Showing papers on "Water environment published in 2011"

Advances in Heterogeneous Photocatalytic Degradation of Phenols and Dyes in Wastewater: A Review

Abstract: The heterogeneous photocatalytic water purification process has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible light spectrum. This paper aims to review and summarize the recently published works in the field of photocatalytic oxidation of toxic organic compounds such as phenols and dyes, predominant in wastewater effluent. In this review, the effects of various operating parameters on the photocatalytic degradation of phenols and dyes are presented. Recent findings suggested that different parameters, such as type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, mode of catalyst application, and calcinations temperature can play an important role on the photocatalytic degradation of organic compounds in water environment. Extensive research has focused on the enhancement of photocatalysis by modification of TiO2 employing metal, non-metal, and ion doping. Recent advances in TiO2 photocatalysis for the degradation of various phenols and dyes are also highlighted in this review.

Advances in heterogeneous photocatalytic degradation of phenols and dyes in wastewater : a review

Abstract: The heterogeneous photocatalytic water purification process has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible light spectrum. This paper aims to review and summarize the recently published works in the field of photocatalytic oxidation of toxic organic compounds such as phenols and dyes, predominant in waste water effluent. In this review, the effects of various operating parameters on the photocatalytic degradation of phenols and dyes are presented. Recent findings suggested that different parameters, such as type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, mode of catalyst application, and calcinations temperature can play an important role on the photocatlytic degradation of organic compounds in water environment. Extensive research has focused on the enhancement of photocatalysis by modification of TiO2 employing metal, non-metal and ion doping. Recent advances in TiO2 photocatalysis for the degradation of various phenols and dyes are also highlighted in this review.

Ecological mechanisms underlying the sustainability of the agricultural heritage rice–fish coculture system

Abstract: For centuries, traditional agricultural systems have contributed to food and livelihood security throughout the world Recognizing the ecological legacy in the traditional agricultural systems may help us develop novel sustainable agriculture We examine how rice–fish coculture (RF), which has been designated a “globally important agricultural heritage system,” has been maintained for over 1,200 y in south China A field survey demonstrated that although rice yield and rice-yield stability are similar in RF and rice monoculture (RM), RF requires 68% less pesticide and 24% less chemical fertilizer than RM A field experiment confirmed this result We documented that a mutually beneficial relationship between rice and fish develops in RF: Fish reduce rice pests and rice favors fish by moderating the water environment This positive relationship between rice and fish reduces the need for pesticides in RF Our results also indicate a complementary use of nitrogen (N) between rice and fish in RF, resulting in low N fertilizer application and low N release into the environment These findings provide unique insights into how positive interactions and complementary use of resource between species generate emergent ecosystem properties and how modern agricultural systems might be improved by exploiting synergies between species

Micronucleus assay in aquatic animals

Abstract: Aquatic pollutants produce multiple consequences at organism, population, community and ecosystem level, affecting organ function, reproductive status, population size, species survival and thus biodiversity Among these, carcinogenic and mutagenic compounds are the most dangerous as their effects may exert a damage beyond that of individual and may be active through several generations The application of genotoxicity biomarkers in sentinel organisms allows for the assessment of mutagenic hazards and/or for the identification of the sources and fate of the contaminants Micronucleus (MN) test as an index of accumulated genetic damage during the lifespan of the cells is one of the most suitable techniques to identify integrated response to the complex mixture of contaminants MN assay is today widely applied in a large number of wild and transplanted aquatic species The large majority of studies or programmes on the genotoxic effect of the polluted water environment have been carried out with the use of bivalves and fish Haemocytes and gill cells are the target tissues most frequently considered for the MN determination in bivalves The MN test was widely validated and was successfully applied in a large number of field studies using bivalves from the genera Mytilus MN in fish can be visualised in different cell types: erythrocytes and gill, kidney, hepatic and fin cells The use of peripheral erythrocytes is more widely used because it avoids the complex cell preparation and the killing of the animals The MN test in fish erythrocytes was validated in laboratory with different species after exposure to a large number of genotoxic agents The erythrocyte MN test in fish was also widely and frequently applied for genotoxicity assessment of freshwater and marine environment in situ using native or caged animals following different periods of exposure Large interspecies differences in sensitivity for MN induction were observed Further validation studies are needed in order to better characterise the different types of nuclear alterations and to clarify the role of biotic and abiotic factors in interspecies and inter-individual variability

