Differences In Emission Rates Research Articles

Spruce bark beetles (Ips typographus) cause up to 700 times higher bark BVOC emission rates compared to healthy Norway spruce (Picea abies)

Abstract. Biogenic volatile organic compound (BVOC) emissions from trees subjected to biotic stress are higher compared to healthy trees, and they may also have a different compound composition. This in turn affects atmospheric chemistry and can lead to either positive or negative feedback to the climate. Climate change favors the abundance of the European spruce bark beetle (Ips typographus) which attacks the bark of Norway spruce (Picea abies) trees, causing induced BVOC emissions from the trees as a response to the insect stress. Here, results are reported from a study analyzing the difference in emission rates between healthy and bark-beetle-infested Norway spruce trees, changes in emission rates over time since the infestation started, and differences in emission rates from bark-beetle-drilled entry and exit holes. Bark chamber measurements on both healthy and infested trees were performed during the summer of 2019 at Hyltemossa and Norunda research stations in Sweden. The measurements showed that induced BVOC emissions following the bark beetle infestation were dominated by entry hole emissions in the early growing season and exit hole emissions in the later season. The results showed a significant difference in emission rates between healthy and infested trees during both seasons. The seasonal average standardized BVOC emission rate of healthy trees was 32 ± 52 µg m−2 h−1 (mean ± standard deviation), while the average standardized BVOC emission rates of infested trees were 6700 ± 6900 and 2000 ± 1300 µg m−2 h−1 during the early and late season respectively. BVOC emission rates were highest at the start of the infestation and decreased exponentially with time, showing induced emission rates for up to 1 year after which the emission rates were similar to those from healthy bark. Constitutive needle emission rates from healthy trees were found to be 11 times higher than bark emissions from healthy trees. However, when Norway spruce trees were infested, the bark emission rates were instead 6 to 20 times higher than the needle emissions, causing substantial increases in the total tree BVOC emission rate. This could lead to high impacts on atmospheric processes, specifically the formation of secondary organic aerosols, which have a higher yield from some monoterpene compounds, which increased from infested trees.

Road Grade Estimation Based on Power Demand Difference of Heavy-Duty Diesel Trucks for Emission Estimation

Road grades have significant impacts on the emissions of heavy-duty diesel trucks (HDDTs), even in the same operating mode. Existing gradient identification methods are time-consuming and difficult to conduct for entire road networks; moreover, few previous studies have considered uncertainty of HDDT emissions caused by various road grades. In this study, an estimation method for road grade was developed based on second-by-second field operating data, with noise reduction performed using the Kalman filter. The consistency and symmetry of the road grade calculated by the proposed method were then analyzed. Finally, differences in emission rate and emission factor for carbon dioxide (CO2), carbon monoxide (CO), total hydrocarbon (THC), and nitrogen oxides (NOx) under various grades were compared. The results indicated that the grade recognition results of each truck were consistent, with an average grade difference of 0.153%. Based on symmetry analysis of the estimation results in opposite directions, the two opposite road grades were found to have a strong negative correlation, and the average error of the grade was 0.125%. Pollutant results showed the emission rate of CO was most affected by grade, followed by NOx, and THC was the least affected. The emission factors of CO2, CO, THC, and NOx were found to increase by 32.4% to 82.8%, 75.6% to 198.4%, 19.9% to 39.9%, and 73.1% to 186.3%, respectively at 1.0%, 2.0%, and 3.0% gradients compared with 0.0% gradient. This study can improve the estimation accuracy for HDDT emissions, especially in areas with undulating terrain such as mountains and hills.

