Characterization of seawater and weather aged polyurethane elastomer for bend stiffeners

A bend stiffener grade polyurethane (PU) elastomer was physically and mechanically characterized by attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis and tensile tests. The material was then exposed to artificial seawater and weather up to 12 months to evaluate its stability as bend stiffeners are exposed to this type of environment during offshore operation. The characterization of aged samples was performed comparing the ageing effects on the chemical structure, thermal stability and mechanical properties with those of the non-aged material. The mass variation of aged samples immersed in artificial seawater was also measured. A slight change in the chemical structure led to a color change from dark green to brown in the samples exposed to natural weathering for 12 months. Increases in thermal stability, stiffness and strength characteristics were also verified, which may be associated to additional crosslink formation. In contrast, a significant mechanical property drop was observed for the artificial seawater aged PU, being attributed to a plasticizer effect induced by the ageing fluid. The stress-strain curves were adjusted with the Mooney-Rivlin model allowing the crosslink density estimation. The weather aged PU presented higher crosslink density than seawater aged and non-aged samples.     

Direct Fluorescence Monitoring of Coal Organic Matter Released in Seawater

Whenever immersed in seawater after a collier accident, a fossil fuel such as coal could become a source of pollution to the marine environment. To study the effect of such a contamination, four coal samples from different origins were used. A first analysis on those coals enabled us to determine the content of polycylic aromatic hydrocarbons. Seawater was then mixed with coal to study the organic matter released from coal into seawater. Fluorescence was used for its sensitivity to aromatic compounds, with the additional purpose of evaluating the relevance of using an immerse fluorescence probe to monitor water pollution. Excitation–emission matrices were recorded and the excitation–emission wavelength range corresponding to the highest fluorescence intensity was 230 nm/[370 nm; 420 nm]. The samples with coal happened to fluoresce more than the coal-free samples, the difference depending on the coal origin. The fluorescence intensity increased with coal mass, up to some limit. The particle size also influenced the fluorescence intensity, the finest particles releasing more fluorescing substances, due to their higher exchange surface. When seawater percolated through coal, the samples fluoresced highly at the beginning, and then the fluorescence intensity decreased and reached the seawater level. However, even with a 10 ns acquisition time shift, the fluorescence spectra were not specific enough to show the presence of PAHs in the samples, which were too diluted to be detected, whenever released from coal into seawater. The lifetimes of the seawater and of the coal samples were respectively 4.7 and 3.8 ns, indicating that the substances released from coal mainly consisted of short-lived fluorescing substances, such as natural humic or fulvic substances. Consequently, the presence of coal does not seem to be too detrimental to the marine environment, and a direct fluorescence probe could be used to monitor the seawater organic charge increase due to the immersion of coal in seawater.     

基于钌配合物荧光猝灭原理的新型氟化有机改性溶胶-凝胶氧传感膜的研究

选用3,3,3-三氟丙基三甲氧基硅烷为前驱体,制备氧光化学传感膜材料.利用4,7-二苯基-1,10-邻菲咯啉钌(Ⅱ)([Ru(dpp)3(ClO4)2])为氧荧光猝灭指示剂,通过优化制备条件获得对氧浓度变化具有敏感响应的传感膜.研究结果表明:所制备的氧传感膜对水体中的溶解氧的线性响应范围为0.5～16.0 mg/L,最...     

Trace metals distribution in surface and deep seawater from the Ría de Arousa estuary (north-western Spain): Study before and after the Prestige oil tanker sinking

Cu, Ni, Pb, Mn, Sn, Fe, Al and Zn in surface and deep seawater samples from Ría de Arousa estuary (Galicia, north-western Spain) collected before and after the Prestige spillage were determined. Data were then used to evaluate the impact of the Prestige accident in the Ría de Arousa by applying principal component analysis (PCA) and cluster analysis (CA). Surface water from Sar River and Ulla River was also analysed for the same elements. Determinations were performed by inductively coupled plasma–optical emission spectrometry (ICP–OES) after solid phase extraction (SPE) of element-8-hydroxyquinoline complexes onto commercial C18 cartridges. The highest concentrations were found in sampling stations along Ulla River, while Al, Fe and Sn offered the highest values in surface and deep seawater from the inner part of the estuary, area where the main villages and sport harbours are located. PCA and CA have shown an independent group formed by surface seawater from the East margin of the mouth of the estuary collected after the Prestige oil spill. However, independent groups were not observed when using deep seawater data, and the effect of the Prestige accident appears to be less evident.     

Determination of uranium in seawater by flow-injection preconcentration on dodecylamidoxime-impregnated resin and spectrophotometric detection

A flow injection method has been developed for the determination of uranium in seawater combining the on-line preconcentration with spectrophotometric detection. An aliquot (10 mL) of the seawater sample adjusted to pH 5.5 was injected into the analytical system and uranium was adsorbed on the column packed with styrene-divinylbenzene copolymer resin (Bio-Beads SM-2) modified with dodecylamidoxime which showed high selectivity to uranium. Uranium was then eluted with 0.01 M hydrochloric acid and detected spectrophotometrically after the reaction with Chlorophosphonazo III. Interference from calcium and strontium was masked with cyclohexanediaminetetraacetic acid added to the chromogenic reagent solution. The sample throughput, the detection limit (3σ), and the preconcentration factor were 23 per hour, 0.13 μg/L, and 20, respectively, when the sample injection volume was kept at 10 mL. The precision at the 2 μg/L level was less than 4% (RSD). The proposed method was applied to the determination of uranium in the seawater samples collected off the Boso peninsula, Japan and the uranium concentration was found to be ca. 3 μg/L, which is close to the literature data. The yield of the recovery test ranged from 95% to 99%.     

