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USGS2000

Effects of the flood of 1993 on the chemical characteristics of bed sediments in the Upper Mississippi River

Concentrations of pollutants stored in the surficial bed sediments in the navigation pools of the Upper Mississippi River showed a general decrease after the record flood of 1993. Percent clay and total organic carbon in the surficial sediments decreased as a result of an increase in the proportion of coarser sediment. Decreases in pollutant concentration may have been a result of the dilution by coarser and relatively less polluted sediment that was mobilized and transported into the Upper Mississippi River from its tributaries or from mainstem locations upstream but outside of the sampling area.

Water, Air, & Soil Pollution↗

USGS1992

Effects of the lampricide 3-trifluoromethyl-4-nitrophenol on dissolved oxygen in aquatic systems

The effects of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) on dissolved oxygen and other water- quality characteristics were evaluated in a series of test chambers under selected combinations of water, sediment, TFM, and exposure to sunlight. Concentrations of TFM gradually decreased over time, especially in the presence of sediment and sunlight. The lampricide did not directly cause a reduction in dissolved oxygen concentration, but appeared to inhibit photosynthetic production of oxygen during daylight. Dissolved oxygen concentrations were significantly reduced by the presence of TFM in chambers exposed to sunlight. Concentrations of total ammonia were significantly higher in chambers with sediment than in those without sediment. In chambers that contained river water and were exposed to sunlight, ammonia concentrations were low because of either oxidation by the elevated dissolved oxygen concentrations or the assimilation of nutrients by algae. The observed changes in dissolved oxygen and ammonia because of the presence of TFM were subtle, but statistically significant.

Technical Report↗