Synthesis of branched para-nonylphenol isomers: occurrence and quantification in two commercial mixtures

Eight tertiary nonanols were synthesized via Grignard reaction and coupled by Friedel–Crafts alkylation with phenol to the corresponding nonylphenols. Six branched para-nonylphenols (NP) were obtained: 4-(3′-methyl-3′-octyl)phenol (33NP), 4-(2′-methyl-2′-octyl)phenol (22NP), 4-(2′,5′-dimethyl-2′-heptyl)phenol (252NP), 4-(2′,5′,5′-trimethyl-2′-hexyl)phenol (2552NP), 4-(2′,4′-dimethyl-2′-heptyl)phenol (242NP) and 4-(4′-ethyl-2′-methyl-2′-hexyl)phenol (4E22NP). Their structures were confirmed by GC–MS and NMR spectroscopy. These six isomers as well as the earlier synthesized 4-(3′,5′-dimethyl-3′-heptyl)phenol (353NP), 4-(3′,6′-dimethyl-3′-heptyl)phenol (363NP) and 4-(2′,6′-dimethyl-2′-heptyl)phenol (262NP) were compared with commercial NP mixtures purchased from Acros and Fluka by GC–MS (equipped with a 100 m polysiloxane column). The analyses revealed that all obtained isomers are occurring in different quantities in both commercial NP mixtures.     

Separation, synthesis and estrogenic activity of 4-nonylphenols: two sets of new diastereomeric isomers in a commercial mixture

Two sets of new diastereomeric 4-nonylphenol (NP) isomers [4-(3,4-dimethylheptan-4-yl)phenol (344NP, NP-J, L) and 4-(3,4-dimethylheptan-3-yl)phenol (343NP, NP-K, P)] were separated from a commercial NP mixture. The mixture of these diastereomers was synthesized at the same time by a single Friedel-Crafts reaction of 3,4-dimethyl-4-heptanol and phenol, and the mixture was separated into individual NPs by HPLC equipped with Hypercarb column. For the first time, in this study the stereostructure-estrogenic activity relationship of NP diastereomers was investigated. The NP isomers (NP-L and NP-P) having the beta-methyl group over the benzene ring were found to be 2-4 times more estrogenic than their diastereomers (NP-J and NP-K). In the case of the other set of diastereomer [4-(3,5-dimethylheptan-3-yl)phenol, (353NP, NP-E, G)] containing gamma-methyl group in the molecule, the gamma-methyl proton signal (delta 0.49) in the more estrogenic isomer (NP-G) also appeared in a higher field than the corresponding methyl signal (delta 0.76) of the less estrogenic isomer (NP-E).     

Determination and distribution characteristics of degradation products of nonylphenol polyethoxylates in the rivers of Taiwan

Concentrations of degradation products of nonylphenol polyethoxylates (NPEOs) were analyzed in river water samples in order to determine the distribution characteristic of these alkylphenolic compounds in 18 major rivers of Taiwan. The degradation products of NPEOs were detected in all river samples, with the dicarboxylates alkylphenolic degradation products (CAPEC) being detected most frequently and at the highest concentrations. Concentrations of NP and NP1EO in rivers ranged from n.d. to 5.1 μg l⁻¹ and n.d. to 0.5 μg l⁻¹, respectively. The total concentrations of shortened carboxylates (i.e., NP1EC + NP2EC + NP3EC) and dicarboxylates alkylphenolic degradation products (CAP1EC + CAP2EC) ranged from n.d. to 63.6 μg l⁻¹ and n.d. to 94.6 μg l⁻¹, respectively. Concentrations of NP2EC, NP3EC and all CAPEC residues were determined semi-quantitatively by comparing with the internal standard. Significantly higher concentrations of CAPEC residues were detected in the river waters as compared to those of NP, NP1EO and NPEC degradation products and the average proportions of these compounds in the samples of the rivers were as follows: NP + NP1EO was 5 ± 2.5%, total NPEC was 25 ± 12%, and total CAPEC was 70 ± 12%. The high concentration ratios of CAPEC/NPEC illustrate that aerobic biodegradation plays a main route in the fate of NPEO in the rivers of Taiwan.     

Variation in estrogenic activity among fractions of a commercial nonylphenol by high performance liquid chromatography

Estrogenic activity by recombinant yeast screen assay of the commercial NP was considerably higher when compared with that of n-nonylphenol (n-NP). Fractionation of the commercial NP by high performance liquid chromatography (HPLC) afforded seven isomers: 4-(1,3-dimethyl-1-propyl-butyl)-phenol, 4-(1,1,3-trimethyl-hexyl)-phenol, 4-(1,1-dimethyl-3-ethyl-pentyl)-phenol, 4-(1,1,4-trimethyl-hexyl)-phenol, 4-(1-methyl-1-propyl-pentyl)-phenol, 4-(1,1,2-trimethyl-hexyl)-phenol and 4-(1-ethyl-1-methyl-hexyl)-phenol. The structures of these isomers were determined by GC-MS and nuclear magnetic resonance spectroscopy (NMR). All of these isomers possessed tertiary alpha-carbon in their chemical structures. Another tertiary NP, 4-(1,1-dimethyl-heptyl)-phenol was synthesized in the present study and this synthetic NP also exhibited the estrogenic activity. One fractionated compound was identified as one of decylphenol, 4-(1-ethyl-1,4,4-trimethyl-pentyl)-phenol. The isomer, 4-(1,1,4-trimethyl-hexyl)-phenol exhibited the highest estrogenic activity corresponding to 1/10000 that of 17beta-estradiol (E2). The activity of n-NP was the least. This suggests that it may be possible to develop a technical NP mixture with relatively low estrogenic activity.     

Distribution, fate and formation of non-extractable residues of a nonylphenol isomer in soil with special emphasis on soil derived organo-clay complexes

Anthropogenic contaminants like nonylphenols (NP) are added to soil, for instance if sewage-sludge is used as fertilizer in agriculture. A commercial mixture of NP consists of more than 20 isomers. For our study, we used one of the predominate isomers of NP mixtures, 4-(3,5-dimethylhept-3-yl)phenol, as a representative compound. The aim was to investigate the fate and distribution of the isomer within soil and soil derived organo-clay complexes. Therefore, (14)C- and (13)C-labeled NP was added to soil samples and incubated up to 180 days. Mineralization was measured and soil samples were fractionated into sand, silt and clay; the clay fraction was further separated in humic acids, fulvic acids and humin. The organo-clay complexes pre-incubated for 90 or 180 days were re-incubated with fresh soil for 180 days, to study the potential of re-mobilization of incorporated residues. The predominate incorporation sites of the nonylphenol isomer in soil were the organo-clay complexes. After 180 days of incubation, 22 % of the applied (14)C was mineralized. The bioavailable, water extractable portion was low (9 % of applied (14)C) and remained constant during the entire incubation period, which could be explained by an incorporation/release equilibrium. Separation of organo-clay complexes, after extraction with solvents to release weakly incorporated, bioaccessible portions, showed that non-extractable residues (NER) were preferentially located in the humic acid fraction, which was regarded as an effect of the chemical composition of this fraction. Generally, 27 % of applied (14)C was incorporated into organo-clay complexes as NER, whereas 9 % of applied (14)C was bioaccessible after 180 days of incubation. The re-mobilization experiments showed on the one hand, a decrease of the bioavailability of the nonylphenol residues due to stronger incorporation, when the pre-incubation period was increased from 90 to 180 days. On the other hand, a shift of these residues from the clay fraction to other soil fractions was observed, implying a dynamic behavior of incorporated residues, which may result in bioaccessibility of the NER of nonylphenol.     

Distribution,fate and formation of non-extractable residues of a nonylphenol isomer in soil with special emphasis on soil derived organo-clay complexes

