A note on the polarographic behavior of the Cu(II) ion selective electrode in seawater

The non-Nernstian behavior of a solid-state cupric ion-selective electrode in seawater is attributed to a reduction of Cu²⁺ at the surface in accordance with a suggestion made in the literature. This ‘polarographic’ behaviour was demonstrated by showing that the electrode potential is affected by molecular oxygen in solution.     

Respiration rates of some New Zealand echinoderms (note)

Respiratory rates were measured in four common New Zealand echinoderms, Evechinus chloroticus and Goniocidaris umbraculum (Echinoidea), and Coscinasterias calamaria and Pentagonaster pulcheilus (Asteroidea). Oxygen uptake was monitored with a polarographic oxygen electrode. The respiratory rates at 12°c ranged from 3.8 to 9.8 μl O_2.h^‐1.g^‐1 (live weight). The rates for Evechinus and Coscinasterias fall well within the range of metabolic rates of other echinoids and asteroids. Goniocidaris and Pentagonaster have relatively low respiratory rates.     

Total thiol redox status as a potent biomarker of PAH-mediated effects on mussels

This laboratory study describes phenanthrene (Ph) and/or anthracene (An) ability to alter the total thiol redox status (TRS), via depletion of protein free thiols (PSH) and glutathione (GSH) levels, in gills of mussel Mytilus galloprovincialis, after a short-term (7 days) exposure period to each contaminant (at a final concentration of 0.1 mg L⁻¹) or in a mixture (ration 1:1, at a final concentration of 0.2 mg L⁻¹). A number of observable changes, like lysosomal membrane impairment (as detected via the neutral red retention time assay, primarily performed in haemocytes), enhancement of lipid peroxidation byproducts, increased nuclear abnormalities, inhibition of AChE and ALP activity, as well as a significant depletion of PSH and GSH were detected in gills of exposed mussels, in any case. Significant relationships occurred among TRS parameters with each change/stress indices measured in tissues of mussels, could reinforce the use of PSH as a potent biomarker.     

氧掺杂碳气体扩散电极用于电催化产活性氧抗菌防污研究

过氧化氢(H₂O₂)等活性氧(ROS)物质因具有绿色高效的特点,在废水处理、杀菌消毒等领域受到研究者广泛关注。利用电催化生成H₂O₂是一种实时提供活性氧物质的有用方法。然而,目前报道的大多数高性能催化材料都是粉体形式,不便于在实际场景中的应用。因此,制备可直接应用的电极材料显得尤为重要。本研究利用喷涂-热解的制备方法,制备了高活性氧催化活性的氧化炭黑(O−CB)/多孔碳毡电极,通过聚四氟乙烯(PTFE)的修饰优化电极表面的氧气传质,成功制备氧掺杂碳气体扩散电极。研究结果表明,O−CB/PTFE-5 wt%电极具有最高的催化性能,其合成H₂O₂的速率达27.19 mg·L^-1(mg catalyst)^-1·cm^-1·h^-1。海洋典型污损微生物假单胞菌(Pseudomonas sp.)的抗菌实验表明,该电极电催化作用60 min产生的活性氧对Pseudomonas sp.的杀菌率可达到97.69%,作用120 min的杀菌率可达到99.99%。     

Microbial processes of carbon cycle as the base of food chain of Håkon Mosby Mud Volcano benthic community

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.     

Stability constants of NaSO4−, MgSO4, MgF+, MgCl+ ion pairs at the ionic strength of seawater by potentiometry

The stability of the ion pair NaSO₄ was determined by measuring the change in sodium activity with medium composition at constant ionic strength, using a sodium-sensitive glass electrode. The stability constants of MgSO₄ and MgCl⁺ were determined indirectly from measurements of the stability of MgF⁺ in different media. All measurements were performed at 1 atm pressure, 25 ± 0.1 °C and 0.7 M formal ionic strength. The stability constants for NaSO₄^?, MgSO₄, MgF⁺ and MgCl⁺ are 1.8 ± 0.1, 6.3 ± 0.1, 22.9 ± 0.1 and 0.34 ± 0.02 M^?1, respectively.     

