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1.
The absorption coefficient of chromophoric dissolved organic matter (aCDOM) has been found to be correlated with fluorescence emission (excitation at 355 nm). In the coastal European Atlantic area and in the Western Mediterranean Sea (Gulf of Lions), a significant statistical dependence has been found between aCDOM and fluorescence with dissolved organic carbon (DOC) concentration. The relationship shows that, in the river plume areas (Rhine in the North Sea and Rhône in the Gulf of Lions), a consistent fraction of DOC (from 40% to 60% of the average of the DOC measured) is non-absorbing in visible light range, where the dissolved organic matter (DOM) is typically absorbent. In comparison, in the open sea, apparently not affected by the continental inputs, the entire DOC belongs to the chromophoric DOM whose specific absorption is lower (5 to 10 times) than that found in the river plume areas.  相似文献   

2.
The photoreactivity of chromophoric dissolved organic matter (CDOM) transported to Arctic shelf environments by rivers has only recently been studied and its quantitative role in Arctic shelf biogeochemistry has received little attention. Sunlight exposure experiments were performed on CDOM collected over a three year period (2002 to 2004) from river, estuary, shelf, and gulf regions of the Western Canadian Arctic. Decreases in CDOM absorption, synchronous fluorescence (SF), and dissolved organic carbon (DOC) concentration were followed after 3 days of exposure, and in two experiments, six optical cutoff filters were used to incrementally remove ultraviolet radiation incident on the samples. Apparent quantum yields for CDOM photobleaching (AQYble) and for DOC photomineralization (AQYmin) were computed, as were two AQY spectra (ble and min) for the Mackenzie River and a sample from the Mackenzie Shelf. The photoreactivity of Mackenzie River CDOM was highest after break-up and peak discharge and lowest in late summer. The half-lives of CDOM and DOC were estimated at 3.7 days and 4.8 days, respectively, when Mackenzie River water was exposed to full sunlight. Photobleaching of Mackenzie River CDOM fluorescence after most UV-B wavelengths were removed increased the correlation between the river and offshore waters in the Beaufort Sea. When light attenuation from particle- and CDOM-rich river water was considered for the Mackenzie Shelf, our photodegradation models estimated around 10% loss of absorption and < 1% DOC loss, suggesting that sunlight exposure does not substantially degrade CDOM on Arctic shelves.  相似文献   

3.
依据2017年8—9月对黄海海域溶解有机物(DOM)的调查，探讨了夏季黄海海水中溶解有机碳(DOC)和有色溶解有机物(CDOM)的空间分布特征。在表层海水中，受陆源影响较大的近岸海域CDOM含量相对较高，北黄海冷水团区域由于水产养殖的饵料引起DOC浓度升高，且该部分DOC以无色为主。DOC浓度随深度逐渐降低，而CDOM逐渐升高，该特征在冷水团区域更为显著，因此DOC和CDOM在冷水团区域的表底差异远大于浅水区的非冷水团区域。陆源输入和初级生产是引起表层DOC升高的主要原因，而光漂白则引起CDOM降低，同时光漂白还导致表层水体中CDOM分子量和芳香性低于底层。底层溶解氧饱和度在冷水团为80%～93%，均表现为弱不饱和状态。层化不仅阻碍了O2向底层水体输送，还抑制了DOC和CDOM的垂向混合，这是引起冷水团区域表底层DOC和CDOM差异较大的主要原因。  相似文献   

