Assessing site-specific effects of TBT contamination with mussel growth rates     

Michael H. Salazar  Sandra M. Salazar 《Marine environmental research》1991,32(1-4)

During nine field transplant tests in San Diego Bay (1987–1990), juvenile mussels were exposed to mean concentrations of tributyltin (TBT) in ambient seawater ranging from 2 to 530 ng liter⁻¹ for 12 weeks under natural conditions. A total of 79 cages with 18 mussels each were monitored at 18 different sites. Growth and seawater TBT concentrations were measured weekly or on alternate weeks (biweekly). Mean growth rates ranged from 17 to 505 mg week⁻¹ (0·2 to 2·5 mm week⁻¹). Accumulation of TBT in mussel tissues was measured at the end of each 12-week test exposure and ranged from 0·1 to 3·2 μg g⁻¹ TBT wet weight. The frequency of the measurements and the integration of chemical and biological measurements improved the accuracy of the assessment over more traditional approaches. Growth was significantly related to seawater and tissue TBT. The statistical relationships with growth effects were used to estimate chemical effect zones for TBT in San Diego Bay. Site-specific differences were distinguished by additional statistical analyses and consideration of environmental significance.  相似文献   

Evaluation of atmospheric transport as a nonpoint source of polycyclic aromatic hydrocarbons in marine sediments of the Eastern Mediterranean   总被引：1，自引：0，他引：1  

Manolis Tsapakis  Euripides G. Stephanou  Ioannis Karakassis 《Marine Chemistry》2003,80(4):283-298

Coastal marine sediment, air and seawater samples were collected at six sampling stations in the Eastern Mediterranean Sea distant from pollutant point sources. All sediment samples were analyzed to determine polycyclic aromatic hydrocarbon (PAH), black carbon (BC) and organic carbon (OC) contents. The PAH contents of gaseous and seawater samples of the study were determined in order to evaluate the role of air–sea exchange as PAH nonpoint source to the marine sediments. The average concentration of the total PAHs (∑PAHs) in the sediments varied from 2.2 to 1056.2 ng g⁻¹ dry weight. The average BC and OC contents varied from 0.3 to 5.6 and from 2.9 to 21.4 mg g⁻¹ dry weight, respectively. ∑PAH concentration in the marine atmosphere varied from 20.0 to 83.2 ng m⁻³. Air–water exchange flux (F_A–W) estimation has indicated air transport as a significant source of PAHs to pristine marine sediments of Eastern Mediterranean. In addition, the significant correlation between the PAHs and the organic and soot carbon content further suggests the importance of atmospheric input of PAHs to the sediments.  相似文献   

The reliability of analytical data for tributyltin (TBT) in sea water and its implications on water quality criteria     

James W. Readman  Laurence D. Mee 《Marine environmental research》1991,32(1-4)

To investigate the reliability of analytical data for tributyltin (TBT) in sea water, split water samples were distributed to ten laboratories in six countries. The sub-surface samples comprised: (i) an offshore (0·5 km) water sample, (ii) the same sample but spiked with an undisclosed quantity of TBT standard compound (175 ng TBT⁺ liter⁻¹), and (iii) a sample taken from a yacht marina. The seven acceptable data sets were in good agreement for the spiked sample (178 ± 26 ng TBT⁺ liter⁻¹) but showed a greater variation in concentrations reported for the yacht marina sample (366 ± 93 ng TBT⁺ liter⁻¹). Atomic absorption and gas chromatographic-flame photometric detection techniques produced results of similar accuracy and precision. Samples acidified with 1 ml of 10% (v/v) acetic acid appeared stable for more than 2 weeks when stored refrigerated and in darkness. Analyses of the offshore seawater sample revealed TBT contamination (9 ± 7 ng TBT⁺ liter⁻¹) indicating dispersion of the compound to the shelf waters off Monaco. The spread in values reported by the laboratories demonstrates inherent difficulties in obtaining good precision below approximately 20 ng TBT⁺ liter⁻¹. This observation is discussed with respect to the setting and enforcing of water quality standards.  相似文献   

