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1.
Artigo em Inglês | MEDLINE | ID: mdl-38833048

RESUMO

Occurrence of 20 organochlorine pesticides (OCPs) in 60 organic and non-organic fruits and vegetables matrices was undertaken using QuEChERS Method EN 15662 for sample preparation analyzed by gas chromatography-mass spectrometry (GC-MS/MS). The procedural method was validated by spiking the OCP standard solutions at three fortified levels at 10, 50, and 100 µg/kg wet weight (ww) to the real matrix of fruit and vegetable with good recovery ranging from 75 to 108% with relative standard deviation (RSD) ≤ 11%, and the limits of detection and quantification (LODs and LOQs) were 0.002-0.02 µg/kg and 0.004-0.1 µg/kg ww, respectively. The assessment of health risks associated with pesticide residues through consumption of vegetables and fruits and the effect of washing and peeling on concentration of various pesticides were also studied. The results showed that the concentration levels of 60% of samples were lower than the LOQs, while the rest was contaminated by OCP residues. Organic fruits and vegetables showed the absence of OCPs, while several of the studied compounds were detected from conventional agriculture. Skin removal (peeling) was the most effective strategy to eliminate or decrease pesticide residues, and should be one of the solutions to reduce the health impact of pesticides in fruits and vegetables. The analysis of health risk assessment was based on the use of the estimated average daily intake (EDI), hazard index (HI), and hazard ratio (HR) for individuals in two weight categories: children (weighing 16.7 kg) and adults (weighing 60 kg). The HI values were less than 1 suggesting that there was no probable non-carcinogenic health effect, except for heptachlor for children (HI of 1.285). However, the values of HR revealed that children were more susceptible to the carcinogenic health effect associated with consuming contaminated vegetables.

2.
Chemosphere ; 339: 139686, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37544523

RESUMO

Bisphenols (BPs) and phthalate esters (PAEs) are important compounds for the plastics industry, also called "everywhere chemicals" due to their ubiquity in daily use products. Both chemical groups are well-known environmental contaminants, whose presence has been reported in all environmental compartments, and whose effects, mainly associated to endocrine disruption, are detrimental to living organisms. Cetaceans, due to their long life-span, low reproduction rate and high position in the trophic web, are especially vulnerable to the effects of contaminants. However, little is known about BP and PAE concentrations in cetacean tissues, their potential relation to individual biological variables, or their trends over time. Here, the concentration of 10 BPs and 13 PAEs was assessed in the muscle of 30 striped dolphins (Stenella coeruleoalba) stranded along the Spanish Catalan coast (NW Mediterranean) between 1990 and 2018. Six BP and 6 PAE compounds were detected, of which only 4,4'-(cyclohexane-1,1-diyl)diphenol (BPZ) was detected in all the samples, at the highest concentration (mean 16.06 µg g-1 lipid weight). Sex or reproductive condition were largely uninfluential on concentrations: only dimethylphthalate (DMP) concentrations were significantly higher in immature individuals than in adults, and the overall PAE concentrations were significantly higher in males than in females. Temporal variations were only detected in bis(4-hydroxyphenyl)ethane (BPE), diethylphthalate (DEP) and dimethylphthalate (DMP), whose concentrations were lower, and 9,9-Bis(4-hydroxyphenyl)fluorene (BPFL), which were higher, respectively, in samples taken between 2014 and 2018, probably reflecting shifts in the production and use of these chemicals. These results provide the first assessment of concentrations of several BP and PAE compounds in the muscle of an odontocete cetacean.


