-
[show abstract]
[hide abstract]
ABSTRACT: To elucidate the environmental fate of tetracycline (TC), we reported the light-source-dependent dual effects of humic acid (HA) and NO3(-) on TC photolysis. TC photolysis rate was highly pH- and concentration-dependent, and was especially enhanced at higher pH and lower initial TC concentrations. Under UV-254 and UV-365 irradiation, HA inhibited TC photolysis through competitive photoabsorption or reactive oxygen species (ROS) quenching with TC; under solar and xenon lamp irradiation, TC photolysis was enhanced at low HA concentration due to its photosensitization, whereas was suppressed at high HA concentration due to competitive photoabsorption or ROS quenching with TC. Similarly, the effect of NO3(-) on TC photolysis varied with light irradiation conditions. Even under the same light irradiation conditions, the effects of HA or NO3(-) on TC photolysis varied with their concentrations. The electron spin resonance spectrometer and ROS scavenger experiments demonstrated that TC photolysis was involved in O2(-)-mediated self-sensitized photolysis. The photolysis pathways were involved in hydroxylation and loss of some groups. More toxic intermediates than TC were generated under different light irradiation conditions. These results can provide insight into the potential fate and transformation of TC in surficial waters.
Chemosphere 04/2013; · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Perfluorooctanesulfonate (PFOS) is a typical persistent organic pollutant of more environmental concerns in the recent years. The adsorption of PFOS on the single-walled carbon nanotube (SWCNT) is studied with molecular dynamics (MD) simulation. The energy and conformational features are investigated via the statistical results from the MD trajectory. The size effect is observed from the adsorption of PFOS both on the inner and the outer surface. The non-bond interaction energy between PFOS and the inner surface of SWCNT is highly related to the diameter of nanotube. The conformation of PFOS is also changed by the sorbent surface. The PFOS molecule adsorbed on the outer surface is affected by the size of SWCNT more gently than that adsorbed in the nanotube. The aliphatic chain contributes most to the adsorption, as it locates more closely to the outer surface than the charged sulfuric group.
Chemosphere 02/2013; · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The remediation of polycyclic aromatic hydrocarbons (PAHs) polluted waters has become a concern as a result of the widespread use of PAHs and their adverse impacts on water ecosystems and human health. To remove PAHs rapidly and efficiently in situ, an active fibrous membrane, laccase-loading spider-type reactor (LSTR) was fabricated by electrospinning a poly(d,l-lactide-co-glycolide) (PDLGA)/laccase emulsion. The LSTR is composed of beads-in-string structural core-shell fibers, with active laccase encapsulated inside the beads and nanoscale pores on the surface of the beads. This structure can load more laccase and retains higher activity than do linear structural core-shell fibers. The LSTR achieves the efficient removal/degradation of PAHs in water, which is attributed to not only the protection of the laccase activity by the core-shell structure but also the pre-concentration (adsorption) of PAHs on the surface of the LSTR and the concentration of laccase in the beads. Moreover, the effects of pH, temperature and dissolved organic matter (DOM) concentration on the removal of PAHs by the LSTR, in comparison with that by free laccase, have been taken into account. A synergetic mechanism including adsorption, directional migration and degradation for PAH removal is proposed.
Journal of hazardous materials 01/2013; 248-249C:254-260. · 4.14 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Horseradish peroxidase (HRP) is successfully in situ encapsulated into the poly(d,l-lactide-co-glycolide) (PLGA)/PEO-PPO-PEO (F108) electrospun fibrous membranes (EFMs) by emulsion electrospinning. The adsorption and degradation of pentachlorophenol (PCP) by HRP-EFMs are investigated. The experimental results show that the sorption kinetic of PCP on EFMs follows the pseudo-second-order model, and the sorption capacity is as high as 44.69mgg(-1). The sorption mechanisms of EFMs for PCP can be explained by hydrogen bonding interactions, hydrophobic interactions and π-π bonding interactions. Profiting from the strong adsorption, the removal of PCP can be dramatically enhanced by the interaction of adsorbed PCP and HRP on the surface of EFMs. For PCP degradation, the optimal pH values for free HRP and immobilized HRP are 4 and 2-4, respectively. As pH>4.7, no adsorption and degradation are observed due to the deprotonation of PCP. The removal percentages reach 83% and 47% for immobilized HRP and free HRP, respectively, at 25±1°C. The presence of humic acid can inhibit the activity of HRP and decreases the adsorption capacity of PCP because of competitive adsorption. The operational and storage stability of immobilized HRP are highly improved through emulsion electrospinning.
