Dimethylsulfide (DMS) is generally thought to be lost from the surface oceans by evasion into the atmosphere as well as consumption by microbe.However, photochemical process might be important in the removal of DMS in the oceanic photic zone.A kinetic investigation into the photochemical oxidation of DMS in seawater was performed.The photo-oxidation rates of DMS were influenced by various factors including the medium, dissolved oxygen, photosensitizers, and heavy metal ions.The photo-oxidation rates of DMS were higher in seawater than in distilled water, presumably due to the effect of salinity existing in seawater.Three usual photosensitizers (humic acid, fulvic acid and anthroquinone), especially in the presence of oxygen, were able to enhance the photo-oxidation rate of DMS, with the fastest rate observed with anthroquinone.Photo-oxidation of DMS followed first order reaction kinetics with the rate constant ranging from 2.5×10^-5 to 34.3×10^-5 s^-1.Quantitative analysis showed that approximately 32% of the photochemically removed DMS was converted to dimethylsulfoxide.One of the important findings was that the presence of Hg²⁺ could markedly accelerate the photo-oxidation rate of DMS in seawater.The mechanism of mercuric catalysis for DMS photolysis was suggested according to the way of CTTM (charge transfer to metal) of DMS-Hg²⁺ complex.

Adsorption kinetics of the interaction between Pt, Pd and Rh (defined here as platinum group elements, PGEs) ions and macromolecular organic compounds (MOCs, >10 kDa), including humic acid, carrageenan and bovine serum albumin, and different cutoff fractions of natural organic matter (>1 kDa and >3 kDa) obtained from seawater using centrifugal ultrafiltration devices were investigated. For a given element, all the adsorption kinetics did not reach equilibrium except the interaction between Pt and >1 kDa cutoff, and between Pd and humic acid. For all the tested MOCs, the adsorption kinetics could be divided into two stages, a rapid adsorption process in the first 8 h and the desorption stage after the first 8 h until the equilibrium. The change trend of partition coefficient (log₁₀K_d) values with experiment time was consistent with that of the kinetic curves. However, in the interaction between PGE ions and natural dissolved organic matter (NDOM), an obvious difference in the change trends of log₁₀K_d and kinetic curves was observed. It indicated that the partition behavior of PGE ions interacting with NDOM in seawater was a combined effect of different organic constituents. The adsorption and log₁₀K_d of PGEs in the >1 kDa NDOM fraction were higher and more stable than those in the >3 kDa NDOM fraction. The results also indicated that the 1–3 kDa NDOM may dominate the interaction between PGEs ions and NDOM. Moreover, no kinetic model could perfectly simulate the adsorption process. It indicated that the colloidal struction and morphology of MOCs or NDOM in seawater might be inhomogeneous. Hence, the interaction between PGE ions and organic matter in seawater was a complicated process and needs further research.

Using semidifferential stripping technique combined with pre-equilibrium complexometric titration, the abnormal phenomena appeared in determining apparent complexation capacity (ACC) are discussed and the improved method for determining ACC is presented in the article.The accuracy of ACC measurement results is tested theoretitelly and experimentally.Based on determination of ACC_Cu, ACC_Pb and ACC_Cd, copper was selected for complexometric titration to determine ACC and the results are proved to be reasonable.ACC_Cu measured in the Haikou Bay surface water is in the range of 166.4-320.2 nmol/dm³, with the mean value of 240.9 nmol/dm³, the maximum value aramd domestic drainage outfall, and the values in other stations are comparatively homogenous.The condition formation constant is in the range of 3.46×10⁷-4.76×10⁸, and the mean value is 1.7×10⁸.Based on the 1:1 comlexing model of copper-natural organic ligand and the toxic concentration limit to marine organisms, seawater self-purification capacity in the Haikou Bay is calculated to be 7.43 μg/dm³.

