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PubMed2004

Atmospheric transport of polybrominated diphenyl ethers and polychlorinated biphenyls to the Baltic Sea.

The atmospheric transport of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) was compared by measuring concentrations in air and deposition on an island located in the central basin of the Baltic Sea. Median sigmaPBDE and sigmaPCB concentrations (gaseous + particle) were 8.6 and 7.4 pg m(-3), respectively. Airborne PCBs were mainly found in the gaseous phase, while most of the PBDEs were detected on particles, which agrees with predicted particle/gas distributions. SigmaPBDE levels were dominated by the decabrominated BDE209 followed bythe tetrabrominated BDE47 and pentabrominated BDE99. BDE209 is a marker for the environmental distribution of the commercial deca-BDE formulation (>99.5% BDE209), whereas BDE47 and BDE99 are markers for the commercial penta-BDE mixture. General correlations between PBDEs and PCBs suggested similarities in sources and transport mechanism, while more detailed examination of the data identified notable behaviors and exceptions. Differences in regression slopes among tetra-, penta-, and decabrominated PBDEs may reflect different transport processes and the change in usage pattern. Tetra- and pentabrominated PBDEs may originate from secondary sources such as air surface exchange in a manner similar to that of the PCBs, while the deca-BDE209 formulation still has primary sources. The tribrominated BDE17 was also detected and is proposed to be a breakdown product due to atmospheric debromination processes. PBDEs had higher washout ratios than PCBs, explaining their higher concentrations compared to PCBs in precipitation (median of 6.0 and 0.5 ng L(-1) for sigmaBDE and sigmaPCB concentrations ("dissolved" + particle), respectively) than in air. The calculated yearly deposition of PBDEs and PCBs indicated that the atmospheric input of PBDEs to the Baltic Proper is currently exceeding that of the PCBs by a factor of 40, while that of the PCBs is decreasing.

Air Movements↗
PubMed2004

Tracing atmospheric nitrate deposition in a complex semiarid ecosystem using delta17O.

The isotopic composition of nitrate collected from aerosols, fog, and precipitation was measured and found to have a large 17O anomaly with delta17O values ranging from 20 percent per thousand to 30% percent per thousand (delta17O = delta17O - 0.52(delta18O)). This 17O anomaly was used to trace atmospheric deposition of nitrate to a semiarid ecosystem in southern California. We demonstrate that the delta17O signal is a conserved tracer of atmospheric nitrate deposition and is a more robust indicator of N deposition relative to standard delta18O techniques. The data indicate that a substantial portion of nitrate found in the local soil, stream, and groundwater is of atmospheric origin and does not undergo biologic processing before being exported from the system.

Aerosols↗
PubMed2005

Determination of methoxyphenols in ambient atmospheric particulate matter: tracers for wood combustion.

Combustion of wood and other biomass fuels produces source-specific organic compounds arising from pyrolysis of lignin, including substantial amounts of 4-substituted methoxylated phenolic compounds (methoxyphenols). These compounds have been used as atmospheric markers to determine the contribution of wood smoke to ambient atmospheric fine particulate matter (PM). However, reliable quantification of methoxyphenols represents an analytical challenge because these compounds are polar, semi-volatile, and somewhat reactive. We reportherein an improved gas chromatographic-mass spectrometric (GC/MS) method for the sensitive and reliable determination of methoxyphenols in low-volume ambient PM samples. Deuterated standard compounds are added to the environmental samples prior to extraction to determine analyte recoveries in each sample. Analytical figures of merit for the assay, as applied to ambient PM2.5 and PM10 samples are as follows: recovery = 63-100%; precision = 2-6%; analytical limit of detection (S/N 2) = 0.002 microg/mL; limit of quantitation = 0.07-0.45 ng/m3 (assuming a 14 m3 sample). The improved method was applied to ambient PM samples collected between 1999 and 2000 in Seattle, WA. Particle-bound methoxyphenol concentrations in the range <0.1 to 22 ng/m3 were observed and the methoxyphenols were present almost exclusively in the fine (PM2.5) size fraction. We also demonstrated that XRF analysis of samples of atmospheric PM collected on Teflon filters significantly reduced the levels of methoxyphenols measured in the PM samples in subsequent assay of the same filters. Therefore, XRF analysis of filters, commonly undertaken to obtain trace element concentrations for use in source apportionment analyses, would preclude the subsequent analysis of those filters for methoxyphenols and other similarly semivolatile or reactive organic chemicals.