Journal of hazardous materials 12/2012; 246-247C:119-125. · 4.14 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Historical profiles and sources of PAHs at two typical sediment cores (i.e., the shipping route site and the shoal site) were fully compared to probe the controlling factors, specifically the water currents, for the PAHs deposition processes in the Yangtze River Estuary. Compared with ocean water currents, river runoff affected by the water impoundment of the Three Gorges Dam greatly affected the PAHs levels and percent contribution of PAHs sources in the two cores. River runoff hindered the PAHs deposition in shoal site, while a contrary phenomenon was observed for the shipping route site. Though the PAHs in the estuary were mainly from river catchment, only low ring PAHs in the shipping route site were mainly from the upper reach of the river. Coarse sediments with higher organic carbon content also accounted for the higher deposition levels of PAHs in the shipping route site.
Chemosphere 11/2012; · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Density functional theory (DFT) plays a significant role in the development of visible light responsive photocatalysts. Based
on the first-principles plane-wave ultrasoft pseudopotential (USPP) method, the crystal structures of α, β, γ, and δ-Bi2O3 were optimally calculated for the total density of states (TDOS) and the partial density of states (PDOS) of Bi, O atoms.
The calculation for Ti(IV) doped Bi2O3 supercell was carried out. The effects of Ti(IV)-doping on the electron structures and light absorption properties of various
Bi2O3 were analyzed. The results showed that Ti 3d orbital appeared in the forbidden band of Bi2O3 and hybridized with O 2p, Bi 6p orbitals. The narrowed band gap (E
g) and red-shift of light absorption edge are responsible for the enhanced photocatalytic activity of Bi2O3. The β-Bi2O3 and Ti-doped β-Bi2O3 were prepared by a hydrothermal synthesis method. The improvement of the photocatalytic activity of Bi2O3 has also been verified by the characteristics of the UV-vis diffuse reflection spectrum and the experimental evaluation of
the photocatalytic degradation of crystal violet in aqueous solution.
KeywordsTi(IV) doping–Bi2O3
–electron structure–visible light photocatalytic activity–density functional theory
Science China-Chemistry 05/2012; 54(1):180-185. · 1.02 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The present study aims in investigating the individual and combined effects of ozone (O3) exposure and nitrogen (N) load on the growth and photosynthetic characters of Cinnamomum camphora seedlings, a dominant evergreen broadleaf tree species in sub-tropical regions. The seedlings were supplied with N as NH4NO3 solution at 0, 30 and 60kgha−1year−1 (simplified as N0, N30, N60, respectively) and were exposed to ambient O3 concentration (AA) or elevated [O3] (E-O3, AA +60ppb) for one growth season. E-O3 induced significant negative effects on foliar photosynthesis, including lower photosynthetic rate, reduced carboxylation
efficiency, quantum yield of PSII and photosynthetic pigment contents, despite no effect on growth. In contrast, N load acted
as fertilization effects. Medium N (N30) increased photosynthetic pigments and stem-base diameter growth relative to N0, whereas
high N load (N60) significantly enhanced the growth, photosynthetic pigments, and dark and light action of photosynthesis
of C. camphora seedlings. No significant interactive effects of O3 and N load on the growth, net photosynthetic rate and pigment contents of the seedlings were found, suggesting that N supply
to the soil at ≤60kgha−1year−1 does not significantly change the sensitivity of C. camphora to ozone.
