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ABSTRACT: A 480 L evacuable reaction chamber, equipped with FT-IR spectroscopy on-line and ion chromatography off-line, has been used to study the gas phase reaction between the nitrate radical, NO3, and the reduced organic sulphur compounds CH3CH2SH, (CH3CH2)2S, (CH3CH2)2S2, and CH3CH2SCH3 in air. The products CH3CH2SO3H, SO2, H2SO4, CH3CHO, and CH3CH2ONO2 were identified and quantified in the reactions of the first three compounds, CH3CH2SH, (CH3CH2)2S, and (CH3CH2)2S2. The reaction products were CH3CH2SO3H, CH3SO3H, SO2, H2SO4, CH3CHO, and CH2O in the reaction of CH3CH2SCH3. On the basis of identified reaction products and intermediates observed in the infrared spectra, mechanisms are proposed for the reactions between the NO3 radical and the four reduced organic sulphur compounds. The results of this study, together with those from previous experiments performed in this laboratory on CH3SCH3, CH3SH, and CH3SSCH3 lead to the conclusion that all these species, in the reaction with the NO3 radical, follow a similar degradation mechanism producing SO2, H2SO4, RSO3H, RCHO, and RCH2ONO2, as the main reaction products. The inital step of the reaction of NO3 with RSR and RSH type (R = CH3, CH2CH3) reduced organic sulphur compounds was found to be H-atom abstraction, probably after the formation of an initial adduct. For the reaction between NO3 and RSSR type compounds, evidence for an addition-decomposition reaction, as the initial steps, was obtained. RS·, RS(O)·, and RS(O)2· appear to be formed as intermediates in all the reactions. © John Wiley & Sons, Inc.
International Journal of Chemical Kinetics 09/2004; 24(10):839 - 850. · 1.01 Impact Factor
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04/2002;
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ABSTRACT: Measurements of nitrogen dioxide using the Palmes diffusion tubes in Uummannaq, Aasiaat, and Nuuk. all located along the west-coast of Greenland, have demonstrated that the levels of pollution at the most heavily impacted sites are comparable to levels in much larger towns in Denmark. The highest concentrations were, in general, observed near sites influenced by car traffic (peak concentrations of up to 16 ppbv), medium concentrations were observed in the residential areas (2 6 ppbv), and very low levels were found at the background locations in the town outskirts (1-2 ppbv). Observations of nitrogen dioxide concentrations less than 0.1 ppbv at a remote site, Akia, 25 km from Nuuk, indicate that, compared to local sources, long-range transport of nitrogen dioxide is not important in western Greenland.
Journal of Environmental Monitoring 03/2001; 3(1):139-45. · 1.99 Impact Factor
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ABSTRACT: Epidemiological and toxicological studies often require the analysis of large numbers of samples for biological markers of exposure. The goal of this work was to develop a class-selective ELISA to detect groups of structurally closely related mercapturic acids with small nonpolar S-substituents. An assay was developed with strong recognition for mercapturates including S-benzylmercapturic acid (IC50 = 0.018 micromol/L), S-n-hexylmercapturic acid (IC50 = 0.021 micromol/L), S-phenylmercapturic acid (IC50 = 0.024 micromol/L), and S-cyclohexylmethylmercapturic acid (IC50 = 0.042 micromol/L). The same assay also showed weaker recognition for S-(1-hydroxynaphthal-2-yl)mercapturic acid and S-allylmercapturic acid (IC50 = 1.1 and 1.7 micromol/L, respectively). Subtle modifications to the hapten linker structure of the coating antigen proved to have a strong impact on the selectivity and the specificity of the assay. A slightly modified assay showed high recognition for S-benzylmercapturic acid (IC50 = 0.018 micromol/L) and weaker recognition for seven other mercapturic acids (IC50 = 0.021-10 micromol/L). Strong positive assay responses were detected in 12 urine samples obtained from persons with no known occupational exposure to exogenous electrophilic xenobiotics. Solid phase extraction and cross-reactivity indicated that the presumptive immunoreactive materials were similar in size and polarity to S-benzylmercapturic acid. The assay was more selective to mercapturic acids than the spectrophotometric thioether assay.
