Main Primary Products Research Articles

Reaction of F Atoms with Carbonyl Sulfide: Experimental and Theoretical Study.

The gas phase reaction of fluorine atoms with carbonyl sulfide, F + OCS → SF + CO (1), has been investigated over a wide temperature range, T = 220-960 K, in a discharge-flow system combined with mass spectrometry for the analysis of the reactive mixture. The reaction rate coefficient was determined as a function of temperature using both absolute (under pseudo-first-order conditions using an excess of F atoms) and relative rate methods: k1 = (8.95 ± 0.52) × 10-11 exp((102 ± 20)/T) cm3 molecule-1 s-1 (with an estimated total uncertainty of 15% independent of temperature). The SF radical was observed as the main primary reaction product. The experimental results are supported by theoretical calculations, which evidence that the reaction is exothermic with a weak negative temperature dependence.

The effect of the isocyanate trimerisation catalyst on the chemical composition and strength characteristics of polyurethane-polyisocyanate foams

Nowadays polyurethane-polyisocyanurate (PIR) foams are in a wide use as structural and thermal insulation materials. Isocyanate trimerisation catalysts for foams synthesis have low selectivity in terms of isocyanurate formation. As a consequence, a significant number of target (primary) and (secondary) chemical processes occur during the synthesis of PIR foams. We estimated the dependence of isocyanate group consumption for the formation of the main primary and secondary products on composition isocyanate index by methods based on the internal standard. Indeed, with an increase in the isocyanate index, the conversion of isocyanate to isocyanurate decreases significantly. The paper examines the influence of trimerisation catalyst type on chemical composition and strength characteristics of PIR foams. Hence, catalysts based on organic salts of alkali metals are more selective to the isocyanate trimerisation process than tertiary amines and derivatives of quaternary ammonium bases.

Biodegradation mechanism of chlorpyrifos by Bacillus sp. H27: Degradation enzymes, products, pathways and whole genome sequencing analysis

Chlorpyrifos (CP) is a pesticide widely used in agricultural production. However, excessive use of CP is risky for human health and the ecological environment. Microbial remediation has become a research hotspot of environmental pollution control. In this study, the effective CP-degrading strain H27 (Bacillus cereus) was screened from farmland soil, and the degradation ratio was more than 80%. Then, the degradation mechanism was discussed in terms of enzymes, pathways, products and genes, and the mechanism was improved in terms of cell motility, secretory transport system and biofilm formation. The key CP-degrading enzymes were mainly intracellular enzymes (IE), and the degradation ratio reached 49.6% within 30 min. The optimal pH for IE was 7.0, and the optimal temperature was 25 °C. Using DFT and HPLC‒MS analysis, it was found that degradation mainly involved oxidation, hydrolysis and other reactions, and 3 degradation pathways and 14 products were identified, among which TCP (3,5,6-trichloro-2-pyridinol) was the main primary degradation product in addition to small molecules such as CO2 and H2O. Finally, the whole genome of strain H27 was sequenced, and the related degrading genes and enzymes were investigated to improve the metabolic pathways. Strain H27 had perfect genes related to flagellar assembly and chemotaxis and tended to tolerate CP. Moreover, it can secrete esterase, phosphatase and other substances, which can form biofilms and degrade CP in the environment. In addition, CP enters the cell under the action of permeases or transporters, and it is metabolized by IE. The degradation mechanism of CP by strain H27 is speculated in this study, which provided a theoretical basis for enriching CP-degrading bacteria resources, improving degradation metabolic pathways and mechanisms, and applying strain H27 to environmental pollution remediation.

