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Assessing the steady-state [*NO2] in environmental samples. Implication for aromatic photonitration processes induced
Claudio Minero1, Valter Maurino, Ezio Pelizzetti
1Dipartimento di Chimica Analitica, Università di Torino, Via Pietro Giuria 5, 10125 Torino, Italy.
Environmental Science and Pollution Research International
|August 3, 2007
Summary
Nitrite (NO2) is formed in atmospheric water droplets through nitrate photolysis, significantly impacting phenol transformation into nitrophenols in both air and surface waters.
Area of Science:
- Environmental Chemistry
- Atmospheric Chemistry
- Photochemistry
Background:
- Nitrate photolysis is a known process in aquatic environments.
- The formation and role of nitrite (NO2) in atmospheric water have not been fully elucidated.
- Understanding NO2 sources is crucial for predicting pollutant transformation.
Purpose of the Study:
- To calculate the steady-state concentration of nitrite (NO2) in environmental aqueous samples.
- To compare NO2 formation via photochemical processes in atmospheric water droplets versus gas-phase transfer.
- To assess the significance of nitrite oxidation and nitrate photolysis as NO2 sources in different water bodies.
- To evaluate the impact of calculated NO2 levels on phenol transformation.
Main Methods:
- Utilized literature data for nitrate (NO3-), steady-state hydroxyl radical (*OH), and *OH generation rates.
- Calculated steady-state *NO2 concentrations based on photolysis and oxidation processes.
- Compared NO2 formation rates in atmospheric water droplets and from gas-phase transfer.
- Assessed the relative importance of nitrite oxidation versus nitrate photolysis.
- Modeled the transformation of phenol to nitrophenols.
Main Results:
- Steady-state *NO2 concentrations were calculated using existing literature data.
- Photochemical processes in atmospheric water droplets generated one to two orders of magnitude more *NO2 than gas-phase transfer.
- Nitrite oxidation was relatively more important than nitrate photolysis as an *NO2 source in atmospheric waters compared to surface waters.
- Calculated *NO2 levels can significantly transform phenol into nitrophenols in both atmospheric and surface waters.
Conclusions:
- Photochemical formation of *NO2 in atmospheric water droplets is a significant process.
- *NO2 plays a crucial role in the transformation of phenol to nitrophenols in aquatic and atmospheric environments.
- Further research into atmospheric nitrite chemistry is warranted.
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