HEAVY METALS CONTENT IN INITIAL SOIL FORMED UNDER SUCCESSION COMMUNITIES ON SAND MINE QUARRY

Marcin Pietrzykowski, Wojciech Krzaklewski
Department of Forest Ecology, University of Agriculture in Cracow, Poland

ABSTRACT

Sand excavations of Jaworzno-Szczakowa region (Upper Silesia Region, Poland) are reclaimed mainly for the forestry but some parts of sand excavations were left for succession. The forming soils are under intense anthropopression, which is manifested by higher imission of heavy metal. Studies of initial soils were carried between 1985 and 2002 in areas with chronosequence, showing subsequent stages of vascular plans succession. A comparison of the study results from the 1985 showed a clear relation between heavy metal content (Zn, Pb, Cd) in the topsoil layers, soil age and succession stage. The results from areas carried out later did not show such a clear correlation.

Key words: sand excavation, succession, initial soil, heavy metal.

INTRODUCTION

The "Szczakowa" mine excavation is located in the vicinity of big urban and industrial centres of the Upper Silesia and Kraków Industrial Zone. However, in this part of Europe, emission and deposition of lead and cadmium to coniferous forest in the nineties was as follows: above 8.0 kg · km^-2·yr^-1 Pb, and 500 g·km^-2·yr^-1 Cd [3], these specific areas are unique on the European scale as far as the high level of soil contamination with lead and cadmium is concerned.

The reclaimed areas of the "Szczakowa" mine excavation have been affected by dust and gas contamination particularly visible between the 1960 and 1980's [data from the Voivodeship Sanitary and Epidemiological Site in Katowice, Fig. 1]. At the time the type and the size of emission had a significant influence on soil substrate pH changes in the floor of the sand mine. Not at all infrequent were dramatic changes of pH_H2O from 3.6 to 4.5, and at times even to 9.4 [1]. It was extremely unfavourable for woodland crops introduced as part of the reclaim process. The "Szczakowa" sand mine excavation site has been under a planned reclaim scheme. Measures taken under the reclaim scheme, including the dosage of mineral fertilizers and humus, have changed over the years along with the state of the knowledge in the field, therefore the direct impact of emission on heavy metal concentration in the reconstructed soils in the area may difficult to assess. However, some parts of the excavation were not reclaimed due to changes in plans of the mined areas and their temporary exclusion from mining, particularly in the 1970's and 1980's. Such areas underwent the process of primary succession and the formation of initial soils took place with no human intervention. This is why it is possible to compare the impact of industrial emission on the heavy metal content in initial soils of sand excavations under communities from succession based on results from 1985 and 2002.

It is difficult to propose, especially for forest ecosystem, with our present knowledge a limit for a toxic concentration of Zn Cu, Cd and Pb [2], however on the basis of many years of research on the destructive influence of heavy metals on the forests, the following threshold concentration of the accumulation in the layers of organic soils of fresh forest sites for the industrial regions of  Southern Poland has been established: cadmium (Cd) – 50 mg·kg^-1, copper (Cu) – 150 mg·kg^-1, zinc (Zn) 500 mg·kg^-1, lead (Pb) 1500 mg·kg^-1 [23]. Critical loads of lead and cadmium (5^th percentile) for forest soils in this part of Europe, computed from an European database, is on the level 15 to 25 g·km^-2·yr^-1 Pb and 2 to 3 g·km^-2·yr^-1 Cd [17]. It should be stressed, however, that the range of negative results of pollutant interaction is determined not only by a total concentration but also by their mutual relations. There is no completely unambiguous method of determining the biologically available fraction of the metals in the soil [2].

What is very important in case of the post-mining regions is that these processes take place in entirely new conditions from the point of view of the climate, geographic features, bare rock which is the substrate for soils forming under communities from primary succession and industrial emissions [14,20].

