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1.
Alessia M. Rodriguez y Baena Juan Carlos Miquel Pere Masqu Pavel P. Povinec Jerome La Rosa 《Marine Chemistry》2006,100(3-4):269
234Th is a particle-reactive radionuclide widely used to trace biogeochemical oceanic processes occurring over short timescales. During the last few years, small-volume techniques based on the co-precipitation of 234Th with MnO2 coupled with beta-counting have been developed as an alternative to large volume gamma-spectrometric techniques. Here a procedure has been developed to enhance quantitative measurement of 234Th in MnO2 precipitates. The main objectives were to obtain a purified Th fraction for beta-counting and to determine the chemical recovery of 234Th using Th spikes and alpha-spectrometry as an alternative to ICP-MS based methods. Two variations of the procedure are presented. In the first “1 spike” method a 230Th tracer is added to the sample prior to precipitation of MnO2, and UTEVA® extraction chromatography is used to obtain a NdF3(Th) purified source that can be used for both beta-counting of 234Th and alpha-spectrometry of 230Th. In the “2 spike” method a 230Th spike is added and the MnO2(Th) precipitate is directly beta-counted for 234Th and subsequently spiked with 228Th or 229Th prior to UTEVA® purification and alpha-spectrometry. The results confirm the need to process small-volume seawater samples for 234Th measurement in presence of a yield tracer, and show that both the 1 spike and 2 spike methods allow an accurate and precise determination of 234Th (relative percent difference, RPD, between expected and mean measured value < 1%; CV between replicate samples < 3%). Our work also suggests that, although the combined analytical uncertainty on total 234Th measurements accomplished with both versions of the NdF3 procedure is promising (6% for 2-L samples), the precision of the 234Th flux estimation will ultimately depend on the degree of disequilibrium between 234Th and 238U. 相似文献
2.
研究了氧化还原电位(Oxidation Reduction Potential, ORP)对海水中碳钢腐蚀电化学特征的影响,应用动电位极化曲线法探讨了 ORP 与碳钢腐蚀行为之间的关系。结果表明,海水的 ORP 参数对碳钢腐蚀行为具有较大的影响,其中 O2/OH?电对的作用占主导,其他电对如 Fe3+/Fe2+也有一定的影响。随着海水 ORP 的增大,其氧化能力越强,碳钢腐蚀电流增大,腐蚀速度加快。水质相对稳定的开放性大洋海水中,可以考虑海水氧化还原电位在碳钢腐蚀速度预测评估中的应用。 相似文献
3.
Joan D. Willey 《Marine Chemistry》1977,5(3):267-290
Dissolved silica can coprecipitate with zinc from seawater or distilled water that has been enriched with both elements. More than 2 ppm Si are necessary for the reaction to begin. The coprecipitation shows pH dependence. The addition of pulverized illite or natural sediment as suspended particulate material does not enhance the reaction in seawater. The organic material present in the nearshore seawater samples decreases the rate and extent of reaction, as indicated by comparisons of results of experiments using natural seawater with results obtained using UV-irradiated seawater. In unbuffered distilled water the reaction must compete with hydrolysis of zinc; however, reaction does occur, which indicates that the seawater matrix is not essential for the reaction. The coprecipitation can limit the concentration of zinc in seawater to less than the solubility concentration assumed for ZnCO3 or Zn(OH)2. The results suggest that a zinc silicate can precipitate directly from seawater or interstitial water as an authigenic mineral. 相似文献
4.
Masachika Maeda 《Journal of Oceanography》1980,36(3):167-176
This article summarizes the author's current work on microbial degradation of nucleic acid. The aim of this work is to elucidate parts of the saprogenic process in the marine ecosystem through the study of the behavior of nucleic acid-hydrolyzing bacteria inhabiting seawater and sediments.Considerably large population of nucleic acid-hydrolyzing bacteria was found to occur in seawater and sediments. The main genera of these microbes areVibrio spp. in coastal seas, andPseudomonas spp. in the oceanic waters. As a result of microbial attack, nucleic acid components are released into seawater. The properties of extracellular nuclease produced by a marineVibrio sp. are well adapted to the seawater environment; consequently this enzyme has high activity and stability in seawater. By determining nuclease activity in seawater and sediments, the intensities of nucleic acid-hydrolysisin situ were evaluated.Distribution patterns of marine bacteria are also discussed in reference to the occurrence of phytoplankton in seawater. 相似文献
5.
