Assessment of persistent organic pollutants load to marine environment by MAPPE-Global model focusing on European regional seas

MAPPE-Global modeling tool belongs to the group of the global box models for environmental fate and transport of POPs. The development of MAPPE-Global for atmosphere includes the relocation of chemical masses exported outside of each grid cell as a proxy of diffusive or advective transport, as well as the accounting of the eventual impact of the long range transcontinental transport in terms of globally "exported or imported" air emissions. In addition, the present version of the model improves the surface water compartment by introducing a global map of travel times to sea which parameter was considered earlier as a fixed value for a given river basin. Besides, the soil-air gas exchange in the soil compartment was bettered by accounting differences in the global land cover. No further improvement is done in the marine part of the model. The estimated error level of MAPPE-Global is about a factor of two, which suggests that the model could be considered as a tool for a screening or initial evaluation of chemical risk for POPs at global scale. The verified MAPPE-Global is applied in practical assessments of chemical loads to the European regional seas. The PCBs case study relates to a sum of 22 congeners and considers two emission scenarios: first - the current status relative to the 2010 year; second - a future projection corresponding to the 2020 year. The total amount of 22PCBs released to air equals to 101.03 t for year 2010 and to 50.2 t for year 2020, respectively. The Baseline scenario for Lindane assumes, for the reference year 2005, 86.6 t atmospheric emissions only from European sources and omits the impact of the long range atmospheric transport. The second scenario for Lindane aims to targeting the situation in the year 2020. This scenario (denoted as LRT) suggests no emissions to atmosphere from any European origin due to the banning of this substance but admits that Europe is affected by an unavoidable 'import" of 5.4 t Lindane through trans-continental air transport. According to the MAPPE-Global model, the extended European area is exporting to the marine water 3.7 t of 22PCBs in 2010 and 1.9 t in 2020, respectively. The observed reduction of 49% of the riverine load from year 2010 to year 2020 reflects the difference in the 22PCBs emissions. The riverine load represents about 4% of the total air emissions of 22PCBs. In both scenarios, the most affected seas are the Mediterranean Sea (ca.35% from the total) followed by Northern (ca. 21.5%) and Black sea (ca. 19%). It was estimated that the European seas receive by atmospheric deposition about 7.9 t of 22PCBs in 2010 and ca. 4t in 2020. This is two times more when comparing to the entire riverine discharge of 22PCBs for these years. MAPPE-Global forecasts 10.1 t riverine sea load of Lindane under the Baseline scenario and 0.26t in the case of LRT meaning 97% reduction compared to the baseline option. The riverine loads represent 11.7% and 5%, respectively, from the total air emissions of Lindane. The highest discharges are observed for Atlantic Ocean - in Baseline scenario 2.2t (21.8% from the total) and for LRT 0.06t (23%); and Mediterranean Sea - Baseline 3.5t (34.7%) and LRT 0.04t (15.4%). For the gamma-HCH, likewise for the PCBs, it is found that the atmospheric deposition over the European seas dominate the river input to the coastal zone. Under the Baseline scenario, the total air deposition (50.2t/y) is about 5 times higher than the riverine component of the sea load. However, in the case of LRT scenario, probably due to the very low amount of Lindane present in the atmosphere, the air deposition (in total 0.2 t/y) is equivalent to the riverine load of Lindane. Potentially the outcome of MAPPE-Global model could serve in the assessments of different policy options related to the EU Water Framework Directive (WFD) or Marine Strategy Framework Directive (MSFD) as well as to support the implementation of the European sea conventions as HELCOM (Baltic Sea), OSPAR (North-East Atlantic), MEDPOL (Mediterranean Sea) and BSC (Black Sea).