The inevitable release of engineered silver nanoparticles (AgNPs) into aquatic environments has
drawn great concerns about its environmental toxicity and safety. Although aggregation and
transformation play crucial roles in the transport and toxicity of AgNPs, how the water chemistry
of environmental waters influences the aggregation and transformation of engineered AgNPs is
still not well understood. In this study, the aggregation of polyvinylpyrrolidone (PVP) coated
AgNPs was investigated in eight typical environmental water samples (with different ionic
strengths, hardness, and dissolved organic matter (DOM) concentrations) by using UV–visible
spectroscopy and dynamic light scattering. Raman spectroscopy was applied to probe the
interaction of DOM with the surface of AgNPs. Further, the photo-transformation and
morphology changes of AgNPs in environmental waters were studied by UV–visible
spectroscopy, inductively coupled plasma mass spectrometry, and transmission electron
microscopy. The results suggested that both electrolytes (especially Ca2+ and Mg2+) and DOM
in the surface waters are key parameters for AgNP aggregation, and sunlight could accelerate
the morphology change, aggregation, and further sedimentation of AgNPs. This water
chemistry controlled aggregation and photo-transformation should have significant environ-
mental impacts on the transport and toxicity of AgNPs in the aquatic environments.
© 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.