Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 22
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Chemosphere ; 246: 125705, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31891848

RESUMO

The photochemical fate of the herbicide bentazone was assessed by lab experiments and modeling tools. Experimental and modeling results showed that bentazone is mainly photodegraded by direct photolysis in natural water samples, even in the presence of dissolved organic matter (DOM) that can act as light-screening agent, photosensitizer and scavenger of reactive species. Even when it was dissolved in natural water samples containing different DOM amounts, the phototransformation kinetics of bentazone was unchanged compared to irradiation runs in ultrapure water. This finding suggests that the DOM and the other components of our samples did not affect the direct photolysis of bentazone by light-absorption competition, at least at the experimental optical path lengths, and did not induce significant indirect photodegradation by producing reactive transient species. Photochemical modeling in a lake-water photoreactivity scenario corroborated the observed experimental results, showing the predominant role of direct photolysis in the overall (direct + indirect) photodegradation of bentazone at different water depths and DOM contents. However, the model predicted a minor but non-negligible contribution of indirect photochemistry (i.e., reactions triggered by HO•, CO3•- and 3CDOM*) to the herbicide degradation. This contribution (especially by 3CDOM*) could become crucial in deep and DOM-rich water bodies. Finally, several photoproducts formed by direct photolysis and HO•-induced photodegradation were identified, which should not be particularly toxic for aquatic organisms and Vibrio fischeri bacteria.


Assuntos
Benzotiadiazinas/química , Processos Fotoquímicos , Poluentes Químicos da Água/química , Água Doce/química , Herbicidas , Cinética , Fotoquímica , Fotólise , Poluentes Químicos da Água/análise
2.
Molecules ; 25(2)2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31968643

RESUMO

This review paper describes briefly the cloud aqueous phase composition and deeply its reactivity in the dark and mainly under solar radiation. The role of the main oxidants (hydrogen peroxide, nitrate radical, and hydroxyl radical) is presented with a focus on the hydroxyl radical, which drives the oxidation capacity during the day. Its sources in the aqueous phase, mainly through photochemical mechanisms with H2O2, iron complexes, or nitrate/nitrite ions, are presented in detail. The formation rate of hydroxyl radical and its steady state concentration evaluated by different authors are listed and compared. Finally, a paragraph is also dedicated to the sinks and the reactivity of the HO• radical with the main compounds found in the cloud aqueous phase. This review presents an assessment of the reactivity in the cloud aqueous phase and shows the significant potential impact that this medium can have on the chemistry of the atmosphere and more generally on the climate.

3.
Phys Chem Chem Phys ; 21(37): 20613-20627, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31528972

RESUMO

Atmospheric aerosol particles with a high viscosity may become inhomogeneously mixed during chemical processing. Models have predicted gradients in condensed phase reactant concentration throughout particles as the result of diffusion and chemical reaction limitations, termed chemical gradients. However, these have never been directly observed for atmospherically relevant particle diameters. We investigated the reaction between ozone and aerosol particles composed of xanthan gum and FeCl2 and observed the in situ chemical reaction that oxidized Fe2+ to Fe3+ using X-ray spectromicroscopy. Iron oxidation state of particles as small as 0.2 µm in diameter were imaged over time with a spatial resolution of tens of nanometers. We found that the loss off Fe2+ accelerated with increasing ozone concentration and relative humidity, RH. Concentric 2-D column integrated profiles of the Fe2+ fraction, α, out of the total iron were derived and demonstrated that particle surfaces became oxidized while particle cores remained unreacted at RH = 0-20%. At higher RH, chemical gradients evolved over time, extended deeper from the particle surface, and Fe2+ became more homogeneously distributed. We used the kinetic multi-layer model for aerosol surface and bulk chemistry (KM-SUB) to simulate ozone reaction constrained with our observations and inferred key parameters as a function of RH including Henry's Law constant for ozone, HO3, and diffusion coefficients for ozone and iron, DO3 and DFe, respectively. We found that HO3 is higher in our xanthan gum/FeCl2 particles than for water and increases when RH decreased from about 80% to dry conditions. This coincided with a decrease in both DO3 and DFe. In order to reproduce observed chemical gradients, our model predicted that ozone could not be present further than a few nanometers from a particle surface indicating near surface reactions were driving changes in iron oxidation state. However, the observed chemical gradients in α observed over hundreds of nanometers must have been the result of iron transport from the particle interior to the surface where ozone oxidation occurred. In the context of our results, we examine the applicability of the reacto-diffusive framework and discuss diffusion limitations for other reactive gas-aerosol systems of atmospheric importance.

4.
Chem Commun (Camb) ; 55(42): 5946-5949, 2019 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-31049542

RESUMO

Fragmentation of molecular clusters inside mass spectrometers is a significant source of uncertainty in a wide range of chemical applications. We have measured the fragmentation of sulfuric acid clusters driving atmospheric new-particle formation, and developed a novel model, based on first principles calculations, capable of quantitatively predicting the extent of fragmentation.

5.
J Phys Chem A ; 123(2): 611-624, 2019 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-30550283

RESUMO

Atmospheric clusters are weakly bound and can fragment inside the measuring instruments, in particular, mass spectrometers. Since the clusters accelerate under electric fields, the fragmentation cannot be described in terms of rate constants under equilibrium conditions. Using basic statistical principles, we have developed a model for fragmentation of clusters moving under an external force. The model describes an energy transfer to the cluster internal modes caused by collisions with residual carrier gas molecules. As soon as enough energy is accumulated in the cluster internal modes, it can fragment. The model can be used for interpreting experimental measurements by atmospheric pressure interface mass spectrometers.

6.
Ecotoxicol Environ Saf ; 170: 664-672, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30579167

RESUMO

Loratadine and desloratadine are second-generation antihistaminic drugs. Because of human administration, they are continuously released via excreta into wastewater treatment plants and occur in surface waters as residues and transformation products (TPs). Loratadine and desloratadine residues have been found at very low concentrations (ng/L) in the aquatic environment but their toxic effects are still not well known. Both drugs are light-sensitive even under environmentally simulated conditions and some of the photoproducts have been isolated and characterized. The aim of the present study was to investigate the acute and chronic ecotoxicity of loratadine, desloratadine and their light-induced transformation products in organisms of the aquatic trophic chain. Bioassays were performed in the alga Pseudokirchneriella subcapitata, the rotifer Brachionus calyciflorus and in two crustaceans, Thamnocephalus platyurus and Ceriodaphnia dubia. Loratadine exerted its acute and chronic toxicity especially on Ceriodaphnia dubia (LC50: 600 µg/L, EC50: 28.14 µg/L) while desloratadine showed similar acute toxicity among the organisms tested and it was the most chronically effective compound in Ceriodaphnia dubia and Pseudokirchneriella subcapitata. Generally, transformation products were less active in both acute and chronic assays.


Assuntos
Organismos Aquáticos/efeitos dos fármacos , Crustáceos/efeitos dos fármacos , Loratadina/análogos & derivados , Rotíferos/efeitos dos fármacos , Raios Ultravioleta , Poluentes Químicos da Água/toxicidade , Animais , Relação Dose-Resposta a Droga , Loratadina/química , Loratadina/efeitos da radiação , Loratadina/toxicidade , Estrutura Molecular , Testes de Toxicidade Aguda , Testes de Toxicidade Crônica , Águas Residuárias/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/efeitos da radiação
7.
Proc Natl Acad Sci U S A ; 115(37): 9122-9127, 2018 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-30154167

RESUMO

Nucleation and growth of aerosol particles from atmospheric vapors constitutes a major source of global cloud condensation nuclei (CCN). The fraction of newly formed particles that reaches CCN sizes is highly sensitive to particle growth rates, especially for particle sizes <10 nm, where coagulation losses to larger aerosol particles are greatest. Recent results show that some oxidation products from biogenic volatile organic compounds are major contributors to particle formation and initial growth. However, whether oxidized organics contribute to particle growth over the broad span of tropospheric temperatures remains an open question, and quantitative mass balance for organic growth has yet to be demonstrated at any temperature. Here, in experiments performed under atmospheric conditions in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at the European Organization for Nuclear Research (CERN), we show that rapid growth of organic particles occurs over the range from [Formula: see text]C to [Formula: see text]C. The lower extent of autoxidation at reduced temperatures is compensated by the decreased volatility of all oxidized molecules. This is confirmed by particle-phase composition measurements, showing enhanced uptake of relatively less oxygenated products at cold temperatures. We can reproduce the measured growth rates using an aerosol growth model based entirely on the experimentally measured gas-phase spectra of oxidized organic molecules obtained from two complementary mass spectrometers. We show that the growth rates are sensitive to particle curvature, explaining widespread atmospheric observations that particle growth rates increase in the single-digit-nanometer size range. Our results demonstrate that organic vapors can contribute to particle growth over a wide range of tropospheric temperatures from molecular cluster sizes onward.

