Magazine article Science News

U.S. River Quality: Not All Signs Are Good

Magazine article Science News

U.S. River Quality: Not All Signs Are Good

Article excerpt

U.S. river quality: Not all signs are good

The first major long-term study ofwater quality in the nation's rivers shows some diverging trends. Though it reports that between 1974 and 1981 there were widespread decreases in contamination from fecal bacteria and inorganic lead, it also reports widespread increases in nitrate levels, river salinity and concentrations of the toxic metals arsenic and cadmium. What will make these increases especially difficult to manage, the water researchers say, is that they are largely linked to diffuse sources of pollution --ones not addressed by the Environmental Protection Agency's massive program for upgrading water quality through better sewage treatment.

The new study, reported in the March27 SCIENCE, quantifies trends for 24 different measures of water quality. It is based on data collected over seven and a half years by two nationwide sampling networks, which together surveyed more than 300 major U.S. river sites.

"Perhaps the foremost surprise,' sayshydrologist Richard A. Smith of the U.S. Geological Survey in Reston, Va., one of the study's authors, is the nitrate trend. Over the sampling period, there was about a 50 percent increase in nitrate concentrations at 116 sampling sites, he points out. The main factors contributing to this increase were fertilizer runoff and acid rain.

Nitrates contribute to the oxygen depletion--and eventual oxygen starvation --of coastal estuaries, Smith says; at levels higher than those measured in this study, they can be a human health hazard as well. …

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