Organic Compounds In Seawater Research Articles

Removal of phenol in seawater by heterogeneous photocatalysis using activated carbon materials modified with TiO2

In this work composites based on Activated Carbon (AC) and TiO2 were synthesized by sol-gel method (containing 10 and 20 of TiO2, w%) using glycerol as source of carbon. These materials were used as photocatalysts for the removal of phenol in seawater. The photocatalysts were characterized by: Adsorption-Desorption of N2, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Infrared Spectroscopy (FTIR), and X-Ray Photoelectronic Spectroscopy (XPS). The photocatalytic test were carried out under UV-C light (254 nm) and Visible light (320−700 nm). The AC-TiO2 composites showed a high surface area, in special AC which reported 1900 (m2. g−1). The TiO2 contained in the composites corresponds to the crystalline form of Anatase. The addition of TiO2 to AC sensitized the material. The AC-TiO2 composites are good photocatalyst for the removal of phenol in seawater, they were superior to the commercial TiO2 (in both situation: under UV and Visible light). The presence of salts of seawater did not affect the heterogeneous photocatalysis under UV light, significantly; moreover, it was benefic under Visible light. In the photocatalysis, the best AC-TiO2 composite removed up to 70 mg of phenol.gcat−1 under UV-C light, and 55 mg of phenol.gcat−1 under Visible light. According to our results, the AC-Ti composites showed promising properties for applications in the removal of organic compounds in seawater. The mechanism, photocatalyst reuse, the effect of scavenger and seawater salts are discussed.

Adsorption and fractionation of Pt, Pd and Rh onto inorganic microparticles and the effects of macromolecular organic compounds in seawater

Adsorption and fractionation of Pt, Pd and Rh (defined here as platinum group elements, PGEs) onto the representative inorganic microparticles, including Fe2O3, MnO2, CaCO3, SiO2, Al2O3 and kaolinite in seawater were investigated. The effects of macromolecular organic compounds (MOCs) as the representatives of organic matter, including humic acids (HA), bovine serum albumin (BSA) and carrageenan, on the adsorption were also studied considering that organic matter is ubiquitous in seawater and indispensable to marine biogeochemical cycles. In the absence of MOCs, the representative mineral particles Fe2O3 and MnO2 had the strongest interaction with PGEs. The adsorption of PGEs onto the representative biogenic particles SiO2 and CaCO3 and lithogenic particles Al2O3 and kaolinite was similar or weaker than onto the mineral particles. MOCs inhibited the interaction between PGEs and the particles except for Pt and Pd onto the biogenic particles in artificial seawater. This impediment may be closely related to the interaction between particles, MOCs and elements. The partition coefficient (log Kd) of Pt was similar (∼4.0) in the presence of MOCs, indicating that the complexation between Pt and MOCs was less important than hydrolysis or adsorption onto the acid oxide particle surface. Rh tended to fractionate onto the mineral and lithogenic particles in the presence of HA and carrageenan, while Pd was more likely to fractionate onto the biogenic particles. However, BSA enhanced the fractionation tendency of Pd onto the mineral particles. The results indicate that the adsorption behavior of Pd onto inorganic particles was significantly affected by the composition or the type of MOCs. Hence, the interaction between PGEs and inorganic particles may be greatly affected by the macromolecular organic matter in the ocean.

Segmented flow coil equilibrator coupled to a proton-transfer-reaction mass spectrometer for measurements of a broad range of volatile organic compounds in seawater

Abstract. We present a technique that utilises a segmented flow coil equilibrator coupled to a proton-transfer-reaction mass spectrometer to measure a broad range of dissolved volatile organic compounds. Thanks to its relatively large surface area for gas exchange, small internal volume, and smooth headspace–water separation, the equilibrator is highly efficient for gas exchange and has a fast response time (under 1 min). The system allows for both continuous and discrete measurements of volatile organic compounds in seawater due to its low sample water flow (100 cm3 min−1) and the ease of changing sample intake. The equilibrator setup is both relatively inexpensive and compact. Hence, it can be easily reproduced and installed on a variety of oceanic platforms, particularly where space is limited. The internal area of the equilibrator is smooth and unreactive. Thus, the segmented flow coil equilibrator is expected to be less sensitive to biofouling and easier to clean than membrane-based equilibration systems. The equilibrator described here fully equilibrates for gases that are similarly soluble or more soluble than toluene and can easily be modified to fully equilibrate for even less soluble gases. The method has been successfully deployed in the Canadian Arctic. Some example data from underway surface water and Niskin bottle measurements in the sea ice zone are presented to illustrate the efficacy of this measurement system.

Assessment of the Current State of the Caspian Sea and the Caspian Seal Habitat Analysis

This article is devoted to the determination of heavy metals and harmful organic compounds in sea water – the habitat of the Caspian seal. The group of the most common heavy metals, according to many authors, includes manganese, nickel, zinc, iron, cadmium, lead, copper and their salts, characterized by long-term preservation and accumulation in water, sediments and hydrobionts. The studies were conducted from February 7–12, 2017 on the route from the Kalamkas (Kazakhstan) field through the islands of Kulaly to the village of Bautino. Water samples were taken 10‒20 cm below the sea ice and surface level, each sample was taken in 2 replicates: one for the Kazakhstan laboratory in Almaty and one for the French independent laboratory. Water samples were analyzed for the content of 13 heavy metals such as – Co, Cu, Ti, Bi, Ag, V, Al, Be, Sb, Sn, Fe, Cr, Mo. It was established that in all water samples the content of vanadium exceeds the maximum permissible concentration (MPC) level by 1.5–7.4 times, beryllium ‒ 140–445 times, antimony 13.2–17.2 times. The maximum concentrations of the V and Be contents were found in water samples taken at sampling points No. 1 and 2, and Sb ‒ at points No. 1.6, 7.8. Cobalt, copper, iron and chromium were not detected in the samples presented. The content of other metals (Ti, Bi, Ag, Al, Sn, Mo) was significantly below the permissible levels or below the detection limits of the method. All samples of sea water are contaminated by several organic chemical pollutants, to various degrees and from different origins. Data on the accumulation of petroleum hydrocarbons and heavy metals in the habitat of Caspian seals characterize the toxicological situation in the study region.

Evaluation of polar organic chemical integrative and hollow fibre samplers for the determination of a wide variety of organic polar compounds in seawater

The calibration of two passive samplers for the determination of 20 emerging organic compounds in seawater is described in this work: i) a new version of polar organic chemical integrative sampler (POCIS) containing 100 mg of mixed-mode anion exchanger (Strata X-AW) and 100 mg of polymeric HLB (Plexa) sorbent materials and using a highly porous Nylon membrane (30-μm pore size) and ii) polyethersulfone (PES) hollow fibre. Among the studied contaminants, herbicides, hormones, life style products (stimulants and artificial sweeteners), industrial chemicals (corrosion inhibitor and fluorinated compounds), personal care products and several pharmaceuticals were included. In the case of POCIS, both the sorbents and the Nylon membranes were extracted and analysed independently. The calibration set up consisted on a continuous-flow tank that was fed with a continuous flow of seawater (2 L/h) and a stock mixture of contaminants (20 mL/h), assuring a nominal concentration of ~ 600 ng/L (each analyte) in the tank. The uptake was linear in POCIS sorbent and Nylon membranes but exponential for PES hollow fibres. Furthermore, the highest sampling rates (Rs) values were obtained in POCIS sorbent (between 2.7 for acetaminophen and 491 mL/day for perfluoro-n-octanoic acid, PFOA) followed by Nylon membranes (between 3.6 for OBT and 50 mL/day for telmisartan) and the lowest were those from PES fibres (between 1.7 for bezafibrate and 157 mL/day for butylparaben). Additionally, five deuterated compounds ([2H5]-atrazine, [2H3]-amitriptyline, [2H7]-irbesartan, [2H3]-ketoprofen and [2H9]-progesterone) were studied as candidates for performance reference compounds (PRCs) in both POCIS and PES, and though [2H5]-atrazine, [2H9]-progesterone and [2H3]-amitriptyline showed acceptable results in the case of POCIS, only [2H5]-atrazine provided a good validation. In the case of PES fibres, the PRC corrections did not provide acceptable results due to a low dissipation of the PRCs. Finally, POCIS were deployed in two sites of the low part of the estuary of Bilbao (northern Spain) from where water samples were also taken and analysed. As a result, in addition to the overall good agreement between the passive and active samplings, passive samplers allowed the determination of several compounds that were below the detection limits in the active sampling.

