Storage and hydrolysis of seawater samples for inorganic carbon isotope analysis

Preservation of seawater samples was tested for total inorganic carbon (ΣCO2), stable carbon isotope (δ13C), and radiocarbon (14C) applications using foil bags and storage by refrigeration and freezing. The aim was to preserve representative samples with minimal storage effects but without using toxic methods such as mercuric chloride poisoning. Hydrolysis of samples to CO2 was based on existing methods. Results of IAEA-C2 standard used with deionized water stored in the foil bags showed complete reaction yields, 14C results within 2σ of the consensus value, and δ13C that were internally consistent, indicating that there were no procedural effects associated with the foil bags. 14C results were statistically indistinguishable across the storage times, for frozen and refrigerated seawater samples from a coastal site, Elie Ness, Fife, UK. The scatter of ΣCO2 concentrations and δ13C was within scatter observed in other studies for lake- and seawater samples preserved by acidification or using mercuric chloride. However, both ΣCO2 and δ13C were less variable for frozen samples compared with refrigerated samples. The foil bags are lighter, safer to transport, and similar in cost to glass bottles and allow sample collection in the field and transfer to the hydrolysis vessel without exposure of the sample to atmosphere. Storage of seawater samples in the foil bags was considered a reliable, alternative method to poisoning for ΣCO2, δ13C, and 14C, and freezing the samples is recommended for storage time beyond a week

Fluorescence spectroscopy applied to the optimisation of a desalting step by electrodialysis for the characterisation of marine organic matter

The isolation and characterisation of marine dissolved organic matter (DOM) are still not readily achieved today. The study of this chemically complex material is particularly difficult, especially as it is hindered by the high salinity of seawater. It is therefore essential to develop a method in which a sufficient quantity of marine organic matter can be collected for structural analyses. Reverse osmosis (RO) is often used for the concentration of DOM from freshwaters, due to the fact that DOM is not modified during RO and that DOC recoveries are high (about 80%). Unfortunately, RO cannot be used directly to isolate marine DOM,since both salts and organic matter are concentrated during the process. Therefore, marine samples have to be desalted before their concentration by RO. Our aim was to develop a desalting step of seawater by electrodialysis (ED), whilst minimising DOM modifications and losses. The process was first developed with small volumes (2 L) of artificial and Mediterranean seawater and was then applied to larger volumes.We showed that 20 L of Mediterranean seawater could be rapidly desalted (in less than 7 h) and, by monitoring the quality of DOM in desalted subsamples collected during ED using spectrofluorometry, that the quality of DOM was not significantly modified. It was concluded that desalted samples were still representative of the initial seawater samples. It should be noted, however, that care has to be taken in choosing the ratio of the volume of water to be desalted over the membrane surface area in order to limit DOM modifications and losses. Electrodialysis efficiently removed up to 75% of the salts present in the seawater samples whilst recovering most of unaltered DOM. ED and RO could then be combined in order to isolate, concentrate and characterise marine organic matter

Effects of external environments on the short beam shear strength of filament wound graphite/epoxy

Filament wound graphite/epoxy samples were immersed in seawater, deionized water, and toluene at room temperature and 80 deg C for 5, 15, and 43 days, and in methanol at room temperature for 15 and 43 days. The percent weight gains and short beam shear strengths were determined after environmental exposure. Samples immersed in deionized water and seawater had higher percent weight gains than those immersed in toluene at room temperature and 80 deg C. The percent weight gains for samples immersed in methanol at room temperature were comparable to those of deionized water and seawater immersed samples. A comparison of percent decreases in short beam shear strengths could not be made due to a large scatter in data. This may indicate defects in samples due to machining or variations in material properties due to processing

