VI. Alps-Adria Scientific Workshop Obervellach, Austria 2007. DOI: 10.1556/CRC.35.2007.2.149 761 CHANGES IN THE PARTS OF THE RHIZOSPHERE PHOSPHORUS CYCLE INFLUENCING BY HEAVY METAL CONTAMINATION Péter MÁTHÉ 1 – Gabriella MÁTHÉ-GÁSPÁR 2 – Tibor SZILI-KOVÁCS 2 – Emese SIPTER 3 – Attila ANTON 2 1 Károly Róbert College, 3200 Gyöngyös, Mátrai st. 36., Hungary 2 Research Institute for Soil Science and Agricultural Chemistry of the Hungarian Academy of Sciences, 1022 Budapest, Herman O. st. 15., Hungary, ggabi@rissac.hu 3 Semmelweis University, Department of Labor and Environmental Health, 1096 Budapest, Nagyvárad sq. 2., Hungary Introduction Phosphorus is one of the major elements for metabolic processes of living organism. Soils are known to vary widely in their P supply capacities, because only a small fraction of the total P in soil is in an available form, which determines chemical bounding and its transformation correlation with soil moisture and temperature (Sárdi et al. 2006). In acid soils P adsorption is generally attributed to hydrous oxides of iron and aluminium, or clay. In alkaline soils or in lime soils (Füleky 2006) various forms of calcium phosphates are the stable minerals that govern P concentration in soil solution. The ratio of the inorganic and organic phosphorus form is determined by soil origin. Organic phosphorus is generally higher in clay soils than in coarse-textured soils, but lower than humus soils (Dalal 1977). Organic phosphorus content of Hungarian soils is ranged between 0.5-43 % (Fábryné 1969) and a brown forest chernozem soil represents the highest value (50 %). Soil phosphatases are essential factors in cycling soil phosphorus. Sources of these enzymes are the soil microbial community and plants roots or residues and can be affected by several ecological factors (soil organic carbon, phosphorus, clay and lime content, soil pollution) (Máthé 1978, Máthé et al. 1994, Paşca et al. 1998, Máthé-Gáspár et al. 2006). Observed site of our study was surrounding area of the Pb/Zn mine at Gyöngyösoroszi (North-East-Hungary), characterized by elevated metal contamination (Pb, As, Cd, Hg and Zn). Heavy metal pollution changes availability of the nutrient element (Csathó 1994, Kádár 1995). Effect of heavy metals on the available phosphorus content is direct (e.g. non-soluble inorganic compound with Pb) and indirect, determining hydrolysis of organic phosphorus sources by phosphatases, and so phosphorus cycle. Toxic metal decreases microbial biomass in soils (Brookes 1995, Szili-Kovács et al 1998, Szili-Kovács et al. 2006) and can inhibit transformation (humification) of soil organic matter and increase the ratio of labile to total fraction (Máthé et al. 2004). Object of this work was to observed differences in phosphorus forms of unpolluted and polluted soil, and to study the effect of heavy metals on acid phosphomonoesterase activity, microbial biomass, and water extractable organic carbon content of soils. Materials and methods Observed sites (sediment area along the Toka-creek) are located near abandoned Pb/Zn mine at Gyöngyösoroszi village (North-East Hungary with an area of 1200 m 2 . Soil samples were taken at unpolluted, which lies higher distance from the river, and polluted areas along the Toka-creek.