Estimating average Nitrogen Oxide emissions from inland waterway vessels using MAX-DOAS measurements

Nitrogen oxides (NO_x = NO + NO₂) have a negative impact on human health and play an important role in tropospheric air chemistry. Inland waterway vessels are equipped with long lasting diesel engines that emit NO_x and might have a significant impact on the local air quality. This is particularly relevant for the residential areas that are located along intensively used waterways, e.g. the Rhine River. Monitoring of NO_x emissions from inland waterway vessels could provide the local authorities with valuable information about ship contribution to air pollution.

In this presentation we show that ground-based MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) measurements, performed at the Rhine River in western Germany, are feasible for the emission plume identification from individual inland waterway vessels. However, especially for ships with rather low emissions, not always an unambiguous detection is possible, especially if the tropospheric NO₂ background is high and variable. For such cases we developed an automatic background correction, and we analysed the emissions in a more statistical way. The focus of this study is put on this method by investigating the height dependency of the averaging background-corrected NO₂ signals and finally estimating average NO_x emissions from inland ships.