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1.
Stoichiometry among bioactive trace metals in the Chukchi and Beaufort Seas   总被引：1，自引：1，他引：0  
The distribution of Al, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb in seawater was investigated in the Chukchi and Beaufort Seas of the western Arctic Ocean in September 2000. The unfiltered and filtered seawater samples were used for determination of total dissolvable metal (TDM) and dissolved metal (DM), respectively. The concentration of labile particulate metal (LPM) was estimated with the difference between that of TDM and DM. The concentrations of TDAl, TDMn, TDFe, TDCo and TDPb varied substantially in the study area. The high concentrations occurred at stations near the Bering Strait, in the Mackenzie delta, and above reductive sediments on the shelf and slope. These elements were mostly dominated by labile particulate species, such as Fe?CMn oxides and species adsorbed on terrestrial clay. DCo was correlated with DMn over the study area (r?=?0.78, n?=?135), and the slope of the regression line was 27 times higher at a pelagic station than at a shelf station. TDNi, TDCu, TDZn and TDCd showed relatively small variations and were generally dominated by dissolved species. There was a moderate correlation between DCd and phosphate for all samples (r?=?0.79), whereas there were no significant correlation between the other DMs and nutrients. TDNi and TDCu showed a remarkable linearity for most stations except those near the Bering Strait (R 2?=?0.95, n?=?126). These results suggest that biogeochemical cycling including uptake by phytoplankton and remineralization from settling particles has only minor control over the distribution of trace metals in this area. Using the present data, the annual input of bioactive trace metals form the Bering Strait and the Mackenzie River was estimated. Also, the trace metal compositions of major water masses were evaluated. The dissolved elemental ratio was P:Al:Mn:Fe:Co:Ni:Cu:Zn:Cd?=?1:1.2?×?10?2:4.4?×?10?4:1.4?×?10?3:3.7?×?10?5:3.7?×?10?3:1.4?×?10?3:4.5?×?10?3:2.2?×?10?4 for Canada Basin deep water (CBDW). This ratio was significantly different from that for Pacific deep water and Bering Sea water, suggesting substantial modification of the trace metal compositions of seawater in the study area.  相似文献   

2.
Abstract

Nitrogen fixing potential was measured in summer 1975 by acetylene reduction in situ at 5 stations on the intertidal flats of the Waimea Inlet, Nelson, New Zealand, which receive nutrients from several sources. Highest values (644 μmol?m?2.d?1) were obtained on sediments near an apple cannery effluent discharge and were linear through at least two tidal cycles. The cannery waste had the highest carbon to nitrogen ratio (10.3 : 1.0) of all the effluents examined and exhibited the highest rate of acetylene reduction (14.0 μmol?‐l?1.d?1). Sizeable populations of the nitrogen fixing bacteria Klebsiella pneumoniae were isolated from the cannery effluent (2 × 104 per millilitre) and also from the mud adjacent to the discharge pipe (5 × 105 per millilitrc). The stimulatory effect of the cannery effluent on nitrogen fixation in the sediment was shown to be restricted to close to the discharge point. Sediments in areas affected by slaughterhouse and sewage effluents exhibited the second and third highest rates of acetylene reduction, (130 &; 28 μmol?m?2.d?1 respectively). In both places, the activities were not restricted to the immediate vicinity of the effluent channels. Nitrogen fixation was lowest in sediments fronting a catchment of grazed pasture. Fixation was low also in sediments affected by effluents from the hydraulic debarker of a woodchip mill.  相似文献   

