ISSN 0147-6874, Moscow University Soil Science Bulletin, 2010, Vol. 65, No. 4, pp. 179–182. © Allerton Press, Inc., 2010. Original Russian Text © M.A. Timofeev, V.A. Terechova, P.A. Kozhevin, 2010, published in Vestnik Moskovskogo Universiteta. Pochvovedenie, 2010, No. 4, pp. 44–47. 179 INTRODUCTION Great importance in environmental ecological monitoring is attributed to biotic indicators. They contain unique information that cannot be collected using physical and chemical tests alone. In particular, chemical analysis reveals the presence of pollutants, but, given its understandable limitations, it cannot provide an unambiguous characterization of the con- dition of soil biota and the ecosystem generally, or pre- dict future events. Biotesting techniques allow one to make an integral assessment of ecological hazard lev- els [17]. The main principle of biotesting lies in determining the action of environmental samples on biological test specimens, which allows one to determine the integral biological effects of the totality of adverse environ- mental factors [13]. Special studies are required to understand the technique’s capabilities and limita- tions, especially when the observed reactions of test subjects reflect the action of other factors than only pollutants, in situ. Such situations are typical in the analysis of soil as a complex heterogeneous system. The development of a biotesting system allowing one to not only ascertain the fact of contamination, but also to obtain qualitative and quantitative characteris- tics is no less topical [13]. In order to solve such prob- lems, analysis utilizing the methods of multidimen- sional mathematical statistics is called for [1]. Microbiological testing techniques, including pol- lution-induced community tolerance of microorgan- isms (PICT) are of especial interest for obtaining the qualitative and quantitative characteristics of contam- ination [14]. In this case, communities in soil samples themselves, rather than individual organisms and pop- ulations, play the role of test subjects [4]. In this work, the range of biosystems that are suit- able for the efficient ecotoxicological assessment of soil samples in soils has been determined based on the example of cadmium pollution. EXPERIMENTAL This study was conducted on sod–podzol soil (from the Moscow oblast) and modal chernozem (from the Tula oblast) samples collected from the top (0–20 cm) horizons, as well as on model soil mixture samples having the following composition: terrestrial peat (10%), kaolin clay (20%), and quartz sand (70%) (as per ISO 11268-1). At the first stage, physical and chemical techniques were used on the soils and model mixture to determine the acidic and basic properties and assay organic mat- ter, mobile phosphorus, as well as potassium com- pounds and silt. In the main experiment, cadmium chloride solu- tions were introduced into soil and model mixture samples at two levels: 25 and 250 mg/kg of soil (10 and 100 threshold limit values (TLV), respec- tively), and the samples were subsequently moistur- ized (0.005 MPa). They were thoroughly mixed to ensure even distribution of the toxicant [16]. Incubation was carried out in a thermostat at 25°C. Samples for analysis were collected 7 and 30 days after the introduction of cadmium. The 1st week was pre- sumed to be a period of acute toxicity with probable inhibition of microbial growth. Prolonged incubation for 1 month was designed to test the possibility of in situ formation of pollution-resistant microbial populations. Eleven biological techniques were used for ecolog- ical assessment. Six of these are biotesting systems; the test organisms included Raphanus sativa radish seeds (three-day germination power test; 7-day germination capacity, specific length and sprout biomass test) [11]; crustaceans Ceriodaphnia affinis (48-hour immobili- zation test) [8]; microscopic algae Scenedesmus quad- ricauda (72-hour population growth inhibition test) [6]; an in vitro homoiothermal animal cell culture (3-hour express test based on the change in the motil- ity of bovine sperm cells) [5]; Paramecium caudatum (24-hour immobilization test) [9]; and luminescent biosensor Ecolum (30-minute bacterial luminescence Biotesting for Cd Pollution in Soils M. A. Timofeev, V. A. Terechova, and P. A. Kozhevin Received May 11, 2010 Abstract—The potential of biotesting to detect and analyze Cd pollution in soils was studied. This paper identifies a number of approaches, such as PICT and discriminant analysis, which may open new perspectives for ecotoxicology. Keywords: cadmium, soil pollution, biotesting, ecotoxicology. DOI: 10.3103/S0147687410040095