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1.
Int J Biol Macromol ; 164: 3038-3047, 2020 Dec 01.
Artículo en Inglés | MEDLINE | ID: mdl-32853606

RESUMEN

Valorization of lignin by-products enhances the overall economics of current lignocellulose biorefinery. This work showed the high potential of fabricating acid-catalyzed condensed lignin fragments into high-value lignin nanoparticles (LNPs) with spherical structure. Four condensed lignins, i.e., liquid hot water pretreated hardwood aspen and eucalyptus lignin, steam pretreated softwood lodgepole pine and herbaceous corn stover lignin, were assessed for their abilities for LNPs using facile self-assembly method. Results showed the contents of condensed aromatics (0.20-0.67 mmol g-1) were varied with biomass species and hydrothermal pretreatment methods selected. Those resulting LNPs exhibited yields from 17.5 to 29.4%, particle sizes ranging from 20 to 100 nm and considerable suspension stabilities at pH 4-10. It was proposed that higher content of condensed lignin aromatics could provide more anchors available for their self-assembly through enhanced hydrophobic interactions, thus LNPs with more uniform particle size could be obtained. This work showed the technical opportunity to enhance the value of intractable condensed lignin through LNPs production towards a multi-product lignocellulose biorefinery.

2.
J Environ Manage ; 270: 110918, 2020 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-32721350

RESUMEN

Man-made multi-level ditches system is designed to irrigate, drain and collect runoff from surrounding fields. It is not only the conduit of water and field carbon, but also the linear-like wetland with complex carbon cycling. However, the contribution of ditches system to CO2 and CH4 emission has rarely been assessed. To understand the emission pattern of CO2 and CH4 from ditches, this study investigated the emission fluxes of CO2 and CH4 in a three-level ditches system in Chengdu Plain, China. The results showed that the emission of CO2 and CH4 ranged from 70.38 to 950.40 mg C m-2 h-1 and 6.51-74.99 mg C m-2 h-1, respectively, and was higher in spring and summer than other seasons in all ditches (P < 0.05). On the other hand, the emission of CO2 and CH4 increased along with the decreasing ditches size. Besides, it is found that the precipitation, water table depth and water DO concentration might contribute to the emission of CO2, while CH4 was possibly influenced by precipitation, water table depth, temperature, water DO and DOC concentration. Moreover, it is suggested that terrestrial external input and in-situ metabolism might be the main sources of C emission, and in-situ source might largely contribute to CH4 emission. To reduce the C emission, it is necessary to improve fertilization and irrigation methods, limit soil pollutants transferring into ditches, and frequently dredge sediments in future.


Asunto(s)
Oryza , Dióxido de Carbono/análisis , China , Metano/análisis , Óxido Nitroso/análisis , Estaciones del Año , Suelo
3.
Molecules ; 25(5)2020 Mar 04.
Artículo en Inglés | MEDLINE | ID: mdl-32143361

RESUMEN

In this work, ethyl acetate (EA) and trichloromethane (TR) extracts were extracted from Phoebe zhennan wood residues and the extracts were then applied to the preparation of UV shielding films (UV-SF). The results revealed that substances including olefins, phenols and alcohols were found in both EA and TR extracts, accounting for about 45% of all the detected substances. The two extracts had similar thermal stability and both had strong UV shielding ability. When the relative percentage of the extract is 1 wt% in solution, the extract solution almost blocked 100% of the UV-B (280-315 nm), and UV-A (315-400 nm). Two kinds of UV-SF were successfully prepared by adding the two extracts into polylactic acid (PLA) matrix. The UV-SF with the addition of 24 wt% of the extractive blocked 100% of the UV-B (280-315 nm) and more than 80% of the UV-A (315-400 nm). Moreover, the UV shielding performance of the UV-SF was still stable even after strong UV irradiation. Though the addition of extracts could somewhat decrease the thermal stability of the film, its effect on the end-use of the film was ignorable. EA extracts had less effect on the tensile properties of the films than TR extracts as the content of the extract reached 18%. The results of this study could provide fundamental information on the potential utilization of the extracts from Phoebe zhennan wood residues on the preparation of biobased UV shielding materials.