3.
To accurately characterize sound speed dispersion of shallow sediments in the Southern Yellow Sea, three types of sediments, i.e., silt, clayey silt, and silty clay, were selected to measure the sound speeds at 25–250?kHz. Over the frequency range, the sound speeds vary approximately from 1,536 to 1,565?m?s?1 in silt sediment, from 1,511 to 1,527?m?s?1 in clayey silt sediment, and from 1,456 to 1,466?m?s?1 in silty clay sediment. The sound speed exhibits a slow increase with frequency in a nearly linear gradient, but these three types of sediments have different sound speed dispersion characteristics. The silt sediment with relatively coarse grains has the most significant sound speed dispersion, while the sound speed dispersions of the two others are relatively weak. Comparison between the measured dispersions and the model predictions shows that the grain-shearing model can match the measured data at most of frequencies. Nevertheless, when the grain bulk modulus was assigned 3.2?×?1010?Pa according to relevant references, the Biot–Stoll model predictions were higher than the measured values at high frequencies; when it was assigned a relatively small value of 2.8?×?1010?Pa, the model predictions achieved optimal matching with the measured values.  相似文献   

4.
Channel constrictions within an estuary can influence overall estuary-sea exchange of salt or suspended/dissolved material. The exchange is modulated by turbulent mixing through its effect on density stratification. Here we quantify turbulent mixing in Hikapu Reach, an estuarine channel in the Marlborough Sounds, New Zealand. The focus is on a period of relatively low freshwater input but where density stratification still persists throughout the tidal cycle, although the strength of stratification and its vertical structure vary substantially. The density stratification increases through the ebb tide, and decreases through the flood tide. During the spring tides observed here, ebb tidal flow speeds reached 0.7?m?s?1 and the buoyancy frequency squared was in the range 10?5 to 10?3?s?2. Turbulence parameters were estimated using both shear microstructure and velocimeter-derived inertial dissipation which compared favourably. The rate of dissipation of turbulent kinetic energy reached 1?×?10?6?m2?s?3 late in the ebb tide, and estimates of the gradient Richardson number (the ratio of stability to shear) fell as low as 0.1 (i.e. unstable) although the results show that bottom-boundary driven turbulence can dominate for periods. The implication, based on scaling, is that the mixing within the channel does not homogenise the water column within a tidal cycle. Scaling, developed to characterise the tidal advection relative to the channel length, shows how riverine-driven buoyancy fluxes can pass through the tidal channel section and the stratification can remain partially intact.  相似文献   

5.
Recent studies have suggested that poikilothermic animals, such as fish, may represent a previously overlooked source of the faecal indicator bacteria (FIB) used for the assessment of water quality. However, quantitative studies of FIB in poikilotherms are scarce. We investigated the presence of FIB in the faeces of five freshwater fish species. E. coli and enterococci were detected in 71 and 76% of faecal samples, respectively. Concentrations were highly variable, with maximum concentrations (2.1?×?104 E. coli and 1.3?×?106 enterococci per gram of faecal material) up to four orders of magnitude higher than present in the water column. FIB were not detected in faecal samples from marine fish. Our findings suggest that FIB ingested from the environment may be capable of replication within the fish gut, making fish a potential source and transport mechanism for FIB in New Zealand freshwaters. This may have implications for water quality monitoring.  相似文献   

6.
The MnO2 adsorption method combined with voltammetry is proposed for the direct determination of metal complexation in seawater of various salinities as a more satisfactory alternative to direct voltammetric measurements and bioassay methods. A small quantity of MnO2 is equilibrated with copper ions in filtered seawater. Natural organic ligands in the seawater compete for copper with the MnO2. Total dissolved copper is measured by differential pulse anodic stripping voltammetry after filtration and acidification of the sample. Preconcentration of natural water samples is unnecessary and measurement is performed at the natural equilibrium pH of the aerated sample. The analytical limit of detection of the method depends on contamination from the filtration step, and for copper complexation a ligand concentration of 5 × 10?8 M was obtained. The sensitivity can be increased by use of radioisotopes as tracers. The method is very versatile in that complexation of various metals may be determined by any analytical method that measures total dissolved metal concentrations. Neither organic ligands nor their complexes with copper adsorb on the MnO2 at pH8, but at pH 1.8 MnO2 is an efficient scavenger for electroactive organic material.Samples of surface water from the Irish Sea and the Atlantic Ocean were found to contain ligand concentrations of 1.7 × 10?7 and 1.1 × 10?7 M, with conditional stability constants (log values) of 9.84 ± 0.13 and 9.86 ± 0.23, respectively, at pH 8.0.  相似文献   

