Greenhouse gas emissions from penguin guanos and ornithogenic soils in coastal Antarctica: Effects of freezing–thawing cycles

In coastal Antarctica, freezing and thawing influence many physical, chemical and biological processes for ice-free tundra ecosystems, including the production of greenhouse gases (GHGs). In this study, penguin guanos and ornithogenic soil cores were collected from four penguin colonies and one seal colony in coastal Antarctica, and experimentally subjected to three freezing–thawing cycles (FTCs) under ambient air and under N₂. We investigated the effects of FTCs on the emissions of three GHGs including nitrous oxide (N₂O), carbon dioxide (CO₂) and methane (CH₄). The GHG emission rates were extremely low in frozen penguin guanos or ornithogenic soils. However, there was a fast increase in the emission rates of three GHGs following thawing. During FTCs, cumulative N₂O emissions from ornithogenic soils were greatly higher than those from penguin guanos under ambient air or under N₂. The highest N₂O cumulative emission of 138.24 μg N₂O–N kg^?1 was observed from seal colony soils. Cumulative CO₂ and CH₄ emissions from penguin guanos were one to three orders of magnitude higher than those from ornithogenic soils. The highest cumulative CO₂ (433.0 mgCO₂–C kg^?1) and CH₄ (2.9 mgCH₄–C kg^?1) emissions occurred in emperor penguin guanos. Penguin guano was a stronger emitter for CH₄ and CO₂ while ornithogenic soil was a stronger emitter for N₂O during FTCs. CO₂ and CH₄ fluxes had a correlation with total organic carbon (TOC) and soil/guano moisture (M_c) in penguin guanos and ornithogenic soils. The specific CO₂–C production rate (CO₂–C/TOC) indicated that the bioavailability of TOC was markedly larger in penguin guanos than in ornithogenic soils during FTCs. This study showed that FTC-released organic C and N from sea animal excreta may play a significant role in FTC-related GHG emissions, which may account for a large proportion of annual fluxes from tundra ecosystems in coastal Antarctica.     

Biomass consumption and CO2, CO and main hydrocarbon gas emissions in an Amazonian forest clearing fire

Biomass consumption and CO₂, CO and hydrocarbon gas emissions in an Amazonian forest clearing fire are presented and discussed. The experiment was conducted in the arc of deforestation, near the city of Alta Floresta, state of Mato Grosso, Brazil. The average carbon content of dry biomass was 48% and the estimated average moisture content of fresh biomass was 42% on wet weight basis. The fresh biomass and the amount of carbon on the ground before burning were estimated as 528 t ha^?1 and 147 t ha^?1, respectively. The overall biomass consumption for the experiment was estimated as 23.9%. A series of experiment in the same region resulted in average efficiency of 40% for areas of same size and 50% for larger areas. The lower efficiency obtained in the burn reported here occurred possibly due to rain before the experiment. Excess mixing ratios were measured for CO₂, CO, CH₄, C₂–C₃ aliphatic hydrocarbons, and PM_2.5. Excess mixing ratios of CH₄ and C₂–C₃ hydrocarbons were linearly correlated with those of CO. The average emission factors of CO₂, CO, CH₄, NMHC, and PM_2.5 were 1,599, 111.3, 9.2, 5.6, and 4.8 g kg^?1 of burned dry biomass, respectively. One hectare of burned forest released about 117,000 kg of CO₂, 8100 kg of CO, 675 kg of CH₄, 407 kg of NMHC and 354 kg of PM_2.5.     

Dissolved black carbon in grassland streams: Is there an effect of recent fire history?

