In situ measurement of particle size in estuarine waters

A novel approach to particle sizing in estuarine waters using a submersible laser diffraction instrument is described. In situ measurements with this instrument are rapid and avoid both the physical disruption of fragile aggregates with pumping and the settlement of larger particles in isolated samples which interfere with currently available sizing techniques. Measurements of the size distributions of suspended particle populations in the Tamar Estuary using this apparatus are compared with measurements carried out on discrete samples obtained from the same depth by pumping. The results confirm the fragile nature of estuarine aggregates and the necessity for in situ measurements in studies of estuarine suspended particle dynamics and fluxes.     

Copper speciation in estuarine waters by forward and reverse titrations

The chemical speciation of copper in the estuarine waters of the Vigo Ria was determined by titrations with salicylaldoxime (reverse copper titrations) and with copper (forward titrations). The forward titrations quantified the concentrations of ligands present in excess whereas the reverse titrations demonstrated the presence of low concentrations of very strong binding ligands, approximately matching the copper concentration. The data obtained by the reverse titrations indicated that copper was about 10× stronger bound than data based on the usual forward titrations.The copper concentration in these ria waters was low at 5 nM with a minor mid-estuarine maximum of 8 nM. These copper levels are amongst the lowest reported for estuarine waters and therefore represent uncontaminated waters. The concentration of inorganic copper was very low across the ria at  10–100 fM, except at Bouzas harbour (salinity 35.5) where it was raised to  1 pM due to copper contamination, in waters affected by the port facilities, to total levels of 15 to 20 nM copper, exceeding the concentration of the very strong ligand detected by the reverse titrations.     

Effects of oxic and anoxic filtration on determined methyl mercury concentrations in sediment pore waters

Accurate determination of methyl mercury (MeHg) concentrations in sediment pore waters is crucial for an improved understanding of mercury (Hg) biogeochemistry, and for improved risk assessment of Hg contaminated sites. In the present study, effects of oxic (air) and anoxic (N₂) filtration (after centrifugation) on determined pore water MeHg concentrations were investigated in severely Hg contaminated pulp fibre sediments from two estuaries of the Bothnian Sea, Sweden. MeHg was determined in the filtrate using species-specific isotope dilution gas chromatography inductively coupled plasma mass spectrometry (SSID–GC–ICPMS), after ethylation with sodium tetraethylborate. Determined concentrations of MeHg were greater after anoxic filtration than after oxic filtration for all samples investigated, with MeHg(N₂)/MeHg(air) ratios ranging between 3.4 and 343. Adsorption to newly formed Fe(III)/Mn(III/IV)-oxy/hydroxide surfaces is proposed as the main mechanism responsible for MeHg removal during oxic filtration. This is supported by decreases in dissolved Fe and Mn concentrations during oxic filtration, and by decreases in dissolved sulphur concentrations during oxic filtration in the samples with largest effect on MeHg concentrations. The latter is explained by adsorption of SO₄²⁻ to newly formed Fe(III)/Mn(III/IV)-oxy/hydroxide surfaces. The effect of oxidation during filtration on pore water MeHg concentrations was largest in samples in which FeS(s) was not present, but with calculated pe-values below − 3. Thus, our results indicate that the largest errors with respect to pore water MeHg concentrations when filtering in air can be expected in samples with an intermediate redox potential, possibly buffered by a mixture of oxidation sensitive Fe(II/III) minerals.     

Enhanced concentrations of dissolved gaseous mercury in the surface waters of the Arctic Ocean

During an almost three months long expedition in the Arctic Ocean, the Beringia 2005, dissolved gaseous mercury (DGM) was measured continuously in the surface water. The DGM concentration was measured using an equilibrium system, i.e. the DGM in the water phase equilibrated with a stream of gas and the gas was thereafter analysed with respect to its mercury content. The DGM concentrations were calculated using the following equation, DGM = Hg_eq / k_H' where Hg_eq is the equilibrated concentration of elemental mercury in the gas phase and k_H' is the dimensionless Henry's law constant at desired temperature and salinity. During the expedition several features were observed. For example, enhanced DGM concentration was measured underneath the ice which may indicate that the sea ice acted as a barrier for evasion of mercury from the Arctic Ocean to the atmosphere. Furthermore, elevated DGM concentrations were observed in water that might have originated from river discharge. The gas-exchange of mercury between the ocean and the atmosphere was calculated in the open water and both deposition and evasion were observed. The measurements showed significantly enhanced DGM concentrations, compared to more southern latitudes.     

A rapid birefringence method for measuring suspended CaCO3 concentrations in seawater

The extreme birefringence of calcium carbonate (CaCO₃) relative to other major components of marine particulate matter provides a basis for making optical in situ measurements of particulate inorganic carbon (PIC) in seawater. This concept was tested with a benchtop spectrophotometer equipped with a 1- and 10-cm path length sample cell and modified with linear polarizers to measure the birefringence of suspended particles. Sample suspensions containing 3–100% CaCO₃ (by weight) were prepared from calcareous marine sediment material and varying amounts of non-birefringent diatomaceous earth. The samples ranged in total suspended material from 0.003 to 249 mg l⁻¹ and PIC from 0.03 to 1820 μmol CaCO₃ l⁻¹. A positive relationship was observed between birefringence and PIC, with response falling off as the total particle concentration and the relative abundance of non-CaCO₃ particles in the sample increased. Sensitivity increased linearly with optical path length, and absolute detection limits of 0.2–0.4 and 0.04–0.08 μmol CaCO₃ l⁻¹, respectively, were determined for path lengths of 1- and 10-cm based on the intrinsic signal noise of the modified spectrophotometer. Conventional (i.e., non-polarized) transmittance measurements were used to correct the birefringence signal for the sensitivity loss due to interference from scattering and absorption. Without further modification, this spectrophotometer-based method can be used (with a 10-cm cell) to quantify PIC in most surface ocean waters—including those influenced by coccolithophore blooms. The spectrophotometer results define performance requirements and design parameters for an in situ instrument capable of operating over the oceanic range of PIC.     

Sampling and analysis for Pu and Am in natural waters

Measurement of the concentrations and physico-chemical states of transuranic elements in natural waters is difficult because of the low levels and the lack of stable elements present for comparison. A sorption technique for sampling transuranic radionuclides from up to 4000 l of water in 3 h is discussed here. Particulate, soluble, and, what is believed to be, colloidal fractions are collected and analyzed separately. The technique has been tested in fresh and salt water for Pu and Am both in the field and in the laboratory and the results are reported. It is a reliable method for measuring the concentrations of Pu and Am in natural waters and simplifies the collection, transport and measurement of large-volume water samples.     

Comparison of sampling devices for trace metal determinations in seawater

The results of an intercomparison of three types of sampling device and three types of hydrowire, used for the collection of seawater samples for trace metal analysis, are presented. These devices were intercompared in an international experiment involving member states of the Intergovernmental Oceanographic Commission through the collection of mid-depth North Atlantic water samples at Panulirus Station near Bermuda. Of the commercially available sampling devices, modified GO-FLO samplers appear to yield the lowest concentration seawater samples with modified Niskin samplers having only slightly inferior capability. Both unmodified GO-FLO and Hydro-Bios samplers have similar, but generally poorer, abilities for the collection of uncontaminated samples. Of the three hydrowires intercompared, plastic-coated steel yields the lowest concentration samples for most metals. Kevlar and stainless-steel hydrowires appear to cause only slight contamination for some metals. Overall, the impression is obtained that differences between the levels of metals in the ocean reported by different laboratories is predominantly due to analytical, rather than sampling errors or artifacts.     