MATERIAL AND METHODS

Object of study
The study sites were situated on The Szczakowa Sand Pit works near Jaworzno in southern Poland (19°26' E; 50°16' N) within the Przemsza River basin. In terms of tectonics, the area belongs to the Bytom Basin [6]. The deposits are genetically related to the fluvioglacial Quaternary sediments deposited in a pre-Quaternary morphological depression. The sedimentation of deposits filling the Biała Przemsza River valley occurred during the Middle Poland and Wörm glaciations period and its approximate age can be defined to reach between 80 and 240 thousand yrs [12]. In general, its climate can be characterized by an annual average air temperature of 8°C and an annual average precipitation of 700 mm. Sand was mined from an open pit. Following the end of the exploitation, the surface lowered considerably in the opencast working boundaries (from 5 to 25 m). The open cast area (over 2700 ha) was mostly reclaimed by reforestation with pine-stands.

Towards the end of the 1970's and in the 1980's dust fallout in the area of the "Szczakowa" Sand Mine much exceeded 200 g·m^-2·yr^-1. Average annual SO₂ concentration in this period reached 68 µg·m^-3. At the beginning of the 1990's there was a marked fall in the size of industrial emission, and there was a nearly twofold decrease in the dust fallout, however, it still exceeded 100 g·m^-2·yr^-1. Only from mid 1990's to 2001 a gradual decrease of industrial emission was reported, with dust fallout falling to approx. 25 g·m^-2·yr^-1 (Fig. 1). There was also a marked downward trend in heavy metal deposition. Still at the beginning of the 1990's the emission of lead (Pb) was from 0.044 to 0.125 g·m^-2·yr^-1, zinc (Zn) from 0.212 to 7.089 g·m^-2·yr^-1, and cadmium (Cd) from 0.0026 to 0.0039 g·m^-2·yr^-1. In the mid 1990's deposition of heavy metals significantly decreased and in 2001 in the case of lead it was slightly above 0.01 g·m^-2·yr^-1, in the case of zinc, slightly above 0.10 g·m^-2·yr^-1, and cadmium below 0.0007 g·m^-2·yr^-1 [based on data from the Voivodeship Sanitary and Epidemiological Site in Katowice].

Field studies
Study sites in 1985 were located in a belt behind the mined area, and included stages of primary succession formed between 1975 and 1986. They were vascular herbaceous plant communities, from a stage with a prevalence of Corispermum leptopterum (1 year after mining was terminated), then a community with Corynephorus canescens (5 years after mining was terminated), a community of Koeleria gracilis and Myricaria germanica (9 years) followed by a community of Calamagrostis epigejos (11 years after mining was terminated) [Krzaklewski, not published data, personal communication]. In 2002 new study sites were formed under communities from succession on parts of post-mining excavations abandoned between 1977 and 1997. The youngest fragments exhibited communities of Corynephorus canescens (5 years after mining was terminated), then arborescent communities of biogroup composition and prevalence of Pinus sylvestris and a fraction of Populus tremulae (17 years after mining was terminated) and communities with a prevalence of Pinus sylvestris and presence of Betula pendula (22 and 25 years after mining was terminated) [16]. Three study sites were organised under communities from succession in each age group.

Sampling and laboratory analyzes
Soils samples were taken from 6 points located in a grid of squares of 6×6 m in every study site with the use of a soil auger from 0-5 cm (i.e. organic-mineral initial horizons) and 5–10 cm (i.e. from transitional organic-mineral initial horizons with parent rock features) and mixed samples were prepared.

The following data was determined on the collected and dried soil samples in the laboratory: grain composition with aerometrical method, pH potentiometrically in H₂O and in 1M KCl in a solution of 1:2,5; basic exchangeable cations Na(+), K(+), Ca(2+), Mg(2+) in 1 M NH₄Ac by AAS detection [19]; organic carbon (C_org) content with the method of infrared absorption with an analyzer 'Leco CNS 2000', the content (close to the total) of some metallic elements: Zn, Cu, Pb, Cd, after digestion in the mixture of HNO₃, (d=1.40) and 60% HClO₄ acid in 4:1 proportion using the AAS method [13].

