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EXECUTIVE SUMMARY

T. Tarvainen¹ and W. De Vos²

¹Geological Survey of Finland, Espoo, Finland; ²Geological Survey of Belgium, Brussels, Belgium.

Following the publication in 2005 of Part 1 of the Geochemical Atlas of Europe, the present Part 2 concludes the formal work on this project of the EuroGeoSurveys-FOREGS Working Group on Regional Geochemical Mapping. The focus of Part 2 is on understanding and interpreting the geochemical patterns displayed on the maps at the scale of the European continent.

One of the main drivers of the FOREGS-EuroGeoSurveys mapping programme was the need for environmental geochemical baselines to assist decision-making, and to monitor future changes in the near-surface environment of the European continent. The Geological Surveys of the European countries had taken into account the growing public concern about sustaining and improving the quality of the environment, and the necessity to establish legislation and to develop policies controlling the levels of potentially harmful elements and compounds in the environment. Unfortunately the available data on existing levels of these substances were inadequate or limited spatially, and did not cover the wide variety of natural environments in Europe (Plant and Ridgeway 1990; Plant et al. 1996, 1997). The homogeneous dataset developed in the present programme is an important step towards a comprehensive coverage of the European near-surface environment. Despite the low-density sampling of soil, stream and floodplain sediments and stream water, about one sample per 5000 km², clear geochemical patterns emerge. They can be explained in terms of local or regional geological substrate, climate, vegetation, natural geochemical processes, and human influence of different types.

The EuroGeoSurveys-FOREGS research programme started in 1996 and the results are presented in more than 400 maps showing a combination of dots and colour surfaces. In this summary we try in just a few pages to illustrate the principles behind the understanding of patterns, and the possible uses that can be made of the geochemical maps and the dataset. How the maps were produced from the dataset is explained in detail in Part 1 (Tarvainen et al. 2005). We will first have a look at soil, and sediment derived from soil, and after that at stream water. For soil and water, European legislation is being prepared or implemented.

Soil contamination is a key issue addressed by many European Community policies. The 6th Environmental Action Programme stresses the need to protect soil against pollution, and to integrate environmental concerns into agricultural practice. The Commission communication on Soil Protection (‘Towards a Thematic Strategy for Soil Protection’) addresses the problem of soil contamination and the need for data and indicators at the European level (European Commission 2004). Other identified threats are erosion, decline of soil organic matter, soil biodiversity, soil sealing, compaction, floods and landslides, and salinisation. These threats were discussed in five Technical Working Groups (TWGs) led by the DG Environment, and in an Advisory Forum. The TWGs on Soil Organic Matter used the EuroGeoSurveys-FOREGS Geochemical Baseline database as one source of information on actual content of organic carbon in European soil and floodplain sediment or alluvial soil (Jones et al. 2004). Although reliable harmonised baseline data for selected soil types of Europe can be found in this dataset, further information from other soil types, such as histosols, which were not included in the FOREGS protocol, will be needed to obtain an overall picture.

In the assessment of potentially contaminated land, baseline concentrations should always be considered. The maps of the Geochemical Atlas of Europe show that baseline concentrations used as reference values in one country cannot generally be applied in other countries. As an example, refer to the subsoil map of nickel (Ni, map p. 357 in Part 1) reveals that the Ni content in Poland is generally in the order of 7 to 14 mg kg^-1 (blue colours on the map), whereas the Ni level in Greece is mostly above 100 mg kg^-1, or roughly a difference by a factor of 10 between these two countries. A similar relation is observed for Ni in topsoil (map p.359 in Part 1), stream sediment (p.363) and floodplain sediment (p.365), all materials ultimately derived from the bedrock. The fundamental reason for this strong contrast is the geological substrate: Greece has many outcrops of ultramafic rocks, which are rich in the elements nickel, chromium, magnesium, cobalt and iron, among others, and also Fe-Ni mineralisation. In contrast, the largest part of Poland is covered with silica-rich glacial deposits dating from the Quaternary ice age, where the same elements are present in much lower concentrations. The example of nickel is rather extreme, but it illustrates the large regional diversity of European geology. Intuitively, it can be appreciated that human-made nickel pollution in Poland would be very easy to spot, but the same pollution would be more difficult to detect in Greece. And finally it shows the difficulty of applying the same criteria in both countries in establishing guideline or threshold values for elements of environmental concern.