Optimizing alginate beads for the immobilisation of Phaeodactylum tricornutum in estuarine waters

This study addresses the influence of calcium as hardening agent, on alginate gel bead stability and suitability for the growth of Phaeodactylum tricornutum Bohlin (Bacillariophyceae) in estuarine waters. Alginate beads produced with 1, 2, 4, 5 and 6% of CaCl₂ solutions were investigated for stability and suitability for growth of P. tricornutum cells, under mean salinity 27, at 220 and 440 rpm stirring laboratory conditions, and in devices placed under in situ estuarine conditions. Gel stability and suitability for cell growth were evaluated through bead diameter, bead disruption, dissolution and loss of spherical shape, cell viability and specific growth rates. Beads gelled with 5% CaCl₂ were found the most suitable to sustain gel stability and cell growth in the estuarine waters. These beads were surveyed during dredging operations in the Tagus estuary, both in situ and in estuarine water under laboratory conditions, showing significantly lowered growth rates possibly due to Mn, Co and As accumulated in the cells. Results confirmed that the monitoring tool presented is reliable and effective for the assessment of anthropogenic impacts.     

AMS测量海水129I的气载分离制样

本研究建立了AMS(Accelerator mass spectrum,加速器质谱)测定海水中129 I的气载分离制样方法:对加入载体的海水样品进行氧化还原处理,在加热的条件下将生成的单质碘吹出,并使用吸收装置吸收,后经阴离子交换树脂富集纯化,最后生成用于AMS分析的AgI沉淀,本方法全程回收率50%~70%,在相对密闭的体系中进行,减少了碘的损失,相对于萃取-反萃取的制样方法具有可操作性强,避免有机试剂使用等优点,可用于固态、液态和气态样品中129 I的AMS分析制样。     

EGTA滴定法测定海水Ca2+浓度精度评估及其在近海海域实测的必要性

海水Ca²⁺浓度是计算碳酸钙饱和度的重要参数之一,通常由海水钙盐比值计算得出,但该方法在受多种因素影响的近海海域可能不适用。本研究开展了EGTA自动电位滴定法对不同盐度海水Ca²⁺浓度测定精度和准确度的研究,探究“盐效应”对Ca²⁺浓度测定可能存在的影响,并比较了近海养殖区海水实测Ca²⁺浓度与通过钙盐比估算值的差异。研究表明：(1)EGTA自动电位滴定法测定不同盐度海水Ca²⁺浓度精度较高,在各个盐度条件下,5次平行测定的标准偏差为0.001～0.006 mmol/kg,精度均优于0.1%;(2)在盐度20.00～34.62范围内,Ca²⁺的实测值与通过钙盐比值计算所得的相对误差为-0.043%～0.023%,准确度在±0.05%内;(3)不同盐度海水样品Ca²⁺浓度的实测值与理论值基本吻合,电位滴定法测定Ca²⁺浓度不存在“盐效应”问题;(4)受陆源输入过程的影响,近海(烟台牟平养殖区)表层及底层海水Ca     

Seasonal variations of dissolved and particulate copper species in estuarine waters

This one-year survey conducted in the macrotidal estuary of Penzé (Brittany, Western part of the Channel, France) was aimed at examining the variations of the various dissolved and particulate copper species. Ten field stations along the whole freshwater–seawater mixing zone were sampled each month. Different biogeochemical parameters (SPM, chl-a, pH and DOC) were also measured. The levels in total dissolved and total particulate copper ranged from 1.8 to 9.5 nM and from 5 to 98 μg g⁻¹, respectively; such amounts are indicative of a pollution-free system. Extractable C₁₈ copper (non-polar hydrophobic organic copper species), in winter and spring, accounted for 30–40% of the total dissolved copper. In summer, this contribution rapidly rose to 60% in the salinity range 20–30; over the same period of time, total particulate copper decreased. The change in dissolved copper speciation and the lowering of particulate copper concentrations were attributed to the release of strong organic ligands by phytoplankton. Our field data evidenced a highly variable behaviour for the various copper species over the seasonal cycle, and then led us to identify the following mechanisms: (i) metal desorption from organic river-flown particles (winter and spring), (ii) metal desorption from resuspended sediment in the upstream section (summer), (iii) competition between particles, non-extractable C₁₈ organic ligands and phytoplankton-released extractable C₁₈ organic ligands to complex copper in the downstream section (summer), and (iv) removal of non-extractable C₁₈ organic copper by adsorption (autumn). Dissolved copper species fluxes were assessed: most of metal inputs to the estuary (60–74%) corresponded to non-extractable C₁₈ organic copper. Winter and spring metal output fluxes were mainly constituted of non-extractable C₁₈ organic complexes; on the other hand, extractable C₁₈ organic complexes were predominant in summer and autumn output fluxes.     

