Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 789
Filtrar
Mais filtros










Filtros aplicados

Base de dados
Intervalo de ano de publicação
1.
Chemosphere ; 255: 126864, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32402869

RESUMO

This work demonstrates the ability of aqueous phase corona discharge to chemically reduce bromate and chlorate ions, common disinfection byproducts, to bromide and chloride ions, respectively. A high voltage pulse was applied to a needle electrode, submerged in the target solution, to generate highly reactive oxidative and reductive species in a temperature-controlled reactor. Optimal water matrix conditions were sought through changing the solution pH, temperature, and dissolved oxygen concentration. Additionally, several oxidative species scavengers were investigated, including methanol, ethanol, sucrose, and D-sorbitol. Chemical reduction rates were improved at low pH (3.5). The presence of dissolved oxygen significantly reduced the chemical reduction rate, and thus high solution temperature (50 °C) also achieved better chemical reduction. All oxidative species scavengers improved the chemical reduction rate; however, methanol and ethanol were superior as these compounds generate hydrogen bubbles in the presence of plasma, which deoxygenates the solution further improving the chemical reduction rate. The application of this technology to 30 µM bromate and chlorate solutions, under optimal water matrix conditions and with the addition of 72 g/L-COD methanol, achieved greater than 95% removal of the target compounds within 60 min. Increasing the initial concentration of the target compounds to 300 µM required 90 and 150 min to achieve similar chemical reductions for bromate and chlorate, respectively.


Assuntos
Bromatos/química , Cloratos/química , Poluentes Químicos da Água/química , Brometos/química , Cloretos , Cloro , Desinfecção , Hidrogênio , Concentração de Íons de Hidrogênio , Metanol , Oxirredução , Temperatura , Água/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
2.
J Environ Manage ; 265: 110566, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32275236

RESUMO

This work focuses on disinfection of water using electrolysis with diamond coatings avoiding or minimizing the formation of hazardous chlorates and perchlorates using a special type of commercial cells designed by CONDIAS (Itzehoe, Germany) in two different sizes: the CabECO and the MIKROZON cells. In these cells, the electrolyte that separates the anode and cathode is a proton exchange membrane. This helps to minimize the production of perchlorate and this behavior is enhanced in the smallest cell for which the very low contact times between the electrodes and the water allows to avoid the production of perchlorates when operating in a single-pass mode, which becomes a really remarkable point. In this paper, we report tests in which we demonstrate this outstanding performance and we also explain the differences observed in the two cells operating with the same water.


Assuntos
Cloratos , Poluentes Químicos da Água , Diamante , Desinfecção , Eletrodos , Alemanha , Oxirredução , Percloratos
3.
Environ Geochem Health ; 42(3): 849-861, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31093815

RESUMO

Eutrophication has become great concern in recent years due to the fact that rivers, lakes, and reservoirs are the main drinking water source. Studies have been performed to enhance the removal of algae with ClO2 pre-oxidation, but there was high potential in the formation of chlorite and chlorate. In this study, ultra-sonication was employed to assist algae removal and control disinfection by-products formation in ClO2 pre-oxidation processes. It was found that solo ultra-sonication for 10 min (algae removal 86.11 ± 2.16%) could achieve similar algae removal efficiency as that with solo ClO2 (0.5 mg/L) pre-oxidation for 10 min (algae removal 87.10 ± 3.50%). In addition, no formations of chlorite and chlorate were detected in solo ultra-sonication process. Five-minutes ultra-sonication followed by 5-min 0.5 mg/L ClO2 treatment (total treatment time 10 min; algae removal 93.55 ± 3.22%) provided a better performance on algae removal compared to the solo ClO2 (0.5 mg/L) pre-oxidation for 10 min. Moreover, chlorite was undetectable. It suggests that the utilization of ultra-sonication in ClO2 pretreatment for algae removal has highly prevented the formations of chlorite and chlorate.


Assuntos
Compostos Clorados/química , Desinfecção/métodos , Eutrofização , Óxidos/química , Sonicação/métodos , Purificação da Água/métodos , Cloratos/química , Cloretos/química , Clorofórmio/química , Oxirredução , Água
4.
J Dairy Sci ; 103(2): 1208-1214, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31837793