If we turn our focus to the increase of heavy metal content in some natural materials, we can find some good examples in lead and cadmium. Let us refer to the subsoil map of lead (Pb, map p.373 in Part 1). Subsoil Pb content in Poland or Lithuania is mostly in the range of 10 to 14 mg kg^-1 (blue colours on the map), whereas in Italy or southern France the Pb concentration is mostly in the order of 20 to 50 mg kg^-1, with exceptions reaching a level above 70 mg kg^-1 (orange and red colours on the map). Again, variation in the composition of the geological substrate or bedrock accounts for the difference. From the same map, a different statistic can be extracted. By convention, when drawing the geochemical distribution maps, the darkest red colour is designed to represent the highest 5% of the sampled points: in the case of lead in subsoil 5% of the samples in Europe contain more than 46 mg kg-1. By comparison, the topsoil map of Pb (p.375, Part 1) shows that 5% of the samples contain more than 70 mg kg-1 Pb, and 15% of the samples contain more than 42 mg kg^-1 Pb (the two darkest red colours). The inescapable conclusion is that topsoil (the surficial part of soil) is enriched in Pb compared to subsoil (the deeper soil, closer to the natural bedrock). Map 11 in Part 2 shows the ratio topsoil/subsoil for Pb: large areas of central and southern Europe show Pb enrichment in topsoil (orange and red colours). The probable main cause of this enrichment is contamination by human activities and is related to the abundance of organic matter. The maps of stream sediment (p.379 in Part 1) and floodplain sediment (p. 381) show similar higher Pb contents when compared to subsoil values. These sediments represent geological materials which, after weathering and soil formation, were eroded, transported (generally by water), and redeposited; they have thus been exposed to external agents on the surface of the earth on their way to becoming sediments, in contrast to subsoil which is more pristine. During this exposure, lead has been added from diverse sources. In the case of floodplain sediment, material from a large catchment basin is deposited over a wide alluvial plain, thus spreading potential contamination. For several heavy metals, including Pb, mining and smelting activities in historical mining areas contributed to downstream enrichment of metals in sediment (examples are to be found in the above-mentioned Pb maps in northern England, in the border area of Germany and the Czech Republic, in the southern Massif Central in France, in Sardinia, Tuscany in Italy, and near Athens in Greece).

An even better illustration of enrichment in the secondary environment is to be found for the element cadmium (Cd, map 4 in Part 2): in large parts of north-central Europe topsoil contains more than two times the Cd concentration in subsoil. A combination of natural and human-related reasons seems to be responsible for this enrichment – see the explanation in the section on Cd in soil. The Cd pattern in floodplain sediment of central Europe (map p.168 in Part 1) is difficult to explain by natural causes alone, and suggests that anthropogenic sources provide the explanation. Other elements with strong enrichment in topsoil relative to subsoil are mercury (Hg, map 7 in Part 2) and phosphorus (analysed as the oxide P₂O₅, map 10 in Part 2). For the latter, the use of phosphate fertilisers in agriculture is certainly the main contribution to the observed patterns. Fertiliser use also automatically increases the content of many trace elements present in natural and artificial fertiliser, first in soil, then in sediment derived from this soil.

Maximum permissible levels of heavy metals in soil were established by EU Directive 86/278/EEC and Sludge Use in Agriculture Regulations (1989, 1999). For example, limits established for lead (Pb) ranged from 50 to 300 mg kg^-1 depending on the pH. As stated above, heavy metal concentration in soil has a natural component; sources of contamination other than sewage sludge include atmospheric deposition arising from traffic and industrial emissions. The new EU Directive on sewage sludge, under development, regulates the use of sludge, establishes the maximum allowed concentration of heavy metals, and also aims to prevent the accumulation of heavy metals in soil. The European Environment Agency has used the FOREGS-EuroGeoSurveys Geochemical Baseline Database together with other data sources such as the EIONET questionnaire to define an indicator on lead accumulation in agricultural topsoil (European Environment Agency 2005). Relatively high Pb concentrations in topsoil (>50 mg kg-1) with clear enrichment in topsoil (enrichment factor >3, see map 11 in Part 2) are found only in restricted areas in central Europe and in Spain.

The maps of the present Atlas can also be used to delineate geochemical provinces, i.e., regions with certain natural geochemical characteristics clearly different from neighbouring regions. Some examples will illustrate this phenomenon. The subsoil maps of potassium (K₂O, p.295 in Part 1) and the trace element rubidium (Rb, p.393 in Part 1) show that felsic crystalline massifs in Sweden, the Massif Central in France and the Iberian Massif in west Spain and north Portugal are naturally rich in K and Rb. Several other elements, such as beryllium (Be), tin (Sn) and uranium (U), are naturally associated with these elements and this type of lithology generally. From the viewpoint of mineral resources, these regions constitute the best places to search for mineral deposits of these specialised and rare metals.

