Atmospheric Chemistry

ClNO2 over Europe_in press GRL

by Gavin Phillips

Critique of the tracer-tracer correlation technique and its potential to analyze polar ozone loss in chemistry-climate models

by Carsten Lemmen

Co-authored with Rolf Müller, Paul Konopka, and Martin Dameris

The tracer-tracer correlation technique (TRAC) has been widely employed to infer chemical ozone loss from... more The tracer-tracer correlation technique (TRAC) has been widely employed to infer chemical ozone loss from observations. Yet, its applicability to chemistry-climate model(CCM) data is disputed. Here, we report the successful application of TRAC on theresults of a CCM simulation. By comparing TRAC-calculated ozone loss to ozone lossderived with the passive ozone method in a chemistry transport model we differentiateeffects of internal mixing and cross vortex boundary mixing on a TRAC referencecorrelation. As a test case, we consider results of a cold Arctic winter/spring episode froman E39/C experiment, where typical features, for example, sufficient polar stratosphericcloud formation potential, denitrification and dehydration, and intermittent and finalstratospheric warming events, are simulated. We find that internal mixing does not impact the TRAC-derived reference correlation at all. Mixing across the vortex boundary wouldlead to an underestimation of ozone loss by 10% when calculated with TRAC. We provide arguments that TRAC is a consistent and conservative method to derive chemicalozone loss and can be used to extract its chemical signature also from CCM simulations. As a consequence, we will be able to provide a lower bound for chemical ozone loss for model simulations where a passive ozone tracer is not available

Size distribution of alkyl amines in continental particulate matter and their online detection in the gas and particle phase

by Trevor Vandenboer

Atmospheric Chemistry and Physics, 11, 4319 - 4332, 2011

An ion chromatographic method is described for the quantification of the simple alkyl amines: methylamine (MA),... more An ion chromatographic method is described for the quantification of the simple alkyl amines: methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA) and triethylamine (TEA), in the ambient atmosphere. Limits of detection (3) are in the tens of pmol range for all of these amines, and good resolution is achieved for all compounds except for TMA and DEA. The technique was applied to the analysis of time-integrated samples collected using a micro-orifice uniform deposition impactor (MOUDI) with ten stages for size resolution of particles with aerodynamic diameters between 56 nm and 18 m. In eight samples from urban and rural continental airmasses, the mass loading of amines consistently maximized on the stage corresponding to particles with aerodynamic diameters between 320 and 560 nm. The molar ratio of amines to ammonium (R3NH+/NH4+) in fine aerosol ranged between 0.005 and 0.2, and maximized for the smallest particle sizes. The size-dependence of the R3NH+/NH4+ ratio indicates differences in the relative importance of the processes leading to the incorporation of amines and ammonia into secondary particles. The technique was also used to make simultaneous hourly online measurements of amines in the gas phase and in fine particulate matter using an Ambient Ion Monitor Ion Chromatograph (AIM-IC). During a ten day campaign in downtown Toronto, DMA, TMA + DEA, and TEA were observed to range from below detection limit to 2.7 ppt in the gas phase. In the particle phase, MAH+ and TMAH+ + DEAH+ were observed to range from below detection limit up to 15 ng m-3. The presence of detectable levels of amines in the particle phase corresponded to periods with higher relative humidity and higher mass loadings of nitrate. While the hourly measurements made using the AIM-IC provide data that can be used the evaluate the application of gas-particle partitioning models to amines, the strong size-dependence of the R3NH+/NH4+ ratio indicates that using bulk measurements may not be appropriate.

Characterization and optimization of an online system for the simultaneous measurement of atmospheric water-soluble constituents in the gas and particle phases

