Effects of crude oil contamination on soils of the Ural region

Abstract

Nowadays, crude oil contamination of soil is one of the widespread environmental problems. In this paper, we examine the impact of oil contamination on individual components of soil ecosystems at the physicochemical and biological levels. We investigated the hydrophysical properties, benzo[a]pyrene content, phytotoxicity, and toxicity for test organisms (Daphnia magna Straus, Escherichia coli) of the experimental crude oil-contaminated soils. The effects of the different levels of crude oil contamination of soil ecosystems on hydrophysical parameters, vegetative growth, the dynamics of microbial degradation of the benzo[a]pyrene, and level of toxicity to organisms of the different taxonomic groups have been examined. The findings indicate that the dependency of change in capillary moisture capacity upon concentration of crude oil is linear and the change of water absorption and infiltration time follows the power-law growth curve. Oil contamination affects the conditions of vegetative growth non-linearly. The floral component of a mixed coniferous-broad-leaved forest ecosystem is less susceptible to crude oil exposure than the floral component of the southern taiga. Varied dynamics of the microbial degradation of one of the chemical components of crude oil hydrocarbons (benzo[a]pyrene) in soil ecosystems at intervals of 40–100-g/kg of soil and 200–300-g/kg of soil was established. The soil becomes acutely toxic with oil concentration exceeding 200 g/kg of soil for animals (test organism D. magna Straus), and 40 g/kg of soil and 200 g/kg of soil for bacteria (test organism E. coli). The most disastrous effects occur when oil doses exceed 200 g/kg of soil. The study of hydrophysical and biological features of experimentally oil-contaminated soils of the Ural region added a new dimension to our knowledge about the impact of crude oil contamination on individual elements of ecosystems.