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Impact of selective catalytic reduction on exhaust particle formation over excess ammonia events

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Pages (from-to)11527-11534
Number of pages8
JournalEnvironmental Science and Technology
Issue number19
Publication statusPublished - 7 Oct 2014
Publication typeA1 Journal article-refereed


The introduction of selective catalytic reduction (SCR) aftertreatment to meet stringent diesel NOx emission standards around the world increases exhaust ammonia. Further to the direct air quality and health implications of ammonia, this may also lead to particle formation in the exhaust. In this study, an ammonia SCR system was examined with respect to its impact on both solid and total exhaust particle number and size distribution, downstream of a diesel particulate filter (DPF). Fuel post-injection was conducted in some tests to investigate the effect of ammonia during active DPF regeneration. On average, the post-DPF solid >23 nm and total x control. Ammonia did not have a significant additional effect on the high particle concentrations measured during DPF regeneration. Based on species availability and formation conditions, sulfate, nitrate, and chloride salts with ammonium are possible sources of the new particles formed. Ammonia-induced particle formation corresponds to an environmental problem which is not adequately addressed by current regulations.

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