Multi-residue analysis of legacy POPs and emerging organic contaminants in Singapore's coastal waters using gas chromatography–triple quadrupole tandem mass spectrometry

A gas chromatography–triple quadrupole mass spectrometry (GC–MS/MS) based method was developed for determination of 86 hydrophobic organic compounds in seawater. Solid-phase extraction (SPE) was employed for sequestration of target analytes in the dissolved phase. Ultrasound assisted extraction (UAE) and florisil chromatography were utilized for determination of concentrations in suspended sediments (particulate phase). The target compounds included multi-class hydrophobic contaminants with a wide range of physical–chemical properties. This list includes several polycyclic and nitro-aromatic musks, brominated and chlorinated flame retardants, methyl triclosan, chlorobenzenes, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). Spiked MilliQ water and seawater samples were used to evaluate the method performance. Analyte recoveries were generally good, with the exception of some of the more volatile target analytes (chlorobenzenes and bromobenzenes). The method is very sensitive, with method detection limits typically in the low parts per quadrillion (ppq) range. Analysis of 51 field-collected seawater samples (dissolved and particulate-bound phases) from four distinct coastal sites around Singapore showed trace detection of several polychlorinated biphenyl congeners and other legacy POPs, as well as several current-use emerging organic contaminants (EOCs). Polycyclic and nitro-aromatic musks, bromobenzenes, dechlorane plus isomers (syn-DP, anti-DP) and methyl triclosan were frequently detected at appreciable levels (2–20,000pgL−1). The observed concentrations of the monitored contaminants in Singapore's marine environment were generally comparable to previously reported levels in other coastal marine systems. To our knowledge, these are the first measurements of these emerging contaminants of concern in Singapore or Southeast Asia. The developed method may prove beneficial for future environmental monitoring of hydrophobic organic contaminants in marine environments. Further, the study provides novel information regarding several potentially hazardous contaminants of concern in Singapore's marine environment, which will aid future risk assessment initiatives.

A Smart Sensor System for Detecting Hydrocarbon Volatile Organic Compounds in Sea Water

Hydrocarbons are among the most dangerous pollutants for the marine environment. The creation of smart systems to detect hydrocarbon spills in the marine environment is often complex and involves many issues. This paper presents an innovative approach based on a sensor system capable of detecting volatile organic compounds (VOCs) produced by hydrocarbons. The system was composed of an array of photo ionization detectors, lodged in a flow chamber and arranged in radial symmetry, in order to receive the same amount of air flow. The air inlet was placed on the upper face of the chamber, while the air outlet was on the lower face. The sensor characterization at the laboratory bench was performed using different kinds of hydrocarbons, such as gasoline, diesel fuel, kerosene, and crude oil, and their response was acquired using a smart electronic system based on an Arduino™ electronic board. With this approach, it was possible to detect mild‐to‐high concentrations of VOCs with a portable, lightweight, smart system, placed in an autonomous underwater vehicle and in a moored buoy.