RESUMO

The objective of this study was to assess the effects of electrochemically activated drinking water (ECW) on milk chlorate, milk perchlorate, milk iodine, milk composition, milk fatty acid profile, and overall performance of dairy cows. Ten Red Danish cows in mid-lactation (203 ± 31 d in milk; average ± SD) were chosen from these 2 groups for intensive sampling. The treated group drank water with 4 ppm of ECW (29 mg/L of chlorate of Neuthox, Danish Clean Water A/S, Sønderborg, Denmark). The treatment lasted 60 consecutive days, with milk and water sampling on d 0, 30, and 60. Additionally, milk samples from both the control group and treated group were taken on d 90 to assess if any carry-over effect was present. Interactions between period and milk yield and somatic cell for the full group and period and milk fat content and milk urea nitrogen in the selected animals occurred. Milk yield was not significantly affected by treatments. Milk fat, milk fatty acid profile, chlorate, perchlorate, and iodine contents were not significantly different between treatments. Milk urea increased, whereas ß-hydroxybutyrate and somatic cell count decreased significantly in the treated groups. Results showed that at a dosing of 4 ppm of ECW, both chlorate and perchlorate concentrations in milk (<0.002 mg/kg) were low, and no deleterious effects on milk production or milk chemical composition were observed. These data can be of use when assessing the effects of ECW on milk and milk powder chlorate and perchlorate levels and provide a context for assessing the potential for influencing human health under the conditions prevailing on a commercial dairy farm.


Assuntos
Água Potável/química , Leite/química , Ácido 3-Hidroxibutírico/análise , Animais , Bovinos , Cloratos/análise , Dinamarca , Dieta/veterinária , Técnicas Eletroquímicas , Ácidos Graxos/análise , Feminino , Iodo/análise , Lactação , Percloratos/análise
5.
Virol J ; 16(1): 134, 2019 11 12.
Artigo em Inglês | MEDLINE | ID: mdl-31718685

RESUMO

BACKGROUND: Duck tembusu virus (DTMUV, genus Flaviviruses, family Flaviviridae) is an emerging flavivirus that can infect a wide range of cells and cell lines in vitro, though the initial step of virus invasion remains obscure. METHODS: In this study, drug treatments that including heparin, chondroitin sulfate, heparinase I, chondroitinase ABC and trypsin were applied to detect the influence of DTMUV absorption, subsequently, the copy number of viral genome RNA was analyzed by quantitative real-time PCR. The inhibition process of viral absorption or entry by heparin was determined by western blotting, and the cytotoxicity of drug treated cells was detected by cell counting kit-8. RESULTS: We found that the desulfation of glycosaminoglycans (GAGs) with sodium chlorate had a significant effect on the adsorption of DTMUV in both BHK21 and DEF cells. Based on this result, we incubated cells with a mixture of DTMUV and GAGs competition inhibitors or pre-treated cells with inhibitors, after incubation with the virus, the NS5 expression of DTMUV and viral titers were detected. The data suggested that heparin can significantly inhibit the absorption of DTMUV in a dose dependent manner but not at the step of viral entry in BHK21 and DEF cells. Meanwhile, heparinase I can significantly inhibit DTMUV attachment step. CONCLUSIONS: Our results clearly proved that heparin sulfate plays an important role in the first step of DTMUV entry, viral attachment, in both BHK21 and DEF cells, which sheds light on the entry mechanism of DTMUV.


Assuntos
Flavivirus/fisiologia , Heparina/farmacologia , Ligação Viral/efeitos dos fármacos , Animais , Linhagem Celular , Cloratos/farmacologia , Cricetinae , Patos , Fibrinolíticos/farmacologia , Flavivirus/efeitos dos fármacos , Glicosaminoglicanos/metabolismo , Heparina Liase/farmacologia , Tripsina/farmacologia
6.
Se Pu ; 37(10): 1064-1070, 2019 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-31642285

RESUMO

An analytical method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for detecting chlorate and perchlorate residues in milk power. Chlorate and perchlorate in milk power were extracted using a 0.1% (v/v) formic acid-acetonitrile solution. The extract was centrifuged at 10000 r/min for 10 min, and the supernatant was cleaned up on a PRiME HLB column. Separation of chlorate and perchlorate was performed on an ion-exchange column (Thermo Scientific Acclaim TRINITY P1, 50 mm×2.1 mm, 3 µm) by gradient elution using acetonitrile and 20 mmol/L ammonium acetate solution as the mobile phase. The analytes were identified by MS/MS. Quantification was achieved using internal standards. Chlorate and perchlorate demonstrated good linearity in the ranges of 2.0-40.0 and 1.0-20.0 µg/L, respectively, with correlation coefficients (r2) greater than 0.999. The limits of quantification (LOQs) of chlorate and perchlorate were found to be 15.0 and 7.5 µg/kg, respectively. The recoveries of chlorate and perchlorate ranged from 89.24% to 107.85% at the three spike levels of 30.0, 60.0, and 120.0, and 15.0, 30.0, and 60.0 µg/kg, respectively, with relative standard deviations (RSDs) ranging from 3.15% to 10.42% (n=6). This method is convenient, rapid, accurate, and efficient, thus demonstrating its suitability for use in the determination of chlorate and perchlorate in milk power.


