Response of soil microorganisms to the introduction of nanoscale carbon materials
Abstract
Carbon-based nanomaterials are finding their way into many product applications and the release of nanomaterials into the environment is inevitable. An early assessment of their potential environmental impacts, prior to environmental release, is warranted. This work focuses on an assessment of the impacts of fullerene (C60) and single-wall carbon nanotubes (SWNTs) on soil microbial processes, considered to be a sensitive indicator of the potential for environmental stress. A series of the most currently encountered nanomaterials including fullerene C60 or its aqueous suspension (nC60) and single-wall carbon nanotubes (SWNTs), in their raw manufactured form or with functionalization were introduced to two soils with high or low organic matter contents. Impacts of the applications were evaluated by measuring soil basal respiration, glucose-induced respiration, total microbial biomass (indicated by phospholipid derived phosphate), or soil enzymatic activities including β-glucosidase, acid-phosphatase, dehydrogenase and urease. Community structure was evaluated using fatty acid profiles or denaturing gradient gel electrophoresis (DGGE) of 16S and 18S rDNA fragments amplified by PCR from soil DNA extracts. Our observations show that C60, introduced in dry form or as aqueous suspension, have limited impact on the structure and activity of the soil microbial community. SWNTs have some effects on microbial community structures but they did not exert a major effect on the activities. The response of soil microorganisms was not affect by C60 introduced in organic solvent (toluene or tetrahydrofuran). However the high concentration of solvent showed negative effects on the microbial activity and changed the bacterial community composition. In addition, the acute toxicity of SWNTs and viability of bioluminescent E. coli O157:H7 in contact with SWNTs was examined. As-produced SWNTs showed toxic effect on both bioluminescence and viability of the cells. Functionalized SWNTs inhibited the number of viable cells but did not show acute toxicity. Our results from this work suggest that the soil organic matter may be a major factor affecting the bioavailability of the nanomaterials. Future research is needed concerning the interaction of organic matter and carbon nanomaterials in natural environment.
Degree
Ph.D.
Advisors
Turco, Purdue University.
Subject Area
Biogeochemistry|Soil sciences|Environmental science
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