4.
Chemosphere ; 245: 125612, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-31864948

RESUMEN

Humic substances are the dominant dissolved organic matter fraction in the aqueous phase of environmental media. They would inevitably react with chemicals released into the environment. The influence of dissolved humic acid (DHA) on the dissolution and dispersion of copper oxide nanoparticles (CuO NPs, 50 nm, 49.57 mg L-1) was therefore investigated in the present study. In addition to dispersing CuO NPs and reducing the size of the aggregates, the amount of released Cu from CuO NPs was found to increase over time with increasing concentrations of DHA, 96% of which was present as organic complexes after 72 h. At DHA concentrations exceeding 16.09 mg C L-1, the complexation coefficients of DHA with Cu and the adsorptivity of CuO NPs to DHA were both reduced due to increased homo-conjugation of DHA as promoted by negative charge-assisted H-bond. Although the adsorption capacity of DHA kept increasing up to 57.07 mg C L-1, the hydrodynamic diameter and ζ-potential were similar and the percentages of total released Cu continued to increase linearly to 4.92% at higher levels of DHA (30.13-57.07 mg C L-1). Thereupon, DHA promoted the dissolution of CuO NPs in a concentration-dependent fashion. The driving force was complexation of Cu by DHA, rather than the balancing between the exposed and the covered surface area of the CuO NPs due to DHA adsorption. Our findings facilitate understanding the underlying mechanisms on how DHA impacts the CuO NPs environmental behavior (or fate) as well as on their kinetics.


Asunto(s)
Cobre/química , Sustancias Húmicas , Nanopartículas del Metal/química , Adsorción , Difusión , Cinética , Solubilidad , Propiedades de Superficie
5.
Int J Biol Macromol ; 142: 288-297, 2020 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-31593728

RESUMEN

This work tailored a promising two-step pretreatment, i.e., liquid hot water extraction followed by mild acidic deep eutectic solvents pretreatment for clean lignocellulose fractionation while enhancing cellulose reactivity for its subsequent utilization. The abilities of three acidic deep eutectic solvents (formic acid-, acetic acid- and lactic acid-choline chloride) to selectively extract poplar wood lignin and enhance cellulose reactivity were comparatively assessed. Results showed that rather high lignin selectivity of 6.3-7.9 was obtained while the available area and porosity of the resulting cellulose were significantly increased. The resulting cellulose pulps exhibited comparable chemical reactivity to commercial bleached Kraft pulp when cellulose acetate was selected as testing cellulose derivative for demonstrating purpose, showing their great promise for high-value use. It was proposed that the unique ionic properties of these acidic deep eutectic solvents were responsible for their selective lignin removal and cellulose swelling/deconstruction to enhance cellulose chemical reactivity.


Asunto(s)
Biomasa , Celulosa/química , Fraccionamiento Químico , Lignina/química , Lignina/aislamiento & purificación , Solventes/química , Peso Molecular , Polimerizacion , Espectroscopía Infrarroja por Transformada de Fourier
6.
J Hazard Mater ; 388: 121807, 2020 04 15.
Artículo en Inglés | MEDLINE | ID: mdl-31831288

RESUMEN

Iron (Fe) dissimilatory reduction might impact chromium (Cr) mobility in the rice rhizosphere, but it is poorly understood. We assessed rhizosphere microbes' role in Cr immobilization and bioavailability by conducting the pot experiment to test different biochar sources (PMB - pig manure and PSB - pine sawdust) and phosphorus (P) levels impact on Cr mobility. Results showed that PMB application increased root biomass (23-65 %) and decreased root Cr concentration (46-74 %) regardless P treatment. However, P addition reduced root and shoot biomass in control and PMB treatments by 33-43 % and 25-26 %. Therefore, low P input is recommended in Cr-contaminated soil. Moreover, Geobacter was the key microbial groups which may be involved in promoting Cr release by increasing Fe dissolution. Finally, Geobacter and Fe dissimilatory reduction play a central role in Cr translocation and they should be considered in strategies to reduce rice Cr uptake by biochar application.