The Water Environment: Algal Toxins And Health

Abstract: I. Review of Toxic Algae.- Freshwater Blue-green Algae (Cyanobacteria) Toxins - A Review.- Toxins from Marine Blue-green Algae.- Poisons Produced by Dinoflagellates - A Review.- The Toxic Principles of Prymnesium parvum.- II. Occurrence and Ecology of Toxic Cyanobacteria.- Studies on the Ecology, Growth and Physiology of Toxic Microcystis aeruginosa in South Africa.- Autecological Studies on Microcystis.- Is a Plasmid(s) Involved in the Toxicity of Microcystis aeruginosa?.- A Toxic Bloom of Anabaena flos-aquae in Hebgen Reservoir Montana in 1977.- Morphology of Toxic versus Non-Toxic Strains of Aphanizomenon flos-aquae.- The Occurrence of Toxic Cyanophyte Blooms in Australia.- The Recent Blue-green Algal Blooms of Long Lake, Washington.- The Mosaic Nature of Toxic Blooms of Cyanobacteria.- III. Culturing Methods and Reports of New Toxic Species.- Collection, Purification, and Culture of Cyanobacteria.- Culture of Planktonic Cyanophytes on Agar.- The Effect of Physico-chemical Factors on Growth Relevant to Mass Culture of Axenic Microcystis.- Preliminary Tests of Toxicity of Synechocystis sp. Grown on Wastewater Medium.- Chemical Nature and Mode of Action of a Toxin from Pandorina morum.- IV. Public Health and Toxic Cyanobacteria.- Water-Associated Human Illness in Northeast Pennsylvania and Its Suspected Association with Blue-green Algae Blooms.- Some Aspects Concerning Remote After-effects of Blue-green Algae Toxin Impact on Warm-blooded Animals.- Temporal Association between an Algal Bloom and Mutagenicity in a Water Reservoir.- Cyanobacteria and Endotoxins in Drinking Water Supplies.- Potential for Groundwater Contamination by Algal Endotoxins.- V. Isolation, Physiology, Toxicology and Detection of Cyanobacteria Toxins.- Toxicity Studies with Blue-green Algae from Norwegian Inland Waters.- Isolation, Characterization and Pathology of the Toxin from the Blue-green Alga Microcystis aeruginosa.- Toxicological Studies on Microcystis.- Effects of a Hepatic Toxin from the Cyanophyte Microcystis aeruginosa.- Studies on Aphantoxin from Aphanizomenon flos-aquae in New Hampshire.- Chemical Studies on Toxins from the Blue-green Alga Aphanizomenon flos-aquae.- Studies on the Fluorometric Determination of the Toxins of the Blue-green Alga Aphanizomenon flos-aquae.- A Fluorometric Technique for the Detection and Determination of Paralytic Shellfish Poisons.- Simplified Monitoring of Anatoxin-A by Reverse-Phase High Performance Liquid Chromatography and the Sub-acute Effects of Anatoxin-A in Rats.- Isolation and Characterization of Endotoxin from Cyanobacteria (Blue-green Algae).- Directory to the Literature on Toxic Cyanobacteria (Blue-green Algae).- List of Contributors.

Detection of three virulence genes alt, ahp and aerA in Aeromonas hydrophila and their relationship with actual virulence to zebrafish.

