Express-phytotest for choosing conditions and following process of soil remediation

Phyto- and bioremediation are perspective methods for soil recultivation. In spite of resistance of plant-hyperaccumulators and degrading microorganisms to some contaminants, there are soil toxicity limits for their growth and activity. Therefore, simple and express methods are needed to estimate the soil phytotoxicity. This article is devoted to description of an express-phytotest evaluated by germination rate of white clover (Trifolium repens) (Ph_CG) for estimating phytotoxicity of contaminated soils. This phytotest was developed on the example of grey forest soil contaminated with diesel fuel or copper(II) and approbated during our long-year experiments on adsorptive bioremediation of petroleum-contaminated soils. The sensitivity of the phytotest values Ph_CG to these contaminants is much higher compared to those phytotests evaluated by germination of larger seeds: cress (Lepidium sativum), and wheat (Triticum vulgare). A significant increase of Ph_CG in those soils by 10% was already recorded at 50-100 mg of available Cu²⁺ kg^-1 and 1-5 g total petroleum hydrocarbons kg^-1, depending on the hydrocarbon composition. The sensitivity of the standard phytotests evaluated by root length of wheat seedlings or by plant (T. vulgare or T. repens) biomass is higher than that of Ph_CG determination. However, bio- and phytoremediation are mostly applied for heavily contaminated soils. Therefore, use of the simple and cheap express phytotest for choosing optimal conditions of the soil remediation and following the process is quite justified. Besides, measuring an additional parameter-root length of the white clover seedlings may significantly increase the sensitivity of the express phytotest for lower contaminated soils.