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Showing papers by "Pedro J. J. Alvarez published in 2010"


Journal ArticleDOI
TL;DR: In this article, the occurrence of antibiotics and antibiotic resistance genes (ARGs) was quantified in water and sediment samples collected from a 72 km stretch of the Haihe River, China.
Abstract: The occurrence of antibiotics and antibiotic resistance genes (ARGs) was quantified in water and sediment samples collected from a 72 km stretch of the Haihe River, China. Tetracycline resistance genes (tetW, tetQ, tetO, tetT, tetM, tetB, and tetS) were not detected by quantitative PCR in many samples. In contrast, sul1 and sul2 (coding for sulfonamide resistance) were present at relatively high concentrations in all (38) samples. The highest ARG concentrations detected were (7.8 ± 1.0) × 109 copies/g for sul1 and (1.7 ± 0.2) × 1011 copies/g for sul2, in sediment samples collected during the summer. The corresponding total bacterial concentration (quantified with a universal 16S-rDNA probe) was (3.3 ± 0.4) × 1012 cells/g. Sul1 and sul2 concentrations in sediments were 120−2000 times higher than that in water, indicating that sediments are an important ARG reservoir in the Haihe River. Statistical analysis indicated a positive correlation between the relative abundance of these ARGs (i.e., sul1/16S-rDNA an...

652 citations


Journal ArticleDOI
12 Jul 2010-ACS Nano
TL;DR: In this paper, state-of-the-art applications of nanomaterials that improve conventional construction materials, suggest likely environmental release scenarios, and summarize potential adverse biological and toxicological effects and their mitigation.
Abstract: The extraordinary chemical and physical properties of materials at the nanometer scale enable novel applications ranging from structural strength enhancement and energy conservation to antimicrobial properties and self-cleaning surfaces Consequently, manufactured nanomaterials (MNMs) and nanocomposites are being considered for various uses in the construction and related infrastructure industries To achieve environmentally responsible nanotechnology in construction, it is important to consider the lifecycle impacts of MNMs on the health of construction workers and dwellers, as well as unintended environmental effects at all stages of manufacturing, construction, use, demolition, and disposal Here, we review state-of-the-art applications of MNMs that improve conventional construction materials, suggest likely environmental release scenarios, and summarize potential adverse biological and toxicological effects and their mitigation Aligned with multidisciplinary assessment of the environmental implicatio

627 citations


Journal ArticleDOI
TL;DR: Overall, this study shows that direct exposure to nanoparticles significantly contributed to phytotoxicity and underscores the need for eco-responsible disposal of wastes and sludge containing metal oxide nanoparticles.
Abstract: Phytotoxicity is an important consideration to understand the potential environmental impacts of manufactured nanomaterials. Here, we report on the effects of four metal oxide nanoparticles, aluminum oxide (nAl(2)O(3)), silicon dioxide (nSiO(2)), magnetite (nFe(3)O(4)), and zinc oxide (nZnO), on the development of Arabidopsis thaliana (Mouse-ear cress). Three toxicity indicators (seed germination, root elongation, and number of leaves) were quantified following exposure to each nanoparticle at three concentrations: 400, 2,000, and 4,000 mg/L. Among these particles, nZnO was most phytotoxic, followed by nFe(3)O(4), nSiO(2), and nAl(2)O(3), which was not toxic. Consequently, nZnO was further studied to discern the importance of particle size and zinc dissolution as toxicity determinants. Soluble zinc concentrations in nanoparticle suspensions were 33-fold lower than the minimum inhibitory concentration of dissolved zinc salt (ZnCl(2)), indicating that zinc dissolution could not solely account for the observed toxicity. Inhibition of seed germination by ZnO depended on particle size, with nanoparticles exerting higher toxicity than larger (micron-sized) particles at equivalent concentrations. Overall, this study shows that direct exposure to nanoparticles significantly contributed to phytotoxicity and underscores the need for eco-responsible disposal of wastes and sludge containing metal oxide nanoparticles.