Biometric genetics in Cowpea beans (Vigna unguiculata (L.) Walp) II: estimates of genetic gains through selection indices

Low cowpea productivity (Vigna unguiculata (L.) Walp) in the semi-arid region of Paraíba is due, among other factors, to poor-quality cultivars. This research tested biometric models intending to increase productivity of superior cultivars with the following objectives: i. Estimate genetic gains in production components; ii. Identify the selection index model providing the greatest gains through simultaneously selecting a set of variables, and iii. Select cultivars with higher productivity. The experiment was carried out in the experimental field of the Agrifood Science and Technology Center of the Federal University of Campina Grande. Eight cultivars and 13 variables were evaluated. Data were subjected to ANOVA and means were grouped using the Scott and Knott test. Genetic gains were estimated by correlated response, classic selection index, rank sum and index based on desired gains. Direct selection of the secondary pod yield component provides significant genetic gains in main grain yield. Among the methodologies used, the classic selection index provided greater distribution of genetic gains for main grain yield and primary production components. These results allow concluding that Costela de vaca, BRS Marataoã and Paulistinha cultivars should be selected for cultivation and commercial exploitation in the semiarid region of Paraíba. Highlights: Direct selection of the secondary pod yield component provides significant genetic gains in main grain yield. The classic selection index provided greater distribution of genetic gains for main grain yield and primary production components. Cultivars were selected for cultivation and commercial exploitation in the semi-arid region of Paraíba.

Diversity and seasonal development of large zooplankton along physical gradients in the Arctic Barents Sea

Due to ongoing climate change, a new Arctic Ocean ecosystem is emerging. Within the framework of the Nansen Legacy project, we investigated the community composition of the large zooplankton and its seasonal development along a latitudinal gradient in the northern Barents Sea. Total biomass was maximal in summer and early winter, and minimal in spring, with copepods contributing considerably in all seasons. Euphausiids represented a minor fraction of the biomass, whereas chaetognaths and other gelatinous zooplankton contributed substantially to the sampled zooplankton at all stations, particularly in winter. Amphipod biomass was high in early winter, but otherwise low. Temperature in the water column interior and bottom-depth had the highest explanatory power for the community composition of the large zooplankton, both revealing the same distinct Atlantic and Arctic domains along the studied section. The continental shelf of the northern Barents Sea had an Arctic signature and was in terms of biomass characterized by a dominance of cold-water species, such as Themisto libellula, and Calanus glacialis. The copepod Calanus hyperboreus was the dominant over the continental slope. Locations at the southern and northern end of the studied section were influenced by Atlantic Water (at intermediate depth at the northern stations), and contained a mixture of temperate species, deep-water species, and sympagic amphipods in northern ice-covered waters. In the northern Barents Sea, a seasonal change was observed in the biomass fractions of different zooplankton feeding guilds, with dominance of herbivores in summer and carnivores in winter. This suggests switching between bottom-up and top-down control through the year. On the continental slope, species that are typically considered omnivores seemed to increase in importance. The role of seasonally changing food preferences to bridge periods outside of the main primary production season is discussed in light of ecosystem resilience to the expected changes in the Arctic Ocean.

Development of Science E-Modules for Middle Schools Integrated with Al-Qur’an Verses with Virtual Simulation of Solar System Material

This research was conducted to produce a science e-modules for middle schools integrated with the Al-Qur’an versed, assisted by virtual simulations on solar system material. These teaching materials were made to support students learning independently with engaging content in which they were equipped with virtual simulations. The author conducted the research using research and development methods by adapting Borg and Gall’s research design. The step in this research was limited by the fifth step, namely the main primary product revision. This was due to the authors’ conditions in the development process. The results of the validity of the science e-module product have been declared valid based on the results of validation by Al-Qur’an verses integration experts, learning materials experts, and teaching materials experts, with the category of all assessments being very good or feasible to use. In addition, the science e-module for middle school integrated verses of the Al-Qur’an assisted virtual simulation on the stated practical to use for students in learning. The student responses related to the science e-module product for middle school integrated verses Al-Qur’an assisted virtual simulation on very positive.

