New insight into the effect of nitrogen on hydrocarbon degradation in petroleum-contaminated soil revealed through 15N tracing and flow cytometry

Heng Liu; Manli Wu; Minghui Zhang; Huan Gao; Zihao Yan; Zhao Yang

doi:10.1016/j.scitotenv.2023.164409

New insight into the effect of nitrogen on hydrocarbon degradation in petroleum-contaminated soil revealed through ¹⁵N tracing and flow cytometry

Sci Total Environ. 2023 Sep 15:891:164409. doi: 10.1016/j.scitotenv.2023.164409. Epub 2023 May 25.

Authors

Heng Liu¹, Manli Wu², Minghui Zhang³, Huan Gao¹, Zihao Yan¹, Zhao Yang¹

Affiliations

¹ Key Laboratory of Environmental Engineering of Shaanxi Province, School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
² Key Laboratory of Environmental Engineering of Shaanxi Province, School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Key Laboratory of Northwest Water Resources, Environment and Ecology, Ministry of Education, Xi'an 710055, China. Electronic address: wumanli1974@hotmail.com.
³ Ankang Ecological Environment Bureau Hanbin Branch, Ankang 725000, China.

PMID: 37244617
DOI: 10.1016/j.scitotenv.2023.164409

Abstract

Nitrogen (N) has been widely used to dissipate total petroleum hydrocarbons (TPH) in the oil-contaminated soil, but the relationships of hydrocarbon transformation, N cycling and utilization, and microbial characteristics during TPH biodegradation still remain unclear. In this study, ¹⁵N tracers (K¹⁵NO₃ and ¹⁵NH₄Cl) were used as stimulants for TPH degradation to compare the bioremediation potential of TPH in the historically (5 a) and freshly (7 d) petroleum-contaminated soils. During bioremediation process, TPH removal and carbon balance, N transformation and utilization, as well as microbial morphologies were investigated using ¹⁵N tracing and flow cytometry. Results showed that TPH removal rates were higher in the freshly polluted soils (61.59 % for K¹⁵NO₃ amendment and 48.55 % for ¹⁵NH₄Cl amendment) than in the historically polluted soils (35.84 % for K¹⁵NO₃ amendment and 32.30 % for ¹⁵NH₄Cl amendment), and TPH removal rate through K¹⁵NO₃ amendment was higher than that of ¹⁵NH₄Cl in the freshly polluted soils. This result was attributed to the higher N gross transformation rates in the freshly contaminated soils (0.0034-0.432 mmol N kg^-1 d^-1) when compared with that in the historically contaminated soils (0.009-0.04 mmol N kg^-1 d^-1), which led to more TPH transformation to residual carbon (51.84 %-53.74 %) in the freshly polluted soils than that in the historically polluted soils (24.67 %-33.47 %). Based on the fluorescence intensity displayed by the combination of stains and cellular components to indicate microbial morphology and activity, flow cytometry analysis showed that nitrogen addition was beneficial for the membrane integrity of TPH-degrading bacteria, and nitrogen also enhanced DNA synthesis and activity of TPH-degrading fungi in freshly polluted soil. Correlation and structural equation modeling analysis identified that K¹⁵NO₃ was beneficial to synthesize DNA of the TPH-degrading fungi but not the bacteria, which contributed to enhance TPH bio-mineralization in the soils with K¹⁵NO₃ amendment.

Keywords: Flow cytometry; Hydrocarbon transformation; N-cycling; Petroleum-contaminated soil; Structural equation model.

MeSH terms

Bacteria / metabolism
Biodegradation, Environmental
Flow Cytometry
Hydrocarbons / analysis
Petroleum* / analysis
Soil / chemistry
Soil Microbiology
Soil Pollutants* / analysis

Substances

Petroleum
Soil Pollutants
Hydrocarbons
Soil