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.
To verify the actual usefulness of time-dependent tracer dating techniques in the ocean, we simultaneously obtained two cross sections of sulfur hexafluoride (SF6) and chlrofluoromethanes (CFC-11, trichlorofluoromethane; CFC-12, dichloro-difluromethane; CFC-113, trichlorotrifluoroethane) in the western North Pacific in 1998. The vertical distribution patterns of SF6 and CFC-113 were similar in shape to those of CFC-11 and CFC-12. Maximum penetration depths of SF6 and CFC-113 remained around 800 m in the subpolar region and 400 m in the tropical region, while the maximum penetration depths of CFC-11 and CFC-12 were still found below 1000 m depth. We also found all maximum contents of these tracers around 26.6−26.8σθ with a gradual decrease southward. This suggested that a new subsurface water mass in the subpolar region spread out over the entire North Pacific, which agrees closely with previous studies based on the salinity minimum. Moreover, we compared the tracer ages (the elapsed period of a water mass from when the water mass left from the ocean surface) using ten time-dependent tracer dating techniques, CFC-11, CFC-12, CFC-113, SF6, CFC-11/CFC-12, CFC-113/CFC-11, CFC-113/CFC-12, SF6/CFC-11, SF6/CFC-12 and SF6/CFC-113. This quantitative evaluation of multiple tracer dating techniques in the ocean was the first confirmation of its usefulness based on the observational data on the ocean basin-wide scale. We conclude that SF6/CFC-11, SF6/CFC-12, SF6/CFC-113 and SF6 dating techniques would be the most promising tools for determining the age of water mass not only just for the past several decades but for the future, too. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2.
汪浩  何真  张婧  杨桂朋 《海洋学报》2018,40(10):96-109
运用吹扫-捕集气相色谱法测定了2017年夏季长江口及其邻近海域海水中4种常见的挥发性卤代烃（VHCs，包括一氟三氯甲烷（CFC-11）、碘甲烷（CH3I）、三氯甲烷（CH3CCl3）和四氯乙烯（C2Cl4））以及大气中CFC-11、CH3I和C2Cl4的浓度。结果表明，表层海水中4种VHCs浓度的水平分布受长江径流输入影响强烈，整体上呈现近岸高、远海低的趋势。垂直方向上4种VHCs浓度最高值出现在10 m水层，长江口内断面的浓度整体高于口外断面的浓度。海水中VHCs的浓度分布受水文环境、生物释放和人为因素等的共同影响。相关性分析表明CH3I与Chl a浓度不存在明显的相关性，而CFC-11与CH3I、C2Cl4浓度存在显著相关性（P<0.01），表明调查海域人为源对CH3I和C2Cl4的影响大于天然源。大气中CFC-11、CH3I和C2Cl4的浓度分布整体上呈现近岸高、远海低的趋势。CFC-11的浓度低于全球平均值，表明我国CFC-11的排放得到了有效控制。后向轨迹分析表明来自近岸的陆源污染物的扩散和输送是调查海域大气中3种VHCs的重要来源。CFC-11、CH3I和C2Cl4的海-气通量平均值分别为24.99 nmol/（m2·d）、7.80 nmol/（m2·d）、1.55 nmol/（m2·d），表明夏季长江口及其邻近海域是大气中这3种VHCs的源。  相似文献   

3.
  相似文献   

4.
Copper concentrations have been measured in more than 200 samples collected from an Alaskan fjord and continental shelf and slope regions in the northwestern Gulf of Alaska. Concentrations were lowest (2·1 nmol kg−1) at depths of 400–1000 m in the continental slope waters of the Gulf of Alaska. Copper increased systematically with decreasing salinities shoreward to concentrations >30 nmol kg−1 in fjord surface waters during summer months of high freshwater runoff. Copper concentrations increased with depth at an inner fjord station where deep basin waters have restricted circulation, and these data together with surface (<5 cm) pore water copper concentrations (mean=122 nmol kg−1) about an order of magnitude higher than bottom water copper concentrations are indicative of a flux of copper across the sediment-seawater interface. This latter was estimated at 32±12 nmol cm−2 annually, and represented less than 20% of the annual input to fjord surface water (228–411 nmol cm−2) added during summer months. Mass balances in bottom waters indicate a vigorous recycling of copper with a residence time estimated at 21±11 days. Most copper that is remobilized in surface sediments is returned to bottom waters and little (3%) is removed by subsequent diagenetic reaction in the buried sediments. However, an estimate of copper accumulating in anoxic fjord sediments was comparable with copper added to fjord surface waters suggesting that input-removal reactions rather than internal cycling controls copper geochemistry in this estuary.  相似文献   