Butyltins in marine waters of The Netherlands in 1988 and 1989; Concentrations and effects   总被引：1，自引：0，他引：1  

R. Ritsema  R. W. P. M. Laane 《Marine environmental research》1991,32(1-4)

Specific effects of tributyltin (TBT) on Crassostrea gigas—valve thickening, and Nucella lapillus—imposex, were measured on local populations, relatively clean unaffected species from England were transferred to the Netherlands and exposed during six weeks to ambient TBT concentrations. Near marinas 50% of the exposed species were sterile after six weeks. In general, no dissolved butyltins were detected in the Rhine and Scheldt estuaries. In 1988 TBT concentrations in marinas ranged from 120 to 4000 ng litre⁻¹. In sediments (fraction <60 μm) and suspended particulate matter TBT concentrations reached up to 1200 ng g⁻¹. TBT concentrations in mussel tissue ranged from <1 to 2300 ng g⁻¹ based on a dry weight. In 1989 concentrations of dissolved TBT ranged from <0·1 to 7200 ng litre⁻¹. In 1989 a seasonal study in the marina of Colijnsplaat showed that dissolved butyltins increased from April to the end of May due to the launching of freshly painted boats, and decreased afterwards.  相似文献   

Effect of changes in water salinity on ammonium, calcium, dissolved inorganic carbon and influence on water/sediment dynamics     

P. Lpez 《Estuarine, Coastal and Shelf Science》2003,56(5-6):943-956

The effect of a sudden increase in salinity from 10 to 37 in porewater concentration and the benthic fluxes of ammonium, calcium and dissolved inorganic carbon were studied in sediments of a small coastal lagoon, the Albufera d'Es Grau (Minorca Island, Spain). The temporal effects of the changes in salinity were examined over 17 days using a single diffusion-reaction model and a mass-balance approach. After the salinity change, NH₄⁺-flux to the water and Ca-flux toward sediments increased (NH₄⁺-flux: 5000–3000 μmol m⁻² d⁻¹ in seawater and 600/250 μmol m⁻² d⁻¹ in brackish water; Ca-flux: −40/−76 meq m⁻² d⁻¹ at S=37 and −13/−10 meq m⁻² d⁻¹ at S=10); however, later NH₄⁺-flux decreased in seawater, reaching values lower than in brackish water. In contrast, Ca-flux presented similar values in both conditions. The fluxes of dissolved inorganic carbon, which were constant at S=10 (55/45 mmol m⁻² d⁻¹), increased during the experiment at S=37 (from 30 mmol m⁻² d⁻¹ immediately after salinity increase to 60 mmol m⁻² d⁻¹ after 17 days).In brackish conditions, NH₄⁺ and Ca²⁺ fluxes were consistent with a single diffusion-reaction model that assumes a zero-order reaction for NH₄⁺ production and a first-order reaction for Ca²⁺ production. In seawater, this model explained the Ca-flux observed, but did not account for the high initial flux of NH₄⁺.The mass balance for 17 days indicated a higher retention of NH₄⁺ in porewater in the littoral station in seawater conditions (9.5 mmol m⁻² at S=37 and 1.6 mmol m⁻² at S=10) and a significant reduction in the water consumption at both sites (5 mmol m⁻² at S=37; 35/23 mmol m⁻² at S=10). In contrast, accumulation of dissolved inorganic carbon in porewater was lower in seawater incubations (−10/−1 meq m⁻² at S=37; 50/90 meq m⁻² at S=10) and was linked to a higher efflux of CO₂ to the atmosphere, because of calcium carbonate precipitation in water (675/500 meq m⁻²). These results indicate that increased salinity in shallow coastal waters could play a major role in the global carbon cycle.  相似文献   

Inorganic carbon in the central California upwelling system during the 1997–1999 El Niño–La Niña event     

