Monitoring shipping emissions in the German Bight using MAX-DOAS measurements

Abstract

Abstract. A 3-year time series of ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of NO2 and SO2 on the island Neuwerk has been analyzed for contributions from shipping emissions. The island is located in the German Bight, close to the main shipping lane (at a distance of 6–7 km) into the river Elbe towards the harbor of Hamburg. Measurements of individual ship plumes as well as of background pollution are possible from this location. A simple approach using the column amounts of the oxygen molecule dimer or collision complex, O4, for the determination of the horizontal light path length has been applied to retrieve path-averaged volume mixing ratios. An excellent agreement between mixing ratios determined from NO2 retrievals in the UV and visible parts of the spectrum has been found, showing the validity of the approach. Obtained mixing ratios of NO2 and SO2 are compared to co-located in situ measurements showing good correlation on average but also a systematic underestimation by the MAX-DOAS O4 scaling approach. Comparing data before and after the introduction of stricter fuel sulfur content limits (from 1 to 0.1 %) on 1 January 2015 in the North Sea Emission Control Area (ECA), a significant reduction in SO2 levels is observed. For situations with wind from the open North Sea, where ships are the only local source of air pollution, the average mixing ratio of SO2 decreased by a factor of 8, while for NO2 in the whole time series from 2013 to 2016, no significant change in emissions was observed. More than 2000 individual ship emission plumes have been identified in the data and analyzed for the emission ratio of SO2 to NO2, yielding an average ratio of 0.3 for the years 2013/2014 and decreasing significantly, presumably due to lower fuel sulfur content, in 2015/2016. By sorting measurements according to the prevailing wind direction and selecting two angular reference sectors representative for wind from the open North Sea and coast excluding data with mixed air mass origin, relative contributions of ships and land-based sources to air pollution levels in the German Bight have been estimated to be around 40 % : 60 % for NO2 as well as SO2 in 2013/2014, dropping to 14 % : 86 % for SO2 in 2015/2016.

Near-surface and path-averaged mixing ratios of NO<sub>2</sub> derived from car DOAS zenith-sky and tower DOAS off-axis measurements in Vienna: a case study

“…This is reasonable because those regions are known as rather rural areas without significant emission sources. The highest hOPLs estimated in our study are slightly lower than the mean value (12.9 km) reported in Seyler et al (2017), but still within the standard deviation.…”

Surveillance of SO<sub>2</sub> and NO<sub>2</sub> from ship emissions by MAX-DOAS measurements and implication to compliance of fuel sulfur content

“…Premuda et al (2011) used the ground-based MAX-DOAS measurements to evaluate the NO2 and SO2 levels in ship plume discharged from the single ship in the Giudecca Strait of the Venetian Lagoon. Seyler et al (2017) have utilized MAX-DOAS to perform long-term measurements of NO2 and SO2 from shipping emissions in the German Bight, and evaluated the reduction in SO2 levels after implement stricter sulfur limits in shipping fuel.…”

“…Remote sensing technique shows the advantages of fast detection, easy operation and high automation. Besides the passive "sniffing" method with in-situ instrumentation, optical remote sensing technique can detect the variation of the light properties after interaction with the exhaust plume and corresponding SO2 and NO2 emission in the plume, such as differential optical absorption spectroscopy (DOAS), light detection and ranging (LIDAR), and the ultraviolet camera (UV-CAM) technique (Balzani et al, 2014;Seyler et al, 2017). LIDAR system can be used to retrieve a 2-dimentional concentration distribution by scanning through the ship plume, and to obtain the ship emissions combing the wind and concentration profiles.…”

Surveillance of SO<sub>2</sub> and NO<sub>2</sub> from ship emissions by MAX-DOAS measurements and the implications regarding fuel sulfur content compliance

“…Sulfur dioxide (SO 2 ) and nitrogen dioxide (NO 2 ) are important air pollutants, and are also recognized as non-negligible components of ship emissions (Corbett et al, 1999;Endresen et al, 2003;Eyring et al, 2010;Matthias et al, 2010). Both of these species can engage in atmospheric chemical reactions to produce aerosols and acid rain, and also have negative effects on air quality, the climate system and human health, as well as contributing to the acidification of terrestrial and marine ecosystems (Berglen et al, 2004;Seinfeld and Pandis, 2006;Singh, 1987). Moreover, NO 2 is also the key substance involved in the formation of photochemical smog (Dimitriades, 1972).…”