The 11th International Conference on Water Resource and Environment (WRE 2025)

Abstract: More frequent global wildfire events intensify the exposure risks of nitrophenols through brown carbon (BrC) emissions. Radical reactions dominate the fates of nitrophenols in surface, municipal, and atmospheric waters, yet the involved reaction kinetics and mechanisms remain poorly understood. In this work, by combining transient and steady-state multispectral analyses, the second-order rate constants (k) for nitrophenols and biomass-burning BrC reacting with HO• as well as common secondary radicals (e.g., Cl2•−, CO3•− and NO3•) were determined (k ~ 105−1010 M−1 s−1 at pH 2.0~10.0 for both protonated and deprotonated nitrophenols), most of which are reported for the first time. We also experimentally demonstrated that the reactions of nitrophenols and BrC with various radicals could produce a substantial amount of HONO/NO2− (a key precursor of tropospheric HO•), with molar yields reaching ~50%. Mechanistic investigations revealed that phenoxy radical (PhO•), generated either from either single electron transfer or addition-elimination reactions during the radical reactions of nitrophenols, acted as a universal intermediate for the de-nitration. Hence, the new kinetic and mechanistic insights suggest that radical-induced de-nitration process of BrC and nitrophenols in acidic waters may serve as a previously overlooked HONO source, but such de-nitration does not guarantee detoxification due to the simultaneous generation of high-risk biphenols. This work highlights the critical role of secondary radicals in nitrophenols and BrC transformation across different waters, shedding light on several unforeseen chemical impacts driven by intensified global wildfires.

Biography: Dr. Zhimin Qiang is a distinguished professor at the School of Environmental Science & Engineering, Shanghai Jiao Tong University. He was a recipient of the National Science Fund for Distinguished Young Scholars, and had served as the director of Drinking Water Science and Technology of Chinese Academy of Sciences, and the director of Sate Key Laboratory of Environmental Aquatic Chemistry of China. His research covers advanced treatment, green disinfection, and safe distribution of water and wastewater. Prof. Qiang has led over 40 research projects, published about 250 SCI papers (H index = 62) and 120 Chinese papers, and been recognized as a Highly Cited Researcher by Elsevier in China. He holds 20 innovation patents and has received 8 national/provincial honors and awards.