Automated high resolution determination of the trace elements iron and aluminium in the surface ocean using a towed Fish coupled to flow injection analysis (original) (raw)
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Journal of Environmental Monitoring, 2000
An overview is presented of sampling techniques and¯ow injection analysis (FIA) methods for low concentrations of Fe, Mn and Al in ®ltered seawater. On the basis of sampling procedures, ®ltration techniques, accuracy, blanks, detection limits, intercalibration results and oceanographic consistency, the feasibility of these FIA methods was evaluated. It was found that these metals could be measured on board with a minimum risk of contamination and with good accuracy even at low subnanomolar levels (v0.5 nM). Results for reference seawater were in the case of Fe-FIA and Mn-FIA in excellent agreement with the certi®ed values. Data from samples analyzed by Fe-FIA and by cathodic stripping voltametry (CSV) compared well, as did Mn-FIA and GFAAS. All three methods gave results that were mostly in good agreement with data from the same ocean regions published by other research groups. Two different types of surface water sampling were also tested and compared, namely conventional hand ®lling of a sample bottle from a rubber dinghy away from the ship, and underway pumping of seawater using a`tow ®sh'. The latter method gave the best results. Also, conventional membrane ®ltration and cartridge ®ltration for large volume ®ltration were compared using Fe and Al data from water column samples. Good agreement was found for both ®lter types, although for de®ning dissolved metal species the latter ®lter type was preferred.
Marine Chemistry, 2007
Dissolved Fe, Mn and Al concentrations (dFe, dMn and dAl hereafter) in surface waters and the water column of the Northeast Atlantic and the European continental shelf are reported. Following an episode of enhanced Saharan dust inputs over the Northeast Atlantic Ocean prior and during the cruise in March 1998, surface concentrations were enhanced up to 4 nmol L − 1 dFe, 3 nmol L − 1 dMn and 40 nmol L − 1 dAl and returned to 0.6 nmol L − 1 dFe, 0.5 nmol L − 1 dMn and 10 nmol L − 1 dAl towards the end of the cruise three weeks later. A simple steady state model (MADCOW, [Measures, C.I., Brown, E.T., 1996. Estimating dust input to the Atlantic Ocean using surface water aluminium concentrations. In: Guerzoni. S. and Chester. R. (Eds.), The impact of desert dust across the Mediterranean, Kluwer Academic Publishers, The Netherlands, pp. 301-311.]) was used which relies on surface ocean dAl as a proxy for atmospheric deposition of mineral dust. We estimated dust input at 1.8 g m − 2 yr − 1 (range 1.0-2.9 g m − 2 yr − 1 ) and fluxes of dFe, dMn and dAl were inferred. Mixed layer steady state residence times for dissolved metals were estimated at 1.3 yr for dFe (range 0.3-2.9 yr) and 1.9 yr for dMn (range 1.0-3.8 yr). The dFe residence time may have been overestimated and it is shown that 0.2-0.4 yr is probably more realistic. Using vertical dFe versus Apparent Oxygen Utilization (AOU) relationships as well as a biogeochemical two end member mixing model, regenerative Fe:C ratios were estimated respectively to be 20 ± 6 and 22 ± 5 μmol Fe:mol C. Combining the atmospheric flux of dFe to the upper water column with the latter Fe:C ratio, a 'new iron' supported primary productivity of only 15% (range 7%-56%) was deduced. This would imply that 85% (range 44-93%) of primary productivity could be supported by regenerated dFe. The open ocean surface data suggest that the continental shelf is probably not a major source of dissolved metals to the surface of the adjacent open ocean. Continental shelf concentrations of dMn, dFe, and to a lesser extent dAl, were well correlated with salinity and express mixing of a fresher continental end member with Atlantic Ocean water flowing onto the shelf. This means probably that diffusive benthic fluxes did not play a major role at the time of the cruise.
Journal of Geophysical Research, 1993
Lead and aluminum were measured with a 40-100 km resolution in surface water on two transects across the Ariantic Ocean, one in May 1990 from Cape Town to the North Sea, the other in November 1990 from the North Sea to the Strait of Magellan. Samples were drawn 14 m below surface at normal speed from a 2-m-long snorkel system mounted on the bottom of the ship directly into a clean-room area. In the tropics, both Pb and A1 show maximum concentrations in the Intertropical Convergence Zone (rrcz) correlated with each other and with minimum salinities, indicating wet deposition as their common source. Even in this area characterized by large inputs of mineral aerosols, the Pb/AI ratio shows that the major source of soluble lead (>95%) is anthropogenic. At higher latitudes, AI is low throughout (10-20 nmol/kg), whereas enhanced Pb values show the anthropogenic inputs off south Africa, northern Argentina and especially western Europe. Very low Pb and especially A1 concentrations in the upwelling areas associated with the Canary and Benguela currents show that the enhanced biogenic particle fluxes cause an efficient scavenging of both lithogenic particles known to arrive here by dry deposition, and of the adhering reactive trace metals.