RESULTS AND DISCUSSION

The investigated soils from the fragments of the excavations were classified as Haplic Arenosols and Urbic Anthrosols according to the FAO classification [4,16]. The initial organic-mineral horizons were characterised by graining of sands with a silt sized fraction from 1 to 17% and a clay fraction from 1 to 5%. In deeper horizons with parent rock features, clay interbedding of a few to about a dozen cm deep with a silt fraction from 20 to 32 % and a clay fraction from 7 to 9 % was sometimes found. Initial soils with top mineral horizons made of sand deposits generally exhibited the sum of alkali cations from under 1.0 to 7.4 cmol (+)·kg^-1 soil. In the soil sorption complex Ca (+2) prevailed, with contents of 0.34 to 1.8 cmol(+)·kg^-1 soil and no increase in the content of this cation was found in relation to soil age and succession stages.

The pH content of samples from the top horizons under communities from succession taken in 1985 were from 7.2 to 8.7 pH_H2O and from 7.1 to 8.6 pH_KCl and were more than 3 units higher than in 2002, when they were respectively from 5.1 to 5.6 pH_H2O and from 4.1 to 5.4 pH_KCl. Samples dating from 1985 exhibited a marked upward pH trend, or even alkalisation of top horizons in comparison to initial features of substrates uncovered during mining (the pH_H2O of comparative samples of sands and clay was from 6.7 to 6.8 and pH_KCl 5.7 to 6.1. Other studies conducted at the end of the 1980's in the "Szczakowa" mine excavation also reported a higher pH in case of initial soils in reclaimed areas i.e. from 7.0 to 8.2 pH_H2O and from 6.3 to 7.4 pH_KCl, however, a downward pH trend was found with the growing depth of soil profiles [17]. At that time increased pH and alkalisation of the topsoil horizons was due to industrial emissions in the "Szczakowa" sand mine excavation, particularly from the nearby cement plant [1]. In 2002 the pH of the top horizons was already strongly acidic to acidic. This was connected with falling industrial emission (Fig. 1) and the acidifying impact of organic deposit under the developing plant communities [15]. Apart from graining and organic matter content, also the soil pH affects the heavy metal mobility and availability for plants [9]. And so heavy metal mobility may increase in the studied soils with falling pH, particularly zinc and cadmium.

In 1985 the studied soils under communities from succession showed a growing heavy metal content in chronosequence. It was particularly visible in case of zinc (Zn) content, which in the 0-5 cm horizon under the initial stage with a prevalence of Corispermum leptopterum within 1 year of finishing mining was only 12 mg·kg^-1 soil, and 11 years after the termination of mining it increased to 423 mg·kg^-1 soil (Table 1) under the stage with a prevalence of Calamagrostis epigejos. The increase of zinc concentration was clearly related to the size of the emission and dust fallout in the area of the excavation. Dust settled on the plants finally to reach the soil together with precipitation and atrophied parts of ground cover [23]. After reaching the soil, heavy metals were mainly accumulated in the upper, organic and organic-mineral soil layers [7,8,21]. In comparative samples of sands uncovered due to mining, the zinc (Zn) content was on average 16.0 mg·kg^-1, and in clays 50 mg·kg^-1. According to the IUNiG classification criteria developed for agricultural land [10] areas of initial stage in 1985 were ranked as 0 (Zn content regarded as natural), and in successive stages it was ranked as II (signifying mild zinc pollution).

