Long-Term Effects of Multiwalled Carbon Nanotubes and Graphene on Microbial Communities in Dry Soil

Abstract

Little is known about the long-term effects of engineered carbonaceous nanomaterials (ECNMs) on soil microbial communities, especially when compared to possible effects of natural or industrial carbonaceous materials. To address these issues, we exposed dry grassland soil for 1 year to 1 mg g–1 of either natural nanostructured material (biochar), industrial carbon black, three types of multiwalled carbon nanotubes (MWCNTs), or graphene. Soil microbial biomass was assessed by substrate induced respiration and by extractable DNA. Bacterial and fungal communities were examined by terminal restriction fragment length polymorphism (T-RFLP). Microbial activity was assessed by soil basal respiration. At day 0, there was no treatment effect on soil DNA or T-RFLP profiles, indicating negligible interference between the amended materials and the methods for DNA extraction, quantification, and community analysis. After a 1-year exposure, compared to the no amendment control, some treatments reduced soil DNA (e.g., biochar, all three MWCNT types, and graphene; P < 0.05) and altered bacterial communities (e.g., biochar, carbon black, narrow MWCNTs, and graphene); however, there were no significant differences across the amended treatments. These findings suggest that ECNMs may moderately affect dry soil microbial communities but that the effects are similar to those from natural and industrial carbonaceous materials, even after 1-year exposure.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects—An updated review

“…However, the masses of carbon NMs entering WWTPs are relatively low, and, unlike Ag NMs, evidence suggests that carbon NMs are only likely to be toxic at relatively high concentrations (Nyberg et al 2008;Garner et al 2015). Although some studies have reported toxicity at high concentrations in hydroponics (Canas et al 2009;Hawthorne et al 2012) and in vitro (Jia et al 2005), the small amount of ecotoxicological work that has taken place in soilbased media has reported little toxicity to soil organisms (Nyberg et al 2008;Ge et al 2016). Such research includes studies reporting low bioavailability of CNTs to earthworms in both artificial and natural soils (Petersen et al 2008a(Petersen et al , 2008b(Petersen et al , 2011, and studies indicating that fullerenes have no impact on soil microbial communities (Tong et al 2007;Nyberg et al 2008).…”

“…Such research includes studies reporting low bioavailability of CNTs to earthworms in both artificial and natural soils (Petersen et al 2008a(Petersen et al , 2008b(Petersen et al , 2011, and studies indicating that fullerenes have no impact on soil microbial communities (Tong et al 2007;Nyberg et al 2008). Newer carbon-based NMs like graphene, for example, have to date received little study but also appear to have relatively low toxicity (Ge et al 2016).…”

Ectomycorrhizal fungi inoculation alleviates simulated acid rain effects on soil ammonia oxidizers and denitrifiers in Masson pine forest

“…The relative abundance of individual T-RF was calculated as the peak area percentage of a specific T-RF in the whole T-RFLP profile. Only those T-RFs with a relative abundance >1% and fragment lengths in the range of 50-500 bp were considered in the further analysis (Ge et al, 2016).…”

Carbon nanotubes: Impacts and behaviour in the terrestrial ecosystem - A review

“…Interestingly, Shan et al [76] found that MWCNTs at low concentration (0.2 mg/kg) stimulated mineralization of an agricultural soil by bacteria. Ge et al [74] made an interesting work about effects of MWCNTs compared to natural or industrial carbonaceous materials on soil microbial communities using long-term studies in dry soil. They found that MWCNTs reduced soil DNA diversity and altered bacterial communities after one year of exposure.…”