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Peat cores taken from ombrotrophic bogs are widely used to reconstruct historical records of atmospheric lead and mercury déposition [1, 2]. In this study, the retention of copper, nickel, cadmium and zinc in peat bogs are studied by comparing high resolution, age dated concentration profiles with emissions from the main local source, the Outokumpu copper-nickel mine. An ombrotrophic peat core was taken from the vicinity of Outokumpu, E Finland. Copper and zinc concentrations of dry peat were measured by XRF, cadmium and nickel by GF-AAS, and sample ages by 210Pb. Only copper and nickel show enhanced concentrations in layers covering the mining period, indicating a retention of these elements. However, the more detailed comparison of ore production rates and concentrations in age-dated samples show clearly that only copper is likely to be permanently fixed, while nickel doesn't reflect the mining activity. Even though copper is retained in the upper part of the profile, a possible redeposition of this element by secondary processes (e.g., water table fluctuations) can not be excluded. This question will be resolved by further investigations, e.g. by pore water profiles.

A peat monolith representing up to 4,000 years of peat accumulation near Manchester, England, was collected. Major and trace elements were analysed with XRF and for Cd and Pb in the deeper samples with GF-AAS following acid digestion. Pb isotopic composition was measured with TIMS and ICP-MS. The results show a pollution since the Roman Period due to local lead sources and an increase in lead pollution in the last century due to leaded gasoline as fingerprinted by Pb isotopic signatures.

To quantify the effects of human activities on atmospheric deposition of mercury in eastem Canada, an improved understanding of the natural variations of the concentrations, fluxes and sources of Hg over a long period of time is required. Peat cores from 3 sites in southern Ontario were used to reconstruct changes in atmospheric mercury accumulation rates for the past 10,000 years. The net mercury accumulation rates and excess mercury (mainly anthropogenic) were calculated using the long-terrn average Hg/Br and Hg/Se. The average background mercury accumulation rate during the pre-anthropogenic period was $1.4 \pm 1.0~\mu$g m-2yr-1. An excess of Hg was observed only once during that period, probably reflecting a change in climat. Mercury contamination from anthropogenic sources began about AD 1475 at the Luther Bog, corresponding to extensive biomass burning for agricultural activities by Native North Americans. During the late 17thand 18thcenturies, deposition of anthropogenic Hg was at least equal to that of Hg from natural sources. Hg pollution increased again at the beginning of the 19thcentury. The maximum increase (up to 30 times) compared to “background” occurred during the 1950s, when the anthropogenic component represented up to 85% ofthe total atmospheric mercury deposition.

There is a growing interest in the atmospheric transport, deposition, and accumulation of anthropogenic Hg in the Arctic. To quantify the impact of industrial Hg emissions, the natural rate of atmospheric Hg accumulalion must be known. Mercury concentration measilrements and age dating oi peatfrom the Canadian Arctic show that natural “background” Hg flux rather constant (ca. 1 microgram per sq. m per yr.) throughout the past 6,000 years. Mercury concentrations in surface peat layers are much higher, but chronology ofthese changes cannot be interpreted until more age dates are available. The elevated Hg concentrations in surface layers, however, are out of proportion with Br and Se, suggesting that there has been a significant human impact. Peat cores from southern Canada provide a record of atmospheric Hg accumulation extending back nine thozisand years, with similar backgroundfluxes. Thus, pre-anthropogenic Hg fluxes in the High Arctic were not significantly differentfrom atmospheric Hg fluxes in the temperate Zone.

An electromechanical drill with titanium barrels was used to recover a 63.7 m long firn core from Devon Island Ice Cap, Nunavut, Canada, representing 155 years of precipitation. The core was processed and analysed at the Geological Survey of Canada by following strict clean procedures for measurements of Pb and Cd at concentrations at or below the pg g−1level. This paper describes the effectiveness of the titanium drill with respect to contamination during ice core retrieval and evaluates sample-processing procedures in laboratories. The results demonstrate that: (1) ice cores retrieved with this titanium drill are of excellent quality with metal contamination one to four orders of magnitude less than those retrieved with conventional drills; (2) the core cleaning and sampling protocols used were effective, contamination-free, and adequate for analysis of the metals (Pb and Cd) at low pg g−1levels; and (3) results from 489 firn core samples analysed in this study are comparable with published data from other sites in the Arctic, Greenland and the Antarctic.

Given the increasing interest in using peat bogs as archives of atmospheric metal deposition, the lack of validated sample preparation methods and suitable certified reference materials has hindered not only the quality assurance of the generated analytical data but also the interpretation and comparison of peat core metal profiles from different laboratories in the international community. Reference materials play an important role in the evaluation of the accuracy of analytical results and are essential parts of good laboratory practice. An ombrotrophic peat bog reference material has been developed by 14 laboratories from nine countries in an inter-laboratory comparison between February and October 2002. The material has been characterised for both acid-extractable and total concentrations of a range of elements, including Al, As, Ca, Cd, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, P, Pb, Ti, V and Zn. The steps involved in the production of the reference material i.e.collection and preparation, homogeneity and stability studies, and certification are described in detail.

