Occurrence of banned and commonly used pesticide residues in concentrated leachate: Implications for ecological risk assessment

Amounts of banned and current pesticides have been used in domestic and agricultural pest control, and their residues have accumulated along the waste stream. In this work, pesticides were characterized in concentrated leachates (CLs) from 5 municipal landfill sites, 2 incineration plants and 1 composting plant in six provinces. A total of 31 pesticides were detected which included 8 organochlorine pesticides (OCPs, 303-2974 ng/L), 16 organophosphorus pesticides (OPPs, 1380-13,274 ng/L) and 7 synthetic pyrethroids (SPs, 319-5636 ng/L). Despite the ten years ban of hexachlorocyclohexane, methamidophos and parathion-methyl, they were still in CL at a mean value of 320 ng/L and 88 ng/L, respectively. The average Σ₈OCPs, Σ₁₆OPPs and Σ₇SPs in CL from landfill sites were approximately 2.8, 1.1 and 4.5 times higher than those from incineration plants, which might have been influenced by pH, moisture and/or HRT. Additionally, it was found that CL from incineration plants and composting plant with lower pesticide contents posed a much higher acute and chronic eco-risk. Methamidophos was the dominant pesticide in CL from incineration plants, which was much higher than any other pesticides detected. The annual emissions of Σ₈OCPs, Σ₁₆OPPs and Σ₇SPs discharged from landfill-CL were estimated to be 2370, 10,357 and 2994 g, respectively. It was evident from the study that long-term release of CL after waste disposal could cause potential risk of ecological pollution.