Determination of copper complexation with natural organic ligands in seawater by equilibration with MnO2 II. Experimental procedures and application to surface seawater

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.     

河口海岸三维水流数值模型中几种垂向坐标模式研究述评

回顾了近年来国内外河口、近岸海域三维斜压水流数值模式研究的进展,着重讨论了不同垂向坐标下三维水流模式的发展状况以及存在的问题。地形拟合坐标(σ坐标)模式可以很好地拟合床面地形和自由面,已在物理海洋学中被广泛使用。但在地形变化剧烈,尤其在密度层结效应明显的海域,σ坐标模式中的水平压强梯度力误差会引起伪密度流。寻求高精度的数值模式以及更加有效的拟合坐标变换将是值得努力的方向。     

Analysis of seawater and different highly saline natural waters by capillary zone electrophoresis

Innovative applications of capillary zone electrophoresis (CZE) to the determination of inorganic ions in environmental aquatic samples of high salinity and, particularly, in seawater are reviewed. Emphasis is placed on advanced approaches utilized for securing separation performance from being degraded by the presence of matrix salts and for simultaneous separation of ions different in natural abundance. Also covered are methodologies of present or possible use to evolve the method's practical utility to trace-level ions. Surveyed procedures are tabulated for the purpose of facilitating the method selection or further development. In addition, brief background information on basic methodological principles of CZE in inorganic ion analysis is given for a better orientation of those intending or just beginning to put CZE to work. Finally, possible future research trends and developments of CZE in the area are briefly discussed.     

海水中溶解态铵盐氮同位素分析的预处理方法

以蒸馏法为基础, 研究了适合海水中铵盐稳定氮同位素分析的预处理方法。对蒸馏法预处理过程中的最佳蒸馏时间、沸石的选取、铵盐最适浓度范围等分别进行改进和优化, 获得稳定、高效的海水中铵盐氮稳定同位素分析预处理方法。结果表明: 最佳蒸馏时间为50 min, 铵盐的回收率为(97±5.8)%。测定了不同沸石对不同浓度氨氮的吸附率, 筛选出酸性条件下铵氮吸附效率较高且稳定的康华科技沸石; 确定铵盐的最佳适用浓度范围为2～10 μmol/L, 在该浓度范围内氮回收率94%～99%,氮分馏系数为0.1‰～0.8‰。将此方法应用于长江口海域水样分析, 结果表明, 这一方法可以应用于河口中铵盐的氮同位素分析, 能够为河口中溶解态氮的来源及循环机理等研究提供有效信息。     