Keywords
Cinnamomum camphora
–Ozone–N deposition–Chlorophyll fluorescence–Gas exchange–Growth
Trees 04/2012; 25(4):617-625. · 1.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The concentrations and depositional fluxes of polycyclic aromatic hydrocarbons (PAHs) were investigated in a dated sediment
core collected from Donghu Lake, central China. Total concentrations of 16 PAHs ranged from 33.32 to 937.24ng g−1 based on dry weight. Depositional fluxes of total PAHs, ranging 15.84–387.37ng cm−2 year−1, were in relatively higher levels compared with those in the cores collected from other areas of China. The concentrations
and fluxes of total and individual PAHs changed dramatically with depth, reflecting energy usage changes and closely following
the historical economic development in central China. Since the initiation of the “Reform and Opening-Up policy” in the late
1970s, the levels of PAHs, especially the high-molecular-weight carcinogenic PAHs, increased rapidly and reached the highest
value in recent years, indicating the growth of incomplete combustion of coal and petroleum with the development of economy
in this area. Furthermore, analysis of isomer ratios and principle component analysis commonly revealed the main contribution
of anthropogenic pyrolytic source to PAH contamination in the largest urban lake of China.
KeywordsPAHs–Sediment core–Toxicity trends–Donghu Lake–Yangtze River
Water Air and Soil Pollution 04/2012; 217(1):577-587. · 1.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants. Due to their low water solubility and high
hydrophobicity, PAHs are rapidly sorbed onto particles and subsequently deposit in sediments once introduced into aquatic
environment. In such a way, sediments become a huge sink for PAHs. During sediment resuspension, the potential exists for
PAHs to be released from sediments into water. Sediment resuspension plays an important role in the transportation and fate
of PAHs in the aquatic environment. In this study, release behavior of PAHs on Yangtze River sediment during resuspension
was investigated using a particle entrainment simulator (PES). The role of resuspension duration on release of 16 PAHs was
measured by resuspending sediment for 12 h at 0.2 and 0.5 N/m2, respectively. Results indicated that PAH concentrations in TSS increase over time with more increase of phenanthrene and
4-ring PAHs. Comparing with 0.2 N/m2 (30%), ΣPAHs concentrations in TSS demonstrated remarkable increase during 0.5 N/m2 resuspension (37%). Dissolved PAH concentrations increased throughout the duration with more increase of 2–3 ring PAHs (50%–88%).
Dissolved PAH concentrations showed remarkable increase during 0.5 N/m2 resuspension (50%). Moreover, PAH concentrations in overlying water throughout the duration of resuspension were higher than
toxic effects threshold values in drinking water developed by WHO, which may cause toxic effect on ecosystem.
Chinese Science Bulletin 04/2012; 53(18):2777-2782. · 1.32 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The influences of suspended particles (SPs) on NH4
+ adsorption and nitritation occurring in the water system of the Three Gorges Reservoir (TGR) were evaluated in this study.
The results indicated that the adsorption of NH4
+ was significantly affected by the SPs concentration under the conditions typically present in the TGR. The amount of ammonia
adsorbed per unit weight of suspended particles was inverse proportional to the concentration of suspended particles. However,
the influences of the particle size and the organic matter concentration existing in SPs were insignificant under the experimental
conditions. The effects of suspended particles on nitritation were determined by the use of ammonia-oxidizing bacteria (AOB)
strain SW16, identified as Nitrosomonas nitrosa, which was isolated from sediment samples of the TGR. Suspended particle concentration in water–sediment solution played
an important role in the nitritation process. The rate of nitritation enhanced with the increase of the suspended particle
concentration. It was found that the critical factor controlling ammonia oxidizing rate was the AOB biomass resulting from
the AOB growth rate. Moreover, results demonstrated that both particle size and organic matter content showed little effect
on the nitritation process under the experimental conditions.
KeywordsAmmonia adsorption-Ammonia-oxidizing bacteria-Nitritation-
Nitrosomonas nitrosa
-Suspended particles-Three Gorges Reservoir
Environmental earth sciences 04/2012; 60(8):1653-1660. · 1.06 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To assess ozone sensitivity of subtropical broadleaved tree species and explore possible underlying mechanisms, six evergreen and two deciduous native species were exposed to either charcoal-filtered air or elevated O(3) (E-O(3), ∼150ppb) for one growing season. Initial visible symptoms in deciduous species appeared much earlier than those in evergreen species. The species which first showed visible symptoms also had the largest reductions in biomass. E-O(3) induced significant decreases in photosynthesis rate, chlorophyll content and antioxidant capacity but a significant increase in malondialdehyde content in two deciduous species and two evergreen species (Cinnamomum camphora and Cyclobalanopsis glauca). Except C. glauca, however, E-O(3) had no significant effects on stomatal conductance (g(s)), total phenols and ascorbate contents. Difference in O(3) sensitivity among all species was strongly attributed to specific leaf mass rather than g(s). It suggests that some subtropical tree species will be threatened by rising O(3) concentrations in the near future.