7.
Sci Rep ; 9(1): 15999, 2019 11 05.
Artículo en Inglés | MEDLINE | ID: mdl-31690791

RESUMEN

As a multifunctional material, biochar is considered a potential adsorbent for removing heavy metals from wastewater. Most biochars with high adsorption capacities have been modified, but this modification is uneconomical, and modifying biochar may cause secondary pollution. Thus, it is necessary to develop an efficient biochar without modification. In this study, spent P. ostreatus substrate and spent shiitake substrate were used as the raw materials to prepare biochar. Then, the physicochemical properties of the biochars and their removal efficiencies for Pb(II) were investigated. The results showed that the physicochemical properties (e.g., large BET surface area, small pore structure and abundant functional groups) contributed to the large adsorption capacity for Pb(II); the maximum adsorption capacities were 326 mg g-1 (spent P. ostreatus substrate-derived biochar) and 398 mg g-1 (spent shiitake substrate-derived biochar), which are 1.6-10 times larger than those of other modified biochars. The Pb(II) adsorption data could be well described by the pseudo-second-order kinetic model and the Langmuir model. This study provides a new method to comprehensively utilize spent mushroom substrates for the sustainable development of the edible mushroom industry.


Asunto(s)
Carbón Orgánico/química , Plomo/química , Pleurotus/química , Hongos Shiitake/química , Residuos/análisis , Adsorción , Cinética
8.
J Environ Manage ; 245: 1-7, 2019 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-31132628

RESUMEN

Nowadays, the plant residual derived biochars have been widely applied to remove nitrogen (N) and phosphorus (P) from water. However, the application of animal manure derived biochars in N and P removal was less studied. To compare the different efficiency and risk of plant residual- and animal manure-derived biochar in removing N and P from water, this study chose rice straw and swine manure as representative to produce biochar at 700 °C, and modified the produced biochar by MgCl2. Then, the characteristics, removal efficiency and release of N and P of biochars were investigated. The results showed swine manure-biochars generally had higher ash content and cation exchange capacity (CEC), but lower pH and surface area relative to rice straw-biochars. Besides, MgCl2 modification reduced the ash content and surface area of both raw biochars, whereas the pH, CEC and pore size were enhanced. Furthermore, this work demonstrated that ammonium and nitrate could be removed by all biochars to certain extent, and MgCl2 modified biochars generally had higher removal efficiency. However, none of phosphate removal was achieved by all biochars. Additionally, the release of ammonium, nitrate and phosphate from biochars was observed, suggesting there might be a risk for applying biochars in N and P removal from water. Notably, the MgCl2 modification seemed to accelerate N and P release from biochars. This work provided important information that the production and modification of biochars should be carefully designed for higher removal efficiency of pollutants. Meanwhile, the risk of released pollutants as well as the release mechanisms should be paid more attention in the future.


Asunto(s)
Estiércol , Oryza , Adsorción , Animales , Carbón Orgánico , Porcinos , Agua
9.
Environ Sci Pollut Res Int ; 26(16): 16596-16605, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30989602

RESUMEN

Multi-level ditch area is a major component of the hydrographic net of plain area, China. Given the high concentration of nitrogen (N) in the surface water and vigorous biogeochemical interactions, ditch is likely to be the hot spots of N2O emission. However, N2O emission flux and emission factor (EF5r) of multi-level ditches have not been determined. To address this knowledge gap, a 1-year field work in three ditches with different levels in Chengdu Plain was conducted. It is found that the annual flux of N2O emission and EF5r was higher in the lateral (0.0020 and 83.94 µg m-2 h-1) and field ditches (0.0019 and 110.75 µg m-2 h-1) than in the branch ditch (0.0016 and 46.38 µg m-2 h-1, P < 0.05). It is found that parameters of groundwater level, discharge, precipitation, and NH4+ were the primary factors, and these parameters can model the N2O flux well. Furthermore, the content of NH4+ in the surface water of ditches presented better correlation with the emission of N2O than the content of NO3-. Therefore, controlling NH4+ emission and lessening fertilizer usage in summer may be key solutions for indirect reduction of N2O in Chengdu Plain.


Asunto(s)
Contaminantes Atmosféricos/análisis , Drenaje de Agua , Agua Dulce/química , Agua Subterránea/química , Óxido Nitroso/análisis , Contaminantes Químicos del Agua/análisis , China , Monitoreo del Ambiente , Fertilizantes/análisis , Nitrógeno/análisis , Estaciones del Año
10.
Chemosphere ; 225: 311-319, 2019 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-30884292

RESUMEN

Biochar can affect the phosphorus (P) cycle in the rice ecosystem through various pathways. Pot experiments were conducted to investigate the risk of P contamination and the P supply rate to crops with the application of maize straw-derived biochar (BM) and P fertilizer. The biochar increased 18.3% and 8.45% total phosphorus (TP) concentration in the low-P level and high-P level soils, respectively. The addition of biochar increased the phosphorus activation coefficient (PAC) by 9.00% at low-P levels, while the PAC was reduced by 10.4% at high-P levels. The results suggested that biochar could serve as either a source or a sink for P. The P concentration in the dithionite-citrate-bicarbonate (DCB) extracts on the root surfaces in biochar-treated soils increased by 467.1% and 46.1% in the low-P level and high-P level soils, respectively. It may cause by the acidification of soils near the root and the increase in Fe plaque. The results also showed the addition of biochar increased the DCB-P concentration and subsequently promoted rice growth. The biochar additions enhanced bacterial community richness and diversity, while the P supplementations inhibited bacterial growth. Redundancy analysis (RDA) showed that available nitrogen (AN), Fe-P, Ca-P, P uptake and, DCB extracted Fe (DCB-Fe) were significantly correlated with microbial community composition and explained 46.8%, 37.1%, 38.0%, 37.5% and 36.7% of the total community variability, respectively. This study provided evidence that biochar might affect the P cycle by impacting the microbial community composition and the Fe-reducing processes in the rice ecosystem.


Asunto(s)
Carbón Orgánico/farmacología , Ecosistema , Microbiota/efectos de los fármacos , Oryza/microbiología , Fósforo/metabolismo , Hierro/química , Oryza/metabolismo , Fósforo/análisis , Fósforo/farmacología , Contaminantes del Suelo/análisis
11.
Toxicol In Vitro ; 58: 13-25, 2019 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-30878698

RESUMEN

Cancer is a leading cause of human mortality around the globe. In this study, mechanism-based SAR (Structure-Activity Relationship) was employed to investigate the carcinogenicity of aromatic amines and nitroaromatics based on CPDB. Principal component analysis and cluster analysis were used to construct the SAR model. Principle component analysis generated three principal components from 12 mechanism-based descriptors. The extracted principal components were later used for cluster analysis, which divided the selected 55 chemicals into six clusters. The three principal components were proposed to describe the "transport", "reactivity" and "electrophilicity" properties of the chemicals. Cluster analysis indicated that the relevant "transport" properties positively correlated with the carcinogenic potential and were contributing factors in determining the carcinogenicity of the studied chemicals. The mechanism-based SAR analysis suggested the electron donating groups, electron withdrawing groups and planarity are significant factors in determining the carcinogenic potency for studied aromatic compounds. The present study may provide insights into the relationship between the three proposed properties and the carcinogenesis of aromatic amines and nitroaromatics.


Asunto(s)
Aminas/toxicidad , Carcinógenos/toxicidad , Hidrocarburos Aromáticos/toxicidad , Nitrocompuestos/toxicidad , Aminas/química , Animales , Carcinógenos/química , Análisis por Conglomerados , Hidrocarburos Aromáticos/química , Neoplasias/inducido químicamente , Nitrocompuestos/química , Análisis de Componente Principal , Ratas , Relación Estructura-Actividad
12.
Waste Manag ; 77: 252-267, 2018 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-29705047

RESUMEN

China has become the largest generator of municipal solid waste (MSW) in the world with its rapid urbanization, population growth and raising living standard. Among diverse solid waste disposal technologies, MSW incineration has been becoming an attractive choice. In terms of systematic point, an integrated MSW incineration system should include an incineration subsystem and a bottom ash (BA) disposal subsystem. This paper employed an extend emergy assessment method with several improved indicators, which considers the emissions' impact, to evaluate the comprehensive performances of an integrated MSW incineration system. One existing incineration plant in Yibin City, Sichuan Province, China, as a case study, is evaluated using the proposed method. Three alternative scenarios (scenario A: the incineration subsystem + the BA landfill subsystem; scenario B: the incineration subsystem + the concrete paving brick production subsystem using BA as raw material; scenario C: the incineration subsystem + the non-burnt wall brick production subsystem using BA as raw material) were compared. The study results reveal that the ratio of positive output is 1.225, 2.861 and 1.230, the improved environmental loading ratio is 2.715, 2.742 and 1.533, and the improved environmental sustainability index is 0.451, 1.043 and 0.803 for scenario A, B and C respectively. Therefore, reuse of BA can enhance the sustainability level of this integrated system greatly. Comparatively, scenario B has the best comprehensive performance among the three scenarios. Finally, some targeted recommendations are put forward for decision-making.


Asunto(s)
Conservación de los Recursos Energéticos , Incineración , Residuos Sólidos , China , Eliminación de Residuos , Instalaciones de Eliminación de Residuos
13.
Food Chem Toxicol ; 112: 563-570, 2018 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-28390859

RESUMEN

A species sensitivity distribution (SSD) for engineered nanomaterials (ENMs) ranks the tested species according to their sensitivity to a certain ENM. An SSD may be used to estimate the maximum acceptable concentrations of ENMs for the purpose of environmental risk assessment. To construct SSDs for metal-based ENMs, more than 1800 laboratory derived toxicity records of metallic ENMs from >300 publications or open access scientific reports were retrieved. SSDs were developed for the metallic ENMs grouped by surface coating, size, shape, exposure duration, light exposure, and different toxicity endpoints. It was found that PVP- and sodium citrate- coatings enhance the toxicity of Ag ENMs as concluded from the relevant SSDs. For the Ag ENMs with different size ranges, differences in behavior and/or effect were only observed at high exposure concentrations. The SSDs of Ag ENMs separated by both shape and exposure duration were all nearly identical. Crustaceans were found to be the most vulnerable group to metallic ENMs. In spite of the uncertainties of the results caused by limited data quality and availability, the present study provided novel information about building SSDs for distinguished ENMs and contributes to the further development of SSDs for metal-based ENMs.


Asunto(s)
Contaminantes Ambientales/toxicidad , Nanopartículas del Metal/toxicidad , Animales , Bacterias/efectos de los fármacos , Citratos/química , Crustáceos/efectos de los fármacos , Peces , Luz , Microalgas/efectos de los fármacos , Nematodos/efectos de los fármacos , Parásitos/efectos de los fármacos , Medición de Riesgo , Citrato de Sodio , Especificidad de la Especie , Pruebas de Toxicidad , Levaduras/efectos de los fármacos
14.
Sci Total Environ ; 610-611: 1329-1335, 2018 Jan 01.
Artículo en Inglés | MEDLINE | ID: mdl-28851153

RESUMEN

Toxicity of metallic nanoparticle suspensions (NP(total)) is generally assumed to result from the combined effect of the particles present in suspensions (NP(particle)) and their released ions (NP(ion)). Evaluation and consideration of how water chemistry affects the particle-specific toxicity of NP(total) are critical for environmental risk assessment of nanoparticles. In this study, it was found that the toxicity of Cu NP(particle) to Daphnia magna, in line with the trends in toxicity for Cu NP(ion), decreased with increasing pH and with increasing concentrations of divalent cations and dissolved organic carbon (DOC). Without the addition of DOC, the toxicity of Cu NP(total) to D. magna at the LC50 was driven mainly by Cu NP(ion) (accounting for ≥53% of the observed toxicity). However, toxicity of Cu NP(total) in the presence of DOC at a concentration ranging from 5 to 50mg C/L largely resulted from the NP(particle) (57%-85%), which could be attributable to the large reduction of the concentration of Cu NP(ion) and the enhancement of the stability of Cu NP(particle) when DOC was added. Our results indicate that water chemistry needs to be explicitly taken into consideration when evaluating the role of NP(particle) and NP(ion) in the observed toxicity of NP(total).


Asunto(s)
Cobre/toxicidad , Daphnia/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua/toxicidad , Agua/química , Animales , Daphnia/fisiología
15.
Environ Pollut ; 234: 684-691, 2018 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-29227954

RESUMEN

A full-factorial test design was applied to systematically investigate the contribution and significance of water chemistry parameters (pH, divalent cations and dissolved organic carbon (DOC) concentration) and their interactions on the behavior and fate of copper nanoparticles (CuNPs). The total amount of Cu remaining in the water column after 48 h of incubation was mostly influenced by divalent cation content, DOC concentration and the interaction of divalent cations and DOC. DOC concentration was the predominant factor influencing the dissolution of CuNPs, which was far more important than the effect of pH in the range from 6 to 9 on the dissolution of the CuNPs. The addition of DOC at concentrations ranging from 5 to 50 mg C/L resulted in a 3-5 fold reduction of dissolution of CuNPs after 48 h of incubation, as compared to the case without addition of DOC. Divalent cation content was found to be the most influential factor regarding aggregation behavior of the particles, followed by DOC concentration and the interaction of divalent cations and DOC. In addition, the aggregation behavior of CuNPs rather than particulate dissolution explained most of the variance in the sedimentation profiles of CuNPs. These results are meaningful for improved understanding and prediction of the behavior and fate of metallic NPs in aqueous environments.