Acute response versus reproductive performance in five strains of brine shrimp exposed to copper sulphate

Five geographically and genetically diverse strains of the brine shrimp, Artemia salina, were tested for response to copper sulphate. Mean survival times (MST) were determined for each strain following continuous exposure to concentrations of 10^?1, 1, 10¹, 10², 10³, 10⁴ and 10⁵ ppm CuSO₄. In addition, lifetime reproductive performance parameters were evaluated for 15 females from each strain after 24 h exposure to 0·067 × 10^?9 CuSO₄.Two-factorial ANOVA revealed that treated females produced fewer offspring per brood and fewer broods per female, resulting in an overall decline in the mean number of offspring per day per female over the reproductive span. When the standard 24 h MST results are compared with the 24 h dose level of CuSO₄ found to impair reproductive performance, the latter was from 24,000 to 156,000 times more sensitive, depending upon strain.     

Shoreline response to a single shore-parallel submerged breakwater

Submerged breakwaters (SBWs) are becoming a popular option for coastal protection, mainly due to their low aesthetic impact on the natural environment. However, SBWs have rarely been employed for coastal protection in the past and therefore, their efficacy remains largely unknown. The main objective of the present study was to investigate the structural and environmental conditions that govern the mode of shoreline response (i.e shoreline erosion vs shoreline accretion) to SBWs. The relative importance of the key structural and environmental parameters governing the response mode to a single shore parallel SBW is investigated through a combination of theoretical analysis and numerical modelling. Using physical considerations, a theoretical response-function model is derived under several simplifying assumptions including parallel depth contours, linear wave theory, shore normal waves, and no wave–current interaction. Numerical modelling is undertaken with the Mike21 model suite to simulate the depth averaged velocity fields (without morphological updating) due to waves acting on a single shore-parallel SBW located on a schematised beach with parallel depth contours. In total 92 coupled wave–current simulations were undertaken. The results indicate that the mode of shoreline response to the SBW can be expressed in terms of the two non-dimensional parameters h_B/H₀ and (s_B/h_B)^3/2(L_B/h_B)²(A³/h_B)^1/2 (variables defined in the text).     

Phytoplankton production in the Tagus estuary (Portugal)

Biomass and phytoplankton photosynthetic response were studied in the lower Tagus estuary weekly, and related to environmental conditions in February, March and April 1994. The Photosynthesis-Irradiance (P₋^BI) relation was studied based on the light-saturated photosynthesis rate (P^Bm) and the light-limited initial slope (a^B). The nutrient concentrations observed were high enough to be considered as not limiting phytoplankton growth. Tagus estuary phytoplankton seems, to a certain extent, adapted to high turbid conditions, being able to utilize the low light levels more efficiently, which was translated by high values of a^B [0.10–0.20 mg C (mg Chl a)⁻¹ h⁻¹ (W m⁻²)⁻¹]; however, light seems to limit phytoplankton production in the water column.     

Wind-related resuspension of sediments in the Peel-Harvey Estuarine System

Resuspension of bottom sediments accounted for 69–92% of mean deposition rates (11·6–69·3 gm^?2 day^?1) measured at 5 sites in the Peel-Harvey Estuarine System, Western Australia. Deposition rates at all but one of the sites were found to be correlated (P<0·05) with a function of wind combining a fetch factor with the number of hours of winds greater than 5 ms^?1 weighted by the third power of wind velocity. The exception was the only site with a cover of benthic algae (Cladophora) during the study. Wind-related resuspension greatly affects the forms and amounts of productivity in this system.     

Calibration of a chalcogenide glass membrane ion-selective electrode for the determination of free Fe in seawater: I. Measurements in UV photooxidised seawater

