Using a novel experimental technique, based on proton transfer reaction mass spectrometry, from measurements of emissions from laboratory scale biomass burning experiments, we have estimated the ...source strengths of several potential HOx producing gases: formaldehyde, acetaldehyde, methanol and acetone. The derived global average emissions are 5–13; 3.8–10; 1.5‐4; 2.3‐6.1 Tg y−1, respectively. The resulting global average HOx production from photochemical decay of these gases is 3 × 109 molecules cm−2 s−1. Although relatively small in a global context, these emissions are significant for the photochemistry in fresh fire plumes. From our measurements are also estimated global source strengths from biomass burning for CH3CN and HCN of 0.4‐1.0; 0.2‐0.6 Tg y−1 respectively. The biomass burning emissions of CH3CN may well dominate the global source of this compound, which thus might well be a unique tracer for biomass burning. Some discrepancies between experimental studies must, however, be resolved.
Characteristic vegetation and biofuels in major ecosystems of southern Africa were sampled during summer and autumn 2000 and burned under semicontrolled conditions. Elemental compositions of fuels ...and ash and emissions of CO2, CO, CH3COOH, HCOOH, NOX, NH3, HONO, HNO3, HCl, total volatile inorganic Cl and Br, SO2 and particulate C, N, and major ions were measured. Modified combustion efficiencies (MCEs, median = 0.94) were similar to those of ambient fires. Elemental emissions factors (EFel) for CH3COOH were inversely correlated with MCEs; EFels for heading and mixed grass fires were higher than those for backing fires of comparable MCEs. NOX, NH3, HONO, and particulate N accounted for a median of 22% of emitted N; HNO3 emissions were insignificant. Grass fires with the highest EFels for NH3 corresponded to MCEs in the range of 0.93; grass fires with higher and low MCEs exhibited lower EFels. NH3 emissions for most fuels were poorly correlated with fuel N. Most Cl and Br in fuel was emitted during combustion (median for each = 73%). Inorganic gases and particulate ions accounted for medians of 53% and 30% of emitted Cl and Br, respectively. About half of volatile inorganic Cl was HCl indicating significant emissions of other gaseous inorganic Cl species. Most fuel S (median = 76%) was emitted during combustion; SO2 and particulate SO42− accounted for about half the flux. Mobilization of P by fire (median emission = 82%) implies large nutrient losses from burned regions and potentially important exogenous sources of fertilization for downwind ecosystems.
The isotopic composition of carbon monoxide (13C, 14C, 18O) and methane (13C, D) was measured on air samples collected between Vladivostok and Moscow using the Trans‐Siberian railroad during August ...1996. Apart from short term fluctuations in the direct vicinity of sources, continuous measurements of CO and CH4 showed sustained, elevated mixing ratios over several hundreds of kilometers indicating the large scale influencing of traversed air masses by significant sources. Persistent, enhanced CH4 levels were found over the west Siberian lowlands concurrent with significantly depleted δ13C and δD values. The derived isotopic signature of the CH4 source (δ13C = −62.5±4.7‰ V‐PDB; δD = −311±14‰ V‐SMOW) clearly indicates the dominance of biogenic CH4, with the west Siberian wetlands being the most likely candidate. A second major feature in the data set is the enormous enhancement of CO (up to 1500 nmol/mol) east of Chita, extending over a 2000 km section along the river Amur. The 14CO measurements and back trajectory analyses identify biomass burning as the origin of the highly elevated CO. This is further supported by the δ18O(CO) and the δ13C/δD signature of the accompanying moderate CH4 enhancement.
Biomass burning is a primary source of many trace substances that are important in atmospheric chemistry1-6. More than 80% of the world's biomass burning takes place in the tropics3 as a result of ...savanna fires, forest-clearing activity, and the burning of agricultural waste and wood. Here we report results from laboratory studies on the emission of nitrogen-containing compounds from the burning of dry vegetation. We find that the emission rates of NO,, HCN and CH3CN are sufficient to contribute significantly to the global atmospheric budget of the compounds. Furthermore, possibly up to half of the biomass nitrogen can be converted to molecular nitrogen, N2, leading to an estimated annual loss of 12-28 x 1012 g of biomass nitrogen ('pyrodenitrification'), equal to -9-20% of the estimated global rate of terrestrial nitrogen fixation.