The unstable state of nitrite results in its very low concentration in seawater, which is below the limit of detection (LOD) of conventional techniques of analysis. Some sensitivity-enhanced methods have been proposed for the determination of nitrite at nanomolar level to illustrate the role of nitrite in the marine nitrogen cycle. However, most of previous reports are not widely accepted, because of their complexity and cost equipment or intensive labor requirement. In this study, a simple automatic system for the determination of nanomolar level nitrite using on-line preconcentration with spectrophotometric detection was described. An Oasis HLB cartridge was adopted to quantitatively enrich the pink-colored azo compound, formed from nitrite via Griess reaction. The cartridge was rinsed with water and ethanol (volume fraction is 55%, the same below), in turn, then eluted by an eluent containing 50% ethanol and 0.25 M(mol/dm³) H₂SO₄, and determined at 543 nm with a 2 cm path-length flow cell. Under the optimized experimental conditions, the calibration curve showed a good linearity in the range of 1.4-85.7 nM, and the LOD (3σ) was estimated to be 0.5 nM. The relative standard deviations of 7 measurements were 4.0% and 1.0% for the samples spiked at 7.1 and 28.6 nM, respectively. The recoveries for the different natural water samples were between 92.2%-108.4%. Each HLB cartridge could be reused for at least 50 times. As compared with other SPE methods, the advantages of this method included the free of interference from salinity variation and less sample consuming. The results of the application of the proposed method to natural water showed good agreement with liquid waveguide capillary cell detection method.

A thorough understanding of the biogeochemical cycling of trace metals in the ocean is crucial because of the important role these elements play in regulating metabolism in marine biotas and thus, the climate. However, a precise and accurate analysis of trace metals in seawater is difficult because they are present at extremely low concentrations in a high salt matrix. In this study, we report an analytical method for the preconcentration and separation of six trace metals, Fe, Ni, Cu, Zn, Cd and Pb, in seawater using a seaFAST automatic solid-phase extraction device, analysis by a triple quadrupole collision/reaction technique with inductively coupled plasma mass spectrometry (ICP-MS), and quantification by the isotope dilution technique. A small volume (10 mL) of seawater sample was mixed with a multi-element isotope spike and subjected to seaFAST procedures. The preconcentrate solution was then analyzed using the optimized collision/reaction cell mode of ICP-MS, with NH₃ gas for Fe and Cd with a flow rate of 0.22 mL/min and He for Ni, Cu, Zn and Pb with a flow rate of 4.0 mL/min. The procedure blanks were 130 pmol/L, 3.0 pmol/L, 6.8 pmol/L, 37 pmol/L, 0.29 pmol/L and 0.42 pmol/L, for Fe, Ni, Cu, Zn, Cd and Pb, respectively. The method was validated using five reference materials (SLRs-6, SLEW-3, CASS-6, NASS-7 and GEOTRACE-GSC), and our results were consistent with the consensus values. The method was further validated by measuring full-water-column seawater samples from the subtropical Northwest Pacific Ocean, and our results demonstrated good oceanic consistency.

Vibrio vulnificus is an opportunistic pathogen widely distributed in estuarine and coastal seawaters. In this study, a culture-free method was developed to rapid detection of V. vulnificus in all seasons, based on loop-mediated isothermal amplification (LAMP) targeting virulent-correlated gene (vcg). The new assay method allows differentiation between the virulent and non-virulent strain of V. vulnificus accurately. This method also allows effective detection of the pathogeny in winter when the bacterium lives in the viable but non-culturable (VBNC) state. A total of 30 costal seawater samples collected in all seasons were used for the evaluation of this method. The results show that the method is sensitive, accurate and convenient.

The specific activities of ²²⁴Ra,²²⁶Ra and ²²⁸Ra were determined by measuring γ-rays of their daughters with HPGe γ spectrometer after preconcentrating Ra isotope' with Mn-fiber adsorption from large volume seawater.The calculating formulas of specific activities of the three nuclides derived.The methods of sample preparation and spectnun analysis were discussed.The advantages of the method are simple,rapid and three nuclides can be determined simultaneously.