Asunto(s)
Cationes Bivalentes/química , Cobre/química , Monitoreo del Ambiente/métodos , Agua Dulce/química , Nanopartículas del Metal/química , Contaminantes Químicos del Agua/química , Agua/química , Carbono/química , Cobre/análisis , Concentración de Iones de Hidrógeno , Nanopartículas del Metal/análisis , Compuestos Orgánicos/química , Contaminantes Químicos del Agua/análisis
16.
Materials (Basel) ; 10(9)2017 Aug 31.
Artículo en Inglés | MEDLINE | ID: mdl-28858269

RESUMEN

Gathering required information in a fast and inexpensive way is essential for assessing the risks of engineered nanomaterials (ENMs). The extension of conventional (quantitative) structure-activity relationships ((Q)SARs) approach to nanotoxicology, i.e., nano-(Q)SARs, is a possible solution. The preliminary attempts of correlating ENMs' characteristics to the biological effects elicited by ENMs highlighted the potential applicability of (Q)SARs in the nanotoxicity field. This review discusses the current knowledge on the development of nano-(Q)SARs for metallic ENMs, on the aspects of data sources, reported nano-(Q)SARs, and mechanistic interpretation. An outlook is given on the further development of this frontier. As concluded, the used experimental data mainly concern the uptake of ENMs by different cell lines and the toxicity of ENMs to cells lines and Escherichia coli. The widely applied techniques of deriving models are linear and non-linear regressions, support vector machine, artificial neural network, k-nearest neighbors, etc. Concluded from the descriptors, surface properties of ENMs are seen as vital for the cellular uptake of ENMs; the capability of releasing ions and surface redox properties of ENMs are of importance for evaluating nanotoxicity. This review aims to present key advances in relevant nano-modeling studies and stimulate future research efforts in this quickly developing field of research.

17.
Int J Mol Sci ; 18(7)2017 Jul 12.
Artículo en Inglés | MEDLINE | ID: mdl-28704975

RESUMEN

As listed by the European Chemicals Agency, the three elements in evaluating the hazards of engineered nanomaterials (ENMs) include the integration and evaluation of toxicity data, categorization and labeling of ENMs, and derivation of hazard threshold levels for human health and the environment. Assessing the hazards of ENMs solely based on laboratory tests is time-consuming, resource intensive, and constrained by ethical considerations. The adoption of computational toxicology into this task has recently become a priority. Alternative approaches such as (quantitative) structure-activity relationships ((Q)SAR) and read-across are of significant help in predicting nanotoxicity and filling data gaps, and in classifying the hazards of ENMs to individual species. Thereupon, the species sensitivity distribution (SSD) approach is able to serve the establishment of ENM hazard thresholds sufficiently protecting the ecosystem. This article critically reviews the current knowledge on the development of in silico models in predicting and classifying the hazard of metallic ENMs, and the development of SSDs for metallic ENMs. Further discussion includes the significance of well-curated experimental datasets and the interpretation of toxicity mechanisms of metallic ENMs based on reported models. An outlook is also given on future directions of research in this frontier.


Asunto(s)
Ecosistema , Nanoestructuras/química , Toxicología/métodos , Biología Computacional , Relación Estructura-Actividad Cuantitativa
18.
Sci Total Environ ; 563-564: 81-8, 2016 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-27135569

RESUMEN

Although the risks of metallic nanoparticles (NPs) to aquatic organisms have already been studied for >10years, our understanding of the link between the fate of particles in exposure medium and their toxicity is still in its infancy. Moreover, most of the earlier studies did not distinguish the contribution of particles and soluble ions to the toxic effects caused by suspensions of metallic NPs. In this study, the toxicity of CuNPs to Daphnia magna upon modification of the exposure conditions, achieved by aging the suspensions of CuNPs and by altering water chemistry parameters like the pH and levels of dissolved organic carbon (DOC), was investigated. The LC50 values for CuNPs exposure decreased by about 30% after 7days of aging. The LC50 values increased >12-fold upon addition of DOC at concentrations ranging from 0 to 10mg/L to the exposure medium. Changing the pH from 6.5 to 8.5 resulted in a 3-fold higher LC50 value. Furthermore, it was found that during 7days of aging of the exposure medium (without addition of DOC and at pH7.8), the toxicity could be mostly ascribed to the particles present in the suspension (around 70%). However, adding DOC or decreasing the pH of the exposure medium reduced the contribution of the particles to the observed toxicity. We thus found that the effective concentration regarding the toxicity was mainly driven by the contribution of the soluble ions in the presence of DOC or at pH6.5. Our results suggest that the toxicity results of CuNPs obtained from laboratory tests may overestimate the risk of the particles in polluted waters due to the common absence of DOC in laboratory test solutions. Moreover, the role of the ions shedding from CuNPs is very important in explaining the toxicity in natural waters.


