Showing papers in "Toxicological & Environmental Chemistry in 2001"
TL;DR: In this article, the adsorption of Sb(V) ions from aqueous solutions onto commercially available activated alumina (AA) was investigated, and the optimum pH was found in the range of 2.8-4.3.
Abstract: The adsorption of Sb(V) ions from aqueous solutions onto commercially available activated alumina (AA) was investigated. AA has a much higher adsorption capacity than presently used adsorbents. Sb(V) ions are likely adsorbed through electrostatic attraction and/or specific adsorption mechanism, while the optimum pH is found in the range of 2.8–4.3. The Sb(V) ions adsorption capacities increase with increasing temperature. The addition of nitrate, acetate, arsenite, chloride, and silicate ions affected Sb(V) ions adsorption only slightly, while the coexisting ascorbate, arsenate, phosphate, sulfate, EDTA, tartrate, and citrate ions substantially depressed Sb(V) ions adsorption.
56 citations
TL;DR: The results of field and laboratory studies on adsorption/desorption, leaching, dissipation, bound residue formation and metabolism of DDT, DDE, lindane, parathion, malathion and carbofuran in tropical soils in various regions in Kenya are summarized in this article.
Abstract: Results of field and laboratory studies on adsorption/desorption, leaching, dissipation, bound residue formation and metabolism of DDT, DDE, lindane, parathion, malathion, dimethoate and carbofuran in tropical soils in various regions in Kenya are summarized in this paper. Based on reported half‐lives of dissipation in temperate soils, DDT, DDE and lindane were found to dissipate much more rapidly in tropical soil conditions with half‐lives of dissipation of 64.5–245.6, 145 and 5–8 days, respectively. Carbofuran (t 1/2 = 66–115.5 days), malathion (t 1/2 = 36.7–770 days), parathion (t 1/2 = 48days) and dimethoate (t 1/2 = 72 days) were also less persistent. The major environmental factors, wind, rainfall, solar radiation intensity and soil moisture content that contributed to this rapid disappearance are presented, explaining also the influence of important soil characteristics such as pH, % organic carbon, texture and microbial activity on pesticide distribution and degradation in soil.
41 citations
TL;DR: The distribution of heavy metals (Hg, Cd, Pb, Cr, Zn, Cu, Ni, Mn) were investigated in surficial sediments of Izmir Bay as mentioned in this paper.
Abstract: The distribution of heavy metals (Hg, Cd, Pb, Cr, Zn, Cu, Ni, Mn) were investigated in surficial sediments of Izmir Bay. The data were collected during cruises in July 1997 and January 1998, in the framework of a Izmir Bay Marine Research Project supported by Izmir Metropolitan Municipality. Heavy metal concentrations in the sediment samples showed significant enrichments during sampling periods from Inner Bay. Outer and Middle Bays show low levels of heavy metal enrichments except mouth of Gediz River. Gediz is the major source of anthropogenic input into the Outer Bay.
24 citations
TL;DR: In this article, the triketone herbicide mesotrione has been applied pre-emergence at the dose of 150 g a.i.d. ha−1 on corn fields grown within the same period of time at different sites on clay, loam, sandy loam or sandy soils.
Abstract: The triketone herbicide mesotrione has been applied pre‐emergence at the dose of 150 g a.i. ha−1 on corn fields grown within the same period of time at different sites on clay, loam, sandy loam or sandy soils. During the crops and one month after the corn harvest, the mobility of mesotrione has been measured in the 0–20 cm surface soil layer, soil samples being taken in the 0–2,2–4,4–6,6–8, 8–10, 10–15 and 15–20 cm surface soil layers. During the first month after the treatment, mesotrione remained in the 0–2 cm surface soil layer. Thereafter, mesotrione was at a higher concentration in a 2 cm‐thick soil layer which progressively moved down in the clay, loam and sandy loam soils. In the sand soil, mesotrione moved down as a uniform diffusion, its concentration being similar in all the 2 cm‐thick layers of the 0–10 cm soil surface layer. Low mesotrione residues (6–10 ug kg−1 dry soil) attained the 10–15 cm layer faster in the clay and sand soils than in the loam and sandy loam soils. Mesotrione was not det...
