appropriate amount of reductant into the exhaust stream at the appropriate time in another embodiment of the invention illustrated in fig2 the exhaust treatment system may further optionally include a lean no x trap lnt 26 positioned downstream from the doc 14 to aid in further reduction of no x in the exhaust gas the lnt 26 comprises one or more platinum group metals and preferably comprises a mixture of platinum palladium and rhodium preferably the lean no x trap has a precious metal loading of from between about 30 to about 300 g ft 3 the lean no x trap further comprises a no x adsorbent material selected from one or more alkali or alkaline earth metals it should be appreciated that in embodiments which include a lean no x trap the use of the reductant delivery system is optional as the lean no x trap generates ammonia during its operation also as shown in fig2 the exhaust treatment system may further include a diesel particulate filter 28 downstream from the scr catalyst for collecting soot and particulate matter the diesel particulate filter is preferably a wall flow filter comprising a highly porous filter substrate having a porosity of from about 30 to 80 the size of the pores preferably range from about 10 to 50 u03bcm it should be appreciated that the distribution of pore sizes may vary throughout the filter substrate suitable filter substrates include refractory inorganic oxides or ceramic or metal materials.