4.
《Marine Chemistry》2002,77(1):23-41
Chromophoric dissolved organic matter (CDOM) is the light absorbing fraction of dissolved organic carbon (DOC). The optical properties of CDOM potentially permit remote sensing of DOC and CDOM, and correction for CDOM absorption is essential for remote sensing of chlorophyll a (chl a) in coastal and estuarine waters. To provide data for this purpose, we report the distributions of CDOM, DOC, and chl a from seven cruises in Chesapeake Bay in 1994–1997. We observed non-conservative distributions of chl a and DOC in half of the cruises, indicating net accumulations within the estuary; however, there were no net accumulations or losses of CDOM, measured as absorption at 355 nm or as fluorescence. Freshwater end member CDOM absorption varied from 2.2 to 4.1 m−1. Coastal end member CDOM absorption was considerably lower, ranging over 0.4–1.1 m−1. The fluorescence/absorption ratio was similar to those reported elsewhere for estuarine and coastal waters; however, in the lower salinity/high CDOM region of the Bay, the relationship was not constant, suggestive of the mixing of two or more CDOM sources. Chl a was not correlated with the absorption for most of the cruises nor for the data set as a whole; however, CDOM and DOC were significantly correlated, with two groups evident in the data. The first group had high CDOM concentrations per unit DOC and corresponded to the conservative DOC values observed in the transects. The second group had lower CDOM concentrations per unit DOC and corresponded to the non-conservative DOC values associated with net DOC accumulation near the chl a maximum on the salinity gradient. This indicates the production of non-chromophoric DOC in the region of the chl a maximum of Chesapeake Bay. In terms of remote sensing, these data show that (1) the retrieval of the absorption coefficient of CDOM from fluorescence measurements in the Bay must consider the variability of the fluorescence/absorption relationship, and (2) estimates of DOC acquired from CDOM absorption will underestimate DOC in regions with recent, net accumulations of DOC.  相似文献   

5.
Chromophoric dissolved organic matter (CDOM) is the major light absorber in the Baltic Sea. In this study, excitation emission matrix (EEM) fluorescence spectra and UV–visible absorption spectra of CDOM are reported as a function of salinity. Samples from different locations and over different seasons were collected during four cruises in 2002 and 2003 in the Baltic Sea in both Pomeranian Bay and the Gulf of Gdansk. Absorption by CDOM decreased with increased distance from the riverine source and reached a relatively stable absorption background in the open sea. Regression analysis showed that fluorescence intensity was linearly related to absorption by CDOM at 375 nm and aCDOM(375) absorption coefficients were inversely related to salinity. Analysis of CDOM-EEM spectra indicated that a change in composition of CDOM occurred along the salinity gradient in the Baltic Sea. Analysis of percent contribution of respective fluorophore groups to the total intensity of EEM spectra indicated that the fluorescence peaks associated with terrestrial humic components of the CDOM and total integrated fluorescence decreased with decreasing CDOM absorption. In contrast, the protein-like fraction of CDOM decreased to a lesser degree than the others. Analysis of the percent contribution of fluorescence peak intensities to the total fluorescence along the salinity gradient showed that the contribution of protein-like fluorophores increased from 2.6% to 5.1% in the high-salinity region of the transect. Fluorescence and absorption changes observed in the Baltic Sea were similar to those observed in similar transects that have been sampled elsewhere, e.g. in European estuaries, Gulf of Mexico, Mid-Atlantic Bight and the Cape Fear River plume in the South Atlantic Bight, although the changes in the Baltic Sea occurred over a much smaller salinity gradient.  相似文献   

6.
In this study, the CDOM absorption coefficient at 350 nm [aCDOM(350)] and CDOM excitation emission matrix (EEM) fluorescence were used to estimate annual fluxes of dissolved organic carbon (DOC) from the Cape Fear River to Long Bay in the South Atlantic Bight. Water samples were collected during a 3.5 year period, from October 2001 through March 2005, in the vicinity of the Cape Fear River (CFR) outlet and adjacent Onslow Bay (OB). Parallel factor analysis (PARAFAC) of CDOM EEM spectra identified six components: three terrestrial humic-like, one marine humic-like and two protein-like. Empirical relationships were derived from the PARAFAC model between DOC concentration and aCDOM(350), total fluorescence intensity and the intensities of respective EEM components. DOC concentration and CDOM optical parameters were very well correlated and R2 values ranged from 0.77 to 0.90. Regression analyses revealed that the non-absorbing DOC fraction, in DOC concentration estimated from CDOM optical parameters, varied with the qualitative composition of the CDOM. DOC concentration and intensity of the humic-like CDOM components characterized by excitation maxima at longer wavelengths have significantly higher estimated non-absorbing DOC compared to the analogous relationships between DOC and intensity of the humic-like CDOM components characterized by excitation maxima at shorter wavelengths. The relationships between DOC concentration and intensity of one of the protein-like components resulted in significantly reduced non-absorbing DOC fraction in DOC concentration estimation. Results of regression analyses between fluorescence intensities of specific EEM components and CDOM-specific absorption coefficients suggest that the relative proportion of humic-like CDOM components (characterized by excitation maximum at longer wavelengths) and the main protein-like component have the most impact on the values of a?CDOM(350). Based on the relationships between aCDOM(350), Cape Fear River flow, and DOC concentrations, DOC fluxes were estimated for 2002, 2003 and 2004. DOC fluxes varied from 1.5 to 6.2 × 1010 g C yr? 1, depending on river flow.  相似文献   