海岸河口泥沙数学模型研究进展

对海岸河口泥沙运动的基本方程、数值方法、边界条件、参数选取等进行了归纳总结和评述,以期对本学科的发展起到一定的引导和促进作用。     

239,240Pu in estuarine and shelf waters of the north-eastern United States

The distribution of ^239,240Pu between dissolved and particulate forms has been measured in four estuaries on the north-east coast of the United States (Connecticut River, Delaware Bay, Chesapeake Bay, and Mullica River). The data cover the whole salinity range from freshwater input to shelf waters at 35‰ and includes one profile from a nearly anoxic basin in the Chesapeake Bay.In the organic-rich Mullica River estuary, large-scale removal of riverine dissolved ^239,240Pu occurs at low salinities due to salt-induced coagulation, a mechanism analogous to that for iron and humic acids. Within the 0 to 25–30‰ zone in the other three estuaries, the activity of dissolved ^239,240Pu increases almost conservatively. The activities of particulate ^239,240Pu are highest in the more turbid waters of low salinity regime (0–15‰), but become increasingly insignificant with respect to dissolved ^239,240Pu as salinities increase. At higher salinities corresponding to shelf water, there is a sharp increase in dissolved ^239,240Pu activity. The dissolved ^239,240Pu activity within each estuary appears to be inversely related to the flushing time of water. For example, Chesapeake Bay has a 6–12 month flushing time and has much lower dissolved ^239,240Pu activities than does the Connecticut River Estuary which has a flushing time of a few days. This and other data from the shelf waters are interpreted as indicating that the sharp decrease in dissolved ^239,240Pu activities between shelf and estuarine waters is driven by removal within the estuaries themselves rather than on the shelf.Dissolved ^239,240Pu activities are lower in the nearly-anoxic bottom waters of Chesapeake Bay indicating enhanced removal by redox transformation of Pu [i.e., Pu(V) to Pu(IV)].     

An automated photochemical method for the determination of dissolved organic carbon in sea and estuarine waters

An improved version of Ehrhardt's (1969) method for the analysis of dissolved organic carbon is described. The method, which is automated, determines the carbon dioxide with a non-dispersive infra-red analyser. The conditions of photo-oxidation have been examined in order to achieve maximum performance. It was found that careful attention needed to be paid to U-V source, “oxygen source”, pH and time or irradiation. The completeness of the method was examined by three independent procedures. We concluded that in all cases the extent of oxidation of organic material was in excess of 98%. Typical performance figures were: precision ±2.5% above 2.0 mg C l^?1, approaching 0.03 mg C l^?1 below 1.0 mg Cl^?1; blank, equivalent to 0.3 mg C l^?1; sampling frequency, 10 samples per hour. The lower limit of sensitivity is mainly governed by the blank. The upper limit of the method is greater than 40 mg C l^?1.A wholly continuous modification of the method has been devised which permits on line analyses. An attentuated version of the method has been used for the analysis of total carbonate.The present and other published methods for the analysis of dissolved organic carbon in natural waters are discussed in relation to one another.     

Optimization of the indophenol blue method for the automated determination of ammonia in estuarine waters

Existing automated methods for the determination of ammonia in natural waters suffer from serious ‘salt error’ in estuaries because of changes in pH, ionic strength and optical properties with salinity. A modified automated indophenol blue method is described which minimizes the ‘salt error’ to less than 8% over the entire salinity of estuaries.     

Sulfide control of cadmium and copper concentrations in anaerobic estuarine sediments

Equilibrium concentrations of the toxic trace metals copper and cadmium were calculated for the physico-chemical conditions characterizing pore waters of anaerobic estuarine sediments using available thermodynamic data and assuming simple sulfide minerals control solubilities. Polysulfide complexes are responsible for the solubility of copper in the cuprous (Cu(I)) oxidation state. Predicated copper concentrations, assuming covellite (CuS) is the controlling solid phase, are in reasonable agreement with copper analyses in a wide range of sulfidic waters and sediment pore waters. In the absence of thermodynamic data, no account could be taken of possible polysulfide complexes of cadmium. However, bisulfide complexes appear to account satisfactorily for observed solubilities assuming the existence of greenockite (CdS) as the controlling solid phase. Anaerobic estuarine sediments may act as a sink for copper and cadmium in the common situation in which free sulfide concentrations are controlled by the coexistence of iron sulfide and iron oxide minerals. However, where free sulfides reach high concentrations of 10^?3 M or more, the concomitant increase in concentration of bisulfide and polysulfide complexes may result in the sediments acting as a source of copper and cadmium.