Natural attenuation of p-nitrophenol in soil: kinetics, microbial dynamics, and functional gene responses
Yingbo Dong, Yujie Qiao, Hai LinContext
p-Nitrophenol (PNP) is a key intermediate in pesticides, pharmaceuticals, and dye industries, and can significantly disrupt soil ecosystem functions and pose risks to human health through bioaccumulation. The biodegradation behaviour of PNP under natural attenuation and its microbial response mechanisms remain inadequately understood.
Aims
This study investigated PNP degradation kinetics, coupled dynamics of soil properties and microbial communities, and key functional taxa/genes under natural attenuation.
Methods
A 168-day experiment in a sand box was conducted using PNP-contaminated soil. Concentrations, physico-chemical properties, enzyme activities, microbial communities (16S rRNA/ITS sequencing), and C/N cycling genes (KEGG annotation) were analyzed at multiple time points.
Key results
PNP with an initial concentration of 10–40 mg kg−1 degraded to the safe threshold (2 mg kg−1) within 126 days. The degradation process followed first-order or biphasic first-order kinetic models and was significantly correlated with changes in soil physico-chemical properties, with ammonium nitrogen, nitrate nitrogen, and organic matter being key environmental factors. Microbial diversity, reduced in high-contamination zones, gradually recovered as PNP degraded, peaking on Day 126. Bacillus and Penicillium dominated the early degradation stage, while Sphingomonas and Arthrobacter became predominant in later stages. Key functional genes involved in carbon and nitrogen cycling showed peak expression on Day 84.
Conclusion
PNP natural attenuation involves rate-limited degradation phases driven by successional shifts in degrading communities and functional gene expression. These findings confirm that biodegradation proceeds through distinct phases corresponding to community succession and functional gene dynamics.
Implications
Regulating soil moisture, aeration, and nutrient conditions can enrich functional degraders, providing a theoretical basis for in situ bioremediation of PNP-contaminated soils.