G. E. Friederich  P. M. Walz  M. G. Burczynski  F. P. Chavez 《Progress in Oceanography》2002,54(1-4)

Sea surface pCO₂ was monitored during 49 cruises from February 1997 to December 1999 along a section perpendicular to the central California Coast. Continuous measurements of the ocean–atmosphere difference of pCO₂ were made on a mooring in the same region from July 1997 to December 1999. The El Niño/La Niña cycle of 1997–1999 had a significant influence on local ocean–atmosphere CO₂ transfer. During the warm anomaly associated with El Niño, upwelling was suppressed and average sea surface pCO₂ was below atmospheric level. High rainfall and river runoff in the late winter and early spring of 1998 produced areas where pCO₂ was depressed by as much as 100 μatm. A flux ranging from 0.3 to 0.7 mol C m⁻² y⁻¹ from the atmosphere into the ocean was estimated for the El Niño period from wind and ΔpCO₂ data. Temperatures and upwelling returned to near normal in the summer of 1998, but a cold anomaly developed during autumn of that year. Temperature and pCO₂ data indicate that upwelling continued throughout much of the 1998–1999 winter and intensified significantly in the spring of 1999. During strong upwelling events, the estimate of ocean to atmosphere flux approached rates of 50 mol C m⁻² y⁻¹. The estimate for the average CO₂ flux from July 1998 to July 1999 was 1.5–2.2 mol C m⁻² y⁻¹ from the ocean to the atmosphere. While the flux estimate for the El Niño time period may be applicable to a larger area, the high ocean to atmosphere fluxes during La Niña might be the result of sampling near a zone of intense upwelling.  相似文献   

fCO₂ variability at the CARIACO tropical coastal upwelling time series station     

Y.M. Astor  M.I. Scranton  F. Muller-Karger  R. Bohrer  J. García   《Marine Chemistry》2005,97(3-4):245-261

Monthly seawater pH and alkalinity measurements were collected between January 1996 and December 2000 at 10°30′N, 64°40′W as part of the CARIACO (CArbon Retention In A Colored Ocean) oceanographic time series. One key objective of CARIACO is to study temporal variability in Total CO₂ (TCO₂) concentrations and CO₂ fugacity (fCO₂) at this tropical coastal wind-driven upwelling site. Between 1996 and 2000, the difference between atmospheric and surface ocean CO₂ concentrations ranged from about − 64.3 to + 62.3 μatm. Physical and biochemical factors, specifically upwelling, temperature, primary production, and TCO₂ concentrations interacted to control temporal variations in fCO₂. Air–sea CO₂ fluxes were typically depressed (0 to + 10 mmol C m^{− 2} day^{− 1}) in the first few months of the year during upwelling. Fluxes were higher during June–November (+ 10 to 20 mmol C m^{− 2} day^{− 1}). Fluxes were generally independent of the slight changes in salinity normally seen at the station, but low positive flux values were seen in the second half of 1999 during a period of anomalously heavy rains and land-derived runoff. During the 5 years of monthly data examined, only two episodes of negative air–sea CO₂ flux were observed. These occurred during short but intense upwelling events in March 1997 (−10 mmol C m^{− 2} day^{− 1}) and March 1998 (− 50 mmol C m^{− 2} day^{− 1}). Therefore, the Cariaco Basin generally acted as a source of CO₂ to the atmosphere in spite of primary productivity in excess of between 300 and 600 g C m^{− 2} year^{− 1}.  相似文献   

Tidal time-scale variation in nutrient flux across the sediment–water interface of an estuarine tidal flat     

Takashi Sakamaki  Osamu Nishimura  Ruichi Sudo 《Estuarine, Coastal and Shelf Science》2006,67(4):653-663