24 citations
TL;DR: The results of the present study show that arsenic oxides are associated well with iron and aluminium oxide deposits on the particle surface of coal fly ash NIST•1633b.
Abstract: The leaching of arsenic from coal fly ash NIST‐1633b and NIST‐2689 was tried with various lixiviants. The leaching of arsenic was found to have taken place readily and to be dependent on both the equilibria of dissolution/precipitation and adsorption/desorption in the leaching system. The arsenic leaching intensity was significantly elevated by the use of proper chelating agents, which is supposed to be owing to the formation of metal (aluminium and/or iron)‐chelate complexes followed by an enhanced binding with arsenate ions. The results of the present study show that arsenic oxides are associated well with iron and aluminium oxide deposits on the particle surface of coal fly ash NIST‐1633b. Surface enrichment for arsenic was also examined and confirmed by XPS measurement. The leaching percentages of arsenic on the surface from XPS detection were in good agreement with those in bulk found in the leaching tests.
22 citations
TL;DR: In this paper, the ability of flyash activated carbon (AC) prepared from raw materials such as wood, ricehusk, coconut shell, groundnut shell and bamboo dust to adsorb acetic acid (AA) from water has been studied.
Abstract: The ability of flyash‐activated carbon (AC) ‐ prepared from raw materials such as wood, ricehusk, coconut shell, groundnut shell and bamboo dust and commercial activated carbon (CAC) to adsorb acetic acid (AA) from water has been studied. The percentage of AA adsorbed increased with decrease in initial concentration of AA and particle size of the adsorbent and increased with the increase in contact time and adsorbent dosage. Flyash blended with wood carbon was found to have the maximum sorption potential. The adsorption process followed a first order kinetics and the data was modelled with Freundlich and Langmuir adsorption isotherms. Natarajan and Khalaf, Lagergren, Bhattacharya and Venkobachar and intraparticle diffusion equations were found applicable. From a comparative account of the adsorptive capacity of various flyash blends it was obvious that the flyash‐AC blends show a significant affinity and capacity compared to CAC in the removal of acetic acid from water. There seems to be good sco...
17 citations
TL;DR: In a study performed from 1996 to 1998 atrazine was the herbicide that showed the highest frequency of detection as mentioned in this paper, in the 177 ground water samples collected 62% were contaminated with Atrazine, 30% with alachlor and 12% with metolachlor.
Abstract: In irrigated maize areas of an important Portuguese agricultural area, Ribatejo and Oeste Region, alachlor, atrazine and metolachlor were detected in ground water. During the study performed from 1996 to 1998 atrazine was the herbicide that showed the highest frequency of detection. In the 177 ground water samples collected 62% were contaminated with atrazine, 30% with alachlor and 12% with metolachlor. All these herbicides were detected both in ground water for human consumption and for irrigation, in some cases above 0.1 ug/L. The maximum levels quantified were 13μg/L for alachlor, 30μg/L for atrazine and 56 μg/L for metolachlor. Seasonal variation of residues in ground water it is also presented through several examples of studies performed during the period 1991–1999.
