Ca-based adsorbents for NOx measurement in atmospheric environments surrounding monumental and archeological sites.

We found of particular interest to achieve information on the actual pollution situation of historic buildings and monuments, and also archeological sites which are often located in the middle of traffic-rich urban sites, with particular regards to the evaluation of NOx. In this paper we present the synthesis of different substrates with variable weight ratio CaO/Ca12Al14O33, namely 75:25 w/w (CM75), 35:65 w/w (CM35) and pure mayenite (PM), capable to react simultaneously with NO and NO2. We characterized the reactivity of mayenite by investigating the influence of water surface sorption. Hydration phenomena were found to play an important role in the process of NOx sorption and their subsequent conversion to nitrite and nitrate species. IR and TGA techniques were used to characterize the reaction products. We also devised a simple method to quantify the uptake of NOx taking into account the interference of CO2 in environmental conditions. We present a possible application of the calcium oxide based sorbents for the simultaneous determination of atmospheric NO and NO2 with passive sampling devices.