Using the CARIBIC Boeing 767 aircraft, a suite of trace gases and aerosols was measured between Germany and the Maldives in June 2000 at altitudes between 9.4 and 10 km. In the extratropics, the ...flight track was located in the tropopause region. A large variability of trace gases and ultrafine aerosol concentrations was observed while the aircraft intercepted air masses from the upper troposphere and the lowermost stratosphere, as well as outflow of deep convection. The correlations of alkanes (C2–C5) observed in the nonconvective areas point to relatively rapid mixing across the tropopause within about a day. Unusually high mixing ratios of short‐lived alkanes (C4–C6) in the convective areas indicate rapid transport of boundary layer air masses to cruising altitude. Using the ratios of the mixing ratios of alkanes (C3–C5) observed in the convective and nonconvective areas, we estimate the age of air masses in the tropopause region to be 24(±6) days for this event. This timescale is similar to that of vertical transport within the troposphere. Altogether our observations provide further evidence that the extratropical tropopause is often not a very effective mixing barrier.
Three types of reference simulations, as recommended by the Chemistry–Climate Model Initiative (CCMI), have been performed with version 2.51 of the European Centre for Medium-Range Weather Forecasts ...– Hamburg (ECHAM)/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model: hindcast simulations (1950–2011), hindcast simulations with specified dynamics (1979–2013), i.e. nudged towards ERA-Interim reanalysis data, and combined hindcast and projection simulations (1950–2100). The manuscript summarizes the updates of the model system and details the different model set-ups used, including the on-line calculated diagnostics. Simulations have been performed with two different nudging set-ups, with and without interactive tropospheric aerosol, and with and without a coupled ocean model. Two different vertical resolutions have been applied. The on-line calculated sources and sinks of reactive species are quantified and a first evaluation of the simulation results from a global perspective is provided as a quality check of the data. The focus is on the intercomparison of the different model set-ups. The simulation data will become publicly available via CCMI and the Climate and Environmental Retrieval and Archive (CERA) database of the German Climate Computing Centre (DKRZ). This manuscript is intended to serve as an extensive reference for further analyses of the Earth System Chemistry integrated Modelling (ESCiMo) simulations.
The chemical composition of the surface boundary layer over the Eurasian continent is still an area of high uncertainty. In the framework of the Trans‐Siberian Observations Into the Chemistry of the ...Atmosphere (TROICA) project, measurements of O3, NO, NO2, CO, CO2, CH4, 222Rn, J(NO2), and black carbon aerosol were carried out on the Trans‐Siberian railroad during June–July 1999. Boundary layer data over more than 16,000 km, from Kirov (∼58°N, 49°E; 972 km east of Moscow) to Khabarovsk (∼48°N, 135°E) and back to Moscow, were obtained without significant contamination, emphasizing the potential of using the Trans‐Siberian railroad system for atmospheric measurements. The 222Rn and CO2 concentrations were determined for the first time using our laboratory wagon. The diurnal variations of these gases and of CH4 due to micrometeorological conditions, as well as their dependence on various soil sources and vegetation types, were used to estimate ecosystem fluxes of CO2 and CH4. The highest soil flux of CH4 was 70 ± 35 μ mol m−2 h−1 for the wet habitats of the West Siberian lowlands, and the lowest CH4 flux was 3.2 ± 1.6 μ mol m−2 h−1 for drier habitats of eastern Siberia. Although the wet tundra emissions found between 67° and 77°N are higher than in comparable environments at much lower latitudes Christensen et al., 1995, boreal wetlands in Siberia at 50°–60°N represent a very important player in the global methane budget. The CO2 density fluxes exhibited the opposite to CH4 fluxes tendency. Ozone mixing ratios varied from a few nmol/mol during nighttime inversions to more than 60 nmol/mol during the day. These values were generally higher than during the 1996 summer campaign (TROICA 2). CH4 and CO levels followed the pattern observed during TROICA 2; elevated levels of CH4 with a mean mixing ratio of 1.97 ± 0.009 μmol/mol were found over the West Siberian lowlands, decreasing to 1.88 ± 0.13 μmol/mol toward East Siberia. Conversely, while background CO levels of the West Siberian wetlands were generally below 140 nmol/mol, high CO concentrations, once even exceeding 2 μmol/mol, were registered east of Chita (∼52°N, 113°E), as a consequence of forest and other vegetation fires, which significantly affect the chemical composition of the air over parts of Russia.
