The focus of environmental regulations has changed significantly since the introduction of the bioassay as a standard means of assessing environmental impact.Prominent in this change is an increasing emphasis on prote...The focus of environmental regulations has changed significantly since the introduction of the bioassay as a standard means of assessing environmental impact.Prominent in this change is an increasing emphasis on protecting the integrity of natural ecosystems,which incorporate community-and system-level properties as well as organismal and population processes.Consequently,support for the use of multispecies testing has widened to include not only ecologists in academia but environmental scientists in the regulatory and industrial sector as well.The reason for this trend is clear:the additional environmental realism gained from tests utilizing communities of organisms allows for greater insight into the potential hazard of chemicals and other forms of human activity to natural ecosystems that cannot be obtained from single species tests alone.Many of the problems cited for multispecies testing early in their evolution as a hazard assessment tool have been refuted or overcome.In particular,the use of natural microbial communities minimizes several shortcomings typically associated with multispecies toxicity testing.This discussion includes the utility of microcosm and mesocosm tests using aquatic microbial communities as hazard assessment tools in conjunction with accumulating information on their performance in toxicity testing protocols.An increasing body of experimental evidence supports an expansion in the use of these tests for a variety of regulatory and research purposes.A shift in research focus is needed,however,to answer remaining questions and further refine standard protocols for these valuable ecotoxicological tools.展开更多
The diffusion kinetics of a molecular probe-rhodamine B-in ternary aqueous solutions containing poly(vinyl alcohol),glycerol,and surfactants was investigated using fluorescence correlation spectroscopy and dynamic lig...The diffusion kinetics of a molecular probe-rhodamine B-in ternary aqueous solutions containing poly(vinyl alcohol),glycerol,and surfactants was investigated using fluorescence correlation spectroscopy and dynamic light scattering.We show that the diffusion characteristics of rhodamine B in such complex systems is determined by a synergistic effect of molecular crowding and intermolecular interactions between chemical species.The presence of glycerol has no noticeable impact on rhodamine B diffusion at low concentration,but significantly slows down the diffiision of rhodamine B above 3.9%(w/v)due to a dominating steric inhibition effect.Furthermore,introducing surfactants(cationic/nonionic/anionic)to the system results in a decreased diffusion coefficient of the molecular probe.In solutions containing nonionic surfactant,this can be explained by an increased crowding effect.For ternary poly(vinyl alcohol)solutions containing cationic or anionic surfactant,surfactant-polymer and surfactant-rhodamine B interactions alongside the crowding effect of the molecules slow down the overall diffiisivity of rhodamine B.The results advance our insight of molecular migration in a broad range of industrial complex formulations that incorporate multiple compounds,and highlight the importance of selecting the appropriate additives and surfactants in formulated products.展开更多
基金This manuscript and specific ex periments discussed within were sponsored,in part,by grants from The Procter&Gamble Company and the du Pont Educational Foundation,altbough the authors take full responsibility for the views ex-pressed herein.
文摘The focus of environmental regulations has changed significantly since the introduction of the bioassay as a standard means of assessing environmental impact.Prominent in this change is an increasing emphasis on protecting the integrity of natural ecosystems,which incorporate community-and system-level properties as well as organismal and population processes.Consequently,support for the use of multispecies testing has widened to include not only ecologists in academia but environmental scientists in the regulatory and industrial sector as well.The reason for this trend is clear:the additional environmental realism gained from tests utilizing communities of organisms allows for greater insight into the potential hazard of chemicals and other forms of human activity to natural ecosystems that cannot be obtained from single species tests alone.Many of the problems cited for multispecies testing early in their evolution as a hazard assessment tool have been refuted or overcome.In particular,the use of natural microbial communities minimizes several shortcomings typically associated with multispecies toxicity testing.This discussion includes the utility of microcosm and mesocosm tests using aquatic microbial communities as hazard assessment tools in conjunction with accumulating information on their performance in toxicity testing protocols.An increasing body of experimental evidence supports an expansion in the use of these tests for a variety of regulatory and research purposes.A shift in research focus is needed,however,to answer remaining questions and further refine standard protocols for these valuable ecotoxicological tools.
基金School of Chemical Engineering,University of Birmingham,and Engineering&Physical Science Research Council(EPSRC)with grant number EP/P007864/1ZJZ acknowledges an Industrial Fellowship with P&G,funded by the Royal Academy of Engineering(IF2021\100).
文摘The diffusion kinetics of a molecular probe-rhodamine B-in ternary aqueous solutions containing poly(vinyl alcohol),glycerol,and surfactants was investigated using fluorescence correlation spectroscopy and dynamic light scattering.We show that the diffusion characteristics of rhodamine B in such complex systems is determined by a synergistic effect of molecular crowding and intermolecular interactions between chemical species.The presence of glycerol has no noticeable impact on rhodamine B diffusion at low concentration,but significantly slows down the diffiision of rhodamine B above 3.9%(w/v)due to a dominating steric inhibition effect.Furthermore,introducing surfactants(cationic/nonionic/anionic)to the system results in a decreased diffusion coefficient of the molecular probe.In solutions containing nonionic surfactant,this can be explained by an increased crowding effect.For ternary poly(vinyl alcohol)solutions containing cationic or anionic surfactant,surfactant-polymer and surfactant-rhodamine B interactions alongside the crowding effect of the molecules slow down the overall diffiisivity of rhodamine B.The results advance our insight of molecular migration in a broad range of industrial complex formulations that incorporate multiple compounds,and highlight the importance of selecting the appropriate additives and surfactants in formulated products.
