chloramines? The graduated pH test answers the first question and is 

 designed to indicate a pH-dependent toxicant such as un-ionized ammonia. 

 The second question is answered by performing the following tests at 

 different pHs: aeration, filtration and reverse-phase solid phase ex- 

 traction (SPE). Aeration tests determine whether toxicity is attributa- 

 ble to volatile or oxidizable compounds. The filtration tests indicate 

 whether toxicity is associated with filterable components. Reverse- 

 phase SPE indicates whether toxicity is attributable to non-polar com- 

 pounds. Presence of toxic cationic metals is indicated if addition of a 

 chelating agent, ethylenediaminetetraacetic acid (EDTA), diminishes 

 toxicity. Presence of chlorine or other oxidizing agents is indicated 

 by a reduction in toxicity following addition of the reducing agent, 

 sodium thiosulfate. 



3.5.2 Phase II uses chemical fractionation techniques in parallel with 

 toxicity tests to isolate suspected toxicants (Mount and Anderson-Carna- 

 han 1989). Our Phase I results strongly implicated ammonia as a toxi- 

 cant, so we retested the samples after selectively removing ammonia 

 using a zeolite ion exchange resin, following the methods of Mount and 

 Anderson-Canaragan (1989), Ankley et al . (1990), and Schubauer-Berigan 

 and Ankley (1991). Zeolites are naturally-occurring or synthetically- 

 created crystalline hydrated alkali -aluminum silicates. A column was 

 prepared by packing a glass tube with a commercially available zeolite 

 product. The sample was passed over the zeolite column using a metering 

 pump, at a flow rate of approximately 10 ml/min (milliliters per minute). 

 Post column samples were analyzed for total ammonia and screened for 

 acute toxicity. 



21 