We determined the range of the tidal variations in nutrient flux across the sediment–water interface and elucidated mechanisms of the flux variation in two estuarine intertidal flats (one sand, one mud) in northeastern Japan. Nutrient flux was measured using in situ light and dark chambers, which were incubated for 2 h, 2–6 times per day. Results showed that nutrient concentration in overlying water varied by tide and was also affected by sewage-treated water inflow. The nutrient fluxes responded quickly to the tidal variation in overlying water chemistry and the range of the variation in flux was as large as the seasonal-scale variation reported in previous studies. In the sand flat, salinity increase likely enhanced benthos respiration and led to increases in both O₂ consumption and PO₄³⁻ regeneration under low illumination, while benthic microalgae were likely to actively generate O₂, uptake PO₄³⁻ and suppress PO₄³⁻ release under high illumination (>900 μmol photons m⁻² s⁻¹). Also in the mud flat, PO₄³⁻ flux was related with O₂ flux, although the range of temporal variation in PO₄³⁻ flux was small. In both the flats, NH₄⁺ flux was always governed by NH₄⁺ concentration in the overlying water; either an increase in NH₄⁺ uptake or a decrease in NH₄⁺ release was observed as the NH₄⁺ concentration rose due to inflow of river water or input of sewage-treated water. Although NO₃⁻ tended to be released in both tidal flats when low NO₃⁻ concentration seawater dominated, their relationship was likely to be weakened under conditions of low oxygen consumption and suppressed denitrification. It is likely that tidal variation in nutrient flux is governed more by the nutrient concentration than other factors, such as benthic biological processes, particularly in the case where nutrient concentration in the overlying water is relatively high and with wide amplitude.  相似文献   

Elemental mercury concentrations and formation rates in the Scheldt estuary and the North Sea     

W. Baeyens  M. Leermakers 《Marine Chemistry》1998,60(3-4)

Concentrations of Hg⁰ in surface waters and atmosphere of the Scheldt estuary and the North Sea are presented and their relationship with biological processes is discussed. Hg⁰ concentrations in the Scheldt estuary range from 0.1 to 0.38 pmol·l⁻¹ in the winter and from 0.24 to 0.65 pmol·l⁻¹ in the summer and show a positive relationship with phytoplankton pigments. In the North Sea Hg⁰ concentrations range from 0.06 to 0.8 pmol·l⁻¹ and are higher in coastal stations. Transfer velocities across the air–sea interface were calculated using a classical shear turbulence model. Volatilization fluxes of Hg⁰ were calculated for the Scheldt estuary and the North Sea. For the Scheldt estuary the fluxes range from 226–284 pmol·m⁻²·d⁻¹ in winter and 500–701 pmol·m⁻²·d⁻¹ in summer and for the North Sea the fluxes range from 59–1110 pmol·m⁻²·d⁻¹ for an average windspeed of 8.1 m·s⁻¹. These fluxes are comparable to the wet and dry depositional fluxes to the North Sea. Hg⁰ formation rates necessary to balance the volatilization fluxes vary from 0.2 to 4% d⁻¹.  相似文献   

Effects of tributyltin (TBT) exposure on the reproduction and embryonic development of the bivalve Scrobicularia plana     

J. M. Ruiz  G. W. Bryan  G. D. Wigham  P. E. Gibbs 《Marine environmental research》1995,40(4)

Field and laboratory work was carried out during the summers of 1990 and 1991 on bivalves Scrobicularia plana from sites moderately-affected and relatively-unaffected by tributyltin (TBT) contamination (i.e. a mean concentration in clam tissues of 0.4 and 0.02 μg Sn g⁻¹ dry wt, respectively). Standard cultures after artificial fertilizations with broodstock of either site did not result in dissimilar survival of embryos nor in larvae of different quality at the time of hatching. Static 48 h toxicity tests on S. plana embryos showed that an EC₅₀ of less than the nominal 250 ng Sn litre⁻¹ (a range of 178–198 ng Sn litre⁻¹, as analysed) can be set for TBT independently of the origin of broodstock. The results are discussed in relation to the reported disappearance of S. plana throughout northern Europe and the simultaneous presence of toxic levels of butyltin. It is concluded that TBT has probably reduced the recruitment into some UK clam populations by preventing the successful development of a significant proportion of their embryos.  相似文献   