Journal of Agricultural and Food Chemistry 01/2001; 48(12):5913-23. · 2.82 Impact Factor
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F S Rowland,
D R Blake,
B R Larsen,
A Lindskog,
P J Peterson,
W P Williams,
T J Wallington,
M J Pilling,
N Carslaw,
D J Creasey, [......],
F Plana,
B Artiño,
A Rauterberg-Wulff,
G W Israël,
T A Rocha,
A C Duarte,
A Röhrl,
G Spindler,
M R Strommen,
R Berkowicz
Environmental Science and Pollution Research 02/1998; 5(3):119-96. · 2.65 Impact Factor
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ABSTRACT: The aims of the study were to evaluate if the front-door concentrations of benzene, toluene, and xylenes can be used to classify the personal exposures of Danish children and to identify factors that affect their personal exposure. Average concentrations were measured over 1 week with diffusive samplers, and the personal exposures of 98 children and the concentrations outside the front doors of their homes were measured simultaneously. Time and activity patterns were noted in diaries. The front-door concentrations were significantly higher in Copenhagen than in rural areas (all P < 0.0001), but the personal exposures were only slightly higher. Even though the personal exposures were highly significantly associated with front-door concentrations in urban areas (all P < 0.004), use of the residential front-door concentration as an exposure surrogate would imply misclassification, as it cannot be used for rural children. Multiple regression analyses brought to light several factors that affect the exposure of children independently, including front-door concentration, riding in cars, and activities involving potential exposure to gasoline vapors like motocross, moped driving, and refueling of cars.
Environmental Research 11/1997; 75(2):149-59. · 3.40 Impact Factor
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ABSTRACT: The aims of the study were to evaluate the front-door concentration of traffic exhaust fumes as a surrogate for the personal exposure of children and to study factors in the behavior and the environment of children that affect their personal exposure to nitrogen dioxide (NO(2)). The exposure to NO(2) of 103 children living in Copenhagen and 101 children living in rural areas of Denmark was studied by measuring average concentrations over 1 week with diffusive badge samplers placed outside the front door of the home, inside the child's bedroom, and on each child. Detailed information about the activities of the children involving potential exposure to NO(2) was noted in diaries. The results indicated that the front-door concentration of traffic pollution might be used to classify the personal exposure of urban children, although misclassification would be introduced. Multiple regression analysis showed several factors that affected the personal NO(2) exposure of the children independently, including the front-door concentration, the bedroom concentration, time spent outdoors, gas appliances used at home, passive smoking, and burning candles.
Environmental Health Perspectives 10/1997; 105(9):964-70. · 7.04 Impact Factor
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ABSTRACT: Formic and acetic acid measured as daily averages in 1993–1994show equal and highly correlated concentrations up to 3 ppb in the summer(May–August). In the winter (October–March) the formicacid/acetic acid ratio was 0.6 and the formic acid concentrations wereusually below 1 ppb. In winter the carboxylic acids correlate withOx, NOy, SO2 and particulatesulphur. The main sources are suggested to be ozonolysis of anthropogenicalkenes and reactions between peroxyacetyl radicals and RO2radicals. In spring–summer the carboxylic acids correlate withO3, Ox, HNO3, PAN,NOy, SO2, particulate sulphur and temperature.In addition to the sources of the winter a contribution from ozonolysis ofbiogenic alkenes is likely. Quite similar formic acid/acetic acid ratios forall wind directions suggest that the source(s) are atmospheric oxidationprocesses distributed over large areas. The highest concentrations occurringfor winds from east to south and the correlation with e.g., particulatesulphur indicate chemical production in polluted air masses during longrange transport.
Journal of Atmospheric Chemistry 01/1997; 28(1):195-207. · 0.99 Impact Factor
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ABSTRACT: Products and mechanisms of the reaction between the nitrate radical (NO3) and three of the most abundant reduced organic sulphur compounds in the atmosphere (CH3SCH3, CH3SH and CH3SSCH3), have been studied in a 480 L reaction chamber using in situ FT-IR and ion chromatography as analytical techniques. In the three reactions, methanesulphonic acid was found to be the most abundant sulphur containing product. In addition the stable products SO2, H2SO4, CH2O, and CH3ONO2 were identified and quantified and thionitric acid-S-methyl ester (CH3SNO2) Was observed in the i.r. spectrum from all of the three reactions. Deuterated dimethylsulphide (CD3SCD3) showed an isotope effect on the reaction rate constant (k(H)/k(D)) of 3.8 +/- 0.6, indicating that hydrogen abstraction is the first step in the NO3 + CH3SCH3 reaction, probably after the formation of an initial adduct. Based on the products and intermediates identified, reaction mechanisms are proposed for the three reactions.
