The distribution of cadmium, lead and zinc in exchangeable, organic, and 2M HNO3-extractable fractions as well as the effect of heavy metal concentrations on soil microflora was investigated. Six sampling transects were chosen in theLitavkaRiveralluvium in 1999–2001. Concentrations of all metals increased with decreasing distance from the source of contamination. The concentrations of Cd and Zn in exchangeable fraction were higher than in organically bound fraction, a reverse trend was found in Pb speciation. All measured parameters of soil microbial activity were affected by heavy metal concentrations. The decrease in CFU was most significant in the case of oligotrophic bacteria and spore-forming bacteria. Significant inhibition of C-biomass occurred in soils highly contaminated by heavy metals. The Cbiomass:Cox ratio decreased with increasing soil pollution. Generally, the values of enzymatic activities were highest in the soil above the source of contamination and they were decreased as approaching the source of contamination. Our results demonstrate that several parameters of microbial activity could be used as good indicators of increasing concentrations of Cd, Pb, and Zn in soil.

Microbial parameters derived from the short-term Michaelis-Menten type model are tested and applied on the ecosystem study. Soil dried immediately after sampling and stored at 4 o C was moistened to 60% water holding capacity and CO 2 production was measured (GC) after 24 h (respiration response to water supply, V DS ) and between the 5 th and 6 th day of incubation (basal respiration V BR ). Then glucose was added into the soil and CO 2 production was measured 16 to 24 h later (maximum respiration, V MAX ). Substrate saturation kinetics of respiration was measured after addition of glucose in 6 different concentrations. Soil heterotrophic respiratory potential was expressed as V DS /V MAX ratio; biologically available C (AC BR ) and potential flush of the biologically available C (AC DS /AC BR ) was estimated using Michaelis-Menten type model. It is shown that the above parameters can get relevant results because they meet the basic assumptions: (i) Fitting of Michaelis-Menten type model is accurate (R 2 R R = 0.956-0.994), (ii) microbial respiration is substrate limited in natural conditions, (iii) V MAX is relatively invariable for a wide range of C substrate concentrations and microbial populations are not growing. (iv) After moistening of the soil, extra C is released, the amount of which is characteristic for the given soil. Application of the short-term kinetic approach on the upper soil layer of various 229