Constraining the Cycle of Natural and Anthropogenic Lead in the Ocean

Constraining the Cycle of Natural and Anthropogenic Lead in the Ocean

Over the past 150 years, human activities have led to an order of magnitude increase in the amount of lead (Pb) released to the environment, with the most prominent contribution coming from the combustion of leaded gasoline. About fifty years after the introduction of leaded gasoline in 1923, mounting evidence of the baleful health effects of Pb on humans led to regulations limiting its use. The effect of these efforts is already visible in the declining Pb concentrations of surface waters from the North Atlantic Ocean. But in other regions, such as the Indian Ocean, the Pb content is still increasing, likely due to the delayed phase-out of leaded gasoline in developing countries, and increasing Pb contributions from other industrial activities such as coal burning, mining and smelting. The changing nature of Pb pollution sources through time provides a unique opportunity to study the dispersion of Pb and other heavy metal pollutants in the environment. This is because industrial activities produce Pb emissions with a distinct chemical signature, which can be used to track the evolution of the various Pb sources in the environment, and also distinguish it from natural Pb. This “fingerprint” is carried by winds and deposited over the ocean, whereupon it can be tracked as it propagates into the ocean interior by circulation and scavenging onto biogenic particles. The goal of this project is to put these ideas into practice by developing a global ocean model that simulates the transport and marine cycling of Pb. The model will be coupled to the Met Office Unified Model, which can simulate the emission, transport and deposition of a variety of aerosols. Once constrained by data, the model will be used to investigate the reactivity and biogeochemical cycling of metals and pollutants in the ocean and, ultimately, evaluate the environmental impact of major industrial activities.