472 citations


Journal ArticleDOI
TL;DR: This study indicates that polyelectrolyte coatings and NOM will mitigate the toxicity of NZVI for exposure concentrations below 0.1 to 0.5 g/L depending on the coating and that aged NZVI without Fe(0) is relatively benign to bacteria.
Abstract: Nanoscale zerovalent iron (NZVI) is used for groundwater remediation. Freshly synthesized bare, i.e. uncoated NZVI is bactericidal at low mg/L concentration, but the impact of surface modifiers and aging (partial oxidation) on its bactericidal properties have not been determined. Here we assess the effect that adsorbed synthetic polymers and natural organic matter (NOM) and aging (partial oxidation) have on the bactericidal properties of NZVI to the gram-negative bacterium, Escherichia coli. Exposure to 100 mg/L of bare NZVI with 28% Fe0 content resulted in a 2.2-log inactivation after 10 min and a 5.2-log inactivation after 60 min. Adsorbed poly(styrene sulfonate) (PSS), poly(aspartate) (PAP), or NOM on NZVI with the same Fe0 content significantly decreased its toxicity, causing less than 0.2-log inactivation after 60 min. TEM images and heteroaggregation studies indicate that bare NZVI adheres significantly to cells and that the adsorbed polyelectrolyte or NOM prevents adhesion, thereby decreasing NZVI ...

316 citations


Journal ArticleDOI
TL;DR: Results suggest that reductive treatment of chlorinated solvent sites with NZVI might be enhanced by the concurrent or subsequent participation of bacteria that exploit cathodic depolarization and reductive dechlorination as metabolic niches.

228 citations


Journal ArticleDOI
TL;DR: Results show that aqueous solution chemistry is important to tetracycline adsorption on carbon nanotubes.
Abstract: Carbon nanotubes have shown great potential as effective adsorbents for hydrophobic organic contaminants in water treatment. The present study investigated the influence of aqueous solution chemistry on the adsorption of tetracycline to carbon nanotubes. Specifically, the effects of ionic strength (NaCl and CaCl2) and presence of Cu 2þ ion (7.5 mg/L) or dissolved soil or coal humic acids (50 mg/L) on adsorption of tetracycline to single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT), and nonporous pure graphite as a model of the graphite surface were systematically estimated. The presence of humic acids suppressed tetracycline adsorption on graphite and MWNT prominently, with stronger effects observed on graphite, but only slightly affected tetracycline adsorption on SWNT. The relatively large humic acid components could not readily access the small interstitial spaces of SWNT and thus were less competitive with tetracycline adsorption. The presence of Cu 2þ ion increased tetracycline adsorption to both SWNT and MWNT through the mechanism of cation bridging, with much larger effects observed on MWNT. This was probably because when compared with the Cu 2þ ions complexed on the surface of SWNT, those on the surface of MWNT having larger mesoporous interstices were more accessible to the relatively bulky tetracycline molecule. Increasing the ionic strength from 10 mM to 100 mM decreased tetracycline adsorption on both SWNT and MWNT, which was attributed to electronic shielding of the negatively charged surface sites. These results show that aqueous solution chemistry is important to tetracycline adsorption on carbon nanotubes. Environ. Toxicol. Chem. 2010;29:2713-2719. # 2010 SETAC Keywords—Adsorption Carbon nanotubes Tetracycline Aqueous solution chemistry

171 citations


Journal ArticleDOI
TL;DR: The initial aggregation kinetics of aqueous fullerene nanoparticles before and after UVA irradiation was investigated in solutions varying in ionic strength, ionic composition, and humic acid concentration, demonstrating the critical role of nC(60) surface chemistry in its environmental transport and fate.
Abstract: The transport and fate of engineered nanomaterials is affected by multiple environmental factors, including sunlight and natural organic matter. In this study, the initial aggregation kinetics of aqueous fullerene (nC(60)) nanoparticles before and after UVA irradiation was investigated in solutions varying in ionic strength, ionic composition, and humic acid concentration. In NaCl solutions, surface oxidation induced by UV irradiation remarkably increased nC(60) stability due to the increased negative surface charge and reduced particle hydrophobicity; although humic acid greatly enhanced the stability of pristine nC(60) via the steric hindrance effect, it had little influence on the stability of UV-irradiated nC(60) in NaCl due to reduced adsorption on oxidized nC(60) surface. In contrast, UV irradiation reduced nC(60) stability in CaCl(2) due to specific interactions of Ca(2+) with the negatively charged functional groups on UV-irradiated nC(60) surface and the consequent charge neutralization. By neutralizing surface charges of both UV-irradiated nC(60) and humic acid as well as forming intermolecular bridges, Ca(2+) facilitated humic acid adsorption on UV-irradiated nC(60), resulting in enhanced stability in the presence of humic acid. These results demonstrate the critical role of nC(60) surface chemistry in its environmental transport and fate.