Abstract: Aims: To evaluate the frequency of the aerolysin (aerA), cytotoxic enterotoxin (alt) and serine protease (ahp) genes in Aeromonas hydrophila isolates from different sources, and to determine the relationship between the presence of these genes and virulence of A. hydrophila in zebrafish. Methods and Results: Aeromonas hydrophila isolates from clinical cases (n = 40), from healthy fish (n = 22) and from water environment (n = 21) were analysed with respect to the prevalence of aerA, alt and ahp genes by PCR assay. These virulence factors occur among clinical isolates as well as among isolates from healthy fish and water environment. The majority (97·6%) of the strains examined carried one or more virulence genes. The isolates were divided into seven genetic profiles on the basis of PCR result: aerA+alt+ahp+ (62·7%), aerA+alt+ahp− (13·3%), aerA+alt−ahp+ (10·8%), aerA−alt+ahp+ (4·8%), aerA−alt−ahp+ (3·6%), aerA+alt−ahp− (2·4%) and aerA−alt−ahp− (2·4%). A higher frequency of genetic group aerA+alt+ahp+ was determined in the isolates from diseased animals compared to those from healthy fish or water environments. Virulence properties of 26 representative strains belonging to the seven genetic profiles were further characterized. Results demonstrated that as the present of virulence genes increased, the proteolytic, haemolytic and cytotoxic activities of extracellular products also increased. And the 50% lethal doses (LD50s) of aerA+alt+ahp+ isolates ( 106). Conclusions: Virulence properties of A. hydrophila correlated well with the presence of virulence genes tested. aerA+alt+ahp+ was more frequent virulence genotype in A. hydrophila isolates from clinical diseases than from healthy fish and water environment, and the aerA+alt+ahp+ isolates were more virulent to zebrafish compared to the other six genetic profiles. Significant and Impact of the Study: The detection for aerA, alt and ahp can be used for virulence typing of A. hydrophila isolates.

Simulating Dye-Sensitized TiO2 Heterointerfaces in Explicit Solvent: Absorption Spectra, Energy Levels, and Dye Desorption

Abstract: Dye-sensitized solar cells (DSCs) represent a valuable, efficient, and low-cost alternative to conventional semiconductor photovoltaic devices. A deeper understanding of the dye/semiconductor heterointerface and of the dye-sensitized semiconductor/electrolyte interactions are fundamental for further progress in DSC technology. Here we report an ab initio molecular dynamics simulation of a dye-sensitized TiO2 heterointerface “immersed” in an explicit water environment for an efficient organic dye, followed by TDDFT excited state calculations of the coupled dye/semiconductor/solvent system. This new computational protocol and the extended model system allows us to gain unprecedented insight into the excited state changes occurring for the solvated dye-sensitized heterointerface at room temperature, and to provide an atomistic picture of water-mediated dye desorption.

Influence of parameters on the heterogeneous photocatalytic degradation of pesticides and phenolic contaminants in wastewater : a short review

Abstract: In recent years, the application of heterogeneous photocatalytic water purification process has gained wide attention due to its effectiveness in degrading and mineralizing the recalcitrant organic compounds as well as the possibility of utilizing the solar UV and visible light spectrum. This paper aims to review and summarize the recently published works on the titanium dioxide (TiO2) photocatalytic oxidation of pesticides and phenolic compounds, predominant in storm and waste water effluents. The effect of various operating parameters on the photocatalytic degradation of pesticides and phenols are discussed. Results reported here suggested that the photocatalytic degradation of organic compounds depends on the type of photocatalyst and composition, light intensity, initial substrate concentration, amount of catalyst, pH of the reaction medium, ionic components in water, solvent types, oxidizing agents/electron acceptors, catalyst application mode, and calcinations temperature in water environment. A substantial amount of research has focused on the enhancement of TiO2 photocatalysis by modification with metal, non-metal and ion doping. Recent developments in TiO2 photocatalysis for the degradation of various pesticides and phenols are also highlighted in this review. It is evident from the literature survey that photocatalysis has shown good potential for the removal of various organic pollutants. However, still there is a need to find out the practical utility of this technique on commercial scale.

Micellar carrier for triplet-triplet annihilation-assisted photon energy upconversion in a water environment

Abstract: In this paper, we demonstrate energetically conjoined triplet?triplet annihilation-assisted photon energy upconversion (UC) operating in an aqueous environment. Obtained micellar structures show very efficient UC emission in a water environment under extremely low excitation light intensity, down to 10?mW?cm?2. The demonstrated sub-linear intensity dependence of the UC emission is of crucial importance for life science applications, allowing upconverted photons to be generated even at low intensity that then serve as a local, in situ, optical excitation source for subsequent light-triggered processes.

