Long-term trends of heavy metal atmospheric deposition to the North-East Atlantic
Executive Summary
Lead (Pb) and copper (Cu) are hazardous pollutants due to their toxicity, persistence, and potential long-term effects on human health and marine ecosystems. Both metals are harmful at low concentrations, particularly in aquatic environments where they can accumulate in food webs. Lead is non-essential and highly toxic, affecting growth, reproduction, and behaviour, and can persist in sediments as a long-term contamination source. Copper, an essential trace element, becomes toxic at elevated concentrations, especially to early life stages of aquatic organisms, and sustained inputs can adversely impact marine ecosystems.
This report presents a model-based assessment of atmospheric inputs of Pb and Cu to the OSPAR maritime area, conducted by Meteorological Synthesizing Centre – East (MSC-E). The study evaluates long-term trends in emissions and deposition from 1990 to 2023, analyses source attribution for 2023, and evaluates modelling results against observations.
The assessment shows that Pb emissions in OSPAR countries decreased sharply by 96% between 1990 and 2023, largely due to the phase-out of leaded petrol. Over the same period, industrial sources became the dominant contributor to Pb emissions, while road transport declined significantly. In contrast, Cu emissions remained broadly stable, with road transport continuing to dominate, and industrial sources contributing significantly in some countries.
Atmospheric Pb deposition to all OSPAR regions declined substantially, with the largest reductions observed in areas closest to major emission sources, such as the Greater North Sea. Statistical analysis confirms a significant long-term decline, although the rate of decrease slowed after the early 2000s. Pb deposition was largely influenced by non-OSPAR and secondary sources, with OSPAR countries contributing between 2% and 29% in 2023. The United Kingdom was the largest contributor in most regions, while Spain, Portugal, and Russia dominated in specific regions.
By contrast, Cu deposition showed no consistent long-term decrease, with high interannual variability masking weak trends. Statistically significant declines were limited to a few regions and were small in magnitude. In 2023, OSPAR emissions accounted for 22-80% of Cu deposition, dominated by the United Kingdom, while secondary sources, including Saharan dust, influenced deposition in remote regions. Pb deposition was dominated by industrial sources and road transport, while Cu deposition was largely driven by road transport, with solvents usage and off-road emissions as secondary contributors. Other sectors contributed minimally.
Model evaluation indicates that the model reproduces Pb air concentrations and deposition reasonably well, with some overestimation in high-emission areas and minor underestimation in Northern Europe. Cu simulations show larger deviations from observations, reflecting higher uncertainty that likely arises from a combination of factors, including emission estimates, model representation, and variability in measurement data.