Engineering oxygen vacancy in (001)-dominated TiO2 for enhanced CH4 photocatalytic conversion

Photooxidation of methane to high valued C1 liquid products with both high yield and selectivity against overoxidation has been a huge challenge. In this work, (001)-dominated ultra-thin TiO2 nanosheets with plenty of oxygen vacancies (Ov) were mass produced by simple hydrothermal and annealing treatments, and used for photocatalytic oxidation of CH4 into C1 products (mainly HCHO, CH3OOH and HCOOH) with H2O2 as the necessary oxidant. For the optimal catalyst with the largest Ov ratio, the highest C1 products yield of 5.95 mmol g−1h−1 was achieved within 2 h, accompanied by a high C1 selectivity of 99.03%, comparable to the current yield record over precious-metal based binary/ternary catalyst. In-situ electron spin resonance, in-situ Fourier Transform Infrared Spectroscopy and mass spectra combined with density functional theory calculations were used for comprehensive clarification of the underlying reaction mechanism. Ov on TiO2-(001) face largely lowered the energy required for CH bond cleavage of CH4, which was the rate-determinate reaction during CH4 photooxidation. Then formed *CH3 went through distinct reaction routes of Ti-OOH+Ti-CH3→Ti–OCH3+Ti-OH→HCHO, thus achieving high yield and selectivity for the main primary product of HCHO (65.7%).

Increased Markers of Oxidative Stress and Positive Correlation Low-Grade Inflammation with Positive Symptoms in the First Episode of Schizophrenia in Drug-Naïve Patients.

Schizophrenia is a severe and chronic mental illness usually diagnosed in adolescents and young adults. Many studies indicate that oxidative stress causes membrane dysfunction and cell damage, which is implicated in the pathophysiology of schizophrenia. The purpose of our study was to evaluate oxidative stress markers (the main primary products of lipid peroxidation, lipid hydroperoxides (LOOH), and end products of lipid peroxidation, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), and Ferric Reducing Ability of Plasma (FRAP)) in the plasma of patients with the first episode of schizophrenia in drug-naïve patients (22 men and 12 women aged 17–29). The control group (Ctrl) comprised 26 healthy subjects (19 men and 7 women, aged 18–30 years). The Positive and Negative Syndrome Scale (PANSS) was applied to evaluate psychotic symptoms. Analyses of the oxidative stress variables revealed an increased level of SOD (U/mL) in subjects with schizophrenia versus control group. In addition, lipid damage measured as LOOHs µ (mol/L) and MDA was significantly higher in patients with schizophrenia in comparison to control subjects. There was a positive correlation between MDA µmol/L and PANSS P and a positive correlation between C-reactive protein (CRP) and the PANSS P scale. The elevated level of superoxide dismutase in patients with the first episode of schizophrenia can be explained by compensatory mechanisms to counteract oxidative stress. Malondialdehyde can be used as a simple biomarker of low-grade systemic inflammation associated with oxidative stress. A positive correlation between CRP and PANSS P scale and MDA and PANSS P scale may indicate a significant relationship between the development of low-grade inflammation and damage associated with oxidative stress in the development of the first symptoms of schizophrenia.

Comparative study of benthic diatom community using 18S rDNA metabarcoding and light microscopy in the Bosphorus, Turkey