Air Pollutants↗
PubMed2005

Regional assessment of the response of the acid-base status of lake watersheds in the Adirondack region of New York to changes in atmospheric deposition using PnET-BGC.

Understanding the response of soil and surface waters to changes in atmospheric deposition is critical for guiding future legislation on air pollution. The Adirondack region of New York experiences among the most severe ecological impacts from acidic deposition. The region is characterized by considerable variability in atmospheric deposition, surficial and bedrock geology, hydrologic flow paths, and vegetation resulting in variability in effects of acidic deposition. In this study, an integrated biogeochemical model (PnET-BGC) was applied to 37 forest lake watersheds to assess the response of soil and surface waters of the Adirondacks to changes in atmospheric deposition at a regional scale. Model-simulated surface water chemistry was validated against data from two synoptic surveys conducted in 1984 and 2001. Results indicate that the model is able to capture the observed changes in surface water chemistry during this period. The model was further used to forecast the response of soil and surface waters to three future emission control scenarios. Results indicate that under the Clean Air Act, surface water SO4(2-) concentrations will continue to decrease at a median rate of -0.38 microeq/L-yr, and surface water ANC is predicted to increase at a median rate of 0.11 microeq/L-yr. More aggressive emission reductions will accelerate the rate of recovery. Under an aggressive control scenario, which represents an additional 75% reduction in SO2 emissions beyond the implementation of the Clean Air Act, surface water SO4(2-) concentrations are predicted to decrease at a median rate of -0.88 microeq/L-yr, and surface water ANC is predicted to increase at a median rate of 0.43 microeq/L-yr. Model predictions of several biologically relevant chemical indicators are also reported.

Acid Rain↗
PubMed2005

Atmospheric concentrations and deposition of polycyclic aromatic hydrocarbons to the Mid-Atlantic East Coast region.

Atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured at urban/industrial, suburban, coastal, and rural areas in New Jersey as part of the New Jersey Atmospheric Deposition Network. Concentrations of 36 PAH compounds were measured in the gas and particle phases in air and in precipitation at nine sites at regular intervals from October 1997 through May 2001. Gas-phase and particle-phase sigma36PAH concentrations ranged from 0.45 to 118 ng m(-3) and from 0.046 to 172 ng m(-3), respectively, and precipitation concentrations ranged from 11 to 16200 ng L(-1). PAH concentrations vary spatially across the region, with the highest concentrations occurring at the most heavily urban and industrial locations. Average gas absorption deposition ranged from 0.004 (naphthacene) to 5040 (methylphenanthrenes) ng m(-2) d(-1), and dry particle deposition PAH fluxes ranged from 0.11 (naphthacene) to 300 (benzo[b+k]fluoranthene) ng m(-2) d(-1) at the nine sites. Average atmospheric wet deposition PAH fluxes at the seven sites ranged from 0.40 (cyclopenta[cd]pyrene) to 140 (methylphenanthrenes) ng m(-2) d(-1). These represent the first comprehensive estimates of PAH deposition to New Jersey and the Mid-Atlantic East Coast.

Air↗
PubMed2006

Spray irrigation of treated municipal wastewater as a potential source of atmospheric PBDEs.

Spray irrigation facilities utilizing treated municipal wastewater are a potential source of polybrominated diphenyl ethers (PBDEs) to the atmosphere. PBDEs are used as flame retardants in many household items and have been found in wastewaters and biosolids. Evidence of PBDE release from spray irrigation facilities was discovered during a multiyear project to measure semivolatile organic chemical concentrations in air. Four BDE congeners (47, 99, 100, and 154) were monitored at three remote/ rural locations in Maryland and Delaware from 2001 to 2003. Average concentrations at two of the sites (BDE-47, 10-17 pg/m3; BDE-99, 5.3-7.7 pg/m3) reflect background levels. Average concentrations at the third location were 5-10 times higher (BDE-47, 175 pg/m3; BDE-99, 26 pg/m3) and were significantly correlated (p < 0.0001) with temperature indicating local source(s). Several spray irrigation facilities are located south and west of the third site, the prevailing wind direction during the spring and summer when most samples were collected. The fine mist released from the irrigation equipment may enhance release to the atmosphere via air-water gas exchange from water droplets. Temporal trends indicate that aerial concentrations of PBDEs in this area are increasing at an exponential rate; the atmospheric doubling times for the different congeners range from 1.1 to 1.7 yrs.

Ethers↗
PubMed2006

Direct volatilization of naphthalene to the atmosphere at a phytoremediation site.

Phytoremediation systems are known to reduce groundwater contamination by at least three major mechanisms: plant uptake, phytovolatilization, and enhanced rhizosphere bioremediation. The potential for such systems to enhance a fourth remediation pathway--direct surface volatilization of contaminants through the subsurface and into the atmosphere-has not yet been investigated in the field. A vertical flux chamber was used to measure direct surface volatilization of naphthalene over nine months at a creosote-contaminated site in Oneida, Tennessee, where a phytoremediation system of poplar trees was installed in 1997. A maximum flux of 23 microg m(-2) h(-1) was measured in August 2004, and naphthalene removal by the direct volatilization pathway is estimated to be 50 g yr(-1) at this site. Results suggest that direct volatilization fluxes are most strongly affected by the groundwater level (thickness of the saturated zone), soil moisture, and changes in atmospheric pressure. At this site, transpiration and canopy interception resulting from the phytoremediation system significantly reduce the saturated thickness, increasing the vertical concentration gradient of naphthalene in the groundwater and thus increasing the upward diffusive flux of naphthalene through the subsurface. The presence of the trees, therefore, promotes direct volatilization into the atmosphere. This research represents the first known measurement of naphthalene attenuation by the direct volatilization pathway.

Air Pollutants↗
PubMed2006

Isotopic evidence in tree rings for historical changes in atmospheric sulfur sources.

Little is understood about the usefulness of sulfur isotopic ratios (sigma 34S) in tree rings because the sulfur content in rings is generally insufficient for analysis using conventional methods. We present sigma 34S values of the water-soluble and the organically bound sulfur fractions in rings of coniferous trees grown in Japan, analyzed using a large-volume oxygen bomb. Comparing the sigma 34S values of the organically bound fraction in tree rings with past atmospheric sulfur concentrations and with those of their sources, we find clear evidence that the sigma 34S values of the organically bound fraction in the rings are dependent upon the values of the atmospheric sulfur sources. The evidence suggests that the sigma 34S values in tree rings are a useful chronological proxy for evaluating possible causes of past atmospheric sulfur pollution.

Air Pollutants↗
PubMed2006

Size distribution characteristics of elemental carbon emitted from Chinese vehicles: results of a tunnel study and atmospheric implications.

The size distribution characteristics of elemental carbon (EC) emissions from Chinese vehicles have not been previously described. In this study, we collected size-segregated aerosol samples using a 10-stage MOUDI sampler (0.056-18 microm) in the Zhujiang tunnel, a roadway tunnel in the urban area of Guangzhou, China. The samples were analyzed for EC, organic carbon (OC), and inorganic ions. Fine particles had an OC/EC ratio of 0.57, indicating a dominant contribution of EC from diesel vehicles. Both EC and OC showed a dominant accumulation mode with a mass median aerodynamic diameter (MMAD) of 0.42 microm. In comparison, studies available in the literature typically reported a much lower MMAD for EC (approximately 0.1 microm) in vehicular emissions in North America. A theoretical analysis indicated that the larger EC particles observed in this study could not have resulted from after-emission growth processes (i.e., water accretion, coagulation, and vapor condensation). This leaves operating conditions such as high engine loads and low combustion efficiencies, which are more prevalent in diesel-fueled Chinese vehicles, as a more plausible inherent reason for producing the larger EC agglomerates. While fresh 0.1 microm EC particles are unlikely to act as cloud condensation nuclei (CCN), calculations showed that EC particles as large as 0.42 microm are effective CCN at atmospherically relevant critical supersaturation values of less than 1%. As a result, fresh EC particles from Chinese vehicle emissions could readily undergo cloud processing and form internal mixtures with sulfate in the residue droplet mode particles. This prediction is consistent with observations that EC frequently showed a dominant droplet mode in urban atmospheres in this region. The internal mixing of EC with highly hygroscopic sulfate would facilitate its removal by wet deposition and shorten its lifetime in the atmosphere. In addition, the light-absorbing capabilities of EC particles could also be enhanced due to their internal mixing with sulfate. Numerical aerosol models need to take these factors into consideration for better predictions of the behaviors and effects of urban aerosols in China.