Antifouling strategies and corrosion control in cooling circuits

Biofouling and corrosion phenomena dramatically reduce the functionality of industrial cooling circuits, especially in marine environments. This study underlines the effectiveness of a low level chlorination treatment of seawater to prevent biological fouling and biocorrosion.Reported examples emphasize the reaction of chlorine with bromide, ammonia and organic compounds in seawater and the effectiveness of a treatment performed in such a way to guarantee a residual concentration lower than 3μM at the outlet of the condensers.In a brief review of antifouling strategies, alternatives to chlorination and the monitoring approach able to optimize the treatments are also reported.An integrated, on-line system based on electrochemical probes (Biox system and a linear polarization resistance probe) demonstrated to be sufficient to monitor in real time: corrosion, biofilm growth and chemical treatments based on chlorine or alternative oxidant products (chlorine dioxide, etc.).A careful electrochemical monitoring and the optimized treatments help the plant operators of industrial cooling circuits prevent the decay of the equipment performance, allowing at the same time the control of the halogenated by-products formation.

Inhibition effect of newly synthesised piperidine derivatives on the corrosion of brass in natural seawater

The piperidine derivatives, namely (4-hydrazono-3-Methyl-2,6-diphenyl-piperidin-1-yl)-ethanoic acid hydrazide (HMDPEH), 5-(2,6-Diphenyl-3-methyl-4-hydrazono-piperidin-1-ylmethyl)-3H-[1,3,4]oxadiazole-2-thione (DMHPOT) and 4-Amino-5-(2,6-diphenyl-3-methyl-4-hydrazono-piperidin1-ylmethyl)-4H-[1,2,4]triazole-3-thiol (ADMHPTT) were synthesised. The inhibiting effect of these compounds on the corrosion of brass in natural seawater was studied using potentiodynamic polarization studies and electrochemical impedance spectroscopic (EIS) measurements. The presence of these organic compounds in seawater suppresses both anodic and cathodic processes, and it is enhanced by the increase in the concentration of the inhibitors. The value of the activation energy (Ea) for the corrosion of brass was calculated and discussed. The structural and electronic parameters of these piperidine derivatives were calculated using computational methodologies. The surface morphology of the brass after its exposure to natural seawater with and without 10−3 M HMDPEH, DMHPOT and ADMHPTT were examined by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX).

Role of H2O2 in the photo-transformation of phenol in artificial and natural seawater

In previous works, it was observed that phenol photo-induced transformation in natural seawater (NSW) mediated by natural photosensitizers occurs and leads to the formation of numerous hydroxylated, condensed, halogenated and nitroderivatives. Irradiation of NSW added with phenol and iron species had provided the enhanced formation of several halophenols, suggesting a central role played by iron species on the phenol halogenation in marine water.In this paper, we focus on hydrogen peroxide, another key photosensitizer, and its interaction with iron species. The ability of Fe(II)/Fe(III) and H2O2 species to act as photo-sensitizers towards the transformation of organic compounds in seawater was investigated under simulated solar radiation.Light activation is necessary to induce the transformation of phenol, as no degradation occurs in the dark when either H2O2 or iron/H2O2 are initially added to artificial seawater (ASW). Fe(II) is easily transformed into Fe(III), assessing that a Fenton reaction (dark, Fe(II)/H2O2) does not take place in marine environment, in favour of a photo-activated reaction involving Fe(III) and H2O2.When NSW is spiked with H2O2 and Fe(III), halophenols' and nitrophenols' concentration decreases and completely disappears at high hydrogen peroxide concentration. Since Fe(II) and Fe(III) in spiked seawater induce an enhanced formation of haloderivatives, an excess of hydrogen peroxide act as scavenger towards the photo-produced chloro/bromo radicals, so hindering halogenation process in seawater. Hence, even if hydrogen peroxide efficiently induces the OH radical formation, and could then promote the phenol phototransformation, nevertheless it is negligibly involved in the production of the intermediates formed during phenol photolysis in seawater, whose formation is necessarily linked to other photosensitizer species.

