[Confluence of the Ohio and Mississippi Rivers at Cairo, Ill. Note contrasting appearance between sediment-laden Ohio River and clearer Mississippi.]

Although the Mississippi River System drains water from 31 States and is the source of 23 percent of the public surface-water supplies for the United States, the Nation had not had a systematic water-quality study that covered the entire length of the Mississippi River prior to the USGS study that was begun in 1987. In conducting this study, USGS made use of new technology for representative sampling of large rivers, that it had developed in studies of the Amazon and Orinoco Rivers. Initially started to assess the water-quality of the Mississippi River System below St. Louis, including assessing the contributions from the Missouri and Ohio Rivers, the study was expanded in 1991 to cover the entire Mississippi River System. USGS scientists coordinated their activities with various from States along the Mississippi River, as well as with the U.S. Fish and Wildlife Service and the U.S. Army Corps of Engineers, and interacted with members of the Upper Mississippi River Basin Association, Upper Mississippi River Conservation Commission, and the Interstate Council on Water Policy

[USGS hydrologists from Missouri sampling Mississippi River near Grafton, Illinois.]

 Some of the findings of this study:

• Overall sewage contamination has decreased in Mississippi since the enactment of 1972 clean-water act.
  o Fecal coliform bacteria (from human and animal wastes) did not appear to be a problem at the Twin Cities, Minneapolis-St. Paul. However, coliform bacteria and LAS, a biodegradable detergent primarily derived from domestic sewage, were found in high concentrations in the St. Louis metropolitan area, probably reflecting incomplete wastewater treatment.
• There is an annual cycle of elevated pesticide concentrations in spring and early summer with lower concentrations at other times of year.
• Atrazine, the most commonly used herbicide, is nearly ubiquitous in the Mississippi River with concentrations usually greatest near St. Louis because of inputs from tributaries that drain cornbelt region.
• EDTA, a general indicator of industrial contamination, was only about 1/4 of the concentration found in some major European Rivers.
• ondustrial contaminants were traced to point sources.
• PCB's persist in Mississippi River sediments even though their disposal in the river was banned about 15 years before the study.

References: Meade, R.H., ed., 1995, Contaminants in the Mississippi River, 1987-92: U.S. Geological Survey Circular 1133, 140p.

For additional information and references, see former project, Sediment-Transported Pollutants in the Mississippi River , or contact Robert Meade, Jr,. rhmeade@usgs.gov or John Moody, jamoody@usgs.gov