Air Pollutants↗
PubMed2001

Results from the Lake Michigan Mass Balance study: concentrations and fluxes of atmospheric polychlorinated biphenyls and trans-nonachlor.

In this paper, we summarize the data and methods used to estimate atmospheric exchange of polychlorinated biphenyls (PCBs) and trans-nonachlor with Lake Michigan. This work was conducted as part of the Lake Michigan Mass Balance (LMMB) study. For the atmospheric component of the LMMB, more than 400 gas- and particulate-phase samples were collected at eight sites on the shore around the lake (shoreline) and at 14 sites on the lake (over-water). We review the quality of the data set; describe the concentrations in atmospheric gas and particulate phases; report local, instantaneous, net gas fluxes; and estimate annual deposition of the particle-associated compounds. The quality of the data set is high except for a subset of over-water samples where PCB contamination is suspected. Gas-phase trans-nonachlor concentrations (although not the resulting gas fluxes) are inversely correlated with latitude and positively correlated with temperature. Gas-phase sigmaPCBs (sum of 98 congener groups) are highest in concentration at the Chicago site and lowest at the Sleeping Bear Dunes site. The resulting sigmaPCB gas fluxes exhibit a seasonality that reflects elevated summertime gas-phase concentrations not compensated by temperature-corrected Henry's law coefficients. Particulate-phase deposition is much smaller in magnitude than gas fluxes, for either compound. Gas and particulate fluxes are comparable only at the Chicago site and only when large (> 10 microm) particulates are considered.

Hydrocarbons, Chlorinated↗
PubMed2001

Modified atmosphere packaged cheddar cheese shreds: influence of fluorescent light exposure and gas type on color and production of volatile compounds.

The influences of fluorescent light exposure and packaging atmosphere on the headspace volatiles and color of Cheddar cheese shreds were evaluated using gas chromatography-mass spectrometry and spectrocolorimetry, respectively. Cheddar cheeses were packaged under atmospheres of 100% carbon dioxide or 100% nitrogen and stored at 4 degrees C under fluorescent light for 6 weeks. Cheeses stored under carbon dioxide contained higher concentrations of aldehydes and fatty acids and lower concentrations of alcohols and esters than cheeses stored under nitrogen. Carbon dioxide atmospheres potentiated light-induced oxidation in shredded Cheddar cheeses, as evidenced by aldehyde and fatty acid headspace volatiles measured following storage. Color bleaching occurred only in cheeses packaged under carbon dioxide and exposed to light. The shift in color is proposed to be due to an interaction between carbon dioxide and high-intensity light, leading to the oxidation of the pigment molecule, bixin. The results have significant implications for procedures used to handle and store pigmented cheeses to ensure desirable flavor and consumer acceptability.

Carbon Dioxide↗
PubMed2003

L-galactono-gamma-lactone dehydrogenase aand vitamin C content in fresh-cut potatoes stored under controlled atmospheres.