Assuntos
Stenella , Animais , Feminino , Masculino , Músculos , Ésteres
3.
Environ Monit Assess ; 194(12): 856, 2022 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-36207614

RESUMO

Pollution generated from landfill solid wastes constitute one of the major threat to the environment. The landfill leachate contains various toxic pollutants, making it the most dangerous issue of the landfills. Monitoring the xenobiotic organic concentrations in landfill leachate is an important step to evaluate the environmental impacts. This work aims to characterize the seasonal variation of 55 xenobiotic organic compounds including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), phthalic acid esters (PAEs) and bisphenols (BPs) in the leachate from municipal solid waste landfill of Tripoli, Lebanon. And also, the quantity of the pollutant's flux to the Abou Ali River and the Mediterranean Sea nearby has been estimated. The organic pollutants were extracted by using the solid-phase extraction and quantified by using GC-MS/MS. The results showed high level of PAEs, BPs, PCBs, and PAHs in the leachate samples. The fluxes of pollutants to the Abou Ali River and Mediterranean Sea have been detected at 0.23 kg, 0.01 kg, 116.85 kg, 15.93 kg, and 7.58 kg for Σ16PAHs, Σ28PCBs, Σ6PAEs, Σ4BPs, and 4-NP respectively.


Assuntos
Poluentes Ambientais , Bifenilos Policlorados , Hidrocarbonetos Policíclicos Aromáticos , Eliminação de Resíduos , Poluentes Químicos da Água , Monitoramento Ambiental/métodos , Líbano , Mar Mediterrâneo , Compostos Orgânicos/análise , Ácidos Ftálicos , Bifenilos Policlorados/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Rios , Resíduos Sólidos/análise , Espectrometria de Massas em Tandem , Instalações de Eliminação de Resíduos , Poluentes Químicos da Água/análise , Xenobióticos
4.
Chemosphere ; 300: 134453, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35390406

RESUMO

The fin whale (Balaenoptera physalus) is a migratory filter-feeding species that is susceptible to ingest plastics while lunge feeding across the oceans. Plastic additives, such as phthalates, are compounds that are added to plastics to give them specific characteristics, such as flexibility. These so-called plasticizers are currently raising major concern because of their potential adverse effects on marine fauna. However, little is known about phthalate concentrations in tissues of baleen whales as well as their potential relation with biological variables (i.e., sex, body length and age) and their trends with time. In this study, we assessed the concentration of 13 phthalates in the muscle of 31 fin whales sampled in the feeding grounds off western Iceland between 1986 and 2015. We detected 5 of the 13 phthalates investigated, with di-n-butylphthalate (DBP), diethylphthalate (DEP) and bis(2-ethylhexyl) phthalate (DEHP) being the most abundant. None of the biological variables examined showed a statistically significant relationship with phthalate concentrations. Also, phthalate concentrations did not significantly vary over the 29-year period studied, a surprising result given the global scenario of increasing plastic pollution in the seas. The lack of time trends in phthalate concentration may be due in part to the fact that phthalates also originate from other sources. Although no adverse effects of phthalates on fin whales have been detected to date, further monitoring of these pollutants is required to identify potential toxic effects in the future.


Assuntos
Baleia Comum , Animais , Islândia , Ácidos Ftálicos , Plásticos
5.
Environ Sci Pollut Res Int ; 28(8): 10140-10154, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33169280

RESUMO

This work focused on the characterization of activated carbon (AC) prepared by pyrolysis-chemical activation with phosphoric acid (60%) from date stones derived from three categories of date palm Phoenix dactylifera (Ajwa, Anbari, Khudri), and on its feasibility of elimination of organochlorine pesticides (OCPs) in water samples. The obtained results showed that the three-produced AC date stone had developed a porous structure, large specific surface area, and acidic property. Due to the high SBET (> 1200 m2/g), Ajwa stones activated coal was considered as the best AC that can be used for the adsorption of environmental contaminants. The effects of several parameters such as the Ajwa AC dose, the time of contact, the initial concentration of pesticides, and the pH were evaluated. The results showed that the adsorption balance of organochlorine pesticides on this AC was reached after a contact time of 60 min at an optimal pHzpc equal to 2. In addition, 0.4 g of AC was the best quantity found to retain the largest quantity of pesticides while considering the economic part.


