Nitrous oxide is shown to undergo both a thermal and a photochemical decomposition at 296 K when it is adsorbed on various dry sands. The photochemical process occurs with light of wavelengths greater than 280 nm where gaseous N2O does not absorb. At low pressures (<0.1 torr) the half-life for the thermal decomposition of nitrous oxide to nitrogen when placed in contact with ~5 gms of heat treated Tunisian sand in a one-liter vessel was 350¿35 days. Under certain photolytic conditions this half-life was reduced. The efficiency of the photolytic process for a particular sand depends on the pressure (fraction of surface covered) and on the wave-length of light. For Tunisian sand at 1.1 torr and with the full mercury arc (<280 nm), the destruction efficiency is ~2¿10-5 molecules/incident photon.

These results indicate that particulate matter in the troposphere may be responsible for the decomposition of nitrous oxide and hence act as an atmospheric sink for N2O. However, moisture causes a drastic reduction in the number of molecules dissociated per incident photon.