Characterization of PM10 Emission Rates from Roadways in a Metropolitan Area Using the SCAMPER Mobile Monitoring Approach

The SCAMPER mobile system for measuring PM10 emission rates from paved roads was used to characterize emission rates from a wide variety of roads in the Phoenix, AZ metropolitan area. Week-long sampling episodes were conducted in March, June, September, and December. A 180 km-long route was utilized and traveled a total of 18 times. PM10 emission rate measurements were made at 5-s resolution for over 3200 km of roads with a precision of approximately 25%. The PM10 emission rates varied by over two orders of magnitude and were generally low unless the road was impacted with dust deposited by activities such as construction, sand and gravel operations, agriculture, and vehicles traveling on or near unpaved shoulders and roads. The data were tabulated into averages for each of 67 segments that the route was divided into. The segment-averaged PM10 emission rates ranged from zero to 2 mg m−1, with an average of 0.079 mg m−1. There was no significant difference in emission rates between seasons. There was a major drop in emission rates over a weekend, when dust generation activities such as construction are expected to be much reduced. By Monday, the PM10 emission rates had risen to the levels of the previous Friday. This indicates that roads quickly reach an equilibrium PM10 generating potential.

Technical note: validation of the GreenFeed system for measuring enteric gas emissions from cattle.

There are knowledge gaps in animal agriculture on how to best mitigate greenhouse gas emissions while maintaining animal productivity. One reason for these gaps is the uncertainties associated with methods used to derive emission rates. This study compared emission rates of methane (CH4) and carbon dioxide (CO2) measured by a commercially available GreenFeed (GF) system with those from (1) a mass flow controller (MFC) that released known quantities of gas over time (i.e., emission rate) and (2) a respiration chamber (RC). The GF and MFC differed by only 1% for CH4 (P = 0.726) and 3% for CO2 (P = 0.013). The difference between the GF and RC was 1% (P = 0.019) for CH4 and 2% for CO2 (P = 0.007). Further investigation revealed that the difference in emission rate for CO2 was due to a small systematic offset error indicating a correction factor could be applied. We conclude that the GF system accurately estimated enteric CH4 and CO2 emission rates of cattle over a short measurement period, but additional factors would need to be considered in determining the 24-hr emission rate of an animal.

The spatial and temporal drivers of pCO2, pCH4 and gas transfer velocity within a subtropical estuary.

Large uncertainties remain in global estuarine CO2 and CH4 emissions estimates due to spatial heterogeneity, differences in methodologies and insufficient data at key locations. This study utilised novel techniques to integrate high-resolution temporal measurements of dissolved CO2 and CH4 and gas transfer velocity, within an urbanised subtropical estuary (Coffs Creek, Australia). An intensive four-station 25hr moving time series approach accounted for diurnal, tidal and spatial trends along an estuarine salinity gradient. Using 185 floating chamber measurements, results revealed major differences in emission rates over short distances. Average CO2 emission rates ranged from 16.7 to 84.4 mmol m−2 day−1 from lower to upper estuary respectively (averaged 49.0 mmol m−2 day−1). The CH4 emissions ranged from 38.8 to 193.4 μmol m−2 day−1 (averaged 115.0 μmol m−2 day−1), equating to 2.4% of the average CO2 emissions, when converted to global warming potential CO2 equivalent (over 100 years). Conservative mixing plots revealed a mid-estuary source of groundwater and porewater exchange that corresponded with a source of pCO2 and pCH4 in the mangrove lined portion of the estuary. Between the mouth and upper-estuary, a 230-fold change in gas transfer velocity (k600) (0.1–25.9 cm hr−1), 130-fold change in CO2 fluxes (1.6–202.6 mmol m−2 day−1) and 260-fold change of CH4 fluxes were observed (2.6–671.1 μmol m−2 day−1). Current velocity was the most important driver of k600 in the lower estuary (r2 = 0.37, p < 0.001) and a significant driver across the whole estuary (r2 = 0.77, p < 0.001). A comparison of measured emissions to existing empirical k models indicated empirical models were less effective at characterising emissions within different ecotypes because of changing physical drivers along the estuary. The kCO2 chemical enhancement may be significant, especially in low k settings such as upper estuaries. This study highlights the importance of characterizing distinct estuarine zones and accounting for spatio-temporal variability to reduce uncertainties of emissions estimates.

Altered volatile profile associated with precopulatory mate guarding attracts spider mite males.

Proximate factors affecting animal behavior include stimuli generated by conspecifics. In spider mites of the genus Tetranychus (Acari: Tetranychidae), males guard pre-reproductive quiescent females, because only the first mating results in fertilization. In a dual-choice experiment, more adult males of T. urticae were attracted to females guarded by a male than to solitary females. Because spider mites are known to perceive volatiles, we hypothesized that guarded and solitary females differ in the volatile blends emitted. To test this hypothesis, headspace volatiles of guarded females, solitary females, and solitary males were collected, respectively. GC/MS analysis detected octanal, methyl salicylate, ethyl 4-ethoxybenzoate, and methyl cis-dihydrojasmonate in all of the groups. Orthogonal Projection to Latent Structures Discriminant Analysis (OPLS-DA) of the blends clearly discriminated guarded females from solitary females, supporting our hypothesis. Individual compounds did not show significant difference in emission rates for guarded females vs. solitary females, suggesting that differences lay in the total blend composition. OPLS-DA did not discriminate between the blends emitted by guarded females and solitary males. In conclusion, the differences in the volatile blends are likely to mediate male discrimination between guarded and solitary females.

Emissions of nitrous oxide from the leaves of grasses

Nitrous oxide (N2O) emissions from pastoral agriculture are considered to originate from the soil as a consequence of microbial activity during soil nitrification and denitrification. However, recent studies have identified the plant canopy as a potentially significant source of N2O emissions to the atmosphere. Understanding the extent and mechanisms of plant emissions may provide new mitigation opportunities as current options only target soil microbial processes. We developed an experimental apparatus and protocol to partition N2O emissions between the leaves of grasses and the soil and measured emissions from ten common grass species found in New Zealand pastures. The chamber design enabled us to identify measurable changes in N2O concentration over a period of 1 h and to distinguish a range of emissions from 0.001 to 0.25 mg N2O-N/m2 leaf area/h. There was a 10-fold variation among species; Holcus lanataus, Lolium perenne and Paspalum dilatatum had the highest leaf N2O emissions and Poa annua the lowest. Grasses do emit N2O from their leaves and the rate that this occurs varies among grass species. The emission does not appear to arise from formation of N2O in plant leaves but more likely reflects transport of N2O from the soil. Differences in emission rates appear to arise from a plant influence on the rate of formation of N2O in the soil rather than the rate of transportation through the plant.

Exposures from Chrysotile‐Containing Joint Compound: Evaluation of New Model Relating Respirable Dust to Fiber Concentrations

The potential for fiber exposure during historical use of chrysotile-containing joint compounds (JCC) has been documented, but the published data are of limited use for reconstructing exposures and assessing worker risk. Consequently, fiber concentration distributions for workers sanding JCC were independently derived by applying a recently developed model based on published dust measurements from sanding modern-day (asbestos-free) joint compound and compared to fiber concentration distributions based on limited historical measurements. This new procedure relies on factors that account for (i) differences in emission rates between modern-day and JCC and (ii) the number of fibers (quantified by phase contrast microscopy [PCM]) per mass of dust generated by sanding JCC, as determined in a bench-scale chamber study using a recreated JCC, that convert respirable dust concentrations to fiber concentrations. Airborne respirable PCM-fiber concentration medians (and 95% confidence intervals) derived for output variables using the new procedure were 0.26 (0.039, 1.7) f/cm(3) and 0.078 (0.013, 0.47) f/cm(3) , and corresponding total fiber concentrations were 1.2 (0.17, 9.2) f/cm(3) and 0.37 (0.056, 2.5) f/cm(3) , in enclosed and nonenclosed environments, respectively. Corresponding estimates of respirable and total PCM fiber concentrations measured historically during sanding of asbestos-containing joint compound-adjusted for differences between peak and time-weighted average (TWA) concentrations and documented analytical preparation and sampling artifacts-were 0.15 (0.019, 0.95) f/cm(3) and 0.86 (0.11, 5.4) f/cm(3) , respectively. The PCM-fiber concentration distributions estimated using the new procedure bound the distribution estimated from adjusted TWA historical fiber measurements, suggesting reasonable consistency of these estimates taking into account uncertainties addressed in this study.