7.
Hydration, ion-water interactions, and water structure effects in seawater were studied by determining differences (Δβ) between the compressibilities of test salt solutions and the compressibilities of reference solutions. The reference solutions were distilled water and seawater (35%0), and the test salt solutions were either 0.13 m or 0.26m with respect to one of the following test salts: LiCl, NaCl, KCl, CsCl, NaF, NaI, MgCl2, CaCl2, BaCl2, Na2SO4, K2SO4, and MgSO4. The compressibility measurements (to 900 bars) were carried out at 2°C and also at 15°C using a differential method in which a pressure increase or a temperature increase causes Δβ to become less negative. At 1 bar and 15°C, the Δβ (0.26 m, distilled water reference) values ranged from ?1.14 × 10?6 bar? for NaI to ?3.84 × 10?6 bar?1 for Na2SO4, and the Δβ (0.26 m, seawater reference) values ranged from ?1.30 × 10?6 bar?1 for NaCl to ?3.04 × 10?6 bar?1 for Na2SO4. The Δβ values were used to calculate hydration numbers. Entropy of transfer, excess hydrogen bond breaking (determined by NMR), and effective radii of ions are properties which can be used to describe the influence of ions on water structure. The extent to which these properties correlate with Δβ values depends upon whether the ion is an anion or a cation, and this correlation forms the thesis that anions alter water structure in a different way than do cations.  相似文献   

8.
A case study was carried out in 2000 in the shallow coastal area of the Northern Adriatic Sea (Gulf of Trieste) where untreated domestic sewage and industrial wastes are discharged at rate of 5500 m3·day?1. The sewage plume above the outfall was followed using faecal coliforms (FC) and overturning length scale (lT). The latter was rejected as a marker as the discharge conditions prohibit following the turbulence of sewage water. Intermittent sewage discharge is reflected in the minimal effect of eutrophication. Increase of phytoplankton biomass is thus only minor compared with the unpolluted area regardless of elevated concentrations of sewage‐derived nutrients (confirmed by correlation coefficients between FC and NH4+, TP, PO43?: 0.78, 0.71 and 0.67, respectively). Deteriorated trophic status, determined by the TRIX index, was observed only in the surface layer (average TRIX: 5.67). High FC content well above the regulation limit (up to 2.6 × 105 FC·100 ml?1) represents, therefore, the major negative impact of the improperly treated waste for the risk to human health.  相似文献   

9.
Large amounts of sediments are dredged annually from Chinese oceans. Dredged materials (DMs) possess poor geotechnical properties and are normally treated as waste. This paper presents the first large-scale engineering application of DM solidification treatment in China. The technique has been used to treat approximately 1.8?×?106?m3 of DM from Taihu Lake to produce fill soils. Portland cement was chosen as the solidification material, the amount of which is confirmed through indoor unconfined compressive strength (UCS) tests. Special solidification machines process DM at 120?m3/hours. Field-based DM solidification engineering began in September 2006. Curing specimens were examined over 28 days. Results show that both UCS and failure strain of solidified DM could meet fill soil requirements. Bearing capacity was also assessed with a cone penetrometer test. Samples were examined after 2 years (after project completion), and the mean UCS of the specimens was 237.2?kPa, which completely satisfied the engineering request. Wuxi Taihu City Science and Technology Industrial Park has now been established on top of the solidified DM storage yard. The successful engineering of such facilities results in economic and environmental benefits; thus, engineering applications of DM solidification treatment are widely promoted in China.  相似文献   

