[Research Progress of Analytical Methods with Molecular Spectroscopy for Determination of Trace Nutrients and Metals in Seawaters].

On-field monitoring is an important way to obtain data in marine environmental research. The ocean environmental conditions are harsh and complex, and there are many difficulties in seawater sample collecting, storing, and transporting. Therefore, the on-field and in-situ detections of chemical parameters have always been pursued by oceanographers and have become a research hot point in the seawater analysis field. In this review, the recent research progress of detection methods with molecular spectroscopy techniques for trace nutrients and metals in seawater was summarized. From the view of sensitivity and detection range, we discussed analytical techniques of trace nutrients (phosphate, nitrate, nitrate, and ammonium) and metals (iron, manganese, copper, and aluminum). It focused on methods of on-field and in-situ measures and development of optical methods such as spectrophotometry, fluorescence, and chemiluminescence, as well as the corresponding instruments that are most suitable in marine field observation. Examples of the application of these methods and relative instruments in land-and ship-based laboratories, ship-board underway monitoring, and long-term in-situ observation were presented. The key problems and possible solutions were analyzed, and the future development of the research field was proposed.

[Research Progress on the Determination of Sulfide in Natural Waters: From Laboratory Analysis to In-Situ Monitoring].

Sulfide in natural waters is highly toxic to aquatic organisms. The occurrence of sulfide in natural waters is closely related to water quality and the biogeochemical processes of many other elements because of the labile chemical properties of sulfide. Therefore, it is very important to obtain real and timely concentrations of sulfide in natural waters. In fact, the determination of sulfide in natural waters has long been a hot issue in the field of environmental monitoring. Researchers have developed various analytical methods, mainly based on spectrophotometry, fluorescence spectroscopy, chemiluminescence, electrochemistry, chromatography, and flow-based techniques. In addition, substantial progress has been made in the aspect of automation and intelligence. This review systematically summarized the state-of-the-art progress on the determination of sulfide in natural waters, including sample collection and pretreatment, laboratory analysis, on-site analysis, and in-situ monitoring. The advantages and disadvantages and application scope of each method were compared. The trend of future development was also proposed.

Accumulation and biodegradation of phenanthrene and fluoranthene by the algae enriched from a mangrove aquatic ecosystem.

This study focused on the accumulation and biodegradation of two typical polycyclic aromatic hydrocarbons (PAHs), phenanthrene (PHE) and fluoranthene (FLA), by the diatoms enriched from a mangrove aquatic ecosystem in the Jiulong River estuary, China. After separation, purification and culture, Skeletonema costatum (Greville) Cleve and Nitzschia sp. were exposed to different concentrations of PHE, FLA, and a mixture of the two. The results showed that the tolerance of S.costatum to PHE and FLA was greater than that of Nitzschia sp., and that the toxic effect of FLA on S. costatum and Nitzschia sp. was higher than that of PHE. The microalgal species S. costatum and Nitzschia sp. were capable of accumulating and degrading the two typical PAHs simultaneously. The accumulation and degradation abilities of Nitzschia sp. were higher than those of S. costatum. Degradation of FLA by the two algal species was slower, indicating that FLA was a more recalcitrant PAH compound. The microalgal species also showed comparable or higher efficiency in the removal of the PHE-FLA mixture than PHE or FLA singly, suggesting that the presence of one PAH stimulated the degradation of the other.

[Environmental Behaviors and Ecotoxicology of the Emerging Contaminants Polyhalogenated Carbazoles].

Polyhalogenated carbazoles (PHCs), with a complex chemical structure similar to polychlorinated dibenzofurans, are a class of emerging environmental organic contaminants. There are 135 congeners for PHCs with a pure halogenation. Most of PHCs are not man-made products. Although PHCs in the environment were firstly discovered in the 1980s, these emerging halogenated compounds were not seriously considered until recent years. Recently, more than 20 PHCs have been detected in sediment and soil samples. In addition, studies have shown that PHCs exhibited dioxin-like toxicity and were persistent and bioaccumulative. Therefore, it is very important to understand the distribution, origins and ecotoxicology of PHCs for a better assessment of their environmental risks. To date, research on the environmental behaviors of PHCs is relatively limited and warrants further investigations. In this review, the environmental distribution, source, analytical methods and toxicity of PHCs were summarized and future research needs were outlined.

Degradation kinetics and products of triazophos in intertidal sediment.

This work presents laboratory studies on the degradation of triazophos in intertidal sediment. The overall degradations were found to follow the first-order decay model. After being incubated for 6 d, the percentage of degradations of triazophos in unsterilized and sterilized sediments were 94.5% and 20.5%, respectively. Between the temperatures of 15 degrees C and 35 degrees C, the observed degradation rate constant (kobsd) enhanced as the incubation temperature increased. Triazophos in sediment degraded faster under aerobic condition than under anaerobic one. The water content of sediment had little influence on the degradation when it was in the range of 50%-100%. The values of kobsd decreased with increasing initial concentration of triazophos in sediment, which could result from the microorganism inhibition by triazophos. Four major degradation products, o, o-diethyl phosphorothioic acid, monoethyl phosphorothioic acid, phosphorothioic acid, and l-phenyl-3-hydroxy-1,2,4-triazole, were tentatively identified as their corresponding trimethylsilyl derivatives with a gas chromato-graphy-mass spectrometer. The possible degradation pathway of triazophos in intertidal sediment was proposed. The results revealed that triazophos in intertidal sediment was relatively unstable and could be easily degraded.