While the existence of black carbon as part of dissolved organic matter (DOM) has been confirmed, quantitative determinations of dissolved black carbon (DBC) in freshwater ecosystem and information on factors controlling its concentration are scarce. In this study, stream surface water samples from a series of watersheds subject to different burn frequencies in Konza Prairie (Kansas, USA) were collected in order to determine if recent fire history has a noticeable effect on DBC concentration. The DBC levels detected ranged from 0.04 to 0.11 mg L^?1, accounting for ca. 3.32 ± 0.51% of dissolved organic carbon (DOC). No correlation was found between DBC concentration and neither fire frequency nor time since last burn. We suggest that limited DBC flux is related to high burning efficiency, possibly greater export during periods of high discharge and/or the continuous export of DBC over long time scales. A linear correlation between DOC and DBC concentrations was observed, suggesting the export mechanisms determining DOC and DBC concentrations are likely coupled. The potential influence of fire history was less than the influence of other factors controlling the DOC and DBC dynamics in this ecosystem. Assuming similar conditions and processes apply in grasslands elsewhere, extrapolation to a global scale would suggest a global grasslands flux of DBC on the order of 0.14 Mt carbon year^?1.     

The effects of evaporating essential oils on indoor air quality

Essential oils, predominantly comprised of a group of aromatic chemicals, have attracted increasing attention as they are introduced into indoor environments through various forms of consumer products via different venues. Our study aimed to characterize the profiles and concentrations of emitted volatile organic compounds (VOCs) when evaporating essential oils indoors. Three popular essential oils in the market, lavender, eucalyptus, and tea tree, based on a nation-wide questionnaire survey, were tested. Specific aromatic compounds of interest were sampled during evaporating the essential oils, and analyzed by GC-MS. Indoor carbon monoxide (CO), carbon dioxide (CO₂), total volatile organic compounds (TVOCs), and particulate matters (PM₁₀) were measured by real-time, continuous monitors, and duplicate samples for airborne fungi and bacteria were collected in different periods of the evaporation. Indoor CO (average concentration 1.48 vs. 0.47 ppm at test vs. background), CO₂ (543.21 vs. 435.47 ppm), and TVOCs (0.74 vs. 0.48 ppm) levels have increased significantly after evaporating essential oils, but not the PM₁₀ (2.45 vs. 2.42 ppm). The anti-microbial activity on airborne microbes, an effect claimed by the use of many essential oils, could only be found at the first 30–60 min after the evaporation began as the highest levels of volatile components in these essential oils appeared to emit into the air, especially in the case of tea tree oil. High emissions of linalool (0.092–0.787 mg m⁻³), eucalyptol (0.007–0.856 mg m⁻³), d-limonene (0.004–0.153 mg m⁻³), ρ-cymene (0.019–0.141 mg m⁻³), and terpinene-4-ol-1 (0.029–0.978 mg m⁻³), all from the family of terpenes, were observed, and warranted for further examination for their health implications, especially for their potential contribution to the increasing indoor levels of secondary pollutants such as formaldehyde and secondary organic aerosols (SOAs) in the presence of ozone.     

Contribution of carbonaceous material to cloud condensation nuclei concentrations in European background (Mt. Sonnblick) and urban (Vienna) aerosols

During four intensive measurement campaigns (two on Mt. Sonnblick, European background aerosol, and two in Vienna, urban aerosol), cloud condensation nuclei (CCN) were measured at supersaturations of 0.5%. Impactor measurements of the mass size distribution in the size range 0.1–10 μm were performed and later analyzed for Cl^-, NO^-₃, SO^2-₄, Na⁺, NH⁺₄, K⁺, Ca²⁺ and Mg²⁺ by ion chromatography, for total carbon (TC) using a combustion method, and for black carbon (BC) by an optical method (integrating sphere). Organic carbon (OC) was defined as the difference between TC (minus carbonate carbon) and BC. At all sites, the mass fraction of BC in the submicron aerosol was comparable (4–5%). CCN concentrations on Mt. Sonnblick were found to be 10–30% of those measured in Vienna, although high Mt. Sonnblick concentrations were comparable to low Vienna concentrations (around 800 cm^-3). The contribution of organic material was estimated from the mass concentrations of the chemical species sampled on the impactor stage with the lowest cut point (0.1–0.215 μm aerodynamic equivalent diameter). On Mt. Sonnblick, TC material contributed 11% to the total mass in fall 1995, and 67% in summer 1996, while the OC fraction was 6 and 61%. The combined electrolytes and mineral material contributed 18 and 16% in fall and summer. During the Vienna spring campaign, the contributions of OC and electrolytes to the total mass concentration in this size range were 48 and 36%, respectively.     

Dissolved organic carbon in rainwater: Glassware decontamination and sample preservation and volatile organic carbon

The efficiency of different methods for the decontamination of glassware used for the analysis of dissolved organic carbon (DOC) was tested using reported procedures as well as new ones proposed in this work. A Fenton solution bath (1.0 mmol L⁻¹ Fe²⁺ and 100 mmol L⁻¹ H₂O₂) for 1 h or for 30 min employing UV irradiation showed to combine simplicity, low cost and high efficiency. Using the optimized cleaning procedure, the DOC for stored UV-irradiated ultra-pure water reached concentrations below the limit of detection (0.19 μmol C L⁻¹). Filtered (0.7 μm) rain samples maintained the DOC integrity for at least 7 days when stored at 4 °C. The volatile organic carbon (VOC) fraction in the rain samples collected at two sites in São Paulo state (Brazil) ranged from 0% to 56% of their total DOC content. Although these high-VOC concentrations may be derived from the large use of ethanol fuel in Brazil, our results showed that when using the high-temperature catalytic oxidation technique, it is essential to measure DOC rather than non-purgeble organic carbon to estimate organic carbon, since rainwater composition can be quite variable, both geographically and temporally.     

Carbonaceous and inorganic composition in long-range transported aerosols over northern Japan: Implication for aging of water-soluble organic fraction

To better understand the influence of sources and atmospheric processing on aerosol chemical composition, we collected atmospheric particles in Sapporo, northern Japan during spring and early summer 2005 under the air mass transport conditions from Siberia, China and surrounding seas. The aerosols were analyzed for inorganic ions, organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), and the major water-soluble organic compound classes (i.e., dicarboxylic acids and sugars). SO₄^2? is the most abundant inorganic constituent (average 44% of the identified inorganic ion mass) followed by NH₄⁺ (21%) and NO₃^? (13%). Concentrations of OC, EC, and WSOC ranged from 2.0–16, 0.24–2.9, and 0.80–7.9 μg m^?3 with a mean of 7.4, 1.0, and 3.1 μg m^?3, respectively. High OC/EC ratios (range: 3.6–19, mean: 8.7) were obtained, however WSOC/OC ratios (0.23–0.69, 0.44) do not show any significant diurnal changes. These results suggest that the Sapporo aerosols were already aged, but were not seriously affected by local photochemical processes. Identified water-soluble organic compounds (diacids + sugars) account for <10% of WSOC. Based on some marker species and air mass back trajectory analyses, and using stable carbon isotopic compositions of shorter-chain diacids (i.e., C₂–C₄) as photochemical aging factor of organic aerosols, the present study suggests that a fraction of WSOC in OC is most likely influenced by aerosol aging, although the OC loading in aerosols may be more influenced by their sources and source regions.     

Production of carbon dioxide in a fattening pig house under field conditions. I. Exhalation by pigs