Diatoms are one of the major algal groups having an important role in the aquatic systems in which they constitute the main primary production with dinoflagellates in the coastal regions, and can contribute to photosynthesis at great rates. There had been intense effort to reveal diatom community with light microscopy (LM) and scanning electron microscopy (SEM), on the other hand, DNA barcoding techniques had been an interest to understand the microbiome in the last decades. Barcoding provided rapid response on the targeted organisms and introduced many new species. Recently, monocultural molecular studies showed that species could be described with accurate and reliable results. DNA metabarcoding approaches yielded to determine the whole organisms with available DNA data in the sample and major advances on next-generation sequencing platforms enable to widen the application of metabarcoding approach to various environmental samples. The aim of this study was to perform a comparative assessment of the diatom community structures in Bosphorus of Istanbul, Turkey by LM and 18S rDNA metabarcoding. Diatom samples were collected by brushing from the submerged stones of 10 cm2 of area taken from the coast of Beykoz on the Asian part of the Bosphorus, Istanbul and processed for LM and metabarcoding in June 2020. To concentrate the sample, the scrapes of the biofilm filtered from a 0.22-micron filter, and eDNA was extracted from that filter paper using MN NucleoSpin Soil DNA isolation kit (Macherey-Nagel, Germany) following the manufacturer’s protocol and diatom community profile was analyzed by targeting the V4 region of the 18S rRNA gene using Illumina® MiSeq™. DNA metabarcoding results revealed two classes Bacillariophyceae (91%) and Mediophyceae (9%) (Fig. 1). While small-celled Hyalosira delicatula Kützing was the most abundant taxa with 40% abundance and it was followed by Licmophora spp. (33%). 28% of Licmophora sequences could not be assigned to any species and remained as unidentified, Licmophora gracilis (Ehrenberg) Grunow (4%), and L. flabellata (0.9%) detected at lower abundances. Besides, one of the common genera of diatoms, Navicula spp., showed a relative abundance of 4% and another common genus Nitzschia spp. were represented only by N. commutata Grunow and composed 0.5% of the community. While 18S rDNA metabarcoding revealed 11 genera, LM investigation identified 17 genera belonging to 21 species. 4 genera were common in both techniques and Licmophora flabellata was detected in both LM and metabarcoding methods. Interestingly, small celled taxa which could be easily overlooked in LM was detected with 18S metabarcoding. The results presented a promising number of genera which could be detected by both methods (Fig. 2). DNA metabarcoding of diatoms is a new area of research in the coastal waters and there are few studies performed so far and this is the first study relying on the rDNA metabarcoding of diatoms in the aquatic systems in Turkey. The comparison of the taxa using microscopy methods and metabarcoding techniques indicated some significant differences in the diatom composition. However, the results here with 18 species with metabarcoding vice-versa 21 taxa with microscopy methods confirms poor biodiversity in the Bosphorus. However, this study based on one sampling effort in one station for the comparison of the two methods, we had LM results from more stations in different seasons supporting the lower biodiversity. eDNA data is scarce from the coastal areas and our results comprise a promising number of genera. Results of this study could provide data for further research, which high number of diatoms could be determined with eDNA metabarcoding.

The monitoring of the phytoplankton condition in the Luga Bay of the Gulf of Finland under natural and anthropogenic impacts

The technogenic transformation of the ecosystem of the southeast part of Luga Bay water area (the second bay of the Baltic Sea) where Ust-Luga commercial seaport situated was determined by longstanding dredging, dumping and other types of anthropogenic impact. The development of phytoplankton as the main primary production former and the base of food reserve for aquatic biological resources was investigated during the monitoring of aquatic biological resources of the Luga Bay which was held due to the seaport construction. The investigation of phytoplankton content and development took part in the main seasons of the ice-free period of 2005–2018 in the water areas of dredging, damping, and adjacent areas. The maximum values of the phytoplankton abundance and biomass were detected in spring. The main part of biomass was formed by diatoms and dinoflagellates. The summer biomass mainly was lower than in spring and the proportion of cyanoprokaryotes (in some years also cryptophytes and green) increased. In autumn the biomass decreasing was continued, cyanoprokaryotes and cryptomonads dominated. The quantitative indicators of phytoplankton development were varied from year to year in all seasons of 2005–2018 but they kept in frames of values which previously observed for the water area of the Luga Bay. The influence of the Gulf of Finland water warming on phytoplankton development was not traced. The certain differences between the quantitative development and composition of the dominant phytoplankton complex on the water areas of dredging, damping, and adjacent areas weren’t observed. The average phytoplankton biomass for the ice-free period in the most part of years corresponds to the mesotrophic state of the Luga Bay water area. There was not a significant impact of dredging and dumping on the phytoplankton of the Luga Bay which indicates the stable state of its ecosystem primary producer and the preservation of the productional resource of the fish food base.

Synchrotron Photoionization Study of the Diisopropyl Ether Oxidation.