10.
The extent and kinetics of Np(V)O2+ adsorption from dilute aqueous solutions and seawater onto a variety of synthetic and natural solids were determined at 25°C and 1 atm total pressure. Extensive and complex adsorption reactions were found, contrary to speculations in the literature that NpO2+ should behave as a simple monovalent ion with a low affinity for surfaces. When normalized to adsorption per unit solid surface area, the ranking for the synthetic solids was aragonite ? calcite > goethite ? MnO2 ≈ clays. Natural materials generally followed the same behavior patterns as their synthetic counterparts. The dissolved/adsorbed ratio was found to be constant over a wide range (10?13–10?7M) of NpO2+ concentrations. At higher concentrations the extent of adsorption decreased until a solubility limit was reached at approximately 10?5 M.Solution composition had the most significant influence for NpO2+ adsorption on goethite, where much more extensive adsorption occurs in dilute solutions than in seawater. When seawater is added to a dilute solution, extensive desorption of NpO2+ from goethite occurs. Tests conducted on NpO2+ adsorbed on carbonates indicated that it remained in the V oxidation state.There is a growing consensus that Pu dissolved in natural waters also occurs dominantly in the V oxidation state as PuO2+ ion. Consequently, these results for NpO2+ may serve as a guide for Pu behavior when also in the V oxidation state. The fact that most adsorbed Pu is found in the III or IV oxidation states indicates that reduction of Pu may occur subsequent to adsorption in the V oxidation state.  相似文献   

11.
A sediment budget for the Choptank River, one of the three largest estuaries on the eastern shore of Chesapeake Bay, was developed from measurements of sediment carried in upland runoff, shore erosion, sedimentation, and levels of suspended sediments in estuarine waters. Shore erosion was the major source of sediment (340 × 106 kg y?1), contributing seven times more sediment than upland runoff. Low relief, the rural character of the Coastal Plain drainage basin, and the susceptibility of poorly consolidated shoreline materials to erosion contributed to the dominance of shore erosion over runoff as a sediment source. Box modelling indicated a net annual flux (14–44 × 106 kg y?1) of sediment from the Choptank River to Chesapeake Bay. A mass balance estimate of sedimentation, calculated as the difference between total inputs and loss at the mouth of the estuary, (350 × 106 kg y?1) agreed well with an estimate based on 210Pb profiles (340 × 106 kg y?1) measured along the longitudinal axis of the estuary. Lead-210 sedimentation rates correspond to accumulation rates of 1·5–7·9 mm y?1.  相似文献   

12.
A novel technique to determine complexing capacities for zinc is presented. The free zinc concentration is determined by cathodic stripping voltammetry preceded by adsorptive collection of complexes of zinc with ammonium pyrrolidine dithiocarbamate (APDC). The reduction peak of zinc is depressed as a result of ligand competition by natural organic material in the sample. Sufficient time is allowed to reach equilibrium between this material and added APDC, and equilibrium is maintained during the measurement. Both electrochemically reversible and irreversible complexes can therefore be investigated. Values for KZnAPDC′ are calibrated against NTA and EDTA in seawater of several salinities; log KZnAPDC′ was found to be 4.40 at 36‰, 4.36 at 24‰, 4.43 at 12‰, and 4.87 at 2.3‰. The ligand concentration and conditional stability constant, KZnL′, for complexing ligands in a sample from the Irish Sea were determined in the presence of 4 × 10?5 M APDC and with added zinc concentrations between 5 × 10?9 and 3 × 10?7 M. The data best fitted a complexation model containing two ligands with concentrations of 2.6 and 6.2 and 10?8 M, and with values for log KZnL′ of 8.4 and 7.5, respectively. These results are comparable to those obtained with other equilibrium techniques, but the values of the constants are greater than those from ASV measurements.  相似文献   

