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1.
Ecotoxicol Environ Saf ; 174: 584-591, 2019 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-30870659

RESUMO

Single and multispecies algal bioassays were assessed using copper toxicity with three green algae (Scenedesmus subspicatus, Scenedesmus quadricauda and Ankistrodesmus angustus) and one blue-green algae species (Oscillatoria prolifera). Single and multispecies toxicity tests were conducted based on cell density as per standard toxicity testing, and on equivalent surface area. A higher copper sulfate toxicity was registered for O. prolifera, followed by S. subspicatus, S. quadricauda, and A. angustus in single-species toxicity tests based on cell density. Single species toxicity tests based on surface area showed increased copper toxicity with increasing algal surface area except for A. angustus. In multispecies control bioassays, the growth of A. angustus was inhibited in the presence of other species in surface area-based tests. As compared to single species bioassays, O. prolifera, and S. quadricauda showed a decreased sensitivity to copper sulfate in both cell density and surface area based multispecies tests. However, for the algae species with the smallest surface area, S. subspicatus, 96h-EC50 value decreased in multispecies bioassays based on surface area as compared to the single species test, while it increased in multispecies bioassays based on cell density. The difference in S. subspicatus sensitivity to copper between tests based on cell density and surface area supports the need to adopt multispecies toxicity testing based on surface area to avoid the confounding effect on copper toxicity of increased biomass for metal binding. 96h-EC50 values for all species combined in the multispecies test based on cell density and on surface area were significantly different from 96h-EC50 values obtained in single species bioassays. These results demonstrate that single-species bioassays may over- or underestimate metal toxicity in natural waters.


Assuntos
Clorófitas/efeitos dos fármacos , Sulfato de Cobre/toxicidade , Herbicidas/toxicidade , Bioensaio , Contagem de Células , Clorófitas/citologia , Clorófitas/crescimento & desenvolvimento , Cianobactérias/citologia , Cianobactérias/efeitos dos fármacos , Cianobactérias/crescimento & desenvolvimento , Scenedesmus/citologia , Scenedesmus/efeitos dos fármacos , Scenedesmus/crescimento & desenvolvimento , Testes de Toxicidade
2.
Molecules ; 23(10)2018 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-30332752

RESUMO

Binderless zeolite macrostructures in the form of ZK-4 microspheres were prepared using anion-exchange resin beads as shape-directing macrotemplates. The particles were synthesized under hydrothermal conditions at different temperatures and treatment times. The influence of the different synthesis parameters was investigated by X-ray diffraction, scanning electron microscopy, fluorescence X, nitrogen adsorption measurements and 29Si solid-state NMR. Fully crystalline spheres similar in size and shape to the original resin beads were obtained by a hydrothermal treatment at the highest temperatures (150⁻180 °C) for a short treatment time of 24 h. The synthesized microspheres showed to be promising in the molecular decontamination of volatile organic compounds (VOCs).


Assuntos
Compostos Orgânicos Voláteis/análise , Zeolitas/síntese química , Adsorção , Descontaminação , Temperatura Alta , Microscopia Eletrônica de Varredura , Microesferas , Tamanho da Partícula , Difração de Raios X , Zeolitas/química
3.
Sci Total Environ ; 637-638: 1230-1240, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-29801216

RESUMO

In this study, a method for assessing the costs of biodiesel production from waste frying oils in Beirut, Lebanon, was investigated with the aim of developing an economic evaluation of this alternative. A hundred restaurant and hotel enterprises in Beirut were surveyed for promoting them in participating in the biodiesel supply chain, and for data collection on waste frying oils generation, disposal methods and frequency, and acquisition cost. Also, waste frying oils were collected and converted into biodiesel using a one-step base catalyzed transesterification process. Physicochemical characteristics of the produced biodiesel were conforming to international standards. Data produced from laboratory scale conversion of waste frying oils to biodiesel, as well as data collected from the only biodiesel plant in Lebanon was used to determine the production cost of biodiesel. Geographic Information System was used to propose a real-time vehicle routing model to establish the logistics costs associated with waste frying oils collection. Comparing scenarios of the configuration collection network of waste frying oils, and using medium-duty commercial vehicles for collection, a logistics cost of US$/L 0.08 was optimally reached. For the calculation of the total cost of biodiesel production, the minimum, average, and maximum values for the non-fixed cost variables were considered emerging 81 scenarios for possible biodiesel costs. These were compared with information on the commercialization of diesel in Lebanon for the years 2011 through 2017. Although competitive with petroleum diesel for years 2011 to 2014, the total biodiesel cost presented less tolerance to declining diesel prices in the recent years. Sensitivity analysis demonstrated that the acquisition cost of waste frying oils is the key factor affecting the overall cost of biodiesel production. The results of this study validate the economic feasibility of waste frying oils' biodiesel production in the studied urban area upon enforcement of low waste frying oils' acquisition costs, and can help spur food service enterprises to become suppliers of biodiesel production feedstock and support a healthy development of the biodiesel industry in Lebanon.

4.
Ecotoxicol Environ Saf ; 155: 59-65, 2018 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-29505982

RESUMO

Studies of metal toxicity to microalgae have predominantly been conducted using single non-target algae species and without due regard for the chemistry of the treated waters, leading to ineffective or excessive algaecide treatments. In this study, indigenous multi-algal species (Scenedesmus quadricauda, and Scenedesmus subspicatus and Oscillatoria agardhii) were used in laboratory toxicity bioassays under simulated field water chemistry (pH = 7.2, hardness = 196 mg L-1 as CaCO3, and alkalinity = 222 mg L-1 as CaCO3) to determine the optimum copper sulfate treatment dose to control algae growth in an irrigation canal. Toxicity bioassays were conducted using copper sulfate in chelated (with EDTA) and non-chelated (without EDTA) forms to assess the influence of the use of synthetic chelators in toxicity studies. Also, copper toxicity to the indigenous algae species was measured in the non-modified EPA test medium (pH = 7.5, hardness = 92 mg L-1 as CaCO3, alkalinity = 10 mg L-1 as CaCO3 and EDTA= 300 µg L-1) to assess the impact of the water chemistry on algae inhibitory algal dosages. Under simulated water chemistry conditions, lower toxicity was measured in the test flasks with the chelated form of copper (96 h- EC50= 386.67 µg L-1 as Cu) as compared to those with the non-chelated metal (96 h-EC50= 217.17 µg L-1 as Cu). In addition, higher copper toxicity was measured in the test flasks prepared with the non-modified EPA medium using chelated copper (96 h-EC50 = 65.93 µg L-1 as Cu) as compared to their analogous microcosms with modified water chemistry (96 h-EC50= 386.67 µg L-1 as Cu), the increased water hardness and alkalinity in the latter case contributing to the decrease of the metal bioavailability. Results from laboratory experiments showed good correlation with copper dosages used in a small scale field testing to control algae growth, increasing confidence in laboratory bioassays.


Assuntos
Clorófitas/efeitos dos fármacos , Sulfato de Cobre/toxicidade , Herbicidas/toxicidade , Testes de Toxicidade , Bioensaio , Quelantes de Cálcio , Cianobactérias/efeitos dos fármacos , Ácido Edético , Água/química
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