Systems and methods are provided for managing low temperature NO.sub.x and HC emissions, such as during a cold start of an internal combustion engine. The systems and methods include storing NO.sub.x and HC emissions at low temperatures and passively releasing and treating these emissions as the temperature of the exhaust system increases.
 The present invention was made with Government assistance from the U.S. Department of Energy (DOE) under contract No. DE-EE0004125. The U.S. Federal Government may have certain rights therein.