Showing papers by "Pedro J. J. Alvarez published in 2015"

Fluorescence Reports Intact Quantum Dot Uptake into Roots and Translocation to Leaves of Arabidopsis thaliana and Subsequent Ingestion by Insect Herbivores

Abstract: We explored the impact of quantum dot (QD) coat characteristics on NP stability, uptake, and translocation in Arabidopsis thaliana, and subsequent transfer to primary consumers, Trichoplusia ni (T. ni). Arabidopsis was exposed to CdSe/CdZnS QDs with three different coatings: Poly(acrylic acid-ethylene glycol) (PAA-EG), polyethylenimine (PEI) and poly(maleic anhydride-alt-1-octadecene)–poly(ethylene glycol) (PMAO–PEG), which are anionic, cationic, and relatively neutral, respectively. PAA-EG-coated QDs were relatively stable and taken up from a hydroponic medium through both Arabidopsis leaf petioles and roots, without apparent aggregation, and showed generally uniform distribution in leaves. In contrast, PEI- and PMAO–PEG-coated QDs displayed destabilization in the hydroponic medium, and generated particulate fluorescence plant tissues, suggesting aggregation. PAA-EG QDs moved faster than PEI QDs through leaf petioles; however, 8-fold more cadmium accumulated in PEI QD-treated leaves than in those exposed...

Sublethal Concentrations of Silver Nanoparticles Stimulate Biofilm Development

Abstract: Although silver nanoparticles (AgNPs) are used as antimicrobial agents in a wide variety of commercial products, sublethal exposure can counterproductively promote the development of biofilms. We observed by fluorescence microscopy denser biofilm growth with mixed cultures from a wastewater treatment plant after exposure to 21.6 μg/L 10 nm AgNPs. To further understand biofilm promotion mechanisms, experiments were conducted with a pure culture of Pseudomonas aeruginosa PAO1. Sublethal exposure of PAO1 to AgNPs (10.8 and 21.6 μg/L) also enhanced biofilm development and upregulated quorum sensing, lipopolysaccharide biosynthesis, and antibiotic resistance (efflux pump) genes. An increase in the sugar and protein contents of the PAO1 biofilm matrix (by 55 ± 3 and 114 ± 32%, respectively, relative to unexposed controls) corroborated the transcriptional upregulation of PAO1 biofilm-related genes. Enhanced biofilm development by exposure to low AgNP concentrations might accelerate biofouling and biocorrosion an...

Microbial fuel cells under extreme salinity: performance and microbial analysis

Abstract: Environmental context The treatment of extremely saline, high-strength wastewaters while producing electricity represents a great opportunity to mitigate environmental effects and recover resources associated with wastes from shale oil and gas production. This paper demonstrates that extreme halophilic microbes can produce electricity at salinity up to 3- to 7-fold higher than sea water. Abstract Many industries generate hypersaline wastewaters with high organic strength, which represent a major challenge for pollution control and resource recovery. This study assesses the potential for microbial fuel cells (MFCs) to treat such wastewaters and generate electricity under extreme salinity. A power density of up to 71mWm–2 (318mWm–3) with a Coulombic efficiency of 42% was obtained with 100gL–1 NaCl, and the capability of MFCs to generate electricity in the presence of up to 250gL–1 NaCl was demonstrated for the first time. Pyrosequencing analysis of the microbial community colonising the anode showed the predominance of a single genus, Halanaerobium (85.7%), which has been found in late flowback fluids and is widely distributed in shale formations and oil reservoirs. Overall, this work encourages further research to assess the feasibility of MFCs to treat hypersaline wastewaters generated by the oil and gas industry.

Bench-scale biodegradation tests to assess natural attenuation potential of 1,4-dioxane at three sites in California

Abstract: 1,4-Dioxane (dioxane) is relatively recalcitrant to biodegradation, and its physicochemical properties preclude effective removal from contaminated groundwater by volatilization or adsorption. Through this microcosm study, we assessed the biodegradation potential of dioxane for three sites in California. Groundwater and sediment samples were collected at various locations at each site, including the presumed source zone, middle and leading edge of the plume. A total of 16 monitoring wells were sampled to prepare the microcosms. Biodegradation of dioxane was observed in 12 of 16 microcosms mimicking natural attenuation within 28 weeks. Rates varied from as high as 3,449 ± 459 µg/L/week in source-zone microcosms to a low of 0.3 ± 0.1 µg/L/week in microcosms with trace level of dioxane (<10 µg/L as initial concentration). The microcosms were spiked with 14C-labeled dioxane to assess the fate of dioxane. Biological oxidizer-liquid scintillation analysis of bound residue infers that 14C-dioxane was assimilated into cell material only in microcosms exhibiting significant dioxane biodegradation. Mineralization was also observed per 14CO2 recovery (up to 44 % of the amount degraded in 28 weeks of incubation). Degradation and mineralization activity significantly decreased with increasing distance from the contaminant source area (p < 0.05), possibly due to less acclimation. Furthermore, both respiked and repeated microcosms prepared with source-zone samples from Site 1 confirmed relatively rapid dioxane degradation (i.e., 100 % removal by 20 weeks). These results show that indigenous microorganisms capable of degrading dioxane are present at these three sites, and suggest that monitored natural attenuation should be considered as a remedial response.

