It is not known which contaminants cause the toxic response in
H. incongruens. There is still not an extensive database for different
chemicals available.However,the test organism should be able to
tolerate the high levels of chloride and ammonia commonly found
in landfill leachate(Kjeldsen etal.,2002; Öman andJunestedt,
2008; Waara,2013) according to previous sediment spiking
experiments in our laboratory(WaaraandRibéunpubl.).It is
therefore likely that one or several other pollutants within the
sediment are responsible for the toxic response observed.