Exhalation of carbon dioxide (CO₂) by pigs was investigated under field conditions in a mechanically ventilated commercial fattening house. The tranquil CO₂ exhalation rate (TCER) by pigs was defined and methodology was developed to study it. The experiments were conducted by moving groups of pigs in and out of one of the compartments in the house and comparing differences of measured CO₂ production rates. The measured TCERs ranged from 41.5 to 73.9 g CO₂ h⁻¹ per pig for pigs from 32 to 105 kg. When pigs were very active, the CO₂ exhalation rate could be about 200% of the TCER but did not last for long time. A TCER mathematical model was developed based on 4 sets of experiments. It calculated the CO₂ exhalation by a pig at tranquil time as a function of its weight. Daily mean CO₂ exhalation rate (CER) by a pig was about 110% of the TCER. The TCER/CER model related the CO₂ exhalation to some aspects of pigs’ behaviours and was the first reported model developed with direct measurement of CO₂ production rates. Five models of CO₂ exhalation in available literature were reviewed and the CER model was compared with them. There was a clear disparity among these models. The average CO₂ exhalation rate calculated with the “Ouwerkerk Model” was about three times as that obtained by the “Anderson Model” for pigs from 35 to 120 kg. The CER model produced the same CO₂ exhalation rate as the “Ouwerkerk Model” for a pig of 35 kg and a close rate to the “Klooster Model” for a pig of 85 kg.     

Characteristics influencing the variability of urban CO2 fluxes in Melbourne,Australia

Urban areas are significant contributors to global carbon dioxide emissions. Vehicle emissions and other anthropogenic related activities are a frequent source of CO₂ to the atmosphere, contributing to global warming. Micrometeorological techniques used for observations in Northern Hemisphere cities have found that urban CO₂ fluxes are consistently a source. This study investigates CO₂ fluxes in an Australian city, adding to the global database of CO₂ fluxes in a bid to aid in future development of planning policies concerning reductions in CO₂ emissions. Using the eddy covariance approach, fluxes of CO₂ were measured at a suburban site (Preston) in Melbourne, Australia from February 2004 to June 2005 to investigate temporal variability. A second site (Surrey Hills) with differing surface characteristics (in particular, greater vegetation cover) was also established in Melbourne and ran simultaneously for 6 months (February 2004–July 2004). Results showed that both sites were a net source of CO₂ to the atmosphere. Diurnal patterns of fluxes were largely influenced by traffic volumes, with two distinct peaks occurring at the morning and evening traffic peak hours, with the winter morning peak averaging 10.9 μmol m⁻² s⁻¹ at Preston. Summer time fluxes were lower than during winter due to greater vegetative influence and reduced natural gas combustion. Vegetation limited the source of CO₂ in the afternoon, yet was not enough to combat the strong local anthropogenic emissions. Surrey Hills showed higher fluxes of CO₂ despite greater vegetation cover because of higher local traffic volumes. Annual emissions from Preston were estimated at 84.9 t CO₂ ha⁻¹ yr⁻¹. Magnitudes and patterns of suburban CO₂ fluxes in Melbourne were similar to those observed in Northern Hemisphere suburban areas.     

Production of carbon dioxide in a fattening pig house under field conditions. II. Release from the manure

Carbon dioxide (CO₂) release from manure was investigated under field conditions in one of the compartments in a mechanically ventilated fattening pig house. The potential of CO₂ release was tested in the emptied compartment by imposing high ventilation rate and measuring CO₂ concentrations in the incoming and exhaust air. When the compartment was filled with pigs, a model of tranquil CO₂ exhalation rate (TCER) was used to estimate the part of CO₂ produced by animals, in addition to the measurement of CO₂ concentrations and ventilation rate. Useful data were extracted from 135 days of continuously measured field data obtained when the housing system was in steady-state. The CO₂ release per m² of pit surface was 18.4 and 25.8 g h⁻¹ m⁻² in the emptied pig compartment during the impulse and pulse ventilation rate tests, respectively. It ranged from 1.1 and 116.7 g h⁻¹ m⁻² and averaged 42.1 g h⁻¹ m⁻² during the 135-day continuous field measurement. In 128 of the 135 days when the compartment was filled with pigs, the mean CO₂ release from the manure reached an average of 37.5% of the TCER by pigs, instead of less than 5% believed by many researchers. The maximum CO₂ release rate in 2-h steady-state measurements was 94% of the TCER by pigs. This research demonstrated that, in the previous knowledge, there might be a serious underestimation of the CO₂ release from the manure in pig houses. The total pig weight, manure temperature and ventilation rate were found the most important variables related to the CO₂ release. A mathematical model was developed to estimate the CO₂ release as a function of these three variables with R²=0.525.     