5.
Eukaryotic phytoplankton such as diatoms and prymnesiophytes produce biogenic halocarbons in the ocean that serve as important sources of chlorine and bromine to the atmosphere, but the role of cyanobacteria in halocarbon production is not well established. We studied distributions of chloroform (CHCl3), carbon tetrachloride (CCl4), methylene bromide (CH2Br2) and bromoform (CHBr3) in relation to phytoplankton composition, determined from pigment analysis complemented by microscopic examination, for one month in coastal waters of the eastern Arabian that experienced a Trichodesmium bloom that typically occurs during the Spring Intermonsoon season. High concentrations of zeaxanthin (23 μg l−1), alpha beta betacarotene (6 μg l−1) and chlorophyll a (67 μg l−1) were found within the bloom whereas the marker pigment concentrations were low outside the bloom. CHCl3 and CCl4 occurred in relatively high concentrations in surface waters whereas CH2Br2 and CHBr3 were restricted to the subsurface layer. Chlorinated halocarbons were positively inter-correlated and with CHBr3. The observed spatial and temporal trends in brominated compounds appear to be related to the abundance of Trichodesmium although correlations between concentrations of brominated compounds with various marker pigments were poor and statistically non-significant. The results support the existence of multiple sources and sinks of halogenated compounds, which might obscure the relationship between halocarbons and phytoplankton composition.  相似文献   

6.
Capabilities of the total column monitoring of different minor gaseous compounds of the atmosphere with the satellite IRFS-2 Fourier interferometer have been studied. The possibilities of determining the СО2, О3, СH4, HNO3, N2O, CH3OH, HCFC-22, CFC-11, CFC-12, PAN, and ССl4 total columns have been investigated on the basis of line-by-line calculations of the forward problem operator and calculation of error matrices by the optimal estimation method. It has been shown that the IRFS-2 device could be used to measure the total columns of СО2, О3, N2O, СH4, and HNO3. In the information-gathering mode, it is also possible to retrieve the CH3OH, HCFC-22, CFC-11, CFC-12, PAN, and ССl4 total columns due to the suppression of random measurement errors.  相似文献   

7.
Total arsenic, arsenate and arsenite concentration profiles for the water column of Saanich Inlet, an intermittently anoxic fjord located on Vancouver Island, B.C., Canada, were measured using independent analytical techniques for total arsenic and arsenic speciation to evaluate the accuracy of the speciation technique in both oxic and anoxic marine environments. Total arsenic profiles indicate a mid-depth minimum of about 1.0 ppb above the oxic—anoxic interface and an enrichment in the anoxic zone to about 2.0 ppb. This minimum may be due to either advection of arsenic-poor water into Saanich Inlet at mid-depth or arsenic incorporation onto solid phases within a bacteria- and manganese-rich particulate layer located immediately above the oxic—anoxic interface and subsequent removal via sinking particulate material. Ratios of total arsenic to phosphorus in the deep, anoxic waters of the basin are similar to those reported for marine algae, suggesting that the enrichment of total arsenic within the anoxic bottom layer may be due to its release upon organic matter decomposition.Arsenate and arsenite concentration versus depth profiles indicate a rapid (but incomplete in a thermodynamic sense) response to the oxic—anoxic interface. The arsenate/ arsenite concentration ratio is 15/1 in the oxic region of the water column and 1/12 in the anoxic zone. Arsenate—arsenite interconversion occurs at a depth shallower than ferric-ferrous but deeper than MnO2 —Mn2+ interconversions.Measurements of arsenite oxidation rates at near-ambient arsenite concentrations and temperatures using an 74As3+ radioactive tracer technique indicate that arsenite oxidation is initially ten times faster in seawater taken from the manganese-rich particulate layer at 165 m depth than in seawater collected near the surface at 50 m depth. Addition of antibiotics to seawater from 165 m depth initially suppressed the rate of arsenite oxidation, indicating that it may be partially microbially mediated.  相似文献   

8.
氟里昂化学示踪技术在海洋研究中的应用   总被引：2，自引：0，他引：2  
氟里昂化学示踪是海洋科学研究的有效工具。文章着重介绍了CFC-11，CFC-12，CFC-113，CC14，SF6等氟里昂示踪物，阐述了氟里昂化学示踪技术在海洋水团运动、水团年龄及海气交换等方面的应用。  相似文献   

9.
Elevated methane (CH4) concentrations (128–2692×103 nM) occur in the hypersaline anoxic brine pools of Bannock and Urania Basins, eastern Mediterranean Sea, compared to low concentrations (17–80×103 nM) in the sediments below the anoxic brines. The CH4 enrichment in the brines might be due to the long residence time of the brine in the Basin. An attempt is made to determine the sources for the enriched dissolved CH4 by considering the influence of hydrothermal activity, the occurrence of sapropel layers (biogenic) and dissolution of gas hydrates. Furthermore, it is suggested that the enriched CH4 in Bannock and Urania Basins is diffused and mixed with the overlying waters by local upward transport mechanisms that selectively move CH4 upward in these Basins.  相似文献   

10.
Anoxic sulfidic waters provide important media for studying the effect of reducing conditions on the cycling of trace metals. In 1987–1988, dissolved and particulate trace metal (Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb) concentrations were determined in the water column of the anoxic Drammensfjord basins, southeastern Norway. The iminodiacetic acid type chelating resin (Chelex 100) was used for the preconcentration of trace metals. The trace metal concentrations were determined using atomic absorption spectrophotometry (AAS), differential pulse polarography (DPP), and differential pulse-anodic stripping voltammetry (DP-ASV).It was observed that the trace metals Mn and Fe were actively involved in the processes of redox cycling (oxidationreduction and precipitation-dissolution) at the O2/H2S interface. The dissolved concentrations of Mn, Fe and Co showed maxima just below the O2/H2S interface. The seasonal enhancement in the maxima of both dissolved and particulate Mn and Fe at the redox cline is mainly governed by the downward movement of water which carries oxygen. An association of Co with the Mn cycle was observed, while the total dissolved Ni was decreased by only 10–35% in the anoxic waters. The dissolved concentrations of Cu, Zn, Pb and, to a lesser extent, Cd decreased in the anoxic zone.  相似文献   

11.
Chlorofluorocarbon (CFC) 11 and 12 transports across the transoceanic World Ocean Circulation Experiment (WOCE) A25 section in the subpolar North Atlantic are derived from an inverse model using hydrographic and ADCP data (Lherminier et al., 2007). CFC and anthropogenic carbon (CANT) advective transports contrary to expected are uncoupled: CANT is transported northeastwards (82±39 kmol s?1) mainly within the overturning circulation, while CFC-11 and CFC-12 are transported southwestwards (?24±4 and ?11±2 mol s?1, respectively) as part of the large-scale horizontal circulation. The main reason for this uncoupled behaviour is the complex CFC vs. CANT relation in the ocean, which stems from the contrasting temperature relation for both tracers: more CANT dissolves in warmer waters with a low Revelle factor, while CFC’s solubility is higher in cold waters. These results point to CANT and CFC having different routes of uptake, accumulation and transport within the ocean, and hence: CANT transport would be more sensitive to changes in the overturning circulation strength, while CFC to changes in the East Greenland Current and Labrador Sea Water formation in the Irminger Sea. Additionally, CANT and CFCs would have different sensitivities to circulation and climate changes derived from global warming as the slowdown of the overturning circulation, increase stratification due to warming and changes in wind stress.  相似文献   

12.
The East/Japan Sea is a mid-latitude marginal sea that has undergone dramatic changes during the last 50–60 years. One of the most prominent characteristics of these changes is a rapid decrease in the amount of dissolved oxygen in deep waters. As a consequence of these changes, some investigators have even argued that the East/Japan Sea might become an anoxic sea in the next 200 years. While the causes of these changes are still under investigation, it has been shown that they are mainly due to modifications in the mode of the deep water ventilation system in the East/Japan Sea: a slowdown and complete cessation of bottom water formation accompanied by an enhancement of upper water formation instead. A simple moving-boundary box model (MBBM) was developed in order to analyze and quantify the processes involved in such changes over the last 50–60 years. Using a MBBM, we estimated the levels of several conservative chemical tracers (CFCs, Tritium, SF6, 137Cs) and bioactive tracers (oxygen and phosphate) in the deep water masses of the East/Japan Sea, comparing these with the historical data available, and making predictions for the near future. The model predicts that the East/Japan Sea should remain well-oxygenated, despite recent rapid oxygen decreases in its deep waters, accompanied by such structural changes as a shrinking of its oxygen-depleted deeper waters and an expansion of its oxygen-rich upper waters over the next few decades.  相似文献   

13.
Iodate (IO3−) is the predominant dissolved species of iodine in the oxygenated waters of the Mediterranean Sea. Iodide (I−) is present in significant quantities (up to 65 nM) in oxygenated waters in the photic zone and near the interface above the anoxic and saline Bannock Basin. Lesser quantities of I− (< 10 nM) are found throughout the rest of the oxic water column. An additional unidentified dissolved iodine species is present immediately above the anoxic interface.Total dissolved iodine (ΣI) increases dramatically across the seawater/brine interface. Part of this increase is undoubtedly the result of the dissolution of iodine-rich evaporites during formation of the brine bodies at the Tyro and Bannock Basins. The vertical distribution of ΣI and other dissolved chemical species (particularly PO43−) in the Bannock Basin brine, however, suggests an additional, present-day, diagenetic source of dissolved iodine to the brine. Based on the increase in the concentration of the most soluble major ions across the seawater/brine interface, 5–7 μM of the 11.5-μM increase in ΣI concentration must be attributed to diagenesis.  相似文献   

14.
The concentrations of total carbonate (Ct), sulphate, sulphide, thiols and oxygen, the ratio between the stable sulphur isotopes 34S and 32S in sulphate and sulphide, and the density (used to calculate salinity) were determined on samples from the water column of Framvaren, a superanoxic fjord in southern Norway. From a depth of 18m (the oxic-anoxic boundary) the initial sulphate concentration, ([SO4]init), as calculated from salinity, is significantly higher than the sum of the measured sulphur species. This is attributed to a loss of sulphur from the water column. The amount of total carbonate produced, corrected for the initial concentration (Ct - 2.4 Sal/35) is found to be proportional to the amount of sulphate consumed, ([SO4]init - [SO4]), according to the following relation Ct- 2.4 Sal/35 = 1.84 ([SO4]init - [SO4]). Isotopic fractionation caused by bacterial sulphate reduction in the anoxic part of the water column produces sulphide with a δ34S 40‰ lower than the δ34S for sulphate at corresponding depths. The isotopic fractionation also results in δ34S value for the remaining sulphate at depths below 80 m being considerably higher than the mean value for ocean water, which is close to + 20‰. The δ34S values for sulphate at depths between 10 and 50 m were lower than + 20‰ which indicates oxidation of sulphide, which follows upon diffusion of sulphide from deeper parts of the water column and inflow of oxygenated seawater over the sill into the anoxic water of the fjord. A conclusive scenario of the Framvaren sulphur chemistry is presented.  相似文献   

15.
Atmospheric and dissolved methane (CH4) and nitrous oxide (N2O) were measured in the unique coastal ecosystem of theBoddenwaters, including the western Oder estuary, (southern Baltic Sea) during five campaigns between 1994 and 1997. The CH4saturations, ranging from 105–15 500%, showed great spatial and temporal variability with maximum values in September and minimum values in December. The N2O saturations were in the range of 91–312% with a maximum in March. Enhanced concentrations of both gases were observed only in the western Oder estuary near the mouth of the Peene River. Thus, we conclude that the distributions of CH4and N2O in the investigatedBoddenwaters are, directly or indirectly, linked to the Peene River runoff and not to the Oder River. Our estimate of the annual CH4emissions from theBoddenwaters to the atmosphere indicates a significant contribution (c. 17%) to the overall CH4emissions from the Baltic Sea. In contrast, theBoddenwaters represent only a small source for atmospheric N2O.CH4production rates estimated from sediment slurry experiments revealed a significant spatial variability and indicated that methanogenic activity was related to acetate consumption in the surface sediment layer. Sedimentary CH4production might depend on different amounts of accumulation of organic material.  相似文献   

16.
An Ensemble Kalman Filter is applied to assimilate observed tracer fields in various combinations in the Bern3D ocean model. Each tracer combination yields a set of optimal transport parameter values that are used in projections with prescribed CO2 stabilization pathways. The assimilation of temperature and salinity fields yields a too vigorous ventilation of the thermocline and the deep ocean, whereas the inclusion of CFC-11 and radiocarbon improves the representation of physical and biogeochemical tracers and of ventilation time scales. Projected peak uptake rates and cumulative uptake of CO2 by the ocean are around 20% lower for the parameters determined with CFC-11 and radiocarbon as additional target compared to those with salinity and temperature only. Higher surface temperature changes are simulated in the Greenland–Norwegian–Iceland Sea and in the Southern Ocean when CFC-11 is included in the Ensemble Kalman model tuning. These findings highlights the importance of ocean transport calibration for the design of near-term and long-term CO2 emission mitigation strategies and for climate projections.  相似文献   

17.
The Arcachon lagoon is a 156 km2 temperate mesotidal lagoon dominated by tidal flats (66% of the surface area). The methane (CH4) sources, sinks and fluxes were estimated from water and pore water concentrations, from chamber flux measurements at the sediment–air (low tide), sediment–water and water–air (high tide) interfaces, and from potential oxidation and production rate measurements in sediments. CH4 concentrations in waters were maximal (500–1000 nmol l−1) in river waters and in tidal creeks at low tide, and minimal in the lagoon at high tide (<50 nmol l−1). The major CH4 sources are continental waters and the tidal pumping of sediment pore waters at low tide. Methanogenesis occurred in the tidal flat sediments, in which pore water concentrations were relatively high (2.5–8.0 μmol l−1). Nevertheless, the sediment was a minor CH4 source for the water column and the atmosphere because of a high degree of anaerobic and aerobic CH4 oxidation in sediments. Atmospheric CH4 fluxes at high and low tide were low compared to freshwater wetlands. Temperate tidal lagoons appear to be very minor contributor of CH4 to global atmosphere and to open ocean.  相似文献   

18.
Between 1980 and 1984 extensive studies were carried out in the Baltic Sea on trace metals (Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn) in water, suspended matter and sediments. The results enabled the influence of different factors on metal distribution patterns to be considered. The vertical profiles of dissolved and particulate metals in waters of the central deep basins reflect influences caused by oxygen deficiency and anoxic conditions in near-bottom water layers. Peculiarities at Station BY15 in the Gotland Deep included high dissolved Fe, Mn and Co concentrations and remarkable enrichment of Zn (0.64%), Cd (51 μg g−1) and Cu (0.15%) in particulate matter from the anoxic zone. Manganese-rich particles were accumulated above this layer.In fine-grained soft sediments below anoxic deep waters, maximum contents of Cd, Cu and Zn were observed, relative to other coring sites, between Bothnian Bay and Lübeck Bight. The Hg content in sediments probably reflects the joint flocculation with organic matter. Land-based sources seem to play the leading part for maximum lead contents.  相似文献   

19.
The magnitude of the exchange flux at the water–sediment interface was determined on the basis of the ammonia concentration gradient at the near-bottom water–interstitial interface and Fick's first law. It was established that in Puck Bay, ammonia almost always passes from the sediment to water. Ammonia flux varied from 5 to 1434 μmol NH4-N m−2 day−1. In total,c. 138·2 tonneammonia year−1pass from sediments of Internal Puck Bay to near-bottom water, the equivalent value for External Puck Bay being 686·9 tonne year−1. In total, about 825 tonne ammonia year−1passes from the sediment to near-bottom water of Puck Bay. In interstitial waters, ammonia occurred in concentrations varying over a wide range (3–1084 μmol NH4-N dm−3).The basic factors affecting the magnitude of ammonia concentration in interstitial waters included: oxidation of organic matter, type of sediment, and inflow of fresh underground waters to the region examined.This paper involves preliminary studies only and constitutes a continuation of the studies on ionic macrocomponents and phosphorus in interstitial waters of Puck Bay undertaken previously.  相似文献   

20.
With a limited number of properties (salinity, temperature, total dissolved inorganic carbon, total alkalinity, and oxygen) from a recent cruise in the tropical Atlantic Ocean, we use the simple and recent approach TrOCA (Tracer combining Oxygen, inorganic Carbon, and total Alkalinity) to estimate the distribution of anthropogenic CO2 along three latitudinal sections. In order to assess the quality of the anthropogenic CO2 distribution, results from the method are compared to the CFC-11 measurements. We discuss the large-scale distribution of the main water masses of the tropical Atlantic Ocean in the light of the anthropogenic CO2 and the CFC-11 distributions. Keeping in mind that the anthropogenic CO2 emission began 60 years earlier than that of CFC-11, the former provides new insight on the local circulation and efficiency of the tropical waters to store the atmospheric carbon.  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