Mercury in European agricultural and grazing land soils

doi:10.1016/j.apgeochem.2012.12.013

Applied Geochemistry

Volume 33, June 2013, Pages 1-12

https://doi.org/10.1016/j.apgeochem.2012.12.013 Get rights and content

Abstract

Agricultural (Ap, A_p-horizon, 0–20 cm) and grazing land soil samples (Gr, 0–10 cm) were collected from a large part of Europe (33 countries, 5.6 million km²) at an average density of 1 sample site/2500 km². The resulting more than 2 × 2000 soil samples were air dried, sieved to <2 mm and analysed for their Hg concentrations following an aqua regia extraction. Median concentrations for Hg are 0.030 mg/kg (range: <0.003–1.56 mg/kg) for the Ap samples and 0.035 mg/kg (range: <0.003–3.12 mg/kg) for the Gr samples. Only 5 Ap and 10 Gr samples returned Hg concentrations above 1 mg/kg. In the geochemical maps the continental-scale distribution of the element is clearly dominated by geology. Climate exerts an important influence. Mercury accumulates in those areas of northern Europe where a wet and cold climate favours the build-up of soil organic material. Typical anthropogenic sources like coal-fired power plants, waste incinerators, chlor-alkali plants, metal smelters and urban agglomerations are hardly visible at continental scales but can have a major impact at the local-scale.

Highlights

► Mercury concentrations in agricultural and grazing land soil of Europe are presented. ► The paper presents the Hg-background for two types of soil-use at the European scale. ► Geology and climate dominate the continental-scale Hg distribution. ► Anthropogenic Hg sources are visible on a local scale.

Introduction

Over the last 30 years, there has been much concern regarding the toxic impact of mercury (Hg) in the ecosystem due to its mobility and volatility, and potential for methylation and bioaccumulation. For example, Hg in fish is a great problem in the Nordic countries (Fjeld and Rognerud, 2009).

The EU repeatedly requested the UNEP Governing Council to take a decision on the opening of negotiations on a global legally binding instrument on Hg. In February 2009, the Governing Council finally decided to establish an Intergovernmental Negotiating Committee (INC) mandated for developing a global legally binding instrument covering most aspects of the Hg life cycle. The first session of the INC took place in Stockholm, 7–11 June 2010, with the objective of concluding early in 2013. The European Strategy on Hg and its implementation aims at making a significant contribution to this process. Despite all these discussions the distribution and natural background of Hg in, e.g., agricultural and grazing land soils, has never been mapped and documented at the continental-scale and thus the base for guided political decisions is missing.

Major Hg mines in Europe were situated in Spain (Almaden), Slovenia (Idria) and Italy (Monte Amiata), however mining of Hg terminated in the EU in 2003. Global Hg supply to the markets is now dominated by three nations that mine mercury for export: Kyrgyzstan, Algeria and China. China may be in the process of closing their mines, especially as other sources of Hg appear to be growing, and mercury remains inexpensive on the international market.

EuroGeoSurveys (EGS) is a forum for cooperation between the 34 geological surveys of Europe. EGS, in cooperation with Eurometaux, the association of the European metal producers, initiated in 2008 a project to document metal concentrations in European agricultural and grazing land soils at the continental-scale. Sampling was organised, conducted and financed by the local Geological Surveys and partner organisations while Eurometaux financed sample preparation and the chemical analysis of about 60 chemical elements, including Hg. The overall project management lies with the Geological Survey of Norway (NGU).

This article presents the analytical results for Hg from >4000 soil samples, evenly distributed over Europe and discusses the importance of natural versus anthropogenic sources and processes on the regional distribution of this element in European topsoil.