16 citations
TL;DR: In this paper, surface sediments were collected from Elefsis Bay (Greece), an area receiving important industrial and domestic pollution, between 1994 and 1995, and analyzed for composition of aliphatic hydrocarbons (AHC) and polycylic aromatic hydrocarbon (PAH) by GC/MS, and several diagnostic indexes, such as unresolved/resolved compounds ratio (U/R), carbon preference index of n−alkanes (CPI), pristane/phytane ratio (Pr/Ph), identification of specific pentacyclic
Abstract: Surface sediments were collected from Elefsis Bay (Greece), an area receiving important industrial and domestic pollution, between 1994 and 1995. The sediments were analyzed for composition of aliphatic hydrocarbons (AHC) and polycylic aromatic hydrocarbons (PAH) by GC/MS. AHC concentrations over all sampling periods and stations ranged from 85.7 to 1062 μg/g dry sediment, while PAH concentrations ranged from 481 to 11182 ng/g dry sediment. These levels were comparable to those reported for other coastal areas highly influenced by industrial and urban effluents. Several diagnostic indexes, such as unresolved/resolved compounds ratio (U/R), carbon preference index of n‐alkanes (CPI), pristane/phytane ratio (Pr/Ph), identification of specific pentacyclic triterpanes and distribution patterns of PAH as well as specific ratio values of PAH compounds were used in order to distinguish between natural and diverse anthropogenic hydrocarbon inputs.
14 citations
TL;DR: In this article, heavy metal pollution in surface sediments of the Lagoon of Venice (Italy) was investigated, focusing on the evaluation of the amounts of heavy metals that can potentially be released into the overlying water column, under particular environmental conditions, thus becoming bioavailable.
Abstract: In this study heavy metal pollution in surface sediments of the Lagoon of Venice (Italy) was investigated. Attention was focused on the evaluation of the amounts of heavy metals that can potentially be released into the overlying water column, under particular environmental conditions, thus becoming bioavailable. To this end, the partitioning of heavy metals among different geochemical phases was determined by a procedure of sequential selective extractions. This approach can provide useful information for assessing the risk posed to the Lagoon ecosystem by metal contaminated sediments and for estimating the anthropogenic heavy metal content. In general, higher levels of contamination were found in sediments sampled in areas situated in the proximity of sources of pollutants and in degraded sites, which presented limited water circulation and prevailing anoxic conditions. The results of the sequential extraction procedure showed that partitioning is dependent on the metal considered: in particular, Pb, Cu...
14 citations
TL;DR: In this article, the effects of scavengers; hydrogen peroxide, H2O2 (an electron scavenger), and methanol, CH3OH (a hole scavenger) were examined for the photocatalytic degradation of 1,3-dihydroxybenzene (1,3−DHB), by following the carbon dioxide (CO2) formation in a gas recycling reactor.
Abstract: Effects of scavengers; hydrogen peroxide, H2O2 (an electron scavenger), and methanol, CH3OH (a hole scavenger) are examined for the photocatalytic degradation of 1,3‐dihydroxybenzene (1,3‐DHB), by following the carbon dioxide (CO2) formation in a gas recycling reactor. Addition of H2O2 as an electron trap enhances the CO2 formation rate for 1,3‐DHB, but there is a limit for the concentration of H2O2 above which hydroxyl radicals (*OH) are consumed in other reactions rather than taking part in oxidative routes. CH3OH being an hole scavenger decreases the degradation rate by reacting with photogenerated holes as well as *OH radicals.
12 citations
TL;DR: In this article, a high performance liquid chromatographic method was developed to determine pesticides in river water as both dissolved phase and suspended phase, and the results of the overall procedure were 78-114% for filtered river water and 75-107% for suspended solids.
Abstract: A high performance liquid chromatographic method has been developed to determine pesticides in river water as both dissolved phase and suspended phase. The target pesticides were eight herbicides, asulam, diuron, flazasulfuron, linuron, MCPB, mecoprop, pyrazosulfuron‐ethyl and siduron, and two fungicides, oxine‐copper and thiram. The pesticides in filtered river water were extracted with styrene‐divinylbenzene copolymer and were eluted with acetonitrile. The pesticides on suspended solids were extracted ultrasonically with acetonitrile. Each eluate was concentrated and analyzed by HPLC with multiwavelength detector. Recoveries of the pesticides in the overall procedure of this method were 78–114% for filtered river water and 75–107% for suspended solids. The limits of detection in water and suspended solids ranged from 0.1 to 0.9 μg/L and 1 to 7 μg/g, respectively. Pesticide distribution between soluble phase and suspended phase in river water was measured by this method.
