*2.2. Soil Characterization*

To characterize the soil used for analysis of the pH, content of petroleum products, total carbon, mobile phosphorus, available forms of nitrogen–nitrates from water soluble ammonia were determined.

Preparation of soil extract and determination of its acidity were performed according to Russian National Standard (RNS) 26483-85 [32] using a Metler Toledo Delta 320 pH meter. Determination of the total organic carbon in soil was performed according to [33]. The content of mobile (available) phosphorus P2O5 in mg/100 g was determined by the photocolorimetric method according to Kirsanov [34]. The determination of nitrates and water-soluble ammonium in the soil was carried out by standard photocolorimetric methods according to RNS 26489-85 [35] and RNS 26488-85 [36]. Petroleum products were determined by the gravimetric method [37]. Elemental analysis of soil was determined using X-ray fluoresce in the chemical analytical laboratory of the Geological Institute of the Russian Academy of Sciences.