Calibration of a chalcogenide glass membrane, Fe(III)ISE [Fe_2.5(Ge₂₈Sb₁₂Se₆₀)_97.5], in buffered saline media has been undertaken in order to assess the suitability of this ISE for seawater analyses. The electrode slopes in saline citrate and salicylate buffers were 26.3 and 28.2 mV/decade, respectively, for Fe³⁺ concentrations ranging from 10⁻¹⁰ M to less than 10⁻²⁵ M Fe³⁺. The calibration lines in the citrate and salicylate buffers were essentially collinear with the response in unbuffered chloride-free standards containing >10⁻⁵ M Fe³⁺, demonstrating that the response of the FeISE is unaffected by chloride ions. A mechanism involving a combination of charge transfer and ion-exchange of Fe(III), at the electrode diffusion layer, can be used to explain the ≈30 mV/decade slope of the FeISE. The response of the FeISE in UV photooxidised seawater containing 8 nM total Fe was measured as the pH was changed from 8.27 to 3.51. The slope of the response was 24.2 mV/decade [Fe³⁺] calculated as a function of pH using Fe(III) hydrolysis constants for seawater. Moreover, the response was essentially collinear with that in citrate buffers and in unbuffered solutions containing >10⁻⁵ M Fe³⁺ and the slope for the combined data was 26.2 mV/decade. This study was restricted to organic-free seawater because the certainty in Fe(III)–ligand stability constants is insufficient to warrant the selection of an ideal calibration buffer system, and there is evidence that powerful chelating ligands (e.g., EDTA along with humic and fulvic acids) may alter the response of the Fe(III)ISE. The Fe dissolution rate of the FeISE in UV photooxidised seawater was found to be 1.6×10⁻² nmol Fe/min, as measured by cathodic stripping voltammetry (CSV). This would contaminate a 100-ml sample by 0.8–1.6 nM Fe over a typical measurement period of 5–10 min obtained using a stability criterion of 0.5 mV/min. Various methods are proposed for reducing the level of contamination in open ocean samples that contain sub-nanomolar concentrations of iron. The FeISE has the potential to detect free Fe³⁺ at concentrations typically found in natural seawater.     

Quantitative evaluation of turbulent mixing in the Central Equatorial Pacific

Turbulent mixing in the central equatorial Pacific has been quantitatively evaluated by analyzing data from microstructure measurements and conductivity temperature depth profiler (CTD) observations in a meridionally and vertically large region. The result that strong turbulent mixing with dissipation rate ε (>O(10^?7) W kg^?1), continuing from sea-surface mixed layer to low Richardson number region below, in the area within 1° of the equator, shows that turbulent mixing has a close relationship to shear instability. ε > O(10^?7) W kg^?1 and turbulent diffusivity K _ρ  > O(10^?3) m² s^?1 were obtained from near-surface to 85 db at stations even southwardly beyond 3°S, where it is already far from the southern boundary (~2°S) of the Equatorial Undercurrent. Turbulence-induced heat flux and salinity flux were calculated, and both had their maxima in the equatorial upwelling region, though the former was downward and the latter was upward. Accordingly, vertical velocity in the upwelling region was estimated to be similar to the results derived by other methods. These fluxes and the vertical velocity suggest the critical importance of turbulent mixing in maintaining the well-mixed upper layer. Secondly, in the intermediate region (>500 db), turbulent eddies were investigated by applying Thorpe’s method to the CTD data. A large number of overturns were detected, with spatial-averaged K _ρ (700–1,000 db) being 3.3 × 10^?6 m² s^?1, and the corresponding K _ρ-max reaching to O(10^?4) m² s^?1 in the north (3°–13°N). The results suggest that, in the intermediate region, considerable turbulent mixing occurs and moderates the properties of the water masses.     

水下溢油油滴粒径分布实验研究

Oil droplet size distribution(ODSD) plays a critical role in the rising velocity and transport of oil droplets in subsurface oil releases. In this paper, subsurface oil release experiments were conducted to study ODSD under different experimental conditions in a laboratory water tank observed by two high-speed cameras in March and April 2017. The correlation formulas Oh=10.2 Re~(–1) and Oh=39.2 Re~(–1)(Re represents Reynolds number and Oh represents Ohnesorge number) were established to distinguish the boundaries of the three instability regimes in dimensionless space based on the experimental results. The oil droplet sizes from the experimental data showed an excellent match to the Rosin–Rammler distribution function with determination coefficients ranging from 0.86 to 1.00 for Lvda 10-1 oil. This paper also explored the influence factors on and change rules of oil droplet size. The volume median diameter d50 decreased steadily with increasing jet velocity, and a sharp decrease occurred in the laminar-breakup regime. At Weber numbers(We) 100, the orifice diameter and oil viscosity appeared to have a large influence on the mean droplet diameter. At 100We1 000, the oil viscosity appeared to have a larger influence on the relative mean droplet diameter.     

Dissociation of hydrogen sulphide in seawater and comparison of pH scales

The protonization constant of HS^? (K₁₂) has been determined potentiometrically (glass electrode) at atmospheric pressure in synthetic seawater in the salinity range 2.5–40‰ at 5 and 25°C and in NaCl solutions in the formal ionic strength of 0.1–0.8 M at 5 and 25°C. The difference between synthetic seawater and an NaCl solution with the same formal ionic strength can be explained in terms of the complexation of H⁺ by sulphate in seawater. These results can be used to compare the pH scales suggested by Hansson (1973c) and Bates (1975). Furthermore, comparison between the present values of K₁₂ and those of Goldhaber and Kaplan (1975) makes it possible to compare the conventional pH scale with Hansson's titration pH scale. The conditional protonization constant of HS^? in seawater of different salinities can be used to modify the Gran plots (Hansson and Jagner, 1973) for alkalinity measurements in anoxic seawater. Ion-pair formation between HS^? and Mg²⁺ or Ca²⁺ seems to be very weak.     

