The RAUCH project investigated the contribution of inland shipping to air quality along the Rhine and adjacent waterways. Using a combination of ground‑based monitoring stations, helicopter‑borne measurements, and AIS‑derived vessel trajectories, the study quantified emissions of nitrogen oxides, particulate matter, black carbon, and ultrafine particles at several key sites. At the Worms bridge, the average additional NOx loading was 10.5 ± 2.5 µg m⁻³, representing 47 ± 18 % of the background concentration. NO₂ increased by 1.2 ± 0.4 µg m⁻³ (7 ± 3 % of background), while fine particulate matter rose by 0.36 ± 0.24 µg m⁻³ (4 ± 2 %). Black carbon showed a 0.14 ± 0.05 µg m⁻³ increase (15 ± 8 %), and ultrafine particle number concentrations increased by 742 ± 340 p cm⁻³ (11 ± 5 %). Similar patterns were observed at the Worms shore, Gernsheim shore, DEK canal bridge, and Koblenz pontoon, with peak contributions ranging from 1 % to 68 % of background for NOx and from 1 % to 33 % for black carbon. These results confirm that inland vessels emit significant amounts of reactive gases and fine particles, especially ultrafine particles that can penetrate deep into the respiratory tract.

The technical approach combined several modelling tools. Gaussian puff and plume models provided rapid estimates of plume dispersion, while the AUSTAL2000 code was used for detailed source‑to‑receptor calculations. The high‑resolution PALM (Parallelized Large‑eddy Simulation Model) was employed to simulate the complex flow around the Rhine’s banks and to map spatial variations in pollutant concentrations. Emission inventories were derived from AIS data, vessel type classifications, and engine performance parameters, and were validated against in‑situ measurements. Instrumentation included a folded‑tubular photometer for NO₂ and NO, a dual‑spot aethalometer for real‑time black carbon loading, and a particle counter capable of resolving ultrafine particles down to 10 nm. Data processing involved peak detection algorithms to isolate ship‑related emission events from background variability.

The project was funded by the German Federal Ministry for Education and Research (BfG) under grant number 2199 RAUCH, and was carried out from 2019 to 2022. Key partners comprised the German Federal Ministry for Digital and Transport (BMDV), the German Federal Institute for Geosciences and Natural Resources (BKG), and the Central Commission for the Navigation of the Rhine (CCNR). Academic collaborators included the Institute of Environmental Chemistry at the University of Stuttgart, the Institute of Transport and Logistics at the Technical University of Munich, and the German Aerospace Center (DLR). The consortium combined expertise in atmospheric chemistry, transport modelling, and maritime operations. The findings support the European Union’s proposal to integrate ultrafine particle monitoring into ambient air quality regulations and underscore the need for stricter emission controls on inland vessels to protect public health along major waterways.