High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry

A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2 L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a Pb-207-Pb-204 double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28 +/- 21 pg(1sd) and typical Pb recoveries of 40-60%. The Pb concentrations are determined by isotope dilution (ID) on 50 mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about +/- 1to +/- 10%(1sd) for Pb concentrations of between 7 and 50 pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12 +/- 4 pg; 1sd). For the Pb isotope analyses, typical reproducibilities (+/- 2sd) of 700-1500 ppm and 1000-2000ppm were achieved for Pb-207/Pb-206, Pb-208/Pb-206 and Pb-206/Pb-204, Pb-207/Pb-204, Pb-208/Pb-204, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor Pb-204 isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the Pb-206/Pb-204 ratios are well correlated with Pb-207/Pb-206, underlining the significant improvement achieved in the measurement of the minor Pb-204 isotope

Persistent organic pollutants in the Atlantic and southern oceans and oceanic atmosphere

Persistent organic pollutants (POPs) continue to cycle through the atmosphere and hydrosphere despite banned or severely restricted usages. Global scale analyses of POPs are challenging, but knowledge of the current distribution of these compounds is needed to understand the movement and long-term consequences of their global use. In the current study, air and seawater samples were collected Oct. 2007–Jan. 2008 aboard the Icebreaker Oden en route from Göteborg, Sweden to McMurdo Station, Antarctica. Both air and surface seawater samples consistently contained α-hexachlorocyclohexane (α-HCH), γ-HCH, hexachlorobenzene (HCB), α-Endosulfan, and polychlorinated biphenyls (PCBs). Sample concentrations for most POPs in air were higher in the northern hemisphere with the exception of HCB, which had high gas phase concentrations in the northern and southern latitudes and low concentrations near the equator. South Atlantic and Southern Ocean seawater had a high ratio of α-HCH to γ-HCH, indicating persisting levels from technical grade sources. The Atlantic and Southern Ocean continue to be net sinks for atmospheric α-, γ-HCH, and Endosulfan despite declining usage

Effects of seawater and deionized water at 0 to 80 deg C on the flexural properties of a glass/epoxy composite

The effect on the flexural properties of a glass/epoxy composite of immersion in deionized water or seawater at 0, 25, and 80 C for 451 hr was examined. The percent weight gain at 0 and 25 C was low (0.06 to 0.17 percent) and there was no significant change in the flexural properties for these environmental conditions. At 80 C there was a decrease in the flexural strength of 17 and 20 percent in seawater and deionized water, respectively. This is a comparison to control samples exposed to 80 C heat alone. These decreases were found to be nearly reversible once the samples were dried. Optical microscopy did not reveal cracking of the matrix. The flexural modulus was essentially unaffected by exposure to deionized water and seawater at 80 C

Rare earth elements in Andaman Island surface water : geochemical tracers for the monsoon

The Asian summer monsoon affects the lives of billions of people. With the aim of identifying geochemical tracers for the monsoon related freshwater input from the major rivers draining into the Bay of Bengal and Andaman Sea we have taken surface seawater samples from various locations up and down the Andaman Islands during 2011. Importantly, in some locations samples have been taken in March, July and November, covering most of a seasonal cycle and different monsoon phases. Samples were collected from the side of small wooden boats or while swimming and were filtered within a few hours at 0.45 or 0.22 microns using the vacuum produced by a water jet or a hand operated peristaltic pump. Filtered and unfiltered samples were acidified to < pH 2 and analysed for Y and the REEs with an automated online preconcentration ICP-MS technique [1]. The local input of REEs from streams and sediment rich areas such as mangrove environments is clearly identified by middle REE enrichments in the shale normalised patterns of some samples. These middle REE bulges accompany large increases in dissolved REE concentrations at some locations, especially for the July samples obtained during the peak monsoon season with frequent storms. Y/Ho fractionation aslo occurs during the local input of dissolved REEs with affected samples having lower Y/Ho ratios. Conversly, some samples, in particular those taken after heavy rainfall in March, show strong REE scavenging accompanied by the prefferential removal of dissolved light REEs and higher Y/Ho ratios. The time series at a location away from local input sources shows remarkably similar REE patterns and concentraions in March and July. Then in October-November, following the peak in monsoon river discharge, the dissolved REE concentration increases by almost a factor of 2. The notable exception to this seasonal pattern is the Ce anomally which is around 0.3 in March and November but 0.6 in July, implying less oxidative removal of Ce(IV) during the peak summer monsoon rains. With the exception of elevated dissolved Ce concentrations, the North Pacific Deep Water normalised REE patterns are similar to those reported for offshore samples from the Bay of Bengal and Andaman Sea [2]. These seawater normalised patterns are distinctive having a middle REE enriched arc with similar light and heavy REE values suggesting the input from large rivers in the region is traceable using seawater REE chemistry. [1] Hathorne et al. (2012), Online preconcentration ICP-MS analysis of rare earth elements in seawater, Geochem. Geophys. Geosyst., 13, Q01020, doi:10.1029/2011GC003907. [2] Amakawa et al. (2000), Geochim. Cosmochim. Acta 64, 1715-1727