Diffusion coefficients of major ions in seawater     

A. Poisson  A. Papaud 《Marine Chemistry》1983,13(4):265-280

Self-diffusion coefficients of five major ions have been determined by a radioactive tracer method (capillary tube method) in seawater of salinity 34.86 at 25°C. Data are presented for Na⁺, Ca²⁺, Cl⁻, SO₄², and HCO₃⁻, which constitute about 95% by weight of sea salt. The influence of temperature and salinity on these coefficients has been studied for Na⁺ and Cl⁻ which are the major components of sea salt: self-diffusion coefficients of these two ions have been measured in seawater, at different temperatures for a salinity of 34.86 and at different salinities for a temperature of 25°C. Diffusion coefficients of the same ions have been determined at 25°C by using another radioactive tracer method (quasi-steady cell method). In this experiment, seawater ions were allowed to diffuse from natural seawater into dilute seawater. Data have been obtained at 25°C for Na⁺, Ca ²⁺, Cl⁻, SO₄²⁻ and HCO₃⁻, corresponding to different salinity gradients.  相似文献   

Activity Concentrations and Fluxes of Radiocesium in the Southern Baltic Sea     

D. Knapinska-Skiba  R. Bojanowski  Z. Radecki  G. E. Millward 《Estuarine, Coastal and Shelf Science》2001,53(6):779

The activity concentrations of dissolved¹³⁷Cs have been determined in the water column and¹³⁷Cs and¹³⁴Cs in the sediments and the sediment porewaters of the southern Baltic Sea. The mean activity concentration of dissolved¹³⁷Cs in the Gdansk Deep declined from 109 Bq m⁻³in June 1986 to 61 Bq m⁻³in 1999. In sediments, the activity concentrations of¹³⁷Cs (33-231 Bq kg⁻¹) were highest in muds and the activity concentrations of¹³⁴Cs were about 6% of the total Cs activity. The Chernobyl contribution to¹³⁷Cs activity was between 43% and 77%. The porewater activity concentrations of¹³⁷Cs in muddy sediments were in the range 71 to 3900 Bq m⁻³and were higher than those in the overlying seawater. The diffusive flux of dissolved¹³⁷Cs from the muddy sediments was estimated in the range 5 to 480 Bq m⁻²year⁻¹. The flux of¹³⁷Cs from sediment porewaters of the southern Baltic Sea was about 45% of the total, including fluxes of¹³⁷Cs from wet and dry atmospheric deposition and the fluvial inputs. The results were used to elucidate the rate of recovery of the sediments and the waters of the southern Baltic from Chernobyl-derived¹³⁷Cs.  相似文献   

Photo-oxidation of dimethylsulphide in aqueous solution   总被引：2，自引：0，他引：2  

Peter Brimblecombe  David Shooter   《Marine Chemistry》1986,19(4)

Dimethylsulphide (DMS) is readily photo-oxygenated in the presence of micromolar amounts of photosensitizers such as methylene blue, rose bengal, anthroquinone and humic acid. Two moles of DMS are oxidized for every mole of molecular oxygen utilized consistent with dimethyl-sulphoxide being the oxidation product. Coastal seawater samples examined contained sufficient naturally occurring photosensitizer to photo-oxygenate DMS in sunlight with a first order rate constant of 2.4 × 10⁻⁵ s⁻¹. This rate is rapid enough to imply that DMS is oxidized at approximately the same rate as it is lost to the atmosphere.  相似文献   

Measurement of manganese, zinc and cadmium complexation in seawater using Chelex ion exchange equilibria     

