Reijo Salminen

The problem of defining geochemical baselines. A case study of selected elements and geological materials in Finland

Abstract Although the term ‘geochemical baseline’ appears in the international geochemical mapping programmes IGCP 259 and 360, it has never been well defined. Several considerations relevant to such a definition are discussed. A geochemical baseline for an element refers to its natural variations in concentration in the surficial environment. Geochemical baselines were studied in Finland by comparing results from regional geochemical mapping programmes based on samples of till, clay and organic stream sediment. The geochemical background changes regionally with the basic geology and locally with the type and genesis of the overburden. Baseline concentrations depend on sample material collected, grain size and extraction method. In Finland, concentrations of potentially harmful elements tend to be higher in fine-grained marine and lacustrine sediments than in glacial till. Concentrations are also systematically higher in the

Considerations regarding the definition of a geochemical baseline of elements in the surficial materials in areas differing in basic geology

Abstract The problem of a geochemical baseline in areas differing in basic geology was studied by comparing the results of regional geochemical mapping programmes undertaken in Finland and Lithuania using different sample media and a variety of analytical methods. The authors discuss issues relevant to the definition of a geochemical baseline. Most of the differences in geochemical baselines between Lithuania and Finland are due to the dissimilarities in basic geology, which in Lithuania is controlled by Palaeozoic and Mesozoic sedimentary rocks, but in Finland by Archaean and Proterozoic metamorphic and intrusive rocks. Other important factors are the geological processes that after the last glaciation created the present surficial materials. In Finland, for instance, the abundances of potentially harmful elements derived from crystalline bedrock tend to be higher than in Lithuania. However, in both countries element concentrations are higher in finely-grained marine and lacustrine sediments than in glacial till, and they are also higher in the finer grain size fractions than in the coarser fractions of till samples. Only a small proportion of the total heavy metal concentrations is bioavailable. Thus the baseline concentrations depend not only on the basic geology, but also on sample material collected, its grain size and the extraction method.

ARSENIC AND OTHER TOXIC ELEMENTAL CONTAMINATION OF GROUNDWATER, SURFACE WATER AND SOIL IN BANGLADESH AND ITS POSSIBLE EFFECTS ON HUMAN HEALTH

The problems of contamination caused by arsenic (As) and other toxic metals in groundwater, surface water and soils in the Bengal basin of Bangladesh have been studied. Altogether 10 groundwater, seven surface water and 31 soil samples were collected from arsenic-affected areas and analysed chemically. The geologic and anthropogenic sources of As and other toxic metals are discussed in this paper. The chemical results show that the mean As concentrations in groundwater in the Char Ruppur (0.253 mg As L−1), Rajarampur (1.955 mg As L−1) and Shamta areas (0.996 mg As L−1) greatly exceed the WHO recommended value, which is 0.01 mg As L−1. The concentrations of As in groundwater are very high compared to those in surface water and in surface soil in the three (As-affected) areas studied. This indicates that the source of As in groundwater could be bedrock. The relatively high concentrations of Cr, Cu, Ni, Pb and Zn in surface water, compared to world typical value, are due to the solubility of metal ions, organometalic complexes, coprecipitation or co-existance with the colloidal clay fraction. In the soil, the elevated concentrations of As, Cr, Cu, Ni, Pb and Zn are due to their strong affinity to organic matter, hydrous oxides of Fe and Mn, and clay minerals.

The Forum of European Geological Surveys Geochemistry Task Group inventory 1994–1996