TL;DR: In this paper, the sorption process of tribenuron methyl, a sulfonylurea herbicide, on the hydroxyapatitic and fluoroapatite minerals has been studied using batch method.
Abstract: The sorption process of tribenuron‐methyl, which is a sulfonylurea herbicide, on the hydroxyapatite and fluoroapatite minerals has been studied using batch method. Desorption of this pesticide from the solid is also investigated using column method. From UV‐visible data, it was found that the pesticide was more removed with the hydroxyapatite than with fluoroapatite samples. Using 1 g of HAp and of FAp, the maximum removed amount of tribenuron methyl from a solution of 2.5 × 10−4mol/L was respectively 1.65 × 10−4mol/L and 0.53 × 10−4mol/L. This is related to the specific surface area and to the solubility of minerals.
TL;DR: In this article, a study of photochemical degradation of a reactive dye (remazol brilliant blue R) by using ZnO in the presence of sodium carbonate is reported.
Abstract: In the present work a study of photochemical degradation of a reactive dye (remazol brilliant blue R) by using ZnO in the presence of sodium carbonate is reported. When the decolorization of the dye was used as analytical response we observed that in the presence of carbonate the chemical structure of the chromophoric group was modified with high efficiency, resulting in almost total decolorization at reaction times of about 20 min. At the same pH value, but in the absence of sodium carbonate, the total decolorization was achieved in a time higher than 60 min. The signal on the ultraviolet region was more resistant to the photochemical process, showing degradation rates of about 95% in the presence of carbonate and 80% in the absence of them, at a reaction time of 60 min. A very resembling result was observed when the total organic carbon content was used as degradation response. Degradation higher than 80% was observed in the presence of carbonate at a reaction time of 120 min. In the absence of carbonat...
TL;DR: The apparent aqueous solubility of the endocrine disruptor in hydroxypropylcyclodextrin (HP•CD) solutions was investigated for evaluating the remediation of soil contamination and ground water pollution as discussed by the authors.
Abstract: The apparent aqueous solubility of the endocrine disruptor in hydroxypropyl‐cyclodextrin (HP‐CD) solutions was investigated for evaluating the remediation of soil contamination and ground water pollution. The apparent solubility of bisphenol A (BPA) in water was significantly increased in HP‐CD solutions. The solubilization effect of HP‐CD's is caused by the formation of inclusion complexes of BPA and cyclodextrin. The relative aqueous‐phase concentration of BPA linearly increased with increasing HP‐CD concentration. The solubility of BPA increased in the order of the addition of HP‐a‐CD, HP‐7‐CD, and HP‐s‐CD. However, it did not depend upon the degree of hydroxypropylation substitution. It is concluded that HP‐CD may be utilized for the remediation of soil contamination.
TL;DR: Extractable, organically bound chlorine (EOCl) concentrations in environmental samples have been used as one of the measures of pollution by chlorinated organics as discussed by the authors, and they have been shown to be the highest in the total EOX family followed by organobromines and organoiodines.
Abstract: Extractable, organically bound chlorine (EOCl) concentrations in environmental samples have been used as one of the measures of pollution by chlorinated organics. Extractable organohalo‐gens (EOX = EOCl + EOBr + EOI) were measured in surface sediments and mussel tissues collected at selected locations in the Kentucky (KY) Lake and KY Dam Tailwater, USA. In sediments, EOX concentrations ranged from 0.22 to 0.90 μgg ‐1 dry wt. The sediment EOCl concentrations recorded in Kentucky Lake and KY Dam Tailwater were lower than those reported for sediments from industrial effluent contaminated sites. In freshwater mussel tissues, concentrations varied between 17.7 and 43.35 μgg ‐1 dry wt. Concentrations of EOCl measured in the tissues were comparable with those reported in fish and shellfish from PCBs and other chlorinated hydrocarbon contaminated sites. Extractable organochlorines (EOCl) were the highest in the total EOX family followed by organobromines and organoiodines. PCBs and chlorinated pesticides constitu...