William G. Sunda 《Marine Chemistry》1984,14(4):365-378

Equilibria between Chelex 100* and manganese, zinc and cadmium ions were used to determine the complexation of these trace metals in 36‰ Gulf Stream seawater at 25°C and pH 8.2. The method utilized radiotracers (⁵⁴Mn, ⁶⁵Zn, and ¹⁰⁹Cd) to quantify trace metal adsorption from trace metal-amended seawater and from seawater containing a series of ethylenediaminetetracetate (EDTA)—metal ion buffers. Results were consistent with Chelex adsorption of both trace metal ions and trace metal—EDTA chelates. Equilibrium models fitted to the data were used to establish conditional stability constants for Chelex adsorption of manganese, zinc and cadmium ions and for adsorption of EDTA-chelates. These models also yielded ratios of free metal ions to total dissolved trace metal concentrations in seawater: 10^−0.1 for manganese, 10^−0.2 for zinc, and 10^−1.5 for cadmium. Independent measurements with a cadmium ion-selective electrode also yielded a free: total cadmium ratio of 10^−1.5.  相似文献   

Cadmium and phosphate in coastal Antarctic seawater: Implications for Southern Ocean nutrient cycling     

Katharine R. Hendry  Rosalind E.M. Rickaby  Jan C.M. de Hoog  Keith Weston  Mark Rehkmper 《Marine Chemistry》2008,112(3-4):149-157

Cadmium is a biologically important trace metal that co-varies with phosphate (PO₄³⁻ or Dissolved Inorganic Phosphate, DIP) in seawater. However, the exact nature of Cd uptake mechanisms and the relationship with phosphate and other nutrients in global oceans remain elusive. Here, we present a time series study of Cd and PO₄³⁻ from coastal Antarctic seawater, showing that Cd co-varies with macronutrients during times of high biological activity even under nutrient and trace metal replete conditions. Our data imply that Cd/PO₄³⁻ in coastal surface Antarctic seawater is higher than open ocean areas. Furthermore, the sinking of some proportion of this high Cd/PO₄³⁻ water into Antarctic Bottom Water, followed by mixing into Circumpolar Deep Water, impacts Southern Ocean preformed nutrient and trace metal composition. A simple model of endmember water mass mixing with a particle fractionation of Cd/P (α_Cd–P) determined by the local environment can be used to account for the Cd/PO₄³⁻ relationship in different parts of the ocean. The high Cd/PO₄³⁻ of the coastal water is a consequence of two factors: the high input from terrestrial and continental shelf sediments and changes in biological fractionation with respect to P during uptake of Cd in regions of high Fe and Zn. This implies that the Cd/PO₄³⁻ ratio of the Southern Ocean will vary on glacial–interglacial timescales as the proportion of deep water originating on the continental shelves of the Weddell Sea is reduced during glaciations because the ice shelf is pinned at the edge of the continental shelf. There could also be variations in biological fractionation of Cd/P in the surface waters of the Southern Ocean on these timescales as a result of changes in atmospheric inputs of trace metals. Further variations in the relationship between Cd and PO₄³⁻ in seawater arise from changes in population structure and community requirements for macro- and micronutrients.  相似文献   

Polycyclic aromatic hydrocarbons in surface seawater and in indigenous mussels (Mytilus galloprovincialis) from coastal areas of the Saronikos Gulf (Greece)   总被引：1，自引：0，他引：1  

A. Valavanidis  Th. Vlachogianni  S. Triantafillaki  M. Dassenakis  F. Androutsos  M. Scoullos 《Estuarine, Coastal and Shelf Science》2008,79(4):733-739

