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HONO acts as a major OH source, playing a vital role in secondary pollutant formation to deteriorate regional air quality. Strong unknown sources of daytime HONO have been widely reported, which significantly limit our understanding of radical cycling and atmospheric oxidation capacity. Here, we identify a potential daytime HONO and OH source originating from photoexcited phenyl organic nitrates formed during the photoreaction of aromatics and NO x . Significant HONO (1.56-4.52 ppb) and OH production is observed during the photoreaction of different kinds of aromatics with NO x (18.1-242.3 ppb). We propose an additional mechanism involving photoexcited phenyl organic nitrates (RONO 2 ) reacting with water vapor to account for the higher levels of measured HONO and OH than the model prediction. The proposed HONO formation mechanism was evidenced directly by photolysis experiments using typical RONO 2 under UV irradiation conditions, during which HONO formation was enhanced by relative humidity. The 0-D box model incorporated in this mechanism accurately reproduced the evolution of HONO and aromatic. The proposed mechanism contributes 5.9-36.6% of HONO formation as the NO x concentration increased in the photoreaction of aromatics and NO x . Our study implies that photoexcited phenyl organic nitrates are an important source of atmospheric HONO and OH that contributes significantly to atmospheric oxidation capacity. more...

Basic fuchsin (BF) is an important dye used in textile and in biological and chemical assays, suspected of being carcinogenic. The environmental and occupational issues related to it are very important. This study aimed at investigating the sonochemical degradation of BF in water using high-frequency ultrasound waves (600 kHz). The effects of several operating parameters, namely initial substrate concentration, ultrasonic power, and liquid temperature (25–45°C), on the efficiency of ultrasonic process were investigated. Additionally, experiments were conducted in the presence of salts (NaCl and Na2SO4) as well as tert-butyl alcohol as a radical scavenger. The viability of ultrasound to degrade BF in natural water was also examined. The obtained results showed that ultrasound (600 kHz) is an efficient technique for removing BF. It was found that the initial degradation rate of BF increased with increasing initial dye concentration in the range 1–15 mg L−1and liquid temperature in the interval 25–35°C. The initial degradation rate increased by factor of 2.8 when the delivered power increased from 30 to 90 W. Excepting the salting out effect, the presence of salts, even at high concentration, has practically no significant effect on the efficiency of BF removal, making ultrasonic treatment as a promising technique for removing organic pollutants from industrial and natural waters. The presence of tert-butyl alcohol in a mass ratio of 1:1 (BF:alcohol) drastically inhibited the degradation rate of BF, making sure that hydroxyl radical was the main species involved in the degradation of this compound. [ABSTRACT FROM AUTHOR] more...