Assuntos
Praguicidas , Phoeniceae , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Praguicidas/análise , Água , Poluentes Químicos da Água/análise
6.
Mar Pollut Bull ; 153: 110947, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32056855

RESUMO

The levels of some persistent organic pollutants (POPs) along the Lebanese coastal zone (LCZ) were assessed by collecting15 surface sediments from five hotspot stations. Such stations were influenced by various industrial units, riverine input, and touristic activities. The levels of polycyclic aromatic hydrocarbons (∑16PAHs), their methylated derivatives (∑18Me-PAHs), and polychlorinated biphenyls (∑28PCBs) were in the range of 537-3773 µg∙kg-1 dw, 187-1541 µg∙kg-1 dw, and 143-303 µg∙kg-1 dw respectively. Significant contamination was found at Beirut Port that is surrounded by a densely populated area and is subjected to multidisciplinary activities. Source identification of PAHs was confirmed by using the diagnostic ratio of PAHs with low molecular weight and high molecular weight (LMW/HMW). For PCBs, LCZ is polluted by higher chlorinated congeners with 4 to 9 chlorinated atoms generated from volatilization and combustion processes. Toxicity and biological risks were assessed using toxic equivalent quantity (TEQcarc) and sediment quality guideline quotient (SQGq).


Assuntos
Monitoramento Ambiental , Bifenilos Policlorados , Hidrocarbonetos Policíclicos Aromáticos , Poluentes Químicos da Água , Poluentes Ambientais , Sedimentos Geológicos/química
7.
Mar Pollut Bull ; 133: 881-890, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30041391

RESUMO

A Characterization and assessment study was conducted for trace metals pollution in surface sediments at six sites including harbors, bays and river input along Lebanese coast (LCZ). A particular attention was given to Tripoli Port in order to identify the main sources of trace metals pollution inside this harbor. Total metals concentrations were compared with those reported for the shale. The results revealed that trace metals (Cd, Pb, Zn, and Cr) contamination was significantly localized at Beirut Port, which is classified as the most highly polluted site. At Tripoli Port site, metals contamination was classified as moderate; it is affected by shipping, ship maintenance activities and sewage outfall. According to the SQGs guideline, the biological adverse effect of Cd, Pb and Zn were expected to occur frequently at Beirut Port. The results obtained would be helpful in developing more effective harbor management strategies to control and monitor the metal discharges.


Assuntos
Sedimentos Geológicos/análise , Metais/análise , Baías/análise , Monitoramento Ambiental/métodos , Líbano , Rios/química , Navios , Poluentes Químicos da Água/análise
8.
Sci Total Environ ; 613-614: 1527-1542, 2018 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-28886915

RESUMO

Human activities on the shoreline generate a growing pollution, creating deleterious habitats in coastal zones. Some species nevertheless succeed in such harsh milieus, raising the question of their tolerance to environmental stress. The annelid Hediste diversicolor lives buried in the sediments, directly exposed to contaminants trapped in the mud. After verifying the similarity of their genetic contexts, we compared reproductive output and individual immune resistance measures of populations living in polluted vs. 'clean' sediments, and related these assessments with measures of phthalates and metal pollution, and associated toxicity indices. Chemical analyses predicted no toxicity to the local infauna, and phenological studies evidenced no direct cost of living in noxious habitats. However, populations exposed to pollutants showed a significantly reduced survival upon infection with a local pathogen. Surprisingly, physiological studies evidenced a basal overinflammatory state in the most exposed populations. This over-activated baseline immune phenotype likely generates self-damage leading to enhanced immune cell death rate and immune failure. Monitoring the immune status of individual worms living in anthropic areas could thus be used as a reliable source of information regarding the actual health of wild populations.