Quantification of oxygenated volatile organic compounds in seawater by membrane inlet-proton transfer reaction/mass spectrometry

The role of the ocean in the cycling of oxygenated volatile organic compounds (OVOCs) remains largely unanswered due to a paucity of datasets. We describe the method development of a membrane inlet-proton transfer reaction/mass spectrometer (MI-PTR/MS) as an efficient method of analysing methanol, acetaldehyde and acetone in seawater. Validation of the technique with water standards shows that the optimised responses are linear and reproducible. Limits of detection are 27 nM for methanol, 0.7 nM for acetaldehyde and 0.3 nM for acetone. Acetone and acetaldehyde concentrations generated by MI-PTR/MS are compared to a second, independent method based on purge and trap-gas chromatography/flame ionisation detection (P&T-GC/FID) and show excellent agreement. Chromatographic separation of isomeric species acetone and propanal permits correction to mass 59 signal generated by the PTR/MS and overcomes a known uncertainty in reporting acetone concentrations via mass spectrometry. A third bioassay technique using radiolabelled acetone further supported the result generated by this method. We present the development and optimisation of the MI-PTR/MS technique as a reliable and convenient tool for analysing seawater samples for these trace gases. We compare this method with other analytical techniques and discuss its potential use in improving the current understanding of the cycling of oceanic OVOCs.

The effect of composition on the density of Indian Ocean waters

The conductivity and density was measured on samples collected in the Indian Ocean during the I9 Climate Variability and Predictability (CLIVAR) cruise. The relative densities ρ− ρ 0 were compared to those determined from the equation of state of seawater. The excess densities Δ ρ= ρ Meas− ρ Calc ranged from 0 in surface waters to 0.025 kg m −3 in deep waters due to additions of nutrients and carbonates. The values Δ ρ were found to be a linear function of the increases of TA, TCO 2, Si(OH) 4 and NO 3 in the deep waters ( σ=0.004−0.005 kg m −3). The correlations with changes in Si(OH) 4 gave the best estimates since the concentrations do not have a large effect on the conductivity. By combining the Indian and earlier Pacific measurements ( N=249), we have10 3Δ ρ/kg m −3=0.12+104ΔSi(OH) 4( σ=0.0041 kg m −3). These results indicate that the effect of changes in the composition of seawater for most of the world oceans can be estimated from the combined results in the Pacific and Indian oceans. The excess densities can also be accounted for by determining the change in the absolute salinity of seawater, defined as S A= S+Δ S, where S is the conductivity salinity and Δ S is equal to the mass of added nutrients and carbonates. S A can then be used in the equation of state to calculate the density ( σ=0.0041×10 −6 kg m −3). Measurements made on artificial seawater ( S=35) agree with the values determined from the equations of state, indicating that the dissolved organic compounds in seawater do not affect the conductivity to density relationships for real seawater. We recommended either S A or ΔSi(OH) 4 be used to estimate the changes in the density of seawater due to the addition of nutrients and carbonates to ocean waters.

Development and initial calibration of a portable laser-induced fluorescence system used for in situ measurements of trace plastics and dissolved organic compounds in seawater and the Gulf of Mexico.

A portable UV laser-induced fluorescence system that uses a high pulsed repetition frequency (8-kHz) microchip laser at 266 nm, 13 switchable optical filters, and a gated photomultiplier tube detector has been developed and tested successfully for the detection of leached plastics (possibly bisphenol-A) and trace dissolved organic compounds in seawater. The instrument is 100 times more sensitive than commercial portable spectrofluorometers and measures a complete fluorescence spectrum in a moderate time period of 1-2 min. The system was tested in the Gulf of Mexico over varying water masses. In addition, fluorescence lifetime, bleaching, and temporal flow characteristics were studied.

UV digestion of seawater samples prior to the determination of copper using flow injection with chemiluminescence detection

