Characterization of the effluent from a nanosilver producing washing machine

The increasing number of nanomaterial based consumer products raises concerns about their possible impact on the environment. This study provides an assessment of the effluent from a commercially available silver nanowashing machine. The washing machine released silver in its effluent at an average concentration of 11μgL(-1), as determined by inductive coupled mass spectrometry (ICP-MS). The presence of silver nanoparticles (AgNPs) was confirmed by single particle ICP-MS as well as ion selective electrode measurements and filtration techniques. Size measurements showed particles to be in the defined nanosize range, with an average size of 10nm measured with transmission electron microscopy (TEM) and 60-100nm determined with nanoparticle tracking analysis (NTA). The effluent was shown to have negative effects on a natural bacterial community as its abundance was clearly reduced when exposed to the nanowash water. If washing machines capable of producing AgNPs become a common feature of households in the future, wastewater will contain significant loadings of AgNPs which might be released into the environment.     

New kind of polarotaxis governed by degree of polarization: attraction of tabanid flies to differently polarizing host animals and water surfaces

Aquatic insects find their habitat from a remote distance by means of horizontal polarization of light reflected from the water surface. This kind of positive polarotaxis is governed by the horizontal direction of polarization (E-vector). Tabanid flies also detect water by this kind of polarotaxis. The host choice of blood-sucking female tabanids is partly governed by the linear polarization of light reflected from the host’s coat. Since the coat-reflected light is not always horizontally polarized, host finding by female tabanids may be different from the established horizontal E-vector polarotaxis. To reveal the optical cue of the former polarotaxis, we performed choice experiments in the field with tabanid flies using aerial and ground-based visual targets with different degrees and directions of polarization. We observed a new kind of polarotaxis being governed by the degree of polarization rather than the E-vector direction of reflected light. We show here that female and male tabanids use polarotaxis governed by the horizontal E-vector to find water, while polarotaxis based on the degree of polarization serves host finding by female tabanids. As a practical by-product of our studies, we explain the enigmatic attractiveness of shiny black spheres used in canopy traps to catch tabanids.     

Relative efficacy of intrinsic and extant parameters for modeling biodegradation of synthetic organic compounds in activated sludge: dynamic systems.

The utility of intrinsic and extant kinetic parameters for simulating the dynamic behavior of a biotreatment system coupled with a distributed, unstructured, balanced microbial growth model were evaluated against the observed response of test reactors to transient loads of synthetic organic compounds (SOCs). Biomass from a completely mixed activated-sludge (CMAS) system was tested in fed-batch reactors, while a sequencing batch reactor (SBR) was tested by measuring SOC concentrations during the fill and react period. Both the CMAS system and the SBR were acclimated to a feed containing biogenic substrates and several SOCs, and the transient loading tests were conducted with biogenic substrates along with one or more SOCs. Extant parameters more closely reflect the steady-state degradative capacity of activated-sludge biomass than intrinsic parameters and, hence, were expected to be better predictors of system performance. However, neither extant nor intrinsic parameters accurately predicted system response and neither parameter set was consistently superior to the other. Factors that may have contributed to the inability of the model to predict system response were identified and discussed. These factors included the role of abiotic processes in SOC removal, disparity in the bases used to evaluate parameter estimates (substrate mineralization) and reactor performance (substrate disappearance), inhibitory substrate interactions under the severe loading conditions of the SBR, changes in the physiological state of the biomass during the transient loading tests, and the presumed correlation between the competent biomass concentration and the influent SOC concentration.