L-galactono-gamma-lactone dehydrogenase (GLDH) activity and vitamin C content as ascorbic acid (AA) plus dehydroascorbic acid (DHA) were evaluated in five potato tuber cultivars (Agata, Altesse, Franceline, Manon, and Monalisa). The effect of fresh-cutting and subsequent refrigerated storage of Manon potato under different atmospheres (air, 20% CO(2) + air, 100% N(2), and vacuum packaging) on GLDH activity and vitamin C content was also determined. GLDH from the five potato tuber cultivars showed typical inhibition kinetics by high substrate concentration in the synthesis of AA from its physiological precursor L-galactonic acid-gamma-lactone (GL). GLDH activity was not correlated with the corresponding vitamin C content in any potato tuber cultivar. GLDH from all the cultivars presented a major isoform with isoelectric point (IEP) 5, which changed to IEP = 4.3 after minimal processing. In addition, the GLDH-catalyzed synthesis of AA by the new isoform showed typical Michaelis kinetics, in which the enzyme became more efficient to catalyze the reaction. Whether the change in the isoform pattern was due to either post-translational modifications or de novo synthesis of a new isoenzyme remains unanswered. Fresh-cutting increased GLDH activity from 4.7-fold (vacuum packaging) to 11-fold (air) after 6 days. In addition, 100% of vitamin C content was retained in air and decreased in the rest of atmospheres after this storage period, following the sequence vacuum packaging (89%) > 100% N(2) (78%) > 20% CO(2) + air (63%). This tendency was correlated with the corresponding GLDH activity detected in each storage atmosphere, except in the case of 20% CO(2) + air. Vacuum packaging proved to be the best storage condition, because fresh-cut potatoes did not turn brown and retained 89% of initial vitamin C content.

Air↗
PubMed2006

Glucosinolates in mixed-packaged mini broccoli and mini cauliflower under modified atmosphere.

Contents of total and individual glucosinolates of mini broccoli cv. Milady and mini cauliflower cv. Clarke were assessed to determine the effect of modified atmosphere packaging on postharvest glucosinolate dynamics of mixed mini Brassica vegetables. Therefore, mixed-packaged mini broccoli and mini cauliflower stored in food trays sealed with two different microperforated biaxial-oriented polypropylene films for up to 7 days at 8 degrees C were analyzed. The results indicate that modified atmosphere at 8% O2 + 14% CO2 was a suitable gaseous combination to maintain aliphatic and indole glucosinolates in mini broccoli for 7 days after an initial decrease at 4 days. In contrast, modified atmosphere at 1% O2 + 21% CO2 resulted in the best retention of indole glucosinolates of mini cauliflower for 7 days and also of aliphatic glucosinolates after an initial decrease at 4 days. Thus, to maintain glucosinolates and external appearance and to prevent off-odor, mini broccoli and mini cauliflower should be packed separately in suitable altered gas composition.

Brassica↗
PubMed2005

Kinetic studies of the reactions of O2(b 1sigma(g)+) with several atmospheric molecules.

Thermal rate coefficients for the removal (reaction + quenching) of O2(1sigma(g)+) by collision with several atmospheric molecules were determined to be as follows: O3, k3(210-370 K) = (3.63 +/- 0.86) x 10(-11) exp((-115 +/- 66)/T); H2O, k4(250-370 K) = (4.52 +/- 2.14) x 10(-12) exp((89 +/- 210)/T); N2, k5(210-370 K) = (2.03 +/- 0.30) x 10(-15) exp((37 +/- 40)/T); CO2, k6(298 K) = (3.39 +/- 0.36) x 10(-13); CH4, k7(298 K) = (1.08 +/- 0.11) x 10(-13); CO, k8(298 K) = (3.74 +/- 0.87) x 10(-15); all units in cm3 molecule(-1) s(-1). O2(1sigma(g)+) was produced by directly exciting ground-state O2(3sigma(g)-) with a 762 nm pulsed dye laser. The reaction of O2(1sigma(g)+) with O3 was used to produce O(3P), and temporal profiles of O(3P) were measured using VUV atomic resonance fluorescence in the presence of the reactant to determine the rate coefficients for removal of O2(1sigma(g)+). Our results are compared with previous values, where available, and the overall trend in the O2(1sigma(g)+) removal rate coefficients and the atmospheric implications of these rate coefficients are discussed. Additionally, an upper limit for the branching ratio of O2(1sigma(g)+) + CO to give O(3P) + CO2 was determined to be < or = 0.2% and this reaction channel is shown to be of negligible importance in the atmosphere.