Simultaneous measurements of O3, CO, and ultrafine aerosol particles (UFP), conducted on board of a Boeing 767‐ER passenger aircraft flying from Sri Lanka to Germany (project CARIBIC), are used to ...study two‐way cross‐tropopause mixing near a subtropical tropopause fold. On the equatorward side of the fold, downward mixing of stratospheric air into the upper troposphere is identified by enhanced concentrations of O3 and 14CO. Very high UFP number concentrations of up to 1.5×104 cm−3 (STP) were encountered inside the poleward half of the fold. This accumulation of small particles is explained by recent extensive aerosol nucleation, most likely triggered by the mixing of stratospheric air with tropospheric air injected into the fold. Further, nine particle formation events were observed outside the fold which are attributed to isolated cells of deep convection and to rising air parcels under cyclonic conditions that mix with surrounding air. In the upper troposphere O3 and CO were found to be correlated with high ΔO3/ΔCO ratios of 0.6 to 1.5. In the fold the correlation was strongly negative with ΔO3/ΔCO; = −3.5; but the high CO mixing ratios of 100 ppb at O3 mixing ratios of 250 ppb point to earlier injection of tropospheric air, in agreement with the UFP measurements.
An airfreight container with automated instruments for measurement of atmospheric gases and trace compounds was operated on a monthly basis onboard a Boeing 767-300 ER of LTU International Airways ...during long-distance flights from 1997 to 2002 (CARIBIC, Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container, http://www.caribic-atmospheric.com). Subsequently a more advanced system has been developed, using a larger capacity container with additional equipment and an improved inlet system. CARIBIC phase #2 was implemented on a new long-range aircraft type Airbus A340-600 of the Lufthansa German Airlines (Star Alliance) in December 2004, creating a powerful flying observatory. The instrument package comprises detectors for the measurement of O3, total and gaseous H2O, NO and NOy, CO, CO2, O2, Hg, and number concentrations of sub-micrometer particles (>4 nm, >12 nm, and >18 nm diameter). Furthermore, an optical particle counter (OPC) and a proton transfer mass spectrometer (PTR-MS) are incorporated. Aerosol samples are collected for analysis of elemental composition and particle morphology after flight. Air samples are taken in glass containers for laboratory analyses of hydrocarbons, halocarbons and greenhouse gases (including isotopic composition of CO2) in several laboratories. Absorption tubes collect oxygenated volatile organic compounds. Three differential optical absorption spectrometers (DOAS) with their telescopes mounted in the inlet system measure atmospheric trace gases such as BrO, HONO, and NO2. A video camera mounted in the inlet provides information about clouds along the flight track. The flying observatory, its equipment and examples of measurement results are reported.
Simultaneous measurements of O
3
, CO, and ultrafine aerosol particles (UFP), conducted on board of a Boeing 767‐ER passenger aircraft flying from Sri Lanka to Germany (project CARIBIC), are used to ...study two‐way cross‐tropopause mixing near a subtropical tropopause fold. On the equatorward side of the fold, downward mixing of stratospheric air into the upper troposphere is identified by enhanced concentrations of O
3
and
14
CO. Very high UFP number concentrations of up to 1.5×10
4
cm
−3
(STP) were encountered inside the poleward half of the fold. This accumulation of small particles is explained by recent extensive aerosol nucleation, most likely triggered by the mixing of stratospheric air with tropospheric air injected into the fold. Further, nine particle formation events were observed outside the fold which are attributed to isolated cells of deep convection and to rising air parcels under cyclonic conditions that mix with surrounding air. In the upper troposphere O
3
and CO were found to be correlated with high ΔO
3
/ΔCO ratios of 0.6 to 1.5. In the fold the correlation was strongly negative with ΔO
3
/ΔCO; = −3.5; but the high CO mixing ratios of 100 ppb at O
3
mixing ratios of 250 ppb point to earlier injection of tropospheric air, in agreement with the UFP measurements.
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