Environmental pollution (Barking, Essex: 1987) 04/2012; 163:149-57. · 3.43 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The [Ni|Cu] microcell was prepared by mixing the Ni(0) and Cu(0) particles. The composition and crystal form were characterized by X-ray diffraction (XRD) and scanning electron microscope. The results evidenced the zero-valence metals Ni and Cu were exposed on the surface of particles mixture. The [Ni|Cu] microcell was employed to decompose chlorophenols in aqueous solution by reductive dechlorination. The dechlorination rates of chlorophenols by [Ni|Cu] were >10 times faster than those by [Fe|Cu], [Zn|Cu], [Sn|Cu], and [Fe|Ni] mixtures under the same conditions. [Ni|Cu] is different from other zero valent metals (ZVMs) in that it performed the best at neutral pH. The main products of chlorophenol dechlorination were cyclohexanol and cyclohexanone. The reduction kinetics was between pseudo zero-order and first-order, depending on the pH, concentration, and temperature. These results, combined with electrochemical analysis, suggested that Ni(0) acted as a reductant and catalyst in dechlorination reaction. The H* corridor mechanism from Ni(0) to Cu(0) was also proposed based on hydrogen spillover. The inhibition on the release of Ni(2+) by adding natural organic matters and adjusting pH was investigated.
Journal of hazardous materials 03/2012; 209-210:414-20. · 4.14 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Spatial distribution and source apportionment of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the Yangtze Estuary, especially the North Branch, have been fully investigated. PAH concentrations increased with the descending distance from the inner estuary to the adjacent sea, and varied significantly in various estuarine regions. Water currents (e.g., river runoff and ocean current) greatly affected the distribution pattern. In addition, ambient sewage and traffic also contributed to the PAH pollution in the estuary. In the adjacent sea, PAH values along the -20m isobath were higher than those along the -10m isobath due to the "marginal filter" phenomenon formed by different water currents. In most sites, PAHs had poor correlations with sediment size, but had positive correlations with total organic carbon. Based on the qualitative and quantitative analysis results, PAH sources were proved to be mainly from a mixture of petroleum combustion, biomass, and coal combustion.
Marine pollution bulletin 03/2012; 64(3):636-43. · 2.63 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The removal of polycyclic aromatic hydrocarbons (PAHs) from soil is costly and time-consuming. The high hydrophobicity of PAHs makes PAH diffusion from soil particles by hydraulic flow difficult. The phase transfer of PAHs from soil to another available mediator is crucial for PAH removal. This study focuses on the remediation of PAH-contaminated shoal soil, located in Yangtze, China, using three types of laccase-carrying electrospun fibrous membranes (LCEFMs) fabricated via emulsion electrospinning. These LCEFMs were composed of core-shell structural nanofibers (for PAH adsorption), with laccase in the core (for PAH degradation) and pores on the shell (for mass transfer). The LCEFMs with strong adsorptivity extracted the PAHs from the soil particles, resulting in an obvious enhancement of PAH degradation. The removal efficiencies in 6 h for phenanthrene, fluoranthene, benz[a]anthracene and benzo[a]pyrene were greater than 95.1%, 93.2%, 79.1%, and 72.5%, respectively. The removal half-lives were 0.003-1.52 h, much shorter than those by free laccase (17.9-67.9 h) or membrane adsorption (1.25-12.50 h). The third-order reaction kinetics suggested that the superficial adsorption and internal diffusion were the rate-limiting steps of the overall reaction. A synergistic effect between adsorption and degradation was also proposed on the basis of the triple phase distribution and kinetics analyses.