Assuntos
Cloratos/análise , Contaminação de Alimentos/análise , Leite/química , Percloratos/análise , Animais , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas em Tandem
7.
J Genet ; 982019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31544785

RESUMO

The cassava grows well on low-nutrient soils because of its high-affinity to absorb nitrate. However, the molecular mechanisms by which cassava adapts itself to this environment remain elusive, although we have cloned a putative gene named MeNRT2.1 which has a crucial role in high-affinity nitrate transporter from cassava seeding. Here, the expression pattern of MeNRT2.1 was further assessed using the GUS activity driven by MeNRT2.1 promoter in Arabidopsis transformation plants. The GUS activity was monitored over time following the reduction of nitrate supply. The GUS gene expression not only peaked in roots after 12 h in 0.2mM nitrate media, but also stained stems and leaves. Arabidopsis plants with overexpression of MeNRT2.1 increased the biomass compared to the wild type on rich nitrogen (N-full) media. However, chlorate sensitivity analysis showed that Arabidopsis plants expressing MeNRT2.1 were more susceptable to chlorate than wild type. Significantly, after growing for 15 days on media containing 0.2mM nitrate concentration, wild-type plants became yellowor died, while the transgenic MeNRT2.1 Arabidopsis plants maintained normal growth. With significant increases in the amount of 15NO- 3 uptake in roots, the MeNRT2.1 plants also increased the contents of chlorophyll and nitrate reductase. Taken together, these results demonstrate that MeNRT2.1 has an important role in adaptation to low nitrate concentration as a nitrate transporter.


Assuntos
Proteínas de Transporte de Ânions/metabolismo , Arabidopsis/metabolismo , Manihot/genética , Proteínas de Plantas/metabolismo , Proteínas de Transporte de Ânions/genética , Arabidopsis/efeitos dos fármacos , Arabidopsis/genética , Cloratos/toxicidade , Expressão Gênica/genética , Glucuronidase/metabolismo , Manihot/metabolismo , Nitratos/metabolismo , Proteínas de Plantas/genética , Raízes de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética
8.
J Dairy Res ; 86(3): 341-346, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31378206

RESUMO

The experiments reported in this research paper aimed to investigate differences in the levels of chlorate (CHLO), perchlorate (PCHLO), trichloromethane (TCM) and iodine residues in bulk tank (BT) milk produced at different milk production periods, and to monitor those levels throughout a skim milk powder (SMP) production chain (BTs, collection tankers [CTs], whole milk silo [WMS] and skim milk silo [SMS]). Chlorate, PCHLO and iodine were measured in SMP, while TCM was measured in the milk cream. The CHLO, TCM and iodine levels in the mid-lactation milk stored in the WMS were lower than legislative and industrial specifications (0.0100 mg/kg, 0.0015 mg/kg and 150 µg/l, respectively). However, in late-lactation, these levels were numerically higher than the mid-lactation levels and specifications. Trichloromethane accumulated in the cream portion after separation. Perchlorate was not detected in any of the samples. Regarding iodine, the levels in mid-lactation reconstituted SMP were higher than that required by manufacturers (100 µg/l), indicating that the levels in milk should be lower than 142 µg/l. The higher residue levels observed in late-lactation could be related to the low milk volume produced during that period and changes in sanitation practices, while changes in feed management could have affected iodine levels. This study could assist in controlling and setting limits for CHLO, TCM and iodine levels in milk, ensuring premium quality dairy products.


Assuntos
Resíduos de Drogas/análise , Contaminação de Alimentos/análise , Manipulação de Alimentos/métodos , Alimentos em Conserva/análise , Leite/química , Animais , Bovinos , Cloratos/análise , Clorofórmio/análise , Indústria de Laticínios/métodos , Feminino , Iodo/análise , Irlanda , Lactação/fisiologia , Percloratos/análise
9.
Molecules ; 24(15)2019 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-31362388

RESUMO

Alkaloids derived from plants have shown great medicinal benefits, and are often reported for their use in cardiovascular disease management. Aristotelia chilensis (Molina) Stuntz (Maqui) has shown important medicinal properties in traditional useage. In this study, we evaluated the effect of the indole-alkaloid aristoteline (ARI), isolated from leaves of Maqui, on vascular reactivity of isolated aortic rings from normotensive rats. ARI induced relaxation (100%) in a concentration-dependent manner in intact or denuded-endothelium aortic rings pre-contracted with phenylephrine (PE; 1 µM). However, a specific soluble guanylyl cyclase inhibitor (ODQ; 1 µM) significantly reduced the relaxation to ARI in aortic rings pre-contracted with PE. In the presence of ARI, the contraction induced by KCl or PE was significantly (p < 0.05) decreased. Interestingly, the potassium channel blockade with 10 µM BaCl2 (Kir), 10 µM glibenclamide (KATP), 1 mM tetraethylammonium (TEA; KCa1.1), or 1 mM 4-aminopyridine (4-AP; Kv) significantly (p < 0.05) reduced the ARI-induced relaxation. ARI significantly (p < 0.05) reduced the contractile response to agonist of CaV1.2 channels (Bay K8644; 10 nM), likely reducing the influx of extracellular calcium through plasma membrane. The mechanisms associated with this process suggest an activation of the potassium channels, a calcium-induced antagonism and endothelium independent vasodilation that possibly involves the nitric oxide-independent soluble guanylate cyclase pathway.