Rapid and noncontaminating sampling system for trace elements in global ocean surveys
Limnology and Oceanography: Methods, 2012
The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. Indeed, the new GEOTRACES program www.GEOTRACES.org) is seeking to do just this-examine the global distributions of trace elements and isotopes in the world's oceans and reveal the processes that affect/control them. However to do this on the scale of an ocean basin, sampling equipment and protocols that can quickly take representative (i.e., corresponding to the hydrography) and uncontaminated samples for the full water column on ocean basin sections are essential. Given that many countries and scientists will be undertaking the GEOTRACES' surveys, cost and reliability are additional considerations. The "traditional" method of taking samples for TEIs (e.g., Bruland et al. 1979) used individual GO-FLO bottles hung on a Kevlar cable and triggered with plastic messengers; while successful, it is clearly too slow for global surveys. Early attempts at speeding up sampling for selected TEIs used coated stainless steel rosettes and conducting metal or Kevlar cables (e.g., Hunter et al. 1996; Löscher et al. 1998). More recently, the all titanium and conducting Kevlar cable system called "TITAN" was specially built and deployed for the GEOTRACES program and takes uncontaminated samples for all TEIs tested to date (De Baar et al. 2008).
Iron distributions in surface waters of the south Atlantic
Marine Chemistry, 1995
Total dissolvable iron in surface waters of the south Atlantic was measured using a flow injection analytical system with chemiluminescent detection and preconcentration onto 8-hydroxyquinoline resin. Surface water iron concentrations range from less than 0.5 nM to 10 nM. Results indicate that very high iron concentrations in the surface seawater are possible due to high atmospheric input and upwelling. The dual input mechanism is supported by correlations with Al, particulate matter and nutrients.
Marine Chemistry, 2005
A sensitive method for iron determination in seawater has been adapted on a submersible chemical analyser for in situ measurements. The technique is based on flow injection analysis (FIA) coupled with spectrophotometric detection. When direct injection of seawater was used, the detection limit was 1.6 nM, and the precision 7%, for a triplicate injection of a 4 nM standard. At low iron concentrations, on line preconcentration using a column filled with 8-hydroxyquinoline (8HQ) resin was used. The detection limit was 0.15 nM (time of preconcentration = 240 s), and the precision 6%, for a triplicate determination of a 1 nM standard, allowing the determination of Fe in most of the oceanic regimes, except the most depleted surface waters. The effect of temperature, pressure, salinity, copper, manganese, and iron speciation on the response of the analyser was investigated. The slope of the calibration curves followed a linear relation as a function of pressure (Cp = 2.8 × 10− 5P + 3.4 × 10− 2 s nmol− 1, R2 = 0.997, for Θ = 13 °C) and an exponential relation as a function of temperature (CΘ = 0.009e0.103Θ, R2 = 0.832, for P = 3 bar). No statistical difference at 95% confidence level was observed for samples of different salinities (S = 0, 20, 35). Only very high concentration of copper (1000 × [Fe]) produced a detectable interference. The chemical analyser was deployed in the coastal environment of the Bay of Brest to investigate the effect of iron speciation on the response of the analyser. Direct injection was used and seawater samples were acidified on line for 80 s. Dissolved iron (DFe, filtered seawater (0.4 μm), acidified and stored at pH 1.8) corresponded to 29 ± 4% of Fea (unfiltered seawater, acidified in line at pH 1.8 for 80 s). Most of Fea (71 ± 4%) was probably a fraction of total dissolvable iron (TDFe, unfiltered seawater, acidified and stored at pH 1.8).
Marine Chemistry, 2007
Aerosol (soluble and total) iron and water-column dissolved (DFe, b 0.2 μm) and total dissolvable (TDFe, unfiltered) iron concentrations were determined in the Canary Basin and along a transect towards the Strait of Gibraltar, in order to sample across the Saharan dust plume. Cumulative dust deposition fluxes estimated from direct aerosol sampling during our one-month cruise are representative of the estimated deposition fluxes based on near surface water dissolved aluminium concentrations measured on board. Iron inventories in near surface waters combined with flux estimates confirmed the relatively short residence time of DFe in waters influenced by the Saharan dust plume (6-14 months). Enhanced near surface water concentrations of DFe (5.90-6.99 nM) were observed at the Strait of Gibraltar mainly due to inputs from metal-rich rivers. In the Canary Basin and the transect towards Gibraltar, DFe concentrations (0.07-0.76 nM) were typical of concentrations observed in the surface North Atlantic Waters, with the highest concentrations associated with higher atmospheric inputs in the Canary Basin. Depth profiles showed that DFe and TDFe were influenced by atmospheric inputs in this area with an accumulation of aeolian Fe in the surface waters. The sub-surface minimum of both DFe and TDFe suggests that a simple partitioning between dissolved and particulate Fe is not obvious there and that export may occur for both phases. At depths of around 1000-1300 m, both regeneration and Meddies may explain the observed maximum. Our data suggest that, in deep waters, higher particle concentrations likely due to dust storms may increase the scavenging flux and thus decrease DFe concentrations in deep waters.