Assessment of Atmospheric Lead, Cadmium and Mercury Pollution to the OSPAR Maritime Area in 2020
Executive Summary
Model assessment of atmospheric pollution of the OSPAR maritime area by heavy metals in 2020 was carried out. The assessment includes the information on time series of lead (Pb), cadmium (Cd) and mercury (Hg) emissions in the OSPAR Contracting Parties for the period from 1990 to 2020, sectoral emissions in these countries in 2020, deposition of Pb, Cd and Hg to the OSPAR regions in 2020 and their trends for the period 1990-2020. Besides, evaluation of the modelling results against measurement data is presented.
Total Pb, Cd and Hg emission in the OSPAR Contracting Parties as a whole in 2020 amounted to 483, 32 and 20 tonnes, respectively. Reduction of Pb, Cd and Hg atmospheric emissions in the OSPAR Contracting Parties from 1990 to 2020 was 97%, 76% and 86%, respectively. The largest reduction of Pb is noted for France and Sweden (98% each). Finland is known for the most significant (90%) decrease of Cd emission. The strongest reduction of Hg emission was reached in Denmark (93%). Emissions of Pb, Cd and Hg are characterized by stronger reduction rate in the first decade of the considered period compared to the reduction from 2000 to 2020.
Reported heavy metal emission data for the OSPAR Contracting Parties are split into 13 emission source categories (sectors). Contributions of emission sectors to total emission were analysed. The main emission sectors contributing to the OSPAR Pb emission are B_Industry (45%), F_RoadTransport (32%) and C_OtherStatComb (10%). The main contribution to Cd total emission is made by the sector B_Industry (58%), followed by C_OtherStatComb (14%) and E_Solvents (11%). The sectors B_Industry (46%) and A_PublicPower (29%) are the largest contributors to total Hg emissions in the OSPAR countries.
The highest spatial mean deposition fluxes of Pb (0.29 kg/km2/y) and Cd (10.3 g/km2/y) in 2020 were noted for Region II. The lowest fluxes (0.14 kg/km2/y and 5.1 g/km2/y, respectively) took place in Region I. In case of Hg, Region I is characterized by the highest (8.9 g/km2/y), and Region IV - by the lowest (4.8 g/km2/y) spatial mean deposition flux. Deposition of Pb, Cd and Hg to the OSPAR maritime area substantially declined from 1990 to 2020. The strongest decline of Pb, Cd and Hg deposition took place in Region II (Greater North Sea) and amounted to 87%, 81% and almost 50%, respectively. The decline of deposition to the OSPAR regions is smaller than the emission reduction because of the effect of secondary and global sources.
Evaluation of the modelling results against measurements demonstrated that the model tends to somewhat overestimate observed concentrations of Pb and Cd in air. The agreement between modelled and observed Hg concentrations in air is within ±15% at most of stations. Wet deposition of Pb, Cd and Hg were reproduced with mean relative bias of -26%, -42% and 16%, respectively. For the majority of stations the modelled and observed concentrations and deposition fluxes agree within a factor of two.