An interesting lithological contrast is the one existing between calcium-rich carbonate rocks and siliceous rocks. The subsoil Ca map (p.157 in Part 1) and the floodplain sediment Ca map (p.161) show large areas in eastern Spain, south-eastern France and Italy in red colours (rich in calcium), whereas the same areas are blue on the corresponding silicon maps (low in SiO₂) – see maps on p.413 and p.417 in Part 1. As carbonate rocks are alkaline, and siliceous rocks are more felsic, it should come as no surprise that a close relation exists between pH and Ca content. Refer to the subsoil pH map (p.383 in Part 1) to observe alkaline conditions (blue colours) in eastern Spain and Italy among others, are caused, as expected, by the high Ca content. Finally, calcium (Ca) and silicon (Si), together with aluminium (Al), constitute the major elements in most rocks, soils and sediments. For the lay reader, it may be useful to read the introductory paragraphs on these three elements first, in order to appreciate the lithological diversity underlying the geochemical contrasts of our continent.

Turning our attention to stream water, let us first observe how different the geochemical patterns in water can be from those in solid sample media discussed above. Such a good case to illustrate this point is the major element aluminium. The stream water map of Al (p.113 in Part 1) shows high Al concentrations in Norway, Sweden and Finland, which do not correspond to comparable high values in soil (maps on p.111 and 112 in Part 1) and sediment (Annex 6 - Al in Part 2, and p.115 in Part 1). It appears that the solubility of Al in stream water is strongly controlled by acidity (pH, map p.385 in Part 1) and dissolved organic carbon (DOC, map p.153), both favouring the mobilisation of Al in Fennoscandia. Climate is co-responsible with siliceous lithology (no alkaline buffer capacity) for the high acidity of soil and water in Fennoscandia, whereas climate (cool and wet) and vegetation are the main factors influencing DOC in stream water. It is no exaggeration to state that external controls have taken over from geology as the main agents influencing the distribution patterns of Al in stream water, but still these agents are mostly natural and not controlled by human activity. For many elements, a similar contrast between stream water and the solid sample media will be found in the geochemical dispersion maps, albeit for very diverse reasons, including human intervention.

During the early implementation phase of the EU Water Framework Directive, the Expert Group on Analysis and Monitoring of Priority Substances tried to elucidate background concentrations for dissolved heavy metals applicable to a larger part of Europe. In 2004, the Expert Group defined “the background concentration of target metals (Pb, Cd, Ni, Hg) in the aquatic ecosystems of a river basin, river sub-basin or river basin management area” as “that concentration in the present or past corresponding to very low anthropogenic pressure”. The most important database used in the evaluation was the FOREGS-EuroGeoSurveys Geochemical Baseline Database. According to the Expert Group, the EuroGeoSurveys-FOREGS data represent the most extensive, robust, spatially-relevant database for dissolved metal concentrations of Pb, Cd and Ni in stream water on the European scale (European Communities 2005).

As shown by several examples above, the natural background concentrations of nutrients and potentially harmful elements differ so much at the regional and continental scale that any Europe-wide legislation concerning soil and water should take into account both the natural geological background and the baselines, which in part result from past human interference. The adoption of guideline or threshold values based only on ecotoxicological data or on baselines of countries with exceptionally low natural trace element concentrations, such as the Netherlands or Poland, can lead to erroneous assessment of regions with naturally high baselines derived from the geological substrate.

Elevated nitrate concentration in surface and groundwater is one of the continent wide environmental problems discussed in the thematic Nitrates Directive (91/676/EEC). The map of nitrate in stream water (p.367 in Part 1) shows the results of a homogeneous dataset pointing out a rather systematic increase of nitrate, especially in western and central Europe. There is no doubt that this is caused by agricultural practices.

European countries have agreed to limit their emissions of acidifying substances in the UN ECE Convention on Long-Range Transboundary Air Pollution. Differences between pH values in soil and surface water and the buffer capacity of water (HCO3-) vary greatly within our continent. Notably, the soil and surface water of northern Europe have low (acidic) pH values (map p.385 in Part 1) and low alkalinity (map p.267 in Part 1). Critical load models have been successfully applied to acidifying components. The FOREGS-EuroGeoSurveys data could be used to evaluate the models, and provide a natural baseline to be compared with the modelled heavy metal input

In many cases, the high natural total concentrations of heavy metals and other potentially harmful elements in soil and sediment are strongly bound in minerals of low solubility and do not pose a major threat to humans or the environment. However, for example, in the Tampere region in Finland, elevated soil arsenic (As) levels can be used to delineate risk areas of arsenic-containing groundwater. High concentrations of arsenic in groundwater can pose a health risk, and this problem is being assessed in the EU-funded Life programme RAMAS project (http://www.gtk.fi/projects/ramas/index.php?lang=en). The Geochemical Atlas of Europe shows the areas in Europe where the potential health risk of arsenic (map p.119 in Part 1) and other harmful substances should be investigated. The potential risk of geologically derived harmful elements should be included routinely in land planning as well. This can be a new topic to be studied in future projects of the European Spatial Planning and Observation Network (ESPON, http://www.espon.lu/).

