The impact of SO2 deposition from wash water on North Sea pH

A numerical modelling system consisting of a coupled hydro-dynamical model and a bio-geochemical model able to simulate the influence of ship-borne SO2 fluxes on the water properties has been established. The system has been set-up for the North Sea and a reference plus 3 scenario simulations have been carried out. The physical simulations are realistic in terms of the applied external forcings – i.e. meteorology, lateral boundary conditions and freshwater fluxes via rivers. The bio-geochemical simulations are realistic in the sense that they describe the carbonate system at high complexity using the ERSEM/carbonate model. These two models are dynamically coupled and run in online mode via FABM (Framework for Aquatic Bio-geochemical Models). The first simulation is the reference simulation using 2006 atmospheric CO2 concentration and not imposing any SO2 flux (best case, no shipping). The second simulation uses SO2 ship emission values from 2006 and atmospheric CO2 concentrations also from 2006. The third simulation uses SO2 from 2006 and CO2 concentration corresponding to present day values. Finally, the fourth simulation applies 5 times the SO2 concentrations from 2006 and CO2 from 2006. We found, as expected, the biggest changes are in the areas of the highest SO2 inputs. Due to advection/diffusion processes the effect is however geographical smeared and the overall pH changes are rather small. Increasing the atmospheric CO2 concentration from 383 ppm in 2006 to 400 ppm in 2015 has a much bigger impact on the pH decrease as that from ship borne SO2 emissions. Only when (unrealistically) multiplying the SO2 fluxes by 5 times a pH decrease comparable to the effect from increasing atmospheric CO2 could be found. It must however be considered that the impacts are cumulative and even small additional contributions from ship born SO2 lead to a further overall decrease of pH (acidification) and a consequent worsening of the marine environmental conditions.

STIPS Adolf;  BOLDING KRISTENSEN Karsten;  BRUGGEMAN Jorn;  MACIAS MOY Diego;  COUGHLAN Clare; 

2016-07-22

University of Bath

JRC101163

978-0-86197-193-0,   

https://publications.jrc.ec.europa.eu/repository/handle/JRC101163,