Fig. 1 provides a simplified geological map of Europe, showing the main features discussed in this paper. Further maps covering topography and land use of Europe can be found in almost any world atlas. For Europe, an excellent source of land use information is the CORINE land use map of Europe (GLC2000 Database, 2003). A detailed geological map of Europe is provided by Asch (2003), concise descriptions of the geology of Europe can be found in Blundell et al. (1992) and McCann (2008). The soil atlas of Europe provides a wealth of information about the soils of Europe, but also contains maps of average precipitation, temperature, land use, population density, extent of the last glaciation and soil texture (Jones et al., 2005). A number of maps covering different themes at about the scale of the GEMAS project (topography, geology, tectonics, fault and fracture zones, distribution of different rock types, distribution of the main sedimentary basins, precipitation and population density) can be found in Reimann and Birke (2010).

Section snippets

Sampling

Two thousand one hundred and eight samples of agricultural soil (A_p-horizon, 0–20 cm, Ap samples) and 2024 samples of grazing land soil (0–10 cm, Gr samples) were collected during 2008 from large parts of Europe, with some few last samples arriving early in 2009. No samples were taken in Albania, Belarus, Malta, Moldova, Rumania, and Russia. Each sample was a composite of five single samples taken about 10 m apart from a large ploughed field or patch of grazing land. The average sample weight was

Mercury concentrations in European agricultural and grazing land soils

Table 1 summarises the Hg results for the European Ap and Gr samples. Fig. 3 shows the Hg distribution of the Ap and Gr soil samples in the form of a combined histogram, density trace, boxplot and one-dimensional scattergram. Both plots demonstrate that there is a small group of samples below detection (0.76% for the Ap samples and 0.35% for the Gr samples, see Table 1). The boxplot and one-dimensional scattergram indicate the presence of a limited number of upper and lower outliers (Fig. 3).

General patterns in the maps

When studying the map (Fig. 5) it is at first glance tempting to assign the almost double as high median Hg concentration in Central Europe to an overall higher level of contamination of Central European agricultural soils with Hg. However, the patterns on the map cannot really be explained by the impact on the soils of anthropogenic activities or long (or even short) range transport of Hg via the atmosphere. The concentration break along the glacial boundary is clearly related to geology and

Conclusions

Overall Hg levels in European agricultural soils are low (median agricultural soil (Ap) 0.030 mg/kg, median grazing land soil (Gr) 0.035 mg/kg). The statistically significantly higher median in the grazing land soil samples is related to the substantially higher amount of organic material in the grazing land soils (median TOC Gr: 2.7 wt.% versus median TOC Ap: 1.8 wt.%).

The strong link of Hg with organic material is also visible in the relatively high Hg levels in the Scandinavian soils. Here many

Acknowledgements

The GEMAS project is a cooperation project of the EuroGeoSurveys Geochemistry Expert Group with a number of outside organisations (e.g., Alterra in The Netherlands, the Norwegian Forest and Landscape Institute, several Ministries of the Environment and University Departments of Geosciences in a number of European countries, CSIRO Land and Water in Adelaide, Australia) and Eurometaux. The analytical work was co-financed by the following organisations: Eurometaux, Cobalt Development Institute

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Mercury in European agricultural and grazing land soils

Abstract

Highlights

Introduction

Section snippets

Sampling

Mercury concentrations in European agricultural and grazing land soils

General patterns in the maps

Conclusions

Acknowledgements

Sci. Total Environ.

J. Geochem. Explor.

J. Geochem. Explor.

Sci. Total Environ.

Geoderma

Appl. Geochem.

Appl. Geochem.

Sci. Total Environ.

Appl. Geochem.

Applied Geochemistry

J. Geochem. Explor.

Appl. Geochem.

Sci. Total Environ.

The Statistical Analysis of Compositional Data

Carte du mercure dans l’horizon de surface des sols agricoles dans le centre du bassin parisien

Etude et gestion des sols

Mercury speciation in sediments affected by dumped mining residues in the drainage area of the Idrija mercury mine, Slovenia

Environ. Sci. Technol.

Urban geochemistry of Berlin, Germany

A Continent Revealed: The European Geotraverse

Geochemical Atlas of Cyprus

Mercury in river sediments, floodplains and plants growing thereon in drainage area of Idrija Mine, Slovenia

Pol. J. Environ. Stud.