Journal of Atmospheric Chemistry 04/1992; 14(1-4). · 0.99 Impact Factor
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ABSTRACT: Products and mechanisms of the reaction between the nitrate radical (NO3) and three of the most abundant reduced organic sulphur compounds in the atmosphere (CH3SCH3, CH3SH and CH3SSCH3), have been studied in a 480 L reaction chamber using in situ FT-IR and ion chromatography as analytical techniques. In the three reactions, methanesulphonic acid was found to be the most abundant sulphur containing product. In addition the stable products SO2, H2SO4, CH2O, and CH3ONO2 were identified and quantified and thionitric acid-S-methyl ester (CH3SNO2) was observed in the i.r. spectrum from all of the three reactions. Deuterated dimethylsulphide (CD3SCD3) showed an isotope effect on the reaction Deuterated dimethylsulphide (CD3SCD3) showed an isotope effect on the reaction rate constant (kH/kD) of 3.80.6, indicating that hydrogen abstraction is the first step in the NO3+CH3SCH3 reaction, probably after the formation of an inital adduct.Based on the products and intermediates identified, reaction mechanisms are proposed for the three reactions.
Journal of Atmospheric Chemistry 03/1992; 14(1):95-108. · 0.99 Impact Factor
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ABSTRACT: The aim of the study was to evaluate the predictions derived from the Danish Operational Street Pollution Model (OSPM) when the input data are obtained by simple methods that could be used in large-scale epidemiological studies. The model calculations were thus compared with passive sampler measurements of nitrogen dioxide and benzene at 103 street locations in Copenhagen, Denmark, and at 101 locations in rural areas. Data on traffic and street configuration were collected by means of a simple registration scheme in which forms were filled out by local municipal authorities. Meteorological data were derived from routine measurements at Copenhagen airport, and data on background air pollution were based on a simple empirical model. Differences in air pollution levels between rural areas and Copenhagen and differences in nitrogen dioxide concentrations at various locations in Copenhagen were well reproduced by the OSPM. The correlation coefficients (r) between the measured and the predicted half-year average concentrations of nitrogen dioxide in Copenhagen were between 0.75 and 0.80 for various degrees of precision of the input data for the model. The results indicate that the OSPM used with the presented methods for generation of input data might be useful in assessing long-term exposure to air pollutants in epidemiological studies.
Journal of Exposure Analysis and Environmental Epidemiology 10(1):4-14. · 2.72 Impact Factor
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ABSTRACT: The reaction between NO3 and dimethylsulphide (DMS) in air has been studied in a 480 ℓ reaction chamber. Intermediates and end products were identified by FT-IR and ion chromatography.HNO3, CH2O, SO2 and methanesulphonic acid were found to be the main products of the reaction, with methanesulphonic acid as the most abundant sulphur compound. Organic peroxynitrates and CH3SNO2 have been identified as intermediates from their characteristics spectral features. Based on the results obtained a mechanism for the reaction DMS+NO3 is proposed, which has hydrogen abstraction as the first step. The formation of HNO3 followed by removal of HNO3 by deposition may represent an efficient night-time sink of NOx in the marine troposphere.
Atmospheric Environment. Part A. General Topics.
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ABSTRACT: The atmospheric concentrations of formaldehyde, acetaldehyde and acetone were measured by the DNPH-technique at the semi-rural site Lille Valby, Denmark (55°N) between May–July 1995. The average concentrations were observed to be 1.2 ppbv for formaldehyde, 0.8 ppbv for acetaldehyde and 1.9 ppbv for acetone. For the set of carbonyl compounds, concentrations were found to be highly correlated, though only during daytime. The weak correlations observed during nighttime are believed to be caused by the dry deposition of especially formaldehyde. During periods with low photochemical activity the carbonyl compounds also correlated with SO2 and the levels of carbonyl compounds were mainly controlled by meteorological parameters. The highest concentration levels were coincident with episodes of long-range transport from central Europe. A pronounced diurnal profile similar to those observed for PAN and ozone during high-pressure episodes also indicated that photochemical production was a major controlling factor. Here the highest concentrations of carbonyl compounds were observed in air masses with the highest photochemical age (PCA) and a likely source was determined to be the oxidation of hydrocarbons during long-range transport. Especially, the concentration levels of acetone showed a pronounced seasonal variation with the highest levels observed during summertime and lowest in winter and spring. The seasonal variation in the concentration levels of formaldehyde and acetaldehyde were small, thus indicating a low net photochemical production of these components. The measurements were validated by a laboratory intercomparison and good agreement was observed.
