Intercalibration of Cd and Pb concentration measurements in the northwest Pacific Ocean (original) (raw)
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Zurbrick et al 2012 Intercalibration of Cd Pb
2013
Dissolved and total Cd and Pb concentration measurements in seawater were intercalibrated using 33 samples collected on the fourth cruise of the Intergovernmental Oceanographic Commission's (IOC-4) Global Investigation of Pollution in the Marine Environment (GIPME) in the northwest Pacific Ocean, as well as in three seawater reference materials (SAFe S1, SAFe D2, and NASS-5). Laboratories from Florida State University (FSU), University of California at Santa Cruz (UCSC), and University of Southern Mississippi (USM) participated in the Pb intercalibration, and two of them (FSU and UCSC) participated in the Cd intercalibration. While each of the laboratories employed different extraction techniques before analysis by inductively coupled plasma-mass spectrometry (ICP-MS), the measurements of Cd and Pb concentrations for the IOC-4 samples agreed to within 4% and 15%, respectively, and those of the reference materials agreed to within 13% and 8%, respectively. This successful intercalibration demonstrates that there now are multiple techniques available for accurately measuring Cd and Pb concentrations in seawater.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2016
Anthropogenic Pb in the oceans, derived from high-temperature industrial processes, fuel combustion and incineration can have an isotopic signature distinct from naturally occurring Pb, supplied by rock weathering. To identify the different pollution sources accurately and to quantify their relative contributions, Pb isotope ratios are widely used. Due to the high salt content (approximately 3.5% of total dissolved solids) and very low levels of Pb (typically from 1 to 100 ng L −1) in seawater the determination of Pb isotope ratios requires preliminary matrix separation and analyte preconcentration. An analytical protocol for the measurements of Pb isotope ratios in seawater combining seaFAST sample pre-treatment system and Sector Field Inductively Coupled Plasma Mass Spectrometry (SF ICP-MS) was developed. The application of seaFAST system was advantageous, because of its completely closed working cycle and small volumes of chemicals introduced in pre-treatment step, resulting in very low detection limits and procedural blanks. The preconcentration/matrix separation step was also of crucial importance for minimizing the isobaric and matrix interferences, coming from the seawater. In order to differentiate between anthropogenic and natural Pb sources, particular attention was paid to the determination of 204 Pb isotope because of its implication in some geological interpretations. The validation of the analytical procedure was effectuated according to the recommendations of the ISO/IEC 17025 standard. The method was validated by processing the common Pb isotope reference material NIST SRM 981. All major sources of uncertainty were identified and propagated together following the ISO/GUM guidelines. The estimation of the total uncertainty associated to each measurement result was fundamental tool for sorting the main sources of possible biases. The developed analytical procedure was applied to the coastal and open seawater samples, collected in different regions of the world and revealed that the procedure is applicable for the measurement of Pb isotope ratios in seawater with combined uncertainty adequate to discuss the origin of Pb pollution in the ocean.
Precise determination of cadmium isotope fractionation in seawater by double spike MC-ICPMS
Geochimica et Cosmochimica Acta, 2007
A new technique has been developed for the accurate and precise determination of the stable Cd isotope composition of seawater. The method utilizes a 110 Cd-111 Cd double spike, and it involves separation of Cd from seawater by column chromatography and isotopic analyses by multiple collector inductively coupled plasma mass spectrometry. As a by-product, it also generates precise Cd concentration data. Repeated analyses of three pure Cd reference materials and three seawater samples yielded reproducibilities of about ±1.0 to ±1.6 e 114/110 Cd (2 SD), based on measurements that each consumed about $8 ng of natural Cd (e 114/110 Cd is the deviation of the 114 Cd/ 110 Cd isotope ratio of a sample from the standard in parts per 10,000). This demonstrates that the new double spike technique is superior to published methods of Cd isotope analyses, with regard to the acquisition of precise data for samples of limited size. Additional experiments showed that as little as 1-5 ng of seawater Cd could be analyzed with a precision of about ±2 to ±6 e 114/110 Cd (2 SD). The accuracy of the seawater isotope data was ascertained by experiments in which a Cd-free seawater matrix was doped with small quantities of isotopically well-characterized Cd. Repeated mass scans that were carried out on purified Cd fractions of several samples furthermore demonstrated the absence of significant spectral interferences. The isotope data that were acquired for the three seawater samples reveal, for the first time, small but resolvable Cd isotope fractionations in the marine environment. Cadmium-rich intermediate water from the North Pacific was found to have an isotope composition of e 114/110 Cd = 3.2 ± 1.0. In contrast, Cd-depleted seawater from the upper water column of the Atlantic and Arctic Oceans displayed isotope compositions of e 114/110 Cd = 6.4 ± 1.1 and 6.6 ± 1.6, respectively. These observations are in accord with the interpretation that the isotope effects are due to the biological fractionation that occurs during the uptake of dissolved seawater Cd by phytoplankton.
