title: Ammonium toxicity at high pH in a marine bioassay using Corophium volutator.
abstract: Two forms of ammonium exist in water: un-ionized ammonia NH3 and ionized ammonium NH4+. The toxicity to many aquatic organisms is primarily attributed to the NH3 (un-ionized) species, with the NH4+ ion (ionized) species being relatively less toxic. The pH level influences the degree of ionization. It is therefore very important that quality criteria be derived for total ammonium levels at several pH values in order to allow correct interpretation of the sediment bioassay with Corophium volutator. The responses of Corophium to total ammonium were studied in a series of pH-controlled experiments. The LC50 of total ammonium showed a significant decrease with increasing pH, in both water-only and sediment experiments. The results indicated a combined NH4+ and NH3 toxicity at pH levels less than 8.3. The results can be used to set pH-dependent water quality criteria for total ammonium in overlying water in a 10-day sediment bioassay with Corophium volutator.
authors.affiliation: National Institute for Coastal and Marine Management/RIKZ, PO Box 8039, 4330 EA, Middelburg, The Netherlands. b.j.kater@rikz.rwz.minvenw.nl
authors.forename: Belinda J
authors.initials: BJ
authors.lastname: Kater
authors.forename: Marco
authors.initials: M
authors.lastname: Dubbeldam
authors.forename: Jaap F
authors.initials: JF
authors.lastname: Postma
mesh_terms: D033304:Amphipoda / Q000187:drug effects*; D000818:Animals; D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007928:Lethal Dose 50; D000644:Quaternary Ammonium Compounds / Q000633:toxicity*; D012621:Seasons; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical