Niels C. Munksgaard

Determination of Trace Metals in Sea-water by Inductively Coupled Plasma Mass Spectrometry After Off-line Dithiocarbamate Solvent Extraction

An off-line solvent extraction procedure with inductively coupled plasma mass spectrometric (ICP-MS) determination was developed for the determination of heavy metals in sea-water at ultra-trace levels. The procedure was adapted from a dithiocarbamate–diisobutyl ketone solvent extraction system with Hg back-extraction, which was previously validated using electrothermal atomic absorption spectrometry. The simultaneous ICP-MS determination significantly reduced the analysis times and improved the detection limits (Cd 0.2, Co 0.3, Cu 3, Fe 21, Ni 2, Pb 0.5 and Zn 2 ppt). The rapid single extraction procedure was quantitative and external standards were used for ICP-MS calibration. The method gave good reproducibility with precisions at the 100 ppt level better than 5% (n=4), except for Fe (7%). The method was validated by accurate analysis of CASS-3 Nearshore Sea-water and NASS-4 Open Ocean Sea-water Standard Reference Materials.

Stable isotopes in leaf water of terrestrial plants

Leaf water contains naturally occurring stable isotopes of oxygen and hydrogen in abundances that vary spatially and temporally. When sufficiently understood, these can be harnessed for a wide range of applications. Here, we review the current state of knowledge of stable isotope enrichment of leaf water, and its relevance for isotopic signals incorporated into plant organic matter and atmospheric gases. Models describing evaporative enrichment of leaf water have become increasingly complex over time, reflecting enhanced spatial and temporal resolution. We recommend that practitioners choose a model with a level of complexity suited to their application, and provide guidance. At the same time, there exists some lingering uncertainty about the biophysical processes relevant to patterns of isotopic enrichment in leaf water. An important goal for future research is to link observed variations in isotopic composition to specific anatomical and physiological features of leaves that reflect differences in hydraulic design. New measurement techniques are developing rapidly, enabling determinations of both transpired and leaf water δ(18) O and δ(2) H to be made more easily and at higher temporal resolution than previously possible. We expect these technological advances to spur new developments in our understanding of patterns of stable isotope fractionation in leaf water.

Rare earth elements as provenance indicators in North Australian estuarine and coastal marine sediments

Rare earth elements (REE) in three grain size fractions of clay-dominated estuarine and coastal sediments from the North Australian coastline have been investigated for use as potential provenance indicators. Comparisons of data based on instrumental neutron activation analysis and inductively coupled plasma mass spectrometry revealed that HF digestions of zircon-bearing samples resulted in unsatisfactory recovery of REE. Instead, a relatively simple, fast and safe partial digestion using HClO4 + HNO3 was used to extract REE mainly from clay minerals while excluding extraction of REE from zircons. A comparison with published data for primary rock units within river catchments showed that the main REE systematics has been preserved in downstream clay-rich sediments. Analysis of variance of La/Gd(PAAS), La/Yb(PAAS) and Eu/Eu*(PAAS) ratios in five areas showed that the <63 μm fraction possessed the greatest discriminating power. All five areas could be distinguished from each other at highly significant levels based on one or more of these ratios.

Lead isotope ratios determined by ICP-MS: Investigation of anthropogenic lead in seawater and sediment from the Gulf of Carpentaria, Australia☆

Abstract Lead isotope ratios and concentrations have been measured in seawater and marine sediment by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). 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 208Pb/206Pb and 207Pb/206Pb. 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 208Pb/206Pb ratios in the range 2.21-2.25, whereas environmental background 208Pb/206Pb ratios were: filtered (

Lead isotope ratios determined by ICP-MS : Monitoring of mining-derived metal particulates in atmospheric fallout, Northern Territory, Australia

Rates of Zn and Pb fallout from atmospheric particulates > 10-20 μm in diameter have been measured by passive sampling during development of the McArthur River Zn/Pb mine from 1993 to 1997. Although short-term variability at a given location is high due to a combination of natural factors and limitations imposed by the sampling technique, long-term fallout rates of Pb increased significantly in 1995 following commencement of local mining operations. Recently fallout rates have decreased and are at the lower end of the range found in other Australian mining and inner-city locations. The measurement of Pb isotope ratios by ICP-MS in samples of fallout and soil has provided unequivocal evidence that ore-derived Pb has become the dominant Pb source in fallout up to 8.6 km from the mine. The isotope data has provided sensitive and reliable discrimination between ore-derived Pb and local soil-derived Pb. In areas with several potential sources of fallout, Pb isotope ratios determined by ICP-MS may provide a source-specific and cost-effective monitoring tool.