Abstract This paper gives the results of the density of diluted and concentrated standard seawater which has been measured in a salinity range from 0 to 42 and a temperature from 0 to 30°C. Equations for density of standard seawater (S = 35) vs the temperature and for density of standard seawater solutions vs the temperature and salinity have been fitted. 相似文献
6.
An ion-exchange technique was used to concentrate ammonia from seawater. Precipitation of bivalent cations, prior to concentration, reduced the variability of ammonia recovery from the ion-exchange column and lengthened column life. Analysis of the eluate was by the phenolhypochlorite reaction. The method was designed for use with small seawater samples (>10ml) and has the advantage that it can be adapted for use with small volumes of seawater with no loss in sensitivity. In a 10 ml seawater example NH3-N concentrations of 10–150 μg l?1 were accurately determined. 相似文献
7.
An energy conversion system based on deep-sea pressure 总被引：1，自引：0，他引：1
A novel seawater pressure energy conversion system that utilizes seawater pressure to generate electricity has been studied in this paper. The energy conversion system utilizes the pressure difference between the pressurized seawater and the empty pressure container to drive hydraulic motor and the coaxially coupled generator to generate electric power. The output electric energy is recorded by the data logger throughout the process. In the current study, technical analysis is performed with the emphasis on conversion efficiency between seawater pressure energy and output electric energy. The analysis is conducted at various pressure differences through the throttle valve so as to obtain maximum conversion efficiency. Research shows that the optimum pressure difference through the throttle valve and the maximum conversion efficiency can be theoretically calculated when the properties of the conversion system are given. Simulation results have demonstrated the influence of pressure difference on conversion efficiency. The test apparatus has been designed, built and tested in 2004. It successfully generated electric energy of approximately 0.85 kW h at the depth of 2400 m with empty pressure container's holding capacity of 200 L in the voyage “DY105-16” in South China Sea on June 12, 2004. The actual conversion efficiency from seawater pressure energy to electric energy reaches as high as 63.8% which is attractive for underwater equipments. The success of the experiment has tested the feasibility of utilizing seawater pressure energy and brings a new power supply way for long-term in-situ underwater equipments. 相似文献
8.
Behavioral responses to chemically dechlorinated seawater were studied using two species of marine fish associated with power plant discharge areas off Southern California. Opaleye (Girella nigricans) neither avoided nor were attracted to chlorinated seawater containing 0·1 mg/liter total residual oxidants (TRO) which had been dechlorinated using equimolar or excess sodium thiosulfate. Blue-banded goby (Lythrypnus dalli) did not avoid dechlorinated seawater initially containing 0·1 or 0·9–1·0 mg/liter TRO. Previously it has been shown that opaleye avoided chlorinated seawater with oxidant concentrations of 0·1 mg/liter and blue-banded gobies avoided 0·9–1·0 mg/liter TRO. Elimination of chlorine-produced oxidants by thiosulphate dechlorination resulted in 100% survival in both species. The toxicological implications of exposure to dechlorinated seawater are discussed. 相似文献
9.
用简化动力系统模型模拟海水入侵,评估未来漳浦县旧镇梅宅村海水入侵的发展趋势,提出减缓和预防海水入侵的措施,并预测监测点海水入侵的矿化度.结果表明:要减缓海水入侵的速度需要8 a时间,矿化度变为6.243 0 g/L,这表明如果发生海水入侵,恢复的时间比较漫长.但通过增加淡水水源,并淡水水头水位保持在6.2个单位(1单位... 相似文献
11.
It is generally accepted that seawaters near the ocean surface are supersaturated with calcite and that increasing atmospheric CO2 will not overcome this condition until late in the 21st century. These expectations are based on comparisons of the ion activity products (IAPs) of various seawaters to the solubility product (K) of seawater saturated with pure calcite at 1 atm and a given temperature. It has been shown in recent papers, however, that calcites in contact with natural seawater in the surface oceans are not pure, but are magnesian calcite compositions. As a result, the presently accepted values of the solubility product of calcite in seawater cannot be used to obtain a correct, or even a reasonable estimate of the saturation state of sea water relative to either pure or magnesian calcite. Data are presented demonstrating that use of the currently accepted solubility product of calcite in seawater to determine seawater's relative calcite saturation leads to gross overestimates of its extent. 相似文献
12.
A bioassay experiment using caged mussels has suggested a total concentration of methylmercury in the seawater of a polluted estuary of 0.06 ng dm?3. The technique may provide a useful tool for the assessment of relative concentrations of methylmercury in seawater at different locations. 相似文献
13.