Measurements of nitrogen oxides from Hudson Bay: Implications for NO x release from snow and ice covered surfaces

Measurements of NO and NO 2 were made at a surface site (55.28 °N, 77.77 °W) near Kuujjuarapik, Canada during February and March 2008. NO x mixing ratios ranged from near zero to 350 pptv with emission from snow believed to be the dominant source. The amount of NO x was observed to be dependent on the terrain over which the airmass has passed before reaching the measurement site. The 24 h average NO x emission rates necessary to reproduce observations were calculated using a zero-dimensional box model giving rates ranging from 6.9 × 10 8 molecule cm −2 s −1 to 1.2 × 10 9 molecule cm −2 s −1 for trajectories over land and from 3.8 × 10 8 molecule cm −2 s −1 to 6.6 × 10 8 molecule cm −2 s −1 for trajectories over sea ice. These emissions are higher than those suggested by previous studies and indicate the importance of lower latitude snowpack emissions. The difference in emission rate for the two types of snow cover shows the importance of snow depth and underlying surface type for the emission potential of snow-covered areas.

NITROUS OXIDE EMISSION FROM FARM DAIRY EFFLUENT APPLICATION IN GRAZED GRASSLAND

Intensification in dairying and increased production of farm dairy effluent (FDE) has raised concerns about gaseous nitrogen (N) losses and their environmental implications. This study was undertaken to monitor changes in mineral-N and soil water-filled pore-space (WFPS) in relation to N20 emission from application of FDE to dairy-grazed pasture. Pasture was irrigated with FDE in September 2003 (first irrigation) and January 2004 (second irrigation), preceded by grazing events. The N20 emission rate increased after application of FDE. Total amounts of N20 emitted from FDE application for first and second irrigation were 2% and 4.9%, respectively, of the total N added through effluents. Difference in emission rates between the two irrigation events were attributed to difference in time lapse between the grazing event and FDE application. When FDE was applied immediately after grazing (second irrigation) higher emissions were observed.

Annual and seasonal changes in foliar terpene content and emission rates in Cistus albidus L. submitted to soil drought in Prades forest (Catalonia, NE Spain)

We measured the gas exchange and foliar terpene concentrations and terpene emission rates of Cistus albidus throughout the seasons of two annual periods (2003 and 2005) of contrasting precipitations (900 vs. 500 mm) and in response to experimental drought in a Mediterranean forest of southern Catalonia. C. albidus showed a typical seasonal oscillation of photosynthetic rates and stomatal conductance. Maximum photosynthetic activity appeared in the spring of the first year of the study and minimum ones in both summers. Net photosynthetic rates and stomatal conductance tended to decrease with drought treatment. In the first year, Cistus albidus presented maximum values of stored terpenes in autumn and winter and minimum values in spring and summer. Average concentrations in the first year were 154 and 96 μg g−1 dry matter (d.m.) for control and drought, respectively. Average concentrations in the second year were higher, 339 and 263 μg g−1 (d.m.) for control and drought, respectively. The most abundant terpene was zingiberene, followed by aromadendrene, germacrene, (−)-α-cedrene, and sesquiphellandrene. The drought treatment tended to decrease terpene content, but not significantly. Considering all the treatments together, total terpene emissions ranged between practically 0 (spring 2003) to 9 μg g−1 (d.m.) h−1 (winter 2003). In the second year, total terpene emission rates decreased 39% in control plants, and 29% in drought plants. Significant seasonal differences in emission rates were found. Total emission rates tended to be higher in the drought treatment, especially in spring and autumn. These results help for a better understanding of the behavior of plant volatiles in Mediterranean conditions interannualy and seasonally, an issue of great interest for forest flammability and atmospheric chemistry.

