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 (NOx = NO + NO2), which are also emitted by ships, play an important role in tropospheric chemistry. NOx contributes to the formation of tropospheric ozone and thus photochemical smog. Moreover, NOx affects human health and increases the acidification of ecosystems. Monitoring of NOx 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.