Metals, arsenic and lead isotopes in near-pristine estuarine and marine coastal sediments from northern Australia

Arsenic and selected metal concentrations, as well as Pb isotope ratios, are reported for sediments from thirteen estuaries and coastal areas along tropical northern Australia. A close approximation of total As, Fe, Mn, Co, Ni, Cu, Zn, Cd and Pb concentrations were derived by a perchloric + nitric acid digestion procedure and the potentially bioavailable fractions were extracted by 1M hydrochloric acid. Total concentrations were at near-pristine levels and although some significant variations were observed amongst the areas studied, concentration ranges are similar to those published for other areas in the region with little anthropogenic input. The potentially bioavailable fraction of each metal (average % ± 1 s.d.) for all areas are: Mn(65 ± 11) > Pb(50 ± 9) > Cd(43 ± 23) > Co(33 ± 5) > Cu (27 ± 5) > As (21 ± 8) > Ni (15 ± 5) ≈ Fe (13 ± 6) ≈ Zn (13 ± 5). The potentially bioavailable fractions for Mn, Co and Ni are similar to published data for globally averaged river particulates. The isotope ratios of naturally derived Pb are catchment specific and of potential value in tracing the provenance of marine coastal and offshore terrigenous sediments. Concordant isotopic ratios for potentially bioavailable Pb and total Pb confirm that there is little anthropogenic Pb in the sediments.

Stable isotope anatomy of tropical cyclone Ita, North-Eastern Australia, April 2014

The isotope signatures registered in speleothems during tropical cyclones (TC) provides information about the frequency and intensity of past TCs but the precise relationship between isotopic composition and the meteorology of TCs remain uncertain. Here we present continuous δ18O and δ2H data in rainfall and water vapour, as well as in discrete rainfall samples, during the passage of TC Ita and relate the evolution in isotopic compositions to local and synoptic scale meteorological observations. High-resolution data revealed a close relationship between isotopic compositions and cyclonic features such as spiral rainbands, periods of stratiform rainfall and the arrival of subtropical and tropical air masses with changing oceanic and continental moisture sources. The isotopic compositions in discrete rainfall samples were remarkably constant along the ~450 km overland path of the cyclone when taking into account the direction and distance to the eye of the cyclone at each sampling time. Near simultaneous variations in δ18O and δ2H values in rainfall and vapour and a near-equilibrium rainfall-vapour isotope fractionation indicates strong isotopic exchange between rainfall and surface inflow of vapour during the approach of the cyclone. In contrast, after the passage of spiral rainbands close to the eye of the cyclone, different moisture sources for rainfall and vapour are reflected in diverging d-excess values. High-resolution isotope studies of modern TCs refine the interpretation of stable isotope signatures found in speleothems and other paleo archives and should aim to further investigate the influence of cyclone intensity and longevity on the isotopic composition of associated rainfall.

Microwave extraction-isotope ratio infrared spectroscopy (ME-IRIS): a novel technique for rapid extraction and in-line analysis of δ18O and δ2H values of water in plants, soils and insects.

