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* 18 Water Quality in the Great Salt Lake Basins, Utah, Idaho, and Wyoming, 1998- 2001 in Farmington Bay sediments. Thus, recent declines in lead concentration in sediments of Farmington Bay probably are mostly due to reduced lead in automobile emissions. Recent declines in lead concentration in sediment have been noted elsewhere and usually are attributed to reduction in lead emissions following passage of the Clean Air Act of 1970 ( Callender and Van Metre, 1997). DDT, PCBs, and other organo- chlorine compounds occur more commonly in fish than in sediment in area streams Twenty- seven organochlorine compounds were analyzed in streambed sediment and fish tissues at 15 sites. Twelve compounds were detected in fish tissue, whereas only 6 of the compounds were detected in sediment. All of the compounds detected in the sediment were also detected in tissue at each site ( fig. 30). These data illustrate the tendency for these compounds to accumulate in fatty tissue. an ' , nn' « J 11 i i c- i Total Chlordane '•• Total PCB I Jordan River Basin ffl • r i"" ' Weber River Basin : Bear River Basin Sediment ( dry weight) • • 3 Fish i ( wet weight) i i i 300 200 100 0 100 200 300 400 MICROGRAMS PER KILOGRAM Figure 30. Organic compounds were detected more frequently in fish tissue than in sediment. Trends in DDT, PCBs, and chlordane in Farmington Bay sediment are different from those at other sites nationally As a part of the NAWQA Program, trends in poly chlorinated biphenyls ( PCBs) and organochlorine compounds were tracked over the last several decades to the mid- to- late 1990s in sediment cores from 10 lakes and reservoirs in 6 U. S. metropolitan areas ( Van Metre and others, 2000). Nationally, total DDT concentration generally followed the historical use of DDT ( an organochlorine insecticide) in the United States, which peaked from the 1950s to the mid- 1970s and then declined substantially. DDT use was discontinued in the United States in 1972; however, in Farmington Bay, which receives inflow from the Jordan River after it flows through the metropolitan area of Salt Lake City, the concentration was still increasing in the mid- 1990s. Similarly, total PCB concentrations increased substantially between 1950 and 1965, coinciding with peak production, but concentrations in Farmington Bay sediment have not declined as at other sites nationally. Chlordane concentrations in Farmington Bay sediment began increasing significantly after 1950 and were still increasing in 1995, even though chlordane was discontinued from general use in the 1970s. The reasons for the continued trend of increasing concentrations of DDT, PCBs, and chlordane in the sediment cores from Farmington Bay are not understood at this time and will require further investigation. The relatively low concentrations in the sediments of streams in the Study Unit suggest that the concentrations should decrease in the bay with times. Farmington Bay sediment cores 20 15 | 10 a _ i 5 I I I I I ' • Total DDT • - - • - • - •, , I I i i 70 60 50 40 30 20 10 0 1930 1940 1950 1960 1970 1980 1990 2000 I I Chlordane I I I I • - - • - - • - ' •. t i i i 1 Two commonly detected compounds were PCBs and DDT, although the use of these compounds was discontinued in the United States in the 1970s. In 1998, PCBs were detected in whole- fish samples from 8 of 15 sites, and DDT breakdown products were detected at 13 of 15 sites. PCBs were detected in bed- sediment samples at only 2 of 15 sites, and DDT compounds were detected at 4 of 15 sites. In general, concentrations of organic compounds in fish tissue and sediment from the Study Unit were lower than those in other areas studied as part of the NAWQA Program. The concentrations of DDT compounds in sediment were between the threshold effect level ( TEL) 1 and probable effect level ( PEL) for aquatic life at three sites. Concentrations between the TEL and PEL indicate possible ' Currently there are no U. S. standards for assessing the potential for adverse biological effects due to contaminated freshwater sediment. The Canadian Council of Ministers of the Environment ( CCME) modified an approach by Long and Morgan ( 1991) to develop guidelines for marine and freshwater sediment. The CCME modified approach uses two assessment levels: ( 1) the threshold effect level ( TEL), representing the concentration below which adverse effects are expected to occur rarely, and ( 2) the probable effect level ( PEL), representing the concentration above which adverse effects are expected to occur frequently ( Ecosystem Conservation Directorate Evaluation and Interpretation Branch, 1995). |