Synthesis and characterization of green agents coated Pd/Fe bimetallic nanoparticles

Abstract: The low stability and mobility of nanoparticles in liquid phase is one of the biggest challenges for the application of zero-valent iron (ZVI) technology. In this research, three green agents, polyethylene glycol (PEG), starch, and guar gum were coated on Pd/Fe bimetallic nanoparticles (NPs) to enhance the stability and reactivity of Pd/Fe NPs. The modified NPs (PEG-Pd/Fe, Starch-Pd/Fe, and Guar gum-Pd/Fe NPs) were characterized in terms of specific surface area, particle size, shape, morphology, and structural feature, etc. The results show that the diameters of modified Pd/Fe NPs are in the range of 60–100 nm. Compared with the pristine unmodified Pd/Fe NPs, the aggregations of modified Pd/Fe NPs were successfully reduced. XRD patterns indicate that modified Pd/Fe NPs remained the body centered cubic crystal structure, and the modification process contributed to improve the antioxidant ability. 2,4-Dichlorophenol (2,4-DCP) dechlorination experiments show that physico-chemical properties of the three modifiers have different effects on the reactivity of modified Pd/Fe NPs. The initial pH value of the reaction system had complex effects on the dechlorination of 2,4-DCP by using modified Pd/Fe NPs. Activation energies of pristine, PEG-Pd/Fe, Starch-Pd/Fe, and Guar gum-Pd/Fe NPs were calculated to be 39.47 kJ/mol, 38.66 kJ/mol, 36.59 kJ/mol, and 33.88 kJ/mol, respectively, implying that the modification process can enhance the dechlorination rate of Pd/Fe NPs, and that catalytic hydrodechlorination process of 2,4-DCP with modified Pd/Fe NPs is a surface-controlled chemical reaction.

Rethink the Nicaragua Canal

Abstract: At the end of 2014, construction began on the Grand Canal in Nicaragua, a project shrouded in secrecy since its inception 2.5 years ago. The Nicaraguan government showed scant evidence of having accounted for the impact on the environment and on local residents, or of having adequately consulted the public in selecting the final 278-km route. Such disregard should be alarming to everyone. Projects of this magnitude warrant dialogue among all stakeholders. As construction is projected to span 5 years, there is still time to reconsider it and convene independent assessments and meetings that are transparent, inclusive, and respectful of different perspectives, to guide the project toward the best outcome. ![Figure][1] “…there is still time…to guide the project toward the best outcome.” PHOTO: GUIZIOU FRANCK/HEMIS/CORBIS Declared an income generator by the Nicaraguan government, the Grand Canal is owned by a Chinese company (HKND). It will enter Nicaragua from the Pacific through the Brito River, cross agricultural land and forests, and traverse Lake Cocibolca (the largest tropical lake of the Americas). On the Caribbean side, it will cross pasturelands, forests, natural reserves, wetlands, and indigenous communities, entering the Caribbean close to the Punta Gorda River. At an international multidisciplinary workshop convened in Managua in November 2014, experts from the Academy of Sciences of Nicaragua (ASN) and the Inter-American Network of Academies of Sciences, with support from the International Council for Science in Latin America and the Caribbean, explored technical and scientific aspects of the canal and shared their scientific concerns with the public, HKND, and the government.[*][2] The final communique highlighted the importance of environmental impact assessments (EIAs) on biodiversity and regional water resources, including Lake Cocibolca, which supplies drinking water to the surrounding population. Particularly disquieting is how the initial construction and recurrent dredging of the lake channel might affect the trophic dynamics, water quality, and sedimentation of local rivers, along with implications for domestic water supplies, crop irrigation, and fisheries. Also planned is an artificial lake to serve the canal and lock system. The potential impact of “Lake Atlanta” and the canal on forests, wetlands, and coastal ecosystems has been grossly underexplored. Species cohesiveness and migration are also at risk. Although a private EIA was commissioned by HKND—undermining its independence—it will not be completed before April 2015, diminishing its influence. Most countries follow rigorous environmental guidelines before approving large infrastructure projects. The Nicaraguan government's decision to grant the canal concession without public consultation, feasibility studies, or EIAs departs from such practices and increases the project's risks. Without independent EIAs, unintended and irreversible impacts on wildlife and indigenous populations are more likely. Social unrest is growing along the canal route. Government and security forces are responding by harassing, repressing, and jailing opposition protesters and leaders, increasing fear among the populace. It is incumbent upon scientists, human rights advocates, nongovernmental organizations, and wildlife protection organizations to share knowledge, voice concerns, provide guidance, and demand a greater role for science in the design and construction of this massive project. There is tremendous need for the international scientific community to join ASN and global organizations such as the Association for Tropical Biology and Conservation and the International Society of Limnology to analyze design plans of the canal and its subprojects for safety, social responsibility, and sustainability; make recommendations to protect the region's water resources and biodiversity; and draft statements urging the Nicaraguan government to halt construction until studies can be performed and evaluated by experts. In this matter of great urgency and importance, this is an opportunity to exercise scientific leadership, raise awareness, and contribute to averting a potential environmental disaster. [1]: pending:yes [2]: #fn-1

