Comparison of the application of unmodified and modified Biochar and microorganisms on some microbial and ecophysiological indicators of soil contaminated with crude oil

Introduction :

Due to the presence of refineries and oil-rich areas in our country, the need to use cost-effective and environmentally friendly methods is strongly felt. Biochar is a soil conditioner that is produced from the pyrolysis of organic residues and in addition to improving the quality of contaminated soils, it also improves the biological conditions of microorganisms involved in the bioremediation process. Using biochar in biological processes is very economical and affordable. Another point is that this material, compared to other similar products, is more economical and generally creates more tolerance in microorganisms against toxic compounds Based on this, a study with the aim of comparing the changes in the properties of biochar obtained from sugarcane bagasse and date palm through surface chemical activation with hydrogen peroxide (modified biochar) and unmodified biochar on metabolic, enzymatic activities and the amount of microbial biomass in a saline calcareous soil. Contaminated with crude oil was implemented.

Materials and methods:

In this research, an experiment was carried out in the form of repeated measurements in time. In the middle and at the end of the experimental period (60 and 120 days), the effect of different levels of unmodified and modified biochar of sugarcane and unmodified palm bagasse (1 and 2 %) along with microorganisms (with biochar and without biochar and a total of 57 test samples at two times) Some biological characteristics and eco-physiological indicators of soil including basic microbial respiration, substrate-induced respiration, microbial carbon dioxide, dehydrogenase enzyme, microbial contribution and metabolic contribution were investigated. The biochar used was prepared from sugarcane bagasse and date palm waste. Wastes were prepared, dried and pounded. Then they were heat treated at 400 degrees Celsius for 4 hours. Then kept for a while to cool. Then they were modified with 10% hydrogen peroxide and kept at room temperature for 24 to 48 hours. After that, they were placed in the oven at a temperature of 80 degrees Celsius for 24 hours and then they were ready to use. In order to measure basic microbial respiration using the method of Anderson et al. substrate-induced respiration using the method Alef and Nannipieri microbial carbon dioxide using the fumigation method, dehydrogenase enzyme activity using the method of Cassida et al and the microbial contribution was obtained by dividing the microbial biomass carbon by the organic carbon, and the metabolic contribution was obtained by dividing the basal respiration by the microbial biomass carbon.



Results and Discussion:

The analysis of variance table of repeated measurement of the effect of unmodified and modified biochar and microorganisms on the examined traits in the soil showed that in the outgroup effects, all treatments have significant differences with each other at the 1% level. In the intragroup effects, time had a similar status in all the investigated treatments. The interaction of time and treatments also showed a significant difference except in microbial biomass carbon and substrate-induced respiration in the rest of the treatments. The best results in dehydrogenase enzyme, microbial carbon dioxide, basal and substrate-induced respiration belonged to the treatment a mixture 4 (A mixture of modified bagasse 2 % and bacterial consortium 2 %) for 60 days. which has increased these traits by 70.98, 8.96, 53.97 and 53.54 percent respectively compared to the control treatment. The highest amount of microbial contribution belonged to the control treatment of 120 days and the highest amount of metabolic contribution also belonged to the treatment of a mixture 3 (Mixture of unmodified bagasse 1 % and bacterial consortium 1 %) for 120 days, which has increased this trait by 76.70% compared to the control treatment of 120 days.

Conclusion:

In this research, all the microbial identifiers measured in the soil showed a significant difference with the control treatment. Also, the results of this research showed that the addition of organic matter in soils contaminated with crude oil, such as unmodified and modified biochar, either alone or in interaction with microorganisms, can partially reduce the destructive effect of the stress caused by the pollutant (crude oil). Reduce the microbial community. Biochar modification using hydrogen peroxide, as a relatively cheap and environmentally friendly modifying agent, increased the effect of biochar on the studied biological and ecophysiological properties. So that the best results belonged to the modified treatments. And sugarcane bagasse biochar had better results than date palm waste. And in combination with microorganisms, this improvement was more. It should be noted that biochar was not only effective in remediation, but also stabilizes and neutralizes toxins. By using the results of this research, we can propose suitable solutions for their biological restoration according to the type of soil. Sugarcane bagasse biochar compared to date palm waste and the presence of microorganisms improved soil biological indicators. Therefore, Biochar modification using hydrogen peroxide, as a relatively cheap and environmentally friendly modification agent, increased the effect of coal on the studied biological and ecophysiological characteristics.