Analytical Chemistry, 1997
A simple low-blank method is described for the analysis of Pb, Cu, and Cd in seawater using Mg(OH) 2 coprecipitation and isotope dilution inductively coupled plasma mass spectrometry (ICPMS). Here, 20-40 µL of 9 M aqueous NH 3 is mixed into a 1.3 mL seawater sample spiked with enriched isotopes of Pb, Cu, and Cd. After centrifugation, the supernatant is discarded and the Mg-(OH) 2 precipitate dissolved in 100 µL of 5% HNO 3 for ICPMS analysis. This method is simple, accurate, and precise, with detection limits of Pb) 1.3 pM, Cu) 39 pM, and Cd) 5.0 pM and blanks of Pb) 0.62 pM, Cu) 27 pM, and Cd) 6.0 pM. The method is demonstrated by oceanographically consistent profiles of these trace metals at an ocean station in the eastern North Atlantic.
Analytica Chimica Acta, 2002
A flow injection inductively coupled plasma magnetic sector mass spectrometry (FI-ICP-MS) method was developed for the analysis of Cd, Cu, Ni, Zn, and Mn in estuarine waters. The method uses just greater than 3 ml sample, and employs an automated on-line preconcentration step using a metal chelating resin (Toyopearl AF-Chelate 650 M). Acidified samples for the analysis of Cd, Cu, Ni, and Zn were buffered on-line to pH of 5.6 ± 0.2 with ammonia acetate just prior to loading onto the chelating resin, while samples for Mn analysis were adjusted to pH of 9.0 ± 0.2 prior to concentration. Limits of detection were: Cd = 1.4 ng l −1 (0.013 nM), Cu = 17 ng l −1 (0.27 nM), Ni = 28 ng l −1 (0.48 nM), Zn = 46 ng l −1 (0.70 nM), and Mn = 86 ng l −1 (1.6 nM). The blank concentrations were less than 1.5% of the SLEW-2 concentrations for each element analyzed, except Ni, which had a significant, but very constant blank from the Ni cones used. The detection limits were less than 5% of the concentrations observed in the San Francisco Bay estuarine samples, with the exception of Zn where the detection limit was 10% of the concentration of lowest San Francisco Bay sample analyzed. Using the FI preconcentration technique, we conducted medium resolution scans of potential isobaric interferences (mass units 55-66) using a magnetic sector ICP-MS to identify a number of interferent complications with evaluating certain isotopes, especially, 59 Co, and 60 Ni. Investigations of potential interferents illustrate the importance of appropriate isotope selection and, in some instances, the need to perform blank corrections with both an instrumental and a matrix blank. The method was verified by the analysis of an estuarine water standard reference materials (SLEW-2), and San Francisco Bay samples with previously reported values. Six estuarine samples run in triplicate generated the following average precision (presented as % R.S.D.); Cd = 4.2%, Cu = 3.2%, Ni = 3.3%, Zn = 4.4%, and Mn = 2.2%. (K.W. Bruland). tool for the determination of trace metals, such as Cd, Cu, Ni, Zn, and Mn in natural waters. ICP-MS is highly sensitive and allows for the simultaneous analysis of numerous elements and their respective isotopes. The elevated levels of Mg 2+ , Ca 2+ , Na + , and K + in seawater ([Mg] = 53 mM, [Ca] = 10 mM, [Na] = 468 mM, [K] = 10 mM) can cause a variety 0003-2670/02/$ -see front matter © 2002 Published by Elsevier Science B.V. PII: S 0 0 0 3 -2 6 7 0 ( 0 1 ) 0 1 5 6 1 -6
Cadmium isotope fractionation in seawater — A signature of biological activity
Earth and Planetary Science Letters, 2007
Investigations of cadmium isotope variations in the oceans may provide new insights into the factors that control the marine distribution and cycling of this element. Here we present the results of Cd isotope and concentration analyses for 22 seawater samples from the Atlantic, Southern, Pacific, and Arctic Oceans. The results reveal, for the first time, large and well resolved Cd isotope fractionations in the marine environment. The majority of the seawater samples display an inverse relationship between dissolved Cd contents and isotope compositions, which range from ε 114/110 Cd≈ +3 ± 0.5 for Cd-rich waters (0.8-1.0 nmol/kg) to ε 114/110 Cd ≈ 38 ± 6 for surface water with a Cd concentration of only 0.003 nmol/kg (all ε 114/110 Cd data are reported relative to the JMC Cd Münster standard). This suggests that the Cd isotope variations reflect kinetic isotope effects that are generated during closed system uptake of dissolved seawater Cd by phytoplankton. A few samples do not follow this trend, as they exhibit extremely low Cd contents (b 0.008 nmol/kg) and nearly un-fractionated Cd isotope compositions. Such complexities, which are not revealed by concentration data alone, require that the Cd distribution at the respective sites was affected by additional processes, such as water mass mixing, atmospheric inputs of Cd and/or adsorption. Uniform isotope compositions of ε 114/110 Cd= +3.3 ± 0.5 (1 S.D.) were determined for seawater from ≥900 m depth, despite of Cd concentrations that display the expected increase along the global deep-water pathway from the Atlantic (∼0.3 nmol/kg) to the Pacific Ocean (∼0.9 nmol/kg). This indicates that the biomass, which is remineralized in the deeper ocean, is also characterized by a very constant Cd isotope composition. This observation is in accord with the interpretation that the Cd distribution in surface waters is primarily governed by Rayleigh fractionation during near-quantitative uptake of dissolved seawater Cd.