Poly(vinylidene fluoride) membrane supported nano zero-valent iron for metronidazole removal: Influences of calcium and bicarbonate ions

Abstract: This study examined the influences of calcium and bicarbonate ions on the performance of poly(vinylidene fluoride)-supported nano zero-valent iron (PSN) for metronidazole (MNZ) removal. The presence of Ca 2+ and HCO3 − , whether in their individual or collective forms with low or high levels, exerted differing degrees of inhibitions to MNZ removal by PSN, but these inhibitions were insignificant. Adding some other inorganic ions (i.e. ,N H 4 + ,S O 4 2− ,M g 2+ ,P O 4 3− ,a nd NO 3 − ) into MNZ solutions also caused suppressive effects and their inhibitive ability generally followed the order: NH4 + > SO4 2− > Mg2+ > PO4 3− > NO3 −. Humic acid (HA) was found to introduce relatively larger inhibition to MNZ removal by PSN, whether in its single presence in MNZ solutions or in its coexistence forms with Ca2+ or HCO3 − in MNZ solutions. The interaction of Ca2+ ,H CO 3 − and HA with iron (oxy)hydroxides on PSN surface might contribute to these adverse impacts on PSN–MNZ reaction system. It was noteworthy that, even with 20 mg/L HA in MNZ solutions where high levels of Ca2+ and HCO3 − were introduced, the MNZ removal by PSN was still above 73.37%. Results reported herein indicated the potential of using PSN to pretreat antibiotic wastewaters in complex environmental conditions.

Scientists Raise Alarms About Fast Tracking of Transoceanic Canal through Nicaragua.

Abstract: Seeking economic growth and job creation to tackle the nation's extreme poverty, the Nicaraguan government awarded a concession to build an interoceanic canal and associated projects to a recently formed Hong Kong based company with no track record or related expertise. This concession was awarded without a bidding process and in advance of any feasibility, socio-economic or environmental impact assessments; construction has begun without this information. The 278 km long interoceanic canal project may result in significant environmental and social impairments. Of particular concern are damage to Lake Cocibolca, a unique freshwater tropical lake and Central America's main freshwater reservoir; damage to regional biodiversity and ecosystems; and socio-economic impacts. Concerned about the possibly irreparable damage to the environment and to native communities, conservationists and the scientific community at large are urging the Nicaraguan government to devise and reveal an action plan to address and mitigate the possible negative repercussions of this interoceanic canal and associated projects. Critical research needs for preparation of a comprehensive benefit-cost analysis for this megaproject are presented.

Silver nanoparticles temporarily retard NO2− production without significantly affecting N2O release by Nitrosomonas europaea

Abstract: Nitrifying bacteria are highly susceptible to silver nanoparticles (AgNPs). However, the effect of sublethal exposure to AgNPs after their release of nitrogenous compounds of environmental concern (e.g., the greenhouse gas nitrous oxide [N2O] and the common water pollutant nitrite [NO2−]) has not been systematically investigated. The present study reports the effect of AgNPs (and potentially released silver ions [Ag+]) on NO2− and N2O production by Nitrosomonas europaea, and on the transcription of the associated genes. The release of NO2− was more negatively affected than the production of N2O. For example, exposure to AgNPs at 0.075 mg/L temporarily enhanced N2O production (by 12%) without affecting nitrite release, whereas higher AgNP concentrations (>0.25 mg/L) inhibited NO2− release (by >12%) but not N2O production. Transcriptomic analyses corroborated these trends; AgNPs at 0.075 mg/L increased the expression of the nitric oxide reductase gene (norQ) associated with N2O production (by 5.3-fold to 12.8-fold), whereas both 0.075 mg/L of Ag+ and 0.75 mg/L of AgNPs down-regulated the ammonia monooxygenase gene (amoA2; by 0.08-fold to 0.15-fold and 0.32-fold to 0.64-fold, respectively), the nitrite reductase gene (nirK; by 0.01-fold to 0.02-fold and 0.22-fold to 0.44-fold, respectively), and norQ (by 0.11-fold to 0.15-fold and 0.32-fold to 0.57-fold, respectively). These results suggest that AgNP release to sewage treatment plants and land application of AgNP-containing biosolids should be minimized because of their potential temporary stimulation of N2O release and interference with nitrification. Environ Toxicol Chem 2015;34:2231–2235. © 2015 SETAC