103 citations


Journal ArticleDOI
TL;DR: NZVI coating might enhance the expression of dechlorinating genes and the concurrent or sequential participation of Dehalococcoides spp.
Abstract: Nanoscale zerovalent iron (NZVI) can be used to dechlorinate trichloroethylene (TCE) in contaminated aquifers. Dehalococcoides spp. is the only microbial genus known to dechlorinate TCE to ethene as a respiratory process. However, little is known about how NZVI affects the expression of genes coding for reductive dechlorination. We examined a high-rate TCE-dechlorinating mixed culture which contains organisms similar to known Dehalococcoides to study the effects of NZVI on the expression of two model genes coding for reductive dehalogenases (tceA and vcrA). A novel pretreatment approach, relying on magnetic separation of NZVI prior to reverse transcription qPCR (to avoid RNA adsorption by NZVI), was developed and used with relative quantification (relative to 16S rRNA as endogenous housekeeping gene) to quantify reductive dehalogenase gene expression. Both tceA and vcrA were significantly down-regulated (97- and 137-fold, respectively) relative to baseline (time 0) conditions after 72-h exposure to chlori...

100 citations


01 Jan 2010
TL;DR: State-of-the-art applications of MNMs that improve conventional construction materials are reviewed, likely environmental release scenarios are suggested, and potential adverse biological and toxicological effects and their mitigation are summarized.
Abstract: The extraordinary chemical and physical properties of materials at the nanometer scale enable novel applications ranging from structural strength enhancement and energy conservation to antimicrobial properties and self-cleaning surfaces. Consequently, manufactured nanomaterials (MNMs) and nanocomposites are being considered for various uses in the construction and related infrastructure industries. To achieve environmentally responsible nanotechnology in construction, it is important to consider the lifecycle impacts of MNMs on the health of construction workers and dwellers, as well as unintended environmental effects at all stagesofmanufacturing,construction,use,demolition,anddisposal.Here,wereviewstate-of-the-artapplications of MNMs that improve conventional construction materials, suggest likely environmental release scenarios, and summarize potential adverse biological and toxicological effects and their mitigation. Aligned with multidisciplinary assessment of the environmental implications of emerging technologies, this review seeks to promote awareness of potential benefits of MNMs in construction and stimulate the development of guidelines to regulate their use and disposal to mitigate potential adverse effects on human and environmental health.

77 citations


Journal ArticleDOI
TL;DR: The potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic is reported, and differences in competitive advantages of these two strains are indicated.

70 citations


Journal ArticleDOI
TL;DR: The aminoC(60)/silica photocatalyst is capable of effective and kinetically enhanced oxidation of Ranitidine and Cimetidine and inactivation of MS-2 bacteriophage compared to aqueous solutions of the C(60) aminofullerene alone and could enable water treatment in less developed areas by alleviating dependence on major infrastructure, including the need for electricity.
Abstract: A new strategy is described to immobilize photoactive C60 aminofullerene on silica gel (3-(2-succinic anhydride)propyl functionalized silica), thus enabling facile separation of the photocatalyst for recycling and repeated use An organic linker moiety containing an amide group was used to anchor C60 aminofullerene to the functionalized silica support The linker moiety prevents aqueous C60 aggregation/agglomeration (shown by TEM images), resulting in a remarkable enhancement of photochemical 1O2 production under visible light irradiation With no loss in efficacy of 1O2 production plus insignificant chemical modification of the aminoC60/silica photocatalyst after multiple cycling, the system offers a promising new visible-light-activated photocatalyst Under visible-light irradiation, the aminoC60/silica photocatalyst is capable of effective and kinetically enhanced oxidation of Ranitidine and Cimetidine (pharmaceutical pollutants) and inactivation of MS-2 bacteriophage compared to aqueous solutions of t