The rate of iron(II) oxidation in North Sea water of pH 5.5–10 in the range 10–25°C has been studied. The oxygenation rate depends linearly on the iron(II) and dissolved oxygen concentrations. The second-order dependence on [OH?], found by several investigators for synthetic solutions, was confirmed in seawater, but only for pOH > 6.9. For pOH < 5.9 the rate appeared to be independent of the pOH. In the intermediate range, pOH 5.9–6.9, corresponding to the natural pH of seawater, a first-order dependence on the pOH is obeyed. The important discrepancy in the literature between the second-order rate constant for NaCHO3 solutions and for seawater can be attributed predominantly to the incorrect assumption of a second-order pOH dependence in natural seawater. The results can be useful, for example, in predicting the effect of dumping acidic iron waste from the titanium-dioxide industry into the ocean. 相似文献
14.
An investigation has been made of available data on the saturation state of seawater with respect to calcium carbonate and its possible significance for scale formation on Ocean Thermal Energy Conversion (OTEC) heat exchangers. Pertinent oceanographic data is lacking at or near potential OTEC sites for the calculation of the degree of saturation of seawater with respect to calcium carbonate. Consequently, only “extrapolated” saturation values can be used. These indicate that near surface seawater is probably supersaturated, with respect to the calcium carbonate phases calcite and aragonite, at all potential OTEC sites. The deep seawater that would be brought to the surface at the potential Atlantic Ocean sites is also likely to be supersaturated with respect to calcium carbonate. The deep seawater at the potential Pacific Ocean sites may be slightly undersaturated.The fact that OTEC heat exchangers will be operating in seawater, which is supersaturated with respect to calcium carbonate, means that if nucleation of calcite or aragonite occurs on the heat exchanger surfaces, significant growth rates of calcium carbonate scale may be expected. The potential for calcium carbonate nucleation is highest at cathodic metal surface locations, which are produced as the result of aluminum corrosion in seawater. Consequently, corrosion and scale formation may be closely related. What the possible effects of biofouling may be on this process are not known. 相似文献
15.
本研究提出了一种用于检测海水中锌离子（Zn2+）含量的电化学检测方法。该方法首先应用水热法合成SiO2@PDA-Sb复合材料,然后将该复合材料修饰到玻碳电极上制备SiO2@PDA-Sb-Nafion/GCE,利用差分脉冲阳极溶出伏安法（DPASV）对珠江口海水水样中Zn2+进行测定。研究结果表明,Zn2+在SiO2@PDA-Sb-Nafion/GCE上具有较强的溶出峰。在最优条件下,SiO2@PDA-Sb-Nafion/GCE对Zn2+浓度在1~1 000 nmol/L范围内可实现灵敏、准确的检测,Zn2+的检测出限为0.71 nmol/L。加标回收率实验显示Zn2+加标回收率为93.19%~100.12%,表明该方法可应用于现场海水样品Zn2+测定。本方法具有电极制作简单、稳定性和抗干扰性良好,能够提高现有测定方法的检测限和精确度,在现场海水检测痕量Zn2+具有较好的应用前景。 相似文献
16.
A method is described for the determination of Th isotopes (232Th,230Th,228Th and227Th) in seawater through analysis of Th adsorbed on MnO2-impregnated fiber that has been moored in the deep sea for up to 10 months. Since the MnO2-fiber adsorbs Th from seawater at a constant rate, natural234Th can be used as a yield monitor by making a correction for its decay during the period of deployment. The results obtained by the method showed good reproducibility and accuracy. The method has the advantage over the chemical coprecipitation method that the time and labor for sampling and processing a large-volume of seawater is reduced. 相似文献
17.
The seawater chemistry of potentially toxic metals can affect their availability to marine organisms. Investigation of the relationship between metal chemistry and metal bioavailability has progressed slowly due to difficulties in controlling and measuring metal speciation in uptake media. Recent work with strong metal chelators such as NTA and EDTA has allowed a closer examination of how metal chemistry relates to biological accumulation and toxicity.1–3 However, the presence of a strong chelator at membrane transport sites and the possible alteration of microenvironments by strong chelators could create unnatural uptake behavior. This study presents another method for stabilizing metal chemistry in accumulation experiments. A cation exchange resin was used to study Mn54 accumulation by a small bivalve Donax variabilus. The resin proved an effective method for buffering manganese chemistry in seawater and could provide a useful tool to look for subtle effects present in other metal buffered seawater systems. 相似文献
18.