by Trevor Vandenboer

Milos Z. Markovic, Trevor C. VandenBoer and Jennifer G. Murphy

DOI: 10.1039/c2em00004k

In this work we present the results of extensive characterization and optimization of the Ambient Ion Monitor-Ion... more In this work we present the results of extensive characterization and optimization of the Ambient Ion Monitor-Ion Chromatograph (AIM-IC) system, an instrument developed by URG Corp. and Dionex Inc. for simultaneous hourly measurements of the water-soluble chemical composition of atmospheric fine particulate matter (PM2.5) and associated precursor gases. The sampling assembly of the AIM-IC consists of an inertial particle size-selection assembly, a parallel-plate wet denuder (PPWD) for the
collection of soluble gases, and a particle supersaturation chamber (PSSC) for collection of particles, in series. The analytical assembly of the AIM-IC consists of anion and cation IC units. The system detection limits were determined to be 41 ppt, 5 ppt, and 65 ppt for gas phase NH3(g), SO2(g), andHNO3(g) and 29 ng m^
3, 3 ng m^3, and 45 ng m
^3 for particle phase NH4+, SO42-, and NO3- respectively. From external trace gas calibrations with permeation sources, we determined that the
AIM-IC is biased low for NH3(g) (11%), SO2(g) (19%), and HNO3(g) (12%). The collection efficiency of SO2(g) was found to strongly depend on the composition of the denuder solution and was found to be the most quantitative with 5 mM H2O2 solution for mixing ratios as high as 107 ppb. Using a cellulose
membrane in the PPWD, the system responded to changes in SO2(g) and HNO3(g) within an hour, however for NH3(g), the timescale can be closer to 20 h. With a nylon membrane, the instrument response time for NH3(g) was significantly improved, becoming comparable to the responses for SO2(g) and HNO3(g). Performance of the AIM-IC for collection and analysis of PM2.5 was evaluated by generating known number concentrations of ammonium sulfate and ammonium nitrate particles (with an aerodynamic diameter of 300 nm) under laboratory conditions and by comparing AIM-IC measurements to measurements from a collocated Aerosol Mass Spectrometer (AMS) during a fieldsampling campaign. On average, the AIM-IC and AMS measurements agreed well and captured rapid ambient concentration changes at the same time. In this work we also present a novel inlet configuration and plumbing for the AIM-IC which minimizes sampling inlet losses, reduces peak
smearing due to sample carryover, and allows for tower-height sampling from the base of a research tower.

Isocyanic acid in a global chemistry transport model: Tropospheric distribution, budget, and identification of regions with potential health impacts

by Trevor Vandenboer

Paul. J. Young, Louisa. K. Emmons, James M. Roberts, Jean–François Lamarque, Christine Wiedinmyer, Patrick Veres, and Trevor C. VandenBoer

Journal of Geophysical Research - Atmospheres
doi:10.1029/2011JD017393, in press.

http://www.dailycamera.com/ci_20534406

http://news.discovery.com/earth/billions-inhale-acid-from-fires-120501.html

This study uses a global chemical transport model to estimate the distribution of isocyanic acid (HNCO). HNCO is... more This study uses a global chemical transport model to estimate the distribution of isocyanic acid (HNCO). HNCO is toxic, and concentrations exceeding 1 ppbv have been suggested to have negative health effects. Based on fire studies, HNCO emissions were scaled to those of hydrogen cyanide (30%), resulting in yearly total emissions of 1.5 Tg for 2008, from both anthropogenic and biomass burning sources. Loss processes included heterogeneous uptake (pH dependent), dry deposition (like formic acid), and reaction with the OH radical (k = 1 x 10^-15 molecule^-1 cm^3 s^-1). Annual mean surface HNCO concentrations were highest over parts of China (maximum of 470 pptv), but episodic fire emissions gave much higher levels, exceeding 4 ppbv in tropical Africa and the Amazon, and exceeding 10 ppbv in Southeast Asia and Siberia. This suggests that large biomass burning events could result in deleterious health effects for populations in these regions. For the tropospheric budget, using the model-calculated pH the HNCO lifetime was 37 days, with the split between dry deposition and heterogeneous loss being 95%:5%. Fixing the heterogeneous loss rate at pH = 7 meant that this process dominated, accounting for ~70% of the total loss, giving a lifetime of 6 days, and resulting in upper tropospheric concentrations that were essentially zero. However, changing the pH does not notably
impact the high concentrations found in biomass burning regions. More observational data is needed to evaluate the model, as well as a better representation of the likely underestimated biofuel emissions, which could mean more populations exposed to
elevated HNCO concentrations.

Quantifying atmospheric transport, chemistry, and mixing using a new trajectory-box model and a global atmospheric-chemistry GCM

by Hella Riede

Verification of snowpack radiation transfer models using actinometry

by Gavin Phillips

Application of the EMEP Unified Model to the UK with a Horizontal Resolution of 5× 5 km 2

by Gavin Phillips

Effects of land use on surface–atmosphere exchanges of trace gases and energy in Borneo: comparing fluxes over oil palm plantations and a rainforest

by Gavin Phillips

Large estragole fluxes from oil palms in Borneo

by Gavin Phillips

Potential for photochemical ozone formation in the troposphere over the North Atlantic as derived from aircraft observations during ACSOE

by Gavin Phillips

Measurement of organic aerosol precursors over an oak forest

by Gavin Phillips

Micrometeorological measurements of anthropogenic VOC emissions from urban areas

by Gavin Phillips

ACCENT workshop abstract

Global modelling of H2 mixing ratios and isotopic compositions with the TM5 model

by Anneke M. Batenburg

Co-authored

Temporal and spatial variability of the stable isotopic composition of atmospheric molecular hydrogen: observations at six EUROHYDROS stations

by Anneke M. Batenburg

H2 vertical profiles in the continental boundary layer: measurements at the Cabauw tall tower in The Netherlands

by Anneke M. Batenburg

Co-authored

Nitrogen deposition to the eastern Atlantic Ocean. The importance of south‐easterly flow

by Sarah Cornell

Converting measured concentrations into fluxes and using estimates of biological productivity in the coastal waters of... more Converting measured concentrations into fluxes and using estimates of biological productivity in the coastal waters of the eastern Atlantic Ocean enables us to determine the role of the atmosphere as a source of biologically essential species, including nitrate and ammonium, to the marine biota. To understand the effects of the atmosphere as a source of nitrogen capable of promoting new production, we need to know both the seasonality of the input as well as the effects of extreme high deposition events which, while small in overall annual budget terms, maybe able to extend, or even promote, phytoplankton growth under nutrient depleted summer conditions. Aerosols and rainwater were collected at both Mace Head and at sea aboard RRS Challenger. Temporal patterns have been interpreted using airmass back trajectories which give the predicted air path prior to arrival at the sampling site. Low levels of both nitrate and ammonium are seen associated with marine westerly flow across the Atlantic and northerly air originating in the Arctic region. As expected, marine derived sodium, chloride, magnesium and seasalt sulphate are high during these periods. High concentration nitrate and ammonium events are seen associated with south-easterly flow where the airmass passes over the UK and northern Europe prior to arrival on the west coast of Ireland. In the polluted atmosphere, nitrate exists as nitric acid and as fine mode (<1 mm diameter) ammonium nitrate aerosol. In the coastal zone, nitric acid reacts with coarse mode seasalt aerosols to form coarse mode (>1 mm diameter) sodium nitrate:
HNO3(g)+NaCl(s) --> NaNO3(s)+HCl(g).
This seasalt displacement reaction not only enhances dry nitrate deposition through more efficient gravitational settling of large particles, but also increases the efficiency of precipitational scavenging via inertial impaction. By looking at the size distribution of nitrate, we can see evidence for the seasalt displacement reaction. Under the polluted south-easterly flow, ~40–60% of the nitrate occurs in the coarse mode fraction. Under clean marine conditions, the seasalt displacement reaction results in almost complete conversion of nitrate from the fine to the coarse aerosol mode. By converting measured wet and dry nitrate, ammonium and organic nitrogen concentrations into fluxes and comparing the data with estimates of biological productivity in the surface waters, our data suggest that ~30% of new production in eastern Atlantic surface waters off Ireland can be supported by atmospheric inputs in May 1997 and that most of the input occurs during short lived, high-concentration, south-easterly transport events.

Circadian Control of Isoprene Emissions From Oil Palm (Elaeis Guineensis)

by Claudia Vickers

The emission of isoprene from the biosphere to the atmosphere has a profound effect on the Earth's atmospheric system.... more The emission of isoprene from the biosphere to the atmosphere has a profound effect on the Earth's atmospheric system. Until now, it has been assumed that the primary short-term controls on isoprene emission are photosynthetically active radiation and temperature. Here we show that isoprene emissions from a tropical tree (oil palm, Elaeis guineensis) are under strong circadian control, and that the circadian clock is potentially able to gate light-induced isoprene emissions. These rhythms are robustly temperature compensated with isoprene emissions still under circadian control at 38°C. This is well beyond the acknowledged temperature range of all previously described circadian phenomena in plants. Furthermore, rhythmic expression of LHY/CCA1, a genetic component of the central clock in Arabidopsis thaliana, is still maintained at these elevated temperatures in oil palm. Maintenance of the CCA1/LHY-TOC1 molecular oscillator at these temperatures in oil palm allows for the possibility that this system is involved in the control of isoprene emission rhythms. This study contradicts the accepted theory that isoprene emissions are primarily light-induced.

1996 About the air pollution in the Bieszczady Mountains

by Marek Nowosad

Shape-Dependent Regularization for the Retrieval of Atmospheric State Parameter Profiles

by Joerg Steinwagner

Co-author: G. Schwarz

We present an adaptive regularization approach to retrieve vertical state parameter profiles from limb-sounding... more We present an adaptive regularization approach to retrieve vertical state parameter profiles from limb-sounding measurements with high accuracy. This is accomplished by introducing a dedicated regularization functional based on a reasonable assumption of the profile characteristics. The approach results in shape-dependent weighting during least-squares computations and relies on a Cholesky decomposition of a preselected LLT matrix. Our method is compared with established regularization functionals such as optimal estimation and Tikhonov with respect to errors and achievable height resolution. The results show an improved height resolution of the retrieved profiles together with a reduction of absolute and relative errors obtained by test-bed simulations.