Polychlorinated biphenyls in air and water of the North Atlantic and Arctic Ocean.

Air and seawater samples were collected on board the R/V Polarstern during a scientific expedition from Germany to the Arctic Ocean during June–August 2004. The air data show a strong decline with latitude with the highest polychlorinated biphenyl (PCB) concentrations in Europe and the lowest in the Arctic. ΣICES PCBs in air range from 100 pg m−3 near Norway to 0.8 pg m−3 in the Arctic. A comparison with other data from previous and ongoing land-based air measurements in the Arctic region suggests no clear temporal decline of PCBs in the European Arctic since the mid-1990s. Dissolved concentrations of Σ6PCBs (28/31, 52, 101, 118, 138, 153) in surface seawater were <1 pg L−1. Dominant PCBs in seawater were 28/31 and 52 (0.1–0.44 pg L−1), with PCBs 101, 118, and 138 < 0.1 pg L−1. In seawater, PCB 52 displayed the highest concentrations in the northernmost samples, while PCBs 101, 118, and 138 showed slightly decreasing trends with increasing latitude. Fractionation was observed for PCBs in seawater with the relative abundance of PCBs 28 and 52 increasing and that of the heavier congeners decreasing with latitude. However, in air only 15–20% of the variability of atmospheric PCBs can be explained by temperature. Owing to large uncertainties in the Henry's Law constant (HLC) values, fugacity quotients for PCBs were estimated using different HLCs reported in the literature. These indicate that on average, deposition dominates over volatilization for PCBs in the Arctic region with a strong increase in the middle of the transect near the marginal ice zone (78–79°N). The increase in fugacity ratio is mainly caused by an increase in air concentration in this region (possibly indirectly caused by ice melting being a source of PCBs to the atmosphere)

Vibrio vulnificus and Vibrio parahaemolyticus in Oysters under Low Tidal Range Conditions: Is Seawater Analysis Useful for Risk Assessment?

Human-pathogenic Vibrio bacteria are acquired by oysters through filtering seawater, however, the relationships between levels of these bacteria in measured in oysters and overlying waters are inconsistent across regions. The reasons for these discrepancies are unclear hindering our ability to assess if -or when- seawater samples can be used as a proxy for oysters to assess risk. We investigated whether concentrations of total and human pathogenic Vibrio vulnificus (vvhA and pilF genes) and Vibrio parahaemolyticus (tlh, tdh and trh genes) measured in seawater reflect concentrations of these bacteria in oysters (Crassostrea virginica) cultured within the US lower Chesapeake Bay region. We measured Vibrio spp. concentrations using an MPN-qPCR approach and analyzed the data using structural equation modeling (SEM). We found seawater concentrations of these bacteria to predictably respond to temperature and salinity over chlorophyll a, pheophytin or turbidity. We also inferred from the SEM results that Vibrio concentrations in seawater strongly predict their respective concentrations in oysters. We hypothesize that such seawater-oyster coupling can be observed in regions of low tidal range. Due to the ease of sampling and processing of seawater samples compared to oyster samples, we suggest that under low tidal range conditions, seawater samples can foster increased spatial and temporal coverage and complement data associated with oyster samples