Assuntos
Alcaloides/química , Alcaloides/farmacologia , Bloqueadores dos Canais de Cálcio/química , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/química , Canais de Potássio/química , Animais , Aorta Torácica/efeitos dos fármacos , Aorta Torácica/metabolismo , Cloratos/farmacologia , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/metabolismo , Estrutura Molecular , Óxido Nítrico/metabolismo , Fenilefrina/farmacologia , Canais de Potássio/agonistas , Prostaglandinas/farmacologia , Ratos , Vasodilatação/efeitos dos fármacos , Vasodilatadores/química , Vasodilatadores/farmacologia
10.
Talanta ; 204: 189-197, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357281

RESUMO

It is fairly crucial to detect inorganic explosives through a sensitive and fast method in the field of public safety, nevertheless, the high non-volatility and stability characteristics severely confine their accurate on-site detection from a real-world surface. In this work, an efficient, simple and cost effective method was developed to fabricate uniform silver nanoparticles (AgNPs) immobilized on polyurethane (PU) sponge through the in-situ reduction of polydopamine (PDA) based on mussel-inspired surface chemistry, in virtue of a large quantities catechol and amine functional groups. The formed PU@PDA@Ag sponges exhibited high SERS sensitivity, uniformity and reproducibility to 4-Aminothiophenol (4-ATP) probe molecule, and the limit of detection was calculated to be about 0.02 nmol L-1. Moreover, these PU@PDA@Ag sponges could be served as excellent flexible SERS substrates to rapidly detect trace inorganic explosives with high collection efficiency via swabbing extraction. The detection limit for perchlorates (ClO4-), chlorates (ClO3-) and nitrates (NO3-) were approximately down to 0.13, 0.13 and 0.11 ng respectively. These flexible substrates not only could drastically increase the sample collection efficiency, but also enhance analytical sensitivity and reliability for inorganic explosive, and would have a great potential application in the future homeland security fields.


Assuntos
Substâncias Explosivas/análise , Nanopartículas Metálicas/química , Poliuretanos/química , Prata/química , Compostos de Anilina/química , Materiais Biomiméticos/química , Cloratos/análise , Indóis/química , Limite de Detecção , Nitratos/análise , Oxirredução , Percloratos/análise , Polímeros/química , Reprodutibilidade dos Testes , Análise Espectral Raman/métodos , Compostos de Sulfidrila/química
11.
Chemosphere ; 235: 757-766, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31280044

RESUMO

The results of the validation study of the LC-ESI-MS/MS method for the determination of chlorate (ClO3-), perchlorate (ClO4-) and bromate (BrO3-) in water and food samples are summarized. Towards this, 284 samples of drinking water were analysed, out of which the 69% contained chlorate above the limit of quantitation (LOQ) of 0.01 mg/L, with maximum amount of 1.1 mg/L. Only 6 samples were found to be positive with perchlorate at levels <0.01 mg/L. Bromate was detected in 5 drinking water samples at levels above the LOQ, at concentrations up to 0.026 mg/L. For the validation of the method in food, 108 blank samples were spiked with chlorate and perchlorate for the LC-MS/MS analysis at two levels. In total 247 food samples from the market of 19 different commodities including fruits, vegetables, cereals and wine, were analysed. The maximum concentration of chlorate was found at 0.83 mg/kg in a sample of cultivated mushrooms. The number of samples contaminated with perchlorate was also small, with all the determined concentrations below the LOQ of 0.05 mg/kg. Experiments for the chlorate reduction in drinking water, showed that reverse osmosis treatment is effective in particular with newly installed cartridges. Finally, according to the results of the pilot study when chlorinated water is used for the plant irrigation, accumulation of chlorate is observed, especially in the green parts of the plant. Perchlorate was also detected in leafy samples, although it was not present in the irrigation water.


