Photo-Reactivity of Natural Dissolved Organic Matter from Fresh to Marine Waters in the Florida Everglades, USA

Natural dissolved organic matter (DOM) is the major absorber of sunlight in most natural waters and a critical component of carbon cycling in aquatic systems. The combined effect of light absorbance properties and related photo-production of reactive species are essential in determining the reactivity of DOM. Optical properties and in particular excitation–emission matrix fluorescence spectroscopy combined with parallel factor analysis (EEM-PARAFAC) have been used increasingly to track sources and fate of DOM. Here we describe studies conducted in water from two estuarine systems in the Florida Everglades, with a salinity gradient of 2 to 37 and dissolved organic carbon concentrations from 19.3 to 5.74 mg C L−1, aimed at assessing how the quantity and quality of DOM is coupled to the formation rates and steady-state concentrations of reactive species including singlet oxygen, hydroxyl radical, and the triplet excited state of DOM. These species were related to optical properties and PARAFAC components of the DOM. The formation rate and steady-state concentration of the carbonate radical was calculated in all samples. The data suggests that formation rates, particularly for singlet oxygen and hydroxyl radicals, are strongly coupled to the abundance of terrestrial humic-like substances. A decrease in singlet oxygen, hydroxyl radical, and carbonate radical formation rates and steady-state concentration along the estuarine salinity gradient was observed as the relative concentration of terrestrial humic-like DOM decreased due to mixing with microbial humic-like and protein-like DOM components, while the formation rate of triplet excited-state DOM did not change. Fluorescent DOM was also found to be more tightly coupled to reactive species generation than chromophoric DOM.

Ultrasound-assisted electrochemical treatment of wastewaters containing organic pollutants by using novel Ti/Ta2O5-SnO2 electrodes

Advanced oxidation processes (AOPs) are modern methods using reactive hydroxyl radicals for the mineralization of organic pollutants into simple inorganic compounds, such as CO2 and H2O. Among AOPs electrochemical oxidation (EO) is a method suitable for coloured and turbid wastewaters. The degradation of pollutants occurs on electrocatalytic electrodes. The majority of electrodes contain in their structure either expensive materials (diamond and Pt-group metals) or are toxic for the environment compounds (Sb or Pb). One of the main disadvantages of electrochemical method is the polarization and contamination of electrodes due to the deposition of reaction products on their surface, which results in diminishing of the process efficiency. Ultrasound combined with the electrochemical degradation process eliminates electrode contamination because of the continuous mechanical cleaning effect produced by the formation and collapse of acoustic cavitation bubbles near to the electrode surface. Moreover, high frequency ultrasound generates hydroxyl radicals at water sonolysis. Ultrasound-assisted EO is a non-selective method for oxidation of different organic compounds with high degradation efficiencies. The aim of this research was to develop novel sustainable and cost-effective electrodes working as electrocatalysts and test their activity in electrocatalytic oxidation of organic compounds such as dyes and organic acids. Moreover, the goal of the research was to enhance the efficiency of electrocatalytic degradation processes by assisting it with ultrasound in order to eliminate the main drawbacks of a single electrochemical oxidation such as electrodes polarization and passivation. Novel Ti/Ta2O5-SnO2 electrodes were developed and found to be electrocatalytically active towards water (with 5% Ta content, 10 oxide film layers) and organic compounds oxidation (with 7.5% Ta content, 8 oxide film layers) and therefore these electrodes can be applicable in both environmental and energy fields. The synergetic effect of combined electrolysis and sonication was shown while conducting sonoelectrochemical (EO/US) degradation of methylene blue (MB) and formic acid (FA). Complete degradation of MB and FA was achieved after 45 and 120 min of EO/US process respectively in neutral media. Mineralization efficiency of FA over 95% was obtained after 2 h of degradation using high frequency ultrasound (381, 863, 1176 kHz) combined with 9.1 mA/cm2 current density. EO/US degradation of MB provided over 75% mineralization in 8 h. High degradation kinetic rates and mineralization efficiencies of model pollutants obtained in EO/US experiments provide the preconditions for further extrapolation of this treatment method to pilot scale studies with industrial wastewaters.

Contribution of plant phytochemicals to organic homeostasis: focus on the aging process and opportunistic infections

Aging process is conceived as a normal stage during human life cycle, but it is also considered a hot topic among scientists and medical community. Alarming rates of premature aging and oxidative stress-related diseases have increasingly affect human individuals. Stress, pollution and exposition to chemical substances are considered the main triggering factors for those conditions; in addition, they also suppress the immune system and, therefore, improve organic vulnerability and occurrence of opportunistic infections [I]. Apart from the associated morbidity and mortality, the increasing rates of antimicrobial resistance improve the severity of the clinical conditions [2]. Botanical preparations possess a multitude of bioactive properties, namely acting as antimicrobials, antioxidants, and homeostasis modulators. Thus, upcoming alternatives, mainly based in plant phytochemicals, are necessary to improve the wellbeing as also life expectancy of individuals. The present study aims to evaluate and to compare both antioxidant and antimicrobial properties of plant extracts rich in phenolic compounds. Among the tested plants, Glycyrrhiza glabra L. (licorice) evidenced the most pronounced free radicals scavenging and antimicrobial effects, followed by Salvia officina/is L. (sage), Thymus vulgaris L. (thyme) and Origanum vulgare L. (oregano). Eucalyptus globulus Labill. (blue gum) and Juglans regia L. (walnut) also showed a high effect, while Pterospartum tridentatum (L.) Willk. (carqueja) and Rubus ulmifolius Schott (elm leaf blackberry) displayed moderate effects, and lastly, Tabebuia impetigirwsa (Mart. ex DC) Standley (pau d'arco), Foeniculum vulgare Miller (fennel), Rosa canina L. (rose hips) and Matricaria recutita L. (chamomile) gave only slight effects. In general, the most pronounced bioactivities were observed in the plant preparations (infusion>decoction>hydromethanolic extract) with higher levels of phenolic compounds (both flavonoids and phenolic acids). The observed synergisms between the phenolic compounds present in the extracts highlight the use of phytochemicals as future health promoters. However, further studies are necessary to understand the effective mode of action of individual phenolic constituents as also the existence of polyvalence relationships between them.

Time-Dependent Density Functional Molecular Orbital and Excited State Calculations on Bis(porphyrinyl)butadiynes in the Monocationic, Neutral, Monoanionic, and Dianionic Oxidation States

We report a theoretical study of the multiple oxidation states (1+, 0, 1−, and 2−) of a meso,meso-linked diporphyrin, namely bis[10,15,20-triphenylporphyrinatozinc(II)-5-yl]butadiyne (4), using Time-Dependent Density Functional Theory (TDDFT). The origin of electronic transitions of singlet excited states is discussed in comparison to experimental spectra for the corresponding oxidation states of the close analogue bis{10,15,20-tris[3‘,5‘-di-tert-butylphenyl]porphyrinatozinc(II)-5-yl}butadiyne (3). The latter were measured in previous work under in situ spectroelectrochemical conditions. Excitation energies and orbital compositions of the excited states were obtained for these large delocalized aromatic radicals, which are unique examples of organic mixed-valence systems. The radical cations and anions of butadiyne-bridged diporphyrins such as 3 display characteristic electronic absorption bands in the near-IR region, which have been successfully predicted with use of these computational methods. The radicals are clearly of the “fully delocalized” or Class III type. The key spectral features of the neutral and dianionic states were also reproduced, although due to the large size of these molecules, quantitative agreement of energies with observations is not as good in the blue end of the visible region. The TDDFT calculations are largely in accord with a previous empirical model for the spectra, which was based simplistically on one-electron transitions among the eight key frontier orbitals of the C4 (1,4-butadiyne) linked diporphyrins.

Characterisation of indoor air organic pollutants in Brisbane

The occurrence and levels of airborne polycyclic aromatic hydrocarbons and volatile organic compounds in selected non-industrial environments in Brisbane have been investigated as part of an integrated indoor air quality assessment program. The most abundant and most frequently encountered compounds include, nonanal, decanal, texanol, phenol, 2-ethyl-1-hexanol, ethanal, naphthalene, 2,6-tert-butyl-4-methyl-phenol (BHT), salicylaldehyde, toluene, hexanal, benzaldehyde, styrene, ethyl benzene, o-, m- and pxylenes, benzene, n-butanol, 1,2-propandiol, and n-butylacetate. Many of the 64 compounds usually included in the European Collaborative Action method of TVOC analysis were below detection limits in the samples analysed. In order to extract maximum amount of information from the data collected, multivariate data projection methods have been employed. The implications of the information extracted on source identification and exposure control are discussed.

Organic and acquisitive employment growth : re-examining,testing and extending Penrose's Growth Theory.

Edith Penrose’s theory of firm growth postulates that a firm’s current growth rate will be influenced by the adjustment costs of, and changes to a firm’s productive opportunity set arising from, previous growth. Although she explicitly considered the impact of previous organic growth on current organic growth, she was largely silent about the impact of previous acquisitive growth. In this paper we extend Penrose’s work to examine that the relative impact of organic and acquisitive growth on the adjustment costs and productive opportunity set of the firm. Employing a panel of commercially active enterprises in Sweden over a 10 year period our results suggest the following. First, previous organic growth acts as a constraint on current organic growth. Second, previous acquisitive growth has a positive effect on current organic growth. We conclude that organic growth and acquisitive growth constitute two distinct strategic options facing the firm, which have a differential impact on the future organic growth of the firm.