Polycyclic aromatic hydrocarbons (PAHs) were identified and measured in surface seawater and in the tissues (gills and mantle) of indigenous black mussels, Mytilus galloprovincialis, collected from three coastal sites of Saronikos Gulf (Greece), a gulf that exhibits high levels of pollution. The total PAHs measured by spectrofluorometry in the surface seawater were found in the range of 425–459 ng L⁻¹ at the most polluted sites 1 and 2 (Elefsis Bay–Salamis Island) and in the range of 103–124 ng L⁻¹ at site 3 (Aegina Island). PAHs' sources in seawater were identified by application of specific PAH ratios, such as phenanthrene/anthracene and fluoranthene/pyrene. Levels of PAHs in soft tissues (gills and mantle) of indigenous mussels were much higher than those reported for seawater. Total PAH concentrations in mantle tissues were in the range of 1300–1800 ng g⁻¹ dry weight (dw) tissue at sites 1 and 2 and approximately 380 ng g⁻¹ dw at site 3. In gill tissues total PAH concentrations were in the range of 1480–2400 ng g⁻¹ dw at sites 1 and 2 and approximately 430 ng g⁻¹ dw at site 3. PAHs composition was dominated by two-, three- and four-ring compounds in seawater, where 17 different PAH compounds were identified and measured in mussel tissues. Mussels can be used as sentinel organisms to monitoring PAHs' contamination, since they concentrate PAHs from the surrounding water media and therefore making the chemical analysis simpler and less prone to error than that for water. In surface seawater possible weathering and photodegradation due to hot climates contribute to reduced PAHs concentrations.  相似文献   

The capacity of marine plankton, macrophytes and particulate matter to adsorb Cu in the presence of Mg     

Carlton D. Hunt  William F. Fitzgerald 《Marine Chemistry》1983,12(4)

A complexometric titration technique was employed to measure the total capacity of a variety of marine organisms to adsorb Cu²⁺. Measured adsorption capacities were 0.22 meq g⁻¹ for phytoplankton, 0.3–1.0 meq g⁻¹ for macrophytes, 1.0–2.5 meq g⁻¹ for zooplankton and 0.3 meq g⁻¹ for suspended particulate matter. The capacity of these materials to adsorb Cu²⁺ was reduced significantly in the presence of Mg²⁺ at seawater concentrations. Competition between Mg^t2+ and Cu²⁺ for adsorption sites at pH 6 is described by an average conditional equilibrium constant of 10^3.7. This constant is such that very little Cu²⁺ may be adsorbed onto particulates and marine phytoplankton in the presence of Mg²⁺. Further, primary productivity data and estimates of the detrital carbon sedimentation in Long Island Sound suggest that the flux of particulate carbon is insufficient to remove significant amounts of Cu from the water column to sediments by adsorption mechanisms.  相似文献   

Submarine groundwater discharge: A large, previously unrecognized source of dissolved iron to the South Atlantic Ocean   总被引：4，自引：5，他引：4  

Herbert L. Windom  Willard S. Moore  L. Felipe H. Niencheski  Richard A. Jahnke   《Marine Chemistry》2006,102(3-4):252-266

This paper reports the initial results of a study of groundwater and coastal waters of southern Brazil adjacent to a 240 km barrier spit separating the Patos Lagoon, the largest coastal lagoon in South America, from the South Atlantic Ocean. The objective of this research is to assess the chemical alteration of freshwater and freshwater–seawater mixtures advecting through coastal permeable sands, and the influence of the submarine discharge of these fluids (SGD) on the chemistry of coastal waters. Here we focus on dissolved iron in this system and use radium isotopic tracers to quantify SGD and cross-shelf fluxes. Iron concentrations in groundwaters vary between 0.6 and 180 μM. The influence of the submarine discharge of these fluids into the surf zone produces dissolved Fe concentrations as high as several micromolar in coastal surface waters. The offshore gradient of dissolved Fe, coupled with results for Ra isotopes, is used to quantify the SGD flux of dissolved Fe from this coastline. We estimate the SGD flux to be 2 × 10⁶ mol day^− 1 and the cross-shelf flux to be 3.2 × 10⁵ mol day^− 1. This latter flux is equal to about 10% of the soluble atmospheric Fe flux to the entire South Atlantic Ocean. We speculate on the importance of this previously unrecognized iron input to regional ocean production and on the potential significance of this source to understanding variations in glacial–interglacial ocean production.  相似文献   