Hydrothermal calcium-carbonate veins reveal past ocean chemistry

Records of past ocean chemistry provide an integrated history of fundamental Earth processes, including the evolution of its continents, climate, and life. Here, we describe a recent dramatic shift in appreciation of the value and the application of studies of ocean crustal hydrothermal processes, which can be used to both reconstruct records of past ocean chemistry and decipher the past changes to global conditions responsible for any variations in these records. In particular, we describe a recently developed method for the determination of past seawater cation ratios using hydrothermal calcium-carbonate veins precipitated from seawater-derived fluids in the upper ocean crust.     

On-Line Solid Phase Extraction and Spectrophotometric Detection with Flow Technique for the Determination of Nanomolar Level Ammonium in Seawater Samples

The determination of low-level ammonium in seawaters suffers from low sensitivity and high contamination; therefore, it is desirable to develop highly sensitive methods for automatic measurements. A highly sensitive and automated flow technique system for nanomolar level ammonium measurement is described. Reagents for Berthelot reaction were automatically added into seawater samples. After a 10 min reaction at 40°C, the formed indophenol blue compound was on-line extracted onto an Hydrophilic-Lipophilic Balance (HLB) cartridge. The enriched compound was rinsed with water and ethanol solution (30%, v/v) and, in turn, eluted with an eluent containing 30% (v/v) ethanol and 5.0 mM of NaOH, and determined with a spectrophotometer at 640 nm. Parameter, including extraction conditions, reagent concentrations, pH, temperature, and reaction time, were optimized. Under the optimized conditions, the detection limit was 3.5 nM and the linear range was 0–428 nM. The relative standard deviations were 5.7% (n = 8) for 44.6 nM standard solution and less than 6.0% (n = 3–5) for samples within concentrations of about 52.4–288.7 nM; the recovery was in the range 93.6 to 108.5%. The sample throughput was 3 h^?1. The proposed method provides a simple, cheap, and automatic way to determine ammonium in seawater samples without complicated sample treatment.     

Application of factorial designs and Doehlert matrix in optimization of experimental variables associated with the preconcentration and determination of vanadium and copper in seawater by inductively coupled plasma optical emission spectrometry

In the present paper a procedure for preconcentration and determination of vanadium and copper in seawater using inductively coupled plasma optical emission spectrometry (ICP OES) is proposed, which is based on solid-phase extraction of vanadium (IV), vanadium (V) and copper (II) ions as 1-(2-pyridylazo)-2-naphthol (PAN) complexes by active carbon. The optimization process was carried out using two-level full factorials and Doehlert matrix designs. Four variables (PAN mass, pH, active carbon mass and shaking time) were regarded as factors in the optimization. Results of the two-level full factorial design 2⁴ with 16 runs for vanadium extraction, based on the variance analysis (ANOVA), demonstrated that the factors pH and active carbon mass, besides the interaction (pH×active carbon mass), are statistically significant. For copper, the ANOVA revealed that the factors PAN mass, pH and active carbon mass and the interactions (PAN mass×pH) and (pH×active carbon mass) are statistically significant. Doehlert designs were applied in order to determine the optimum conditions for extraction. The procedure proposed allowed the determination of vanadium and copper with detection limits (3σ/S) of 73 and 94 ng l⁻¹, respectively. The precision, calculated as relative standard deviation (R.S.D.), was 1.22 and 1.37% for 12.50 μg l⁻¹ of vanadium and copper, respectively. The preconcentration factor was 80. The recovery achieved for determination of vanadium and copper in the presence of several cations demonstrated that this procedure improved the selectivity required for seawater analysis. The procedure was applied to the determination of vanadium and copper in seawater samples collected in Salvador City, Brazil. Results showed good agreement with other data reported in the literature.     

液液萃取-高效液相色谱-电感耦合等离子体质谱同时测定海水中的多种有机锡

利用高效液相色谱-电感耦合等离子体质谱(HPLC-ICP/MS)联用技术对海水中的五种有机锡[三甲基氯化锡(TMT)、二丁基氯化锡(DBT)、三丁基氯化锡(TBT)、二苯基氯化锡(DPhT)和三苯基氯化锡(TPhT)]进行了分离,采用Agilent TC-C18色谱柱,流动相为乙腈/水/乙酸(65∶23∶12, φ),0.05%三乙胺,pH 3.0,流速为0.6 mL·min-1, 测定了0.5～100 μg·L-1范围内五种有机锡化合物的混合标准工作曲线,其相关系数R2优于0.998,方法的检出限均小于3 ng·L-1。100 mL海水样品用10 mL含有0.2% Tropolone的CH₂Cl₂萃取两次后,有机相合并氮吹浓缩至最后一滴,加入1 mL的乙腈,用0.2 2 μm的有机滤膜过滤后分析。结果表明,海水中只检测到TPhT,含量为53.2 ng·L-1。样品的加标证明DBT, DPhT, TBT和TPhT的加标回收率均优于80%。TMT可能存在吸附或降解问题,回收率仅为50%。     

Promoting effect of low concentration of benzotriazole on the corrosion of Cu10Ni alloy in sulfide polluted salt water

The interaction of benzotriazole (BTAH) with the surface of a corroding copper–nickel alloy in a sulfide polluted salt solution reveals a change in its role from an inhibitor to a promoter of localized corrosion as its concentration changes. A concentration of BTAH ≥5 × 10⁻⁴ M inhibits the corrosion reaction in both the polluted and the unpolluted media. On the other hand, a concentration of 10⁻⁴ M BTAH promotes the localized corrosion of the alloy in the polluted medium while it acts as an inhibitor in the unpolluted salt solution. This finding is substantiated by measurements of mass loss and current transients and examination of the surface by SEM microscopy.