Assuntos
Biomarcadores Ambientais , Sedimentos Geológicos/química , Poliquetos/efeitos dos fármacos , Poliquetos/imunologia , Poluentes Químicos da Água/toxicidade , Animais , Monitoramento Ambiental , Poluição Ambiental , França
9.
Sci Total Environ ; 621: 578-587, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29195205

RESUMO

Phthalic Acid Esters (PAEs) are a group of emerging organic contaminants that have become a serious issue because of their ubiquitous presence and hazardous impact on the marine environment worldwide. Seawater samples were collected monthly from December 2013 to November 2014 in the northwestern Mediterranean Sea (Marseille Bay). The samples were analyzed for dissolved organic carbon (DOC) as well as the molecular distribution of dissolved PAEs by using solid phase extraction followed by gas chromatography and mass spectrometry (GC/MS) analyses. The results demonstrated the occurrence of six PAEs, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-isobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), benzylbutyl phthalate (BzBP) and diethylhexyl phthalate (DEHP), with total concentrations ranging from 130 to 1330ngL-1 (av. 522ngL-1). In Marseille Bay, the highest concentrations were detected in the bottom water from June to November 2014 and in the whole water column during the winter mixing period. This result suggests that resuspension of PAE-rich sediment, in relation to the accumulation of plastic debris above the seabed, or the higher degradation rate in the upper layer of the water column, plays a significant role in the PAE dynamics in coastal water. DEHP was the most abundant PAE in all of the surface samples and the summer bottom samples, followed by DiBP and DnBP, which also represent the largest fractions in the other bottom samples.

10.
Bull Environ Contam Toxicol ; 98(3): 392-399, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27864583

RESUMO

This study is focused on the removal, accumulation and degradation of three environmental ubiquitous polycyclic aromatic hydrocarbons (PAHs), phenanthrene (PHE), fluoranthene (FLA) and pyrene (PYR), by the marine alga Rhodomonas baltica enriched from the English Channel. After separation, purification and culture in several phases, R. baltica was exposed to PAH concentrations that are frequently encountered in the field in several anthropized environments. The results showed that R. baltica can grow under PAH stress, efficiently remove up to 70% of these compounds from the medium by 216 h of culture and selectively bioaccumulate PAHs by their hydrophobicity. Between PHE, FLA and PYR, phenanthrene was the compound with higher degradation rates throughout incubation. The equilibrium partitioning theoretical approach showed that physico-chemical partitioning, rather than active bioconcentration, was the major factor governing the bioaccumulation, outlying a potential application in decontamination processes for this species.


Assuntos
Biodegradação Ambiental , Fluorenos/análise , Phaeophyceae/metabolismo , Fenantrenos/análise , Pirenos/análise
11.
Sci Total Environ ; 563-564: 424-33, 2016 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-27151499

RESUMO

Due to their widespread use in human and animal healthcare, antibiotics and other drug residues are ubiquitous in the aquatic environment. Given their potential impacts on ecosystem functioning and public health, the quantification of environmental drug residues has become a necessity. Various analysis techniques have been found to be suitable for reliable detection of such compounds. However, quantification can be difficult because these compounds are present at trace or ultra-trace levels. Consequently, the accuracy of environmental analyses depends on both the efficiency and the robustness of the extraction and quantification method. In this work, an off-line solid-phase extraction (SPE) combined with on-line SPE-LC-MS/MS was applied to the simultaneous extraction and quantification of 26 pharmaceutical products, including 18 antibiotics, dissolved in a water phase. Optimal conditions were determined and then applied to assess the contamination level of the targeted drug residues in water collected from four sites in Northern France: a river, the input and output of an aerated lagoon, and a wastewater treatment plant. Drug residues associated with suspended solid matter (SSM) were also quantified in this work using pressurized liquid extraction (PLE) combined with an on-line SPE-LC-MS/MS system in order to complete an assessment of the degree of total background pollution.