Proton-transfer versus nontransfer in compounds of the diazo-dye precursor 4-(phenyldiazenyl) aniline (aniline yellow) with strong organic acids: the 5-sulfosalicylate and the dichroic benzenesulfonate salts, and the 1:2 adduct with 3,5-dinitrobenzoic

The structures of two 1:1 proton-transfer red-black dye compounds formed by reaction of aniline yellow [4-(phenyldiazenyl)aniline] with 5-sulfosalicylic acid and benzenesulfonic acid, and a 1:2 nontransfer adduct compound with 3,5-dinitrobenzoic acid have been determined at either 130 or 200 K. The compounds are 2-(4-aminophenyl)-1-phenylhydrazin-1-ium 3-carboxy-4-hydroxybenzenesulfonate methanol solvate, C12H12N3+.C7H5O6S-.CH3OH (I), 2-(4-aminophenyl)-1-hydrazin-1-ium 4-(phenydiazinyl)anilinium bis(benzenesulfonate), 2C12H12N3+.2C6H5O3S-, (II) and 4-(phenyldiazenyl)aniline-3,5-dinitrobenzoic acid (1/2) C12H11N3.2C~7~H~4~N~2~O~6~, (III). In compound (I) the diaxenyl rather than the aniline group of aniline yellow is protonated and this group subsequently akes part in a primary hydrogen-bonding interaction with a sulfonate O-atom acceptor, producing overall a three-dimensional framework structure. A feature of the hydrogen bonding in (I) is a peripheral edge-on cation-anion association involving aromatic C--H...O hydrogen bonds, giving a conjoint R1/2(6)R1/2(7)R2/1(4)motif. In the dichroic crystals of (II), one of the two aniline yellow species in the asymmetric unit is diazenyl-group protonated while in the other the aniline group is protonated. Both of these groups form hydrogen bonds with sulfonate O-atom acceptors and thee, together with other associations give a one-dimensional chain structure. In compound (III), rather than proton-transfer, there is a preferential formation of a classic R2/2(8) cyclic head-to-head hydrogen-bonded carboxylic acid homodimer between the two 3,5-dinitrobenzoic acid molecules, which in association with the aniline yellow molecule that is disordered across a crystallographic inversion centre, result in an overall two-dimensional ribbon structure. This work has shown the correlation between structure and observed colour in crystalline aniline yellow compounds, illustrated graphically in the dichroic benzenesulfonate compound.

Ultrafine particles in indoor air of a school : possible role of secondary organic aerosols

The aim of this work was to investigate ultrafine particles (< 0.1 μm) in primary school classrooms, in relation to the classrooms activities. The investigations were conducted in three classrooms during two measuring campaigns, which together encompassed a period of 60 days. Initial investigations showed that under the normal operating conditions of the school there were many occasions in all three classrooms where indoor particle concentrations increased significantly compared to outdoor levels. By far the highest increases in the classroom resulted from art activities (painting, gluing and drawing), at times reaching over 1.4 x 105 particle cm-3. The indoor particle concentrations exceeded outdoor concentrations by approximately one order of magnitude, with a count median diameter ranging from 20-50 nm. Significant increases also occurred during cleaning activities, when detergents were used. GC-MS analysis conducted on 4 samples randomly selected from about 30 different paints and glues, as well as the detergent used in the school, showed that d-limonene was one of the main organic compounds of the detergent, however, it was not detected in the samples of the paints and the glue. Controlled experiments showed that this monoterpene, emitted from the detergent, reacted with O3 (at outdoor ambient concentrations ranging from 0.06-0.08ppm) and formed secondary organic aerosols. Further investigations to identify other liquids which may be potential sources of the precursors of secondary organic aerosols, were outside the scope of this project, however, it is expected that the problem identified by this study could be more widely spread, since most primary schools use liquid materials for art classes, and all schools use detergents for cleaning. Further studies are therefore recommended to better understand this phenomenon and also to minimize school children exposure to ultrafine particles from these indoor sources.

The synthesis of novel isoindoline nitroxides bearing water-solubilising functionality

A range of novel tetramethyl- and tetraethylisoindolinenitroxides, possessing aryl-linked carboxylic acids, amines, alcohols and phosphonic acids were prepared. Notably, the chemistry established for the aromatic dibromination of the tetramethylisoindolines was not easily transferred to the corresponding tetraethylisoindoline system. Instead, various tetraethylisoindoline analogues were accessed by the oxidation of methyl groups attached to the aromatic ring to give the carboxylic acids. The increased steric bulk of the tetraethyl structures should limit bio-reduction and these compounds may have potential as antioxidants.