SZILI-KOVÁCS Tibor (1), GULYÁS Ferenc (1), ANTON Attila (1), FILIP Zdenek (2)

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1 Scientific registration n o : 2328 Symposium n o : 37 Presentation : poster An international approach to assess soil quality by biological methods: Experience from anthropogenically affected soils in Hungary Une approche internationale pour évaluer la qualité des sols par des méthodes biologiques. Le cas d'un sol anthropisé en Hongrie SZILI-KOVÁCS Tibor (1), GULYÁS Ferenc (1), ANTON Attila (1), FILIP Zdenek (2) (1) Research Institute for Soil Science and Agricultural Chemistry of the Hungarian Academy of Sciences, Budapest, Herman O. u. 15. H-122 Hungary (2) Federal Environmental Agency, Institute for Water, Soil and Air Hygiene, D Langen, Paul-Ehrlich-Str. 29, FRG. ABSTRACT Indication value of microbial biomass was studied in case of two anthropogenically contaminated soils by power plants at Visonta and Százhalombatta. The seasonal changes of microbial biomass-c and the formation of biomass during a 3 days incubation with lucerne meal were studied. Soil were sampled from five locations at seven times from spring 1995 to spring 1996 year. Although the dust deposition rate was not high in the above regions some accumulation of inorganic and organic pollutants could be observed. The results of our investigations showed strong differences in microbial biomass during the season which is probably in relation to the nutrient state of soil rather than to soil moisture and temperature. Carbon incorporation rates were also changed during the year in spite of the equal incubation circumstances. The low level of pollution did not caused significant change in microbial biomass-c. INTRODUCTION Soil quality can be deteriorated by various anthropogenic chemical pollutants. Especially the accumulation of xenobiotics may endanger soil biota, soil transformation processes and a quality of plant product. Air deposition of pollutants from industrial sources may seem negligible but some refractory or persistent materials can be accumulated at significant amounts in the topsoil for a long time. For this reason it is necessary not only to measure the concentration of harmful materials but also to estimate the level significant for changes which can affect the main ecological functions of soil (Filip,1995). Microbial biomass is a general parameter of soil microbiota and this point of view may 1

2 gain an indicative importance (Brookes, 1995). The size of microbial biomass is considerably influenced by environmental factors (soil moisture, temperature, nutrients) and responds very rapidly to their changes. The formation of biomass can be also important indication value for the ability of microorganisms to form new biomass from the abiotic organic matter. Indication value of microbial biomass was studied in case of two anthropogenically polluted soils contaminated by air depositions from power plants and compared with control sites. The seasonal changes in biomass were also considered. MATERIALS AND METHODS Five sampling sites, all arable land, were selected near to two power stations. Two of them are situating on the foot of Mátra mountain closed to "Mátraalja" Power Plant (Visonta) which is situated in the North-East Hungary about 8 km from Budapest. The contaminated site is very closed to the power station at the village area. The control site is situated at village. Chernozem brown forest soil (acidic) is typical for both sites. Only the cadmium concentration was significantly higher in soil in comparison with soil (Table 2.). The other three sampling sites were located near to "Dunamenti" Power Plant (Százhalombatta) south from Budapest. Soils at two contaminated sites ( and ) were located near to the Százhalombatta Power Plant which caused a low pollution resulting in a not significant heavy metal accumulation in the soil. The control at village area, belongs to the calcareous chernozem type. Soils were sampled from the top 2 cm layer in 2 points along a line and then they were mixed. Three subsamples were divided from the original mixed soil sample. One was for moisture determination another was air dried for physical and chemical analyses and the remaining part was placed into a refrigerator for microbiological analyses. Soils were sampled seven times from March 1995 to April 1996 these were on 2nd March, 18th April, 6th June, 28th September, 7th November of 1995 year and 26th March, 22nd April of 1996 year. Microbial biomass-c was determined by chloroform fumigation extraction method using ethanol free chloroform (Williamson et al.,1995). Carbon content was determined in.5m potassium-sulphate extract by dichromate digestion and the non-reduced dichromate was back titrated with ferrous-ammonium-sulphate. Biomass-C was estimated according to Vance et al. (1987) calculations (k C =.38). A part of fresh soil samples were wet-sieved (5 mm mesh-size) and enriched with lucerne meal in.5 per cent. Soil samples have been incubated at 25 o C for 3 days. Microbial biomass-c was measured after lucerne meal addition and 3 days later. Lucerne meal contained 39.2 %C and 2.48 %N. 2