Assuntos
Antibacterianos/análise , Resíduos de Drogas/análise , Monitoramento Ambiental/métodos , Água Doce/análise , Poluentes Químicos da Água/análise , Cromatografia Líquida/métodos , França , Rios , Extração em Fase Sólida/métodos , Espectrometria de Massas em Tandem/métodos , Águas Residuárias/análise
12.
Environ Pollut ; 206: 38-48, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26142749

RESUMO

The occurrence of three groups of hazardous organic contaminants (PCBs, PAHs, Me-PAHs) in fifteen watercourses and rivers located in highly urbanized and industrialized zones was studied. The distribution of 62 organic contaminants was determined in three matrices: in the dissolved phase, associated with suspended solid matter (SSM) and in sediment. Their distributions in the aquatic environment depend strongly on their physicochemical properties. Low molecular weight PAHs were predominant in the dissolved phase while those with high molecular weight accumulated preferentially in SSM and sediments. Among the 28 PCBs congeners, only PCB153 was detected. The results showed that the contamination of these areas originated mainly from combustion processes. The three the most polluted sites identified are surrounded by big cities. Ecotoxicological assessment based on the international Sediment Quality Guidelines (SQGs) showed that the toxic effects of the sediment in these watercourses and rivers occurred due to high levels of hydrocarbons.


Assuntos
Monitoramento Ambiental , Sedimentos Geológicos/química , Bifenilos Policlorados/química , Hidrocarbonetos Policíclicos Aromáticos/química , Rios/química , Poluentes Químicos da Água/química , Bélgica , Cidades , Ecotoxicologia , França , Urbanização
13.
Sci Total Environ ; 521-522: 152-9, 2015 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-25829293

RESUMO

Various drug residues, pesticides and phthalates are ubiquitous in the environment. Their presence in the environment has attracted considerable attention due to their potential impacts on ecosystem functioning and on public health. In this work, 14 drug residues, 24 pesticides and 6 phthalates have been quantified in three matrices (in the dissolved phase, associated to suspended solid matter (SSM), and in sediment) collected from fifteen watercourses and rivers located in a highly industrialized zone at the cross-border area of Northern France and Belgium. The extractions have been carried out using accelerated solvent extraction (ASE) for solid matrices (SSM and sediment) and using solid phase extraction (SPE) for liquid matrix. The final extract was analyzed using GC-MS technique. Among the three classes of compounds, phthalates have been found at highest level compared to pesticides and drug residues. The Σ6PAE concentrations were ranging from 17.2±2.58 to 179.1±26.9µgL(-1) in dissolved phase, from 2.9±0.4 to 21.1±3.2µgL(-1) in SSM and from 1.1±0.2 to 11.9±1.8µgg(-1)dw in sediment. The Σ14drug residue concentrations were lower than 1.3µgL(-1) in the dissolved phases, lower than 30ngL(-1) associated to SSM and from nondetectable levels to 60.7±9.1ngg(-1)dw in sediment. For pesticides, all compounds were below the LOQ values in dissolved phase and in sediment, and only EPTC could be quantified in SSM.


Assuntos
Resíduos de Drogas/análise , Sedimentos Geológicos/análise , Praguicidas/análise , Ácidos Ftálicos/análise , Poluentes Químicos da Água/análise , Bélgica , Monitoramento Ambiental , França , Sedimentos Geológicos/química , Rios/química
14.
Environ Sci Technol ; 49(7): 4019-35, 2015 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-25730609