7.
The retrieval of dissolved organic carbon (DOC) distribution by remote sensing is mainly based on the empirical relationship of DOC concentration and colored dissolved organic matter (CDOM) concentration in many literatures. To investigate the nature of this relationship, the distributions and mixing behaviors of DOC and CDOM are reviewed in the world’s major estuaries and bays. It is found that, generally, the CDOM concentration is well correlated with the salinity in most estuaries, while DOC usually shows a nonconservative behavior which leads to a weak correlation between the DOC concentration and the CDOM concentration. To establish a good satellite reversion of the DOC concentration, the East China Sea(ECS) was taken as an example, and the mixing behavior of DOC and CDOM as well as the influence of biogeochemical processes were analyzed except for the physical mixing process with the data from late autumn (November, 2010) and winter (December, 2009) cruises. In the two ECS cruises, the CDOM concentration was found to be tightly correlated with the salinity, influenced little by the photochemical or biological processes. The data from the winter cruise show that DOC followed a conservative mixing along the salinity gradient, while in the late autumn cruise it was significantly affected by the biological activities, resulting in a poor correlation between the DOC and the CDOM. Accordingly, an improved DOC algorithm (CSDM) was proposed: when the biological influence was significant (Chl a greater than 0.8 μg/dm3 ), DOC was retrieved by the conservative and biological model, and if the conservative mixing was dominant (Chl a less than 0.8 μg/dm3 ), the direct DOC concentration and CDOM concentration relationship was used. Based on the proposed algorithm, a reasonable DOC distribution for the ECS from satellite was obtained in this study, and the proposed method can be applied to the other large river-dominant marginal sea.  相似文献   

8.
The distribution and characteristics of coloured dissolved organic matter (CDOM) in the Baltic – North Sea transition zone were studied. The aim was to assess the validity of predicting CDOM absorption in the region on the basis of water mass mixing alone and demonstrate the utility of CDOM as an indicator of water mass mixing in coastal seas. A three-end-member mixing model representing the three major allochthonous CDOM sources was sufficient to describe the patterns in CDOM absorption distribution observed. The three-end-member water masses were the: Baltic outflow, German Bight and the central North Sea. Previously, it was thought that water from the German Bight transported northwards in the Jutland coastal current only sporadically influenced mixing between the Baltic and North Sea. The results from this study show that water from the German Bight is detectable at salinities down to 12 in the Kattegat and Belt Sea. On average, 23% of the CDOM in bottom waters of the Kattegat, Great Belt, Belt Sea, Arkona Sea and the Sound originated from the German Bight. Using this conservative mixing model approach, local CDOM inputs were detectable but found to be limited, representing only 0.25% of CDOM in the surface waters of the Kattegat and Belt Sea. The conservative mixing of CDOM makes it possible to predict its distribution and characteristics and offers a powerful tool for tracing water mass mixing in the region. The results also emphasize the need to include the Jutland Coastal current in hydrodynamic models for the region.  相似文献   

9.
Chromophoric dissolved organic matter (CDOM), as the light absorbing fraction of bulk dissolved organic matter (DOM), plays a number of important roles in the global and local biogeochemical cycling of dissolved organic carbon (DOC) and in controlling the optical properties of estuarine and coastal waters. Intertidal areas such as salt marshes can contribute significant amounts of the CDOM that is exported to the ocean, but the processes controlling this CDOM source are not well understood. In this study, we investigate the production of DOM and CDOM from the decomposition of two salt marsh cordgrasses, Spartina patens, a C4 grass, and Typha latifolia, a C3 grass, in well-controlled laboratory experiments. During the seven-week incubation period of the salt marsh grasses in oxic and anoxic seawater, changes in dissolved organic carbon (DOC) concentrations, dissolved nitrogen (DN) concentrations, stable carbon isotopic composition of DOC (DOC-δ13C), and CDOM fluorescence demonstrate a significant contribution of DOC and CDOM to estuarine waters from salt marsh plants, such as Spartina and Typha species. In the natural environment, however, the release processes of CDOM from different cordgrass species could be controlled largely by the in situ oxic and anoxic conditions present during degradation which affects both the production and decomposition of DOC and CDOM, as well as the optical properties of CDOM in estuarine and coastal waters.  相似文献   