Finally, the aim of the Infrastructure for Spatial information in Europe (INSPIRE) initiative is to make available relevant, interoperable and/or harmonised quality geographical information to support formulation, implementation, monitoring and evaluation of Community policies with a territorial dimension (http://inspire.jrc.it/). With the present Geochemical Atlas of Europe, the EuroGeoSurveys-FOREGS Geochemistry Working Group has developed a real Europe-wide georeferenced harmonised dataset that is permanently available to support the aims of the INSPIRE initiative (http://www.gtk.fi/publ/foregsatlas/). Moreover, it is the first continent-wide step that can be updated at any time in the future in order to create a timeline designed to monitor changes in our near-surface environment. In the meantime, all the analytical data, photographs of sampling sites, printed pages, publications, tables, maps and figures resulting from the EuroGeoSurveys-FOREGS geochemical mapping programme will be freely available from the Internet and a sample archive is being maintained for future reference.

References

European Communities, 2004. Reports of the Technical Working Groups established under the Thematic Strategy for Soil Protection: Volume I - Introduction and executive summary (EUR 21319 EN/1). Volume II – Erosion (EUR 21319 EN/2). Volume III - Organic Matter and Biodiversity (EUR 21319 EN/3). Volume IV - Contamination and Land Management (EUR 21319 EN/4). Volume V – Monitoring (EUR 21319 EN/5). Volume VI - Research, Sealing and Cross-Cutting Issues (EUR 21319 EN/6). All reports are available in pdf format from URL (Point 17 in the list): http://eusoils.jrc.it/ESDB_Archive/eusoils_docs/doc.html#OtherReports

European Communities, 2005. Contributions of the Expert Group on Analysis and Monitoring of Priority Substances, AMPS to the Water Framework Directive Expert Advisory Forum on Priority Substances and Pollution Control". EUR 21587 EN, 133 pp.

European Environment Agency, 2005. The European Environment – State and Outlook 2005. Copenhagen: EEA. 570 pp.

Internet: website of the FOREGS-EuroGeoSurveys geochemical project: http://www.gtk.fi/publ/foregsatlas/

Jones, R.J.A., Yli-Halla, M, Demetriades, A., Leifeld, J. & Robert, M., 2004. Organic Matter and Biodiversity: Task Group 2 on Status and Distribution of Soil Organic Matter in Europe. In: L. Van-Camp, B. Bujarrabal, A.R. Gentile, R.J.A. Jones, L. Montanarella, C. Olazabal. & S.-K. Selvaradjou (Editors), Reports of the Technical Working Groups established under the Thematic Strategy for Soil Protection, Volume III, Organic Matter. European Commission, Director General, Joint Research Centre, European Environmental Agency, Ispra-Copenhagen EUR 21319 EN/3: 27-50.

Plant, J.A. & Ridgeway, J., 1990. Inventory of geochemical surveys of Western Europe. In: A. Demetriades, R.T. Ottesen & J. Locutura (Eds.), Geochemical Mapping of Western Europe towards the Year 2000. Pilot Project Report. Western European Geological Surveys, Geological Survey of Norway, NGU Report 90-105, Appendix Report 10, 20 pp.

Plant, J.A., Klaver, G., Locutura, J., Salminen, R., Vrana, K. & Fordyce, F., 1996. Forum of European Geological Surveys (FOREGS), Geochemistry Task Group 1994-1996 Report. A contribution to IUGS Continental Geochemical Baselines. British Geological Survey, Keyworth, Nottingham, U.K., BGS Technical Report WP/95/14, 52 pp.

Plant, J.A., Klaver, G., Locutura, J., Salminen, R., Vrana, K. & Fordyce, F., 1997. The Forum of European Geological Surveys Geochemistry Task Group inventory 1994-1996. Journal of Geochemical Exploration, 59(2), 123-146.

Tarvainen, T., Reeder, S. & Albanese, S., 2005. Database management and map production. In: R. Salminen, R. (Chief-editor), M.J. Batista, M. Bidovec, A. Demetriades, B. De Vivo, W. De Vos, M. Duris, A. Gilucis, V. Gregorauskiene, J. Halamic, P. Heitzmann, A. Lima, G. Jordan, G. Klaver, P. Klein, J. Lis, J. Locutura, K. Marsina, A. Mazreku, P.J. O’Connor, S.Å. Olsson, R.T. Ottesen, V. Petersell, J.A. Plant, S. Reeder, I. Salpeteur, H. Sandström, U. Siewers, A. Steenfelt, & T. Tarvainen, FOREGS Geochemical Atlas of Europe, Part 1: Background Information, Methodology and Maps. Geological Survey of Finland, Espoo, 95-108.

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