The unaccounted dissolved iron (II) sink: Insights from dFe(II) concentrations in the deep Atlantic Ocean.

Hydrothermal vent sites found along mid-ocean ridges are sources of numerous reduced chemical species and trace elements. To establish dissolved iron (II) (dFe(II)) variability along the Mid Atlantic Ridge (between 39.5°N and 26°N), dFe(II) concentrations were measured above six hydrothermal vent sites, as well as at stations with no active hydrothermal activity.

Increasing picocyanobacteria success in shelf waters contributes to long-term food web degradation.

Continental margins are disproportionally important for global primary production, fisheries and CO uptake. However, across the Northeast Atlantic shelves, there has been an ongoing summertime decline of key biota-large diatoms, dinoflagellates and copepods-that traditionally fuel higher tropic levels such as fish, sea birds and marine mammals. Here, we combine multiple time series with in situ process studies to link these declines to summer nutrient stress and increasing proportions of picophytoplankton that can comprise up to 90% of the combined pico- and nanophytoplankton biomass in coastal areas.

Uncertainty associated with the leaching of aerosol filters for the determination of metals in aerosol particulate matter using collision/reaction cell ICP-MS detection.

High quality observational data with a firm uncertainty assessment are essential for the proper validation of biogeochemical models for trace metals such as iron. Typically, concentrations of these metals are very low in oceanic waters (nM and sub nM) and ICP-MS is therefore a favoured technique for quantitative analysis. Uncertainties in the measurement step are generally well constrained, even at sub-nM concentrations.

Changes to polychlorinated biphenyl (PCB) signatures and enantiomer fractions across different tissue types in Guillemots.

Two Guillemot carcases were dissected, each providing 12 discrete tissue samples and 3 samples of partially digested food. One hundred and five PCBs from the 209 PCBs determined by GCxGC-ToFMS were detected. The relative proportions of individual PCBs did not vary greatly within tissue types, although the PCB profile from undigested food could be distinguished.

Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES.

Continental shelves and shelf seas play a central role in the global carbon cycle. However, their importance with respect to trace element and isotope (TEI) inputs to ocean basins is less well understood. Here, we present major findings on shelf TEI biogeochemistry from the GEOTRACES programme as well as a proof of concept for a new method to estimate shelf TEI fluxes.

Return of naturally sourced Pb to Atlantic surface waters.

Anthropogenic emissions completely overwhelmed natural marine lead (Pb) sources during the past century, predominantly due to leaded petrol usage. Here, based on Pb isotope measurements, we reassess the importance of natural and anthropogenic Pb sources to the tropical North Atlantic following the nearly complete global cessation of leaded petrol use. Significant proportions of up to 30-50% of natural Pb, derived from mineral dust, are observed in Atlantic surface waters, reflecting the success of the global effort to reduce anthropogenic Pb emissions.

Combined uncertainty estimation for the determination of the dissolved iron amount content in seawater using flow injection with chemiluminescence detection.

This work assesses the components contributing to the combined uncertainty budget associated with the measurement of the Fe amount content by flow injection chemiluminescence (FI-CL) in <0.2 m filtered and acidified seawater samples. Amounts of loaded standard solutions and samples were determined gravimetrically by differential weighing.

Can polychlorinated biphenyl (PCB) signatures and enantiomer fractions be used for source identification and to age date occupational exposure?

Detailed polychlorinated biphenyl (PCB) signatures and chiral Enantiomer Fractions (EFs) of CB-95, CB-136 and CB-149 were measured for 30 workers at a transformer dismantling plant. This was undertaken to identify sources of exposure and investigate changes to the PCB signature and EFs over different exposure periods. Approximately 1.

Iron stable isotopes track pelagic iron cycling during a subtropical phytoplankton bloom.

The supply and bioavailability of dissolved iron sets the magnitude of surface productivity for ∼ 40% of the global ocean. The redox state, organic complexation, and phase (dissolved versus particulate) of iron are key determinants of iron bioavailability in the marine realm, although the mechanisms facilitating exchange between iron species (inorganic and organic) and phases are poorly constrained. Here we use the isotope fingerprint of dissolved and particulate iron to reveal distinct isotopic signatures for biological uptake of iron during a GEOTRACES process study focused on a temperate spring phytoplankton bloom in subtropical waters.