Journal ArticleDOI
TL;DR: The cationic hexakis C60 derivative with amine functionality, C60(CR2)6 (R=CO2(CH2)2NH3+CF3CO2-), was found to exhibit remarkable efficiency to inactivate Escherichia coli and MS-2 bacteriophage under UVA irradiation and is also photoactive in response to visible light from both commercial fluorescence lamps and sunlight.
Abstract: Recently, we reported the successful synthesis of various hexakis C60 derivatives (i.e., C60 with six functional groups containing NH3+-, CO2H-, or OH-terminals) with enhanced stability in water for aqueous phase application (Lee et al., Environ. Sci. Technol. 2009, 43, pp 6604−6610). Among these newly synthesized C60 derivatives, the cationic hexakis C60 derivative with amine functionality, C60(CR2)6 (R = CO2(CH2)2NH3+CF3CO2−), was found to exhibit remarkable efficiency to inactivate Escherichia coli and MS-2 bacteriophage under UVA irradiation. Herein, we report that this amine-functionalized C60 derivative is also photoactive in response to visible light from both commercial fluorescence lamps and sunlight. Efficient production of 1O2, facile reaction of 1O2 with proteins in MS-2 phage capsid and electrostatic attraction between positively charged C60 derivative and negatively charged MS-2 phage collectively contributed to high efficiency of MS-2 phage inactivation in this photocatalytic disinfection s...

Journal ArticleDOI
TL;DR: In this paper, real-time quantitative PCR (qPCR) was used to target the catabolic bssA gene and a 16S rDNA phylogenetic gene (for total Bacteria) as potential biomarkers to infer on anaerobic toluene degradation rates.
Abstract: The assessment of biodegradation activity in contaminated aquifers is critical to demonstrate the performance of bioremediation and natural attenuation and to parameterize models of contaminant plume dynamics. Real time quantitative PCR (qPCR) was used to target the catabolic bssA gene (coding for benzylsuccinate synthase) and a 16S rDNA phylogenetic gene (for total Bacteria) as potential biomarkers to infer on anaerobic toluene degradation rates. A significant correlation (P = 0.0003) was found over a wide range of initial toluene concentrations (1–100 mg/l) between toluene degradation rates and bssA concentrations in anaerobic microcosms prepared with aquifer material from a hydrocarbon contaminated site. In contrast, the correlation between toluene degradation activity and total Bacteria concentrations was not significant (P = 0.1125). This suggests that qPCR targeting of functional genes might offer a simple approach to estimate in situ biodegradation activity, which would enhance site investigation and modeling of natural attenuation at hydrocarbon-contaminated sites.

Journal ArticleDOI
TL;DR: In this article, the binding energy of the C60−OH adduct as a function of C60 clustering degree was analyzed and the results imply that ordered clustering of C 60 in the aqueous phase significantly hinders C60s fundamental reactivity with radical species.
Abstract: Reactions of water-stable C60 clusters (nC60) in water with OH radicals (•OH) and hydrated electrons (eaq−), generated by steady-state γ-radiation, were observed and characterized. Ordered C60 clusters were relatively recalcitrant to highly reactive •OH and eaq− species, with only a fraction of carbons oxidized and reduced, respectively. Pulse radiolysis suggested that the reactions of nC60 with OH• and eaq− were diffusion limited, with rate constants of (7.34 ± 0.31) × 109 M−1 s−1 and (2.34 ± 0.02) × 1010 M−1 s−1, respectively. Quantum mechanical calculations of binding energy of the C60−OH adduct as a function of C60 clustering degree indicate, despite an initial fast reaction, a slower overall conversion due to thermodynamic instability of C60−OH intermediates. The results imply that ordered clustering of C60 in the aqueous phase significantly hinders C60’s fundamental reactivity with radical species.

Journal ArticleDOI
TL;DR: Benzene plume elongation and longevity were more pronounced in the presence of alcohols that biodegrade slower (e.g., propanol and n-butanol), forming longer and more persistent alcohol plumes, illustrating the significant effect that a small difference in chemical structure can have on biodegradation.

