Abstract: Petroleum extraction and its organic pollutants have numerous negative consequences on the composition and ecological function of grasslands, such as vegetation degradation, reduction in species diversity, and salinization. Thus, finding a comprehensive method for polluted soil and restoring grasslands faces many challenges, and the mechanism to influence soil environments and microbial community composition remains unclear. In this study, container experiments explored the potential of sulfonic acid group (–SO₃H groups) modified biochar combined with isolated bacterium (named Y-1, Acinetobacter-spp.) on physicochemical properties and microbial communities of polluted soil. The results show that modified biochar and Y-1 combined addition had the highest petroleum degradation rate (39.4%), and soil nutrients such as dissolved organic carbon (DOC), cation exchange capacity (CEC), available nitrogen, invertase and urease activities in CK were decreased by 35.4, 12.1, 30, 43.2 and 32.5% compared to treatments. The contents of available phosphorus in CM treatment were increased 2.4 times compared to CK. The –SO₃H groups efficiently improve salinity by accumulating Ca²⁺ and Mg²⁺ and inhibiting the aggregation of Na⁺. The correlation heatmap indicated that soil organic carbon, total nitrogen and CEC markedly interact with microbial communities. High-throughput sequencing indicated that the biomarkers enriched by the present integrated treatment are crucial for stimulating nitrogen and phosphorus cycles. The results indicate that -SO₃H groups modified biochar, and Y-1 has great potential to serve as a novel bioremediation technology to remediate soil from petroleum pollutants and alkalization and achieve better restoration of degradation grasslands.

Key words: Grassland degradation, Bioremediation, Modified biochar, Soil bacterial community