Hydrocarbonates in atmospheric precipitation of Moscow: Monitoring data and analysis

• Published in: Izvestiya. Atmospheric and oceanic physics 2017-05, Vol.53 (3), p.334-342
• Main Authors: Eremina, I. D., Aloyan, A. E., Arutyunyan, V. O., Larin, I. K., Chubarova, N. E., Yermakov, A. N.
• Format: Article
• Language: English
• Subjects: Acid rain; Acidity; Alkaline earth metals; Ammonia; Ammonium; Ammonium compounds; Atmosphere; Atmospheric precipitations; Carbon dioxide; Carbon dioxide atmospheric concentrations; Carbonates; Chemical composition; Climatology; Condensates; Condensation; Condensation nuclei; Conversion; Data; Data processing; Deceleration; Earth; Earth and Environmental Science; Earth atmosphere; Earth Sciences; Environmental impact; Environmental monitoring; Equilibrium; Estimates; Exchanging; Geophysics/Geodesy; Hydrocarbons; Mass; Precipitation; Precipitation acidity; Precipitation monitoring
• ISSN: 0001-4338; 1555-628X
• DOI: 10.1134/S0001433817030069

Based on atmospheric precipitation monitoring data for Moscow, we have revealed a number of episodes when the content of hydrocarbonates repeatedly surpasses the equilibrium level. These facts are associated with the complex structure of precipitation, which is caused by differences in the chemical composition of condensation nuclei. As a result, the underlying surface involves two groups of drops with acidities of different nature. The acidity of the first (“metal”) group is determined by the carbonate equilibrium with atmospheric CO 2 and dissolved carbonates of alkaline and alkaline earth metals. The acidity of the second (“ammonium”) group is characterized by the balance between ammonia absorbed from the air and atmospheric acids. Because of this, the precipitation acidity measured during the monitoring is regulated not only in the air but also in the condensate collector. The mixing of the metal and ammonium groups of precipitation is accompanied by only a partial conversion of hydrocarbonates into dissolved CO 2 . Its termination is hindered when CO 2 actually ceases to enter the atmosphere due to mass-exchange deceleration. As a result, the content of hydrocarbonates in the collector exceeds the equilibrium level. Some estimates indicate that the acidity of the ammonia component of precipitation can be much higher than the acidity according to monitoring data. This should be taken into account in estimating the health and environmental impacts. The true level of acid rain hazard can be estimated only by measuring the acidity of individual drops, whereas the results obtained with modern tools of monitoring can underestimate this hazard.