8.
J Phys Chem A ; 122(20): 4717-4729, 2018 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-29693391

RESUMO

The role of a strong organobase, guanidine, in sulfuric acid-driven new-particle formation is studied using state-of-the-art quantum chemical methods and molecular cluster formation simulations. Cluster formation mechanisms at the molecular level are resolved, and theoretical results on cluster stability are confirmed with mass spectrometer measurements. New-particle formation from guanidine and sulfuric acid molecules occurs without thermodynamic barriers under studied conditions, and clusters are growing close to a 1:1 composition of acid and base. Evaporation rates of the most stable clusters are extremely low, which can be explained by the proton transfers and symmetrical cluster structures. We compare the ability of guanidine and dimethylamine to enhance sulfuric acid-driven particle formation and show that more than 2000-fold concentration of dimethylamine is needed to yield as efficient particle formation as in the case of guanidine. At similar conditions, guanidine yields 8 orders of magnitude higher particle formation rates compared to dimethylamine. Highly basic compounds such as guanidine may explain experimentally observed particle formation events at low precursor vapor concentrations, whereas less basic and more abundant bases such as ammonia and amines are likely to explain measurements at high concentrations.

9.
Sci Rep ; 7(1): 12693, 2017 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-28978998

RESUMO

Organic interfaces that exist at the sea surface microlayer or as surfactant coatings on cloud droplets are highly concentrated and chemically distinct from the underlying bulk or overlying gas phase. Therefore, they may be potentially unique locations for chemical or photochemical reactions. Recently, photochemical production of volatile organic compounds (VOCs) was reported at a nonanoic acid interface however, subsequent secondary organic aerosol (SOA) particle production was incapable of being observed. We investigated SOA particle formation due to photochemical reactions occurring at an air-water interface in presence of model saturated long chain fatty acid and alcohol surfactants, nonanoic acid and nonanol, respectively. Ozonolysis of the gas phase photochemical products in the dark or under continued UV irradiation both resulted in nucleation and growth of SOA particles. Irradiation of nonanol did not yield detectable VOC or SOA production. Organic carbon functionalities of the SOA were probed using X-ray microspectroscopy and compared with other laboratory generated and field collected particles. Carbon-carbon double bonds were identified in the condensed phase which survived ozonolysis during new particle formation and growth. The implications of photochemical processes occurring at organic coated surfaces are discussed in the context of marine SOA particle atmospheric fluxes.

10.
J Phys Chem A ; 121(32): 6155-6164, 2017 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-28732163

RESUMO

Recent experimental evidence suggests that diamines can enhance atmospheric new particle formation more efficiently compared to monoamines such as dimethylamine. Here we investigate the molecular interactions between sulfuric acid (sa) and the diamine putrescine (put) using computational methods. The molecular structure of up to four sulfuric acid molecules and up to four putrescine molecules were obtained at the ωB97X-D/6-31++G(d,p) level of theory. We utilized a domain local pair natural orbital coupled cluster method (DLPNO-CCSD(T)/aug-cc-pVTZ) to obtain highly accurate binding energies of the clusters. We find that the (sa)1-4(put)1-4 clusters show more ionic character than clusters consisting of sulfuric acid and dimethylamine (dma) by readily forming several sulfate ions in the cluster. To estimate the stability of the clusters, we calculate the evaporation rates and compare them to ESI-APi-TOF measurements. Using the atmospheric cluster dynamics code (ACDC), we simulate and compare the new particle formation rates between the (sa)1-4(put)1-4 and (sa)1-4(dma)1-4 cluster systems. We find that putrescine significantly enhances the formation of new particles compared to dimethylamine. Our findings suggest that a large range of amines with different basicity is capable of explaining various regions of the observed new particle formation events. These results indicate that diamines, or related compounds with high basicity, might be important species in forming the initial cluster with sulfuric acid and subsequently more abundant amines with lower basicity can assist in the new particle formation process by attaching to the sulfuric acid-diamine nucleus.

