Guadalupe de la Rosa

Nanomaterials and the environment: A review for the biennium 2008–2010

Applications of nanotechnology are touching almost every aspect of modern life. The increased use of engineered nanomaterials (ENMs) in consumer products, chemical and medical equipment, information technology, and energy, among others, has increased the number of publications (informative and scientific) on ENMs. By the 1950s, very few papers were committed to nanomaterials (NMs), but in 2009, more than 80,000 journal articles included the concept nanotechnology. The objective of this review is to compile and analyze publications on NMs in the biennium 2008-2010. This review includes the most recent publications in risk assessment/toxicity, characterization and stability, toxicity, fate and transport of NMs in terrestrial ecosystems, and new ENMs. Carbon nanotubes, metallic, metal oxides and hydroxides nanoparticles, quantum dots, and polystyrene NPs are included.

Kinetic and Thermodynamic Modeling of Cd+2 and Ni+2 Biosorption by Raw Chicken Feathers

Batch experiments were performed to model kinetic and thermodynamic data for Cd+2 and Ni+2 biosorption by raw chicken feathers (CFs) under different conditions. Results indicated that Cd+2 and Ni+2 sorption onto CFs occurred on the external surface of the biosorbent. Ion removal increased with pH, whereas both endothermic and exothermic stages where observed depending on temperature. Our calculated thermodynamic parameters showed that, below the temperature of 30°C, the metal uptake of Cd+2 and Ni+2 ions may be mainly controlled by a chemisorption process. However, for temperatures higher than 30°C, it is likely that sorption of both metals onto CFs is caused by a combination of both physical and chemical processes, especially for Ni+2 ions. Maximum sorption capacities were of 0.039 (Cd+2 ) and 0.065 mmol/g (Ni+2) at pH 5 and 30°C. Using 0.1 M HCl or CH3COOH as desorbing agents, approximately a 50% recovery for Cd+2 was achieved. The pseudo-second order and the general rate law models best fit the sorption kinetics data. The equilibrium metal uptake data was best described by the Sips isotherm.

Toxicity and biotransformation of ZnO nanoparticles in the desert plants Prosopis juliflora-velutina, Salsola tragus and Parkinsonia florida

Although arid and semiarid regions account for about 40% of world land, no nanotoxicity studies on desert plants have been reported. In this investigation, Parkinsonia florida (blue palo verde), Prosopis juliflora-velutina (velvet mesquite) and Salsola tragus (tumbleweed) were selected to determine the phytotoxicity of ZnO nanoparticles (NPs) at germination stage. Seeds were treated with ZnO NP concentrations ranging between 0 and 4000 mg L−1. From this, the germination rate, root elongation and Zn concentration in tissues were determined. Furthermore, X-ray Absorption Spectroscopic (XAS) studies were performed to obtain preliminary information on potential NP biotransformation within plant tissues. Results indicated that germination was not significantly affected (P < 0.05) in any of the three plant species. Also, root elongation in blue palo verde was reduced by 16%, with respect to control at 4000 mg ZnO L−1. Tumbleweed root size diminished by 14% and 16% at ZnO NP levels of 500 and 2000 mg L−1, respectively, and velvet mesquite root length was reduced to all ZnO NP concentrations used in this study. The 50% inhibitory concentration (IC50) for mesquite root elongation was between 1000 mg L−1 and 2000 mg L−1. XAS results demonstrated that ZnO NPs were biotransformed on/within the root and Zn was present as Zn(II) in the three desert plant species.

Biochemical and spectroscopic studies of the response of Convolvulus arvensis L. to chromium(III) and chromium(VI) stress

The objective of the present study was to determine the oxidative stress caused by hexavalent chromium (Cr[VI]), the chromium (Cr) uptake, and the Cr speciation in Convolvulus arvensis L. plants grown in hydroponics media containing either Cr(VI) or Cr(III). The results demonstrated that C. arvensis plants exposed to Cr(VI) concentrations ranging from 0 to 40 mg/L expressed higher ascorbate peroxidase specific activity in roots than in shoots. On the other hand, catalase activity monitored in plants exposed to 2 mg/L of Cr(VI) for 24 h increased in roots after a few hours of exposure. However, catalase activity in shoots revealed a decrement almost immediately after treatment was initiated. The results from x-ray absorption spectroscopic studies indicated that the oxidation state of the supplied Cr(III) remained the same in plant tissues. The supplied Cr(VI), however, was reduced to the trivalent form in plant tissues. The results of inductively coupled plasma/optical emission spectroscopy demonstrated that after 5 d, the roots of plants exposed to 40 mg/L of Cr(III) or Cr(VI) accumulated approximately 25,000 and 3,500 mg/kg dry weight of Cr, respectively. Nevertheless, shoots concentrated 1,500 and 2,000 mg/kg dry weight of Cr from Cr(III) and Cr(VI), respectively, which indicated that Cr moved faster into C. arvensis plants when supplied as Cr(VI).

Role of ethylenediaminetetraacetic acid on lead uptake and translocation by tumbleweed (Salsola kali L.)

Tumbleweed plants (Salsola kali L.) grown in agar and liquid media demonstrated a high capacity to accumulate Pb in their different parts without affecting biomass. Whereas shoot elongation and biomass were not significantly affected by high tissue concentrations of Pb, root growth was significantly affected relative to controls. Roots, stems, and leaves demonstrated Pb concentrations of 31,000, 5,500, and 2,100 mg/kg dry weight, respectively, when plants were grown in the agar medium containing 80 mg Pb/L. Application of ethylenediaminetetraacetic acid (EDTA) to Pb-contaminated media dramatically reduced the total acquisition of Pb from both types of media. However, EDTA significantly increased the translocation of Pb from roots to the aerial parts, as evidenced by a multifold increase (23- and 155-fold for agar and liquid media, respectively) in the translocation concentration factor. The concentration of the antioxidant thiol compounds significantly increased (p < 0.05) in plants grown with uncomplexed Pb treatments relative to control plants. Scanning-electron microscopy and electron dispersive x-ray spectroscopic evaluation of leaf samples demonstrated an interesting pattern of Pb translocation in the presence or absence of EDTA. Large Pb crystals were found across the leaf tissues (palisade, spongy parenchyma, and conducting tissues) in the absence of EDTA. Lead nanoparticles also were seen when plants were grown in Pb-EDTA solution. Ultramicroscopic features of tumbleweed provide clear evidence for the unrestricted conduction of Pb from the root to the aerial parts, and this property makes the plant a good candidate for phytoremediation.

Physiological and biochemical response of plants to engineered NMs: Implications on future design

Engineered nanomaterials (ENMs) form the basis of a great number of commodities that are used in several areas including energy, coatings, electronics, medicine, chemicals and catalysts, among others. In addition, these materials are being explored for agricultural purposes. For this reason, the amount of ENMs present as nanowaste has significantly increased in the last few years, and it is expected that ENMs levels in the environment will increase even more in the future. Because plants form the basis of the food chain, they may also function as a point-of-entry of ENMs for other living systems. Understanding the interactions of ENMs with the plant system and their role in their potential accumulation in the food chain will provide knowledge that may serve as a decision-making framework for the future design of ENMs. The purpose of this paper was to provide an overview of the current knowledge on the transport and uptake of selected ENMs, including Carbon Based Nanomaterials (CBNMs) in plants, and the implication on plant exposure in terms of the effects at the macro, micro, and molecular level. We also discuss the interaction of ENMs with soil microorganisms. With this information, we suggest some directions on future design and areas where research needs to be strengthened. We also discuss the need for finding models that can predict the behavior of ENMs based on their chemical and thermodynamic nature, in that few efforts have been made within this context.

Effect of Sulfate on Selenium Uptake And Chemical Speciation in Convolvulus Arvensis L

Environmental Context. Selenium (Se) is one of the most serious problems confronted in agricultural soils derived from Se-containing rocks. This metalloid, an essential nutrient for animals and humans, may be toxic at relatively low concentrations. Se removal from soil and water using plants is a promising alternative to traditional chemical or electrochemical techniques. However, very few plant species are able to accumulate Se at high concentrations. Since Se and sulfur (S) have similar chemical properties, sulfate (SO42−) in the plant growth media may interfere in the process of Se uptake by plants. Thus, plant species able to uptake more Se than S when both elements are present are desired for Se phytoremediation purposes. Abstract. Hydroponic experiments were performed to study several aspects of Se uptake by C. arvensis plants. Ten day old seedlings were exposed for eight days to different combinations of selenate (SeO42−), sulfate (SO42−), and selenite (SeO32−). The results showed that in C. arvensis, SO42− had a negative effect (P < 0.05) on SeO42− uptake. However, a positive interaction produced a significant increase in SO42− uptake when SeO42− was at high concentration in the media. X-ray absorption spectroscopy studies showed that C. arvensis plants converted more than 70% of the supplied SeO32− into organoselenium compounds. However, only approximately 50% of the supplied SeO42− was converted into organoselenium species while the residual 50% remained in the inorganic form. Analysis using LC-XANES fittings confirmed that the S metabolic pathway was affected by the presence of Se. The main Se compounds that resembled those Se species identified in C. arvensis were Se-cystine, Se-cysteine, SeO32−, and SeO42−, whereas for S the main compounds were cysteine, cystine, oxidized glutathione, reduced glutathione, and SO42−. The results of these studies indicated that C. arvensis could be considered as a possible option for the restoration of soil moderately contaminated with selenium even in the presence of sulfate.

