prototype benthic chamber capable of sampling considerable quantities of affected undisturbed sediment along with its overlying water. The chamber was transported to the laboratory where simulation experiments reproducing the conditions occurring in nature, including the extreme ones, were carried out and studied carefully. The chamber allows the full and fine control of the dissolved oxygen concentration – and thus of the redox potential – as well as water temperature while subsamples of both water and sediment could be obtained and analysed for a series of chemical substances. The controlled laboratory chamber experiments reproduced four successional phases: 1) deoxygenation, 2) hypoxia, 3) reoxygenation and 4) anoxia.The results showed that even minor changes in the redox conditions at a relatively narrow zone near the water sediment interface have significant impacts on the concentrations of dissolved nitrogen, phosphorus and silicate compounds.With decreasing oxygen supply (phases 1, 2 and 4), the concentrations of ammonium, nitrite, TDN, phosphate, TDP and silicate rapidly increase, those of nitrate decrease. DON and DOP exhibit remarkable fluctuations.During reoxygenation (phase 3) the concentrations of ammonium stabilise, the nitrate concentration decreases while nitrite shows an increasing trend. Decreases in phosphate and silicate concentrations were also observed paralleled by TDP stabilization and DOP increasing trend. TDN shows a relatively small increase while the DON concentration fluctuates significantly.  相似文献   

19.
The aim of this study was to investigate the cycling of dissolved inorganic and organic nutrients using moored instrumented buoys (SmartBuoys) during the spring bloom in the North Sea. The instrumentation on the buoys enabled high frequency measurements of water-column integrated irradiance and in situ chlorophyll to be made, and also preserved water sample collection which were used for dissolved inorganic and organic nutrient analyses. The SmartBuoys were located in the year-round well-mixed plume zone associated with the River Thames and in the summer stratified central North Sea. These site locations allowed comparison of nutrient concentrations and cycling, and spring bloom development at two contrasting sites. The spring bloom was expected to be initiated at both stations due to increasing insolation and decreasing suspended load leading to higher water-column integrated irradiance. Due to differences in suspended load between the sites, the spring bloom started ∼2 months earlier in the central North Sea. The spring bloom in the Thames plume also resulted in higher maximum phytoplankton biomass due to the higher pre-bloom nutrient concentrations associated with riverine input. The use of SmartBuoys is also shown to allow the cycling of dissolved organic nutrients to be examined over the critical, and often undersampled, spring bloom period. Dissolved Organic Nitrogen (DON) clearly increased during the spring bloom in the central North Sea compared to winter concentrations. DON also increased in the Thames plume although showing greater winter variability related to higher riverine and sedimentary dissolved organic matter input at this shallow (∼18 m) coastal site. DON increase during the spring bloom was therefore related to primary production at both sites probably due to active release by phytoplankton. At both stations DON decreased to pre-bloom concentrations as the bloom declined suggesting the released DON was bioavailable and removed due to heterotrophic uptake and production. The preserved nutrient samples from the central North Sea site were also suitable for Dissolved Organic Phosphorus (DOP) analysis due to their low suspended load with similar trends and cycling to DON, albeit at lower concentrations. This suggested similar processes controlling both DON and DOP. The variable timing of short term events such as the spring bloom makes sampling away from coastal regions difficult without the use of autonomous technology. This study demonstrates for the first time the applicability of using preserved samples from automated buoys for the measurement of dissolved organic nutrients.  相似文献   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号