Accuracy and precision of lead isotopic composition measurements in seawater (original) (raw)
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Geochimica Et Cosmochimica Acta, 1994
Stable lead isotopes are used to illustrate the impact of surface water circulation on dissolved lead distribution in North Atlantic surface waters during oligotrophic conditions. Using stable lead isotopic signatures from (1) the Sargasso Sea and (2) direct tropospheric deposition to the North Atlantic, we estimate that 10–40% of the lead accumulated in surface waters of the European Basin is transported from the western North Atlantic by the North Atlantic Current. South of 50°N, lead appears to be primarily distributed by the Subtropical North Atlantic Gyre that extends well beyond the western basins to 30°W in the North African Basin (at 30–40°N). There are different lead isotopic signatures between the subtropical gyre to the Guiana and western Guinea Basins, which suggests that the Inter Tropical Convergence Zone acts as an efficient barrier limiting chemical exchanges between the gyre and the equatorial currents.
Intercalibrated lead concentration measurements in the Atlantic Ocean
Deep Sea Research Part II: Topical Studies in Oceanography, 2001
Measurements of dissolved (50.22 mm) lead concentrations in seawater in samples collected on the third 1996 Intergovernmental Oceanographic Commission cruise (IOC III) in the Atlantic Ocean have been intercalibrated. This represents the first successful intercalibration (p50.05, paired t-test) of lead concentration measurements in the IOC's Global Investigation of Pollution in the Marine Environment (GIPME), which was designed to establish the baseline concentrations of trace elements in oceanic waters and the reproducibility of those measurements. #
A new method for stable lead isotope extraction from seawater
Analytica Chimica Acta, 2013
A new technique for stable lead (Pb) isotope extraction from seawater is established using Toyopearl AF-Chelate 650M ® resin (Tosoh Bioscience LLC). This new method is advantageous because it is semi-automated and relatively fast; in addition it introduces a relatively low blank by minimizing the volume of chemicals used in the extraction. Subsequent analyses by HR ICP-MS have a good relative external precision (2σ) of 0.35% for 206 Pb/ 207 Pb, while analyses by MC-ICP-MS have a better relative external precision of 0.06%. However, Pb sample concentrations limit MC-ICP-MS analyses to 206 Pb, 207 Pb, and 208 Pb. The method was validated by processing the common Pb isotope reference material NIST SRM-981 and several GEOTRACES intercalibration samples, followed by analyses by HR ICP-MS, all of which showed good agreement with previously reported values.
Marine Pollution Bulletin, 1998
For seawater, solvent extraction pre-concentration and the use of a micro-concentric nebulizer allowed 1 ml of concentrate to be measured for several minutes to achieve precisions in the range 0.5-1.2% relative standard deviation for 2°Spb/Z°6Pb and 2°Tpb/2°6Pb. The environmental dispersion of trace amounts of anthropogenic Pb produced distinctive Pb isotope ratio changes in seawater and marine sediments in the immediate vicinity of a Pb-Zn concentrate shipping facility. Concentrate was found to have 2°Spb/2°6pb ratios in the range 2.21-2.25, whereas environmental background 2°Spb/z°apb ratios were: filtered (<0.45 om) seawater, 2.13-2.15; unfiltered seawater, 2.06-2.10; sediment, 2.06-2.09. The combined Pb isotope ratio and concentration measurements by ICP-MS have provided a sensitive and cost effective monitoring tool allowing an una~abiguous assessment of the source of Pb.
Isotopic evidence of contaminant lead in the South Atlantic troposphere and surface waters
Deep-sea Research Part Ii-topical Studies in Oceanography, 2001
The third Intergovernmental Oceanographic Commission (IOC) Baseline Contaminant cruise (May–June 1996) has established the first lead isotopic compositions in the surface water and the atmosphere of the Equatorial and South Atlantic Ocean. These ratios have evidenced both anthropogenic and natural origins of lead along the cruise transect (from 33°S to 10°N). The isotopic gradients tentatively have been, attributed to aeolian as well as surface-water advective inputs from a suite of rather local and remote sources to the Southern Hemisphere. Relatively low 206Pb/207Pb ratios (x±sd) were encountered within the South Equatorial Current between 17°S and 5°S (1.156±0.003). Those were bracketed by more radiogenic ratios at higher latitudes in the Southern Hemisphere (33°S to 23°S), within the Brazil Current and the Subtropical Gyre (1.163±0.003), and in the Northern Hemisphere (0° to 10°N) (1.165±0.005). The latter were comparable to ratios of surface water in the North Atlantic Equatorial Ocean (1.169±0.006), under a combined contaminant influence of both North American westerlies (1.19–1.20) and European easterlies (1.155–1.165). That predominance of contaminant lead contrasts with the measurable presence of natural lead in surface waters of the Equatorial Ocean, which are attributed to aeolian inputs of Saharan dust. The ratios of lead in surface waters at higher latitudes in the South Atlantic are characteristic of anthropogenic lead aerosols also detected in Antarctic ice, and could substantiate as well the hypothesized aerosol recycling of lead by sea-spray emission in the far Southern Hemisphere. The atmospheric lead isotopic compositions (206Pb/207Pb) in bulk depositions (1.171±0.006), precipitation (1.171±0.006) and aerosols (1.168±0.011) were, generally, more radiogenic than the surface waters (1.162±0.005). Beside a poor representation of a short term atmospheric sampling, this difference could reflect a recent evolution in atmospheric lead emissions, which have not yet been reflected in oceanic surface waters. It may also be due, in part, to advective lead inputs from surface oceanic circulation of the South Equatorial Current.
Journal of Geophysical Research, 2003
Lead concentrations and isotope ratios were measured in North Atlantic surface water samples collected in 1981 (29°-79°N, 6°E-49°W) and in 1989 (23°-39°N, 29°-68°W). In the early 1980s, 206Pb/207Pb ratios in the North African Basin averaged 1.193 +/- 0.005 (1 sigma). Similar radiogenic ratios within the level of analytical precision (average 0.29%) were found in the Labrador and Iceland Basins (1.198 +/- 0.006) and in the Norwegian Sea (1.196 +/- 0.008). These radiogenic mixed layer signatures along with atmospheric global lead emission patterns suggest that most North Atlantic lead in the early 1980s was derived from North American leaded gasoline. Samples in the East Iberian Basin near Portugal and France showed lower 206Pb/207Pb ratios, between 1.167 and 1.182, indicating a significant influence of less radiogenic atmospheric lead transported from Europe and possibly the influence of the Rio Tinto acid mine drainage very close to shore in the Gulf of Cadiz. [Pb] across the entire...