v
I
THE MOBILITY OF HEAVY METALS IN SOILS IN THE KRUSNE
HORY AND SLAVKOVSKY LES MOUNTAINS BOHUMILA BEZVODOVA Czech Ecological Institute, Prague, Czech Republic
Abstract. In the North Bohemian forest soils the total content and EDTA, HAc and H20-extractable portions of Cr, Co, Ni, Cu, Pb and Zn were investigated. Increased concentration of Pb in topsoils, in comparison with subsoils, is the result of air pollution. The extractable portion of all studied heavy metals is higher in topsoil than in subsoil.
1. Introduction Many heavy metals are biogene elements, i.e. they occur in limited amounts in living organisms and play specific roles in them. However, higher concentrations can cause complications. In recent years, due to human activity, some heavy metals accumulate in topsoil, penetrate into the food chain and affect human health. There are two ways that heavy metals can move from soils into the food chain: soilplant, and soil-drinking water. Both pathways dePend upon the transfer of heavy metals from solid components to the soil solution. The reactions involved are Very complex, with the rate of transfer depending on many factors, mainly on the binding mechanisms of heavy metals in soil solids, and on the amount and composition of the liquid phase (Bruemmer et al., 1986). In the literature it is possible to find many papers on this topic, often with controversial results. For practical purposes, acceptable limits for heavy metals in soils were introduced. These limits change from c~untry and/or extractable amounts. The advantage of total content of heavy metal in soil is the comparability of the determined values all over the world. The advantage of determining extractable soil metal is that information is obtained about the mobility and availability of the metals. However, the disadvantage of the latter approach is the dependence on extraction methodology.
2. Area of Interest and Methods Used Soils in the Kru~n6 Hory and Slavkovsk)~ Les mountains were used for this study. Both mountain areas are situated on the N and NW boundary of the Czech Republic at an altitude of about 700 m. Both areas are covered by damaged, in some places dead, forest. In the Slavkovsk~ Les mountains the parent rock is mainly granite, on which the brown podzolic soils are developed. One locality is formed of serpentinite with pararendzina on it. In the Km~n6 Hory mountains, brown soils cover weathered gneisses. For the purpose of this investigation 9 test pits were dug (6 in Kru~n6 Environmental Monitoring and Assessment 34:163-166, 1995. (~) 1995 Kluwer Academic Publishers. Printed in the Netherlands.
164
BOHUMILABEZVODOV./~
Hory mountains and 3 in Slavkovsk3) Les mountains). Each locality was sampled in accordance with the soil horizons to follow the heavy metals distribution in the whole soil profile. Laboratory analyses were made on the grain size fraction of less than 2 mm. The total contents were determined by X-ray fluorescence (XRF). The extractable content was received using 0.05 M EDTA (ethylene diamine tetraacetic acid), HAc (acetic acid) according Berrow and Ure (1985), and distilled water (5 g/100 ml, shake 1 h, leaching 24 hs). The concentrations were determined using atomic absorption spectrometry (AAS). 3. Results
3.1. CHROMIUM,COBALTAND NICKEL The concentration of these elements is evidently determined primarily by the parent rock composition. Co was found only in pararendzine on serpentinite (total content, 5-40 ppm). Cr and Ni contents are considerable higher in the pararendzine on serpentinite (total Cr content, 145-405 ppm, total Ni content, 186-490 ppm) than in other soils, where the total concentration of Cr was found to be 3-15 ppm and Ni 1-13 ppm. The Co-, Cr- and Ni-total contents are lower in topsoils than in subsoils. However, the EDTA-extractable portion of them is higher in topsoils than in subsoils. Most readily extractable is Ni. 3.2. COPPER Cu concentration is also higher in soil on serptentinite (33-66 ppm) than on granite and gneiss (3-22 ppm). In soil on serpentinite, the Cu content increases from topsoil to parent rock, while in soil on gneiss and granite it decreases from the topsoil downwards. Also here, the EDTA-extractable portion of Cu is higher in topsoil than in subsoil. 3.3. LEAD The total content of Pb in topsoils is high in all the soils under consideration (122268 ppm), decreasing rapidly towards the subsoil to a few ppm or below detection limit. This big difference between topsoil and subsoil suggests Pb contamination of these forest soils. The EDTA-extractable level of Pb is very high (50--80%), suggesting that Pb is bound in an organically complex form. This phenomenon is well known in forest soils from both the Czech Republic (Lochman, 1983, 1986) as well as from abroad (Heinrichs and Mayer, 1977; Hutchinson and Whitby, 1974). 3.4. ZINC The total content of Zn in the soils under consideration varies from 18 to 62 ppm. There are no significant differences in Zn content between the soils from each of the investigated parent rocks (serpentinite, gneiss, granite). The quantities are smaller than the world-wide content of 60 ppm Zn in soils, reported by Ure and
MOBILITY OF HEAVY METALS IN SOILS cm 0
165
2;.& ~
/ 20
";"
4O
60
.80
100 . . . . . . . . . . . . . . . . ,k. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 5 10 15 20 25 30 35 40 45 50 55 60 65 7 0 p p m I • i
TOTAL
~
EDTA
÷
HAC
I
Fig. 1. Total content and EDTA- and HAc-extractable portion of zinc in profile of podzolic soil developed on granite, Slavkovsk2~ Les mountains, Czech Republic.
B errow (1982) and Kabata-Pendias and Pendias (1984). In contrast to other studied elements, Zn was found in all samples in EDTA-, HAc- and water-extractable form. It is worth mentioning that the HAc-extractable portion is equal to or higher than an EDTA-extractable one. Cross ratio of extractable portions is given in Figure 1. It is obvious that the distribution of Zn in the soil profile depends on soil type and soil horizon. There is a decrease of Zn in eluvial soils and accumulation at the illuvial horizon in podzol soils.
4. Conclusion
Soils under consideration in the Krugn6 hory and Slavkovskj¢ Les mountains are evidently contaminated by Pb. The total content of this element in topsoil is always above 200 ppm, while in subsoils it decreases to about 20-60 ppm and, in parent material, it is sometimes below the limit of detection. This phenomenom indicates deposition from air pollution. The EDTA-extractable portion of Pb in topsoil is 50-90% of its total content. The concentration of Co, Ni and Cr depends on the parent rock, their concentrations being higher in soils on serpentinite then that on gneiss and granite. Approximately the same concentration of Zn was found in soil on serpentinite, gneiss and granite. Zn was easily extracted and its distribution in the soil profile depends on the soil-forming process. From the risk assessment point of view, the extractable portion of heavy metals is much higher in topsoils than in subsoils. In some cases the concentration of some elements exceeds the corresponding limit, it is thus necessary to find out the mobility of the element using appropriate extraction methods.
166
BOHUMILABEZVODOVA
References Berrow, M.L. and Ure, A.M.: 1985, 'Trace Element Distribution and Mobilization in Scottisch Soils with Particular Reference to Cobalt, Copper and Molybdenum', Environmental Geochemistry and Health 8, 19-24. Bruemmer, G.W., Gerth J., and Herms, U.: 1986, 'Heavy Metal Species, Mobility and Availability in Soils', Z. Pflanzenernaehr. Bodenk. 149, 382-398. Heinrichs, H. and Mayer, R.: 1977, Distribution and Cycling of Major and Trace, Elements in Two Central European Forest Ecosystems', J. Environ. Qual. 6, 402--407. Hutchnson, T.C. and Whitby, L.M.: 1974, 'A Study of Airborne Contamination of Vegetation and Soils by Heavy Metals, from the Sudbury, Ontario, Copper-nickel Smelters', Symposium Trace Substances in Environmental Health, VII., University of Missouri, Columbia, pp. 175-178. Kabata-Pendias, A., and Pendias, H.: 1984, Trace Elements in Soils and Plants, CRC Press, Florida. Lochman, V.: 1983, 'Dynamika a z~isoba n~kter,jch t~k~ck kovu_ a hlin~u v pud~ich smrkov~ch porost_u v oblastech rozdflnrho stupn~ zne~i~t~nl ovzdu~f', Lesnictvi 29(8), 659-672. Lochman, V.: 1986, 'Sou~asn~)v~jvojlesnfch pud v Kru~n~ch hor~ich', Prdce VULHM 68, 9--48. Ure, A.M. and Berrow, M.L.: 1982, Environmental Chemistry, Royal Society of Chemistry, London.
I
THE MOBILITY OF HEAVY METALS IN SOILS IN THE KRUSNE
HORY AND SLAVKOVSKY LES MOUNTAINS BOHUMILA BEZVODOVA Czech Ecological Institute, Prague, Czech Republic
Abstract. In the North Bohemian forest soils the total content and EDTA, HAc and H20-extractable portions of Cr, Co, Ni, Cu, Pb and Zn were investigated. Increased concentration of Pb in topsoils, in comparison with subsoils, is the result of air pollution. The extractable portion of all studied heavy metals is higher in topsoil than in subsoil.
1. Introduction Many heavy metals are biogene elements, i.e. they occur in limited amounts in living organisms and play specific roles in them. However, higher concentrations can cause complications. In recent years, due to human activity, some heavy metals accumulate in topsoil, penetrate into the food chain and affect human health. There are two ways that heavy metals can move from soils into the food chain: soilplant, and soil-drinking water. Both pathways dePend upon the transfer of heavy metals from solid components to the soil solution. The reactions involved are Very complex, with the rate of transfer depending on many factors, mainly on the binding mechanisms of heavy metals in soil solids, and on the amount and composition of the liquid phase (Bruemmer et al., 1986). In the literature it is possible to find many papers on this topic, often with controversial results. For practical purposes, acceptable limits for heavy metals in soils were introduced. These limits change from c~untry and/or extractable amounts. The advantage of total content of heavy metal in soil is the comparability of the determined values all over the world. The advantage of determining extractable soil metal is that information is obtained about the mobility and availability of the metals. However, the disadvantage of the latter approach is the dependence on extraction methodology.
2. Area of Interest and Methods Used Soils in the Kru~n6 Hory and Slavkovsk)~ Les mountains were used for this study. Both mountain areas are situated on the N and NW boundary of the Czech Republic at an altitude of about 700 m. Both areas are covered by damaged, in some places dead, forest. In the Slavkovsk~ Les mountains the parent rock is mainly granite, on which the brown podzolic soils are developed. One locality is formed of serpentinite with pararendzina on it. In the Km~n6 Hory mountains, brown soils cover weathered gneisses. For the purpose of this investigation 9 test pits were dug (6 in Kru~n6 Environmental Monitoring and Assessment 34:163-166, 1995. (~) 1995 Kluwer Academic Publishers. Printed in the Netherlands.
164
BOHUMILABEZVODOV./~
Hory mountains and 3 in Slavkovsk3) Les mountains). Each locality was sampled in accordance with the soil horizons to follow the heavy metals distribution in the whole soil profile. Laboratory analyses were made on the grain size fraction of less than 2 mm. The total contents were determined by X-ray fluorescence (XRF). The extractable content was received using 0.05 M EDTA (ethylene diamine tetraacetic acid), HAc (acetic acid) according Berrow and Ure (1985), and distilled water (5 g/100 ml, shake 1 h, leaching 24 hs). The concentrations were determined using atomic absorption spectrometry (AAS). 3. Results
3.1. CHROMIUM,COBALTAND NICKEL The concentration of these elements is evidently determined primarily by the parent rock composition. Co was found only in pararendzine on serpentinite (total content, 5-40 ppm). Cr and Ni contents are considerable higher in the pararendzine on serpentinite (total Cr content, 145-405 ppm, total Ni content, 186-490 ppm) than in other soils, where the total concentration of Cr was found to be 3-15 ppm and Ni 1-13 ppm. The Co-, Cr- and Ni-total contents are lower in topsoils than in subsoils. However, the EDTA-extractable portion of them is higher in topsoils than in subsoils. Most readily extractable is Ni. 3.2. COPPER Cu concentration is also higher in soil on serptentinite (33-66 ppm) than on granite and gneiss (3-22 ppm). In soil on serpentinite, the Cu content increases from topsoil to parent rock, while in soil on gneiss and granite it decreases from the topsoil downwards. Also here, the EDTA-extractable portion of Cu is higher in topsoil than in subsoil. 3.3. LEAD The total content of Pb in topsoils is high in all the soils under consideration (122268 ppm), decreasing rapidly towards the subsoil to a few ppm or below detection limit. This big difference between topsoil and subsoil suggests Pb contamination of these forest soils. The EDTA-extractable level of Pb is very high (50--80%), suggesting that Pb is bound in an organically complex form. This phenomenon is well known in forest soils from both the Czech Republic (Lochman, 1983, 1986) as well as from abroad (Heinrichs and Mayer, 1977; Hutchinson and Whitby, 1974). 3.4. ZINC The total content of Zn in the soils under consideration varies from 18 to 62 ppm. There are no significant differences in Zn content between the soils from each of the investigated parent rocks (serpentinite, gneiss, granite). The quantities are smaller than the world-wide content of 60 ppm Zn in soils, reported by Ure and
MOBILITY OF HEAVY METALS IN SOILS cm 0
165
2;.& ~
/ 20
";"
4O
60
.80
100 . . . . . . . . . . . . . . . . ,k. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 5 10 15 20 25 30 35 40 45 50 55 60 65 7 0 p p m I • i
TOTAL
~
EDTA
÷
HAC
I
Fig. 1. Total content and EDTA- and HAc-extractable portion of zinc in profile of podzolic soil developed on granite, Slavkovsk2~ Les mountains, Czech Republic.
B errow (1982) and Kabata-Pendias and Pendias (1984). In contrast to other studied elements, Zn was found in all samples in EDTA-, HAc- and water-extractable form. It is worth mentioning that the HAc-extractable portion is equal to or higher than an EDTA-extractable one. Cross ratio of extractable portions is given in Figure 1. It is obvious that the distribution of Zn in the soil profile depends on soil type and soil horizon. There is a decrease of Zn in eluvial soils and accumulation at the illuvial horizon in podzol soils.
4. Conclusion
Soils under consideration in the Krugn6 hory and Slavkovskj¢ Les mountains are evidently contaminated by Pb. The total content of this element in topsoil is always above 200 ppm, while in subsoils it decreases to about 20-60 ppm and, in parent material, it is sometimes below the limit of detection. This phenomenom indicates deposition from air pollution. The EDTA-extractable portion of Pb in topsoil is 50-90% of its total content. The concentration of Co, Ni and Cr depends on the parent rock, their concentrations being higher in soils on serpentinite then that on gneiss and granite. Approximately the same concentration of Zn was found in soil on serpentinite, gneiss and granite. Zn was easily extracted and its distribution in the soil profile depends on the soil-forming process. From the risk assessment point of view, the extractable portion of heavy metals is much higher in topsoils than in subsoils. In some cases the concentration of some elements exceeds the corresponding limit, it is thus necessary to find out the mobility of the element using appropriate extraction methods.
166
BOHUMILABEZVODOVA
References Berrow, M.L. and Ure, A.M.: 1985, 'Trace Element Distribution and Mobilization in Scottisch Soils with Particular Reference to Cobalt, Copper and Molybdenum', Environmental Geochemistry and Health 8, 19-24. Bruemmer, G.W., Gerth J., and Herms, U.: 1986, 'Heavy Metal Species, Mobility and Availability in Soils', Z. Pflanzenernaehr. Bodenk. 149, 382-398. Heinrichs, H. and Mayer, R.: 1977, Distribution and Cycling of Major and Trace, Elements in Two Central European Forest Ecosystems', J. Environ. Qual. 6, 402--407. Hutchnson, T.C. and Whitby, L.M.: 1974, 'A Study of Airborne Contamination of Vegetation and Soils by Heavy Metals, from the Sudbury, Ontario, Copper-nickel Smelters', Symposium Trace Substances in Environmental Health, VII., University of Missouri, Columbia, pp. 175-178. Kabata-Pendias, A., and Pendias, H.: 1984, Trace Elements in Soils and Plants, CRC Press, Florida. Lochman, V.: 1983, 'Dynamika a z~isoba n~kter,jch t~k~ck kovu_ a hlin~u v pud~ich smrkov~ch porost_u v oblastech rozdflnrho stupn~ zne~i~t~nl ovzdu~f', Lesnictvi 29(8), 659-672. Lochman, V.: 1986, 'Sou~asn~)v~jvojlesnfch pud v Kru~n~ch hor~ich', Prdce VULHM 68, 9--48. Ure, A.M. and Berrow, M.L.: 1982, Environmental Chemistry, Royal Society of Chemistry, London.