RESUMO

Because of their large and widespread application, phthalates or phthalic acid esters (PAEs) are ubiquitous in all the environmental compartements. They have been widely detected throughout the worldwide environment. Indoor air where people spend 65-90% of their time is also highly contaminated by various PAEs released from plastics, consumer products as well as ambient suspended particulate matter. Because of their widespread application, PAEs are the most common chemicals that humans are in contact with daily. Based on various exposure mechanisms, including the ingestion of food, drinking water, dust/soil, air inhalation and dermal exposure the daily intake of PAEs may reach values as high as 70 µg/kg/day. PAEs are involved in endocrine disrupting effects, namely, upon reproductive physiology in different species of fish and mammals. They also present a variety of additional toxic effects for many other species including terrestrial and aquatic fauna and flora. Therefore, their presence in the environment has attracted considerable attention due to their potential impacts on ecosystem functioning and on public health. This paper is a synthesis of the extensive literature data on behavior, transport, fate and ecotoxicological state of PAEs in environmental matrices: air, water, sediment, sludge, wastewater, soil, and biota. First, the origins and physicochemical properties of PAEs that control the behavior, transport and fate in the environment are reviewed. Second, the compilation of data on transport and fate, adverse environmental and human health effects, legislation, restrictions, and ecotoxicological state of the environment based on PAEs is presented.


Assuntos
Disruptores Endócrinos/química , Exposição Ambiental/efeitos adversos , Poluentes Ambientais/química , Ácidos Ftálicos/química , Animais , Poeira/análise , Ecossistema , Ecotoxicologia , Disruptores Endócrinos/metabolismo , Disruptores Endócrinos/toxicidade , Meio Ambiente , Poluentes Ambientais/metabolismo , Poluentes Ambientais/toxicidade , Ésteres/análise , Humanos , Ácidos Ftálicos/metabolismo , Ácidos Ftálicos/toxicidade , Esgotos/química , Solo/química , Poluentes do Solo/análise , Águas Residuárias
15.
Sci Total Environ ; 515-516: 162-80, 2015 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-25723871

RESUMO

Because of their widespread application, phthalates or phthalic acid esters (PAEs) are ubiquitous in the environment. Their presence has attracted considerable attention due to their potential impacts on ecosystem functioning and on public health, so their quantification has become a necessity. Various extraction procedures as well as gas/liquid chromatography and mass spectrometry detection techniques are found as suitable for reliable detection of such compounds. However, PAEs are ubiquitous in the laboratory environment including ambient air, reagents, sampling equipment, and various analytical devices, that induces difficult analysis of real samples with a low PAE background. Therefore, accurate PAE analysis in environmental matrices is a challenging task. This paper reviews the extensive literature data on the techniques for PAE quantification in natural media. Sampling, sample extraction/pretreatment and detection for quantifying PAEs in different environmental matrices (air, water, sludge, sediment and soil) have been reviewed and compared. The concept of "green analytical chemistry" for PAE determination is also discussed. Moreover useful information about the material preparation and the procedures of quality control and quality assurance are presented to overcome the problem of sample contamination and these encountered due to matrix effects in order to avoid overestimating PAE concentrations in the environment.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Ácidos Ftálicos/análise , Atmosfera/química , Meio Ambiente , Esgotos/química , Solo/química , Água/química
16.
Mar Pollut Bull ; 93(1-2): 284-93, 2015 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-25619918

RESUMO

Tripoli harbour is among the most important ports on the Mediterranean Sea eastern basin. The persistent organic pollutants (POPs) were monitored (28 PCBs, 16 PAHs and 18 Me-PAHs) in 15 stations of Tripoli harbour basins, which are influenced by anthropogenic activities. Total PAHs concentrations ranged from 243 to 2965 µg kg(-1)dw, total Me-PAH concentrations ranged from 54 to 1638 µg kg(-1)dw, while total PCB levels ranged from 18 to 302 µg kg(-1)dw. PCBs profiles were dominated by four and six-chlorinated congeners while the PAHs were dominated by four and five rings. For identifying pollution emission sources of PAHs, different ratios were used. The results show that the pollution origin was predominated by pyrogenic process related to the deposition of coal dust and the combustion of biomass and coal. Based on Sediments Quality Guidelines the biological adverse effects on aquatic ecosystems were expected rarely to occasionally for PAHs and PCBs contamination.