Assuntos
Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Bromatos/análise , Cloratos/análise , Cromatografia Líquida/métodos , Frutas/química , Percloratos/análise , Projetos Piloto , Espectrometria de Massas em Tandem/métodos , Verduras , Purificação da Água
12.
Chemosphere ; 229: 68-76, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31075704

RESUMO

Chlorate ion ClO3- is formed as a result of the complex chemical interaction of ozone with chloride ion in aqueous solution. In neutral and basic solutions, chlorate is the main product. In acid solutions, the main product is molecular chlorine Cl2, and the yield of chlorate is 50-100 times lower. Dependencies have been studied of chlorate formation rate on significant experimental factors: concentrations of initial substances, ozone and chloride ion, acidity (pH), ionic strength and temperature of the reaction solution. The kinetic laws of chlorate generation have been established, and the expressions are given for rate constants of chlorate formation as functions of temperature and ionic strength. When tert-butanol is added to the reaction system, the formation of chlorate ceases, which is an evidence of the crucial role of free radical reactions in this process.


Assuntos
Cloratos/química , Cloretos/química , Ozônio/química , Purificação da Água/métodos , Cinética , Soluções
13.
J Appl Microbiol ; 126(5): 1508-1518, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30803130

RESUMO

AIMS: Determine the antimicrobial effects of 5 µmol ml-1 sodium chlorate, 9 µmol ml-1 nitroethane or 2-nitropropanol as well as lauric acid, myristic acid and the glycerol ester of lauric acid Lauricidin® , each at 5 mg ml-1 , against representative methicillin-resistant staphylococci, important mastitis- and opportunistic dermal-pathogens of humans and livestock. METHODS AND RESULTS: Three methicillin-resistant Staphylococcus aureus and two methicillin-resistant coagulase-negative staphylococci were cultured at 39°C in 5 µmol ml-1 nitrate-supplemented half-strength Brain Heart Infusion broth treated without or with the potential inhibitors. Results revealed that 2-nitropropanol was the most potent and persistent of all compounds tested, achieving 58-99% decreases in mean specific growth rates and maximum optical densities when compared with untreated controls. Growth inhibition did not persist by cultures treated solely with chlorate or nitroethane, with adaptation occurring by different mechanisms after 7 h. Adaptation did not occur in cultures co-treated with nitroethane and chlorate. The medium chain fatty acid compounds had modest effects on all the staphylococci tested except the coagulase-negative Staphylococcus epidermidis strain NKR1. CONCLUSIONS: The antimicrobial activity of nitrocompounds, chlorate and medium chain fatty acid compounds against different methicillin-resistant staphylococci varied in potency. SIGNIFICANCE AND IMPACT OF THE STUDY: Results suggest that differential antimicrobial activities exhibited by mechanistically dissimilar inhibitors against methicillin-resistant staphylococci may yield potential opportunities to combine the treatments to overcome their individual limitations and broaden their activity against other mastitis and dermal pathogens.


Assuntos
Antibacterianos/farmacologia , Cloratos/farmacologia , Ácidos Graxos/farmacologia , Staphylococcus aureus Resistente à Meticilina/efeitos dos fármacos
14.
J Appl Microbiol ; 126(6): 1643-1656, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30661281

RESUMO

Alicycliphilus is a promising candidate for participating in the development of novel xenobiotics bioremediation processes. Members of the Alicycliphilus genus are environmental bacteria mostly found in polluted sites such as landfills and contaminated watercourses, and in sewage sludges from wastewater treatment plants. They exhibit a versatile metabolism and the ability to use oxygen, nitrate and chlorate as terminal electron acceptors, which allow them to biodegrade xenobiotics under oxic or anoxic conditions. Pure cultures of Alicycliphilus strains are able to biodegrade some pollutants such as industrial solvents (acetone, cyclohexanol and N-methylpyrrolidone), aromatic hydrocarbons (benzene, toluene and anthracene), as well as polyurethane varnishes and foams, and they can even transform Cr(VI) to Cr(III). In addition, Alicycliphilus has also been identified in bacterial communities involved in wastewater treatment plants for denitrification, and the degradation of emerging pollutants such as triclosan, nonylphenol, N-heterocyclic aromatic compounds (indole and quinoline), and antibiotics (tetracycline and oxytetracycline). This work summarizes the current knowledge on the Alicycliphilus genus, describing its different metabolic characteristics, focusing on its xenobiotic biodegradation abilities and examining the distinct pathways and molecular bases that sustain them. We also discuss the progress made in genetic manipulation and 'omics' analyses, as well as Alicycliphilus participation in novel bioremediation strategies.


