Pedosphere 36(5): 1150--1162, 2026
ISSN 1002-0160/CN 32-1315/P
©2026 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| How is microbial biomass carbon affected by oil pollution in soils? An alternative approach to measurement |
Shokufeh MORADI1, Mohammad Reza SARIKHANI1 , Ali BEHESHTI ALE-AGHA2 |
1 Department of Soil Science, Faculty of Agriculture, University of Tabriz, Tabriz 5166614776 (Iran);
2 Department of Soil Science, Razi University, Kermanshah 6714414971 (Iran) |
| ABSTRACT |
| Soil biological properties, such as soil respiration, enzyme activities, and microbial biomass carbon (MBC), serve as suitable indicators for understanding and monitoring the effects of oil pollutants on soil health and quality. There are several indirect methods to measure MBC, the most important of which are chloroform fumigation extraction (CFE), chloroform fumigation incubation (CFI), and substrate-induced respiration (SIR). Due to the presence of high oil content and elevated organic carbon (OC) levels in oil-contaminated soil samples, the application of the CFE method has limitations, as tracking minor changes in MBC against a high OC background is not feasible; therefore, in this study, 120 oil-contaminated soil samples were collected from four selected locations at polluted sites in Naftshahr, Kermanshah, Iran, and the effect of three levels of oil pollution, low (L), moderate (M), and high (H), on MBC was evaluated using the other two indirect methods through an incubation experiment. The results showed a positive and significant correlation between MBC using CFI (MBC-CFI) and SIR (MBC-SIR) (r = 0.91, P < 0.01). In both methods, the MBC obtained in H soils was higher than in L and M soils. The values of MBC-CFI data ranged from 2 646.85 mg C kg-1 in L soils to 4 194.59 mg C kg-1 in H soils. Among the four empirical formulas used in this study, the equation, MBC-SIR = 40.04SIR + 0.37, yielded the lowest root mean square error (RMSE) and scatter index (SI). The MBC-SIR measured by this equation ranged from 2 902.24 mg C kg-1 in L soils to 4 781.07 mg C kg-1 in H soils. Based on the results of this study, the method based on SIR, particularly the aforementioned empirical formula, can be effectively used to estimate MBC in oil-contaminated soils. Additionally, multiple linear regression analysis (MLR) and principal component analysis (PCA) were performed on the data to explore the relationships among soil biological, physical, and chemical properties, particularly in relation to MBC. Results from PCA indicated that the first two components explained approximately 73% of the variance in the test data. Given the high eigenvector values of biological and chemical parameters in the first component and those of physical parameters in the second, the first component can be termed the biochemical component and the second the physical component. The MLR equation also revealed that SIR was the most influential parameter affecting MBC (R2 = 0.84). |
| Key Words: biological indicators,chloroform,empirical formula,fumigation incubation,method evaluation,microbial respiration,petroleum contamination,soil respiration,substrate-induced respiration |
| Citation: Moradi Sh, Sarikhani M R, Beheshti Ale-Agha A. 2026. How is microbial biomass carbon affected by oil pollution in soils? An alternative approach to measurement. Pedosphere. 36(5): 1150-1162. |
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