Stronger impacts of long-term relative to short-term exposure to carbon nanomaterials on soil bacterial communities.

Environmental impacts of carbon nanomaterials (CNMs) have been attracting increasing concerns in recent years. Knowledge on how short-term exposure to CNMs influences soil microbial communities is available. However, little is known about the possible difference in effects of long-term versus short-term exposure of CNMs on soil microbial communities. In this study, we systematically compared effects of fullerene (C), single-walled carbon nanotubes (SW), and graphene (GR) on soil bacterial communities over short (30 d) and long (360 d) term exposure durations. Our findings revealed that short-term exposure to all CNMs significantly increased the alpha diversity of soil bacterial communities. SW and GR exposure for 360 d relative to that for 30 d more significantly decreased their alpha diversity. Compared to short-term exposure, a long term exposure to CNMs more strongly altered the beta diversity of soil bacterial communities. LEfSe analysis showed that, GR relative to C and SW exposure more strongly altered soil bacterial community composition especially for long-term duration at various taxonomic levels; more taxa were also identified by LEfSe analysis as biomarkers upon long-term GR exposure. More OTUs were affected by long-term GR exposure. These differences resulted from both distinct physicochemical properties of various CNMs and their exposure durations.