Increased benthic grazing: An alternative explanation for low phytoplankton biomass in northern San Francisco Bay during the 1976–1977 drought

Among the consequences of extremely low river flow into northern San Francisco Bay during a two-year drought were (1) a gradual increase in salinity, (2) an unusual decline in chlorophyll a concentration, and (3) the upstream migration of estuarine benthic invertebrates to the normally brackish area of the bay. Total abundance in the benthos at a shallow monitoring site increased from a normal 2000 to greater than 20 000 individuals m^?2 during the summer of 1977, presumably in response to the increased salinity. Estimated filtration rates derived from equations in the literature for one of the species, the suspended-feeding bivalve Mya arenaria ranged from 1 to 4 m³ m^?2 day^?1 during 1977 depending on abundance and mean size on sampling dates. Because water depth at this site is less than 2 m, Mya could have filtered all of the particles (including diatoms) from the water column on the order of once per day. Several other immigrant species undoubtedly contributed to the removal of particles from the near-bottom water as well. Increased benthic grazing, therefore, could have accounted for the anomalously low phytoplankton biomass observed during the drought. These results suggest that during periods of prolonged low river flow and increased salinity benthic food webs could become more important than planktonic food webs in the upper part of the estuary.     

Apparent dissociation constants of hydrogen sulfide in chloride solutions

Spectrophotometric measurements are reported for the first apparent dissociation constant of hydrogen sulfide in seawater over the temperature range 7.5–25°C and 2–35.8‰ salinity. These data are described by the expression $\text{p}\text{K}{}_1\text{′ = 2.527 ? 0.169 Cl}{}^{\mathrm{<mtext>1</mtext><mtext>3</mtext>}}\text{+ 1359.96/T}$. The second apparent dissociation constant in potassium chloride solution was estimated potentiometrically using a sulfide specific ion electrode. A value of ～13.6 was found for pK₂′ at a KCl concentration of 0.67 M. It is suggested that explicit reference to the sulfide ion, S^2?, in describing equilibria in marine waters be dropped in favor of a formulation involving the bisulfide ion, HS^?.     

Food-web structure and trophodynamics of mesopelagic–suprabenthic bathyal macrofauna of the Algerian Basin based on stable isotopes of carbon and nitrogen