Assuntos
Comamonadaceae/genética , Comamonadaceae/metabolismo , Poluentes Ambientais/metabolismo , Xenobióticos/metabolismo , Biodegradação Ambiental , Cloratos/metabolismo , Comamonadaceae/classificação , Genoma Bacteriano/genética , Redes e Vias Metabólicas/genética , Nitratos/metabolismo , Oxigênio/metabolismo , Esgotos/microbiologia
15.
Chemosphere ; 218: 540-550, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30500715

RESUMO

Formation potential and speciation characteristics of two important groups of disinfection byproducts (DBPs), namely, trihalomethanes (THMs) and haloacetic acids (HAAS), during Cl2 and ClO2 treatment of water samples collected from three different sources, namely, sea, river, and reservoir, were investigated with reference to key controlling parameters. Formation of inorganic DBPs such as chlorate and chlorite was evaluated. Dissolved organic carbon (DOC) and UV absorbance (UV254) of the sea, river, and reservoir samples were 3.35 ±â€¯0.05, 3.12 ±â€¯0.05, and 3.23 ±â€¯0.05 mg/L and 0.062 ±â€¯0.01, 0.074 ±â€¯0.01, and 0.055 ±â€¯0.01 cm-1, respectively. For Cl2 and ClO2 treatments, the respective formation potential of THMs and HAAs from the three water sources studied exhibited unidentical trend suggesting that higher THM formation was not necessarily associated with higher HAA formation. On chlorination, the concentrations of total HAAs formed were 9.8 µg/L (sea), 12.8 µg/L (river), and 20.6 µg/L (reservoir) and total THM yields were 38.3 µg/L (sea), 18.8 µg/L (river), and 21.5 µg/L (reservoir) for a Cl2 dose of 1 mg/L and 30 min reaction time. The trend of formation of THMs and HAAs for Cl2 treatment was similar to that for ClO2 treatment. However, the amount of HAAs (3.5 µg/L (sea), 1.8 µg/L (river), and 1.9 µg/L (reservoir)) and THMs (not detected) formed was much lower than that formed during chlorination. Regardless of source water type, di-HAAs were the most favored HAAs, followed by tri-HAAs with a small amount of mono-HAAs formed for both Cl2 and ClO2 treatment. Chlorination yielded more THMs than HAAs, whereas it was reverse for chlorine dioxide treatment. Irrespective of treatment with ClO2 or Cl2, seawater samples showed the highest bromine incorporation percentage (BIP) in both THMs and HAAs followed by that for river and reservoir water samples. HAAs were found to be always associated with lower amount of BIP than THMs.


Assuntos
Desinfetantes/química , Trialometanos/análise , Poluentes Químicos da Água/química , Purificação da Água/métodos , Bromo/química , Cloratos/análise , Cloratos/química , Cloretos/química , Cloro/química , Compostos Clorados/química , Desinfetantes/análise , Desinfecção , Água Doce/análise , Água Doce/química , Halogenação , Índia , Óxidos/química , Água do Mar/análise , Água do Mar/química , Trialometanos/química , Poluentes Químicos da Água/análise
16.
mBio ; 9(5)2018 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-30254119

RESUMO

Nitrate respiration is a widespread mode of anaerobic energy generation used by many bacterial pathogens, and the respiratory nitrate reductase, Nar, has long been known to reduce chlorate to the toxic oxidizing agent chlorite. Here, we demonstrate the antibacterial activity of chlorate against Pseudomonas aeruginosa, a representative pathogen that can inhabit hypoxic or anoxic host microenvironments during infection. Aerobically grown P. aeruginosa cells are tobramycin sensitive but chlorate tolerant. In the absence of oxygen or an alternative electron acceptor, cells are tobramycin tolerant but chlorate sensitive via Nar-dependent reduction. The fact that chlorite, the product of chlorate reduction, is not detected in culture supernatants suggests that it may react rapidly and be retained intracellularly. Tobramycin and chlorate target distinct populations within metabolically stratified aggregate biofilms; tobramycin kills cells on the oxic periphery, whereas chlorate kills hypoxic and anoxic cells in the interior. In a matrix populated by multiple aggregates, tobramycin-mediated death of surface aggregates enables deeper oxygen penetration into the matrix, benefiting select aggregate populations by increasing survival and removing chlorate sensitivity. Finally, lasR mutants, which commonly arise in P. aeruginosa infections and are known to withstand conventional antibiotic treatment, are hypersensitive to chlorate. A lasR mutant shows a propensity to respire nitrate and reduce chlorate more rapidly than the wild type does, consistent with its heightened chlorate sensitivity. These findings illustrate chlorate's potential to selectively target oxidant-starved pathogens, including physiological states and genotypes of P. aeruginosa that represent antibiotic-tolerant populations during infections.IMPORTANCE The anaerobic growth and survival of bacteria are often correlated with physiological tolerance to conventional antibiotics, motivating the development of novel strategies targeting pathogens in anoxic environments. A key challenge is to identify drug targets that are specific to this metabolic state. Chlorate is a nontoxic compound that can be reduced to toxic chlorite by a widespread enzyme of anaerobic metabolism. We tested the antibacterial properties of chlorate against Pseudomonas aeruginosa, a pathogen that can inhabit hypoxic or anoxic microenvironments, including those that arise in human infection. Chlorate and the antibiotic tobramycin kill distinct metabolic populations in P. aeruginosa biofilms, where chlorate targets anaerobic cells that tolerate tobramycin. Chlorate is particularly effective against P. aeruginosalasR mutants, which are frequently isolated from human infections and more resistant to some antibiotics. This work suggests that chlorate may hold potential as an anaerobic prodrug.


