Scientific registration number: 2022 Syposium n o : 25 Presentation: poster. ERIKSSON Jan, ANDERSON Arne, ANDERSSON Rune.

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1 Scientific registration number: 2022 Syposium n o : 25 Presentation: poster Trace element concentrations in Swedish agricultural soils as affected by parent material and anthropogenic sources Concentrations en éléments-traces métalliques dans les sols agricoles de Suéde en relation avec le matériau parental et les apports anthropiques ERIKSSON Jan, ANDERSON Arne, ANDERSSON Rune. Department of Soil Sciences, Swedish University of Agricultural Sciences, P. O. Box 7014, S Uppsala, Sweden. Introduction This paper presents a study of trace element concentrations in Swedish agricultural soils, their geographic variation and correlation to parent material and depositional patterns. The study on trace elements is part of a more extensive project aimed at mapping the current status agricultural soils with regard to humus content, nutrient status, base cation content and ph. Materials and methods The study includes plough-layer samples (0-20 cm) and subsoil samples (40-60 cm) from sampling sites randomly distributed throughout the major agricultural areas in Sweden. Plough-layer samples were collected from 1988 through 1995, although most were collected during Subsoil samples were taken in Each plough-layer sample represents around 900 ha. Sampling was made with an auger and soil samples were dried at o C and passed through a 2 mm sieve. As, Cd, Co, Cr, Cs, Cu, Hg, Mo, Mn, Ni, Pb, Sr, V and Zn were extracted with 7 M HNO3 for 30 min. at 120 o C and 200 kpa in an autoclave. Selenium was extracted in aqua regia with a method suggested in Application Note 015 from PS Analytical Ltd, Orpington, Kent, Great Britain. Mercury in the extracts were determined with atomic fluorescense spectrometry (AFS). Se was determined with AFS after hydride generation. Other trace elements were determined with ICP-AES or ICP-MS. Choice of ICP tecnique was determined by the concentration level in each single sample. 1

2 Results and discussion Data on trace element concentrations in the plough-layer of Swedish agricultural soils are presented in Table 1. Table 1. Trace element concentrations (mg kg -1 dw) in the plough-layer of Swedish arable land. The number of observations is As Cd Co Cs Cu Cr Hg Mn Min <0.1 <0.1 < < Max Mean Std Median Mo Ni Pb Se Sr V Zn Min < Max Mean Std Median Cadmium concentrations above average in the plough-layer are present in southernmost Sweden (Skåne), in the plain districts in eastern Sweden west and southwest from Stockholm and in Jämtland county in the inland in the middle of Sweden (Fig. 1). Cadmium concentrations in the subsoil are in most part of Sweden considerably lower than in the plough-layer, but areas with the highest concentrations in the plough-layer usually had high levels also in the subsoil. On average the Cd concentrations in the plough-layer are 61 % higher than those in the subsoil. The mercury concentrations in the plough-layer varies in a rather irregular pattern, but there is a tendency to a gradient with decreasing concentrations to the north (Fig. 1). Average concentrations in the subsoil are considerably lower than those in the plough-layer. However there are some spots with high concentration in the subsoil. On average the Hg concentrations in the plough-layer are 251 % higher than those in the subsoil. Lead concentrations in the plough-layer above average are common in the eastern part of Sweden, especially along Lake Mälaren west of Stockholm (Fig 2). High concentrations in the subsoil in these areas indicate that a large part of the Pb content derives from the parent material. Above average concentrations were also recorded along the west coast of Sweden, but in that area elvated concentrations were not present in the subsoil. On average the Pb concentrations in the plough-layer are 24 % higher than those in the subsoil. It can be assumed that the subsoil is considerably less influenced by soil forming processes and anthropogenic supply than the plough-layer. Thus the good correlation between concentrations in plough-layer and subsoil indicate that Cd, Hg and Pb concentrations in Swedish 2

