Geochemical perspectives from the past: understanding the natural enrichment of Cd in pre-industrial and pre-anthropogenic aerosols using polar ice and peat cores from remote locations (original) (raw)
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Natural and Anthropogenic Cd Isotope Variations
2012
Cadmium is a transition metal with eight naturally occurring isotopes that have atomic mass numbers of between 106 and 116. The large Cd isotope anomalies of meteorites have been subject to investigation since the 1970s, but improvements in instrumentation and techniques have more recently enabled routine studies of the smaller stable Cd isotope fractionations that characterize various natural and anthropogenic terrestrial materials. Whilst the current database is still comparatively small, pilot studies have identified two predominant mechanisms that routinely generate Cd isotope effects -partial evaporation/condensation and biological utilization. Processes that involve evaporation and condensation appear to be largely responsible for the Cd isotope fractionations of up to 1‰ (for 114 Cd/ 110 Cd) that have been determined for industrial Cd emissions, for example from ore refineries. Cadmium isotope measurements hence hold significant promise for tracing anthropogenic sources of this highly toxic metal in the environment. The even larger Cd isotope fractionations that have been identified in the oceans (up to 4‰ for 114 Cd/ 110 Cd) are due to biological uptake and utilization of dissolved seawater Cd. This finding confirms previous work, which identified Cd as an essential marine micronutrient that exhibits a phosphate-like distribution in the oceans. The marine Cd isotope fractionations are of particular interest, as they can be used to study micronutrient cycling and its impact on ocean productivity. In addition, they may also inform on past changes in marine nutrient utilization and how these are linked to global climate, if suitable archives of seawater Cd isotope compositions can be identified.
Geochimica et Cosmochimica Acta, 2003
A new technique for the precise and accurate determination of Cd stable isotope compositions has been developed and applied to geological materials and meteorites. The Cd isotope analyses are performed by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) using external normalization to Ag for mass bias correction. The accuracy of the new procedure was ascertained by the comparison of data for meteorites with published results acquired by thermal ionization mass spectrometry and double spiking. Some results were also confirmed by measurements using external normalization to Sb on a different MC-ICPMS instrument. A long-term reproducibility of Ϯ 1.1 Cd/amu (2 sd) was obtained for separate dissolutions and multiple analyses of several rock and meteorite samples (Cd/amu represents the deviation of a Cd isotope ratio of a sample relative to the JMC Cd standard in parts per 10 4 , normalized to a mass difference of 1 amu). As little as 5-20 ng of Cd are sufficient for the acquisition of precise and accurate data.
Environmental Science & Technology, 2005
This study aims to determine the extent to which the accumulation rates of Cu, Ni, Co, Zn, and Cd in peat cores agree with established histories of atmospheric emission from local point sources. Metals accumulating in three Finnish peat cores with known metal deposition histories have been measured using inductively coupled plasma-sector field mass spectrometry. Samples were age-dated using both 210 Pb and 14 C (bomb pulse curve). At the Outokumpu (OUT) site as well as the low-background site Hietajärvi (HIJ), 210 Pb age dates are in excellent agreement with the 14 C bomb pulse curve method results, and the precision is between 1 and 10 years for most of the samples; at the Harjavalta (HAR) site, precision is >6 years. Mean regional "background" concentrations have been calculated from deeper peat layers of the HIJ site (µg g -1 ): Cu, 1.3 ( 0.2 (n ) 62); Co, 0.25 ( 0.04 (n ) 71); Cd, 0.08 ( 0.01 (n ) 23); and Zn, 4 ( 2 (n ) 40). For layers accumulated within the past 100 years, accumulation rates (ARs) have been calculated. At sites with <0.06 g m -2 cumulative Ni inventory (HIJ and OUT), ARs of Cu and Co trace the known metal deposition histories very well. At HAR, where metal inventories are much greater, Cu and Co are mobile. ARs of Zn were between 3 and 30 mg m -2 year -1 and those of Cd between 24 and 140 µg m -2 year -1 at all sites and are independent of the chronology of their inputs from the atmosphere.