TL;DR: In this paper, a pre-leaching of coal fly ash prior to disposal by a natural chelating agent, sodium gluconate (SG), was proposed and studied.
Abstract: The present study deals with the development of an efficient and reliable process for safe disposal of coal fly ash to remove arsenic that has been found to be the most easily leachable and hazardous heavy metal in coal fly ash. Pre‐leaching of fly ash prior to disposal by a natural chelating agent, sodium gluconate (SG), was proposed and studied. Several operational factors influencing arsenic leachability, such as concentration of SG solution, liquid to solid ratio, pH, length of leaching time and leaching temperature were examined. Arsenic was found to leach out substantially with SG, but almost no further release was observed from the ash pre‐leached by SG. After the pre‐leaching treatment, the desirable high buffering capacity of the ash was well sustained. SG solution was effectively regenerated by activated alumina adsorption so that it could be successfully reused for multiple leaching/adsorption cycles.
TL;DR: The levels of cadmium, copper, mercury, nickel, lead and zinc in nine striped dolphins stranded dead on the beach in 1996 and 1997 have been worked out.
Abstract: As part of a program monitoring the contamination of Cetaceans by heavy metals on the French Mediterranean coast, the levels of cadmium, copper, mercury, nickel, lead and zinc in nine striped dolphins (Stenella coeruleoalba), stranded dead on the beach in 1996 and 1997, have been worked out. The results obtained were compared to those of a similar study carried out in 1990 and 1991 on the same species. A significant decrease in the concentrations of copper, mercury, nickel and lead was shown, as well as a slight decrease in the concentrations of cadmium. Contamination by zinc was not lower and remain rather high. These results are most likely the consequence of the efforts made to clean up the coast, inadequat as it may be. Indeed, the metallic contents of the most contaminated dolphins still remain high and pose a toxicological problem which is discussed, with emphasis on mercury. Cetacean are reliable biological indicators and irrefutable evidence of the chronical poisoning of the sea and of the danger ...
TL;DR: Kinetics studies on removal of the colour showed that the decolorization rate was several times faster than the degradation rate of glucose for a range of dye concentrations between 60mg/L and 400 mg/L.
Abstract: Wool dyeing wastewater contains xenobiotic compounds that can be removed by biotechnological processes. Studies on various dyes showed that anaerobic processes are suitable to alter azo dyes as a first step of the biodegradation process. These compounds are reduced by anaerobic consortia to aromatic amines and its ultimate degradation can be achieved by a further aerobic treatment. Studies on degradation rate of an wool acid dye were performed in batch systems inoculated with anaerobic biomass. A commercial diazo dye, Acid Red 73, was added to the synthetic medium in which glucose was used as sole carbon source. Results indicated that the Acid Red 73 was partially degraded by a mixed culture of anaerobic bacteria and a decolorization of 90% was obtained. Kinetics studies on removal of the colour showed that the decolorization rate was several times faster than the degradation rate of glucose for a range of dye concentrations between 60 mg/L and 400 mg/L. A first order kinetic model was used for d...
TL;DR: In this paper, the authors deal with the application of different multivariate statistical approaches to a pot water data set from Athens, Greece, which represents analytical monitoring data for 16 potable water parameters (turbidity, pH, free acidity, total hardness, chloride, sulfate, nitrate, nitrite, calcium, magnesium, sodium, chemical oxygen demand, dry residue, conductivity, phosphate and silicon dioxide).