Seasonal soil and leaf CO2 exchange rates in a Mediterranean holm oak forest and their responses to drought conditions

We measured the soil and leaf CO₂ exchange in Quercus ilex and Phillyrea latifolia seasonally throughout the year in a representative site of the Mediterranean region, a natural holm oak forest growing in the Prades Mountains in southeastern Catalonia. In the wet seasons (spring and autumn), we experimentally decreased soil moisture by 30%, by excluding rainfall and water runoff in 12 plots, 1×10 m, and left 12 further plots as controls. Our aim was to predict the response of these gas exchanges to the drought forecasted for the next decades for this region by GCM and ecophysiological models.Annual average soil CO₂ exchange rate was 2.27±0.27 μmol CO₂ m⁻² s⁻¹. Annual average leaf CO₂ exchange rates were 8±1 and 5±1 μmol m⁻² s⁻¹ in Q. ilex and P. latifolia, respectively. Soil respiration rates in control treatments followed a seasonal pattern similar to photosynthetic activity. They reached maximum values in spring and autumn (2.5–3.8 μmol m⁻² s⁻¹ soil CO₂ emission rates and 7–15 μmol m⁻² s⁻¹ net photosynthetic rates) and minimum values (almost 0 for both variables) in summer, showing that soil moisture was the most important factor driving the soil microbial activity and the photosynthetic activity of plants. In autumn, drought treatment strongly decreased net photosynthesis rates and stomatal conductance of Q. ilex by 44% and 53%, respectively. Soil respiration was also reduced by 43% under drought treatment in the wet seasons. In summer there were larger soil CO₂ emissions in drought plots than in control plots, probably driven by autotrophic (roots) metabolism. The results indicate that leaf and soil CO₂ exchange may be strongly reduced (by ca. 44%) by the predicted decreases of soil water availability in the next decades. Long-term studies are needed to confirm these predictions or to find out possible acclimation of those processes.     

Continuous observations of carbon dioxide at Mace Head,Ireland from 1995 to 1999 and its net European ecosystem exchange

A 5-yr record of continuous high-frequency carbon dioxide CO₂ observations over the 1995–1999 period for the Mace Head Atmospheric Research Station has been examined to reveal a complex interplay between local- and regional-scale sources and sinks. During the winter months, an additional CO₂ source, over and above fossil fuel combustion, is required to support the observed concentrations of CO₂ in European regionally polluted air masses. During the summer months, an additional CO₂ sink is required. Over the entire study period, the additional net European ecosystem exchange source–sink required is –0.36±0.4 Gtonne C yr⁻¹.     

Characterization of emissions from portable household combustion devices: particle size distributions,emission rates and factors,and potential exposures

A series of source tests were conducted to characterize emissions of particulate matter (PM), carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), and total hydrocarbon (THC ) from five types of portable combustion devices. Tested combustion devices included a kerosene lamp, an oil lamp, a kerosene space heater, a portable gas range, and four unscented candles. All tests were conducted either in a well-mixed chamber or a well-mixed room, which enables us to determine emission rates and emission factors using a single-compartment mass balance model. Particle mass concentrations and number concentrations were measured using a nephelometric particle monitor and an eight-channel optical particle counter, respectively. Real-time CO concentrations were measured with an electrochemical sensor CO monitor. CO₂, CH₄, and THC were measured using a GC-FID technique. The results indicate that all particles emitted during steady burning in each of the tested devices were smaller than 1.0 μm in diameter with the vast majority in the range between 0.1 and 0.3 μm. The PM mass emission rates and emission factors for the tested devices ranged from 5.6±0.1 to 142.3±40.8 mg h⁻¹ and from 0.35±0.06 to 9.04±4.0 mg g⁻¹, respectively. The CO emission rates and emission factors ranged from 4.7±3.0 to 226.7±100 mg h⁻¹ and from 0.25±0.12 to 1.56±0.7 mg g⁻¹, respectively. The CO₂ emission rates and emission factors ranged from 5500±700 to 210,000±90,000 mg h⁻¹ and from 387±45 to 1689±640 mg g⁻¹, respectively. The contributions of CH₄ and THC to emission inventories are expected to be insignificant due both to the small emission factors and to the relatively small quantity of fuel consumed by these portable devices. An exposure scenario analysis indicates that every-day use of the kerosene lamp in a village house can generate fine PM exposures easily exceeding the US promulgated NAAQS for PM_2.5.     