Environmental Science & Technology 11/2011; 45(24):10611-8. · 4.80 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A biosensor based on Trametes versicolor laccase (Lac) was developed for the determination of phenolic compounds. The biosensor was prepared by in situ electrospinning of a mixture of polyvinyl alcohol (PVA), Lac, PEO-PPO-PEO (F108) and gold nanoparticles (Au NPs), where F108 was used as an enzyme stabilizing additive and Au NPs was used to enhance the conductivity of the biosensor. Laser confocal scanning microscopy and electrochemical impedance spectroscopy proved that the enzyme was successfully encapsulated into the electrospun nanofibers. Under the optimal conditions, the lowest detection limit was found to be 0.04 μM (S/N = 3) for 2,4-DCP and the highest detection limit was found to be 12.10 μM for 4-CP. The sensitivity of the biosensor obtained in the linear range for chlorophenols followed the sequence 2,4-dichlorophenol (2,4-DCP) > 2,4,6-trichlorophenol (2,4,6-TCP) > 4-chlorophenol (4-CP). The sensing performance for chlorophenols was attributed to the suitable electrochemical interface of PVA/F108/Au NPs/Lac, resulting from biocompatibility, a high surface area-to-volume ratio (10.42 m(2) g(-1)) and superior mechanical properties of the electrospun nanofibers. The biosensor exhibited good repeatabilities of 7.6%, 2.8% and 9.0% (R.S.D.) and reproducibilities of 14.9%, 10.4% and 13.7% (R.S.D.) for 4-CP, 2,4-DCP and 2,4,6-TCP, respectively. Lac retained 65.8% of its initial activity after a 30-day storage period.
The Analyst 09/2011; 136(22):4802-8. · 4.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The effects of elevated ozone (O(3)) and enhanced nitrogen (N) on the growth and biomass of Cinnamomum camphora, a subtropical evergreen broad-leaved tree species, were investigated. The seedlings, supplied with N (NH(4)NO(3) solution) at 0, 30 and 60 kg ha(-1) year(-1) (simplified as N0, N30, N60, respectively), were exposed to ambient (AA) or elevated O(3) (AA + 60 nmol mol(-1) and AA + 120 nmol mol(-1), designated as AA + 60 and AA + 120, respectively) for the 2009 and 2010 growing seasons. Symptomatic leaf percentages were significantly increased with O(3) concentration. AA + 120 significantly decreased the mean leaf size and chlorophyll content of both 2009- and 2010-emerged leaves, inhibited the growth of stem height and basal diameter, and reduced biomass accumulation of all plant parts except for leaves. By comparison, only the chlorophyll content of 2009-emerged leaves and root dry weight were significantly reduced under AA + 60. Specific leaf area, total leaf area and foliar biomass were not affected even at a higher O(3) level. On the other hand, N loads, especially N60, exerted significantly positive effects on all variables except mean leaf size and shoot/root ratio. No significant interactions between O(3) and N were detected, suggesting that the N supply at ≤60 kg ha(-1) year(-1) did not significantly modify the response of C. camphora to O(3) in terms of seedling growth and biomass accumulation.
Journal of Environmental Monitoring 08/2011; 13(10):2873-9. · 1.99 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Photolysis of Enro in water was investigated under simulated sunlight irradiation using a Xenon lamp. The results showed that Enro photolysis followed apparent first-order kinetics. Increasing Enro concentration from 5.0 to 40.0 mg L⁻¹ led to the decrease of the photolysis rate constant from 1.6 × 10⁻² to 3.0 × 10⁻³ min⁻¹. Compared with the acidic and basic conditions, the photolysis rate was faster at neutral condition. Both of nitrate and humic acid can markedly decrease the photolysis rate of Enro because they can competitively absorb photons with Enro. The electron spin resonance and reactive oxygen species scavenging experiments indicated that Enro underwent self-sensitized photooxidation via OH and ¹O₂. After irradiation for 90 min, only 13.1% reduction of TOC occurred in spite of fast photolysis of 58.9% of Enro, indicating that Enro was transformed into intermediates without complete mineralization. The photolysis of Enro involved three main pathways: decarboxylation, defluorination, and piperazinyl N⁴-dealkylation. The bioluminescence inhibition rate using Vibrio fischeri increased to 67.2% at 60 min and then decreased to 56.9% at 90 min, indicative of the generation of some more toxic intermediates than Enro and then the degradation of the intermediates. The results will help us understand fundamental mechanisms of Enro photolysis and provide insight into the potential fate and transformation of Enro in surface waters.