Scientific evidence has shown oxygenates help to reduce dangerous pollutants arising from burning fossil fuel in the automotive sector. For this reason, their use as additives has spread widely. The aim of this work consists in providing a comprehensive identification of the main primary oxidation products of diisopropyl ether (DIPE), one of the most promising among etheric oxygenates. The Cl-initiated oxidation of DIPE is examinated by using a vacuum ultraviolet (VUV) synchrotron radiation at the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory (LBNL). Products are identified on the basis of their mass-to-charge ratio, shape of photoionization spectra, adiabatic ionization energies, and chemical kinetic profiles, at three different temperatures (298, 550, and 650 K). Acetone, propanal, propene, and isopropyl acetate have been identified as major reaction products. Acetone is the main primary product. Theoretical calculations using the composite CBS-QB3 method provided useful tools to validate the postulated reaction mechanisms leading to experimentally observed species. The formation of other species is also discussed.

Thermal treatment of lignin, cellulose and hemicellulose in nitrogen and carbon dioxide

The paper explores the primary products from fast pyrolysis of biomass components: Lignin, Cellulose and Hemicellulose (Xylan). A heated strip reactor is employed at temperatures of 1573 K and 2073 K with N2 and CO2 atmospheres. Volatiles quench immediately after volatilization on a cold pyrex bridge, while char remains on the heated strip for 3 s. Tar, soot and char are collected and subject to chemical treatments and analyses, including gas chromatography-mass spectrometry and Size Exclusion Chromatography, Thermogravimetric analysis, Raman spectroscopy and Scanning Electron Microscopy.Fast pyrolysis of Lignin produces “Light tar” (soluble in acetone) and “Heavy tar” (soluble in NMP), char, a minor fraction of soot. The “Light tar” contains Vanillin, which can be considered the main primary depolymerization product, but also aliphatics and PAHs. Higher temperature enhances “Heavy tar” and graphitization of the char.Cellulose at 1573 K produces only “Light tar”, largely made of Levoglucosan, as the result of depolymerization. At higher temperature the tar becomes heavier. Hemicellulose has a peculiar behavior: it produces a “Light tar” which is chemically similar to that of Cellulose and, at high temperature also “Heavy tar”. Hemicellulose pyrolysis results also in the production of an atypical solid residue: swollen ad spongy at lower temperature, bright and glassy at higher temperature.CO2 affects the pyrolysis products, particularly those of Lignin, promoting tar cracking and oxygenation already at the stage of primary pyrolysis and hindering thermal annealing and structural ordering of the solid carbonaceous structure.

Method development of levoglucosenone analysis by UHPLC-UV-MS in fast pyrolysis samples and aspects of its degradation in aqueous samples.

Levoglucosenone ((1S,5R)-6,8-dioxabicyclo[3.2.1]oct-2-en-4-one or LGO; CAS number: 37112-31-5) is an extensively studied biomass based chemical and its potential applications in organic synthesis, as well as in the extraction of various natural substances, have been established; therefore developing dependable, yet fast and simple analytical methods for determining LGO in the products of thermochemical biomass processing is of great importance. In this work different UHPLC methods have been developed and compared for the determination of LGO in wood pyrolysis products. In addition to UV detection, LGO determination conditions by single quadrupole mass spectrometry have been adjusted with and without chemical derivatization. The ionization of LGO in the positive and negative electrospray ionisation mode and the effect of a mobile phase additive on LGO and its degradation product ionisation have been evaluated. Using the UHPLC-UV system, a method for the quantification of levoglucosenone was developed and the analytical parameters of the method were determined. Utilising the developed UHPLC-UV method, studies of LGO stability in standard solution and in fast pyrolysis products were carried out in various solvent systems at different temperatures and pH levels. The main LGO primary degradation product has been confirmed to be furfural. It has been concluded that the degradation rate of LGO is significantly affected by the solvent and storage temperature, so it is essential that LGO standard solutions and samples are analysed when freshly prepared. Using a UHPLC-MS system and derivatization with 2,4-dinitrophenylhydrazine (DNPH), a method for the determination of LGO was developed and the method analytical parameters were tested. To sum up, quantitative determination of LGO in pyrolysis products can be performed by reversed phase UHPLC-UV without any particular sample preparation, but in the case of UHPLC-MS it is necessary to derivatize LGO with DNPH to ensure ionisation of LGO. The additional work, requiring MS detection, can be outweighed by the greater selectivity compared to that of the more straightforward UV detection method in cases of incomplete chromatographic separation.

Review of the Results from the NUCLEON Space Experiment

The NUCLEON space observatory was developed to measure the spectra of cosmic ray nuclei with individual charge resolution in the energy range of several TeV to 1 PeV per particle. The NUCLEON was launched into a heliosynchronous orbit as an additional load on the Resurs-2P production satellite on December 28, 2014, and it is still in operation (2019). This work is a brief review of the results from the NUCLEON observatory over three years of operation in orbit. The spectra of the main primary abundant nuclei and product nuclei of cosmic rays (CRs) are presented. Some new interesting features of the CR spectra found in the NUCLEON data are discussed.

Cu42Ge24Na4—A Giant Trimetallic Sesquioxane Cage: Synthesis, Structure, and Catalytic Activity

Unprecedented germanium-based sesquioxane exhibits an extremely high nuclearity (Cu42Ge24Na4) and unusual encapsulation features. The compound demonstrated a high catalytic activity in the oxidative amidation of alcohols, with cost-effective catalyst loading down to 400 ppm of copper, and in the oxidation of cyclohexane and other alkanes with H2O2 in acetonitrile in the presence of nitric acid. Selectivity parameters and the mode of dependence of initial cyclohexane oxidation rate on initial concentration of the hydrocarbon indicate that the reaction occurs with the participation of hydroxyl radicals and alkyl hydroperoxides are formed as the main primary product. Alcohols have been transformed into the corresponding ketones by the catalytic oxidation with tert-butyl hydroperoxide.

Selenium supplementation of diets of dairy cows to produce Se-enriched cheese

Selenium (Se) deficiency in people and animals is a nutritional problem in many regions of the world. Ten mid-lactation Estonian Red dairy cows were supplemented for 64 days with inorganic Se [0.39 mg kg−1 in total mixed ration (TMR)] followed by a 57-day period of supplementation with organic and inorganic Se (0.44 mg kg−1 in TMR), according to EU directives on maximum allowed amounts. Feeding organic Se increased Se content in blood (from 186.5 to 287.9 μg kg−1), milk (from 17.1 to 51.8 μg kg−1) and Edam-type cheese made there from (from 146 to 361 μg kg−1). Se content in milk after supplementation was high enough to produce a cheese enabling the nutrition claim “high in Se” and related health claims. The concentration of the main primary oxidation products of linoleic acid (oxylipins) was low and leukotoxin diols were found in trace amounts; the oxidative stability of cheeses was high.

Kinetics of the photolysis and OH reaction of 4-hydroxy-4-methyl-2-pentanone: Atmospheric implications

This study provides the first kinetic and mechanistic study of the photolysis of 4-hydroxy-4-methyl-2-pentanone (4H4M2P) and the determination of the temperature dependence of the relative rate coefficient for the reaction of OH radicals with 4H4M2P. The UV absorption spectrum of 4H4M2P was determined in the spectral range 200–360 nm. The photolysis frequency of this compound in the atmosphere was evaluated relative to actinometers and found to be J4H4M2Patm=4.2×10−3h−1, corresponding to a lifetime of about 10 days. Using 4H4M2P cross section measurements, an atmospheric effective quantum yield of 0.15 was calculated. The main primary photolysis products were acetone (121 ± 4) % and formaldehyde (20 ± 1) %. A low methanol yield of (3.0 ± 0.3) % was also determined. These results enabled us to propose a mechanistic scheme for the photolysis. Rate coefficients for the reaction of 4H4M2P with OH radicals were determined over the temperature range 298–354 K and the following Arrhenius expression was obtained: kOH+4M4H2P = (1.12 ± 0.40) × 10−12exp(461.5 ± 60/T) cm3 molecule−1 s−1. The lifetimes of 4H4M2P due to reaction with OH radicals has been estimated to ∼2.5 days and indicates that the gas-phase reaction with the OH could be the main loss process for this compound.

Environmental Fate of Chiral Herbicide Fenoxaprop-ethyl in Water-Sediment Microcosms.

The environmental fate of the herbicide fenoxaprop-ethyl (FE) in water, sediment and water-sediment microcosm was studied and degradation products fenoxaprop (FA), ethyl-2-(4-hydroxyphenoxy)propanoate (EHPP), 2-(4-hydroxyphenoxy)propanoic acid (HPPA) and 6-chloro-2,3-dihydrobenzoxazol-2-one (CDHB) were monitored. FE, FA, EHPP and HPPA were chiral and the environmental behavior was investigated on an enantiomeric level. In water, sediment and water-sediment microcosms, fenoxaprop-ethyl degraded very fast with half-lives less than 1 day and it was found the herbicidally inactive S-enantiomer degraded faster. Fenoxaprop was the main primary degradation product which was quickly formed and the further degradation was relatively slow with half-lives of 6.4–12.4 days, and the S-enantiomer degraded faster too. EHPP, HPPA and CDHB could be found and S-EHPP and S-HPPA were degraded preferentially. The effects of microorganism and water content were investigated and it was found that the enantioselectivity was attributed to microorganisms. In sediment, the main degradation pathway of fenoxaprop-ethyl was hydrolysis and the degradation rate of fenoxaprop-ethyl increased with water content. The degradation products and enantioselectivity should be considered for the impact of fenoxaprop-ethyl on the aquatic system.

Mechanism for the primary transformation of acetaminophen in a soil/water system

The transformation of acetaminophen (APAP) in a soil/water system was systematically investigated by a combination of kinetic studies and a quantitative analysis of the reaction intermediates. Biotransformation was the predominant pathway for the elimination of APAP, whereas hydrolysis or other chemical transformation, and adsorption processes made almost no contribution to the transformation under a dark incubation. Bacillus aryabhattai strain 1-Sj-5-2-5-M, Klebsiella pneumoniae strain S001, and Bacillus subtilis strain HJ5 were the main bacteria identified in the biotransformation of APAP. The soil-to-water ratio and soil preincubation were able to alter the transformation kinetic pattern. Light irradiation promoted the overall transformation kinetics through enhanced biotransformation and extra photosensitized chemical reactions. The transformation pathways were strongly dependent on the initial concentration of APAP. The main primary transformation products were APAP oligomers and p-aminophenol, with the initial addition of 26.5 and 530 μM APAP, respectively. APAP oligomers accounted for more than 95% of transformed APAP, indicating that almost no bound residues were generated through the transformation of APAP in the soil/water system. The potential environmental risks of APAP could increase following the transformation of APAP in the soil/water system because of the higher toxicity of the transformation intermediates.

Photodegradation of 4-tert-butylphenol in aqueous solution by UV-C, UV/H2O2 and UV/S2O82− system

ABSTRACTThe photolytic degradation of 4-tert-butylphenol (4-t-BP) in aqueous solution was investigated using three kinds of systems: UV-C directly photodegradation system, UV/H2O2 and UV/S2O82− system. Under experimental conditions, the degradation rate of 4-t-BP was in the order: UV/S2O82− > UV/H2O2 > UV-C. The reaction kinetics of UV/S2O82− system were thoroughly investigated. The increase of S2O82− concentration enhanced the 4-t-BP degradation rate, which was inhibited when the concentration of S2O82− exceeded 4.0 mM. The highest efficacy in 4-t-BP degradation was obtained at pH 6.5. The oxidation rate of 4-t-BP could be accelerated by increasing the reaction temperature and irradiation intensity. The highest rate constant (kobs = 8.4 × 10−2 min−1) was acquired when the reaction temperature was 45°C. The irradiation intensity was measured by irradiation distance, and the optimum irradiation distance was 10 cm. Moreover, the preliminary mechanism of 4-t-BP degradation was studied. The bond scission of the 4-t-BP molecule occurred by the oxidation of SO4•−, which dimerized and formed two main primary products. Under the conditions of room temperature (25°C±1°C) and low concentration of K2S2O8 (0.5 mM), 35.4% of total organic carbon (TOC) was removed after 8.5-h irradiation. The results showed that UV/S2O82− system was effective for the degradation of 4-t-BP.