10.
河口有色溶解有机物（colored dissolved organic matter,CDOM）的分布是各种物理-生物地球化学过程共同作用的结果。为实现河口高动态变化CDOM的监测，遥感是一种重要的手段。由珠江口四个不同季节的航次获得的实测数据，本文构建了一个遥感算法以反演CDOM在400 nm的吸收系数（aCDOM （400））。该算法使用以波段反射率比值Rrs （667）/Rrs （443）和Rrs （748）/Rrs （412）为自变量。将构建的算法应用于2002-2014年的MODIS/Aqua数据，本文计算了珠江口不同季节的aCDOM （400）气候态分布。CDOM的分布主要受珠江径流量和区域水下地形特征的影响。沿着垂直于水深梯度的断面，气候态aCDOM （400）呈指数减少（y=aebx,b<0），但不同季节差异很大。珠江口CDOM主要是河流淡水输运而来。其中，富里酸比例随盐度的增加而降低。基于构建的算法、CDOM保守混合方程和径流量，本文由MODIS/Aqua数据进一步估算了2002-2014年夏季和冬季珠江DOC的有效入海浓度和有效入海通量。珠江的有效入海浓度和有效入海通量都与流量存在正相关关系，且在夏季的相关性更明显，R2分别为0.698和0.9657。  相似文献   

11.
Systematic water sampling for characterization of chromophoric dissolved organic matter (CDOM) in the coastal South Atlantic Bight, was conducted as part of the long term Coastal Ocean Research and Monitoring Program (CORMP). Water samples were collected during a 3.5 year period, from October 2001 until March 2005, in the vicinity of the Cape Fear River (CFR) outlet and in adjacent Onslow Bay (OB). During this study there were two divergent hydrological and meteorological conditions in the CFR drainage area: a severe drought in 2002, followed by the very wet year of 2003. CDOM was characterized optically by the absorption coefficient at 350 nm, the spectral slope coefficient (S), and by Excitation Emission Matrix (EEM) fluorescence. Parallel Factor Analysis (PARAFAC) was used to assess CDOM composition from EEM spectra and six components were identified: three terrestrial humic-like components, one marine humic-like component and two protein-like components. Terrestrial humic-like components contributed most to dissolved organic matter (DOM) fluorescence in the low salinity plume of the CFR. The contribution of terrestrial humic-like components to DOM fluorescence in OB was much smaller than in the CFR plume area. Protein-like components contributed significantly to DOM fluorescence in the coastal ocean of OB and they dominated DOM fluorescence in the Gulf Stream waters. Hydrological conditions during the observation period significantly impacted both concentration and composition of CDOM found in the estuary and coastal ocean. In the CFR plume, there was an order of magnitude difference in CDOM absorption and fluorescence intensity between samples collected during the drought compared to the wet period. During the drought, CDOM in the CFR plume was composed of equal proportions of terrestrial humic-like components (ca. 60% of the total fluorescence intensity) with a significant contribution of proteinaceous substances (ca. 20% of the total fluorescence). During high river flow, CDOM was composed mostly of humic substances (nearly 75% of total fluorescence) with minor contributions by proteinaceous substances. The impact of changes in fresh water discharge patterns on CDOM concentration and composition was also observed in OB, though to a lesser degree.  相似文献   

12.
厦门湾有色溶解有机物的光吸收特性研究   总被引：3，自引：0，他引：3  
研究了厦门湾九龙江河口区、西海域、同安湾及东侧水道海水中有色溶解有机物(CDOM)的光吸收特性,分析了CDOM的河口行为,并讨论了CDOM光吸收特性与其荧光性质之间的关系。结果表明,厦门湾表层海水CDOM光吸收系数a(355)的水平分布表现为河口区最高、东侧水道最低、西海域和同安湾介于两者之间,底层水a(355)的分布与表层基本相似,表明陆源河流输入是厦门湾CDOM的主要来源;a(355)的垂直分布为表层高于底层,主要受水文和生物因素控制。厦门湾表层水CDOM光谱斜率S的平均值介于0.014—0.018nm-1,但河口低盐度区S值较小,反映陆源腐殖质的影响。a(355)在河口混合中呈保守行为,表明CDOM具有良好的保守性质。CDOM的吸收系数a(355)与其荧光强度之间表现为较好的相关关系,指示可以用灵敏度更高的荧光方法来研究CDOM的分布和行为。  相似文献   

13.
The distribution and chemical properties of chromophoric dissolved organic matter (CDOM) in the Jiaozhou Bay, China were examined during four cruises in 2010-2011. The influence of freshwater and industrial and municipal sewage along the eastern coast of the bay was clearly evident as CDOM levels (defined as a 305 ), and dissolved organic carbon (DOC) concentrations were well correlated with salinity during all the cruises. Moreover, DOC concentrations were significantly correlated with chlorophyll a concentrations in the surface microlayer as well as in the subsurface water. The concentrations of DOC and CDOM displayed a gradually decreasing trend from the northwestern and eastern coast to the central bay, and the values and gradients of their concentrations on the eastern coast were generally higher than those on the western coast. In addition, CDOM and DOC levels were generally higher in the surface microlayer than in the subsurface water. In comparison with DOC, CDOM exhibited a greater extent of enrichment in the microlayer in each cruise, with average enrichment factor (E F ) values of 1.38 and 1.84, respectively. Four fluorescent components were identified from the surface microlayer and subsurface water samples and could be distinguished as peak A, peak T, peak B and peak M. For all the cruises, peak A levels were higher in the surface microlayer than in the subsurface water. This pattern of variation might be attributed to the terrestrial input.  相似文献   

14.
The quantity of chromophoric or coloured dissolved organic matter (CDOM) released by eleven species of intertidal and sub-tidal macroalgae commonly found on UK shores was investigated. The subsequent breakdown of CDOM was also measured by exposing collected CDOM samples to light and dark conditions for over two weeks. CDOM absorption properties were compared at a fixed wavelength of 440 nm and across two integrated wave - bands; UV-A (400–315 nm) and UV-B (315–280 nm). Absorption spectra of macroalgal CDOM samples were typically characterized by peaks and shoulders in the UV bands, features which were species specific. The spectral slope, derived using the log-linear method, proved to be very specific to the species and to the effect of light. Slope measurements ranged from 0.010 to 0.027 nm−1, in the range of normal seawater values. Significantly more CDOM was produced by algae which were illuminated, providing evidence for a light driven exudation mechanism. Averaged across all species, exudation in the dark accounted for 63.7% of that in the light in the UV-B band. Interspecific differences in exudation rate encompassed an order of magnitude, with the highest absorption measurements attributable to brown algae. However, some brown algae produced considerably less CDOM (e.g. Pelvetia canaliculata), which were more comparable to the green and red species. Over an exposure time of 16 days, significant photochemical degradation of CDOM was observed using a natural summer sunlight regime, showing that natural solar radiation could be an important removal mechanism for newly produced algal CDOM. Though the most obvious effect was a decrease in absorption, photo-bleaching also caused a significant increase in the spectral slope parameter of 0.004 nm−1.  相似文献   

15.
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   

16.
We analyze a two-year time-series of chromophoric dissolved organic matter (CDOM) light absorption measurements in the upper 400 m of the water column at the BOUSSOLE site in the NW Mediterranean Sea. The seasonal dynamics of the CDOM light absorption coefficients at 440 nm (acdom(440)) is essentially characterized by (i) subsurface maxima forming in spring and progressively reinforcing throughout summer, (ii) impoverishment in the surface layer throughout summer and (iii) vertical homogeneity in winter. Seasonal variations of the spectral dependence of CDOM absorption, as described by the exponential slope value (Scdom), are characterized by highest values in summer and autumn at the surface and low values at the depths of acdom(440) subsurface maxima or just below them. Variations of acdom(440) are likely controlled by microbial digestion of phytoplankton cells, which leads to CDOM production, and by photochemical destruction (photobleaching), which leads to CDOM degradation. Photobleaching is also the main driver of Scdom variations. Consistently with previous observations, acdom(440) for a given chlorophyll a concentration is higher than expected from Case I waters bio-optical models. The total non-water light absorption budget shows that surface waters at the BOUSSOLE site are largely dominated by CDOM during all seasons but the algal bloom in March and April. These results improve the knowledge of CDOM absorption dynamics in the Mediterranean Sea, which is scarcely documented. In addition, they open the way to improved algorithms for the retrieval of CDOM absorption from field or satellite radiometric measurements.  相似文献   