Cadmium in northeast Pacific waters
Limnology and Oceanography, 1978
Northeast Pacific water was collected by five different methods and the Cd in it was preconcentrated by both chelex-ion exchange and chelation-organic extraction techniques. All sampling and preconcentnation methods yielded essentially the same data. Cadmium was very significantly correlated with phosphate and nitrate at all depths and it appears that the resulting equations, ng Cd* liter-' = -3.6 + 34.9 (Mmol PO,. liter-') and ng Cd. liter-l = 5.1 + 2.45 (pmol NOR-liter-'),
Cadmium isotopic composition in the ocean
Geochimica Et Cosmochimica Acta, 2006
The oceanic cycle of cadmium is still poorly understood, despite its importance for phytoplankton growth and paleoceanographic applications. As for other elements that are biologically recycled, variations in isotopic composition may bring unique insights. This article presents (i) a protocol for the measurement of cadmium isotopic composition (Cd IC) in seawater and in phytoplankton cells; (ii) the first Cd IC data in seawater, from two full depth stations, in the northwest Pacific and the northwest Mediterranean Sea; (iii) the first Cd IC data in phytoplankton cells, cultured in vitro. The Cd IC variation range in seawater found at these stations is not greater than 1.5 e Cd/amu units, only slightly larger than the mean uncertainty of measurement (0.8 e Cd/amu ). Nevertheless, systematic variations of the Cd IC and concentration in the upper 300 m of the northwest Pacific suggest the occurrence of Cd isotopic fractionation by phytoplankton uptake, with a fractionation factor of 1.6 ± 1.4 e Cd/amu units. This result is supported by the culture experiment data suggesting that freshwater phytoplankton (Chlamydomonas reinhardtii and Chlorella sp.) preferentially take up light Cd isotopes, with a fractionation factor of 3.4 ± 1.4 e Cd/amu units. Systematic variations of the Cd IC and hydrographic data between 300 and 700 m in the northwest Pacific have been tentatively attributed to the mixing of the mesothermal (temperature maximum) water (e Cd/amu = À0.9 ± 0.8) with the North Pacific Intermediate Water (e Cd/amu = 0.5 ± 0.8). In contrast, no significant Cd IC variation is found in the northwest Mediterranean Sea. This observation was attributed to the small surface Cd depletion by phytoplankton uptake and the similar Cd IC of the different water masses found at this site. Overall, these data suggest that (i) phytoplankton uptake fractionates Cd isotopic composition to a measurable degree (fractionation factors of 1.6 and 3.4 e Cd/amu units, for the in situ and culture experiment data, respectively), (ii) an open ocean profile of Cd IC shows upper water column variations consistent with preferential uptake and regeneration of light Cd isotopes, and (iii) different water masses may have different Cd IC. This isotopic system could therefore provide information on phytoplankton Cd uptake and on water mass trajectories and mixing in some areas of the ocean. However, the very small Cd IC variations found in this study indicate that applications of Cd isotopic composition to reveal aspects of the present or past Cd oceanic cycle will be very challenging and may require further analytical improvements. Better precision could possibly be obtained with larger seawater samples, a better chemical separation of tin and a more accurate mass bias correction through the use of the double spiking technique.
Chemosphere, 2017
During the austral summer 2011-2012, the metal quotas of Cd, Pb and Cu in the phytoplankton of Terra Nova Bay (TNB, Antarctica) were measured for the first time. Evolution of all the three metal distributions between dissolved and particulate fractions during the season was also evaluated. Metal concentrations were mainly affected by the dynamic of the pack ice melting and phytoplankton activity. In mid-December when TNB area was covered by a thick pack ice layer and phytoplankton activity was very low, all the three metals were present mainly in their dissolved species. When the pack ice started to melt and the water column characteristics became ideal (i.e. moderate stratification, ice free area), the phytoplankton bloom occurred. Cd showed a nutrient-type behaviour with dissolved and particulate fractions mainly influenced by phytoplankton activity. Cd quota showed a mean value of 0.12 ± 0.07nmol L-1 (30-100% of the total particulate). Also Cu showed a nutrient-type behaviour, with its quota in phytoplankton varying between 0.08 and 2.1 nmol L-1 (20-100% of the total particulate). Pb features the typical distribution of a scavenged element with very low algal content (0.03 ± 0.02 nmol L-1 , representing 20-50% of the total particulate). The vertical distribution of this element was influenced by several factors (e.g. pack ice melting, atmospheric inputs), the phytoplankton activity affecting Pb behaviour only partially. Metal:C ratios provide valuable information on the biological requirements for Cd, Pb and Cu, leading us to better understand their biogeochemical cycles.