Phthalic acids are one kind of the major representative dicarboxylic acids detected in atmospheric aerosols. In the atmosphere, phthalic acids could be resulted from the photooxidation of aromatic hydrocarbons. Artificial sources, such as motor vehicle emissions and degradation and hydrolysis of phthalate esters, a main type of endocrine disrupting chemicals in the environment, also contribute to the abundance of atmospheric phthalic acids. Phthalic acids, like other dicarboxylic acids, can act as cloud condensation nuclei and affect the formation and acidity of precipitation, radiative force, energy balance, and consequently climate change. The fate of phthalic acids in atmospheric aerosols is largely governed by photodegradation due to directly exposure to UV radiation and various photoreactive species. Photodegradation of phthalic acid is also a key link in the full pathway of photodegradation of phthalate esters. Thus, studies on phthalic acid photodegradation not only have significance in elucidating the transformation and fate of phthalic acid in atmospheric aerosols but also help to clarify the total decomposition pathways of phthalate esters. The photodegradation of phthalic acid was studied under 300 nm UV irradiation in the absence and presence of nitrite or nitrate in a pH range 2-7. Under all conditions studied, the photodegradation rate of phthalic acid obeyed the first order kinetics. For both in the absence and presence of nitrite or nitrate, the degradation rate was pH dependent and was significantly higher in acidic conditions than in neutral conditions. The presence of nitrite or nitrate facilitated the photodegradation in the pH range 2-7 and these facilitation effects was more significant in acidic conditions. The effects of nitrite were much more significant than that of nitrate in acidic conditions. At pH 2, the first-order reaction constant Kobs was 0.0096 min-1 in the presence of 30 µM nitrate whereas it rose to 0.0581 min-1 in the presence of 30 µM nitrite. The findings are crucial for understanding the fate of phthalic acid in atmospheric aerosols and aquatic environments, and the roles of nitrite, nitrate, and the effect of pH values on the photodegradation of phthalic acids.

Photodegradation of o-phthalic acid and the effects of nitrite and nitrate

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.