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Diagnosis of Toxic Effects <br />When the initial field inspection is completed and <br />the probable cause is believed to be a toxic sub- <br />stance or substances, the next step is to establish <br />whether the suspect chemical was present in suffi- <br />cient quantity to be toxic to fish. A complete water <br />chemistry analysis should help rule out other pos- <br />sible causes and help identify any contributing fac- <br />tors (e.g., dissolved oxygen, pH) that could influence <br />the toxicity of the suspected chemical agents. <br />Analyses that should always be run as soon as pos- <br />sible are listed below (in approximate order of im- <br />portance) as Priority I. Other desirable, useful <br />analyses that should be run when possible are listed <br />as Priority II. <br />Changes in pH caused by the discharge of <br />contaminants can drastically alter the <br />availability or activity of toxic substances. <br />Standardized equipment, such as this digi- <br />tal pH meter, promptly provides accurate <br />data. <br />TOXIC SUBSTANCES <br />Routine Water Chemistry Analyses <br />Priority I Priority II <br />Dissolved oxygen Biological oxygen <br />pH demand <br />Temperature Calcium <br />Ammonia, nitrogen Total organic <br />Alkalinity carbon <br />Color Chlorine <br />Conductivity Chemical oxygen <br />Nitrite nitrogen demand <br />Nitrate nitrogen Hardness <br />Total suspended Iron <br />solids Magnesium <br />Salinity Manganese <br />Sulfate Osmolality <br />Turbidity Phosphate <br />23