Lead pollution 

Much of my research is focused on lead pollution. No safe level of lead exposure has been identified. Even low levels of lead in blood have been shown to negatively affect a child’s IQ, ability to pay attention, and performance in school. Lead is a top risk factor for premature death in the USA, particularly from cardiovascular disease. My work includes spatial studies of modern and persistent legacy lead sources in urban centers and temporal studies examining historical trends of lead pollution.

In spatial studies, I seek to identify distributions of lead that can be used to reduce human exposures. The legacy of leaded gasoline persists despite phasing out its use decades ago. Modern lead sources in our cities are under appreciated. This includes the release of lead from relic lead-sheathed telecommunication cables in our older cities and emissions from the permitted use of leaded gasoline in general aviation aircrafts and in racing vehicles.

In temporal studies, I seek to construct a global record of lead emissions that spans the history of human input using ice and lake sediment records. This work identifies human activities (e.g., rise and fall of civilizations, war, plagues, industrialization) that have perturbed the natural distribution of lead locally, regionally, and globally.

Examples of past projects:

Tracing of smelting emissions using cadmium, zinc, and lead isotopes

This research uses a combination of cadmium, zinc, and lead isotopes to trace the impact of smelting emissions. We have demonstrated that cadmium and zinc isotopes are fractionated during metallurgical processes and that they have the potential to trace their distributions in the environment. In contrast, lead isotopes are used to identify the ores, with unique radiogenic signatures, processed by the smelter.

Development of uranium isotope fractionation as an indicator of uranium immobilization by U(VI) reduction to U(IV)


This research investigates the use of uranium isotopic composition as a tool for evaluating U(VI) reduction to U(IV) by measuring the 238U/235U of groundwaters from a uranium contaminated aquifer at a former uranium mill site in Rifle, CO. We have demonstrated that significant uranium isotopic fractionation accompanies U(VI) reduction during bioremediation and thus, that uranium isotopes provide a powerful tool for quantifying the extent of U(VI) reduction to U(IV) and thus, immobilization.

Tracing cadmium, zinc and lead sources in oysters and mussels from Canada, the USA and France


In contrast to efforts focused on the use of metal concentrations, which are limited in their ability to assess metal sources, I used cadmium, zinc and lead isotope ratios to trace the source of these metals in bivalve tissues. I used this technique to determine that despite relatively high cadmium levels in British Columbian bivalves, Cd in their tissues is primarily natural, likely originating from the upwelling of nutrient-rich (and cadmium-rich) waters along that coast. In contrast, I identified cadmium in bivalves from France and the USA East Coast as primarily anthropogenic.

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Environmental and Isotope Geochemistry