The Forum of European Geological Surveys (FOREGS) includes representatives from 33 European countries and is responsible for co-ordinating Geological Survey activities in Europe. The FOREGS Geochemistry Task Group was established in 1994 to develop a strategy for the preparation of European geochemical maps following the recommendations of the International Geological Correlation Programme (IGCP) Project 259 ‘International Geochemical Mapping’ (now the International Union of Geological Sciences (IUGS) /International Association of Geochemistry and Cosmochemistry (IAGC) Working Group on Global Geochemical Baselines). The FOREGS geochemistry programme is aimed at preparing a standardised European geochemical baseline to IGCP-259 standards. The principal aims of this dataset will be for environmental purposes, as a baseline for the assessment of the extent and distribution of contaminated land in the context of variations in the natural geochemical background, but it will also have applications in resource assessment and for the development of policy for the sustainable management of metalliferous mineral and other resources. The first phase of the programme was the compilation of an inventory of geochemical data based on the results of a questionnaire completed by Geological Surveys and related organisations throughout the FOREGS community. The results show that the sample types which have been used most extensively are stream sediment (26% coverage), surface water (19% coverage) and soil (11% coverage). Stream sediments have been collected using a narrow range of mesh sizes (< 150–< 200 μm), but soil samples have been collected according to two different conventions: some surveys used a similar mesh size range to that used for stream sediments while others employed the < 1000 or < 2000 μm fractions traditionally used by soil surveys. Sample densities range from 1 sample per 0.5 km2 to 1 per 3500 km2. Various analytical methods have been used, but most of the available data have been calibrated using international reference materials, and data for the most important of the potentially harmful elements (PHEs) are available for most datasets. Systematic radiometric data are available for only a small proportion of Europe, a situation which compares very unfavourably with that in Australia, North America, the former Soviet Union and many developing countries. Recommendations are made for increasing the compatibility of geochemical methods between national geochemical surveys as a basis for the preparation of a series of European geochemical maps. The next stage of the FOREGS Geochemistry Task Group will be the collection of the Global Reference Network of samples against which to standardise national datasets according to the methods recommended in the final report of the IGCP 259 programme.

Regional geochemical mapping of Western Europe towards the year 2000

Abstract The Directors of the Western European Geological Surveys (WEGS, presently the Forum of European Geological Surveys, FOREGS) created in 1985 a Working Group on “Regional Geochemical Mapping” for the study of different aspects of regional geochemical surveys. The Working Group proposed to the Directors a systematic low sampling density regional geochemical mapping project to obtain baseline data. Following this proposal for a systematic low sampling density regional geochemical mapping programme of Western Europe a three-year (1988–1990) Pilot Project was carried out. Its objectives were (1) to prepare an inventory of regional geochemical mapping already completed in Western Europe, and (2) to assess the scope and limitations in the use of overbank and stream sediment as sample media in wide-spaced regional geochemical mapping. Based on the results obtained in the Pilot Project, the Directors decided that more research was required before taking a final decision. The Working Group was asked to carry out further research and to submit its final report in 1993. The WEGS Working Group collected and evaluated a substantial amount of information during the pilot and research projects. This paper summarises the main results of the research work carried out from 1986 to 1992.

Application of a risk assessment method to Europe-wide geochemical baseline data

The environmental risk, defined as the possibility of impairment of biotic or abiotic components of the environment, derived from geological sources was estimated for the whole of Europe. The assessment was based on data obtained from the Geochemical Atlas of Europe and included measured total concentrations of: Al, As, B, Cd, Cr, Cu, Ni, Pb, Se, Zn, Fe, Mn, Cl, NO3 and SO4 in stream water; As, Ba, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, V and Zn in topsoil; and As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in stream and floodplain sediments. The number of sampling sites varied from 741 (stream water) to 847 (subsoil). The assessment method was based on the calculation of two-step environmental risk index values (IER) for individually analysed water, soil and sediment samples. Environmental risk quotients are first calculated for each analysed chemical element or compound that exceeds the limit for risk values, and their sum is then calculated. The risk at each site was defined and classified as negligible, low, medium, high, very high or extremely high. The results are presented as risk maps covering the 26 countries of Europe. Stream waters show a high to extremely high risk value in large areas of southern Finland and Sweden, and sporadically in Spain, southern Italy, the Netherlands, northern Germany and Denmark. Stream sediments show high risk values in Greece, Albania, Sardinia and northern Italy. The risk areas for floodplain sediment differ from those for stream sediment, with no high risk values in Sardinia, but instead in Belgium. The highest risk levels in topsoils were detected in Greece, Albania and northern Italy. The combination of all materials shows a medium-level risk throughout Europe and a high to extremely high risk in Greece, Albania, Sicily and Sardinia, and sporadically in Spain, Belgium and the Netherlands. The calculated maps delineate regions where high elevated concentrations pose a risk to the environment, or where the action limits for soil, sediment or water contamination should be revised using the high local baseline.

