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<br />12 <br /> <br />Recently, development of special tech- <br />niques for use in bioassays has allowed for <br />some discrimination as to the cause of <br />toxicity. TIE (toxicity identification <br />evaluation) procedures are used to identify <br />the chemical characteristics of the toxicant. <br />These procedures are especially useful in <br />situations where many potential toxicants <br />may be present. By performing a TIE, <br />the chemical that is causing the observed <br /> <br />toxicity can be characterized and separated <br />from the confusing background chemical <br />matrix. <br /> <br />Biosurveys <br /> <br />Reclamation studies on the Arkansas <br />River have demonstrated the effective use <br />of biosurveys for detecting impairment. <br />Heavy metals associated with historical <br /> <br />'1 <br /> <br /> <br />,. ~.:. <br /> <br /> <br />" <br />~,;::;~ . I - "';:~""a':.. <br />~ '..: "". ,....~.. <br /> <br /> <br />'~~ <br /> <br />Durin!J a biosurvey, aquatic organisms are collected In the field using a <br />variety of nets and other sampling gear. <br /> <br />Elioassays are performed using various dilutions of the toxicant or test <br />\IIater to determine the point at which there Is an effect or mortality to <br />50 percent of the test organisms. <br /> <br />\".. <br /> <br /> <br />.... . <br /> <br /> <br />-, <br /> <br />~ <br /> <br />---- ----=---.................. <br /> <br /> <br />~~~ <br /> <br />~ <br />