Atmospheric Environment.
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ABSTRACT: Mercury concentrations are clearly elevated in the surface and sub-surface layers of peat cores collected from a minerotrophic (“groundwater-fed”) fen in southern Greenland (GL) and an ombrotrophic (“rainwater-fed”) bog in Denmark (DK). Using 14C to precisely date samples since ca. AD 1950 using the “atmospheric bomb pulse,” the chronology of Hg accumulation in GL is remarkably similar to the bog in DK where Hg was supplied only by atmospheric deposition: this suggests not only that Hg has been supplied to the surface layers of the minerotrophic core (GL) primarily by atmospheric inputs, but also that the peat cores have preserved a consistent record of the changing rates of atmospheric Hg accumulation. The lowest Hg fluxes in the GL core (0.3 to 0.5 μg/m2/yr) were found in peats dating from AD 550 to AD 975, compared to the maximum of 164 μg/m2/yr in AD 1953. Atmospheric Hg accumulation rates have since declined, with the value for 1995 (14 μg/m2/yr) comparable to the value for 1995 obtained by published studies of atmospheric transport modelling (12 μg/m2/yr).The greatest rates of atmospheric Hg accumulation in the DK core are also found in the sample dating from AD 1953 and are comparable in magnitude (184 μg/m2/yr) to the GL core; again, the fluxes have since gone into strong decline. The accumulation rates recorded by the peat core for AD 1994 (14 μg/m2/yr) are also comparable to the value for 1995 obtained by atmospheric transport modelling (18 μg/m2/yr). Comparing the Pb/Ti and As/Ti ratios of the DK samples with the corresponding crustal ratios (or “natural background values” for preanthropogenic peat) shows that the samples dating from 1953 also contain the maximum concentration of “excess” Pb and As. The synchroneity of the enrichments of all three elements (Hg, Pb, and As) suggests a common source, with coal-burning the most likely candidate. Independent support for this interpretation was obtained from the Pb isotope data (206Pb/207Pb = 1.1481 ± 0.0002 in the leached fraction and 1.1505 ± 0.0002 in the residual fraction) which is too radiogenic to be explained in terms of gasoline lead alone, but compares well with values for U.K. coals. In contrast, the lowest values for 206Pb/207Pb in the DK profile (1.1370 ± 0.0003 in the leached fraction and 1.1408 ± 0.0003 in the residual fraction) are found in the sample dating from AD 1979: this shows that the maximum contribution of leaded gasoline occurred approximately 25 yr after the zenith in total anthropogenic Pb deposition.
Geochimica et Cosmochimica Acta.
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ABSTRACT: Terpene fluxes from a Norway spruce (Picea abies) forest and an orange orchard (Citrus clementii and Citrus sinensis) were measured by relaxed eddy accumulation (REA) during summer 1997. α-pinene and β-pinene were the most abundant terpenes emitted from Norway spruce and constituted approximately 70% of the flux. A much lower flux was observed for myrcene, limonene and γ-terpinene and both α-terpinene and camphor were only occasionally detected. The average terpene flux was 107.6 ng m−2 s−1 which corresponds to 0.73 μg g(dw)−1 h−1 (30°C) when calculated relatively the weight of the dry biomass. The five terpenes which were detected in all samples at the orange orchard were limonene, sabinene, α-pinene, trans-ocimene and β-pinene with an average flux of 126.3 ng m−2 s−1. Cis-ocimene, linalool and myrcene were occasionally detected but no systematic upward or downward flux was observed. The results from a laboratory intercomparison made in Spain deviated by maximum 7%. The flux measured at the two sites exhibited a strong diurnal variation with maximum in the afternoon and minimum in the morning hours and evenings. The applied REA system is new in its design and the major advantage is that the air is sampled at a constant flow rate on the adsorbent tubes. This is realised by having two primary Teflon lines with a relatively large flow rate (6 l min−1). The air is then sampled from these two Teflon lines on two identical adsorbent tubes at a constant and much lower rate by using two precision pumps operated at approximately 60 ml min−1. The terpenes collected on the adsorbent tubes were significantly decomposed by ozone during sampling unless ozone scrubbers were applied.