Assuntos
Biofilmes/efeitos dos fármacos , Cloratos/farmacologia , Farmacorresistência Bacteriana , Pseudomonas aeruginosa/efeitos dos fármacos , Pseudomonas aeruginosa/genética , Anaerobiose , Antibacterianos/farmacologia , Proteínas de Bactérias/genética , Mutação , Nitratos/metabolismo , Oxidantes/farmacologia , Pró-Fármacos , Pseudomonas aeruginosa/metabolismo , Tobramicina/farmacologia , Transativadores/genética
17.
Environ Toxicol ; 33(11): 1182-1194, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30144278

RESUMO

Sodium chlorate (NaClO3 ) is widely used in paper and pulp industries and as a non-selective herbicide. Humans can be exposed to NaClO3 through contaminated drinking water due to its improper and unchecked usage in industries and as herbicide. NaClO3 is also present as a major stable by-product in drinking water that has been disinfected with chlorine dioxide. In this study, we have investigated the effect of a single acute oral dose of NaClO3 on rat kidney. Adult male Wistar rats were divided into one control and four NaClO3 treated groups that were orally given different doses of NaClO3 and euthanized 24 hr after the treatment. Oral administration of NaClO3 resulted in increased hydrogen peroxide levels, lipid, and protein oxidation while thiol and glutathione content and activities of brush border membrane enzymes were decreased in kidney in a NaClO3 dose-dependent manner. Significant alterations in the activities of enzymes involved in carbohydrate metabolism and antioxidant defense were also observed. Administration of NaClO3 induced DNA fragmentation and increased DNA-protein cross-linking. Histological studies showed marked damage in kidney from NaClO3 treated animals. These results strongly suggest that NaClO3 induces nephrotoxicity via redox imbalance that results in DNA and membrane damage, metabolic alterations and brush border membrane enzyme dysfunction.


Assuntos
Lesão Renal Aguda/induzido quimicamente , Cloratos/toxicidade , Herbicidas/toxicidade , Rim/efeitos dos fármacos , Microvilosidades/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Lesão Renal Aguda/metabolismo , Lesão Renal Aguda/patologia , Animais , Antioxidantes/metabolismo , Metabolismo dos Carboidratos/efeitos dos fármacos , Dano ao DNA , Glutationa/metabolismo , Rim/enzimologia , Rim/patologia , Rim/ultraestrutura , Masculino , Microvilosidades/enzimologia , Microvilosidades/patologia , Oxirredução/efeitos dos fármacos , Ratos , Ratos Wistar , Testes de Toxicidade Aguda
18.
Environ Sci Technol ; 52(11): 6317-6325, 2018 06 05.
Artigo em Inglês | MEDLINE | ID: mdl-29746105

RESUMO

Halides and natural organic matter (NOM) are inevitable in aquatic environment and influence the degradation of contaminants in sulfate radical (SO4•-)-based advanced oxidation processes. This study investigated the formation of chlorate in the coexposure of SO4•-, chloride (Cl-), bromide (Br-) and/or NOM in UV/persulfate (UV/PDS) and cobalt(II)/peroxymonosulfate (Co/PMS) systems. The formation of chlorate increased with increasing Cl- concentration in the UV/PDS system, however, in the Co/PMS system, it initially increased and then decreased. The chlorate formation involved the formation of hypochlorous acid/hypochlorite (HOCl/OCl-) as an intermediate in both systems. The formation was primarily attributable to SO4•- in the UV/PDS system, whereas Co(III) played a significant role in the oxidation of Cl- to HOCl/OCl- and SO4•- was important for the oxidation of HOCl/OCl- to chlorate in the Co/PMS system. The pseudo-first-order rate constants ( k') of the transformation from Cl- to HOCl/OCl- were 3.32 × 10-6 s-1 and 9.23 × 10-3 s-1 in UV/PDS and Co/PMS, respectively. Meanwhile, k' of HOCl/OCl- to chlorate in UV/PDS and Co/PMS were 2.43 × 10-3 s-1 and 2.70 × 10-4 s-1, respectively. Br- completely inhibited the chlorate formation in UV/PDS, but inhibited it by 45.2% in Co/PMS. The k' of SO4•- reacting with Br- to form hypobromous acid/hypobromite (HOBr/OBr-) was calculated to be 378 times higher than that of Cl- to HOCl/OCl-, but the k' of Co(III) reacting with Br- to form HOBr/OBr- was comparable to that of Cl- to HOCl/OCl-. NOM also significantly inhibited the chlorate formation, due to the consumption of SO4•- and reactive chlorine species (RCS, such as Cl·, ClO· and HOCl/OCl-). This study demonstrated the formation of chlorate in SO4•--based AOPs, which should to be considered in their application in water treatment.