3 agricultural soils are determined to a large degree by the parent material. The spots with the higest Cd concentrations in the subsoil are those that are influenced by alum shale rich parent material (Fig. 3). Also high Hg and Pb concentration are related to influence by alum shale rich parent material, and this is also the case for As, Cu, Mn, Se and Zn in our investigation. Another important factor influencing trace element concentrations is the organic matter content of the soil. Some of the spots in South Sweden where elevated Cd and Hg concentrations are not related to presence of alum shale, are situated in areas where organic soils are frequent. Of the heavy metals studied Hg and Cd show the strongest correlation to soil organic matter content (r=0.58 and r=0.44 respectively). Also Se concentrations are strongly correlated to soil organic matter contents (r=0.62). The generally elevated trace element contents in Jämtland in the middle of Sweden seem to be a combination of influence from alum shale rich parent material an high frequency of organic matter rich soils. Elevated contents of especially Pb but also of Cd east and southeast of Stockholm are probably partly explained by frequent very clayey soils in these areas. However, there are also indications that these soils which formed from Baltic sediments generally have higher levels than the marine clays along parts of the west coast. At present we cannot explain this difference between the different types of sediments. Also Cr, Cu and Zn concentrations are elevated in the same way as Pb in the Baltic clays. The lowest trace element concentrations are generally found in inland areas where soils are usually coarser textured. Influences from deposition are not so easy to recognize on the maps sice they are superimposed on the pattern determined by the nature of the parent material. However, in southeastern Sweden Pb and Cd concentrations are elevated in the plough-layer but not in the subsoil. This part of Sweden is the one where deposition of these and many other elements has generally been the highest due to effect of long-range transport from industrial areas in Western Europe (Monitor, 1987; Nord, 1992). Also the tendency of generally higher Hg concentrations in the plough-layer in South Sweden than in North Sweden is presumably a deposition gradient. Table 2 shows concentrations in the plough-layer and the subsoil. The correlation between concentrations in the two layers is strong showing the importance of the parent material. The relative difference in concentration between top soil and subsoil gives an estimate of the the accumulation of the elements in the top soil since the land was raised above sea level by land rise or alternatively, for soils above the highest coast line, since the latest ice-age. These figures can be compared with the estimated average increases in the trace metal contents in the plough-layer of Swedish agricultural soils during the 20 th century, mainly induced by anthropogenic input. The elements with the largest anthropogenic input to soils are Hg, Cd and Pb. Acccording to Andersson (1992) the contents of these elements have increased with 46, 33 and 14 % from 1900 through As already mentioned these elements also show higher concentrations in the plough-layer compared to the subsoil. 3

4 Table 2. Trace element concentrations (mg kg -1 dw) in plough-layer and subsoil, estimated increase in concentrations (Andersson, 1992) and correlations between concentrations in the plough-layer and subsoil for each variable. The number of observations is A correlation coefficient larger than 0.04 is significant at the 5 % level. As Cd Cr Cu Hg Mn Mo Ni Pb Zn Top soil Mean Subsoil Mean Top soil/subsoil (%) Increase, (%) Correlation (r), top soil-subsoil Especially for Pb and Hg comparison of concentrations in plough-layer and subsoil should give a rather reliable estimate of total external inputs. Crop uptake of these elements is negligible (Tjell et al, 1979; Mosbaek et al, 1982). Therefore tranfer from the subsoil to the top soil via crops is small. Thus, if concentrations initially were the same, higher contents in the plough-layer can mainly be ascribed to supply from above-ground anthropogenic and natural sources. The fact that the difference in concentration, especially for Hg, between top soil and subsoil is substantially larger than the calculated anthro-pogenic input during the 20 th century, is probably due to a significant deposition of this element also before this century. Mercury is added to the air from e. g. volcanic activity and Lindqvist et al (1991) in a literature review suggest 6 g km -2 as a resonable figure for natural global emissions. According to Aastrup et al (1991) the total depositon of Hg in southern Sweden, including supply from anthropogenic sources, is 20 mg km -1. The figures are uncertain and presumably some of the Hg added to the soil in historic time has disappeared again through vaporization. However they indicate that a considerable accumulation may have taken place for a long time. Anthropogenic supplies of Pb via deposition since roman times has been shown by Renberg et al (1994) after analyzing lake sediment cores. There may also have been pre-idustrial emissions of Hg and Cd to air in connection with activities to extract metals from sufide ores. Both elements are accumulated in sufides and especially Hg but also Cd is volatile. For cadmium the interpretation of differences between plough-layer and subsoil is a little more uncertain. Cadmium is less strongly adsorbed to soil than other heavy metals and therefore more mobile. More Cd is therefore presumably transported downward in the soil profile, leading to an increase of concentrations in the subsoil. On the other hand Cd is more plant available than Hg and Pb and the transloction from subsoil to top soil via root uptake and litterfall may be more significant for Cd than for the other metals. For Zn and Cu estimation of external supplies is very difficult as these elements are important plant nutrients taking part in an internal circulation in the agricultural system; soil-root-crop and back to soil via crop residues and manure. 4

5 Some elements show higher concentrations in the subsoil than in the top soil. External inputs of these elements have been low. For geological and colloid chemical reasons clay content in Swedish soils tend to be higher in the subsoil than in the top soil. Higher clay content usually means higher trace metal concentrations especially for elements like Cr, Cu, Ni, Mn, and Zn with a ionic radius making them fit into the structure of silicate clays and sesquioxides (Andersson, 1979). The extraction method we use also tend to be more efficient on clay soils than on coarser textured soils. Conclusions Geographic variation in trace element concentrations in Swedish soils are to a large extent determined by the nature of the parent material. However concentrations of Hg, Cd and Pb have also been influenced by external supplies in the form of atmospheric deposition, seed disinfectant (only Hg) and phosphorous fertilizer (main source for Cd). Supplies in the form of atmospheric deposition could be of natural (especially for Hg) as well as anthropogenic origin. References Aastrup M, Johnsson J, Bringmark E, Bringmark L och Iverfeldt Å (1991): Occurrence and transport of mercury within a small catchment area. Water, Air and Soil Pollution 56, Andersson A (1979): On the distribution of heavy metals as compared to some other elements between grain size fractions in soils. Swedish J. agric. Res. 9, Andersson A, Dahlman B, Gee D G & Snäll S (1985): The Scandinavian alum shales. SGU, Ser Ca 56. Andersson A (1992): Trace elements in agricultural soils - fluxes, balances and background values. Swedish Environmental Protection Agency, report Lindqvist O, Johansson K, Aastrup M, Andersson A, Bringmark L, Hovsenius G, Håkansson L, Iverfeldt Å, Meili M och Timm B (1991): Mercury in the Swedish Environment - Recent research on causes, consequences and corrective methods. Water, Air and Soil Pollution 55, Monitor (1987): Tungmetaller förekomst och omsättning i naturen. Naturvårdsverket. (in Swedish) Mosbaek H, Tjell J C & Hovmand M F (1982): Atmospheric deposition of trace elements on agricultural soils and plants. In: Newsletter from the FAO European Cooperative Network on Trace Elements, First Issue, State University Gent, Belgium. Nord (1992): Atmospheric Heavy Metal Deposition in Northern Europe Nord 1992:12, Nordic Council of Ministers, Copenhagen. Renberg I, Wik S, Persson M & Emteryd O (1994): Pre-industrial atmospheric lead contamination detected i Swedish lake sediments. Nature 368, Tjell J C, Hovmand M F & Mosbaek H (1979): Atmospheric lead pollution of grass grown in a background area in Denmark. Nature 280, Key words: agricultural soils, trace elements, parent material, anthropogenic supply, deposition Mots clés : sols agricoles, éléments traces, matériau parental, source anthropique, dépôt 5

Rufus L. Chaney, USDA-ARS, Beltsville, MD Michelle Mahoney, John Schmeltzer, Gary Newheart Harry Compton, Mark Sprenger

Biosolids and Revegetation Addressing Contaminants: Ecosystem Revitalization of the Long-Barren Serpentine Mine Waste at the Vermont Asbestos Group Mine Rufus L. Chaney, USDA-ARS, Beltsville, MD Michelle