202 research outputs found
Biocidal quaternary ammonium resin
Activated carbon (charcoal) and polymeric resin sorbents are widely used in the filtration and treatment of drinking water, mainly to remove dissolved organic and inorganic impurities and to improve the taste. Earlier hopes that activated carbon might "disinfect' water proved to be unfounded. The feasibility of protecting against microbial infestation in charcoal and resin beds such as those to be incorporated into total water reuse systems in spacecraft was investigated. The biocidal effect of IPCD (insoluable polymeric contact disinfectants) in combination with a representative charcoal was assessed. The ion exchange resins (IPCD) were shown to adequately protect charcoal and ion exchange beds
XRD studies of thermally stable mesoporous tungsten oxide synthesised by a templated sol-gel process from tungstic acid precursor
Role of the hyporheic heterotrophic biofilm on transformation and toxicity of pesticides
The role of heterotrophic biofilm of water–sediment interface in detoxification processes was tested in abiotic and biotic conditions under laboratory conditions. Three toxicants, a herbicide (Diuron), a fungicide (Dimethomorph) and an insecticide (Chlorpyrifos-ethyl) have been tested in water percolating into columns reproducing hyporheic sediment. The detoxification processes were tested by comparing the water quality after 18 days of percolation with and without heterotrophic biofilm. Tested concentrations were 30 mg.Lx1 of Diuron diluted in 0.1% dimethyl sulfoxide (DMSO), 2 mg.Lx1 of Dimethomorph and 0.1 mg.Lx1 of Chlorpyrifos-ethyl. To characterise the detoxification efficiency of the system, we performed genotoxicity bioassays in amphibian larvae and rotifers and measured the respiration and denitrification of sediments. Although the presence of biofilm increased the production of N-(3,4 dichlorophenyl)-N-(methyl)-urea, a metabolite of diuron, the toxicity did not decrease irrespective of the bioassay. In the presence of biofilm, Dimethomorph concentrations decreased compared with abiotic conditions, from 2 mg.Lx1 to 0.4 mg.Lx1 after 18 days of percolation. For both Dimethomorph and Chlorpyrifos-ethyl additions, assessment of detoxification level by the biofilm depended on the test used: detoxification effect was found with amphibian larvae bioassay and no detoxification was observed with the rotifer test. Heterotrophic biofilm exerts a major influence in the biochemical transformation of contaminants such as pesticides, suggesting that the interface between running water and sediment plays a role in self-purification of stream reaches
Flow management to control excessive growth of Macrophytes - An assessment based on habitat suitability modeling
Original ResearchMediterranean rivers in intensive agricultural watersheds usually display outgrowths of
macrophytes – notably alien species – due to a combination of high concentrations
of nutrients in the water runoff and low flows resulting from water abstraction for
irrigation. Standard mechanical and chemical control is used to mitigate the problems
associated with excessive growth of plant biomass: mainly less drainage capacity and
higher flood risk. However, such control measures are cost and labor-intensive and
do not present long-term efficiency. Although the high sensitivity of aquatic vegetation
to instream hydraulic conditions is well known, management approaches based on
flow management remain relatively unexplored. The aim of our study was therefore to
apply physical habitat simulation techniques promoted by the Instream Flow Incremental
Method (IFIM) to aquatic macrophytes – the first time it has been applied in this
context – in order to model shifts in habitat suitability under different flow scenarios
in the Sorraia river in central Portugal. We used this approach to test whether the risk of
invasion and channel encroachment by nuisance species can be controlled by setting
minimum annual flows. We used 960 randomly distributed survey points to analyze the
habitat suitability for the most important aquatic species (including the invasive Brazilian
milfoil Myriophyllum aquaticum, Sparganium erectum, and Potamogeton crispus) in
regard to the physical parameters ‘flow velocity,’ ‘water depth,’ and ‘substrate size’.
We chose the lowest discharge period of the year in order to assess the hydraulic
conditions while disturbances were at a low-point, thus allowing aquatic vegetation
establishment and subsistence. We then used the two-dimensional hydraulic River2D
software to model the potential habitat availability for different flow conditions based
on the site-specific habitat suitability index for each physical parameter and species.
Our results show that the growth and distribution of macrophytes in the hydrologically
stable vegetation period is primarily a function of the local physical instream condition.
Using site-specific preference curves and a two-dimensional hydraulic model, it was
possible to determine minimum annual flows that might prevent the excessive growth
and channel encroachment caused by Myriophyllum aquaticuminfo:eu-repo/semantics/publishedVersio
Uptake of Alkanes and Alcohols by Ion-Exchange Resins in Aqueous Solution
Uptake of alkane (C5 - C9) and alcohol (C4 - C7) solutes by both strong acid cation exchange resins and strong base anion exchange resins in aqueous medium has been studied. The amount of solute taken up by resins is directly proportional to the solute concentration equilibrium with resins. Hydrophobic interaction between the solute and the resin matrix appears to play an important role in the uptake phenomenon
20-Year Risks of Breast-Cancer Recurrence after Stopping Endocrine Therapy at 5 Years
The administration of endocrine therapy for 5 years substantially reduces recurrence rates during and after treatment in women with early-stage, estrogen-receptor (ER)-positive breast cancer. Extending such therapy beyond 5 years offers further protection but has additional side effects. Obtaining data on the absolute risk of subsequent distant recurrence if therapy stops at 5 years could help determine whether to extend treatment
Water nutrient concentrations in channels in relation to occurrence of aquatic plants: a case study in eastern Croatia
- …