The temporal variation is higher over the northern sub-basins and for dry and wet deposition separately. The monthly NOx deposition originating from BS ship-traffic emissions reached a maximum in the summer months due to higher dry deposition velocities, and a faster chemistry converting NO2 into scavengable chemical

species. The S deposition did not have as high a seasonal variation ( Figure 5). The decline in sulphur emissions due to the EU restrictions regarding fuel S content can be directly seen in the decrease in the S deposition towards 2011. The monthly average wet deposition share of the NOx deposition was highest in the northern BS sub-basins in winter (up to 80%) and autumn, and lowest during the spring months in the south ( Figure 6). The accumulated EPZ015666 cell line seasonal precipitation ( Figure 7) and the strength of the ice winter have a direct effect on the dry and wet deposition shares. The contribution of accumulated annual precipitation to the total BS varied from 556 km3 in 2010 to 839 km3 in 2008, but the seasonal see more precipitation sums over sub-pools did display different inter-annual variation. On average, winters were colder at the end of the period, being characterised by more northerly winds from clean areas and lower dry deposition over the ice cover. From 2008 to 2011 the HIRLAM winter (JFM) average MABL height dropped from 420–450 m to around 200 m over the northern BS

sub-basins ( Figure 8). The modelled SO2 and NOx (NO + NO2) concentrations in 2011 are presented in Figure 9, the average concentrations of ammonia, ammonium, total nitrate and sulphate in air in Figure 10. Figure 11 shows the modelled concentrations from BS ship emissions of SO2, NOx, sulphate and nitrate in air, in 2011, when the marine fuel S content reductions

were implemented. The modelled ship-originated concentrations of sulphate on BS coasts (Figure 11) were 0.1–0.5 μg (S) m− 3. The maximum 2010 annual average proportion of ship-originated sulphate, including direct SO4 emissions and secondary particles, occurred along the shipping routes. not Those modelled maximum proportions exceeded 60% of the modelled total SO4 over the open water areas at the mouth of the GoF, but this ship-emission originated SO4 share fell generally to 5–30% along the shores of sub-basins B1–B5, exceeding, however, 30% in the coastal areas of the southern BS where the ship routes run close to the coastline. For verifying the deposition of this study the monthly average concentrations in precipitation at 22–26 background stations are presented for the years 2008–2011 in Figures 12 and 13 in units of mg l− 1. When the intercomparison in units of mg m− 2 was calculated from daily values (Figure 14) the correlation coefficient was significant (0.6348, N = 5324) and the average annual modelled and measured depositions were close to each other: 0.64 and 0.60 mg (N) m− 2 respectively.