Meridional carbon dioxide transport in the northern North Atlantic     

M. H. C. Stoll  H. M. van Aken  H. J. W. de Baar  C. J. de Boer 《Marine Chemistry》1996,55(3-4)

Combination of estimated water transport and accurate measurements of total carbon dioxide (TCO₂) on a hydrographic section at 58 °N allows the assessment of meridional inorganic carbon transport in the northern North Atlantic Ocean. The transport has been decomposed into contributions from the large-scale baroclinic overturning, the Ekman transport, baroclinic and a barotropic eddy terms, and an estimated contribution of the East Greenland Current. These terms are −0.27 · 10⁶, +0.03 · 10⁶, +0.03 · 10⁶, +0.10 · 10⁶, and +0.05 · 10⁶ mol s⁻¹, respectively, which result in a total southward inorganic carbon transport of only −0.06 · 10⁶ mol s⁻¹. An order of magnitude estimate of the meridional transport of dissolved organic carbon (DOC) has shown that in general this term cannot be ignored in the total carbon flux, this being +0.04 · 10⁶ to +0.16 · 10⁶ mol s⁻¹ at 58 °N. A simple carbon budget has been formulated for the temperate North Atlantic, using our flux estimates as well as those of Brewer et al. (1989). This budget shows that the divergence of the meridional carbon flux, connected with the freshwater balance of the ocean may be of the same order of magnitude as the divergence of the total inorganic carbon flux. For an accurate estimate of the total carbon budget of the ocean it will be necessary to take both the DOC transport and the effects of the freshwater balance into account.  相似文献   

Winkler's method overestimates dissolved oxygen in seawater: Iodate interference and its oceanographic implications     

George T.F. Wong  Kuo-Yuan Li 《Marine Chemistry》2009,115(1-2):86-91

Dissolved oxygen in seawater has been determined by using the Winkler's reaction scheme for decades. An interference in this reaction scheme that has been heretofore overlooked is the presence of naturally occurring iodate in seawater. Each mole of iodate can result in an apparent presence of 1.5 mol of dissolved oxygen. At the concentrations of iodate in the surface and deep open ocean, it can lead to an overestimation of 0.52 ± 0.15 and 0.63 ± 0.05 μmol kg^− 1 of oxygen in these waters respectively. In coastal and inshore waters, the effect is less predictable as the concentration of iodate is more variable. The solubility of oxygen in seawater was likely overestimated in data sources that were based on the Winkler's reaction scheme for the determination of oxygen. The solubility equation of García and Gordon [Garcia H.E., Gordon, L.I., 1992. Oxygen solubility in seawater: Better fitting equations. Limnol. Oceanogr. 37, 1307–1312] derived from the results of Benson and Krause [Benson, F.B., Krause, D. Jr., 1984. The concentration and isotopic fractionation of oxygen dissolved in freshwater and seawater in equilibrium with the atmosphere. Limnol. Oceanogr. 29, 620–632] is free from this source of error and is recommended for general use. By neglecting the presence of iodate, the average global super-saturation of oxygen in the surface oceans and the corresponding efflux of oxygen to the atmosphere both have been overestimated by about 8%. Regionally, in areas where the degree of super-saturation or under-saturation of oxygen in the surface water is small, such as in the tropical oceans, the net air–sea exchange flux can be grossly under- or overestimated. Even the estimated direction of the exchange can be reversed. Furthermore, the presence of iodate can lead to an overestimation of the saturation anomaly of oxygen in the upper ocean attributed to biological production by 0.23 ± 0.07%. AOU may have been underestimated by 0.52 ± 0.15 and 0.63 ± 0.05 μmol kg^− 1 in the surface mixed layer and deep water, while preformed phosphate and preformed nitrate may have been overestimated by 0.004 ± 0.001 and 0.06 ± 0.02 μmol kg^− 1 in the surface mixed layer, and 0.005 ± 0.0004 and 0.073 ± 0.006 μmol kg^− 1 in the deep water. These are small but not negligible corrections, especially in areas where the values of these parameters are small. At the increasing level of sophistication in the interpretation of oxygen data, this source of error should now be taken into account. Nevertheless, in order to avoid confusion, an internationally accepted standard needs to be adopted before these corrections can be applied.  相似文献