Uncertainty contributions to the measurement of dissolved Co, Fe, Pb and V in seawater using flow injection with solid phase preconcentration and detection by collision/reaction cell-quadrupole ICP-MS.

A flow injection manifold incorporating a solid phase chelating resin (Toyopearl AF-Chelate-650) is reported for the preconcentration of dissolved metals from seawater, with a focus on investigating the effect of the loading pH, wash solution composition and wash time. Cobalt, iron, lead and vanadium have been used as target analytes with contrasting oceanographic behaviour. Quadrupole ICP-MS has been used for detection to make the approach accessible to most laboratories and a collision/reaction cell has been incorporated to minimise polyatomic interferences.

Identifying the provenance of Leach's storm petrels in the North Atlantic using polychlorinated biphenyl signatures derived from comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

PCB signatures can be used for source identification, exposure studies, age dating and bio-monitoring. This study uses comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-ToFMS) to produce a PCB signature comprised of over 80 PCBs for individual Leach's storm petrels (Oceanodroma leucorhoa). The Leach's storm petrel is a relatively small, elusive, understudied pelagic bird, which only returns to remote islands under darkness during the breeding season.

Seasonal ITCZ migration dynamically controls the location of the (sub)tropical Atlantic biogeochemical divide.

Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (∼0.

Fingerprinting polychlorinated biphenyls in environmental samples using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry.

A GC × GC-TOFMS installed with a Rtx-PCB (60 m × 0.18 mm × 0.18 μm) in the first dimension and Rxi- 17 (1.

Flow injection analysis as a tool for enhancing oceanographic nutrient measurements--a review.

Macronutrient elements (C, N and P) and micronutrient elements (Fe, Co, Cu, Zn and Mn) are widely measured in their various physico-chemical forms in open ocean, shelf sea, coastal and estuarine waters. These measurements help to elucidate the biogeochemical cycling of these elements in marine waters and highlight the ecological and socio-economic importance of the oceans. Due to the dynamic nature of marine waters in terms of chemical, biological and physical processes, it is advantageous to make these measurements in situ and in this regard flow injection analysis (FIA) provides a suitable shipboard platform.

Elucidating the structural properties that influence the persistence of PCBs in humans using the National Health and Nutrition Examination Survey (NHANES) dataset.

In human exposure studies involving Polychlorinated Biphenyls (PCBs), it is useful to establish when an individual was potentially exposed. Age dating PCB exposure is complex but assessments can be made because different PCB congeners have different residence times in the human body. The less chlorinated congeners generally tend to have shorter residence times because they are biotransformed and eliminated faster than more chlorinated congeners.

Nitrogen fixation and nitrogenase (nifH) expression in tropical waters of the eastern North Atlantic.

Expression of nifH in 28 surface water samples collected during fall 2007 from six stations in the vicinity of the Cape Verde Islands (north-east Atlantic) was examined using reverse transcription-polymerase chain reaction (RT-PCR)-based clone libraries and quantitative RT-PCR (RT-qPCR) analysis of seven diazotrophic phylotypes. Biological nitrogen fixation (BNF) rates and nutrient concentrations were determined for these stations, which were selected based on a range in surface chlorophyll concentrations to target a gradient of primary productivity. BNF rates greater than 6 nmolN l(-1) h(-1) were measured at two of the near-shore stations where high concentrations of Fe and PO(4)(3-) were also measured.

Elevated Fe(II) and dissolved Fe in hypoxic shelf waters off Oregon and Washington: an enhanced source of iron to coastal upwelling regimes.

There has been a growing interest in the cause and impact of hypoxic regions known as "dead zones" that have increasingly appeared along the west coast of the United States and have caused widespread destruction to the crab and fishing industry in this upwelling region. Here, we present results that demonstrate that the hypoxic conditions in the water column over the continental shelf result in a marked increase in iron(II) concentrations, which contribute to elevated dissolved and labile particulate iron concentrations. These elevated dissolved iron(II) concentrations result from two factors: (1) the hypoxic water column allows extremely elevated iron(II) concentrations in reducing porewaters to exist close to the sediment water interface, leading to an increased flux of iron(II) from the sediments; (2) the low oxygen, low pH, and low temperatures within the bottom boundary layer act in concert to markedly slow down the oxidation rate of Fe(ll).