Prof. HU Chunlei | Publications & Academic Profile | SinoGreenTech

Research Publications & English Decoded Briefs

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Environmental Chemistry•2026•DOI: 10.7524/j.issn.0254-6108.2025081103

Optimized Simulation of HONO Sources and Its Impact on Nitrate Formation in Guangzhou

Nitrous acid (HONO) is a critical precursor of hydroxyl radicals (·OH) in the atmosphere, influencing oxidative capacity and secondary pollutant formation. However, model simulations often underestimate HONO concentrations, and its role in nitrate formation remains unclear. This study investigates a typical winter haze episode in Guangzhou (January 2021, peak PM2.5: 243.0 μg·m−3) using observational data and a box model to quantify HONO sources and assess their impact on ·OH and particulate nitrate. HONO concentrations increased from (1.0±1.0) μg·m−3 during clean periods to (9.2±3.8) μg·m−3 during polluted periods, while nitrate rose from (6.4±3.4) to (43.3±20.0) μg·m−3 (6.8-fold). Incorporating seven additional HONO sources improved simulated daytime HONO from (0.3±0.1) to (6.5±2.3) μg·m−3, matching observations. Source apportionment showed direct vehicle emissions dominated (49.7%), followed by heterogeneous photosensitized reaction of NO2 on aerosol surfaces (23.0%), ground surface reaction (10.7%), and nitrate photolysis (8.7%). With optimized HONO, simulated daytime ·OH increased from (0.6±0.3)×10^6 to (1.5±0.8)×10^6 molec·cm−3 (1.2-fold), and nitrate production via ·OH+NO2 increased from (3.4±1.2) to (15.3±8.5) μg·m−3·h−1 (3.5-fold). The simulated-to-observed nitrate ratio improved from 21% to 81%. Sensitivity tests indicated that setting nitrate photolysis enhancement to 100 times gaseous nitric acid yielded better HONO and nitrate simulations. This study underscores the importance of refining HONO sources for accurate simulation of atmospheric oxidation and nitrate formation, aiding pollution control strategies.

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Environmental Chemistry•2026•DOI: 10.7524/j.issn.0254-6108.2025040401

Chloride-Induced Dual Electron Regulation on Zero-Valent Iron Surface for Highly Efficient Reductive Removal of Cr(VI)

Conventional zero-valent iron (ZVI) suffers from limited electron transfer due to its dense surface oxide layer. This study introduces a mechanochemical ball-milling strategy incorporating sodium chloride (NaCl) with ZVI to fabricate chloride-modified ZVI (Cl-ZVIbm). Using hexavalent chromium (Cr(VI)) as a model pollutant, Cl-ZVIbm exhibited a 76.5-fold enhancement in removal kinetics (0.0306 min−1 vs. 0.0004 min−1) compared to ball-milled ZVI (ZVIbm), achieving complete removal of 2 mg·L−1 Cr(VI) within 120 min. Spectroscopic characterization and density functional theory (DFT) calculations revealed dual regulation mechanisms: (1) Cl− substitution of surface hydroxyl groups alters coordination environments, enabling Cr(VI) adsorption via a bidentate binuclear configuration with adsorption energy reduced from –0.28 eV to –1.64 eV; (2) The strong electron-withdrawing effect of Cl− drives directional electron migration from the iron core to the surface, increasing surface Fe(II) content by 26.9% (67.5% vs. 53.2%) and facilitating direct electron transfer to reduce 99.5% of Cr(VI) into low-toxicity Cr(III). Notably, chloride leaching during reactions was only 0.0126 mmol·L−1, far below industrial wastewater discharge standards, confirming environmental compatibility. This work provides atomic-scale insights into chloride-mediated electronic modulation on ZVI surfaces, offering novel principles for interfacial engineering of environmental functional materials and a theoretical basis for heavy metal remediation technologies.

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