11.
Environ Sci Technol ; 50(20): 11041-11048, 2016 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-27611489

RESUMO

Interfaces are ubiquitous in the environment and many atmospheric key processes, such as gas deposition, aerosol, and cloud formation are, at one stage or another, strongly impacted by physical and chemical processes occurring at interfaces. Here, the photoinduced chemistry of an air/water interface coated with nonanoic acid-a fatty acid surfactant we use as a proxy for chemically complex natural aqueous surface microlayers-was investigated as a source of volatile and semivolatile reactive organic species. The carboxylic acid coating significantly increased the propensity of photosensitizers, chosen to mimic those observed in real environmental waters, to partition to the interface and enhance reactivity there. Photochemical formation of functionalized and unsaturated compounds was systematically observed upon irradiation of these coated surfaces. The role of a coated interface appears to be critical in providing a concentrated medium allowing radical-radical reactions to occur in parallel with molecular oxygen additions. Mechanistic insights are provided from extensive analysis of products observed in both gas and aqueous phases by online switchable reagent ion-time of flight-mass spectrometry and by off-line ultraperformance liquid chromatography coupled to a Q Exactive high resolution mass spectrometer through heated electrospray ionization, respectively.


Assuntos
Processos Fotoquímicos , Água/química , Aerossóis , Fenômenos Químicos , Ácidos Graxos
12.
Science ; 353(6300): 699-702, 2016 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-27516601

RESUMO

Although fatty acids are believed to be photochemically inert in the actinic region, complex volatile organic compounds are produced during illumination of an air-water interface coated solely with a monolayer of carboxylic acid. When aqueous solutions containing nonanoic acid (NA) at bulk concentrations that give rise to just over a monolayer of NA coverage are illuminated with actinic radiation, saturated and unsaturated aldehydes are seen in the gas phase, and more highly oxygenated products appear in the aqueous phase. This chemistry is probably initiated by triplet-state NA molecules excited by direct absorption of actinic light at the water surface. Because fatty acids-covered interfaces are ubiquitous in the environment, such photochemical processing will have a substantial impact on local ozone and particle formation.

13.
Environ Sci Technol ; 50(17): 9324-32, 2016 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-27487120

RESUMO

In the present work, the photoreactivity of a mixture of iron(III)­pyoverdin (Fe(III)­Pyo) complexes was investigated under simulated cloud conditions. Pyoverdins are expected to complex ferric ions naturally present in cloudwater, thus modifying their availability and photoreactivity. The spectroscopic properties and photoreactivity of Fe(III)-Pyo were investigated, with particular attention to their fate under solar irradiation, also studied through simulations. The photolysis of the Fe(III)­Pyo complex leads to the generation of Fe(II), with rates of formation (RFe(II)f) of 6.98 and 3.96 × 10­9 M s­1 at pH 4.0 and 6.0, respectively. Interestingly, acetate formation was observed during the iron-complex photolysis, suggesting that fragmentation can occur after the ligand-to-metal charge transfer (LMCT) via a complex reaction mechanism. Moreover, photogenerated Fe(II) represent an important source of hydroxyl radical via the Fenton reaction in cloudwater. This reactivity might be relevant for the estimation of the rates of formation and steady-state concentrations of the hydroxyl radical by cloud chemistry models and for organic matter speciation in the cloud aqueous phase. In fact, the conventional models, which describe the iron photoreactivity in terms of iron­aqua and oxalate complexes, are not in accordance with our results.


Assuntos
Ferro , Fotólise , Sideróforos , Compostos Férricos , Radical Hidroxila , Oxalatos
14.
Angew Chem Int Ed Engl ; 55(35): 10336-9, 2016 08 22.
Artigo em Inglês | MEDLINE | ID: mdl-27458109

RESUMO

The heterogeneous reaction between SO2 and unsaturated compounds results in the efficient production of organosulfates for several fatty acids and long-chain alkenes. The presence of an acid group, the physical state of the reactants (solid or liquid), the nature of the double bond (cis, trans, terminal), and the use of light irradiation all have an impact on the reaction rate. The reaction was investigated using different set-ups (coated flow tube, aerosol flow tube, and diffuse reflectance infrared Fourier transform cell). The reaction products were identified by high-resolution mass spectrometry and the impact of this reaction on organosulfate formation in the atmosphere is discussed.

