Abstract
Carbon nanotubes (CNTs) are widely used in industry, but their environmental impacts on soil microbial communities are poorly known. In this paper, we compare the effect of both raw and acid treated or functionalized (fCNTs) multi-walled carbon nanotubes (MWCNTs) on soil bacterial communities, applying different concentrations of MWCNTs (0 µg/g, 50 µg/g, 500 µg/g and 5000 µg/g) to a soil microcosm system. Soil DNA was extracted at 0, 2 and 8 weeks and the V3 region of the 16S rRNA gene was PCR-amplified and sequenced using paired-end Illumina bar-coded sequencing. The results show that bacterial diversity was not affected by either type of MWCNT. However, overall soil bacterial community composition, as illustrated by NMDS, was affected only by fMWCNT at high concentrations. This effect, detectable at 2 weeks, remained equally strong by 8 weeks. In the case of fMWCNTs, overall changes in relative abundance of the dominant phyla were also found. The stronger effect of fMWCNTs could be explained by their intrinsically acidic nature, as the soil pH was lower at higher concentrations of fMWCNTs. Overall, this study suggests that fMWCNTs may at least temporarily alter microbial community composition on the timescale of at least weeks to months. It appears, by contrast, that raw MWCNTs do not affect soil microbial community composition.
Highlights
Carbon nanotubes (CNTs) are widely used in novel industrial materials because of their particular chemical and physical characteristics [1,2,3]
The characterization of multi-walled carbon nanotubes (MWCNTs) based on field-emission scanning electron microscopy (FE-SEM) (Fig. 1A) and Energy-Filtering transmission electron microscopy (EF-TEM) (Fig. 1B, 1C) images showed that the average diameter was around 13.4 nm and the number of walls was 11 in average
Raman spectrum showed that the D-band/G-band ratio was approximately 1.305 and this result showed that defects have been generated from pristine MWCNT which D-band/G-band ratio is 1.087 (Fig. 1D)
Summary
Carbon nanotubes (CNTs) are widely used in novel industrial materials because of their particular chemical and physical characteristics [1,2,3]. They are currently used for—or under development in—electron emission devices, energy storage devices, drug delivery mechanisms, and a range of other engineering applications [4,5,6,7,8,9]. Carbon nanotubes (CNTs) are single atom layers of hexagonal carbon rolled up into hollow cylinders. PLOS ONE | DOI:10.1371/journal.pone.0123042 March 31, 2015
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