Biochemical components of nitrogen balance in soil under crude oil contamination and phytoremediation
Authors:   Ivan Franko National University of Lviv, Mekich Marta , Bunio Lubov ,   Ivan Franko National University of Lviv, Теrek Olha ,   Ivan Franko National University of Lviv
Published: June 2024

Introduction. Nitrogen availability in oil contaminated soil is adversely affected due to an increase in the inorganic carbon (C) and nitrogen (N) ratio, unfavorable changes in physical, chemical and biological properties of the soil. Phytoremediation of oil contaminated soil may have a positive effect on N cycling. Changes in soil enzyme activity, content of organic and mineral N in the soil can be used as indicators of nitrogen balance. This paper aims to identify some biochemical elements of N cycling in oil contaminated soil and the effect of plants in recovering N balance in the soil. Materials and Methods. In this study artificially oil contaminated soil (50 mL of crude oil per 1 kg of soil) was remediated by plants Zea mays L. and Vicia faba var. minor. Soil samples were collected on the 10th day after oil pollution, on the 22nd day (seeds were sown), on the 65th day (30 days of plants’ growth), and on the 95th day (60 days of plants’ growth). Soil without oil and plant vegetation was used as control. We determined the nodulation ability of soil, activity of soil protease and urease, content of labile organic nitrogen and free amino acids accumulation in the soil. Results. Our study revealed the absence of nodules on V. faba roots in oil contamination conditions. Protease activity was inhibited in oil contaminated soil compared to control. Under plant vegetation and oil contamination conditions, soil protease activity increased on the 65th day, and decreased on the 95th day compared to oil contaminated soil without plants. Amino acid concentration was significantly smaller for oil contaminated soil during the experiment than for soil without oil, but amino acid content was significantly greater for soil planted with Z. mays than for soil without plants. V. faba had a stimulating effect on amino acid accumulation only for uncontaminated soil compared to soil without plants. The results have shown that the urease activity decreased in oil contaminated soil during all experimental period. Results indicated that 22 days after oil pollution, the content of labile organic N decreased in oil contaminated soil, whereas on further stages of the experiment it was not significantly different compared to control. Significant reduction of labile N was revealed for oil contaminated soil with Z. mays plants on the 95th day and with V. faba plants on the 65th day compared to uncontaminated soil with plants. Conclusions. Oil-contamination had a negative effect on all studied biochemical characteristics of soil: protease activity, urease activity, labile organic nitrogen, free amino acids accumulation. In oil contamination conditions the positive effect of Z. mays and V. faba plants was determined for protease activity on the 65th day, a positive effect of Z. mays plants on accumulation of free amino acids accumulation was observed on the 95th day. The shortage of labile N in oil contaminated soil increased during phytoremediation. Therefore application of Z. mays and V. faba plants for optimization of biochemical components of N balance in oil contaminated soil may be controversial and requires further exploration.