Evaluation of multi-walled carbon nanotubes as an adsorbent for trapping volatile organic compounds from environmental samples.

A type of purified multi-walled carbon nanotubes (PMWCNTs) prepared by catalytic decomposition of methane, with a surface area of 98 m2/g, was evaluated as an adsorbent used for tapping volatile organic compounds (VOCs). The performance in evaluation was based on breakthrough volumes (BTVs) and recoveries of selected VOCs. PMWCNTs were also used as a trap packing material to adsorb VOCs purged from spiked water sample. Due to their porous structure, PMWCNTs were found to have much higher BTVs than that of Carbopack B, a graphitized carbon black with the same surface area as PMWCNTs. The recoveries of the tested VOCs trapped on PMWCNTs ranged from 80 to 110%, and not affected by the humidity of purge gas. The results indicate that PMWCNTs are a potential useful adsorbent for direct trapping VOCs from air samples and may be a supplement to VOCARB 3000, a commercially available trap, in purge-and-trap system to preconcentrate VOCs from water samples.

[Bioaccumulation of mercury in Crassostrea sp. exposed to waste seawater discharged from a coal-fired power plant equipped with a seawater flue-gas desulfurization system].

A field experiment was conducted to study mercury (Hg) bioaccumulation in Crassostrea sp. exposed to waste seawater discharged from a coal-fired power plant equipped with a flue gas desulfurization system. Oysters were cultured in the discharge outlet of the power plant (studying site) and a control site, respectively. The total Hg (THg) concentrations (all counted as dry weight) of seawater in the studying and control sites were determined as (120.6 +/- 55.5) ng x L(-1) (n = 5) and (2.7 +/- 1.0) ng x L(-1) (n = 5), respectively, while methyl Hg (MeHg) concentrations were (0.30 +/- 0.44) ng x L(-1) (n = 5) and (0.28 +/- 0.31) ng x L(-1) (n = 5), respectively. The THg in oyster at the studying site increased dramatically from (138.3 +/- 14.3) ng x g(-1) (n = 6) to (3 012 +/- 289) ng x g(-1) (n = 6) within 7 d, and remained at high levels of 2 935-4 490 ng x g(-1) for the next 34 d. In contrast, the THg in oyster at the control site showed no significant change, and kept at low levels of 60.7-137.5 ng x g(-1). After 41 d exposure, the MeHg in oyster at the studying site had no significant change, ranging from 55.4 ng x g(-1) to 73.1 ng x g(-1), and the content at the control site showed a slight decrease, ranging from 15.6 to 55.6 ng x g(-1). The study showed that THg in the waste seawater discharged at the coal-fired power plant could be quickly bioaccumulated by oyster to a great extent, the potential risk can thus not be ignored. MeHg concentration in the waste seawater was quite low, and no obvious bioaccumulation was found in oyster. Under the study conditions, no self-synthesis of MeHg or transformation of inorganic Hg into MeHg was found.

Electrochemical removal of chromium from aqueous solutions using electrodes of stainless steel nets coated with single wall carbon nanotubes.

An electrochemical technique was adopted to investigate the removal of Cr(VI) species and total chromium (TCr) from aqueous solution at a laboratory scale. The electrodes of stainless steel nets (SSNE) coated with single wall carbon nanotubes (SWCNTs@SSNE) were used as both anode and cathode. Three parameters, including solution pH, voltage and electrolyte concentration, were studied to explore the optimal condition of chromium removal. The optimal parameters were found to be pH 4, voltage 2.5 V and electrolyte concentration 10 mg/L. Under these conditions, the Cr(VI) and TCr removal had a high correlation with the amount of SWCNTs coated on the electrodes, with coefficients of the regression equations 0.953 and 0.928, respectively. The mechanism of Cr(VI) removal was also investigated. X-ray photoelectron spectroscopy (XPS) study and scanning electron microscope (SEM) picture showed that the process of chromium removal involved the reduction of Cr(VI) to Cr(III) on the cathode, and then the adsorption of Cr(III) by SWCNTs on the cathode. The study results indicated that the proposed method provided an interesting means to remove chromium species from aqueous solution, especially Cr(VI) in acidic condition.

[Production and consumption of dimethyl sulfur compounds by three typical algae].

By the method of inhibitor amendment, this paper estimated the production and consumption of dimethyl sulfur compounds by Skeletonema costatum, Phaeocystis sp. and Prorocentrum donghaiense in their different growth phases. The results indicated that throughout the whole growth period of the three algae, particle dimethylsulfoniopropionate (DMSPp) and dimethylsulfoxide (DMSOp) were net consumed. The concentrations of dissolved dimethylsulfoniopropionate (DMSPd) and dimethylsulfoxide (DMSOd) were mainly affected by the processes of algal production and bacterial and virus consumption, and thus, could reflect their production or consumption rates in the growth period of algae. Dimethylsulfide (DMS) was net produced in the whole growth period of the algae. There was a greater difference in the production and consumption of dimethyl sulfur compounds for the same alga in its different growth phases and for different algae in the same growth phase, indicating that both the physiology and the inter-species difference of algae had effects on the production and consumption of dimethyl sulfur compounds.