ESTIMATION OF THE BENZO[A]PYRENE EFFECT ON BIOLOGICAL ACTIVITY OF ROSTOV REGION CHERNOZEM

Abstract

The relevance of the research is caused by the importance in assessing the effect of long-term polycyclic aromatic hydrocarbons contamination using spring barley (Hordeum sativum distichum) on enzymatic activity of chernozems and the morphometric parameters of barley. Spring barley was used to assess the negative impact of chernozem soil pollution with benzo[a]pyrene as a well-known carcinogen and a mutagen among polycyclic aromatic hydrocarbons. The selected doses were close to the level of technogenic pressure in the studied zone: 0–800 μg benzo[a]pyrene kg–1. Benzo[a]pyrene content in soils during 4 years of the experiment affected the morphometric parameters of barley and the absorption of benzo[a]pyrene by plants, as well as the enzymatic activity of soils. The main aim was to assess benzo[a]pyrene effect on the chernozem biological activity in the Rostov Region. Objects. The investigations were carried out with a sample of soil taken from the upper (0–20 cm) layer of carbonate heavy loamy chernozem on the territory of the State Soil Preserve «Persian Protected Steppe» located in the Rostov Region (south of the Russian Federation), far from pollution sources. This soil has the following characteristics: Corganic – 3,4 %, pH – 7,3, exchange capacity cation – 37,1 mmol (+)/100 g–1; the content of CaCO3 is 0,1 %, the content of physical clay is 53,1 %. Methods. Model experiments were carried out under the natural conditions. Two kilograms of air-dry soil were sieved through a 1-mm-diameter sieve and placed into the 4 liters vegetative pots. The benzo[a]pyrene solution in acetonitrile was mixed with the soil to obtain final concentrations of benzo[a]pyrene in soil samples of 20, 200, 400 and 800 μg benzo[a]pyrene kg–1 (dry weight), which corresponds to 1, 10, 20 and 40 levels of maximum permissible concentration of benzo[a]pyrene. Clean soil was used as a control and, in addition, a background control was performed where acetonitrile was added similarly to the samples with benzo[a]pyrene. Results. The main factor influencing the increase in benzo[a]pyrene in soil and plants of model experiment was inoculation dose of toxicant in chernozem ordinary. The activity of oxidoreductase (catalase and dehydrogenases) of chernozem was inhibited with increasing benzo[a]pyrene content in the soil. The greatest toxic effect of benzo[a]pyrene was observed on the activity of dehydrogenases. Tendencies of pronounced phytotoxicity of soils were observed for all morphometric characteristics of spring barley, such as germination energy, length of shoots, plant weight and length of ears. The quantitative absorption levels of benzo[a]pyrene by the roots of spring barley exceeded the vegetative part by more than 2,5 times in all contaminated variants. Thus, the migration of benzo[a]pyrene to shoots and roots of spring barley from chernozem, accompanied by inhibition activity of dehydrogenases and catalase demonstrated the possibility of evaluating bioindication reactions during environmental monitoring to assess the effect of benzo[a]pyrene contamination.

Keywords

• benzo[a]pyrene
• soil
• spring barley
• morphometry
• catalase activity
• dehydrogenases activity
• correlative dependence