Sediment layers reveal a history of pollution

SEQUIM -- The history of a region can be told through faded photographs, old letters or yellowed news clippings. Eric Crecelius likes to tell the story of Puget Sound with mud.

It's all written on the seafloor.


	A five-part special report about the effects of pollution on the waters of Puget Sound. - Part 1: Polluted waters - Part 2: Extinction or bust - Part 3: Ruinous runoff - Part 4: Maritime mess - Part 5: Turning things around - Further developments - More stories - Join the forum Read the transcript of a live chat with reporters Robert McClure and Lisa Stiffler.

Scientists like Crecelius plunge coring devices into the bottom of the Sound and pull out plugs of dripping gray muck up to 8 feet long. Revealed in the sand and mud are trapped chemicals and metals -- telltale signposts dating back to the settlement of the basin by European immigrants.

Layers of sediments chronicle the rise and fall of smelters and paper mills, the proliferation of cars burning leaded gasoline, the dusting of fields with the insecticide DDT. Even the silver leached from photographic film-developing waste is imprinted.

The footprint of some toxins spans decades. It was worst from the 1950s to the '70s, when sea life was bombarded by everything from nuclear fallout to PCBs.

Much of that is concealed now, under a carpet of sediment. And tests show those top layers are much safer.

"Puget Sound is recovering," said Crecelius, of the government-funded Battelle Marine Sciences Laboratory here. "It's not back to pre-industrial contamination levels, but quite a bit of the area doesn't seem to be impacted by pollutants."

What is standing in the way of a happy ending to this story is urban growth and the pollution it generates -- and a new wave of contaminants that Crecelius isn't testing for yet.

From a research ship, a stainless-steel corer is driven into the sediments by massive weights. The layered sediment is sliced up and then chemically analyzed for metals, radioactive materials and other elements and compounds.

Because chemicals settle relatively quickly into sediment, samples can identify sources of pollution. They can reveal secret dumping and tell scientists about historical discharges, before monitoring started. Sediments concentrate contaminants, bringing attention to new pollutants. And they can suggest whether environmental regulations are working.

Like tree rings, each centimeter of sediment spans a year or so. The story told by a typical core sample begins in the late 1800s, with a rise in lead, mercury, silver and copper -- signs of increased industrial activity.

The samples included:

Synthetic compounds such as DDT and PCBs, the latter used as coolants and lubricants in electrical equipment, come into use in the 1930s. It would be decades before the government bans both.

In the '40s, as the number of coal-burning homes swells in Seattle and Tacoma, concentrations of airborne toxins called polycyclic aromatic hydrocarbons, or PAHs, also increase.

Cancer-causing dioxins from pulp mills first appear in the '60s and increase until 1989, when mills largely eliminate the chemical by shifting to cleaner processes.

Traces of plutonium in the seafloor, the result of global fallout, start in the early '50s and peak a decade later when the Nuclear Test Ban Treaty takes effect.

The most contaminated sediments are near the pollution source -- urban areas with lots of people, paved roads and manufacturing. The dirtiest areas also tend to be under shallow water or in river estuaries that churn the sediments and prevent the burial of pollutants.

The flow of many pollutants into the Sound is decreasing, as society recognizes the threat and regulates or eliminates their use. But serious concerns remain.

"It doesn't mean we're out of the woods," said Alan Mearns, a scientist with the National Oceanic and Atmospheric Administration in Seattle.

Copper, chromium, mercury, arsenic and PCBs are being buried, but burrowing organisms and dredging can revive them from their watery graves. And population growth threatens progress toward a cleaner Sound: More people means more damaging vehicle emissions, laundry detergent chemicals and tainted stormwater.

The future threat could come from "anything you buy in large quantities and take home and dump down the drains," said Crecelius, who is also studying the effects in fish of chemicals that mimic hormones, and how people and animals process arsenic. He's itching to get his hands on more mud and sand. His last samples from the Sound are years old.

"There could be some things changing the ecosystem, and we aren't even aware of it."

P-I reporter Lisa Stiffler can be reached at 206-448-8042 or lisastiffler@seattlepi.com

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