Anthropogenic contaminants like nonylphenols (NP) are added to soil, for instance if sewage-sludge is used as fertilizer in agriculture. A commercial mixture of NP consists of more than 20 isomers. For our study, we used one of the predominate isomers of NP mixtures, 4-(3,5-dimethylhept-3-yl)phenol, as a representative compound. The aim was to investigate the fate and distribution of the isomer within soil and soil derived organo-clay complexes. Therefore, ¹⁴C- and ¹³C-labeled NP was added to soil samples and incubated up to 180 days. Mineralization was measured and soil samples were fractionated into sand, silt and clay; the clay fraction was further separated in humic acids, fulvic acids and humin. The organo-clay complexes pre-incubated for 90 or 180 days were re-incubated with fresh soil for 180 days, to study the potential of re-mobilization of incorporated residues. The predominate incorporation sites of the nonylphenol isomer in soil were the organo-clay complexes. After 180 days of incubation, 22 % of the applied ¹⁴C was mineralized. The bioavailable, water extractable portion was low (9 % of applied ¹⁴C) and remained constant during the entire incubation period, which could be explained by an incorporation/release equilibrium. Separation of organo-clay complexes, after extraction with solvents to release weakly incorporated, bioaccessible portions, showed that non-extractable residues (NER) were preferentially located in the humic acid fraction, which was regarded as an effect of the chemical composition of this fraction. Generally, 27 % of applied ¹⁴C was incorporated into organo-clay complexes as NER, whereas 9 % of applied ¹⁴C was bioaccessible after 180 days of incubation. The re-mobilization experiments showed on the one hand, a decrease of the bioavailability of the nonylphenol residues due to stronger incorporation, when the pre-incubation period was increased from 90 to 180 days. On the other hand, a shift of these residues from the clay fraction to other soil fractions was observed, implying a dynamic behavior of incorporated residues, which may result in bioaccessibility of the NER of nonylphenol.     

Cold season CH4, CO2 and N2O fluxes from freshwater marshes in northeast China

Cold season (winter and thaw) CH₄, CO₂ and N₂O fluxes from freshwater marshes (47°35′N, 133°31′E, Northeast China) were measured, using the static chamber method. The mean CH₄ and CO₂ fluxes from Carex lasiocarpa (Cl) were 0.5 ± 0.19 and 6.23 ± 1.36 mg C m⁻² h⁻¹, respectively, and those from Deyeuxia angustifoli (Da) were 0.18 ± 0.15 and 5.22 ± 2.48 mg C m⁻² h⁻¹, respectively in winter. There was no significant difference between Cl and Da (p > 0.05). The contributions of winter CH₄ fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N₂O sink in winter season in northeast China. During thaw, the CH₄ and CO₂ emissions rapidly increased, 4.5–6 times of winter emissions. Wetland became a source of N₂O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange.     

Octyl and nonylphenol ethoxylates and carboxylates in wastewater and sediments by liquid chromatography/tandem mass spectrometry

This work presents an LC–MS–MS-based method for the quantitation of nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) in water, sediment, and suspended particulate matter, and three of their carboxylated derivatives in water. The alkylphenol ethoxylates (APEOs) were analyzed using isotope dilution mass spectrometry with [¹³C₆]-labeled analogues, whereas the carboxylated derivatives were determined by external standard quantitation followed by confirmation using standard additions. The method was used to study APEO’s behavior in a wastewater treatment plant (WWTP), where total dissolved NP0-16EO concentration was reduced by approximately 99% from influent (390 μg l⁻¹) to final effluent (4 μg l⁻¹), and total OP0-5EO concentration decreased by 94% from 3.1 to 0.2 μg l⁻¹. In contrast, the carboxylated derivatives were formed during the process with NP0-1EC concentrations increasing from 1.4 to 24 μg l⁻¹. Short-chain APEOs were present in higher proportions in particulate matter, presumably due to greater affinity for solids compared to the long-chain homologues. NP (0.49 μg l⁻¹) and NP0-1EC (4.8 μg l⁻¹) were the only APEO-related compounds detected in a surface water sample from a WWTP-impacted estuary; implying that 90% of the mass was in the form of carboxylated derivatives. Sediment analysis showed nonylphenol to be the single most abundant compound in sediments from the Baltimore Harbor area, where differences in homologue distribution suggested the presence of treated effluent in some of the sites and non-treated sources in the rest.     

Experimental study on the thermal oxidation of 2-chlorophenol in air over the temperature range 450-900 degrees C

The thermal oxidation of 2-chlorophenol (2-CP) in air was investigated using a perfectly stirred reactor at 1 atm over the temperature range 450–900 °C. The relative concentration of 2-CP was 1000 ppmV (equivalence ratio Φ = 0.03). About fifty organic products were identified as trace species. The concentration profiles of 2-CP, carbon oxides as well as those of seventeen major organic intermediates and six non-to-lower chlorinated dioxins and furans were presented as a function of temperature for a residence time of 2 s. The most abundant intermediate products were carbon monoxide, 2 H-pyran-2-one, chlorobenzene, 4-cyclopenten-1,3-dione, phenol, benzofuran, 2-chlorohydroquinone and 2-indanone. These concentration profiles have revealed that temperatures of at least 900 °C were needed to completely oxidize 2-CP, CO and all other organic byproducts to carbon dioxide. Reaction pathways accounting for the formation of most observed products are proposed.     

Determination of dithiocarbamate fungicide propineb and its main metabolite propylenethiourea in airborne samples

A simple, rapid and sensitive GC–MS method for the determination of dithiocarbamate fungicide propineb [polymeric zinc propylenebis (dithiocarbamate)] and an improved HPLC procedure for the simultaneous determination of its main metabolite, propylenethiourea, and ethylenethiourea, the main metabolite of all ethylenedithiocarbamates, in airborne samples are described. The method for the analysis of propineb involves the evolution of carbon disulfide (CS₂), under acidic conditions in the presence of stannous chloride, extraction of the generated CS₂ into a layer of isooctane which is then analyzed for CS₂ content by GC–MS in SIM mode. Under the optimum conditions, the retention time of CS₂ was 1.89 min and the total time of chromatographic analysis was 5 min. Recoveries from spiking glass microfibre filters (GF/A) and silica gel filters were 86 ± 7 (n = 9) and 89 ± 4 (n = 9), respectively. The limit of detection is 0.7 ng per filter, which is equivalent to about 0.8–1.0 ng m⁻³ in air. In parallel, an HPLC method with ultraviolet detection is presented for the simultaneous analysis of the metabolites. Separation of the two metabolites was attained in less than 5 min. Recoveries from spiking GF/A and silica gel filters for ethylenethiourea were 100 ± 1 (n = 3) and 98 ± 2 (n = 3), respectively, while for propylenethiourea were 102 ± 1 (n = 3) and 98 ± 1 (n = 3), respectively. The detection limits are about 36–43 and 40–49 ng m⁻³ in air for ethylenethiourea and propylenethiourea, respectively. All the analytes spiked in the filters are proven to be stable for more than one month, at −4 °C.     

Nitration and hydroxylation of benzene in the presence of nitrite/nitrous acid in aqueous solution

This paper studies the nitration and hydroxylation of benzene in the presence of nitrite/nitrous acid in aqueous solution, both in the dark upon addition of hydrogen peroxide and under 360 nm irradiation. In both cases the detected transformation intermediates were phenol (P), nitrobenzene (NB), 2-nitrophenol (2NP) and 4-nitrophenol (4NP). P and NB directly form from benzene, and the initial formation rate of P is at least an order of magnitude higher than that of NB. In our experiments nitrophenols arise from P nitration, as can be inferred by their time evolution and isomer ratio (2NP:4NP=60:40, 3NP below detection limit). Nitrophenols may also form upon hydroxylation of NB, but in a different ratio (2NP:3NP:4NP=45:30:25). The detection of 3NP is thus a marker for the hydroxylation of NB, since this isomer is not formed in P nitration processes. The formation rates of P and NB increase with decreasing pH, both in the presence of HNO₂ + H₂O₂ in the dark (which produce HOONO) and in the presence of NO₂⁻/HNO₂ under irradiation. In the former case the pH dependence reflects the formation rate of HOONO. In the case of the irradiation experiments the pH effect can be accounted for by the higher molar absorbivity and photolysis quantum yield of nitrous acid when compared with nitrite. Interestingly, benzene does not react with HNO₂ alone in the dark. An important feature of benzene nitration in the presence of NO₂⁻/HNO₂ under irradiation is that the process is not inhibited by the addition of hydroxyl scavengers, differently from the case of phenol nitration. This finding indicates that nitrite irradiation might lead to the nitration of certain aromatic compounds in natural waters even in the presence of natural hydroxyl scavenging agents, which are usually thought to limit the environmental role of many photochemical processes.     

浸渍-碱性微波法载磁活性炭粉对壬基酚的吸附

利用浸渍-碱性微波法制备载磁粉末活性炭,通过等温吸附实验和动力学吸附实验,研究对比了其与原料活性炭、浸渍载铁活性炭对壬基酚的吸附性能。采用氮气吸附仪、FTIR、XRD、国标(GB/T12496.19-1999)邻菲啰啉分光度法及VSM,分别对3种样品进行了物相结构、表面官能团、铁含量及磁性能的分析,并探讨了吸附机理。结果表明,浸渍-碱性微波法载磁活性炭的总孔容及孔隙率均有较大提高;其吸附等温线符合Freundich方程,吸附动力学过程符合准二级动力学方程与孔道内扩散模型,相关系数R2均大于0.900。原活性炭经一定浓度的铁盐溶液浸渍后,铁含量由2%提高到8%。在碱性、N2气氛条件下微波后,铁系物主要存在形式为零价铁和Fe3O4,制得的载磁活性炭饱和磁化强度为1.12 emu/g。     

Structure characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane

1,2-Dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) is used primarily as an additive flame retardant. 1H NMR spectroscopy and an X-ray structure determination have revealed that a technical mixture consists largely of two (of the four possible) diastereomers, rac-(1R,2R)-1,2-dibromo-(4S)-4-((1S)-1,2-dibromoethyl)cyclohexane (alpha-TBECH) and rac-(1R,2R)-1,2-dibromo-(4S)-4-((1R)-1,2-dibromoethyl)cyclohexane (beta-TBECH), in a mole ratio of approximately 1:1. The two other possible isomers, gamma- and delta-TBECH, were not detected in a technical mixture. The TBECH isomers are thermally sensitive and can easily interconvert at temperatures of 125 degrees C. A thermal equilibrium mixture of alpha-, beta-, gamma- and delta-TBECH consists of approximately 33%, 33%, 17% and 17% of these isomers, respectively. Separation of all four TBECH diastereomers, with minimal thermal interconversion of the isomers, was achieved by careful selection of GC-capillary column length and injector temperature. Although technical TBECH does not contain the gamma- and delta-isomers, they may still be relevant environmental contaminants since manufacturing processes utilize thermal processes which may induce their formation.     

Passive dosing: an approach to control mutagen exposure in the Ames fluctuation test

By using dialysis equilibrium experiments, the sorption of a branched nonylphenol isomer [4-(1-ethyl-1,3-dimethylpentyl)-phenol] (NP111) on various humic acids (HAs) isolated from river sediments and two reference HAs was studied. The HAs were characterized by solid-state ¹³C direct polarization/magic angle spinning nuclear magnetic resonance (¹³C DP/MAS NMR) spectroscopy. Sorption isotherms of NP111 on HAs were described by a linear model. The organic carbon-normalized sorption coefficient (K_OC) ranged from 2.3 × 10³ to 1.5 × 10⁴ L kg⁻¹. Interestingly, a clear correlation between K_OC value and alkyl C content was observed, indicating that the aliphaticity of HAs markedly dominates the sorption of NP111. These new mechanistic insights about the NP111 sorption indicate that the fate of nonylphenols in soil or sediment depends not only on the content of HA, but also on its structural composition.     

Enantioselective separation and determination of single nonylphenol isomers

It has recently become clear that an isomer specific view of technical 4-nonylphenol (NP) is absolutely necessary for the evaluation of the biological behavior of NP, raising additional questions concerning enantiomer specific effects. For the first time, in this study enantioselective HPLC was applied to enantiomeric separation of chiral NP isomers. A semipreparative separation of two NP isomers could be achieved. A GC-MS method has been developed for the simultaneous detection of three chiral NP isomers in water samples. Investigation of influent and effluent samples from a wastewater treatment plant in Germany indicated that enantioselective degradation could occur in the environment. In one examined influent, an enantiomer ratio of 1.7 for two different isomers was determined.     

On-line solid-phase extraction and fluorescence detection of selected endocrine disrupting chemicals in water by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed to analyse selected endocrine disrupting chemicals in water by using automated on-line solid-phase extraction with a fluorescence detector. The excitation and emission wavelengths of the fluorescence detector were 230 nm and 290 nm, respectively. The selected endocrine disrupting chemicals include hormone steroids such as estradiol (E2), estriol (E3), ethynylestradiol (EE2), and ethynylestradiol 3-methyl ether (MeEE2) as well as nonylphenols (NP), octylphenols (OP), POE(1-2) nonyl phenol (NPE) and bisphenol A (BP). Three types of on-line cartridges (C18, PLRP-s and PRP-1) were tested to pre-concentrate the endocrine disruptors in deionised water. It was found that the recoveries of these chemicals at 1 microg/L were close to 100% except for 4-octyl phenol and 4-n-nonyl phenol, which had recoveries of about 40% to 80%. The two polymer cartridges (PLRP-s and PRP-1) gave higher recoveries than the C18 cartridges. The addition of methanol at 5% to 10% in water significantly improved the recovery of 4-octyl phenol and 4-n-nonyl phenol. The addition of methanol also led to an improvement in the recovery with C18 cartridges. With the addition of methanol in water samples, these three types of cartridges gave similar recoveries for the chemicals. The detection limits of this method ranged from 20 ng/L to 50 ng/L. A river water sample spiked with these chemicals was analysed using the above method and we found no interference with the peaks of the selected endocrine disrupting chemicals. The recoveries for these chemicals were more than 92% except for 4-NP with a recovery of 61%. This relatively simple method is useful for laboratory studies on the environmental fate of these endocrine disrupting chemicals in water.     