A purpose built UV digestion system was successfully used for the breakdown of Cu complexing organic ligands in seawater samples, prior to total dissolved Cu determination using flow injection with chemiluminescence detection (FI-CL) and on-line micro-column preconcentration/matrix removal. Residual dissolved organic carbon (DOC) was quantified using a DOC analyser. Humic acid (1.8–7.2 mg l −1 C) in ultra high purity (UHP) water was completely broken down within 4 h in all batch experiments (125 and 400 W lamps; with and without 15 mM H 2O 2 and, as expected, was more rapid with the 400 W lamp, in the presence of H 2O 2, and for lower humic acid concentrations. UV digestion experiments with seawater showed that the residual DOC concentration after batch UV treatment (4 h) was <0.08 mg l −1 C compared with >0.32 mg l −1 C after on-line irradiation (residence time 11.2 min). Therefore, the batch method was more efficient than on-line UV digestion at breaking down added humic acid and naturally present organic compounds in seawater. However, the release of Cu from metal complexing organic matter in seawater and estuarine water was the same using both on-line and batch UV digestion (sample irradiation residence time: 5.6 min and 8 h, respectively). UV digestion is, therefore, a contamination-free approach for seawater pretreatment prior to micro-column preconcentration and FI-CL determination of total dissolved Cu and should also be applicable to the selective determination of the total dissolved fractions of other trace metals in seawater (e.g. Co, Fe, Mn).

An automated purge and trap gas chromatography-mass spectrometry system for the sensitive shipboard analysis of volatile organic compounds in seawater

We developed an automated purge and trap unit connected to a gas chromatograph-mass spectrometer for shipboard determination of unstable volatile organic compounds in seawater. The device used a small column for the rapid desorption of adsorbed compounds, thus eliminating the need for post-desorption cryofocusing. The repeatability (relative standard deviation, RSD; n = 7) was typically < 5%. The detection limits were 0.1–4.3 pM for chloromethane, bromomethane, dichloromethane, iodomethane, dimethyl sulfide, iodoethane, isoprene, bromochloromethane, chloroform, tetrachloromethane, dibromomethane, bromodichloromethane, iodopropane, chloroiodomethane, dimethyl disulfide, dibromochloromethane, bromoform, and diiodomethane. To investigate the stability of seawater samples, we obtained a concentration-time profile of volatile organic compounds using this method during the incubation of a seawater sample with and without the addition of HgCl2 in the dark at 4°C. We found shipboard determination to be suitable and essential for the determination of unstable compounds such as dimethyl sulfide in seawater, as the concentration of dimethyl sulfide increased considerably during the incubation of a seawater sample both with and without the addition of HgCl2. This method permitted the assessment of numerous naturally produced volatile organic compounds that are considered to be important for the chemistry of seawater/atmosphere exchange in the ocean.

An automated purge and trap gas chromatography-mass spectrometry system for the sensitive shipboard analysis of volatile organic compounds in seawater

We developed an automated purge and trap unit connected to a gas chromatograph-mass spectrometer for shipboard determination of unstable volatile organic compounds in seawater. The device used a small column for the rapid desorption of adsorbed compounds, thus eliminating the need for post-desorption cryofocusing. The repeatability (relative standard deviation, RSD; n = 7) was typically < 5%. The detection limits were 0.1–4.3 pM for chloromethane, bromomethane, dichloromethane, iodomethane, dimethyl sulfide, iodoethane, isoprene, bromochloromethane, chloroform, tetrachloromethane, dibromomethane, bromodichloromethane, iodopropane, chloroiodomethane, dimethyl disulfide, dibromochloromethane, bromoform, and diiodomethane. To investigate the stability of seawater samples, we obtained a concentration-time profile of volatile organic compounds using this method during the incubation of a seawater sample with and without the addition of HgCl2 in the dark at 4°C. We found shipboard determination to be suitable and essential for the determination of unstable compounds such as dimethyl sulfide in seawater, as the concentration of dimethyl sulfide increased considerably during the incubation of a seawater sample both with and without the addition of HgCl2. This method permitted the assessment of numerous naturally produced volatile organic compounds that are considered to be important for the chemistry of seawater/atmosphere exchange in the ocean.

Fluorescent screening of phytoplankton and organic compounds in sea water.