15.
J Am Chem Soc ; 137(26): 8348-51, 2015 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-26068588

RESUMO

We report on experiments that probe photosensitized chemistry at the air/water interface, a region that does not just connect the two phases but displays its own specific chemistry. Here, we follow reactions of octanol, a proxy for environmentally relevant soluble surfactants, initiated by an attack by triplet-state carbonyl compounds, which are themselves concentrated at the interface by the presence of this surfactant. Gas-phase products are determined using PTR-ToF-MS, and those remaining in the organic layer are determined by ATR-FTIR spectroscopy and HPLC-HRMS. We observe the photosensitized production of carboxylic acids as well as unsaturated and branched-chain oxygenated products, compounds that act as organic aerosol precursors and had been thought to be produced solely by biological activity. A mechanism that is consistent with the observations is detailed here, and the energetics of several key reactions are calculated using quantum chemical methods. The results suggest that the concentrating nature of the interface leads to its being a favorable venue for radical reactions yielding complex and functionalized products that themselves could initiate further secondary chemistry and new particle formation in the atmospheric environment.

16.
Sci Total Environ ; 518-519: 258-65, 2015 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-25765378

RESUMO

The photochemical behavior of etodolac was investigated under various irradiation conditions. Kinetic data were obtained after irradiation of 10(-4) M aqueous solutions by UVB, UVA and direct exposure to sunlight. The Xenon lamp irradiation was used in order to determine the photodegradation quantum yield under sun-simulated condition (ϕsun). The value was determined to be=0.10±0.01. In order to obtain photoproducts and for mechanistic purposes, experiments were carried out on more concentrated solutions by exposure to sunlight and to UVA and UVB lamps. The drug underwent photooxidative processes following an initial oxygen addition to the double bond of the five membered ring and was mainly converted into a spiro compound and a macrolactam. Ecotoxicity tests were performed on etodolac, its photostable spiro derivative and its sunlight irradiation mixture on two different aquatic trophic levels, plants (algae) and invertebrates (rotifers and crustaceans). Mutagenesis and genotoxicity were detected on bacterial strains. The results showed that only etodolac had long term effects on rotifers although at concentrations far from environmental detection values. A mutagenic and genotoxic potential was found for its derivative.


Assuntos
Etodolac/química , Fotólise , Poluentes Químicos da Água/química , Animais , Crustáceos , Etodolac/toxicidade , Rotíferos , Luz Solar , Poluentes Químicos da Água/toxicidade
17.
Environ Sci Pollut Res Int ; 21(21): 12154-62, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24801287

RESUMO

The present work compares the efficiency of homogenous Fenton and photo-Fenton processes in the presence of Fe(III)-EDDS complex under different experimental conditions. 4-tert-Butylphenol (4-t-BP), which is one of the endocrine disrupting chemicals, was used as a model pollutant to investigate the Fenton and photo-Fenton application. The efficiency of homogenous photo-Fenton process was significantly much higher than homogenous Fenton process, which is due to the rapid formation of Fe(2+) under UV irradiation of the iron complex and the photochemical formation of HO(•) from the photolysis of the complex Fe(III)-EDDS. Through the degradation of 4-t-BP, the effect of Fe(III)-EDDS concentration, H2O2 concentration, pH, and oxygen was investigated in both processes. Such trend was also correlated with pH calculating the polychromatic Fe(2+) quantum yield formation at pH 4.0, 6.0, and 8.6. The results showed that at high Fe(III)-EDDS and H2O2 concentrations, a negative effect was found. By the way, the Fenton process was found to be enhanced at basic pH. These results can be very useful for the use and optimization of such iron complex in water treatment process as function of different physico-chemical conditions.


Assuntos
Compostos Férricos/química , Fenóis/química , Processos Fotoquímicos , Fotólise , Purificação da Água/métodos , Disruptores Endócrinos/química , Peróxido de Hidrogênio/química , Oxigênio/química , Raios Ultravioleta
18.
Water Res ; 55: 106-14, 2014 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-24602865

RESUMO

This work investigated the fate of nicotine (Nico) in aqueous solution upon reaction with singlet oxygen ((1)O2) and hydroxyl radical (HO·). The second-order rate constants of Nico with (1)O2 (k(Nico,(1)O(2)) = (3.38 ± 0.14) × 10(6) M(-1) s(-1)) and HO· (kNico,·OH = (1.08 ± 0.10) × 10(9) M(-1) s(-1)) were determined using competition kinetics. Photochemical modelling showed that the reaction of Nico with HO· would prevail over that with (1)O2 in surface waters transformation pathway. The Nico photochemical half-life time could be accounted for by the two reactions. This value would vary in the month-year range depending on the environmental conditions: phototransformation would be favoured in shallow water poor in organic matter and rich in nitrate and nitrite. Irradiation experiments of Nico with nitrite suggested that transformation could not be accounted for by HO· reaction alone. Indeed, a variable fraction of Nico transformation (30-80% depending on the conditions) would take place upon reaction with additional transients, photogenerated NOx being possible candidates. The chemical structures of the transformation intermediates were derived by means of HPLC-MS. The detection of nitroderivatives upon irradiation of Nico with nitrite suggests the involvement of nitrogen dioxide in the relevant photoprocesses.


