Skip to main content
U.S. flag

An official website of the United States government

Going Above and Beyond

Submitted by Pixie Hamilton, USGS, October 2005

A strong indicator of leadership is taking people to a level beyond that which they may achieve themselves. In addition, integral to our USGS mission, exemplary leadership is taking science beyond that which might be expected, as indicated, for example, by other studies or research. Peter Van Metre and Barbara Mahler, research hydrologists at the Texas Water Science Center , continue to demonstrate scientific excellence and leadership through their inquiring and innovative research. These two scientists currently study polycyclic aromatic hydrocarbons (or PAHs), which are a group of organic contaminants that form from the incomplete combustion of hydrocarbons, such as coal. These contaminants are commonly found in sediment in urban surface water bodies, such as streams, lakes and reservoirs, and are potentially toxic to mammals (including humans), birds, fish, amphibians, invertebrates, and plants.

In the past, sources of PAHs in urban watersheds have been primarily reported to be dominated by vehicular exhaust, leaking motor oil, tire wear, and atmospheric deposition. However, recent work initiated by Van Metre and Mahler suggests that a major important source is abraded sealcoat from parking lots. Specifically, vehicle tires abrade parking lot sealcoat into small pieces, and these small particles are washed off parking lots by rain into storm sewers and streams. Sealcoat is used commercially and by homeowners across the Nation. It commonly is applied to parking lots associated with commercial businesses (including strip malls and shopping centers); apartment and condominium complexes; churches, schools, and business parks; and on residential driveways.

To pursue their research ideas, Van Metre and Mahler initiated and developed a study with the City of Austin and sampled wash-off from 13 parking lots representing a range of different sealant types. They also took scrapings of different parking lot surface types to compare the source material with wash-off particulates. Concentrations and yields (the amount of PAHs coming off each lot) were used to determine levels of contamination in runoff from each type of lot and the importance of sealed lots as a source of PAHs to urban streams.

Peter Van Metre and Barbara Mahler, along with the City of Austin, may have discovered a major source of these contaminants, sealed parking lots. Findings from this study will undoubtedly influence management strategies for controlling PAHs in urban environments, not only in the City of Austin, but in urban areas throughout the Nation. Van Metre and Mahler have demonstrated that they are leaders who go "above and beyond."


« Back to Leadership Stories