Word: sediment
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...steep to walk on have been scraped to bare earth. Acreage bulldozed for shopping malls looks like this. Until these ravaged uplands reseed themselves -- which on the steepest slopes simply may not happen -- erosion is inevitable, and the most reliable yield, says Forester Morrison in disgust, will be "sustained sediment" in the streams that drain them. We head eastward to a landing field near Mount Rainier National Park...
...five years, at 200 locations around the U.S., the National Oceanic and Atmospheric Administration has been studying mussels, oysters and bottom- dwelling fish, like flounder, that feed on the pollutant-rich sediment. These creatures, like canaries placed in a coal mine to detect toxic gases, serve as reliable indicators of the presence of some 50 contaminants. The news is not good. Coastal areas with dense populations and a long history of industrial discharge show the highest levels of pollution. Among the worst, according to Charles Ehler of NOAA: Boston Harbor, the Hudson River-Raritan estuary on the New Jersey coast...
...except in a few scattered communities, has a fairly low political priority. One reason: most people assume that the vast oceans, which cover more than 70% of the world's surface, have an inexhaustible capacity to neutralize contaminants, by either absorbing them or letting them settle harmlessly to the sediment miles below the surface. "People think 'Out of sight, out of mind,' " says Richard Curry, an oceanographer at Florida's Biscayne National Park. The popular assumption that oceans will in effect heal themselves may carry some truth, but scientists warn that this is simply not known. Says Marine Scientist Herbert...
...number of ways. Dredging can stir up the bottom, throwing pollutants back into circulation. The U.S. Navy plans to build a port in Puget Sound for the aircraft carrier U.S.S. Nimitz and twelve other ships; the project will require displacement of more than 1 million cu. yds. of sediment, with unknown ecological consequences. Similarly, natural events such as hurricanes can bestir pollutants from the sediment. The estuarine environment also changes when the balance of freshwater and salt water is disturbed. Upstream dams, for example, diminish the flow of freshwater into estuaries; so do droughts. On the other hand, rainstorms...
Buried toxins can also be moved around by shrimp and other creatures that dig into the bottom and spread the substances through digestion and excretion. Though ocean sediment generally accumulates at a rate of about one-half inch - per thousand years, Biogeochemist John Farrington of the University of Massachusetts at Boston cites discoveries of plutonium from thermonuclear test blasts in the 1950s and 1960s located 12 in. to 20 in. deep in ocean sediment. Thus contaminants can conceivably lie undisturbed in the oceans indefinitely -- or resurface at any time...