3 Table 1. Chemical characteristics of investigated soils. site ph (H 2 O) ph (KCl) CaCO 3 (%) C (%) N (%) NH + 4 -N mg/kg NO 3 -N mg/kg CEC meq/1 g Table 2. Total amounts of heavy metals in the investigated soils. site National limit * Element (ppm) As Hg Cr Zn Cd Pb Co Ni Cu * in case of soils having CEC between meq/1 g soil. RESULTS AND DISCUSSION Microbial biomass-c Microbial biomass-c data showed the following tendency during the sampling season (Fig.1.). The minimum value was found in June then it increased in October and November, the highest biomass-c was in March, however there was no sampling from middle of June to end of September and from middle of November to March. Decrease in microbial biomass-c during winter season usually occurs according to some observations (Kaiser and Heinemeyer, 1993). In the Visonta area the results showed that microbial biomass-c was higher in polluted site comparing with the unpolluted soil site in every sampling time. It is probably due to the higher organic matter content of soil (Table 1.) and not to be assigned to the heavy metal pollution. Besides this soil has very high cation exchange capacity which can adsorb metals in relatively high concentrations and preserve organic matter for longer time. 3

4 Microbial biomass-c (µg/ g soil) st 2nd 3th 4th 5th 6th 7th Fig.1. Microbial biomass-c changes during the season. A., Soil moisture (%) st 2nd 3th 4th 5th 6th 7th B., Soil temperature ( o C) st 2nd 3th 4th 5th 6th 7th Fig. 2. Soil moisture (A) and temperature (B) at the sampling dates (see M & M). 4

5 Microbial biomass-c (µg/g soil) th 4th 5th 6th 7th Fig. 3a. Net microbial biomass-c synthesized during 3 days due to lucerne meal addition. Microbial biomass-c (µg/g soil) th 4th 5th 6th 7th Fig. 3.b. Net microbial biomass-c synthesized during 3 days due to lucerne meal addition. In Százhalombatta region there was no significant differences in microbial biomass-c among the investigated three sites. The seasonal changes were similar to the Visonta region. There is not enough data to determine the factors affecting the fluctuations of microbial biomass during the year but probably the temperature, the vegetation and the 5

6 amount of plant residue after harvesting can play an important role. The effect of soil moisture could not be demonstrated because water content was relatively equal in all dates, rainy days preceded sampling amazingly in almost every case. Soil incubation experiment Microbial biomass-c increased during the 3 days incubation period in all soil sampling sites and at all times showing a significant incorporation of lucerne carbon to the microbial biomass. The lucerne meal added to the soil contained 196 mg C/kg soil and the carbon assimilation from this source estimated from 15 to 4 percent depending on the soil and the sampling date. The incorporation rates showed seasonal changes similar to the native microbial biomass-c. Plant residues and perhaps root exudates could be important in this respect. Interesting tendency was observed in Visonta region where the seasonal change of carbon incorporation from lucerne was higher in comparing with soil. Similarly but not at so high extent, the soil fluctuated more than and soil. CONCLUSIONS Soil microbial biomass and its formation in soil samples during a 3 days incubation has not decreased as a result of soil contamination by atmospheric depositions from a power plant. Rather a slight increase could be observed during a one year sampling period. Seasonal changes of microbial biomass-c were higher than the difference among the contaminated and control soils on the same time. Biomass forming capacity also fluctuated during the sampling season in spite of equal incubation conditions. Chemical analysis of soils showed only a very little accumulation of some heavy metals in the soil top layer. This had no disturbing effect on the general ecological functions of soil microorganisms. For its general importance in soil fertility and ecological functions, the microbial biomass-c undoubtedly represents an important indicator of soil quality. However, a slight anthropogenic pollution of soil may cause in an enhancement rather than in a decrease of the biomass content. Furthermore, a sampling season and soil characteristics other than pollution may strongly influence the analytical results. ACKNOWLEDGEMENT This research was supported by a grant from the Federal Environmental Agency, Berlin. REFERENCES Brookes P.C. (1995) The use of microbial parameters in monitoring soil pollution by heavy metals. Biol. Fertil. Soils, 19, Filip, Z. (1995) Microbiological and biochemical assessment of soil quality: The conception and some preliminary results of an international proposal. Proc. Soil Fertility Research Institute, Bratislava, 19/I,

7 Kaiser, E.A., Heinemeyer, O. (1993) Seasonal variations of soil microbial biomass carbon within the plough layer. Soil Biology and Biochemistry, 25, Vance, E.D., Brookes, P.C., Jenkinson, D.S. (1987) An extraction method for measuring soil microbial-c. Soil Biology and Biochemistry, 19, Williamson, W.M., Blunt,J.W., Greenfield, L.G. (1995) Method for rapid removal of ethanol from chloroform in soil microbial biomass determinations. Commun. Soil Sci. Plant Anal. 26 (3&4), Keywords : soil quality, atmospheric depositions, microbial biomass Mots clés : qualité du sol, dépôts atmosphériques, biomasse microbienne 7