SEQUIM, WA The slow natural restoration of hazardous sediments mired beneath the Puget Sound is progressing, thanks to Mother Nature and a stiff dose of federal environmental regulations.
But, researchers at the Department of Energy's Pacific Northwest National Laboratory warn that this recovery process may take 10 to 30 years longer than first predicted, because of increased urban growth and its associated untreated runoff.
"An analysis of sediment core samples retrieved over several decades provides us with empirical evidence that environmental regulations have had a positive impact on the overall water quality of the Puget Sound," said PNNL marine chemist and co-project lead Jill Brandenberger. She noted that some pollutants have returned to pre-industrial concentration levels.
"Unfortunately, our data also suggest that although pollution coming from a specific source or location may be decreasing, non-point sources, such as storm water discharges, are becoming more significant," she said.
PNNL marine scientists, along with the Texas A&M University research team, documented the evidence from a centimeter-by-centimeter dissection of several Puget Sound sediment cores. A recent article in Environmental Science and Technology detailed their findings from data collected over more than 23 years.
The complex Puget Sound waterway connects the Seattle metropolitan area and neighboring communities of about four million residents with the Pacific Ocean.
Scientists collected and analyzed 10-foot-long sediment cores in 1982, 1991 and, most recently, 2005, from a location near Seattle and adjacent to Tacoma, Wash. This careful chemical analysis of the sediment layers provided a historical rap sheet of toxins including lead, arsenic and copper. Like the concentric rings of a tree, each centimeter of mud delicately displayed a historical biography of environmental conditions.
|Contact: Geoff Harvey|
DOE/Pacific Northwest National Laboratory