13.
It is shown that the values of the diffusion coefficient of MgSO40 ion pairs computed by Harned and Hudson (J. Am. Chem. Soc., 73: 5880, 1951) and Katz and Ben-Yaakov (Mar. Chem., 8: 263, 1980) are too high by a factor of 2. The correct value of the ion pair diffusion coefficient at infinite dilution was obtained from the measured mutual diffusion coefficient after applying corrections for incomplete dissociation, the electrophoretic effect, the viscosity of the solution and the effect of chloride ion pairs (in the ionic media used during measurements of the stoichiometric association constant of MgSO40 ion pairs). The MgSO40 diffusion coefficient is calculated to be 0.65 × 10?5 cm28?1. The result is independent of the concentration up to a value of 0.8 mol dm?3.Values were also calculated for the diffusion coefficients of the following ion pairs: NaSO4? (0.81 × 10?5), CaCl+ (0.78 × 10?5), BaCl+ (0.85 × 10?5), NaCl0 (0.86 × 10?5), KCl0 (1.09 × 10?5), NH4Cl0 (1.10 × 10?5) and CaCl0 (1.27 × 10?5). In general, the diffusion coefficients are less than those of the free ions. The results show quantitative agreement with theoretical predictions.  相似文献   

14.
The concentration of hydrogen peroxide was measured in waters off the coast of Peru during June and July 1983. The study period coincided with the end of the 1982/83 El Niño and the onset of coastal upwelling. Depth profiles of hydrogen peroxide concentration exhibit surface maxima and decrease with depth to the base of the mixed layer. Surface peroxide concentrations ranged from 0.8 to 5 × 10?8 M. Below the mixed layer hydrogen peroxide was below the detection limit (5 × 10?9 M). Diel variations were observed, with surface peroxide levels increasing during the day and decreasing at night. The nearshore station exhibited lower hydrogen peroxide concentrations than offshore stations, a reversal of the trend found in other coastal regions. This is attributed to the lack of coastal vegetation and runoff, and to active coastal upwelling of deeper water with low hydrogen peroxide concentrations.  相似文献   

15.
Abstract

This study investigated the penetrability of high volume fly ash cement suspensions prepared with and without superplasticizer into sandy soil having different relative densities with 30%, 60%, 73%, and 83% through permeation grouting. Class C fly ash was used due to its pozzolanic activity and fineness. Due to engineering characteristics and cost, cementitious grouts are the most commonly used grout in both waterproofing and ground strengthening. Fly ash-cement grouts have relatively constant and low viscosity values for a reasonable period after preparation, exhibit limited or negligible bleed capacity and set and develop satisfactory strength within a relatively short period. Modeling of grouting of soil was done in laboratory and improvements in physical and mechanical properties of grouted soil were analyzed. Unconfined compressive strength, shear strength and permeability characteristics of grouted soil were studied as a result. Unconfined compressive strength values of grouted sand with high volume fly ash ranged between 410 and 1107?kPa. Morover, cohesion values were comparable to microfine cement grouting ranging from 373 to 511?kPa. Furthermore, permeability values were also approximately equal to the permeability of impervious liners, which is around 1?×?10?7?cm/s. The findings support the applicability of grouting in different applications.  相似文献   

16.
Abstract

Bacterial numbers and production were measured in the upper water column in the winter and spring of 1993 in five water masses surrounding the South Island of New Zealand. Average bacterial numbers and production were found to be higher in spring (8.5 × 105 cells ml?1 and 0.20 mg m3 h?1, respectively) than winter (5.5 × 105 cells ml?1 and 0.05 mg C m3 h?1 respectively). Bacterial production was strongly correlated with chlorophyll a and primary production (P < 0.001) in spring but not in winter. Spring bacterial production and at 10 m depth averaged across 28 stations was 23% of primary production, and with a growth efficency of 40%, may have consumed up to 57% of primary production. Bacterial biomass was greater than phytoplankton biomass for 75% of the 10 m depth comparisons during winter sampling and 44% during the spring sampling. The bacterial biomass was found to represent 24.6–33.5% of the nitrogen in particulate organic matter (<200 μm) supporting the concept that in New Zealand oceanic water masses bacteria are of significant biogeochemical importance.  相似文献   

17.
Box and gravity cores recovered from the Håkon Mosby mud volcano (HMMV) during cruise 15 of the R/V Professor Logachev were analyzed for bacterial activity and benthic fauna distribution. The high bacterium number (up to 9.6×109 cells cm-3 of the sediment) and marked rates of sulfate reduction (up to 0.155?mg?S?dm-3?day-1) and methane oxidation (up to 9.9?μg?C?dm-3?day-1) were shown for the upper horizons of the sediments of the HMMV peripheral zone. The benthic community is characterized by the presence of two pogonophoran species, Oligobrachia sp. and Sclerolinum sp., harboring symbiotic methanotrophic bacteria.  相似文献   

18.
We examined the effects of the presence of larval conspecifics on larval vertical distribution of four‐arm and six‐arm plutei of Strongylocentrotus droebachiensis and bipinnaria of Asterias rubens, in laboratory experiments, by manipulating population density. Larvae were introduced to experimental columns (10 × 10 × 30 cm) at one of two or three population densities (S. droebachiensis: 0.1 and 10 larvae·ml?1; A. rubens: 0.1, 1 and 10 larvae·ml?1). Subsequent changes in vertical distribution were determined from images of the larvae in the columns illuminated by a 532‐nm laser and captured by a high‐resolution camera. Larvae of both species were found higher in the water column in the high than in the low and intermediate population densities. The relationship between vertical swimming velocity and nearest neighbour distance (NND) was measured for four‐arm plutei of S. droebachiensis, and used to determine a range in distances among individuals that may affect potential interactions. The variation in swimming velocity decreased with increasing proximity below a threshold distance among individuals of 10 mm, which was greater than the estimated distance in the high population density. We suggest that the increased larval aggregation near the water surface under high population density is the result of a behavioural response to conspecifics.  相似文献   

19.
Methane fluxes in the southeastern Baltic Sea   总被引：2，自引：2，他引：0  
New data from surveys of gas-bearing mud areas in the Gdansk Deep (southeastern Baltic Sea) were collected during four research cruises in 2009–2011. These revealed the presence of seven large pockmarks apart from the three already known, and enabled significant improvement of the existing digital map of gassy mud distribution. Based on geochemical sediment analyses, calculated diffusive methane fluxes from the upper (0–5?cm) seabed layer into near-bottom waters were highest—3.3?mmol/(m2?day)—in pockmark mud, contrasting strongly with the minimum value of 0.004?mmol/(m2?day) observed in typical, background mud. However, fluxes of less than 0.1?mmol/(m2?day) were observed in all sediment types, including pockmarks. In a newer attempt to roughly estimate budgets at a more regional scale, diffusive methane venting amounts to 280?×?106?mmol/day for southeastern Baltic Sea muddy sediments. Elongated pockforms in the southern Gotland Deep, known since the end of the 1980s as pockmarks, had methane concentrations that were similar to those of gassy mud from the Gdansk Basin, and there was no geo-acoustic evidence of considerably increased gas levels.  相似文献   

20.
Measurements have been made, by amperometric titration using anodic stripping voltammetry, of the zinc-binding properties of organic material released by Thalassiosira fluviatilis in culture over a period from the beginning of growth to senescence. After the onset of the stationary phase, titration curves showed two inflection points, interpreted as indicating the presence of two analytically distinguishable ligand assemblages (L1 and L2). The complexing capacities (CL) of these assemblages changed with time, CL1 increasing linearly from <0.5 × 10?8 M to 2.0 × 10?6 M into the stationary phase and then more rapidly during senescence, and CL2 increasing after its initial appearance to a final value of 4.4 × 10?6 M. These changes were accompanied by systematic decreases in the corresponding conditional stability constants (K′) calculated for 1 : 1 associations of the ligands with zinc. Values of log K′1 decreased from 6.6 to 5.8, and those of log K′2 from 7.2 to 6.2. The presence of the second ligand assemblage may be related to the release of intracellular material during senescence.  相似文献   

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