Niobium in boreal stream waters and brackish-water sediments

The focus is on ‘non-detrital’ Nb in boreal stream waters (dissolved fraction and acid-available particulate fraction) and brackish-water/lacustrine sediments (aqua regia extractable fraction). Spatial patterns, temporal trends and speciation experiments all point to dissolved humic substances and colloidal Fe as the main control of Nb concentrations in stream waters. In addition, clay-silt deposits and/or ore deposits may be responsible for producing local streamwater Nb anomalies. In groundwater in overburden (glacial till) overlying Proterozoic granitoids, dissolved Nb concentrations were about an order of magnitude higher than in stream waters and strongly correlated with dissolved Fe. In the brackish-water sediments, the Nb concentrations (1.33–4.20 ppm) were higher than in the lacustrine ones (0.25–0.53 ppm). To explain this, we assessed the potential role of organic material, biological processes, sulphide mineralogy, silicate mineralogy and input factors. However, none of them could satisfactorily explain the observed Nb geochemical features. Although Nb can be considered relatively immobile, the data presented in this paper show that under certain conditions its abundance in the aquatic environment increases.

Geogenic and anthropogenic zinc in epiphytic and terricolous lichens in Finland

Abstract At 31 sites in Finland the Zn content was determined of the epiphytic lichen Hypogymnia physodes (L.) Nyl. growing on pine and birch, the terricolous lichen Cladina spp. in pine bark, and the inner part of birch bark. The anomalous contents of Zn in H. physodes on pine and Cladina spp. in soil appeared to be strongly related to sulphide ore deposits. Anthropogenic Zn correlated closely with S and Fe in H. physodes on pine and with Fe in Cladina spp. The binding of geogenic Zn was related to iron hydroxides, and was attributed to the different uptake mechanism of S in these lichens. Elevated values of Zn in H. physodes on birch were due to both geogenic and anthropogenic sources. Zinc in pine bark increased with the Zn content in H. physodes and reached a limiting value.

Uranium in surface and groundwaters in Boreal Europe

ABSTRACT This study focuses on uranium (U) in surface and groundwaters in Boreal Europe (Sweden, Finland, Russia). Data from recently completed regional hydrogeochemical surveys and from site-specific studies were combined, in order to enhance the current understanding of U behaviour in the catchments and water bodies of these northerly latitudes. Over Precambrian areas (dominated by igneous and metamorphic rocks) the aqueous U concentrations in general increased in a downward direction, i.e. from stream waters to overburden groundwaters to bedrock groundwaters, and they were correlated with the U abundance in the surrounding overburden (mainly glacial till). Over Phanerozoic areas (dominated by terrigene deposits containing or composed of limestone) the aqueous U concentrations were, in contrast, unrelated to overburden U concentrations and strongly correlated with dissolved Ca and HCO3− concentrations. There is thus an overall geochemical and hydrochemical control, respectively, related to the underlying lithology. At geologically specific and local sites there is a range of correlations and control mechanisms of aqueous U. From acid sulphate soils, occurring abundantly on coastal plains, runoff below pH 4.0 is enriched in U (up to 55 μg/l) most likely due to oxidation of U(IV) minerals followed by subsequent limited sorption of U(VI) in the acidic environment. In a studied black shale setting, characterized by high U concentrations (up to >200 ppm), U levels increased in groundwater (up to 200 μg/l) and surface water (up to 80 μg/l) as the conditions changed from reducing to oxidizing. In an unmineralized granitic setting, proposed as a repository for spent nuclear fuel, elevated U concentrations in surface waters (up to 25 μg/l) reflect a regional stream-hydrochemical anomaly and in bedrock groundwaters (up to >100 μg/l), most likely mobilization of uranyl from U-rich fracture coatings. In the Baltic Sea, which has unique brackish water, the ratio of U to Cl− is similar to that in the oceans but contrasting near-coastal U trends exist, characterized by an inverse relationship between U and Cl− concentrations. These coastal-water anomalies are most likely caused by high U levels in inflowing streams, and possibly to some extent submarine discharge of U-enriched waters.

The environmental impact of sulphide mines measured with organogenic sampling media

Abstract The environmental impact of an active and an abandoned mine was studied using several different sampling media. The emphasis was on organic and organic-rich materials such as humus, moss and organic stream sediment. The chemical processes in the waste were studied in samples obtained by drilling through the waste into the ground beneath. Both total and bioavailable element concentrations were measured. The abundances of more than 30 elements were determined, but since the distribution patterns were similar, discussion in this paper is focused on As, Cd, Cu, Fe, S and Zn. The high capacity of humus, moss and organic sediments for binding heavy metals and S made them excellent media for studying the distribution of elements in the vicinity of the mining area. The airborne contamination from the active mine was detectable at distances of 2 to 3 km, but from the abandoned mines only about 100 m. The airborne distribution patterns recorded for the various elements were approximately the same for all sampling media and analytical methods.