ABSTRACT
The main objective of this study was to find a cost-effective, efficient and environmentally-friendly solution to remove perfluorooctanic acid (PFOA) from groundwater by using Fe0 and MnO2 nanoparticles. The selected method was expected to be applicable to the remediation of PFOA-contaminated groundwater. Phytotoxicity of the nanoparticle treatment was studied to demonstrate the safe application of the nanomaterials. Zero-valent Fe (100 mg L-1) and MnO2 (100 mg L-1) nanoparticles, produced in our lab, were used to remove PFOA up to 10 mg L-1. The test was conducted under visible light with or without addition of 0.88 mol L-1 H2O2 in a pH range of 0.5-11.0 for a duration of 18 h. Using Fe nanoparticles, a higher percentage of PFOA was removed under extreme acidic environment of pH 0.5 than under the basic environment of pH 11.0, and a minimum removal rate was reached under the neutral environment. The Fe nanoparticles were more efficient than the MnO2 nanoparticles at pH 0.5 with a removal rate of 69.7% and 89.7% without and with H2O2 addition, respectively. Phytotoxicity study showed that the treatment by Fe nanoparticles under mild pH reduced the phytotoxicity of groundwater-associated PFOA to Arabidopsis thaliana. The Fe nanoparticles did not show negative effect to A. thaliana under the experimental conditions used in this study.
Subject(s)
Caprylates/analysis , Environmental Restoration and Remediation/methods , Fluorocarbons/analysis , Groundwater/chemistry , Iron/chemistry , Light , Manganese Compounds/chemistry , Nanoparticles/chemistry , Oxides/chemistry , Water Pollutants, Chemical/analysis , Arabidopsis/drug effects , Caprylates/radiation effects , Fluorocarbons/radiation effects , Hydrogen Peroxide/chemistry , Hydrogen-Ion Concentration , Iron/toxicity , Nanoparticles/toxicity , Oxides/toxicity , Water Pollutants, Chemical/radiation effectsABSTRACT
A new method for path transverse wind velocity survey was introduced by analyzing time lagged covariance function of different separation sub-apertures of Hartmann wavefront sensor. A theoretical formula was logically deduced for the light propagation path transverse wind velocity profile. According to the difference of path weighting function for different sub apertures spacing, how to select reasonable path weighting functions was analyzed. Using a Hartmann wavefront sensor, the experiment for measuring path transverse velocity profile along 1 000 m horizontal propagating path was carried out for the first time to our knowledge. The experiment results were as follows. Path transverse averaged velocity from sensor had a good consistency with transverse velocity from the wind anemometer sited near the path receiving end. As the path was divided into two sections, the path transverse velocity of the first section had also a good consistency with that of the second one. Because of different specific underlaying surface of light path, the former was greater than the later over all experiment period. The averaged values were 1.273 and 0.952 m x s(-1) respectively. The path transverse velocity of second section and path transverse averaged velocity had the same trend of decrease and increase with time. The correlation coefficients reached 0.86.
