Processes involved in uptake and release of nitrogen dioxide from soil and building stones into the atmosphere

Abstract

Atmospheric NO 2 was taken up by samples of various soils and building stones. The NO 2 uptake rate constants were highest in soil samples taken during the summer months. However, the NO 2 uptake rate constants of the soils and building stones were not significantly correlated with any of the following variables: moisture, pH, ammonium, nitrite, or nitrate. NO 2 uptake by soil and stone was not abolished by autoclaving indicating a chemical uptake process. NO 2 uptake by acidic and air-dry soils and stones resulted in nearly stoichiometric reduction of NO 2 to NO. This reduction was enhanced by the addition of ferrous iron and was further enhanced by incubation under 1 ppmv SO 2. The results suggest that NO 2 reduction may be coupled to oxidation of ferrous to ferric iron which may be reduced again by atmospheric SO 2 thus regenerating the ferrous iron content of the soil or stone. Conversion of NO 2 to NO was not observed in neutral or/and moist soils and stones. NO 2 was also taken up by purified and sterilized quartz sand moistend with water. This uptake was enhanced by addition of humic material but not by addition of bacteria which both had been extracted from genuine soil. Under most conditions, only uptake but no release of NO 2 was observed. However, NO 2 was released in air-dry soils that were heated to 45–65°C, or in ammonium-fertilized soil or stone that was drying up at room temperature. Under the latter conditions mimicking field practice, the NO 2 release reached rates that were similar to the NO release rates.