夏季外海水入侵对大亚湾浮游植物群落结构的影响 总被引：1，自引：0，他引：1
夏季大亚湾存在由粤东沿岸上升流所引起的外海水入侵现象,且入侵强度存在年际差异,作者利用大亚湾2004～2017年历年夏季航次调查数据,将弱入侵年份与强入侵年份进行对比分析,以探讨外海水入侵对大亚湾浮游植物群落结构的影响。结果显示,当外海水入侵由弱变强时,湾内水体理化特征发现显著变化,水体由高温低盐转变为低温高盐,N、P等营养盐含量出现下降。海水理化性质的改变导致了浮游植物群落结构的变化,硅藻、甲藻种类数以及浮游植物Shannon-wiener指数均出现升高;浮游植物总丰度和硅藻丰度下降,甲藻丰度变化不明显;常见浮游植物种类伪菱形藻属(Pseudo-nitzschiasp.)、角毛藻属(Chaetocerossp.)和叉角藻(Ceratiumfurca)丰度出现下降,而中肋骨条藻(Skeletonemacostatum)和菱形海线藻(Thalassionemanitzschioides)丰度出现升高;优势种由单一硅藻种类向硅藻和甲藻共为优势转变。此外,外海水入侵还会通过改变海水理化因子的空间分布以及湾内上层水体流向来影响浮游植物群落结构的空间分布。 相似文献
19.
A method for the determination of nanomolar concentrations of orthophosphate in oligotrophic seawater developed by Liang et al. (2007) has been modified to make it fully feasible for shipboard application and for faster sample throughput with minimized
sample volume. The technique is based on the flow injection method with solid phase extraction on a Sep-Pak C18 cartridge
and colorimetric detector. The Schlieren effect was minimized by rinsing the cartridge sequentially with 5 mL water and 2
mL 95% ethanol solution. With three micro pumps in parallel, savings of up to 80% in amount of reagents and 25% volume of
seawater samples could be achieved in comparison to the previous method. Variation of stopped flow time and sample loading
time gave 3 different standard curves, which corresponded to 3 linear ranges within 3.4 and 515 nM. The modified method permits
the analysis of samples over a wide range of concentrations, and has been successfully applied to shipboard determination
of trace orthophosphate in more than 200 seawater samples during a one-month cruise in the South China Sea. For seawater at
concentrations of 20.6, 82.5, 206.2 nM orthophosphate, the relative standard deviations (RSD) (n = 6), determined daily for 6 days on board ship were 4.45%, 4.73% and 6.75%, respectively. Five seawater samples collected
in the Station SEATS (South East Asia Time Series Station at 18°N, 116°E) were analyzed using the present method both on board
and in a land-based laboratory, as well as with the magnesium hydroxide-induced coprecipitation (MAGIC) method, and showed
no significant difference according to the statistical t-test. 相似文献
20.
The northern part of Okinawa Island suffers from red soil pollution—runoff of red soil into coastal seawater—which damages coastal ecosystems and scenery. To elucidate the impacts of red soil pollution on the oxidizing power of seawater, hydrogen peroxide (HOOH) and iron species including Fe(II) and total iron (Fe(tot), defined as the sum of Fe(II) and Fe(III)) were measured simultaneously in seawater from Taira Bay (red-soil-polluted sea) and Sesoko Island (unpolluted sea), off the northern part of Okinawa Island, Japan. We performed simultaneous measurements of HOOH and Fe(II) because the reaction between HOOH and Fe(II) forms hydroxyl radical (•OH), the most potent environmental oxidant. Gas-phase HOOH concentrations were also measured to better understand the sources of HOOH in seawater. Both HOOH and Fe(II) in seawater showed a clear diurnal variation, i.e. higher in the daytime and lower at night, while Fe(tot) concentrations were relatively constant throughout the sampling period. Fe(II) and Fe(tot) concentrations were approximately 58% and 19% higher in red-soil-polluted seawater than in unpolluted seawater. Gas-phase HOOH and seawater HOOH concentrations were comparable at both sampling sites, ranging from 1.4 to 5.4 ppbv in air and 30 to 160 nM in seawater. Since Fe(II) concentrations were higher in red-soil-polluted seawater while concentrations of HOOH were similar, •OH would form faster in red-soil-polluted seawater than in unpolluted seawater. Since the major scavenger of •OH, Br−, is expected to have similar concentrations at both sites, red-soil-polluted seawater is expected to have higher steady-state •OH concentrations. 相似文献