Abstract: The present study deals with the application of different multivariate statistical approaches to a pot water data set from Athens, Greece. The set represents analytical monitoring data for 16 potable water parameters (turbidity, pH, free acidity, total hardness, chloride, sulfate, nitrate, nitrite, calcium, magnesium, sodium, chemical oxygen demand, dry residue, conductivity, phosphate and silicon dioxide) measured in samples collected at 17 different sampling sites (3 sites of the water purification complex near Athens, 3 sites of lake system Iliki, 5 sites of lake system Marathonas and 6 sites of lake system Mornos) during 6 bimonths intervals in 1998. Both unsupervised and supervised environmetrical methods were used for data treatment: two‐ and multi‐way principal component analysis (PCA and MPCA‐Tucker 3 model) and CART (partitioning tree), respectively. It has been found that “rural”; and “urban”; conditional factors are responsible for the site spatial separation and “salinity”; and “turbi...
TL;DR: In this paper, the effects of carbonate and carbonate substitutions in apatite (Ap) on Cd2+ sorption capacity from aqueous solutions (pH = 6) were examined on precipitated apatites by a batch method.
Abstract: Effects of fluoride and carbonate substitutions in apatite (Ap) on Cd2+ sorption capacity from aqueous solutions (pH = 6) were examined on precipitated apatites by a batch method. Chemical, XRD, FTIR, BET and TEM analyses were used. The sorption of Cd2+ on Ap proceeds mainly by an ion exchange mechanism. The most important factor influencing Aps sorption capacity is the specific surface area. The amount of Cd2+ bound reaches 58 mmol/100 g Ap for hydroxyapatite, the increase in carbonate and fluoride content diminishes the sorption of Cd2+ to 5.5mmol/100g Ap. The removal of structural water from Ap has no significant effect on the Cd2+ sorption capacity.
TL;DR: In this paper, a denitrifying bacterium was isolated from activated sludge after enrichment on 4-chlorophenol under anoxic, denitrating conditions, and the microbial degradation of 4-chlorophenol by this bacterium, with nitrate as the only electron acceptor, was investigated.
Abstract: A denitrifying bacterium was isolated from activated sludge after enrichment on 4‐chlorophenol under anoxic, denitrifying conditions, and the microbial degradation of 4‐chlorophenol by this bacterium, with nitrate as the only electron acceptor, was investigated. The bacterium was capable of degrading up to 5 mM 4‐chlorophenol with stoichiometric release of chloride under denitrifying conditions. Anaerobic degradation of 4‐chlorophenol was dependent on nitrate as an electron acceptor. Nitrate (10 mM) severely inhibited the growth by the toxic effect of the accumulated nitrite. The optimum nitrate concentration for cell growth and chlorophenol degradation was 6 mM.
TL;DR: In this article, the kinetics of the photocatalytic degradation of aniline has been investigated experimentally in a batch-type photoreactor using TiO2 P25 Degussa as the primary intermediate.
Abstract: The kinetics of the photocatalytic degradation of aniline has been investigated experimentally. The reactions have been carried out in a batch‐type photoreactor using TiO2 P25 Degussa as the photocatalyst. The effects of the catalyst loading, H2O2, the initial concentration of aniline and the added Cu2+ ions on the degradation rate have been determined. With the intention of predicting the primary intermediates, geometry optimization of the aniline molecule has been performed with the semi‐empirical PM3 method. The molecular orbital calculations have been carried out by an SCF method using RHF formalism. Based on the results of the quantum mechanical calculations, two different primary intermediates have been determined.
TL;DR: In this paper, the interaction between atrazine, a triazine herbicide, and a series of decay fungi was characterized in terms of biodegradation of the herbicide and its influence on fungal growth.
Abstract: The interaction between atrazine, a triazine herbicide, and a series of decay fungi was characterized in terms of biodegradation of the herbicide and its influence on fungal growth. The following fungi were studied: thermophilic cellulolytic (Penicillium sp. 13) and noncellulolytic (Humicola lanuginosa sp. 5 and 12) strains isolated from self‐heated plant composts, mesophilic diphenol oxidase producing strain Mycelia sterilia INBI 2–26, white‐rot fungi Cerrena maxima, Coriolopsis fulvocinerea and Coriolus hirsutus. Competitive enzyme immunoassay was elaborated for detection of atrazine in cultural liquid. During agar plate cultivation the growth of Humicola sp. 5 was promoted by atrazine whereas the growth of Humicola sp. 12 and Penicillium sp. 13 was suppressed whereas M. sterilia INBI 2–26 was not affected by the herbicide. Neither atrazine‐accelerated nor atrazine‐depressed thermophilic strains decomposed atrazine during 21‐day cultivation according to ELISA data. In contrast, white‐rot fungi Coriolus ...
TL;DR: In this paper, the distribution of PAHs in a river ecosystem was studied by sampling of four abiotic compartments (surface water, suspended matter, pore water and sediments) under two different hydrological conditions.
Abstract: Distribution of PAHs in a river ecosystem was studied by sampling of four abiotic compartments (surface water, suspended matter, pore water and sediments) under two different hydro‐logical conditions. PAHs were detected at significant concentrations in both the solid and aqueous phase of the river ecosystem. Water concentrations were relatively low despite greater contamination of sediments. Lower MW PAHs were prevailing in the dissolved phase, higher MW PAHs in particulate materials. Concentrations of PAHs in surface waters were greater in summer than in fall. PAHs composition in the sediments was found to be relatively uniform across sites reflecting combustion generated PAH profile. Correlation and multivariate statistical analysis have shown differences between PAH patterns in solid and water samples. In aquatic samples and suspended matter, principal component analysis distinguished two separated groups of PAHs with different distribution depending on their molecular weight. In‐situ partition coeffic...
TL;DR: In this paper, a Quantitative Structure-Property Relationship (QSPR) prediction equation was developed for 19 aliphatic amines: log(K q) = 71.639 + 7.148.
Abstract: From the quenching rates of singlet oxygen by aliphatic amines, a Quantitative Structure‐Property Relationship (QSPR) prediction equation was developed for 19 aliphatic amines: log(K q) = 71.639 + 7.148 Ehomo‐ 0.0146a n=19, R = 0.911, SE = 0.892, F =36.653, P <0.00001 It was found that the quenching rate depends on two factors: the ionization potential and number of substituents and their size. The quenching rates of some substituted quinolines were determined according to B. Monroe's method. 8‐Methylaminoquinoline shows greater quenching rate than the traditional quencher l,4‐diazobicyclo‐[2.2.2]octane; it can be used as a good antioxidant.
TL;DR: In this paper, the roles played by copper in dibenzo-p-dioxin formation from the precursor phenol have been investigated using ab initio molecular orbital calculation, and the following catalytic roles of copper has been identified: stabilization of the total energy owing to the absorption of phenol, reduction of oxygen-hydrogen bond strength in phenol and reduction of steric effect of hydrogen atom in pre-Dioxin.
Abstract: The roles played by copper in dibenzo‐p‐dioxin formation from the precursor phenol have been investigated using ab initio molecular orbital calculation, and the following catalytic roles of copper has been identified: (i) stabilization of the total energy owing to the absorption of phenol, (ii) reduction of oxygen‐hydrogen bond strength in phenol, and (iii) reduction of steric effect of hydrogen atom in pre‐dioxin. The catalytic effect of copper has been shown in terms of the smaller apparent activation energy. In the case of polychlorinated dibenzo‐p‐dioxins generation from precursor polychlorinated phenols, the catalytic roles (i), i.e., the stabilization of the total energy of precursor, would become even stronger. On the other hand, the catalytic roles (ii) and (iii) are unchangeable regardless of the existence of substituted chlorine atom.
TL;DR: The mutagens or carcinogens were detected in air pollutants from several sources, including combustion products such as diesel exhaust, coal, terchimney soot, fly ash, photocopier toners, cigarette smoke, and other environmental samples as mentioned in this paper.
Abstract: The mutagens or carcinogens were detected in air pollutants from several sources, including combustion products such as diesel exhaust, coal, terchimney soot, fly ash, photocopier toners, cigarette smoke, and other environmental samples. Air Particulate samples for total suspended particle (TSP) was collected from August to December 1999 at Hungkuang Institute of Technology (HKIT) site in central Taiwan, Sha‐Lu. Their mutagenicity was examined with Salmonella Typhimurium TA98 and TA100 in presence or absence of S9 mix. The mutagenicity showed a good correlation with amounts of the acetone extractable matter of airborne particulates. The carcinogenic polycyclic aromatic hydrocarbons (PAHs) in the airborne particulates were extracted by an organic solvent and determined by High Performance Liquid Chromato‐graphy with photodiode array detection (HPLC/PDA). The results indicated that the amounts of acetone extractable matters of air samples showed a significant correlation with direct (r = .87) and indirect m...
TL;DR: In this paper, the chemical composition of rainfall was somehow characterized by high level of acid precursors, especially sulphates of possible marine and transboundary origin, mainly Saharan dust, with higher depositions in the south-eastern sectors.
Abstract: Samples of wet and dry depositions were collected during the period December 1996‐September 1998 at 16 stations located at different latitudes in the Campania Region (southwest Italy). Most of the rainwater samples showed neutral to alkaline reaction, with pH values below 5.50 only in the southern part of the study area. Chemical composition of rainfall was somehow characterized by high level of acid precursors, especially sulphates of possible marine and transboundary origin, mainly Saharan dust, with higher depositions in the south‐eastern sectors. No correlation was found between H+ and strong acidic anions (non marine sulphate and nitrate), as well as between SO4 2− and Ca2+ and acidic species and H+. Concentrations of trace metals (zinc, copper, lead) and Ca2+ showed distinct east‐west gradient in dry deposition as a possible consequence of long distance transport of Saharan dust. The mineralogy of the dry contributions revealed the prevalence of quartz, feldspars, illite, chlorite and smectite. In s...
TL;DR: In this paper, the degradation of pentachlorophenol (PCP) by photo-Fenton reaction was facilitated in the presence of humic acid (HA), and the degradation kinetics of PCP were investigated for six types of phenolic acids.
Abstract: At pH = 5.0, the degradation of pentachlorophenol (PCP) by the photo‐Fenton reaction was facilitated in the presence of humic acid (HA). To identify the functional groups in HA that contributed to this facilitation, the degradation kinetics of PCP were investigated for six types of phenolic acids. The pseudo‐first‐order rate constants of PCP degradation (K 3) increased with those for the photoreduction of Fe(III) (k 1 ).This indicates that the photoreduction of Fe(III) is an important step in the degradation of PCP by the photo‐Fenton reaction. Moreover, the K 3values for gallic, protocatechuic and caffeic acids were larger than those for syringic, vanillic and ferulic acids. This shows that the phenolic acids in HA, which contain neighboring hydroxyl groups, are major contributors to the facilitation of PCP degradation.
TL;DR: In this article, the adsorbed Sb(V) ions were desorbed easily by a 50 mM NaOH solution, and a 41-90 times concentrated SbV solution was yielded correspondingly.
Abstract: Adsorption rates of Sb(V) ions on an activated alumina (AA) were analyzed by batchwise experiments, while the continuous adsorption, desorption, regeneration of AA, and multiple reuse cycles were studied by flow column tests. The adsorption rates increased quickly with the increases of shaking speed and operation temperature. The adsorbed Sb(V) ions were desorbed easily by a 50 mM NaOH solution, and a 41–90 times concentrated Sb(V) solution was yielded correspondingly. AA was effectively regenerated by desorption operation and ca. 93% of the initial adsorption capacity was retained after six times adsorption/desorption cycles.