Seawater samples are collected in the spring of 2013 from the Taiwan Strait for the analysis of uranium (U) concentrations and isotopic compositions using MC-ICP-MS, and the geochemical behavior patterns of U in the Taiwan Strait are then investigated. Average concentrations of individual U isotopes are (3.23±0.14) μg/kg for ²³⁸U, (2.34±0.09)×10^-2 μg/kg for ²³⁵U and (2.05±0.07)×10^-4 μg/kg for ²³⁴U. Correspondingly, the U isotopic compositions are 155±18 for δ²³⁴U and 138±2 for ²³⁸U:²³⁵U. The U concentrations and isotopic ratios in the Taiwan Strait are similar to those of open ocean seawater, suggesting the dominance of the open ocean input to the strait's U pool. However, river input, as suggested by the slightly lower salinity than that of the open ocean, also affected the U concentrations and isotopic compositions in the strait. From a compilation of U concentrations in the Taiwan Strait and adjacent areas, including the Jiulong Estuary and Zhujiang Estuary, the Xiamen Bay and the northern South China Sea, a strong and significant relationship between U concentration and salinity[U:S; U=(0.093 4±0.002 4)S+(0.092 0±0.061 5)] is revealed, suggesting conservative mixing of U in the Taiwan Strait. To better understand the U geochemistry in the Taiwan Strait, a multiple endmembers mixing model is applied to estimate the contributions of potential sources. The open ocean seawater contributed 69%-95% of U in the Taiwan Strait, with river water approximately 2%, and dust deposition only around 0.13%. Therefore, the model results supported the open ocean input source and the conservative mixing behavior of U derived from the observation of U concentrations and isotopic ratios and U:S ratios. The sediment interstitial water may be an important source of U to the Taiwan Strait with a possible contribution of 3%-29%, consistent with previous investigations based on radium isotopes. However, further investigations are warranted to examine the U concentration in the sediment interstitial water and its input to the overlying seawater in the Taiwan Strait.

Dissolved Cu, Pb, Zn and Cd in the I-Iaikou Bay waters were measured to be respectively in the range concentrations of 0.47-1.16μg/dm³, 0.94-2.36 μg/dm³, 1.28-4.83 μg/dm³ and 0.005-0.072 μg/dm³; with respectively average values of 0.78 μg/dm³, 1.36 μg/dm³, 3.14 g/dm³ and 0.03 μg/dm³.Dissolved Cu and Zn concentrations are relatively high at the stations near the Longkun Road Outfall for domestic sewage, the Xiuying Out-fall for industry waste water and the Haidian Island Estuary, but dissolved Pb and Cd concentrations are low in these stations.The values in other stations are comparatively homogenous.Vertical dissolved Cu, Pb and Zn concentrations at the bottom layer are higher than at the surface layer, but dissolved Cd concentration appears to be on the opposite.The measurement results of Cu, Pb, Zn and Cd in suspended particle show that particulate matters in the Haikou Bay seeweter play a role in purifying heavy metals.The study on strong complexed form and non-liable form of dissolved copper show that the ratio of strong complexed form and dissolved form is about 85%,and non-liable form is very low with a value lower than 5 nmol/dm³.Therefore, nipper in the I-Iaikou Bay seawater cannot cause influence on marine organisms.

The English Channel (the Channel) represents a major sink and transport pathway of anthropogenic radioactive ¹²⁹I. Despite this important role, data concerning the distribution of ¹²⁹I in seawater of the Channel are scarce, and most of existing data are restricted to the eastern part of the Channel. The advection and dispersion of ¹²⁹I from the French coast toward the central and further the English coast, especially in the Channel west of Cap de La Hague, are not fully investigated. We present results of iodine isotopes (¹²⁷I and ¹²⁹I) analyses of surface water samples collected along the central English Channel in October, 2010. The data show high ¹²⁹I concentrations between Dover Strait and La Hague, followed by a dramatic drop towards the Celtic Sea and reveal the dispersal of ¹²⁹I towards central and northern part of the Channel. Our observation also implies that the entire British coast is contaminated by ¹²⁹I. ¹²⁹I levels in the westernmost English Channel, close to the English coast, may reflect combined influences from La Hague and Sellafield. Evolution of ¹²⁹I between 2005 and 2010 suggests a strong link to temporal marine discharges from La Hague plant. The discharges from the nuclear reprocessing facility have continued since 2010 and thus an ecological evaluation of ¹²⁹I radioactive hazards in the environment of the Channel may be needed.