RATIONALE Traditionally, stable isotope analysis of plant and soil water has been a technically challenging, labour-intensive and time-consuming process. Here we describe a rapid single-step technique which combines Microwave Extraction with Isotope Ratio Infrared Spectroscopy (ME-IRIS). METHODS Plant, soil and insect water is extracted into a dry air stream by microwave irradiation within a sealed vessel. The water vapor thus produced is carried to a cooled condensation chamber, which controls the water vapor concentration and flow rate to the spectrometer. Integration of the isotope signals over the whole analytical cycle provides quantitative δ(18)O and δ(2) H values for the initial liquid water contained in the sample. Calibration is carried out by the analysis of water standards using the same apparatus. Analysis of leaf and soil water by cryogenic vacuum distillation and IRMS was used to validate the ME-IRIS data. RESULTS Comparison with data obtained by cryogenic distillation and IRMS shows that the new technique provides accurate water isotope data for leaves from a range of field-grown tropical plant species. However, two exotic nursery plants were found to suffer from spectral interferences from co-extracted organic compounds. The precision for extracted leaf, stem, soil and insect water was typically better than ±0.3 ‰ for δ(18)O and ±2 ‰ for δ(2) H values, and better than ±0.1 ‰ for δ(18)O and ±1 ‰ for δ(2) H values when analyzing water standards. The effects of sample size, microwave power and duration and sample-to-sample memory on isotope values were assessed. CONCLUSIONS ME-IRIS provides rapid and low-cost extraction and analysis of δ(18)O and δ(2) H values in plant, soil and insect water (≈10-15 min for samples yielding ≈ 0.3 mL of water). The technique can accommodate whole leaves of many plant species.

Laser Ablation ICP-MS Analysis of Faviidae Corals for Environmental Monitoring of a Tropical Estuary

An LA-ICP-MS linescan procedure has been developed for the determination of sub-millimetre scale elemental compositions of Al, Ba, Cu, La, Mg, Mn, Pb, Rb, Sr, U, and Zn in corallite walls of Faviidae corals, with the aim of establishing coral-based pollution monitoring in a tropical estuary. By selectively analyzing corallite walls, analytical signals from voids, organic, and detrital phases were minimized. Although the relative ablation yields of coral aragonite and NIST glass calibration standards differed and was dependent on pulse energy, accurate internal-standard normalized results could be verified for Ba, Cu, La, Mn, Pb, Sr, U, and Zn through the use of a secondary carbonate standard (MACS-1) and comparison with solution ICP-MS analysis. Signal smoothing and pre-acquisition surface cleaning procedures were applied. Corallite wall compositions varied by factors of up to five over distances of a few hundred micrometres. Significantly, the compositional variations along and perpendicular to the coral growth axis were of similar magnitude on a sub-millimetre scale. Consequently, compositional variations along the growth axis could not be interpreted chronologically on a sub-annual time scale. However, compositional records based on multi-annual integrated line scans should still reflect long-term environmental influences.

ISO‐CADICA: Isotopic – continuous, automated dissolved inorganic carbon analyser

RATIONALE Quantifying the processes that control dissolved inorganic carbon (DIC) dynamics in aquatic systems is essential for progress in ecosystem carbon budgeting. The development of a methodology that allows high-resolution temporal data collection over prolonged periods is essential and is described in this study. METHODS A novel sampling instrument that sequentially acidifies aliquots of water and utilises gas-permeable ePTFE tubing to measure the dissolved inorganic carbon (DIC) concentration and δ(13)C(DIC) values at sub-hourly intervals by Cavity Ring-down spectrometry (CRDS) is described. RESULTS The minimum sensitivity of the isotopic, continuous, automated dissolved inorganic carbon analyser (ISO-CADICA) system is 0.01 mM with an accuracy of 0.008 mM. The analytical uncertainty in δ(13)C(DIC) values is proportional to the concentration of DIC in the sample. Where the DIC concentration is greater than 0.3 mM the analytical uncertainty is ±0.1‰ and below 0.2 mM stability is < ± 0.3‰. The isotopic effects of air temperature, water temperature and CO(2) concentrations were found to either be negligible or correctable. Field trials measuring diel variation in δ(13)C(DIC) values of coral reef associated sea water revealed significant, short-term temporal changes and illustrated the necessity of this technique. CONCLUSIONS Currently, collecting and analysing large numbers of samples for δ(13)C(DIC) measurements is not trivial, but essential for accurate carbon models, particularly on small scales. The ISO-CADICA enables on-site, high-resolution determination of DIC concentration and δ(13)C(DIC) values with no need for sample storage and laboratory analysis. The initial tests indicate that this system can offer accuracy approaching that of traditional IRMS analysis.