A 650 cm core from a Swiss bog represents 12,370 14C years of peat accumulation and provides the first complete record of atmospheric Pb deposition for the entire Holocene. Excess, non-atmospheric Sr in the peat was calculated by normalizing Sr/Sc to crustal abundance; this was used to differentiate between the ombrogenicsection of the bog in which inorganic solids are supplied exclusively by atmospheric deposition and the minerogeniczone where mineral-water interactions contribute metals to the peat. While sediment dissolution contributes significantly to the Sr inventory of the minerogenic section of the peat profile, there is no measurable effect of this process on the Pb burden. Isotopic analyses (204Pb, 206Pb, 207Pb, 208Pb) show that effectively all of the Pb in the peat profile was supplied exclusively from the atmosphere.

Equilibrium diffusion chambers (“peepers”) have been constructed to collect anoxic pore waters in bogs without degassing and/or oxidizing the samples. These samplers have been constructed of Plexiglass, either as a long board with a series of sampling chambers for close interval analyses near the surface of a bog, or as single chambers inserted at greater depths (1 to 6 m). Prior to installation, the chambers have been filled with deaerated, deionized water, and have been covered by a 0.2 µm membrane filter; this membrane allows the dissolved constituents in the waters to equilibrate with the deionized water in the chamber by diffusion. The samplers have been allowed to equilibrate in the bog for 4 to 6 weeks. Thereafter, they have been withdrawn into N 2-filled glove bags. Individual chambers have been sampled in the field by inserting a syringe through the glove bag; these syringes have been used immediately upon the arrival in the lab to analyze volatile and redox-sensitive species by ion chromatography. The effectiveness of this sampling approach has been demonstrated by measuring the concentrations of the dominant volatile acids in these waters (H 2CO 3) and two redox sensitive species (Fe 2+ and HS –). The procedure described here should be applicable also to trace metal speciation studies, provided that appropriate checks are made for all possible sources of contamination.

Polished (001) cleavage faces of Nain Labradorite ($$An \approx 56$$) were leached at 20°C ($$\pm 2^{\circ}$$) for 72 days in distilled water ($$pH \approx 5.6$$), in HCl solution ($$pH \approx 4.05$$) and in four other HCl solutions containing 1 mg/l or less of Na, K, Ca, Al(aq), and $$SiO_{2}(aq)$$($$pH of all four solutions \approx 4.05$$). Analysis of the cleavage faces by Secondary Ion Mass Spectrometry (SIMS) revealed no residual surface layer on faces leached by distilled water. By contrast, thick Si-rich residual layers (1500 Å) formed on surfaces leached by pure HCl solutions. Much thinner residual layers (700 Å) were observed on labradorite leached by HCl solutions containing 1 mg/l of Na, Ca, and K, whereas leached layers <75 Å thick formed on faces leached by solutions containing 1 mg/l each of Na, K, Ca, Al(aq) and Si(aq); consequently incongruent dissolution of feldspars occurs in HCl solution, but congruent dissolution of feldspars occurs in mixed electrolyte solutions in which dissolved cations are more abundant than $$H_{3}O^{+}$$(hydronium or proton). Of the cations studied, Al(aq) most affects formation of the leached layers, $$SiO_{2}(aq)$$, however, does not noticeably affect thickness of the residual layer. Affinity of cations for surface functional groups affects the rate of formation of the leached layer (diffusion), and the rate of surface dissolution from the Si-rich surface layer, by controlling the concentration of $$H_{3}O^{+}$$surface complexes on the surface of the leached layer. Diffusion through the leached layer apparently proceeds via lattice diffusion and line defects. A "competitive adsorption model" is proposed to explain the SIMS results and experimental leaching results of others. An important prediction of the model is that Si-rich residual layers generally do not form on feldspars of most soil and weathering profiles. If the residues form, they generally will be thin, with the thickness controlled by the composition of the soil solution.

Peat bogs serve as faithful archives of atmospheric Pb deposition, and there is growing evidence that they preserve reliable records of atmospheric Hg and Cu deposition as well. Far less is known about As and Se in peat, despite their environmental relevance, because there have been so few studies; the lack of study probably is due partly to the difficulties associated with the measurement of these elements at low concentrations in complex matrices. In peat which is contaminated with anthropogenic As (e.g. bogs near smelters), and in minerotrophic peat which may be naturally enriched with this element, As can be measured in solid samples containing 1 to 100 or more ppm using XRF or INAA. Similarly, Se can be measured in blanket peats from maritime locations using either of these methods, because marine emissions of DMSe give rise to elevated Se concentrations (1 to 10 ppm) in these peats. However, in pre-anthropogenic peats from continental bogs, the concentrations of As and Se are far lower (<0.1 ppm), and only recently bas As been reliably measured in peat samples at these levels (Krachler et al., 2002). Clearly, accurate and precise measurements are needed both to describe the geochemical cycles of these elements, and for the reconstruction of atmospheric metal deposition rates. Thus, there is a real need to develop robust and reliable analytical methods with low detection limits for the determination of As and Se in ombrotrophic peat.