A significant fraction of engineered nanoparticles (ENPs) entering wastewater treatment plants is likely to be removed with settled sludge. This sludge may be disposed as biosolids in landfills or applied on agricultural land. Therefore, fate of pristine and transformed/aged ENPs in biosolids needs to be urgently investigated. The goal of this study is to quantify the fraction of ENPs that may detach from biosolids and further enter into the environment and food chain.To overcome the challenge of ENP detection at parts per billion levels in complex matrices, we identified single-particle mode inductively coupled plasma mass spectrometry (SP-ICP-MS) as a suitable analytical technique to quantify and characterize ENPs detached from biosolids. Target ENPs included AgNPs, TiO2NPs, CuNPs and ZnNPs. The presence of ENPs in biosolid samples was also confirmed with transmission electron microscopy.Municipal wastewater biosolids samples were collected, flash-frozen in liquid nitrogen and stored at -80�C before analyses. After resuspension of thawed biosolids in fresh media (DI water or buffer solutions), samples were mixed and/or sonicated representing a range of mixing conditions. After biosolids sedimentation, analysis of ENPs in the supernatant was performed by SP-ICP-MS. The total metal content after acid digestion was assessed for mass balance. SP-ICP-MS analysis was optimized and validated by performing control experiments with biosolids spiked with standard ENPs (e.g. 80 nm AgNPs). In both unspiked and spiked biosolids, ENPs were detected in the supernatant, confirming the detachment of ENPs from biosolids after resuspension in aqueous media. Data from ongoing experiments on SP-ICP-MS characterization of the amounts of dissolved and organic molecule-metal complexes present in the supernatant will also be presented. Implication of these results for environmental risk assessment and regulation will be also discussed.

Detection of engineered nanoparticles in municipal wastewater biosolids by SP-ICP-MS

248th National Meeting (2014)

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