A Discussion on the Impact of CFC12 Emission Rate from XPS Insulation on Atmospheric Banks

This report presents new information regarding emissions of CFC12 used to make extruded polystyrene foam products. Earlier reports identified a significant difference in emission rates from extruded polystyrene foam that are used to estimate the amount of the chlorofluorocarbon yet to be released from these materials — the banked amount. Since the estimated atmospheric lifetime of CFC12 is ∼100 years, it is very important to use an accurate release rate from extruded polystyrene foam in actual use to corroborate laboratory measurements. This report will provide evidence that CFC12 is emitted from extruded polystyrene foam more than an order of magnitude slower than some earlier reported rates, resulting in a bank of CFC12, yet to be released from the foam, potentially larger than previously estimated.

Spatial modelling of nitrous oxide emissions at the national scale using soil, climate and land use information

AbstractNitrous oxide (N2O) is a powerful greenhouse gas. The UK government is committed to reducing all greenhouse gas emissions and is required to make an inventory of the sources and emissions of these gases. Here, we extend work from a pilot study at the catchment scale reported in an earlier paper. This paper reports on the upscaling measurements of emissions to derive annual emission rates for specific combinations of soil type, land management and fertiliser practices to the national scale. Digital soil, climate and land use maps were combined within Geographic Information Systems (GIS) software. Upscaling of field emissions measurements involves adjusting measured annual N2O emissions to fit combinations of crop growth cycles, soil wetness and the amount and timing of fertiliser applications. We have also taken account of the differences in emission rates from grazed pasture land due to differences in land management between land utilised for dairy production and land utilised for beef production. Calculated annual emission rates were then spatially scaled to derive national figures through the use of a GIS modelling framework, termed NitOx. The annual emission of N2O from Scotland was determined as approximately 6 000 000 kg N yr−1 (2.8 Mt carbon dioxide (CO2) equivalents) and compares favourably with other national scale estimates such as the IPCC (1997). The combination of animal grazing, high N inputs, climatic warmth and poorly drained soils means that the south west contributes significantly to the national total N2O emissions. Localised areas of high emission can also be identified, but identification could be improved by applying this modelling approach at a larger scale. It would be beneficial to target these areas with mitigation strategies.

The effect of flooding on the exchange of the volatile C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere

Abstract. The effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid in relation to assimilation and transpiration was investigated with 2–3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited measurable emissions of any of the compounds, but rather low deposition of acetaldehyde and acetic acid was observed instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid were only observed from the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning suggest that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted, though we can not totally exclude other production pathways. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1 for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates and a non-trivial loss of carbon to the atmosphere. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere.

Effects of elevated CO2 and temperature on monoterpene emission of Scots pine (Pinus sylvestris L.)

The aim of this study was to evaluate the long-term (5 years) effects of elevated CO2 concentration (doubling of ambient CO2 concentration) and temperature (2–6°C elevation) on the monoterpene emission of Scots pine (Pinus sylvestris L.) saplings (ca. 20 years old) grown in closed-top environmental chambers. The chamber treatments included: (1) ambient temperature and CO2, (2) ambient temperature and elevated CO2, (3) elevated temperature and ambient CO2, and (4) elevated temperature and elevated CO2. The variability of emissions during and after tree shoot growth was studied, and additionally the total cumulative emission of monoterpenes through a growing period (May–September) was estimated. When compared to the controls, the combination of elevated CO2 and temperature significantly increased normalized monoterpene emission rate for the whole growing period (+23%), whereas elevated CO2 had no significant effect (−4%), and elevated temperature even decreased (−41%) the emission rate. The increasing effect of the combination of elevated CO2 and temperature was strongest during shoot growth (+54%). After shoot growth, no significant differences in emission rate were found among the treatments. Emission modeling showed that the total amount of monoterpenes emitted from May to September was 2.38mggdw−1 in ambient conditions. The total emission in elevated CO2 was 5% greater and in elevated temperature 9% lesser than in ambient conditions. The combination of elevated CO2 and temperature increased the amount of emitted monoterpenes over the growing period by 126% compared to the total emission in ambient conditions.

P-Dichlorobenzene emission rates from moth repellents and leakage rates from cloth storage cases

Emission rates of p-dichlorobenzene (pDCB) from five kinds of commercially available moth repellents and leakage rates from six kinds of commercially available cloth storage cases were measured. The emission rates from moth repellents immediately after purchase (E(max)), which were obtained as the slope of the total emission amount vs. time elapsed, were 0.0033 to 0.035 g/h at 25 degrees C. Moth repellents from different manufacturers differed greatly in emission rates at 0.0033, 0.0060, and 0.011 g/h, even if the moth repellent pieces were of similar shape and initial weight. This is thought to be because emission rates depended on the diffusion resistance of the repellent packing material used by each manufacturer. Therefore, the manufacturer-specific apparent mass transfer coefficients (K) were calculated for each moth repellent from the measured emission rates and a calculated saturated concentration. The apparent mass transfer coefficient K and the concentration gradient between the in-case (inside a cloth storage case) bulk air and the air at the surface of a moth repellent (pDCB tablet) were used for the calculation of the general emission rates. The leakage rates, defined as the air-exchange rate for a cloth storage case, from six cloth storage cases ranged from 0.41 to 78/h. Despite the large difference (more than 100 times) in the leakage rates of the cloth storage cases, the differences in emission rates of pDCB from these cloth storage cases to the indoor environment were small (<30%). This is because the concentration gradients between the in-case bulk air and the air at the surface of a repellent piece were almost the same among the storage cases. This suggests that pDCB emissions from cloth storage cases into the indoor environment should be reduced by making the storage cases more tightly sealable so that the leakage rate is <0.01/h. The results of adsorption tests of pDCB onto woollen clothes showed that the adsorption of pDCB on the clothes was assumed to be very strong and the transfer between the gas phase and the cloth phase in the cloth storage case was assumed to be small. The use of pDCB provides benefits such as moth control and deodorizing, but on the other hand, poses potential risks to human health. There is a risk-benefit tradeoff, i.e. a tradeoff between risks of pDCB to human health and benefit of moth control effects. The pDCB concentration in the cloth storage case and in the indoor air can be estimated by using emission rates and the leakage rates obtained in this study. By comparing the concentration to the deterrent efficiency of pDCB, the risk for the use of pDCB moth repellents can be managed.

Isoprenoid emissions of trees in a tropical rainforest in Xishuangbanna, SW China

Isoprenoid emissions of eight tropical tree species of SE Asia were investigated using dynamic Teflon bag branch enclosures. Emission potentials of four species were considerably deviating from a previous report. Two species, Garcinia cowa and Celtis philippensis, emitted isoprene with standard emission factors, given as carbon on dry weight basis of 20.7 and 0.2 μ g g - 1 h - 1 , respectively, before the peak of the rainy season. After the peak of the rainy reason the standard emission changed to 17.5 and 0.7 μ g g - 1 h - 1 , respectively. The other six species emitted monoterpenes with low standard emission factors between < 0.1 and 0.5 μ g g - 1 h - 1 . Four out of five species investigated at two different times of the year showed seasonal differences in emission rates and composition. Total isoprenoid emissions were generally higher with new leaf flush than with aged leaves. Overall, the results suggest that better understanding of volatile organic compounds (VOC) emission from tropical species of SE Asia requires investigations that cover different seasons.