Assuntos
Sedimentos Geológicos/química , Poluentes Químicos da Água/análise , Carvão Mineral , Ecossistema , Monitoramento Ambiental , Líbano , Mar Mediterrâneo , Bifenilos Policlorados/análise , Hidrocarbonetos Policíclicos Aromáticos/análise
17.
Chemphyschem ; 11(18): 4019-27, 2010 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-21117122

RESUMO

The pseudo-first-order loss of coniferyl aldehyde, adsorbed on silicon dioxide particles, upon heterogeneous ozonolysis was monitored at various ozone mixing ratios in the absence and presence of simulated sunlight. For the first time we investigated the effect of light on the heterogeneous ozonolysis of coniferyl aldehyde adsorbed on silica particles. We found that UV-VIS light (λ>300 nm) does not impact the degradation of coniferyl aldehyde by ozone but induces an additional, slow photolysis of the aldehyde with a photolytic rate constant of ~10(-5) s(-1). In both cases, that is, in presence and/or absence of light, the heterogeneous ozonation kinetics are well described by an immediate gas-surface reaction formalism with light-independent rate constants of k(2nd)=(7.2±0.9)×10(-19) cm(3) molec(-1) s(-1) and (7.6±1.7)×10(-19) cm(3) molec(-1) s(-1) in the absence and presence of light, respectively. Five oxidation products: glycolic acid, oxalic acid, vanillin, vanillic acid and 3,4-dihydroxybenzoic acid were identified and confirmed by their corresponding standards. Vanillin and vanillic acid absorb light in the region λ>300 nm and thus can further participate in the direct and indirect photolysis processes of atmospheric relevance. A reaction mechanism is proposed in order to elucidate the ozonolysis reaction and to explain the reaction products.


Assuntos
Acroleína/análogos & derivados , Oxidantes Fotoquímicos , Ozônio , Fotólise , Dióxido de Silício/química , Acroleína/química , Adsorção , Cromatografia Gasosa-Espectrometria de Massas , Cinética , Luz , Oxidantes Fotoquímicos/química , Oxirredução , Ozônio/química
18.
Phys Chem Chem Phys ; 12(27): 7603-11, 2010 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-20502834

RESUMO

Light-induced heterogeneous reactions between gas-phase ozone and veratraldehyde adsorbed on silica particles were performed. At an ozone mixing ratio of 250 ppb, the loss of veratraldehyde largely increased from 1.81 x 10(-6) s(-1) in the dark to 2.54 x 10(-5) s(-1) upon exposure to simulated sunlight (lambda > 300 nm). The observed rates of degradation exhibited linear dependence with the ozone in the dark ozonolysis experiments which change in the non-linear Langmuir-Hinshelwood dependence in the experiments with simultaneous ozone and light exposure of the coated particles. When the coated silica particles were exposed only to simulated sunlight in absence of ozone the loss of veratraldehyde was about three times higher i.e. 5.97 x 10(-6) s(-1) in comparison to the ozonolysis experiment under dark conditions at 250 ppb ozone mixing ratio, 1.81 x 10(-6) s(-1).These results clearly show that the most important loss of veratraldehyde occurs under simultaneous ozone and light exposure of the coated silica particles. The main identified product in the heterogeneous reactions between gaseous ozone and adsorbed veratraldehyde under dark conditions and in presence of light was veratric acid.Carbon yields of veratric acid were calculated and the obtained results indicated that at low ozone mixing ratio (250 ppb) the carbon yield obtained under dark conditions is 70% whereas the carbon yield obtained in the experiments with simultaneous ozone and light exposure of the coated particles is 40%. In both cases the carbon yield of veratric acid exponentially decayed leading to the plateau ( approximately 35% of carbon yield) at an ozone mixing ratio of 6 ppm. Two reaction products i.e. 3-hydroxy-4-methoxybenzoic acid and 4-hydroxy-3-methoxybenzoic acid were identified (confirmed with the standards) only in the experiments performed under simultaneous ozonolysis and light irradiation of the particles.

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