Phytoplankton in Estonian coastal waters – variability, trends and response to environmental pressures

Abstract: Muutused futoplanktoni kui mere okosusteemi uhe aluskomponendi koosseisus kutsuvad esile nii struktuurseid kui funktsionaalseid nihkeid toiduahela jargmistes lulides. Toos on analuusitud Eesti rannikumere erinevatest osadest kogutud seireandmeid 1990-ndate algusest kuni praeguseni. Saadud tulemused fikseerivad futoplanktoni sesoonse dunaamika pohijooned. Futoplanktoni liigilise koosseisu aastatevahelist ja sesoonisisest varieeruvust seletatavad uhelt poolt ilmastikutingimusted ning teiselt poolt vee toitainetesisaldus. Temperatuur ja soolsus on peamised tegurid, mis kujundavad Laanemere, sealhulgas Soome lahe futoplanktoni koosluste struktuuri ja levikut. Luhikesel ajaskaalal on looduslike ja inimtekkeliste protsesside osakaalu maaramine futoplanktoni dunaamikas keeruline, sest pusivama iseloomuga muutused leiavad aset jark-jargult ning isegi moodukas toitainetesisalduse kasv peegeldub liigilises koosseisus vahemargatavalt. Futoplanktoni ajalis-ruumiline varieeruvus tingib, et sesoonseid muutusi tuleb jalgida voimalikult vaikese ajasammuga, ent samas vaatluste ja analuusikulusid moistlikul tasemel hoides. Traditsiooniliste meetodite korval saab seiret tohustada kommertsalustele paigaldatud jarelvalveta mootmis- ja proovikogumissusteemide abil. Teadmised futoplanktoni koosluste suktsessiooni ja uksikute liikide ajalis-ruumilist dunaamika kohta voimaldavad anda soovitusi seiresageduse optimeerimiseks, arvestades vetikaoitsengute esinemise ajalisi mustreid ja oitsenguvaheliste perioodide suuremat stabiilsust koosluse struktuuris. Pakutakse valja potentsiaalsed uued keskkonnaseisundi indikaatorid Laanemere pohjaosa jaoks.; Changes in phytoplankton composition may reflect structural and functional ecosystem shifts. In this thesis, the general patterns of seasonal dynamics in four areas of Estonian operational phytoplankton monitoring have been demonstrated. All data are linked to spatial distributions of abiotic parameters and the results are discussed in relation to present and future environmental challenges to the Baltic Sea. Temperature and salinity are the main factors shaping the phytoplankton communities in the Gulf of Finland. Most of the statistically significant changes over the study period (1993–2010) have been related to increases in the mean seasonal or monthly biomass values at different taxo¬nomic levels. Measuring seasonal changes and inter-annual variability requires extensive sampling efforts. The optimal sampling frequency for the northern parts of the Baltic Sea has been discussed and alternative methods of phytoplankton monitoring introduced. Although phytoplankton biomass and species composition are influenced by different mechanisms, the impact of climate change may be overwhelming in the future and induce changes at higher trophic levels. Therefore it is important to maintain long-term biological monitoring programs to assess the biological response to both relatively slow processes and short-term events in water environment. Phytoplankton is also determined as one of the biological quality…

Molecular dynamics simulations of the adsorption of bone morphogenetic protein-2 on surfaces with medical relevance.

Abstract: Bone morphogenetic protein-2 (BMP-2) plays a crucial role in osteoblast differentiation and proliferation. Its effective therapeutic use for ectopic bone and cartilage regeneration depends, among other factors, on the interaction with the carrier at the implant site. In this study, we used classical molecular dynamics (MD) and a hybrid approach of steered molecular dynamics (SMD) combined with MD simulations to investigate the initial stages of the adsorption of BMP-2 when approaching two implant surfaces, hydrophobic graphite and hydrophilic titanium dioxide rutile. Surface adsorption was evaluated for six different orientations of the protein, two end-on and four side-on, in explicit water environment. On graphite, we observed a weak but stable adsorption. Depending on the initial orientation, hydrophobic patches as well as flexible loops of the protein were involved in the interaction with graphite. On the contrary, BMP-2 adsorbed only loosely to hydrophilic titanium dioxide. Despite a favorable intera...