A comparative study of VOCs in Singapore and European office buildings

This study compares the characteristics of volatile organic compounds (VOCs) and the associated factors affecting them within European (EU) and Singapore buildings. Generally, concentrations of target VOCs determined in the two types of buildings were within health and comfort guidelines. This study found that concentrations of 2-methylpentane and n-heptane were significantly higher in the EU buildings, while those of n-tetradecane, 2-ethyl 1-hexanol, benzene, toluene, m/ p-xylene, benzaldehyde and naphthalene significantly higher in Singapore buildings. Area specific emission rates of the methylpentane isomers, n-heptane and isoprene were significantly higher in the EU buildings, while those of 2-ethyl 1-hexanol, benzene, toluene and naphthalene were significantly higher in Singapore buildings. Lower ventilation rates within Singapore buildings caused relatively higher concentrations of m/ p-xylenes and benzaldehyde despite no differences in emission rates between the two types of buildings. Elevated levels of 2-ethyl 1-hexanol in Singapore buildings are due to the higher air velocities and relative humidity indoors. There were no differences in 1,1,1-trichloroethane and 2-propanone levels, suggesting similar use of consumer products and occupant densities relating these two VOCs. Higher emission rates of methylpentane isomers and heptane were associated with the use of adhesives and solvents related to internal surfaces while higher emission rates for isoprene in the EU buildings were associated with environmental tobacco smoke (ETS). Higher levels of benzene, toluene and naphthalene in ETS-free Singapore buildings were associated with human-related activities.

Atmospheric gaseous mercury concentrations in New York State: relationships with meteorological data and other pollutants

Abstract Ambient vapor-phase mercury concentrations including total gaseous mercury (TGM) and reactive gaseous mercury (RGM) were measured at three locations in rural New York State: Potsdam, Stockton, and Sterling. The RGM concentrations (4.2±6.4, 5.7±9.2, 6.0±10.8 pg m−3 at the Potsdam, Stockton, and Sterling sites, respectively) were about 0.2–3% of the total gaseous phase mercury concentration (TGM: 1.84±1.24, 1.83±1.32, 3.02±2.14 ng m−3, respectively) at the three monitoring sites. Standard deviations of RGM concentrations indicate that their daily variation was larger than that of TGM at all sites. This larger variation is probably because RGM is influenced by local sources to a greater extent than elemental mercury, which makes up to majority of TGM. There was no significant correlation between ozone and mercury concentrations. However, there was a significant positive correlation between water vapor mixing ratio and elemental mercury concentrations, suggesting that reduction of Hg2+ to Hg0 occurred in liquid water contained in clouds and fogs near the three monitoring sites. TGM concentrations had a generally negative correlation with ambient temperature, whereas RGM concentrations had a positive relationship. The negative relationship between TGM and temperature may be due to seasonal differences in emission rates of coal-fired power plants (winter maximum) in the northern hemisphere. This assumption was supported by a positive correlation between TGM and sulfur concentration, one of the major pollutants emitted from coal-fired power plants.

Fragrance chemistry, nocturnal rhythms and pollination “syndromes” in Nicotiana

GC–MS analyses of nocturnal and diurnal floral volatiles from nine tobacco species ( Nicotiana; Solanaceae) resulted in the identification of 125 volatiles, including mono- and sesquiterpenoids, benzenoid and aliphatic alcohols, aldehydes and esters. Fragrance chemistry was species-specific during nocturnal emissions, whereas odors emitted diurnally were less distinct. All species emitted greater amounts of fragrance at night, regardless of pollinator affinity. However, these species differed markedly in odor complexity and emission rates, even among close relatives. Species-specific differences in emission rates per flower and per unit fresh or dry flower mass were significantly correlated; fragrance differences between species were not greatly affected by different forms of standardization. Flowers of hawkmoth-pollinated species emitted nitrogenous aldoximes and benzenoid esters on nocturnal rhythms. Four Nicotiana species in section Alatae sensu strictu have flowers that emit large amounts of 1,8 cineole, with smaller amounts of monoterpene hydrocarbons and α-terpineol on a nocturnal rhythm. This pattern suggests the activity of a single biosynthetic enzyme (1,8 cineole synthase) with major and minor products; however, several terpene synthase enzymes could contribute to total monoterpene emissions. Our analyses, combined with other studies of tobacco volatiles, suggest that phenotypic fragrance variation in Nicotiana is shaped by pollinator- and herbivore-mediated selection, biosynthetic pathway dynamics and shared evolutionary history.