Seasonal alterations of landfill leachate composition and toxic potency in semi-arid regions

► Seasonal changes of leachate parameters are related with the amount of rainfall. ► Weather conditions mediate the landfill age and leachate strength and toxicity. ► Leachate parameters show high values in dry seasons. ► Leachate toxicity in different species tested is increased during dry seasons. ► The BOD5/NH4-N ratio could be related with the leachate strength and toxicity.