Chemosphere 07/2011; 85(5):892-7. · 3.21 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Five types of nanofibrous membranes were prepared by electrospinning poly(ε-caprolactone) (PCL), poly(D,L-lactide) (PDLLA), poly(lactide-co-caprolactone) (P(LA/CL)), poly(D,L-lactide-co-glycolide) (PDLGA) and methoxy polyethylene glycol-poly(lactide-co-glycolide) (MPEG-PLGA), respectively. These electrospun nanofibrous membranes (ENFMs) were used to adsorb anthracene (ANT), benz[a]anthracene (BaA) and benzo[a]pyrene (BaP) from aqueous solution, and the sorption kinetics and isotherms of these PAHs on the five ENFMs were investigated. The pseudo-second-order model (PSOM) can well describe the sorption kinetics of the three PAHs on five ENFMs, and the partition-adsorption model (PAM) can interpret the sorption processes of PAHs on the ENFMs. PCL ENFMs, which had the largest surface areas (8.57 m(2)g(-1)), exhibited excellent sorption capacity for ANT at over 4112.3 ± 35.5 μg g(-1). Moreover, the hydrophobicity and pore volume of ENFMs significantly affected the sorption kinetics and sorption capacity of the PAHs. The main sorption mechanisms of three PAHs on the PDLLA ENFMs included hydrophobic interactions and pore-filling, while those of PCL, P(LA/CL) and PDLGA ENFMs were dominated by the hydrophobic interactions. The sorption mechanisms of MPEG-PLGA ENFMs primarily included pore-filling, hydrogen bonding interactions and hydrophobic interactions. Additionally, π-π bonding interaction was also deduced to be involved in all of ENFMs sorption systems.
Journal of hazardous materials 06/2011; 192(3):1409-17. · 4.14 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Sorption of polycyclic aromatic hydrocarbons (PAHs) to natural sediment and isolated organic fractions, including demineralized organic matter (DM), condensed organic matter (COM), and black carbon (BC), was investigated to provide insight into sorption mechanisms. The organic carbon normalized distribution coefficient K(OC) measured for DM was 0.8 to 3.0 times higher than that of bulk sediment, indicating the physical protection of favorable PAH sorption domains by mineral conformation; that is, mineral enwrapping was supposed to prevent physically the accessing process of the sorbate molecules to the sorption domain. Surface area-normalized K(OC) values showed that the differences between COM and BC in the sorption capability were caused largely by their surface areas, additionally indicating the importance of solid physical structure. In considering specific interactions, mature organic fractions with polyaromatic sheets were implied to be affected by π-π interaction, whereas the DM sample that contained the electron-repulsive N-H group hardly sorbed PAHs via this interaction. Besides sorbent characteristics, PAH properties were also assumed to influence the sorption process. The hydrophobicity normalized sorption coefficient increased in the order of fluoranthene> phenanthrene> pyrene> fluorine> acenaphthene, with pyrene showing an exceptional order.
Environmental Toxicology and Chemistry 03/2011; 30(3):576-81. · 2.81 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Rapid and efficient methods to assess nanoparticle toxicity are desired in current research. Here we showed that Escherichia coli labeled by green fluorescent protein can be a good model bacterium for assessing acute toxicity of TiO(2) (about 50% inhibition ratios after 135 min exposure). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed that TiO(2) nanoparticles (NPs) can influence certain protein expression in the recombinant bacterium, and the obvious effects in repressed expression and elevated expression were observed in 30/40, 10/20 μg mL(-1) treated cells, respectively. However, the GFP expression (27 kD) was not influenced by introduced TiO(2) NPs. The change of the fluorescence intensity may be caused by the damage in folding and chromophore formation of the GFP post-translational modification due to generated reactive oxygen species. Furthermore, TiO(2) NPs at higher concentrations decreased their toxicity because of aggregation. 20 μg mL(-1) humic acid (HA) introduced to the medium can decrease the fluorescent inhibition owing to the barrier of steric hindrance it provides between NPs and cells.
Journal of Environmental Monitoring 01/2011; 13(1):42-8. · 1.99 Impact Factor