2010
Environmental monitoring and remediation require techniques to identify the source and fate of metals emissions. In this study, Cd and Zn isotopes were evaluated as tools for the identification of metal sources through (1) the assessment of metallurgical processing as a source of Cd and Zn isotopic fractionation and (2) the measurement of isotopic compositions in bivalves from sites receiving variable metal contributions from natural and anthropogenic sources. This study was facilitated by the successful development of a technique to measure Cd and Zn isotopes (MC-ICP-MS) in environmental and anthropogenic samples. Cadmium, Zn and Pb isotopic ratios were measured for samples from an integrated Zn–Pb smelting/refining complex in B.C. (British Columbia, Canada). Significant fractionation of Cd and Zn isotopes during processing is demonstrated by the total isotopic variation in δCd (1.04‰) and δZn (0.42‰) among smelter samples. Characterization of Cd and Zn isotopic compositions in emi...
Fluxes, trends and source characterisation of atmospheric trace elements
Aerosols are well known to have effects on climate and human health. The chemical composition of aerosols in particular has a profound effect on the latter. Many trace elements (e.g. cadmium, lead and arsenic) found in the particulates as well as mercury (existing mostly in the gaseous form) are considered toxic for humans while deposition of these elements poses risks to the ecosystems. Due to emission abatement strategies, emissions of trace elements have significantly reduced in the recent decades. The overall objective of this thesis was to gain knowledge on the different sources as well as the temporal and spatial changes of atmospheric trace elements in Finland. The thesis was focused on the priority trace element pollutants mercury, arsenic, cadmium, nickel and lead. Also, other elements of interest were studied (aluminium, chromium, cobalt, copper, iron, manganese, vanadium, and zinc). Gaseous, particulate and deposition forms of the elements were investigated. The work was concentrated in background areas far away from possible anthropogenic sources; however, urban and industrial sites were also surveyed. The measurement techniques were partially developed or further validated in this thesis, and partially we utilised measurements conducted as a part of international measurement programmes. Sources of trace elements were studied with source apportionment method using positive matrix factorisation (PMF) and enrichment factors. Enrichment factors were used to characterize the source of a pollutant between natural and anthropogenic, and this grouped the elements from mainly crustal (Al, Fe) to highly anthropogenic origin (As, Cd, Pb, Zn) and others in between. PMF produced a more precise analysis of sources for Pallas, in which trace elements were associated with soil, sea emissions, and various long-range transported sources e.g. copper and nickel smelters in Kola Peninsula, Russia. In addition, magnitude of mercury soil and wetland emissions was investigated at one background site with the chamber technique. The air-terrestrial surface exchange measurements of elemental mercury showed that the soil emissions were found similar to depositional fluxes at the site (but opposite) and larger than the ones observed at wetland. For most trace elements, a clear south-to-north decreasing gradient in both atmospheric concentrations and deposition was observed due to minor local sources and longer distance to the large European source areas in the north than in the south. Additionally, the differences in the length of the snow-cover period have an effect on resuspension of some of the elements. For several elements both in particulate matter (PM) and deposition, statistically significant decreasing trends up to 80 % were detected since the 1990s. For gaseous mercury, no statistically significant trends were found. No statistically significant increasing trends were observed for PM, however, at two sites increases in deposition of single elements were detected.
Tracing Source Pollution in Soils Using Cadmium and Lead Isotopes
Environmental Science & Technology, 2006
Tracing the source of heavy metals in the environment is of key importance for our understanding of their pollution and natural cycles in the surface Earth reservoirs. Up to now, most exclusively Pb isotopes were used to effectively trace metal pollution sources in the environment. Here we report systematic variations of Cd isotope ratios measured in polluted topsoils surrounding a Pb-Zn refinery plant in northern France. Fractionated Cd was measured in soil samples surrounding the refinery, and this fractionation can be attributed to the refining processes. Despite the Cd isotopic ratios being precisely measured, the obtained uncertainties are still large compared to the total isotopic variation. Nevertheless, for the first time, Cd isotopically fractionated by industrial processes may be traced in the environment. On the same samples, Pb isotope systematics suggested that materials actually used by the refinery were not the major source of Pb in soils, probably because refined ore origins changed over the 100 years of operation. On the other hand, Cd isotopes and concentrations measured in topsoils allowed identification of three main origins (industrial dust and slag and agriculture), assuming that all Cd ores are not fractionated, as suggested by terrestrial rocks so far analyzed, and calculation of their relative contributions for each sampling point. Understanding that this refinery context was an ideal situation for such a study, our results lead to the possibility of tracing sources of anthropogenic Cd and better constrain mixing processes, fluxes, transport, and phasing out of industrial input in nature.