Assuntos
Brometos , Poluentes Químicos da Água , Cloratos , Oxirredução , Sulfatos
19.
Artigo em Inglês | MEDLINE | ID: mdl-29617281

RESUMO

A constructed rapid infiltration (CRI) system is a new type of sewage biofilm treatment technology, but due to its anaerobic zone it lacks the carbon sources and the conditions for nitrate retention, and its nitrogen removal performance is very poor. However, a shortcut nitrification–denitrification process presents distinctive advantages, as it saves oxygen, requires less organic matter, and requires less time for denitrification compared to conventional nitrogen removal methods. Thus, if the shortcut nitrification–denitrification process could be applied to the CRI system properly, a simpler, more economic, and efficient nitrogen removal method will be obtained. However, as its reaction process shows that the first and the most important step of achieving shortcut nitrification–denitrification is to achieve shortcut nitrification, in this study we explored the feasibility to achieve shortcut nitrification, which produces nitrite as the dominant nitrogen species in effluent, by the addition of potassium chlorate (KClO3) to the influent. In an experimental CRI test system, the effects on nitrogen removal, nitrate inhibition, and nitrite accumulation were studied, and the advantages of achieving a shortcut nitrification–denitrification process were also analysed. The results showed that shortcut nitrification was successfully achieved and maintained in a CRI system by adding 5 mM KClO3 to the influent at a constant pH of 8.4. Under these conditions, the nitrite accumulation percentage was increased, while a lower concentration of 3 mM KClO3 had no obvious effect. The addition of 5mM KClO3 in influent presumably inhibited the activity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), but inhibition of nitrite-oxidizing bacteria (NOB) was so strong that it resulted in a maximum nitrite accumulation percentage of up to over 80%. As a result, nitrite became the dominant nitrogen product in the effluent. Moreover, if the shortcut denitrification process will be achieved in the subsequent research, it could save 60.27 mg CH3OH per litre of sewage in the CRI system compared with the full denitrification process.


Assuntos
Reatores Biológicos/microbiologia , Cloratos/química , Filtração/métodos , Esgotos/química , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/métodos , Bactérias/efeitos dos fármacos , Biofilmes/efeitos dos fármacos , Desnitrificação , Nitrificação
20.
ISME J ; 12(6): 1568-1581, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29476141

RESUMO

Dissimilatory perchlorate reduction is an anaerobic respiratory pathway that in communities might be influenced by metabolic interactions. Because the genes for perchlorate reduction are horizontally transferred, previous studies have been unable to identify uncultivated perchlorate-reducing populations. Here we recovered metagenome-assembled genomes from perchlorate-reducing sediment enrichments and employed a manual scaffolding approach to reconstruct gene clusters for perchlorate reduction found within mobile genetic elements. De novo assembly and binning of four enriched communities yielded 48 total draft genomes. In addition to canonical perchlorate reduction gene clusters and taxa, a new type of gene cluster with an alternative perchlorate reductase was identified. Phylogenetic analysis indicated past exchange between these gene clusters, and the presence of plasmids with either gene cluster shows that the potential for gene transfer via plasmid persisted throughout enrichment. However, a majority of genomes in each community lacked perchlorate reduction genes. Putative chlorate-reducing or sulfur-reducing populations were dominant in most communities, supporting the hypothesis that metabolic interactions might result from perchlorate reduction intermediates and byproducts. Other populations included a novel phylum-level lineage (Ca. Muirbacteria) and epibiotic prokaryotes with no known role in perchlorate reduction. These results reveal unexpected genetic diversity, suggest that perchlorate-reducing communities involve substantial metabolic interactions, and encourage expanded strategies to further understand the evolution and ecology of this metabolism.


Assuntos
Metagenoma , Metagenômica , Oxirredutases/genética , Percloratos/química , Cloratos/química , Cloro/química , Metabolismo Energético , Variação Genética , Funções Verossimilhança , Família Multigênica , Oxirredução , Estresse Oxidativo , Filogenia , Plasmídeos/metabolismo , Software
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA