April 13, 2009

Study focuses on sealcoating runoff

A U.S. study suggests the significant increase in polyaromatic hydrocarbons entering waterways might come from driveway and parking lot sealcoats.

University of New Hampshire scientists said polyaromatic hydrocarbons, more commonly known as PAHs, are found in diesel and crude oil and are considered to be carcinogenic.

Our society has been sealcoating pavement for decades and there are things we've never asked about, said Associate Professor Tom Ballestero. Now we're starting to probe and ask these questions.

Although intended to remain on the pavement surface, much of the sealcoat eventually ends up in nearby streams and rivers, said researcher Alison Watts. She said the PAHs from the sealcoat attach to organic matter, such as leaves or sediment, where they may be ingested by organisms or buried in other sediments.

The university's Stormwater Center researchers covered one-quarter acre of a campus parking lot with coal tar-based sealcoat and one-third acre with asphalt-based sealcoat. The remainder of the nine-acre lot was left unsealed. On-site storm water drains off the parking lot and into a nearby swale.

The researchers said both types of sealcoat led to a surprisingly rapid increase in PAH concentrations in the initial runoff -- up to 5,000 parts per billion -- significantly higher than the 10 ppb levels released from the unsealed lot.

The UNH Stormwater Center is partially funded by the National Oceanic and Atmospheric Administration.