Scholarly record

PAHS BIOACCUMULATION IN SOIL-PLANT SYSTEM IN ARTIFICIAL CONTAMINATED MODEL EXPERIENCE

Svetlana Sushkova

Abstract

The aim of this article is assessment of the PAHs bioavailability and phytotoxicity on benzo[a]pyrene (BaP) example in model experiment with Haplic Chernozem and that spiked with various doses of BaP (20, 200, 400 and 800 ?g/kg) equivalent to 1, 10, 20 and 40 levels of maximal permissible concentrations (MPC) planted with spring barley (Hordeum sativum distichum). The main subject of this study is to research the bioindication of BaP contaminated soil in a model experiment to quantify the main features of BaP accumulation, phytotoxicity and degradation in soil-plant system with chernozem. The content of BaP in soil and plants was determined by using new ecologically friendly method of subcritical water extraction instead of traditional methods based on a large amount of organic solvents. The experiment was carried out with Haplic Chernozem, virgin, taken from the upper 0-20 cm layer of soil in the State Soil Preserve ?Persianovsky preserved steppe? of Rostov region (south of Russian Federation) located far from contaminated sources. This soil revealed the following physical and chemical characteristics: Corg 3.4%; pH 7.3; cation exchange capacity (CEC) 37.1 mMol(+)/100g; content of CaCO3 0.1%; physical clay 53.1% and clay 32.4%. The experimental soil samples were planted every spring and incubated outdoor during 4 years. The express-method of subcritical water extraction was used for BaP extraction from samples. The values of BaP period of semi-degradation in soil (T50, y) contaminated with 10, 20 and 40 MPC deviated from 1.4 to 1.8 years, while these values in low contaminated soils deviated from 2.9 to 5.4 years. The BaP concentrations in plants depended on initial BaP contamination and reduced simultaneously with diminish of BaP concentration in the related spiked samples. Growing of spring barley in the BaP spiked soils lead to BaP accumulation in plants. The bioaccumulation factors for BaP in roots and vegetative part of barley plants (BAFr and BAFv respectively) fluctuated within 0.035-0.065 and 0.015-0.025 respectively at the 1st season and then reduced about twice to the 4th season. Meantime those values in control soils vice-versa increased twice from 0.03 and 0.01 respectively. The spiked BaP revealed phytotoxic effect on growth of spring barley even in low dose equal to 1MPC. The most sensitive indicators of the BaP contamination are length of vegetative part and ear hight, which reduced more than 20% at initial BaP content in soil about 30 ?g/kg. The other morphometric characteristics of spring barley (germination energy and plant weight) reduce significantly at BaP content in the soil 150-200 ?g/kg. Meantime the root length was not sensitive characteristic of the plant.

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