| Press release

Combined Ammonia and Shipping Emissions Favour Particulate Matter Formation Notably in Coastal Regions

Ammonia, mainly emitted in agriculture, increases the formation of certain particulate matter in the air, thus facilitating pollution in the coastal regions. Particle formation is especially efficient in combination with shipping emissions. One of the main sources of ammonia emissions is animal husbandry. Anna M. Backes and her colleagues in the Department of Chemistry Transport Modelling within the Institute of Coastal Research at the Helmholtz-Zentrum Geesthacht (HZG) have demonstrated in a model study that, by halving ammonia emissions, the notable concentration of particulate matter in parts of Europe is reduced by one quarter in winter.

Graphic: NO3 concentrations

Concentrations of NO3 shown as µm/m3 for the reference case and two scenarios NEC2020 and RCAP, divided into summer and winter months. Graphic. Anna Backes

The ammonia (NH3) emissions follow an annual cycle and intensify between April and June as well as in September. This is due to widespread fertilization of fields during these periods. The scientists from the Department of Chemistry Transport Modelling within the Biogeochemistry in Coastal Seas Division demonstrated a connection in a model between NH3 emissions from agriculture and nitrogen oxides (NOx) as well as sulphur dioxides (SO2) emitted predominantly from shipping in the coastal regions of the North Sea. The occurrence of both emissions together considerably increases the formation of the smallest particulate matter (PM2.5) according to this study. Particles with a maximum size of 2.5 microns can find their way deep into human lungs and can therefore be damaging to respiratory health.

Development of Different Scenarios

The researchers developed three scenarios where the focal points were defined as "political" (NEC2020), "technical" (MTFR) and "behavioural" (RCAP). NEC2020 shows the politically targeted conditions in the year 2020 and is based on National Emission Ceilings (NEC). The MTFR scenario contains a technically feasible maximum emission reduction, while the RCAP scenario assumes a reduction in consumption of animal products. “We could show the most considerable reduction of NH3 emissions and therefore also of the particulate matter formation with the last simulation,” explains Anna M. Backes, environmental scientist at the HZG.

Greatest Effects Noticeable During Winter Months

Environmental Scientist Anna M. Backes from the Institute of Coastal Sciences.

Environmental Scientist Anna M. Backes from the Institute of Coastal Sciences. Photo: HZG/ Oliver Weiner

The most striking differences appear in the autumn and in winter months. With the NEC2020, the reduction of the PM2.5 particles amounted to merely two percent in winter, while with the RCAP simulated just under a quarter (24 percent) less particulate matter of the PM2.5 size class. The colder seasons better indicate the effects because particle formation increases through other emission sources such as frequent heating and through typical meteorological situations with more humidity and reduced air mixing. In addition, animal husbandry plays a greater role when considering the causes of NH3 emissions because field fertilization as an emissions source in the winter months is largely non-existent.

The expansion of atmospheric pollutants can be simulated with chemistry transport models (© DKRZ/HZG).

More information

Here you can find the complete study carried out by the Department of Chemistry Transport Modelling within the Division of Biogeochemistry in Coastal Seas:

Publication on Science Direct
  • Oliver Weiner Your thesis was the basis for this study. Who or what drew you to this topic and what precisely were you working on?
  • Anna Backes While watching an animation of dust pollution from ships, which we showed during an Open Ship event, I noticed that the concentration of particulates increased as soon as the exhaust plumes reached agricultural regions. In my thesis, I therefore looked at the connection between ammonia from agricultural sources and the emissions from transportation and industry.
  • Oliver Weiner How did the subsequent cooperation come about with the Chemistry Transport Modelling group at the Institute of Coastal Research?
  • Anna Backes I came across the working group during my coursework at Leuphana University and during my last semester of my environmental studies as an intern in the Chemistry Transport Modelling Department at the HZG. This then resulted in further cooperation and became the topic of my thesis.
  • Oliver Weiner The fact that agricultural processes can general be attributed to bad air quality has been known for quite a long time. What exactly is new within your work?
  • Anna Backes My work illustrates the potential for different emission reduction strategies. Animal husbandry, for example, contributes to a particularly large portion of the particulate matter concentration in the winter months and is therefore a sector that holds great potential for utilising such strategies. This fact was pointed out for the first time in this study.
  • Oliver Weiner You developed the RCAP scenario within the framework of this study. The scenario assumes a reduced reliance on animal products. How exactly did you translate this scientifically?
  • Anna Backes The societal Sufficiency Scenario is based on a Harvard Medical School study that recommends a considerable reduction in meat consumption. I have adjusted production in individual European countries based on the necessity that would arise from reduced consumption. It is a scenario that is geared to best illustrate potential. It does not reflect developments that could be expected in the near future, in part due to the fact it neglects certain factors such as exports.


Environmental Scientist

Anna M. Backes

Institute of Coastal Research

Phone: +49 (0)4152 87-1528

E-mail contact

Press and Public Relations

Oliver Weiner

Institute of Coastal Research

Phone: +49 (0)4152 87-2369

E-mail contact