With the rapid development of nanotechnology, selenium nanoparticles (SeNPs) have been used in many fields especially in medical, nutritional and agricultural industries. Therefore, there is increasing concern for the SeNPs released into the environment. Due to their unique physical and chemical properties, nanoparticles (1-100 nm in diameter) as emerging contaminants may pose potential adverse impacts on the environment. However, little is known about the chemical behavior of SeNPs in soil-plant systems. In particular, the biological processes that control the transport and fate of SeNPs in the soil environment have not been well elucidated. We hypothesized that SeNPs could be bio-transformed by soil bacteria that are associated with Se-hyper-accumulator plant Stanleya pinnata. A series of laboratory experiments were conducted to determine the biotransformation and volatilization of SeNPs in the soil-plant system. The results showed that the amount of Se volatilized from the soil with S. pinnata during a 7-day experimental time period was not significantly (p>0.05) different from the soil with the plant removal, after the soils were treated with 3 mg/kg SeNPs (based on dry weight). The cumulative Se mass volatilized from the soil-roots compartment (88.643±10.618 μg/pot) was significantly (p<0.05) higher than from the shoots (0.214±0.086 μg/pot). These results demonstrated that soil microbes play an important role in the volatilization of SeNPs in the soil-S. pinnata system. The microbial volatilization of SeNPs by Pseudomonas fuscovaginae that was isolated from the rhizosphere soil of S. pinnata was Se concentration dependent. During a 24-hour time period the rates of Se volatilization from the cultural solutions treated with 1, 5, and 10 mg/L Se (SeNPs) were 140.9±11.3 ng/flask, 1056.2±188.4 ng/flask, and 1444.2 ±106.6 ng/flask, respectively. In comparing to selenate and bulk elemental Se, the amount of Se volatilized from SeNPs by P. fuscovaginae was significantly (p<0.05) lower than from selenate, but higher than bulk elemental Se. Further, the difference in SeNP size (e.g., 23 nm versus 127 nm) had no significant (p>0.05) effects on the Se volatilization process. Pseudomonas fuscovaginae also exhibited higher rates of Se volatilization from SeNPs than Salicornia bigelovii-associated soil bacterium Corynebacterium propinquum, but was similar with Cellulomonas cellasea that was isolated from the rhizosphere soil of Polypogon monspeliensis. This study demonstrated that SeNPs in the soil-plant system are partially bioavailable and bio-transformed into volatile Se compounds. Soil bacteria are critically important in controlling chemical behaviors of SeNPs in the environment. Different biological transformation processes determine the fate and environmental impacts of nanoscale elemental Se in the environment.
|Commitee:||Kitz, Dennis, Yoon, Kyong-sup|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 55/05M(E), Masters Abstracts International|
|Subjects:||Nanotechnology, Environmental science|
|Keywords:||Bioaccumulation, Selenium, Volatilization|
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