Potential
Mechanisms and Environmental Controls of
TiO<sub>2</sub> Nanoparticle Effects on Soil Bacterial Communities
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Abstract
It has been reported
that engineered nanoparticles (ENPs) alter soil bacterial communities,
but the underlying mechanisms and environmental controls of such effects
remain unknown. Besides direct toxicity, ENPs may indirectly affect
soil bacteria by changing soil water availability or other properties.
Alternatively, soil water or other environmental factors may mediate
ENP effects on soil bacterial communities. To test, we incubated nano-TiO<sub>2</sub>-amended soils across a range of water potentials for 288
days. Following incubation, the soil water characteristics, organic
matter, total carbon, total nitrogen, and respiration upon rewetting
(an indicator of bioavailable organic carbon) were measured. Bacterial
community shifts were characterized by terminal restriction fragment
length polymorphism (T-RFLP). The endpoint soil water holding had
been reported previously as not changing with this nano-TiO<sub>2</sub> amendment; herein, we also found that some selected soil properties
were unaffected by the treatments. However, we found that nano-TiO<sub>2</sub> altered the bacterial community composition and reduced diversity.
Nano-TiO<sub>2</sub>-induced community dissimilarities increased but
tended to approach a plateau when soils became drier. Taken together,
nano-TiO<sub>2</sub> effects on soil bacteria appear to be a result
of direct toxicity rather than indirectly through nano-TiO<sub>2</sub> affecting soil water and organic matter pools. However, such directs
effects of nano-TiO<sub>2</sub> on soil bacterial communities are
mediated by soil water