Asunto(s)
Cobre/toxicidad , Daphnia/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Carbono/análisis , Concentración de Iones de Hidrógeno , Iones/metabolismo , Pruebas de Toxicidad
19.
Environ Sci Technol ; 49(7): 4657-64, 2015 Apr 07.
Artículo en Inglés | MEDLINE | ID: mdl-25785366

RESUMEN

There is increasing recognition that the wide use of nanoparticles, such as Cu (CuNPs) and ZnO nanoparticles (ZnONPs), may pose risks to the environment. Currently there is insufficient insight in the contribution of metal-based nanoparticles and their dissolved ions to the overall toxicity and accumulation. To fill in this gap, we combined the fate assessment of CuNPs and ZnONPs in aquatic test media with the assessment of toxicity and accumulation of ions and particles present in the suspensions. It was found that at the LC50 level of Daphnia magna exposed to the nanoparticle suspensions, the relative contributions of ions released from CuNPs and ZnONPs to toxicity were around 26% and 31%, respectively, indicating that particles rather than the dissolved ions were the major source of toxicity. It was additionally found that at the low exposure concentrations of CuNPs and ZnONPs (below 0.05 and 0.5 mg/L, respectively) the dissolved ions were predominantly accumulated, whereas at the high exposure concentrations (above 0.1 mg/L and 1 mg/L, respectively), particles rather than the released ions played a dominant role in the accumulation process. Our results thus suggest that consideration on the contribution of dissolved ions to nanoparticle toxicity needs to be interpreted with care.


Asunto(s)
Cobre , Daphnia/efectos de los fármacos , Daphnia/metabolismo , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua , Óxido de Zinc , Animales , Cobre/metabolismo , Cobre/toxicidad , Contaminantes Químicos del Agua/metabolismo , Contaminantes Químicos del Agua/toxicidad , Óxido de Zinc/metabolismo , Óxido de Zinc/toxicidad
20.
PLoS One ; 9(2): e88752, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-24551152

RESUMEN

BACKGROUND: Forest litter decomposition is a major component of the global carbon (C) budget, and is greatly affected by the atmospheric nitrogen (N) deposition observed globally. However, the effects of N addition on forest litter decomposition, in ecosystems receiving increasingly higher levels of ambient N deposition, are poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: We conducted a two-year field experiment in five forests along the western edge of the Sichuan Basin in China, where atmospheric N deposition was up to 82-114 kg N ha(-1) in the study sites. Four levels of N treatments were applied: (1) control (no N added), (2) low-N (50 kg N ha(-1) year(-1)), (3) medium-N (150 kg N ha(-1) year(-1)), and (4) high-N (300 kg N ha(-1) year(-1)), N additions ranging from 40% to 370% of ambient N deposition. The decomposition processes of ten types of forest litters were then studied. Nitrogen additions significantly decreased the decomposition rates of six types of forest litters. N additions decreased forest litter decomposition, and the mass of residual litter was closely correlated to residual lignin during the decomposition process over the study period. The inhibitory effect of N addition on litter decomposition can be primarily explained by the inhibition of lignin decomposition by exogenous inorganic N. The overall decomposition rate of ten investigated substrates exhibited a significant negative linear relationship with initial tissue C/N and lignin/N, and significant positive relationships with initial tissue K and N concentrations; these relationships exhibited linear and logarithmic curves, respectively. CONCLUSIONS/SIGNIFICANCE: This study suggests that the expected progressive increases in N deposition may have a potential important impact on forest litter decomposition in the study area in the presence of high levels of ambient N deposition.


Asunto(s)
Nitrógeno/metabolismo , Nitrógeno/farmacología , Hojas de la Planta/fisiología , Árboles/fisiología , China , Ecosistema , Lignina/metabolismo , Hojas de la Planta/efectos de los fármacos , Lluvia
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