Structural and Binding Analysis of Pyrimidinol Carboxylic Acid and N-Hydroxy Quinazolinedione HIV-1 RNase H Inhibitors

Abstract: HIV-1 RNase H breaks down the intermediate RNA-DNA hybrids during reverse transcription, requiring two divalent metal ions for activity. Pyrimidinol carboxylic acid and N-hydroxy quinazolinedione inhibitors were designed to coordinate the two metal ions in the active site of RNase H. High-resolution (1.4 A to 2.1 A) crystal structures were determined with the isolated RNase H domain and reverse transcriptase (RT), which permit accurate assessment of the metal and water environment at the active site. The geometry of the metal coordination suggests that the inhibitors mimic a substrate state prior to phosphodiester catalysis. Surface plasmon resonance studies confirm metal-dependent binding to RNase H and demonstrate that the inhibitors do not bind at the polymerase active site of RT. Additional evaluation of the RNase H site reveals an open protein surface with few additional interactions to optimize active-site inhibitors.

Ionization of Purine Tautomers in Nucleobases, Nucleosides, and Nucleotides: From the Gas Phase to the Aqueous Environment

Abstract: We have simulated ionization of purine nucleic acid components in the gas phase and in a water environment. The vertical and adiabatic ionization processes were calculated at the PMP2/aug-cc-pVDZ level with the TDDFT method applied to obtain ionization from the deeper lying orbitals. The water environment was modeled via microsolvation approach and using a nonequilibrium polarizable continuum model. We have characterized a set of guanine tautomers and investigated nucleosides and nucleotides in different conformations. The results for guanine, i.e., the nucleic acid base with the lowest vertical ionization potential, were also compared to those for the other purine base, adenine. The main findings of our study are the following: (i) Guanine remains clearly the base with the lowest ionization energy even upon aqueous solvation. (ii) Water solvent has a strong effect on the ionization energetics of guanine and adenine and their derivatives; the vertical ionization potential (VIP) is lowered by about 1 eV for guanine while it is ∼1.5 eV higher in the nucleotides, overall resulting in similar VIPs for GMP(-), guanosine and guanine in water. (iii) Water efficiently screens the electrostatic interactions between nucleic acid components. Consequently, ionization in water always originates from the base unit of the nucleic acid and all the information about conformational state is lost in the ionization energetics. (iv) The energy splitting between ionization of the two least bound electrons increases upon solvation. (v) Tautomerism does not contribute to the width of the photoelectron spectra in water. (vi) The effect of specific short-range interactions with individual solvent molecules is negligible for purine bases, compared to the long-range dielectric effects of the aqueous medium.

Improvement in the tribological performances of Si3N4, SiC and WC by graphite-like carbon films under dry and water-lubricated sliding conditions

Abstract: Silicon nitride (Si3N4), silicon carbide (SiC) and cemented carbide (WC) are good material candidates in the applications of water hydraulic systems and related water-lubrication fields. But high friction and severe wear would arise from the unavoidable solid–solid contact during running-in period, frequent starting/stopping due to the absence of effective water lubrication. Graphite-like carbon (GLC) films with high hardness was successfully deposited on above different ceramics to improve their durability and stability under different working conditions. The microstructure, morphology and mechanical characteristics of the as-deposited GLC films were investigated by Raman spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and nano-indention tester. The tribological behaviors of GLC-coated Si3N4, SiC and WC were comparatively studied by a ball-on-disc tribo-meter when compared with un-coated ceramic substrates under both dry and water-lubricated sliding conditions. Results show that the friction coefficient of coated-GLC films kept a relatively lower value of 0.04–0.07 whereas the above three ceramic substrates demonstrated a much higher value in the range of 0.1–0.3 under both dry and water-lubricated conditions. In addition, the wear rate of Si3N4, SiC and WC substrates could be significantly reduced after the deposition of GLC films and interestingly the GLC-coated WC exhibited unique super-low wear rate (nearly non-wear properties). The tribological performance of coated-GLC films greatly depended on the ceramic substrates and the corresponding friction-reduction and anti-wear mechanisms related with different wear conditions and substrates were also revealed. Such GLC films are considered as potential protective and lubricating surfaces for water-lubricated parts such as water-lubricated bearing, mechanical seals and other moving parts used in water environment.