Unveiling natural aging behavior of biogenic sulfur

The practical application of biogenic sulfur (bio-S⁰) in environmental biotechnology is hindered by a limited understanding of its long-term dynamic behavior and its consequent impact on bioavailability. In this study, we systematically investigated the natural aging of bio-S⁰ over 200 days under outdoor conditions and evaluated its subsequent denitrification performance. Our findings revealed that aging induced progressive fragmentation and detachment of the surface organic coating, leading to enhanced exposure of the sulfur core and significant enrichment of bioavailable polysulfane species at the particle surface, accompanied by a reduction in sulfur crystallinity. These physicochemical changes markedly improved the bioavailability of bio-S⁰, as evidenced by a more than twofold increase in the nitrate removal rate for the 200-day aged samples compared to fresh ones. Microbial community analysis further demonstrated that aging selectively enriched Thiobacillus (from 60 % to 74 %), indicating a shift towards a more specialized sulfur-oxidizing consortium. This work provides novel insights into the dynamic nature of bio-S⁰ and offers pre-aging as a cost-effective and operationally simple strategy for enhancing the performance of bio-S⁰-driven biotechnologies.