17.
The optical properties of coloured dissolved organic matter (CDOM) can be used, in some environments, to trace water masses and provide information about the dynamics of the dissolved organic fraction in natural waters. This work presents the results from a modelling exercise, laboratory experiment and field data, which describe the variations in the optical properties of CDOM during mixing. The exponential slope coefficient (S) is frequently used to characterise different CDOM pools; however, its behaviour during conservative mixing of two different CDOM types is often misunderstood. Identification of a theoretical conservative mixing line allows the rapid identification of non-conservative processes (e.g. in situ production, flocculation and degradation) acting on the pool during mixing. The results suggest that some of the patterns reported in the literature could purely be a result of conservative mixing rather than a product of non-conservative processes.  相似文献   

18.
INTRODUCTIONDissolvedorganiccarbon (DOC)makesupthesecondlargestofthebioactivepoolsofcar bonintheocean ,secondtothelargestpoolofdissolvedinorganiccarbon .Theglobaldissolvedorganiccarbonpoolisestimatedtobe 6 85Gt,avaluecomparabletothemassofCO2 intheat mosphere (Hedges,1 992 ) .Thesizeofthereservoir,aswellasitsdynamics ,indicatesthatDOCplaysacentralroleintheoceancarboncycle .AsitrelatestogreenhousegasessuchasCO2 andassociatesclimatecycle ,oceanicDOCbiogeochemicalcycleshavebeenoneoftheh…  相似文献   

19.
The distribution and optical absorption characteristics of chromophoric dissolved organic matter (CDOM) were systematically investigated along three meridional transects in the North Atlantic Ocean and Caribbean Sea conducted as part of the 2003 US CLIVAR/CO2 Repeat Hydrography survey. Hydrographic transects covered in aggregate a latitudinal range of 5° to 62° north along longitudes 20°W (line A16N, Leg 1), 52°W (A20), and 66°W (A22). Absorption spectra of filtered seawater samples were collected and analyzed for depths ranging from the surface to ∼6000 m, sampling all the ocean water masses in the western basin of the subtropical North Atlantic and several stations on the North and South American continental slopes. The lowest surface abundances of CDOM (< 0.1 m−1 absorption coefficient at 325 nm) were found in the central subtropical gyres while the highest surface abundances (∼0.7 m−1) were found along the continental shelves and within the subpolar gyre, confirming recent satellite-based assessments of surface CDOM distribution. Within the ocean interior, CDOM abundances were relatively high (0.1–0.2 m−1 absorption coefficient at 325 nm) except in the subtropical mode water, where a local minimum exists due to the subduction of low CDOM surface waters during mode water formation. In the subthermocline water masses of the western basin, changes in CDOM abundance are not correlated with increasing ventilation age as assessed using chlorofluorocarbon (CFC) concentrations and the atmospheric CFC history. But dissolved organic carbon (DOC) mass-specific absorption coefficients of CDOM increase with increasing ventilation age in the deep sea, indicating that CDOM is a refractory component of the DOC pool. The overall CDOM distribution in the North Atlantic reflects the rapid advection and mixing processes of the basin and demonstrates that remineralization in the ocean interior is not a significant sink for CDOM. This supports the potential of CDOM as a tracer of ocean circulation processes for subducted water masses.  相似文献   

20.
A high temperature catalytic oxidation (HTCO) technique was used to measure dissolved organic carbon (DOC) during seasonal surveys of the Tamar Estuary, U.K. At the time of the programme, the field of DOC analysis had been plagued by numerous analytical difficulties. However, using thorough calibration of the analytical systems and the systematic analysis of an internal reference material, a valuable estuarine DOC data set was produced. The range of DOC concentrations observed (478–110 μM C) is consistent with the published data for riverine and coastal sea waters respectively. The Tamar Estuary is a freshwater DOC-dominated system, with strong correlation between lateral DOC distribution and salinity. However, mixing behaviour was not strictly conservative. During tidal cycle studies at a fixed station, DOC concentrations appeared to be uncoupled from salinity, and were inversely related to turbidity. It is concluded that tidally-induced resuspension of bottom sediments provided the dominant control mechanism for DOC concentration. The Tamar Estuary shows contrasting behaviour to the larger, more heavily impacted, Severn Estuary. Hence it is likely that the behaviour of DOC in estuaries cannot be classified as typical per se, but is a function of the natural and anthropogenic characteristics of the catchment and hydrology.  相似文献   

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