In case of soils in areas studied in 2002 there was no such marked zinc content increase in chronosequence as in the case of areas from 1985 (Table 1). Zinc content in the initial organic-mineral horizons of soils under communities from succession (in the layer of 0-5 cm) studied in 2002 was from 12.3 mg·kg^-1 soil under the initial stage with Corynephorus canescens to 89.7 mg·kg^-1 soil in the oldest areas with arborescent communities and prevalence of Pinus sylvestris and Betula pendula (Table 1). Soils investigated in 2002 may be considered as soils with natural zinc content or slightly increased zinc content [10].

In samples taken in 1985 there was a marked upward trend of lead (Pb) and cadmium (Cd) concentration in chronosequence. In the first year after mining was terminated, the Pb content in the top horizon of initial soils was approx. 6 mg·kg^-1 soil and cadmium 1 mg·kg^-1 soil. In the 11-year-old areas, the Pb content increased to 260 mg·kg^-1 soil, and Cd to mg·kg^-1 soil (Table 1). Lead and cadmium concentration in the initial soils was also clearly linked to the size of dust depositions in the excavation area (Fig. 1). Comparable Pb content in sands uncovered in the process of mining was from 7 to 8 mg·kg^-1 soil and in clay deposits it was twofold higher. In case of cadmium, content considered background in sand deposits was from approx. 0.1 mg·kg^-1 to trace quantities in clay deposits (Table 1). Although in the studied area there is a naturally higher heavy metal content in parent rock [5], from the point of view of lead and cadmium soil contamination there was a steady increase in 1985 in chronosequence from 0 for lead (Pb content considered natural) and I for cadmium (increased Cd content) to III for lead (soils moderately polluted with Pb) and IV for cadmium (soils heavily polluted with Cd) [10]. In the first year after mining was terminated, the cadmium content was approx. 10 fold higher than initial values, and after 11 years, it was sometimes even several dozen times higher. Out of the heavy metal group, cadmium is one of the most mobile elements in the soil environment [9]. Its toxicity, particularly for soil microorganisms, is much higher compared to zinc or lead and therefore it has a very negative influence on the efficient functioning of the materialisation process of organic substance and the nutrient circulation in the forest ecosystem [22,23]. The reported cadmium, lead and zinc concentrations were however in no case higher than the quoted critical values for forest soils of coniferous forest habitats in the Upper Silesia Industrial Zone [23]. For instance, in the nearby Olkusz area affected by the zinc and lead ore mining and production industry, the cadmium content in the locally degraded forest soils in areas adjacent to industrial sites, may sometimes exceed 50 mg·kg^-1 soil [11]. However, considering the young age of soils forming in the excavation site it may be assumed that the heavy metal concentrated rate reported in 1985 was very high. In 2002 lead concentration increased in chronosequence from 8.4 mg·kg^-1 soil in the youngest areas with communities with Corynephorus canescens to over 43 mg·kg^-1 soil under herbaceous communities with Pinus sylvestris and Betula pendula. This was content typical of natural soils [10]. In 2002 cadmium content in the topsoil horizons was on average slightly diversified and not much higher than the content considered natural.

In 17, 22 and 25 year-old areas studied in 2002 primary succession and the soil-forming process under communities began at a similar period as in the case of 1, 5, 9 and 11 year-old areas studied 1985, i.e. at the end of the 1970's and in the 1980's when the size of industrial emissions in this area was very high. However, the heavy metal (Zn, Cd, Pb) concentration assessed in 2002 showed that soil contamination was not long-term. This was connected with the features of initial soils including mostly low organic matter content, graining and features of the soil sorption complex.

CONCLUSIONS

The conducted studies enabled observations of changes and the comparison of the industrial emission impact on the heavy metal content in initial soils forming under communities from succession in the sand fluvioglacial deposits uncovered in the mining process in two periods i.e. 1985 and 2002. The reported concentration and zinc, cadmium and lead accumulation rates in the investigated soils of the excavation area in 1985 was much higher than in 2002. The differences were most visible in case of growing zinc (Zn) concentration rate (a 35-fold increase within 11 years) and cadmium (Cd) (a 7-fold increase within the same period). Diversified heavy metal concentration in comparable periods (1985 and 2002) was clearly due to changes in the emissions of dust containing these metals. Considering the young age of the soils it could be said that the heavy metal concentrations reported in 1980 were high and could negatively influence the reconstructed soil environment and vegetation in the excavation area. However, in the case of the reconstructed forest ecosystem it is difficult to establish unambiguously the range of heavy metal content in soil harmful for plants and evaluate the extent of the impact of the reported contamination on soil forming process. In the post-mining areas these processes take place in completely new conditions with respect to the climate, geographic features, and bare rock which is the substrate for initial soils under communities form primary succession and industrial emission. In line with the state of knowledge in this field the studied initial soils showing an overall low alkaline cation content with a prevalence of the sand fraction in the granulometric composition, may be regarded as sensitive to degradation caused by industrial emission. In turn the still low organic matter content and the capacity of the soil sorption complex mean that the heavy metal concentration is not long-term as demonstrated by areas studied in 2002. The conducted studies unanimously confirm that the overall decrease of industrial emission in the areas of the "Szczakowa" sand mine excavation (the Upper Silesia Industrial Zone) is reflected in the lower heavy metal accumulation in initial soils in sand mine excavation as compared to the 1970's and the1980's.

REFERENCES

1. Adamowicz S., 1965. Dobór roślin dla leśnej rekultywacji wyrobisk górnictwa piasku podsadzkowego [Plant selection for reclamation to forest of sand mine quarries]. Zakład Badań Naukowych GOP-PAN, Biuletyn, 5, 83–88 [in Polish].

2. Balsberg-Phålsson A-M., 1989. Toxicity of heavy metals (Zn, Cu, Cd, Pb) to vascular plants, Water Air and soil Pollution, 47, 287–319.

3. Dutchak S., Ilyin I., 2002. Modelling Depostition fields of lead and cadmium for critical load exceedance estimates, in: Posch M., P.A.M. de Smet, J-P. Hettelingh and R.J. Downing (eds.) Modelling and mapping of critical thresholds in Europe,  Status report 2002 CCE, 51–64.

4. FAO-UNESCO, 1988. Soil Map of the World. Revised Legend, Food and Agriculture Organization of the United Nations, Roma.

5. Gambuś F., Gorlach E., 2001. Ocena i stan zanieczyszczenia gleb  w Polsce [The assesment and contamination state of soil in Poland]. Aura. 7, 10–11 [in Polish].

6. Gilewska S., 1972. Wyżyny Śląsko-Małopolskie [Śląsko-Krakowskie Upplands], in M. Klimaszewskiego (ed)., Geomorfologia Polski, Polska Południowa Góry i Wyżyny cz. I. [Geomorphology of Poland, Southern Poland, Mountains and Upplands, Part I]. Warszawa, PWN. 232–339 [in Polish].

7. Godbold D.L., Hüttermann A., 1985. Effect of Zinc, Cadmium and Mercury on root elongation of Picea abies (Karst.) seedlings, and the significance of these metals to forest Die-Back, Environmental Pollution, 38, 375–381.

8. Greszta J., Godzik S., 1969. Wpływ hutnictwa cynku na gleby [The Influence of Zink mining on soil]. Soil Science Annual. 20, 195–213 [in Polish].

9. Kabata-Pendias A., Pendias H., 1992. Trace elements in soil and plants, 2nd edition, CRC Press, Boca Raton, London, 124–350.

10. Kabata-Pendias A., Piotrowska M., Witek T., 1993. Ocena jakości i możliwości rolniczego użytkowania gleb zanieczyszczonych metalami ciężkimi, in Ocena Stopnia Zanieczyszczenia Gleb i Roślin [An assessment of quality and possibilities of agricultural using of soil contaminated by heavy metals, in: An assesment of soil and plant contamination degree]. IUNG, Pulawy, 5–10.

11. Krzaklewski W., Barszcz J., Małek S., Kozioł K., Pietrzykowski M., 2004. Contamination of Forest Soils in the Vicinity of the Sedimentation Pond after Zinc and Lead Ore Flotation (in the Region of Olkusz, Southern Poland), Water, Air, and Soil Pollution, 159 (1), 151–164.

12. Lewandowski J., Zieliński T., 1990. Wiek i geneza osadów kopalnej doliny Białej Przemszy [Age and Genesis of Biała Przemsza River buried Valley sediments]. Biuletyn Państwowego Instytutu Geologicznego, 364, 64–98, [in Polish].

13. Ostrowska A., S. Gawliński, Szczubiałka Z., 1991. Metody analizy gleb i roślin [Procedures for soil and plants analysis]. IUNG, Warszawa, 240 [in Polish].

14. Pająk M., Forgiel M., Krzaklewski W., 2004. Growth of trees used in reforestation of a northern slope of the external spoil bank of the "Bełchatów" brown coal mine, EJPAU 7(2). Available Online: http://www.ejpau.media.pl/volume7/issue2/forestry/art-02.html

15. Pietrzykowski M., Krzaklewski W., 2004. The accumulation of organic matter, Carbon and Nitrogen during the development of initial soil on the non-reclaimed parts of sand exploitation area, Science Books of University of Zielona Góra, Environment Engineering, 131(12), 307–317 [in Polish].

16. Pietrzykowski M., 2004. Characteristic of soils and vegetation in reclaimed areas or in areas left for succession on the example of the Szczakowa sand mine cast, Ph.D. Thesis, Department of Forest Ecology, Agricultural University of Krakow, 148 [in Polish].

17. Pikulski A., 1989. Ocena hodowlana zalesień wyrobiska piasku podsadzkowego w Szczakowej (Pole I) [An silviculture assessment of afforestation on sand filling quarry Szczakowa, Field I]. Ph.D. Thesis, Department of Silviculture, Agricultural University of Krakow, 156 [in Polish].

18. Reinds G.J., de Vries W., Groenenberg E.J., 2002. Update assessment of critical loads of lead and cadmium for European forest soils' in: Posch M., P.A.M. de Smet, J-P. Hettelingh and R.J. Downing (eds.) 'Modeling and mapping of critical thresholds in Europe', Status report 2002 CCE, 123–127.

19. Van Reeuwijk L.P., 1995. Procedures for Soil Analysis, 5th ed., Technical Paper 9, ISRIC, FAO, Wageningen.

20. Wali MK., 1999. Ecological succession and the rehabilitation of disturbed terrestrial ecosystems, Plant and Soil, 213, 195–220.

21. Widera S., 1980. Skażenie gleb i organów asymilacyjnych sosny pospolitej w różnych odległościach od zródła emisji, Archiwum Ochrony Środowiska [Contamination of the Soil and Assimilative Organs of the Pine-Tree in Various Distance from the Surface of Emission]. Archives of Environmental Protection, 3–4, 147–152 [in Polish].

22. Zwoliński J., Olszowska G., Zwolińska B., 1987. Soil biological activity as an indicator of industrial pressure on the forest environment (microbiological and biochemical activity), Acta Agraria et Silvestria Vol XXVI, 25–43.

23. Zwoliński J., 1995. Wpływ emisji zakładów przemysłu metali nieżelaznych na środowisko leśne – rola metali ciężkich w degradacji lasów [Effects of emissions from non-ferrous metal works on forest environment – the role of heavy metals in forest degradation]. Prace Instytutu Badawczego Leśnictwa, ser. A, 809, 1–86 [in Polish].

Accepted for print: 25.11.2010

Responses to this article, comments are invited and should be submitted within three months of the publication of the article. If accepted for publication, they will be published in the chapter headed 'Discussions' and hyperlinked to the article.