Assessment of In-Use NOx Emissions from Heavy-Duty Diesel Vehicles Equipped with Selective Catalytic Reduction Systems

• DOI: 10.1021/acs.est.1c03042
• Publication Date: 2021-09-30T18:52:51Z
• Authors: Yi Tan; Seungju Yoon; Chris R. Ruehl; Jorn Herner; Paul Henderick; Tom Montes; Jenna Latt; Abraham Lee; Elena Florea; Sharon Lemieux; William Robertson; Shaohua Hu; Tao Huai
• Keywords: Selective catalytic reduction; Heavy duty; Nitrogen oxides

This work evaluated the nitrogen oxide (NOx) emissions of 277 heavy-duty diesel vehicles (HDDVs) from three portable emission measurement system testing programs. HDDVs in these programs were properly maintained before testing, so malfunction indicator lamp (MIL) was not illuminated. NOx some significantly higher than certification standard even during hot operations where exhaust temperature ideal for selective catalytic reduction to reduce NOx. For engines certified 0.20 g/bhp-hr standard, operation increased with engine age at 0.081 ± 0.016 per year. The correlation between and mileage weak because six trucks showed extraordinarily high apparent increase rates reaching several multiples within first 15,000 miles operation. overall annual this study two-thirds what observed real-world Caldecott Tunnel over past decade. would include those without proper maintenance, inclusion possibly explains difference rate increase. results suggest that need robust strategies better control in-use emissions.