Combined measurements of thermal emission and solar absorption of atmospheric carbon monoxide

A new technique using ground-based FTIR spectroscopy has been developed to investigate the vertical distribution of carbon monoxide in the atmosphere. Complementary measurements of atmospheric emission and solar absorption over the infrared region have been carried out sequentially to determine the amounts of carbon monoxide in the lower and upper atmosphere. The method is based on the fact that the two techniques of remote sensing are inherently sensitive to the carbon monoxide amount in different regions of the atmosphere. The measurements have been made under summertime conditions at a northern mid-latitude rural setting with a relatively pollution-free atmosphere. The total zenith column amount was determined to be 1.84×10¹⁸ molecules cm^-2±7% which was based on the solar absorption measurement. From the analysis of the thermal emission spectrum, which is sensitive to carbon monoxide only in the lower troposphere, a zenith column amount of 1.01×10¹⁸ molecules cm^-2±10% was estimated for the first 4.8 km of the atmosphere; this corresponded to an average carbon monoxide mixing ratio of 118 ppbv. Comparing the results of the two measurements indicated that a zenith column amount 8.3×10¹⁷ molecules cm^-2±20%, or an average mixing ratio of 66 ppbv, was present in the free troposphere above an altitude of 4.8 km. These results are consistent with those reported for other northern mid-latitude locations using various in situ and solar absorption measuring techniques.     

Measurement of gas-phase total peroxides at the summit of Mount Tai in China

Measurement of ambient gas-phase total peroxides was performed at the summit of Mount Tai (Mt. Tai, 1534 m above sea level) in central-eastern China during March 22–April 24 and June 16–July 20, 2007. The hourly averaged concentration of peroxides was 0.17 ppbv (± 0.16 ppbv, maximum: 1.28 ppbv) and 0.55 ppbv (± 0.67 ppbv, maximum: 3.55 ppbv) in the spring and summer campaigns, respectively. The average concentration of peroxides at Mt. Tai, which is in a heavily polluted region, was much lower than hydrogen peroxide measurements made at some rural mountain sites, suggesting that significant removal processes took place in this region. An examination of diurnal variation and a correlation analysis suggest that these removal processes could include chemical suppression of peroxide production due to the scavenging of peroxy and hydroxy radicals by high NO_x, wet removal by clouds/fogs rich in dissolved sulfur dioxide which reacts quickly with peroxides, and photolysis. These sinks competed with photochemical sources of peroxides, resulting in different mean concentrations and diurnal pattern of peroxides in the spring and summer. A principal component analysis was conducted to quantify the major processes that influenced the variation of peroxide concentrations. This analysis shows that in the spring photochemical production was an important source of peroxides, and the major sink was scavenging during upslope transport of polluted and humid air from the lower part of the planetary boundary layer (PBL) and wet removal by synoptic scale clouds. During the summer, highly polluted PBL air (with high NO_x) was often associated with very low peroxides due to the chemical suppression of HO₂ by high NO_x and wet-removal by clouds/fogs in this sulfur-rich atmosphere, especially during the daytime. Higher concentrations of peroxides, which often appeared at mid-nighttime, were mainly associated with subsidence of air masses containing relatively lower concentrations of NO_y.     

Air–land exchanges of CO2, CH4 and N2O measured by FTIR spectrometry and micrometeorological techniques

Micrometeorological flux-gradient and nocturnal boundary layer methods were combined with Fourier transform infrared (FTIR) spectroscopy for high-precision trace gas analysis to measure fluxes of the trace gases CO₂, CH₄ and N₂O between agricultural fields and the atmosphere. The FTIR measurements were fully automated and routinely obtained a precision of 0.1–0.2% for several weeks during a measurement campaign in October 1995. In flux-gradient measurements, vertical profiles of the trace gases were measured every 30 min from the ground to 22 m. When combined with independent micrometeorological measurements of water vapour fluxes, trace gas fluxes from the underlying surface could be determined. In the nocturnal boundary layer method the rate of change in mass storage in the 0–22 m layer was combined with fluxes measured at 22 m to estimate surface fluxes. Daytime fluxes for CO₂ were −0.78±0.40 (1σ) mg CO₂ m⁻² s⁻¹. Daytime fluxes of N₂O and CH₄ were very small and difficult to measure reliably using the flux-gradient technique, despite the high precision of the concentration measurements. Mean daytime flux for N₂O was 17±48 ng N m⁻² s⁻¹, while the corresponding flux for CH₄ was 47±410 ng CH₄ m⁻² s⁻¹. The mean nighttime flux of CO₂ estimated using the nocturnal boundary layer method was +0.15±0.05 mg CO₂ m⁻² s⁻¹, in good agreement with chamber measurements of respiration rates. Nighttime fluxes of CH₄ and N₂O from the nocturnal boundary layer method were 109±69 ng CH₄ m⁻² s⁻¹ and 2±3.2 ng N m⁻² s⁻¹, respectively, in good agreement with chamber measurements and inventory estimates based on the sheep and cattle stocking rates in the region. The suitability of FTIR-based methods for long term monitoring of spatially and temporally averaged flux measurements is discussed.     

Chemical composition of aerosols during a major biomass burning episode over northern Europe in spring 2006: Experimental and modelling assessments

The long-range transported smokes emitted by biomass burning had a strong impact on the PM_2.5 mass concentrations in Helsinki over the 12 days period in April and May 2006. To characterize aerosols during this period, the real-time measurements were done for PM_2.5, PM_2.5–10, common ions and black carbon. Moreover, the 24-h PM₁ filter samples were analysed for organic and elemental carbon (OC and EC), water-soluble organic carbon (WSOC), ions and levoglucosan. The Finnish emergency and air quality modelling system SILAM was used for the forecast of the PM_2.5 concentration generated by biomass burning. According to the real-time PM_2.5 data, the investigated period was divided into four types of PM situations: episode 1 (EPI-1; 25–29 April), episode 2 (EPI-2; 1–5 May), episode 3 (EPI-3; 5–6 May) and a reference period (REF; 24 March–24 April). EPI-3 included a local warehouse fire and therefore it is discussed separately. The PM₁ mass concentrations of biomass burning tracers—levoglucosan, potassium and oxalate—increased during the two long-range transport episodes (EPI-1 and EPI-2). The most substantial difference between the episodes was exhibited by the sulphate concentration, which was 4.9 (±1.4) μg m⁻³ in EPI-2 but only 2.4 (±0.31) μg m⁻³ in EPI-1 being close to that of REF (1.8±0.54 μg m⁻³). The concentration of particulate organic matter in PM₁ was clearly higher during EPI-1 (11±3.3 μg m⁻³) and EPI-2 (9.7±4.0 μg m⁻³) than REF (1.3±0.45 μg m⁻³). The long-range transported smoke had only a minor impact on the WSOC-to-OC ratio. According to the model simulations, MODIS detected the fires that caused the first set of concentration peaks (EPI-1) and the local warehouse fire (EPI-3), but missed the second one (EPI-2) probably due to dense frontal clouds.     

