title: Effect of water hardness on the toxicity of cobalt and nickel to a freshwater fish, Capoeta fusca.
abstract: OBJECTIVE
  To determine the effects of water hardness on the toxicities of cobalt (Co) and nickel (Ni) to a freshwater fish, Capoeta fusca.
  
  
  METHODS
  Toxicity was investigated by static bioassay. Fish were exposed to cobalt (as CoCl(2)) and nickel (as NiCl(2)) for 96 h in waters with two levels of hardness ("hard" and "very hard", nominally 130 mg/L and 350 mg/L as CaCO(3), respectively).
  
  
  RESULTS
  Water hardness had a significant effect on the acute toxicity of both elements. The 96 h LC(50) values for Co were 91.7 mg/L and 204.8 mg/L in hard and very hard waters, respectively, and for Ni the 96 h LC(50) values were 78.0 mg/L and 127.2 mg/L, respectively.
  
  
  CONCLUSIONS
  The fish were more sensitive to Co and Ni toxicity in hard water than in very hard water; very hard water protects C. fusca against the toxicity of Co and Ni.
authors.affiliation: Department of Environmental Sciences, Faculty of Agriculture, University of Birjand, Birjand, Iran. Apourkhabbaz@yahoo.com
authors.forename: Alireza
authors.initials: A
authors.lastname: Pourkhabbaz
authors.forename: Tahereh
authors.initials: T
authors.lastname: Khazaei
authors.forename: Samira
authors.initials: S
authors.lastname: Behravesh
authors.forename: Mohammad
authors.initials: M
authors.lastname: Ebrahimpour
authors.forename: Hamidreza
authors.initials: H
authors.lastname: Pourkhabbaz
mesh_terms: D000818:Animals; D002119:Calcium Carbonate / Q000032:analysis*; D003035:Cobalt / Q000032:analysis / Q000633:toxicity*; D003530:Cyprinidae / Q000254:growth & development*; D004784:Environmental Monitoring; D005618:Fresh Water / Q000032:analysis*; D007492:Iran; D007928:Lethal Dose 50; D009532:Nickel / Q000032:analysis / Q000633:toxicity*; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D003035:Cobalt; C022838:nickel chloride; D009532:Nickel; C018021:cobaltous chloride; D002119:Calcium Carbonate