Atmospheric Environment.
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W. Shotyk,
M.E. Goodsite,
F. Roos-Barraclough,
N. Givelet,
G. Le Roux,
D. Weiss,
A.K. Cheburkin,
K. Knudsen,
J. Heinemeier,
W.O. van Der Knaap,
S.A. Norton, C. Lohse
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ABSTRACT: A monolith representing 5420 14C yr of peat accumulation was collected from a blanket bog at Myrarnar, Faroe Islands. The maximum Hg concentration (498 ng/g at a depth of 4.5 cm) coincides with the maximum concentration of anthropogenic Pb (111 μg/g). Age dating of recent peat accumulation using 210Pb (CRS model) shows that the maxima in Hg and Pb concentrations occur at AD 1954 ± 2. These results, combined with the isotopic composition of Pb in that sample (206Pb/207Pb = 1.1720 ± 0.0017), suggest that coal burning was the dominant source of both elements. From the onset of peat accumulation (ca. 4286 BC) until AD 1385, the ratios Hg/Br and Hg/Se were constant (2.2 ± 0.5 × 10-4 and 8.5 ± 1.8 × 10-3, respectively). Since then, Hg/Br and Hg/Se values have increased, also reaching their maxima in AD 1954. The age date of the maximum concentrations of anthropogenic Hg and Pb in the Faroe Islands is consistent with a previous study of peat cores from Greenland and Denmark (dated using the atmospheric bomb pulse curve of 14C), which showed maximum concentrations in AD 1953.The average rate of atmospheric Hg accumulation from 1520 BC to AD 1385 was 1.27 ± 0.38 μg/m2/yr. The Br and Se concentrations and the background Hg/Br and Hg/Se ratios were used to calculate the average rate of natural Hg accumulation for the same period, 1.32 ± 0.36 μg/m2/yr and 1.34 ± 0.29 μg/m2/yr, respectively. These fluxes are similar to the preanthropogenic rates obtained using peat cores from Switzerland, southern Greenland, southern Ontario, Canada, and the northeastern United States. Episodic volcanic emissions and the continual supply of marine aerosols to the Faroe Islands, therefore, have not contributed significantly to the Hg inventory or the Hg accumulation rates, relative to these other areas. The maximum rate of Hg accumulation was 34 μg/m2/yr. The greatest fluxes of anthropogenic Hg accumulation calculated using Br and Se, respectively, were 26 and 31 μg/m2/yr. The rate of atmospheric Hg accumulation in 1998 (16 μg/m2/yr) is comparable to the values recently obtained by atmospheric transport modeling for Denmark, the Faroe Islands, and Greenland.
Geochimica et Cosmochimica Acta.
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ABSTRACT: Products and mechanisms of the reaction of NO3 with isoprene have been studied under simulated atmospheric conditions with in situ FTIR spectroscopy as analytical technique. The study addressed also the reactions of NO3 with 1,3-butadiene and 2,3-dimethyl-1,3-butadiene as well as with the deuterated species 1,1,4,4-d4-1,3-butadiene, d6-1,3-butadiene and 4,4-d2-2-methyl-1,3-butadiene (d2-isoprene). The dienes examined apparently follow very similar reaction pathways. The decay of the intermediate peroxynitrates formed after the addition of NO3 to one of the methylene groups, leads to unsaturated ketone-nitrate, aldehyde-nitrate, alcohol-nitrate and perhaps also dinitrate species. The yield of unsubstituted carbonyl compounds was insignificant in the reactions of NO3 with 1,3-butadiene and isoprene. In the case of isoprene, NO3 reacts adding preferentially to the 1-position and 3-methyl-4-nitroxy-2-butenal appears to be the main product. 1,3-Butadiene predominantly reacts with NO3 via trans-1,4-addition and 1,2-addition while the cis-1,4-addition path is of minor importance. trans-4-Nitroxy-2-butenal and 1-nitroxy-3-buten-2-one were found as main products. Contrary to the daytime OH-initiated degradation of isoprene, the nighttime oxidation of isoprene by NO3 leads to formation of large quantities of organic nitrate compounds; this may have consequences for the tropospheric NOy budget as briefly discussed.
Atmospheric Environment. Part A. General Topics.
