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

Inland waterway shipping is an important mode of freight transport in Europe with an extended network especially in Germany, e.g. the Rhine and Danube Rivers, and a variety of artificial channels. Nitrogen oxides (NO_x = NO + NO₂), which are also emitted by ships, play an important role in tropospheric chemistry. NO_x contributes to the formation of tropospheric ozone and thus photochemical smog. Moreover, NO_x affects human health and increases the acidification of ecosystems.  Monitoring of NO_x emissions from inland waterway vessels could provide cities that are located along the rivers with valuable information about ship contribution to the pollution.

In this study, ground-based MAX-DOAS (Multi AXis-Differential Optical Absorption Spectroscopy) measurements were performed along the Rhine River. The aim is to derive NO₂ emissions from individual ships. First sensitivity measurements showed that our Tube MAX-DOAS instrument is sensitive enough to detect a NO₂ signal that can be attributed to passing ships. However, finding the optimal measurement mode to determine the emissions proves to be a challenging endeavour.