Journal ArticleDOI
TL;DR: Microarrays were used to study mineralization of the most common oxysterol, 7-ketocholesterol (7KC), by Rhodococcus jostii RHA1, resulting in 363 differentially expressed genes, including upregulation of two large gene clusters putatively encoding steroid catabolism.
Abstract: Oxysterols from steroid autooxidation have numerous harmful effects, but their biodegradation is poorly understood. Microarrays were used to study mineralization of the most common oxysterol, 7-ketocholesterol (7KC), by Rhodococcus jostii RHA1. Growth on 7KC versus growth on cholesterol resulted in 363 differentially expressed genes, including upregulation of two large gene clusters putatively encoding steroid catabolism. Despite this difference, 7KC degradation required key genes involved in cholesterol degradation, indicating a common catabolic route.

Journal ArticleDOI
01 Mar 2010
TL;DR: The authors summarizes the extent of this water footprint and explores mechanisms for reducing the resulting impacts and explores how to reduce the water footprint of dedicated crops used for bio-fuels in the US.
Abstract: The US mandates for increased use of domestically produced biofuels will help to reduce the dependence on imported oil, yet it will necessitate the increased use of our earth and ecosystem services, our ‘natural capital’. Biofuels can be sustainably produced if we recognize the limits of our soil, water and air resources to provide these services. Many of the dedicated crops used for biofuels have a significant water footprint. That is, they consume water for growth and evapotranspiration, and a fraction of the agrochemicals used to obtain higher yields are leached into surface water bodies. This opinion summarizes the extent of this water footprint and explores mechanisms for reducing the resulting impacts.

01 Jan 2010
TL;DR: A comprehensive research paper evaluating the government's multi-billion dollar support of ethanol production to meet the goal of enhancing energy security in an environmentally sustainable fashion is presented in this article, where the authors evaluate the effectiveness of the subsidies.
Abstract: A comprehensive research paper evaluating the government's multi-billion dollar support of ethanol production to meet the goal of enhancing energy security in an environmentally sustainable fashion.

Journal ArticleDOI
TL;DR: The proposed spectrophotometric assay is a simple approach to quantify TDO activity, and demonstrates how the presence of ethanol in groundwater contaminated with reformulated gasoline is likely to interfere with naturally occurring microorganisms from fully expressing their aerobic catabolic potential towards hydrocarbons bioremediation.
Abstract: Toluene dioxygenase (TDO) is ubiquitous in nature and has a broad substrate range, including benzene, toluene, ethylbenzene and xylenes (BTEX). Pseudomonas putida F1 (PpF1) induced on toluene is known to produce indigo from indole through the activity of TDO. In this work, a spectrophotometric assay previously developed to measure indole to indigo production rates was modified to characterize the effects of various ethanol concentrations on toluene aerobic biodegradation activity and assess catabolite repression of TDO. Indigo production rate by cells induced on toluene alone was 0.0012 ± 0.0006 OD610 min−1. The presence of ethanol did not fully repress TDO activity when toluene was also available as a carbon source. However, indigo production rates by PpF1 grown on ethanol:toluene mixtures (3:1 w/w) decreased by approximately 50%. Overall, the proposed spectrophotometric assay is a simple approach to quantify TDO activity, and demonstrates how the presence of ethanol in groundwater contaminated with reformulated gasoline is likely to interfere with naturally occurring microorganisms from fully expressing their aerobic catabolic potential towards hydrocarbons bioremediation.

Patent
24 Jun 2010
TL;DR: In this article, the present disclosure describes fullerene derivatives that are capable of photocatalytically generating reactive oxygen species in the presence of ultraviolet and/or visible light.
Abstract: In various embodiments, the present disclosure describes fullerene derivatives that are capable of photocatalytically generating reactive oxygen species in the presence of ultraviolet and/or visible light. In some embodiments, the fullerene derivatives are aminofullerenes containing a plurality of amine-terminated moieties covalently bonded to the fullerene cage. The fullerene derivatives may optionally be covalently bonded to a substrate surface for use in photocatalytic disinfection systems for removing various contaminants including, for example, bacteria, viruses, protozoa and chemical pollutants. Methods using the present fullerene and aminofullerene derivatives in various purification processes are also described herein.