Journal Article↗
PubMed2005

Atmospheric chemistry of 4:2 fluorotelomer alcohol (n-C4F9CH2CH2OH): products and mechanism of Cl atom initiated oxidation in the presence of NOx.

Smog chamber/FTIR techniques were used to study the Cl atom initiated oxidation of 4:2 fluorotelomer alcohol (C(4)F(9)CH(2)CH(2)OH, 4:2 FTOH) in the presence of NO(x) in 700 Torr of N(2)/O(2) diluent at 296 K. Chemical activation effects play an important role in the atmospheric chemistry of the peroxy, and possibly the alkoxy, radicals derived from 4:2 FTOH. Cl atoms react with C(4)F(9)CH(2)CH(2)OH to give C(4)F(9)CH(2)C(*)HOH radicals which add O(2) to give chemically activated alpha-hydroxyperoxy radicals, [C(4)F(9)CH(2)C(OO(*))HOH]*. In 700 Torr of N(2)/O(2) at 296 K, approximately 50% of the [C(4)F(9)CH(2)C(OO(*))HOH]* radicals decompose "promptly" to give HO(2) radicals and C(4)F(9)CH(2)CHO, the remaining [C(4)F(9)CH(2)C(OO(*))HOH]* radicals undergo collisional deactivation to give thermalized peroxy radicals, C(4)F(9)CH(2)C(OO(*))HOH. Decomposition to HO(2) and C(4)F(9)CH(2)CHO is the dominant atmospheric fate of the thermalized peroxy radicals. In the presence of excess NO, the thermalized peroxy radicals react to give C(4)F(9)CH(2)C(O(*))HOH radicals which then decompose at a rate >2.5 x 10(6) s(-1) to give HC(O)OH and the alkyl radical C(4)F(9)CH(2)(*). The primary products of 4:2 FTOH oxidation in the presence of excess NO(x) are C(4)F(9)CH(2)CHO, C(4)F(9)CHO, and HCOOH. Secondary products include C(4)F(9)CH(2)C(O)O(2)NO(2), C(4)F(9)C(O)O(2)NO(2), and COF(2). In contrast to experiments conducted in the absence of NO(x), there was no evidence (<2% yield) for the formation of the perfluorinated acid C(4)F(9)C(O)OH. The results are discussed with regard to the atmospheric chemistry of fluorotelomer alcohols.

Journal Article↗
PubMed2005

Ion atmosphere relaxation controlled electron transfers in cobaltocenium polyether molten salts.

A room-temperature redox molten salt for the study of electron transfers in semisolid media, based on combining bis(cyclopentadienyl)cobalt with oligomeric polyether counterions, [Cp2Co](MePEG350SO3), is reported. The transport properties of the new molten salt can be varied (plasticized) by varying the polyether content. The charge transport rate during voltammetric reduction of the ionically conductive [Cp2Co](MePEG350SO3) molten salt exceeds the actual physical diffusivity of [Cp2Co]+ because of rapid [Cp2Co](+/0) electron self-exchanges. The measured [Cp2Co](+/0) electron self-exchange rate constants (k(EX)) are proportional to the diffusion coefficients (D(CION)) of the counterions in the melt. The electron-transfer activation barrier energies are also close to those of ionic diffusion but are larger than those derived from optical intervalent charge-transfer results. Additionally, the [Cp2Co](+/0) rate constant results are close to those of dissimilar redox moieties in molten salts where D(CION) values are similar. All of these characteristics are consistent with the rates of electron transfers of [Cp2Co](+/0) (and the other donor-acceptor pairs) being controlled not by the intrinsic electron-transfer rates but by the rate of relaxation of the ion atmosphere around the reacting pair. In the low driving force regime of mixed-valent concentration gradients, the ion atmosphere relaxation is competitive with electron transfer. The results support the generality of the recently proposed model of ionic atmosphere relaxation control of electron transfers in ionically conductive, semisolid materials.