Analysis and modeling of multicomponent sorption of heavy metals on chicken feathers using Taguchi’s experimental designs and artificial neural networks

AbstractIn this study, we have used an integrated approach based on Taguchi’s experimental designs and artificial neural networks (ANNs) for the analysis and modeling of the simultaneous removal of cadmium (Cd2+), nickel (Ni2+), and lead (Pb2+) ions from ternary aqueous solutions using chicken feathers. Our results indicated that the multicomponent sorption of these heavy metals on chicken feathers is a complex antagonistic process. Specifically, chicken feathers showed a strong preference for the removal of Pb2+ ions in multicomponent solutions and the presence of these ions affected significantly the multicomponent removal of Cd2+ and Ni2+. This antagonistic sorption effect is more significant at pH 5 and the sorption preference of chicken feathers during heavy metal removal depends on the solution pH. Results of X-ray absorption near edge structure suggested that sulfide and carboxylic groups of chicken feathers appear to play a relevant role for the removal of heavy metal ions using this biomass. On t...

Evaluating the role of vegetation on the transport of contaminants associated with a mine tailing using the Phyto-DSS

We identified contaminants associated with the Cata mine tailing depot located in the outskirts of the city of Guanajuato, Mexico. We also investigated strategies for their phytomanagement. Silver and antimony were present at 39 and 31 mg kg(-1), respectively, some twofold higher than the Dutch Intervention Values. Total and extractable boron (B) occurred at concentrations of 301 and 6.3 mg L(-1), respectively. Concentrations of B in soil solution above 1.9 mg L(-1) have been shown to be toxic to plants. Plant growth may also be inhibited by the low concentrations of extractable plant nutrients. Analysis of the aerial portions of Aloe vera (L. Burm.f.) revealed that this plant accumulates negligible concentrations of the identified contaminants. Calculations using a whole system model (Phyto-DSS) showed that establishing a crop of A. vera would have little effect on the drainage or leaching from the site. However, this plant would reduce wind and water erosion and potentially produce valuable cosmetic products. In contrast, crops of poplar, a species that is tolerant to high soil B concentrations, would mitigate leaching from this site. Alternate rows of trees could be periodically harvested and be used for timber or bioenergy.

Environmental behavior of coated NMs: Physicochemical aspects and plant interactions

The application of nanomaterials (NMs) depends on several characteristics, including polydispersity, shape, surface charge, and composition, among others. However, the specific surface properties of bare NMs induce aggregation, reducing their utilization. Thus, different surface coverages have been developed to avoid or minimize NMs aggregation, making them more stable for the envisioned applications. Carbon-based NMs are usually coated with metals, while metal-based NMs are coated with natural organic compounds including chitosan, dextran, alginate, or citric acid. On the other hand, the coating process is expected to modify the surface properties of the NMs; several coating agents add negative or positive charges to the particles, changing their interaction with the environment. In this review, we analyze the most recent literature about coating processes and the behavior of coated NMs in soil, water, and plants. In particular, the behavior of the most commercialized metal-based NMs, such as TiO2, ZnO, CeO2, CuO, Ag, and Au, and carbon-based NMs are discussed in this review. The available articles about the effects of coated NMs in plants are discussed. Up to now, there is no uniformity in the information to ensure that the surface coverage increases or decreases the effects of NMs in plants. While some parameters are increased, others are decreased. Since the data is contradictory in some cases, the available literature does not allow researchers to determine what concentrations benefit the plants. This review highlights current results and future perspectives on the study of the effects of coated NMs in the environment.