The trophodynamics of mesopelagic (macrozooplankton/micronekton) and benthic boundary layer (suprabenthos=hyperbenthos) faunas from the Algerian Basin were characterized on a seasonal scale through stable carbon and nitrogen isotopic analyses of a total of 34 species and two broad taxa (Copepoda and Cumacea). This is the first study simultaneously focused on trophodynamics of deep-sea zooplankton and suprabenthos. Samples were collected southeast of Mallorca (Algerian Basin, Western Mediterranean), on the continental slope close to Cabrera Archipelago, at 650–780 m depths, ca. bi-monthly between August 2003 and June 2004. Mean δ¹³C values of suprabenthos ranged from ?21.1‰ (Munnopsurus atlanticus) to ?16.7‰ (Cyclaspis longicaudata). Values of δ¹⁵N ranged from 2.8‰ (Lepechinella manco) to 9.9‰ (larvae of Gnathia sp.). The stable isotope ratios of suprabenthic fauna displayed a continuum of values, confirming a wide spectrum of feeding guilds (from filter feeders/surface deposit feeders to predators). According to the available information on diets for suprabenthic species, the highest annual mean δ¹⁵N values were found for the hematophagous isopod Gnathia sp. parasite on fish (represented by Praniza larvae) and carnivorous amphipods (e.g. Rhachotropis spp., Nicippe tumida) consuming copepods, and the lowest δ¹⁵N values were found for two cumaceans (Cyclaspis longicaudata and Platysympus typicus) feeding on detritus. Assuming a ¹⁵N-enrichment factor of 2.5‰ and deposit feeders as baseline, we found three trophic levels in suprabenthic food webs. δ¹³C ranges were particularly wide among deposit feeders (ranging from ?21.8% to ?17.3‰) and omnivores (from ?20.5% to ?18.8‰), suggesting exploitation of particulate organic matter (POM) of different characteristics. Our isotopic analyses revealed lower ranges of δ¹³C and δ¹⁵N for macrozooplankton/micronekton, compared with suprabenthos. δ¹³C values of zooplankton taxa ranged from ?21.1‰ (the hyperiid Phrosina semilunata) to ?19.9‰ (the decapod Pasiphaea multidentata), while δ¹⁵N values ranged from 3.9‰ (P. semilunata) to 7.5‰ (P. multidentata). Among zooplankton, more enriched δ¹⁵N values were found among carnivores (e.g. the fish Cyclothone spp. and Pasiphaea multidentata) preying on copepods, hyperiids, euphausiids and small fish. The lowest δ¹⁵N values were found for hyperiids that feed on the mucus nets of salps (e.g. Vibilia armata). After contrasting isotope analysis with dietary data, we conclude there were two trophic levels among zooplankton/micronekton. Strong correlation between the mean annual δ¹⁵N and δ¹³C values was found for zooplankton (R²=0.7), but not for suprabenthos, which suggests a single source of carbon for plankton. We found a general seasonal trend for δ¹³C enrichment from late autumn (November) to late winter–spring (February–April) for both suprabenthos and zooplankton. The δ¹³C enrichment in February–April was correlated in zooplankton with higher surface chlorophyll a concentration 1 month before sampling. As evidenced by δ¹³C–δ¹⁵N correlations, the response of zooplankton to the peak of surface primary production was almost immediate (an increase of δ¹³C–δ¹⁵N correlations in February), and stronger than for suprabenthos. The response among suprabenthos was weak, with slight increase in δ¹³C–δ¹⁵N relationships in April–June.     

基于最小二乘法与RBF神经网络的溶解氧检测系统设计

为克服温度对溶解氧传感器的影响,对极谱型溶解氧检测系统的溶解氧电极激励源、高精度信号采样、软件标定和温度补偿等方面进行研究。通过对极谱型溶解氧传感器工作原理进行分析,设计了极谱型溶解氧传感器检测电路;根据溶解氧电极的温度特性,设计了基于NTC(负温度系数)热敏电阻的硬件温度补偿电路,并利用最小二乘法及RBF神经网络构建了软件温度补偿模型。利用饱和蒸馏水进行温度补偿实验,结果表明:经温度补偿后,该溶解氧检测系统的相对误差及采样波动均在1%以内,大大减小了传感器的非线性误差,测量精度和稳定性均可满足应用要求。     

Estimation of the non-seasonal production of Spartina maritima (Curtis) Fernald in a South African Estuary

Net aerial production of Spartina maritima (Curtis) Fernald, in a warm temperature estuary in Algoa Bay, South Africa, occurring possibly as an exotic, was estimated as 523–680 g dry weight m^?2 year^?1. The method of production measurement designed here used community structure data and accounted for the species' extremely slow shoot production (3.1–6.7 dry g m^?2 year^?1) and continuous leaf turnover (516–676 dry g m^?2 year^?1). Standard methods of production measurement for other Spartina species failed by not accounting for the non-seasonal growth of S. maritima. N, C, organic and energy content of live and dead shoots remained constant through the seasons. The P : B ratio is 1.1, which is lower than for other Spartina species, but agrees with the low vigour shown by negligible regrowth a year after clipping. Decomposition rates were 90 mg g^?1 month^?1 in winter and 305 mg g^?1 month^?1 in summer. Monthly decomposition values showed significant correlation with air temperature (r = 0.86; P < 0.01), and water temperature (r = 0.80; P < 0.01), suggesting that monthly litterbag losses are a valid means of determining decomposition rate.     

Effects of hexavalent and trivalent chromium on the reproduction of Neanthes arenaceodentata (polychaeta)

This study compared the very different responses of the polychaete Neanthes arenaceodentata to chronic exposure of hexavalent (Cr VI) and trivalent (Cr III) chromium. The polychaetes were exposed to sublethal concentrations of Cr VI and Cr III for periods of 440 days (three generations) and 293 days (two generations), respectively. In the Cr VI test, polychaete reproduction ceased at 100 μg litre^?1, and the number of young produced was reduced at the 12·5 to 50 μg litre^?1 levels and above. However, polychaetes that lived in Cr III during the test showed no adverse effects in 50400 μg litre^?1.