Investigations of emissions and heterogeneous formation of HONO in a road traffic tunnel

Simultaneous measurements of nitrous acid (HONO) and nitrogen dioxide (NO₂) using a differential optical absorption spectroscopy system, nitrogen oxide (NO) by an in situ chemiluminescence analyser and carbon dioxide (CO₂) by a gas chromatographic technique were carried out in the Wuppertal Kiesbergtunnel. At high traffic density HONO concentrations of up to 45 ppbV were observed. However, at low traffic density unexpectedly high HONO concentrations of up to 10 ppbV were measured caused by heterogeneous HONO formation on the tunnel walls. In addition to the tunnel campaigns, emission measurements of HONO, NO₂, NO and CO₂ from different single vehicles (a truck, a diesel and a gasoline passenger car) were also performed. For the correction of the HONO emission data, the heterogeneous HONO formation on the tunnel walls was quantified by two different approaches (a) in different NO₂ emission experiments in the tunnel without traffic and (b) on tunnel wall residue in the laboratory. The HONO concentration corrected for heterogeneous formation on the tunnel walls, in relation to the CO₂ concentration can be used to estimate the amount of HONO, which is directly emitted from the vehicle fleet. From the measured data, emission ratios (e.g. HONO/NO_x) and emission indices (e.g. mg HONO kg⁻¹ fuel) were calculated. The calculated emission index of 88±18 mg HONO kg⁻¹ fuel allows an estimation of the HONO emission rates from traffic into the atmosphere. Furthermore, the heterogeneous formation of HONO from NO₂ on freshly emitted exhaust particles is discussed.     

NOX fluxes from three kinds of agricultural lands in the Yangtze Delta,China

Static chamber method was adopted to measure the surface exchanges of NO and NO₂ between three kinds of agricultural lands and the atmosphere during spring–summer period in the Yangtze Delta, China. The average NO fluxes were 20.9, 27.4 and 21.4 ng N m⁻² s⁻¹, respectively, for cabbage (CA, cultivation of celery occurred along with cabbage), potato (PO) and soybean (SY) fields. The average NO₂ fluxes were −1.12, 0.93 and −0.68 ng N m⁻² s⁻¹, respectively, for the cabbage, potato and soybean fields. Apparently, negative linear correlation was found between the NO₂ fluxes from the CK plot (tilled conventionally but did not cultivate any seeds) and its ambient concentrations, and the compensation point was calculated to be 0.92 ppbv. The total NO emission from the vegetable lands and SY land in this region during spring–summer period was roughly estimated to be 15.9 Gg N, which accounted for about 11.2% of the estimated value of total NO emissions in the July of 1999 from Chinese agricultural fields.     

Influence of competing inorganic cations on the ion exchange equilibrium of the monovalent organic cation metoprolol on natural sediment

The aim of this study was to systematically investigate the influence of the mono- and divalent inorganic ions Na⁺ and Ca²⁺ on the sorption behavior of the monovalent organic cation metoprolol on a natural sandy sediment at pH = 7. Isotherms for the beta-blocker metoprolol were obtained by sediment–water batch tests over a wide concentration range (1–100 000 μg L^?1). Concentrations of the competing inorganic ions were varied within freshwater relevant ranges. Data fitted well with the Freundlich sorption model and resulted in very similar Freundlich exponents (n = 0.9), indicating slightly non-linear behavior. Results show that the influence of Ca²⁺ compared to Na⁺ is more pronounced. A logarithmic correlation between the Freundlich coefficient K_Fr and the concentration or activity of the competing inorganic ions was found allowing the prediction of metoprolol sorption on the investigated sediment at different electrolyte concentrations. Additionally, the organic carbon of the sediment was completely removed for investigating the influence of organic matter on the sorption of metoprolol. The comparison between the experiments with and without organic carbon removal revealed no significant contribution of the organic carbon fraction (0.1%) to the sorption of metoprolol on the in this study investigated sediment. Results of this study will contribute to the development of predictive models for the transport of organic cations in the subsurface.