A methodological approach to assess the release of metals from metallic- and electronic-wastes exposed to rainfall events in waste collection centers

• Metal leaching from metallic & electronic wastes exposed to rain was investigated. • Laboratory experiments were designed to support field survey results. • High data variability was observed due to intrinsic material differences. • Critical factors to improve waste management and reduce impacts were identified. • Metal leaching should be investigated throughout the entire rainfall event. The disposal of metallic (MW) and electronic (E-W) waste, if not properly accomplished, can lead to the release of toxic metals to soil and surface water, posing risks to environmental health. The extent of metal leaching depends on waste management practices, including storage conditions. Facing this issue, we developed a methodological approach combining field and laboratory investigations to support management strategies in collection centers where wastes are stored in open-top containers and thus exposed to rainfall. Specifically, leachate samples were collected after rainfall events at several centers and analysed. To account for variability observed in field conditions, a laboratory-scale experiment was also set up, with MW and EW exposed to simulated rainfall events, including a 15-minute first flush, followed by further 15 min, with waste immersion up to 14 days in water accumulated in the containers (later stage). Periodical leachate analysis revealed that, despite a higher release of certain metals from MW (up to 13.4, 10.9 and 47.9 mg/L for aluminium, iron, and zinc, respectively), E-W posed greater concern due to a significant release of hazardous metals such as cadmium, nickel and lead (up to 0.5, 0.3 and 1.7 mg/L, respectively). Different release patterns between waste types were observed, particularly during the first flush. Water accumulated during the later stage showed increasing or peak concentrations of hazardous metals, stressing the influence of prolonged immersion. These findings highlighted critical factors in waste management to mitigate environmental impact, including storage time and monitoring/treatment of the resulting wastewater before discharge into the environment.