Systems for reducing the content of residual pollutants from tailpipes emissions in an exhaust line having a cold part may include an ozone generation system; an MnO2 catalyst; and a lean NOx trap (LNT) catalyst. In these systems, the ozone, MnO2 catalyst, and LNT catalyst may be provided in the cold part of the exhaust line. In these systems, the residuals pollutants may be oxidized at temperatures of from about 20° C. to about 150° C. in rich or lean conditions and NO2 may have a concentration of less than 0.1 mg/km in the tailpipe emissions downstream of the cold part of the exhaust line. Corresponding methods may include generating ozone from an ozonizer; injecting the ozone in a mixing chamber comprising the residual pollutants to form a first mixture; converting the first mixture using an MnO2 catalyst to form a second mixture; and converting the second mixture using an LNT catalyst.