The flow-through spectrofluorometers, FLUO-IMAGER, were developed to measure the abundance of phytoplankton, including the analysis of pigment composition and concentration of organic pollution and dissolved organic matter (DOM), in continuous mode. The measurements can be carried out without the time-consuming pretreatment of water samples. The analytical concept uses the technique of spectral fluorescent signatures (SFS), based on the systematized spectral library comprising the SFS of major phytoplankton species and chemical pollution. The SFS technique has been applied for several years in qualitative and quantitative screening of organic compounds and phytoplankton in the Baltic, North and Norwegian Seas. The results of the analysis of phytoplankton pigments, the dynamic processes of bloom development, DOM and oil pollution are presented.

A simple and sensitive method for the determination of volatile halogenated organic compounds in sea water in the amol l −1 to pmol l −1 range

Volatile halogenated organic compounds in sea water were determined in automated purge and trap systems connected to either a gas-chromatograph with an electron capture detector (GC–ECD), or a mass spectrometer (GC–MS). We show for the first time a miniaturised packed trap in combination with a narrow bore capillary column for the analysis of sea water. Detection limits of amol l −1 to fmol l −1 range for GC–ECD and fmol l −1 to pmol l −1 for GC–MS are achieved with a micro-trap filled with a porous polymer for water samples of 27 ml. The trap is cooled to moderate temperatures, +5°C to −10°C by means of circulating water. The repeatability (RSD) of the compounds determined in sea water were 4% or lower. The method was shown to facilitate the assessment of a number of naturally produced halocarbons important for the chemistry of the atmosphere, in the Arctic Ocean.

On-line flow injection analysis of volatile organic compounds in seawater by membrane introduction mass spectrometry

The combination of flow injection analysis with membrane introduction mass spectrometry for analysis of volatile organic compounds (VOCs) in seawater is examined and is compared to measurements made in water. Membrane introduction mass spectrometry is performed using a benchtop ion trap mass spectrometer, and characterization of various aspects of the flow injection and ion trap combination for the analysis of volatile organic compounds (including anthropogenic halocarbons) in seawater is carried out. The analyte responses are shown to be linear over several orders of magnitude (e.g. for methylene chloride), independent of seawater pH (e.g. for chlorobenzene) and independent of matrix effects for the VOCs studied. A comparison of the performance of a microporous (Teflon) membrane with that of an amorphous silicone membrane is made, and the former is shown to provide lower detection limits which are in the parts-per-trillion range (300 ppt for chlorobenzene, 190 ppt for trans-1,2-dichloroethene). The microporous membrane provides faster response times by a factor of four to five for relatively more polar compounds, such as chlorobenzene. An analysis of a seven-component mixture demonstrates the ability of this on-line combination to allow multicomponent analysis of mixtures of some complexity.

Morphological and Physiological Responses of Echinoderm Larvae to Nutritive Signals

SYNOPSIS. Echinoid larvae have been found previously to develop shorter arms as phytoplankton concentrations increase. In the present study, the skeletal dimensions of larvae of the sea urchins Lytechinus pictus and Strongylocentrotus purpuratus were measured after exposure to dissolved organic compounds in seawater. The presence of glucose or individual amino acids (at 1 or 2 μM), a mixture of 16 different amino acids (100 nM each), or algal exudate resulted in larvae with shorter arms (by 12 to 88%), relative to larvae in seawater with no additions. Larvae exposed to mixtures of amino acids also had changes in the constituents of their internal free amino acid pools (as determined by HPLC). For another echinoid, Dendraster excentricus, amino acid transport (T, from 500 nM) by individual larvae (n = 47) scaled to arm length (L) as follows: T = 2.06L0.81 (0.81 ± 0.26,95% confidence intervals). Mass (M) and metabolic rate (MR) did not scale in the same manner (as transport) to arm length for larvae of the echinoid Centrostephanus coronatus (MR = 148L1.51; M = 1.7L2.01). These characteristics may scale to arm length independently from transport rate under certain conditions. Larvae of echinoderms respond morphologically to “signals” in their environment that may indicate the availability of dissolved and paniculate nutrients. This in turn will have consequences for their ability to take up and metabolize these nutrients. The response may be mediated by surface receptors for dissolved organic compounds, or by changes in the sizes of intracellular substrate pools.