Atmospheric concentrations and air-sea exchanges of nonylphenol, tertiary octylphenol and nonylphenol monoethoxylate in the North Sea

Concentrations of nonylphenol isomers (NP), tertiary octylphenol (t-OP) and nonylphenol monoethoxylate isomers (NP1EO) have been simultaneously determined in the sea water and atmosphere of the North Sea. A decreasing concentration profile appeared following the distance increasing from the coast to the central part of the North Sea. Air-sea exchanges of t-OP and NP were estimated using the two-film resistance model based upon relative air-water concentrations and experimentally derived Henry's law constant. The average of air-sea exchange fluxes was -12+/-6 ng m(-2)day(-1) for t-OP and -39+/-19 ng m(-2)day(-1) for NP, which indicates a net deposition is occurring. These results suggest that the air-sea vapour exchange is an important process that intervenes in the mass balance of alkylphenols in the North Sea.     

Degradation of organic pollutants in Mediterranean forest soils amended with sewage sludge

The degradation of two groups of organic pollutants in three different Mediterranean forest soils amended with sewage sludge was studied for nine months. The sewage sludge produced by a domestic water treatment plant was applied to soils developed from limestone, marl and sandstone, showing contrasting alkalinity and texture. The compounds analysed were: linear alkylbenzene sulphonates (LAS) with a 10–13 carbon alkylic chain, and nonylphenolic compounds, including nonylphenol (NP) and nonylphenol ethoxylates with one and two ethoxy groups (NP1EO + NP2EO). These compounds were studied because they frequently exceed the limits proposed for sludge application to land in Europe. After nine months, LAS decomposition was 86–96%, and NP + NP1EO + NP2EO decomposition was 61–84%, which can be considered high. Temporal trends in LAS and NP + NP1EO + NP2EO decomposition were similar, and the concentrations of both types of compounds were highly correlated. The decomposition rates were higher in the period of 6–9 months (summer period) than in the period 0–6 months (winter + spring period) for total LAS and NP + NP1EO + NP2EO. Differences in decay rates with regard to soil type were not significant. The average values of decay rates found are similar to those observed in agricultural soils.     

Anaerobic degradation of nonylphenol in soil

This study investigated the effects of various factors on the anaerobic degradation of nonylphenol (NP) in soil. The results show that the optimal pH for NP degradation was 7.0 and that the degradation rate was enhanced when the temperature was increased. The addition of compost enhanced NP degradation. The individual addition of the electron donors lactate, acetate, and pyruvate inhibited NP degradation. The high-to-low order of NP degradation rates under three anaerobic conditions was sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the anaerobic degradation of NP, with sulfate-reducing bacteria being a major component of the soil. Of the anaerobic strains isolated from the soil samples, strain AT3 expressed the best ability to biodegrade NP.     

Photochemical oxidation of reduced sulfur compounds in an urban location based on short time monitoring data

This study examines the oxidation of reduced sulfur compounds (RSCs) in urban ambient air. The photochemical conversions of RSC (such as DMS, CS₂, H₂S, DMDS, and CH₃SH) to a further oxidized form (e.g., SO₂, MSA, and H₂SO₄) were assessed using a photochemical box model. For our model simulation of RSC oxidation, measurements were taken at an urban monitoring station in Seoul, Korea (37.6° N, 127° E) during three separate time periods (e.g., Sept. 17–18, Oct. 23, and Oct. 27–28, 2003). The results indicate that DMS and H₂S were the dominant RSCs with concentrations of 370 ± 140 and 110 ± 60 pptv, respectively. The photochemical conversion of DMDS to SO₂ was found to occur more efficiently than other RSCs. The overall results of our study suggest that photochemical conversion of RSCs accounted for less than 15% of the observed SO₂ during the measurement period. The SO₂ production from DMS oxidation (mainly by the reaction with OH) was found to be affected primarily by the abstraction channel due to high NO_x levels during the experimental conditions.