Journal Article↗
PubMed2005

Atmospheric chemistry of CH3CHF2 (HFC-152a): kinetics, mechanisms, and products of Cl atom- and OH radical-initiated oxidation in the presence and absence of NO(x).

Smog chamber/Fourier transform infrared (FTIR) and laser-induced fluorescence (LIF) spectroscopic techniques were used to study the atmospheric degradation of CH3CHF2. The kinetics and products of the Cl(2P(3/2)) (denoted Cl) atom- and the OH radical-initiated oxidation of CH3CHF2 in 700 Torr of air or N2; diluents at 295 +/- 2 K were studied using smog chamber/FTIR techniques. Relative rate methods were used to measure k(Cl + CH3CHF2) = (2.37 +/- 0.31) x 10(-13) and k(OH + CH3CHF2) = (3.08 +/- 0.62) x 10(-14) cm3 molecule(-1) s(-1). Reaction with Cl atoms gives CH3CF2 radicals in a yield of 99.2 +/- 0.1% and CH2CHF2 radicals in a yield of 0.8 +/- 0.1%. Reaction with OH radicals gives CH3CF2 radicals in a yield >75% and CH2CHF2 radicals in a yield <25%. Absolute rate data for the Cl reaction were measured using quantum-state selective LIF detection of Cl(2P(j)) atoms under pseudo-first-order conditions. The rate constant k(Cl + CH3CHF2) was determined to be (2.54 +/- 0.25) x 10(-13) cm3 molecule(-1) s(-1) by the LIF technique, in good agreement with the relative rate results. The removal rate of spin-orbit excited-state Cl(2P(1/2)) (denoted Cl) in collisions with CH3CHF2 was determined to be k(Cl + CH3CHF2) = (2.21 +/- 0.22) x 10(-10) cm3 molecule(-1) s(-1). The atmospheric photooxidation products were examined in the presence and absence of NO(x). In the absence of NO(x)(), the Cl atom-initiated oxidation of CH3CHF2 in air leads to formation of COF2 in a molar yield of 97 +/- 5%. In the presence of NO(x), the observed oxidation products include COF2 and CH3COF. As [NO] increases, the yield of COF2 decreases while the yield of CH3COF increases, reflecting a competition for CH3CF2O radicals. The simplest explanation for the observed dependence of the CH3COF yield on [NO(x)] is that the atmospheric degradation of CH3CF2H proceeds via OH radical attack to give CH3CF2 radicals which add O2 to give CH3CF2O2 radicals. Reaction of CH3CF2O2 radicals with NO gives a substantial fraction of chemically activated alkoxy radicals, [CH3CF2O]. In 1 atm of air, approximately 30% of the alkoxy radicals produced in the CH3CF2O2 + NO reaction possess sufficient internal excitation to undergo "prompt" (rate >10(10) s(-1)) decomposition to give CH3 radicals and COF2. The remaining approximately 70% become thermalized, CH3CF2O, and undergo decomposition more slowly at a rate of approximately 2 x 10(3) s(-1). At high concentrations (>50 mTorr), NO(x) is an efficient scavenger for CH3CF2O radicals leading to the formation of CH3COF and FNO.

Journal Article↗
PubMed2001

Ward atmosphere, client satisfaction, and client motivation in a psychiatric work rehabilitation unit.

This study investigated the ward atmosphere of a psychiatric work rehabilitation unit and its relationships to clients' satisfaction with the unit and client motivation, operationalised as proneness to set personal goals for their rehabilitation. The Community-oriented Programs Environment Scale was used and 52 clients participated. Their report of the ward atmosphere was in accordance with recommended levels on 5 sub-scales out of 10. A regression analysis revealed that optimal levels of order-and-organization and support were of importance for satisfaction with the unit. An optimal level of support was associated with a high rating of personal goals. This study added two therapeutically interesting factors-satisfaction and motivation-to the flora of factors that have been related to perceptions of the ward atmosphere.

Adult↗