Assuntos
Radical Hidroxila/química , Nicotina/química , Fotoquímica , Cromatografia Líquida de Alta Pressão
19.
Environ Sci Process Impacts ; 16(4): 823-31, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24166079

RESUMO

In this study, a comparison of two carbamic pesticides, chlorpropham and phenisopham, was carried out in terms of both photodegradability and ecotoxicity. The photochemical behaviour of the two pesticides was investigated under environmental-like conditions (aqueous media, UVB or solar irradiation). The photochemical kinetic parameters were calculated by irradiating 5 × 10(-5) M solutions (H2O-CH3CN, 9 : 1 v/v) using UVB lamps. For chlorpropham and phenisopham similar half-life times (39.0 and 55.0 min) were determined. Irradiation by sunlight leads to longer degradation half-life times (about 3 months), while it is possible to observe the formation of the same photoproducts. The well-known dechlorination reaction to a hydroxyphenylcarbamate was observed for chlorpropham. Phenisopham undergoes photo-Fries reaction to give rearranged products (hydroxybenzamides) and fragmentation products (hydroxyphenylcarbamate and N-ethylaniline). Acute and chronic toxicity tests of pesticides and their photoproducts were performed on organisms from two levels of the freshwater aquatic chain, the anostraca crustacean Thamnocephalus platyurus, the rotifer Brachionus calyciflorus and the alga Pseudokirchneriella subcapitata. The acute results showed that chlorpropham had median lethal concentrations for the crustacean T. platyurus and the rotifer B. calyciflorus of 10.16 and 35.19 mg L(-1), respectively, and phenisopham did not show any acute toxicity as the derivatives up to 10 mg L(-1). The only exception was N-ethylaniline which exhibited an acute LC50 value of 0.46 mg L(-1). Phenisopham was the most toxic in the long term exposure while its five derivatives showed lower chronic potential for rotifers and algae. The same trend was observed for chlorpropham except for rotifers.


Assuntos
Carbamatos/toxicidade , Clorprofam/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Carbamatos/química , Carbamatos/efeitos da radiação , Clorprofam/química , Clorprofam/efeitos da radiação , Ecotoxicologia , Fotólise , Medição de Risco , Testes de Toxicidade , Poluentes Químicos da Água/efeitos da radiação
20.
Water Res ; 47(14): 5422-30, 2013 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-23863380

RESUMO

In this paper we investigated the degradation of the rivastigmine drug induced by hydroxyl radical in synthetic and natural waters focusing on both reactivity and photoproducts identification. The hydroxyl radical formation rate was quantified by using terephthalic acid as trapping molecule and it was related with the rivastigmine degradation rate. The second order rate constant between hydroxyl radical and rivastigmine was estimated to be ≈ 5.8 × 10(9) M(-1) s(-1). Irradiation of rivastigmine in three natural waters (rain, lake and river) and comparison with degradation rates observed in synthetic solutions using nitrite, nitrate and hydrogen peroxide suggest that, in addition to hydroxyl radical, also nitroderived radicals (NO/NO2) are responsible for the pollutant degradation in natural media. In fact, the evaluated degradation rates in three natural waters are greatly higher than those estimated considering only the reactivity with photogenerated hydroxyl radical. Using nitrites and nitrates as photochemical OH source, the rivastigmine degradation cannot be described considering only the hydroxyl radical reactivity suggesting that NO and NO2 radicals could play a key role during indirect degradation. Moreover main degradation products have been identified by means of HPLC-MS. Hydroxylation of the aromatic ring as well as carbamate and amino chain oxidation were suggested as main reaction mechanisms, but also nitroderived compounds were characterized. Finally polychromatic irradiations of three rivastigmine doped natural waters (rain, river and lake) underlined the role of the indirect degradation that needs to be considered when direct degradation of selected pollutants is negligible under environmental-like conditions.


Assuntos
Radical Hidroxila/química , Fenilcarbamatos/química , Poluentes Químicos da Água/química , Biodegradação Ambiental , Hidroxilação , Lagos/química , Nitratos/química , Nitritos/química , Fotólise , Ácidos Ftálicos , Chuva/química , Rivastigmina , Rios/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA