Hasil untuk "Earthwork. Foundations"

S. Khanal, M. Toohey, A. Bourassa et al.

<p>The Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instrument on the SCISAT satellite provides aerosol extinction measurements in multiple solar wavelength bands. In this study, we evaluate the quality and utility of MAESTRO version 3.13 stratospheric aerosol extinction retrievals, from February 2004–February 2021, through comparison with measurements from other satellite instruments. Despite significant scatter in the MAESTRO data, we find that gridded median MAESTRO aerosol extinctions and stratospheric aerosol optical depth (SAOD) values are generally in good agreement with those from other instruments during volcanically quiescent periods. After volcanic eruptions and wildfire injections, gridded median MAESTRO extinction and SAOD are well correlated with other measurement sets but generally biased low by 40 %–80 %. The Ångström exponent (AE), which can provide information on aerosol particle size, is derived from the MAESTRO spectral extinction measurements in the lowermost stratosphere, showing perturbations after volcanic eruptions qualitatively similar to those from the Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) for the eruptions of Ambae (2018) and Ulawun (2019). Differences in AE anomalies after the 2019 extratropical Raikoke eruption may be due to the different spatiotemporal sampling of the two instruments. Furthermore, we introduce a method to adjust MAESTRO extinction data based on comparison with extinction measurements from SAGE III/ISS during the period from June 2017–February 2021, resulting in improved comparison during volcanically active periods. Our work suggests that empirical bias correction may enhance the utility of MAESTRO aerosol extinction data, which can make it a useful complement to existing satellite records, especially when multi-wavelength solar occultation data from other instruments are unavailable.</p>

Mingliang Pan, Hanling Sun

B. A. Löw, R. Kleinschek, V. Enders et al.

<p>Mapping the greenhouse gases (GHGs) carbon dioxide (CO<span class="inline-formula">₂</span>) and methane (CH<span class="inline-formula">₄</span>) above source regions such as urban areas can deliver insights into the distribution and dynamics of local emission patterns. Here, we present the prototype development and an initial performance evaluation of a portable spectrometer that allows for measuring CO<span class="inline-formula">₂</span> and CH<span class="inline-formula">₄</span> concentrations integrated along a long (<span class="inline-formula">&gt;10</span> <span class="inline-formula">km</span>) horizontal path component through the atmospheric boundary layer above a target region. To this end, the spectrometer is positioned at an elevated site from which it points downward at reflection targets in the region, collecting the reflected sunlight at shallow viewing angles. The path-integrated CO<span class="inline-formula">₂</span> and CH<span class="inline-formula">₄</span> concentrations are inferred from the absorption fingerprint in the shortwave–infrared (SWIR) spectral range. While mimicking the concept of the stationary California Laboratory for Atmospheric Remote Sensing – Fourier Transform Spectrometer (CLARS-FTS) in Los Angeles, our portable setup requires minimal infrastructure and is straightforward to duplicate and to operate in various locations.</p> <p>For performance evaluation, we deployed the instrument, termed EM27/SCA, side by side with the CLARS-FTS at the Mt. Wilson Observatory (1670 m a.s.l.) above Los Angeles for a 1-month period in April/May 2022. We determined the relative precision of the retrieved slant column densities (SCDs) for urban reflection targets to be 0.36 %–0.55 % for O<span class="inline-formula">₂</span>, CO<span class="inline-formula">₂</span> and CH<span class="inline-formula">₄</span>, where O<span class="inline-formula">₂</span> is relevant for light path estimation. For the partial vertical column (VCD) below instrument level, which is the quantity carrying emission information, the propagated precision errors amount to 0.75 %–2 % for the three gases depending on the distance to the reflection target and solar zenith angle. The comparison to simultaneous CLARS-FTS measurements shows good consistency, but the observed diurnal patterns highlight the need to take light scattering into account to enable detection of emission patterns.</p>

M. Rauber, M. Rauber, G. Salazar et al.

<p>Radiocarbon (<span class="inline-formula">¹⁴</span>C) analysis of carbonaceous aerosols is used for source apportionment, separating the carbon content into fossil vs. non-fossil origin, and is particularly useful when applied to subfractions of total carbon (TC), i.e. elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC), and water-insoluble OC (WINSOC). However, this requires an unbiased physical separation of these fractions, which is difficult to achieve. Separation of EC from OC using thermal–optical analysis (TOA) can cause EC loss during the OC removal step and form artificial EC from pyrolysis of OC (i.e. so-called charring), both distorting the <span class="inline-formula">¹⁴</span>C analysis of EC. Previous work has shown that water extraction reduces charring. Here, we apply a new combination of a WSOC extraction and <span class="inline-formula">¹⁴</span>C analysis method with an optimised <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">OC</mi><mo>/</mo><mi mathvariant="normal">EC</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="40pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="580ada1a61f0f73a9255ab81c518e127"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-825-2023-ie00006.svg" width="40pt" height="14pt" src="amt-16-825-2023-ie00006.png"/></svg:svg></span></span> separation that is coupled with a novel approach of thermal-desorption modelling for compensation of EC losses. As water-soluble components promote the formation of pyrolytic carbon, water extraction was used to minimise the charring artefact of EC and the eluate subjected to chemical wet oxidation to CO<span class="inline-formula">₂</span> before direct <span class="inline-formula">¹⁴</span>C analysis in a gas-accepting accelerator mass spectrometer (AMS). This approach was applied to 13 aerosol filter samples collected at the Arctic Zeppelin Observatory (Svalbard) in 2017 and 2018, covering all seasons, which bear challenges for a simplified <span class="inline-formula">¹⁴</span>C source apportionment due to their low loading and the large portion of pyrolysable species. Our approach provided a mean EC yield of <span class="inline-formula">0.87±0.07</span> and reduced the charring to 6.5 % of the recovered EC amounts. The mean fraction modern (<span class="inline-formula"><i>F</i>¹⁴</span>C) over all seasons was <span class="inline-formula">0.85±0.17</span> for TC; <span class="inline-formula">0.61±0.17</span> and <span class="inline-formula">0.66±0.16</span> for EC before and after correction with the thermal-desorption model, respectively; and <span class="inline-formula">0.81±0.20</span> for WSOC.</p>

S. Tian, S. Tian, K. Zu et al.

<p>In the last few decades, various techniques, including spectroscopic, mass spectrometric, chemiluminescence and wet chemical methods, have been developed and applied for the detection of gaseous ammonia (NH<span class="inline-formula">₃</span>). We developed an online NH<span class="inline-formula">₃</span> monitoring system – salicylic acid derivatization reaction and long-path absorption photometer (SAC-LOPAP) – based on a selective colorimetric reaction to form a highly absorbing reaction product and a LOPAP, which could run stably for a long time and be applied to the continuous online measurement of low concentrations of ambient NH<span class="inline-formula">₃</span> by optimizing the reaction conditions, adding a constant-temperature module and liquid flow controller. The detection limit reached with this instrument was 40.5 parts per trillion (ppt) with a stripping liquid flow rate of 0.49 mL min<span class="inline-formula">⁻¹</span> and a gas sample flow rate of 0.70 L min<span class="inline-formula">⁻¹</span>. An inter-comparison of our system with a commercial Picarro G2103 analyzer (Picarro, USA) in Beijing was presented, and the results showed that the two instruments had a good correlation with a slope of 1.00 and an <span class="inline-formula"><i>R</i>²</span> of 0.96, indicating that the SAC-LOPAP instrument involved in this study could be used for the accurate measurement of NH<span class="inline-formula">₃</span>.</p>

J. Gorroño, D. J. Varon, I. Irakulis-Loitxate et al.

<p>The use of satellite instruments to detect and quantify methane emissions from fossil fuel production activities is highly beneficial to support climate change mitigation. Different hyperspectral and multispectral satellite sensors have recently shown potential to detect and quantify point-source emissions from space. The Sentinel-2 (S2) mission, despite its limited spectral design, supports the detection of large emissions with global coverage and high revisit frequency thanks to coarse spectral coverage of methane absorption lines in the shortwave infrared. Validation of S2 methane retrieval algorithms is instrumental in accelerating the development of a systematic and global monitoring system for methane point sources. Here, we develop a benchmarking framework for such validation. We first develop a methodology to generate simulated S2 datasets including methane point-source plumes. These benchmark datasets have been created for scenes in three oil and gas basins (Hassi Messaoud, Algeria; Korpeje, Turkmenistan; Permian Basin, USA) under different scene heterogeneity conditions and for simulated methane plumes with different spatial distributions. We use the simulated methane plumes to validate the retrieval for different flux rate levels and define a minimum detection threshold for each case study. The results suggest that for homogeneous and temporally invariant surfaces, the detection limit of the proposed S2 methane retrieval ranges from 1000 to 2000 kg h<span class="inline-formula">⁻¹</span>, whereas for areas with large surface heterogeneity and temporal variations, the retrieval can only detect plumes in excess of 500 kg h<span class="inline-formula">⁻¹</span>. The different sources of uncertainty in the flux rate estimates have also been examined. Dominant quantification errors are either wind-related or plume mask-related, depending on the surface type. Uncertainty in wind speed, both in the 10 m wind (<span class="inline-formula"><i>U</i>₁₀</span>) and in mapping <span class="inline-formula"><i>U</i>₁₀</span> to the effective wind (<span class="inline-formula"><i>U</i>_eff</span>) driving plume transport, is the dominant source of error for quantifying individual plumes in homogeneous scenes. For heterogeneous and temporally variant scenes, the surface structure underlying the methane plume affects the plume masking and can become a dominant source of uncertainty.</p>

F. Liefhebber, S. Lammens, P. W. G. Brussee et al.

<p>Now that the Earth has been monitored by satellites for more than 40 years, Earth observation images can be used to study how the Earth system behaves over extended periods. Such long-term studies require the combination of data from multiple instruments, with the earliest datasets being of particular importance in establishing a baseline for trend analysis. As the quality of these earlier datasets is often lower, careful quality control is essential, but the sheer size of these image sets makes an inspection by hand impracticable. Therefore, one needs to resort to automatic methods to inspect these Earth observation images for anomalies. In this paper, we describe the design of a system that performs an automatic anomaly analysis on Earth observation images, in particular the Meteosat First Generation measurements. The design of this system is based on a preliminary analysis of the typical anomalies that can be found in the dataset. This preliminary analysis was conducted by hand on a representative subset and resulted in a finite list of anomalies that needed to be detected in the whole dataset. The automated anomaly detection system employs a dedicated detection algorithm for each of these anomalies. The result is a system with a high probability of detection and low false alarm rate. Furthermore, most of these algorithms are able to pinpoint the anomalies to the specific pixels affected in the image, allowing the maximum use of the data available.</p>

Timothy P. Melchert

L. Skochko, A. Shabaltun

The influence of the order of construction of houses on the formation of the stress-strain state of the system "foundation-foundation-above-ground structures" is investigated For this purpose, several options for setting tasks for the phased construction of multi-section building sections are considered. With this in mind, it should be noted that the construction of each subsequent section has an impact on the built entirely or partially adjacent section. That is why this effect should be investigated to predict how serious this impact may be, and to draw appropriate constructive decisions. Thus, the main objectives of the study are: Creation of SEM without taking into account the stages of construction of the house; Calculation of a house with a phased loading of 5 floors. Taking into account changes in the order of construction of sections; Formation of SEM taking into account the sequence of erection of sections without including the sequence of erection of floors within the boundaries of the current section; Research of the impact of the calculation of sections of a multi-section building without and taking into account the summary of subsequent sections. The research of the impact of the sequence of construction and installation of the object will allow us to assess the stress-strain scheme at all stages of construction, so changes in the behavior of the scheme will be recorded at all stages of construction specified by the designers. To do this, the change in the stress-strain state (VAT) of the system "foundation - foundations - above-ground structures" must be modeled with different options for stages of construction, taking into account the real parameters of the soil base and so on. The interaction of piles in different zones of sections, the work of grids in the foundations of high-rise buildings are considered. The research was carried out with the help of numerical modeling of the system "foundation - foundations - aboveground constructions". The redistribution of forces in the piles depending on the formulation of problems on the stages of construction of sections and design parameters (location of piles in characteristic zones, the influence of the stiffness of the aboveground part on the redistribution of forces). Characteristic zones in the foundation are distinguished: they are central, lateral, angular and especially at the joints of adjacent sections. The redistribution of efforts between piles and a grid is revealed.

Zied Kammoun, Mohamed Fourati, Hichem Smaoui

C. Beisbart

D. Weaver, D. Weaver, K. Strong et al.

<p>Improving measurements of water vapour in the upper troposphere and lower stratosphere (UTLS) is a priority for the atmospheric science community. In this work, UTLS water vapour profiles derived from Atmospheric Chemistry Experiment (ACE) satellite measurements are assessed with coincident ground-based measurements taken at a high Arctic observatory at Eureka, Nunavut, Canada. Additional comparisons to satellite measurements taken by the Atmospheric Infrared Sounder (AIRS), Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), Microwave Limb Sounder (MLS), Scanning Imaging Absorption Spectrometer for Atmospheric CHartography (SCIAMACHY), and Tropospheric Emission Spectrometer (TES) are included to put the ACE Fourier transform spectrometer (ACE-FTS) and ACE Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) results in context.</p> <p>Measurements of water vapour profiles at Eureka are made using a Bruker 125HR solar absorption Fourier transform infrared spectrometer at the Polar Environment Atmospheric Research Laboratory (PEARL) and radiosondes launched from the Eureka Weather Station. Radiosonde measurements used in this study were processed with software developed by the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN) to account for known biases and calculate uncertainties in a well-documented and consistent manner.</p> <p>ACE-FTS measurements were within 11&thinsp;ppmv (parts per million by volume; 13&thinsp;%) of 125HR measurements between 6 and 14&thinsp;km. Between 8 and 14&thinsp;km ACE-FTS profiles showed a small wet bias of approximately 8&thinsp;% relative to the 125HR. ACE-FTS water vapour profiles had mean differences of 13&thinsp;ppmv (32&thinsp;%) or better when compared to coincident radiosonde profiles at altitudes between 6 and 14&thinsp;km; mean differences were within 6&thinsp;ppmv (12&thinsp;%) between 7 and 11&thinsp;km. ACE-MAESTRO profiles showed a small dry bias relative to the 125HR of approximately 7&thinsp;% between 6 and 9&thinsp;km and 10&thinsp;% between 10 and 14&thinsp;km. ACE-MAESTRO profiles agreed within 30&thinsp;ppmv (36&thinsp;%) of the radiosondes between 7 and 14&thinsp;km. ACE-FTS and ACE-MAESTRO comparison results show closer agreement with the radiosondes and PEARL 125HR overall than other satellite datasets – except<span id="page4040"/> for AIRS. Close agreement was observed between AIRS and the 125HR and radiosonde measurements, with mean differences within 5&thinsp;% and correlation coefficients above 0.83 in the troposphere between 1 and 7&thinsp;km.</p> <p>Comparisons to MLS at altitudes around 10&thinsp;km showed a dry bias, e.g. mean differences between MLS and radiosondes were <span class="inline-formula">−25.6</span>&thinsp;%. SCIAMACHY comparisons were very limited due to minimal overlap between the vertical extent of the measurements. TES had no temporal overlap with the radiosonde dataset used in this study. Comparisons between TES and the 125HR showed a wet bias of approximately 25&thinsp;% in the UTLS and mean differences within 14&thinsp;% below 5&thinsp;km.</p>

M. Reggente, A. M. Dillner, S. Takahama

<p>Peak fitting (PF) and partial least squares (PLS) regression have been independently developed for estimation of functional groups (FGs) from Fourier transform infrared (FTIR) spectra of ambient aerosol collected on Teflon filters. PF is a model that quantifies the functional group composition of the ambient samples by fitting individual Gaussian line shapes to the aerosol spectra. PLS is a data-driven, statistical model calibrated to laboratory standards of relevant compounds and then extrapolated to ambient spectra. In this work, we compare the FG quantification using the most widely used implementations of PF and PLS, including their model parameters, and also perform a comparison when the underlying laboratory standards and spectral processing are harmonized. We evaluate the quantification of organic FGs (alcohol <span class="inline-formula">COH</span>, carboxylic <span class="inline-formula">COOH</span>, alkane CH, carbonyl <span class="inline-formula">CO</span>) and ammonium, using external measurements (organic carbon (OC) measured by thermal optical reflectance (TOR) and ammonium by balance of sulfate and nitrate measured by ion chromatography). We evaluate our predictions using 794 samples collected in the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network (USA) in 2011 and 238 laboratory standards from Ruthenburg et al. (2014) (available at <a href="https://doi.org/10.1016/j.atmosenv.2013.12.034">https://doi.org/10.1016/j.atmosenv.2013.12.034</a>). Each model shows different biases. Overall, estimates of OC by FTIR show high correlation with TOR OC. However, PLS applied to unprocessed (raw spectra) appears to underpredict oxygenated functional groups in rural samples, while other models appear to underestimate aliphatic CH bonds and OC in urban samples. It is possible to adjust model parameters (absorption coefficients for PF and number of latent variables for PLS) within limits consistent with calibration data to reduce these biases, but this analysis reveals that further progress in parameter selection is required. In addition, we find that the influence of scattering and anomalous transmittance of infrared in coarse particle samples can lead to predictions of OC by FTIR which are inconsistent with TOR OC. We also find through several means that most of the quantified carbonyl is likely associated with carboxylic groups rather than ketones or esters. In evaluating state-of-the-art methods for FG abundance by FTIR, we suggest directions for future research.</p>

A. Lavi, A. Lavi, M. P. Vermeuel et al.

Benzene cluster cations are a sensitive and selective reagent ion for chemical ionization of select biogenic volatile organic compounds. We have previously reported the sensitivity of a field deployable chemical ionization time-of-flight mass spectrometer (CI-ToFMS), using benzene cluster cation ion chemistry, for detection of dimethyl sulfide, isoprene and <i>α</i>-pinene. Here, we present laboratory measurements of the sensitivity of the same instrument to a series of terpenes, including isoprene, <i>α</i>-pinene, <i>β</i>-pinene, <i>D</i>-limonene, ocimene, <i>β</i>-myrcene, farnesene, <i>α</i>-humulene, <i>β</i>-caryophyllene, and isolongifolene at atmospherically relevant mixing ratios (&lt; 100 pptv). In addition, we determine the dependence of CI-ToFMS sensitivity on the reagent ion neutral delivery concentration and water vapor concentration. We show that isoprene is primarily detected as an adduct (C₅H₈  ⋅  C₆H₆⁺) with a sensitivity ranging between 4 and 10 ncps ppt⁻¹, which depends strongly on the reagent ion precursor concentration, de-clustering voltages, and specific humidity (SH). Monoterpenes are detected primarily as the molecular ion (C₁₀H₁₆⁺) with an average sensitivity, across the five measured compounds, of 14 ± 3 ncps ppt⁻¹ for SH between 7 and 14 g kg⁻¹, typical of the boreal forest during summer. Sesquiterpenes are detected primarily as the molecular ion (C₁₅H₂₄⁺) with an average sensitivity, across the four measured compounds, of 9.6 ± 2.3 ncps ppt⁻¹, that is also independent of specific humidity. Comparable sensitivities across broad classes of terpenes (e.g., monoterpenes and sesquiterpenes), coupled to the limited dependence on specific humidity, suggest that benzene cluster cation CI-ToFMS is suitable for field studies of biosphere–atmosphere interactions.

M. Höpfner, T. Deshler, M. Pitts et al.

<p>A global data set of vertical profiles of polar stratospheric cloud (PSC) volume density has been derived from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) space-borne infrared limb measurements between 2002 and 2012. To develop a well characterized and efficient retrieval scheme, systematic tests based on limb-radiance simulations for PSCs from in situ balloon observations have been performed. The finally selected wavenumber range was 831–832.5&thinsp;cm⁻¹. Optical constants of nitric acid trihydrate (NAT) have been used to derive maximum and minimum profiles of volume density which are compatible with MIPAS observations under the assumption of small, non-scattering and larger, scattering PSC particles. These max/min profiles deviate from their mean value at each altitude by about 40&thinsp;%–45&thinsp;%, which is attributed as the maximum systematic error of the retrieval. Further, the retrieved volume density profiles are characterized by a random error due to instrumental noise of 0.02–0.05&thinsp;µm³ cm⁻³, a detection limit of about 0.1–0.2&thinsp;µm³ cm⁻³ and a vertical resolution of around 3&thinsp;km. Comparisons with coincident observations by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite showed good agreement regarding the vertical profile shape. Quantitatively, in the case of supercooled ternary solution (STS) PSCs, the CALIOP dataset fits to the MIPAS retrievals obtained under the assumptions of small particles. Unlike for STS and NAT, in the case of ice PSCs the MIPAS retrievals are limited by the clouds becoming optically thick in the limb-direction. In these cases, the MIPAS volume densities represent lower limits. Among other interesting features, this climatology helps to study quantitatively the on-set of PSC formation very near to the South Pole and the large variability of the PSC volume densities between different Arctic stratospheric winters.</p>

G. Broquet, F.-M. Bréon, E. Renault et al.

This study assesses the potential of 2 to 10 km resolution imagery of CO₂ concentrations retrieved from the shortwave infrared measurements of a space-borne passive spectrometer for monitoring the spatially integrated emissions from the Paris area. Such imagery could be provided by missions similar to CarbonSat, which was studied as a candidate Earth Explorer 8 mission by the European Space Agency (ESA). This assessment is based on observing system simulation experiments (OSSEs) with an atmospheric inversion approach at city scale. The inversion system solves for hourly city CO₂ emissions and natural fluxes, or for these fluxes per main anthropogenic sector or ecosystem, during the 6 h before a given satellite overpass. These 6 h correspond to the period during which emissions produce CO₂ plumes that can be identified on the image from this overpass. The statistical framework of the inversion accounts for the existence of some prior knowledge with 50 % uncertainty on the hourly or sectorial emissions, and with ∼ 25 % uncertainty on the 6 h mean emissions, from an inventory based on energy use and carbon fuel consumption statistics. The link between the hourly or sectorial emissions and the vertically integrated column of CO₂ observed by the satellite is simulated using a coupled flux and atmospheric transport model. This coupled model is built with the information on the spatial and temporal distribution of emissions from the emission inventory produced by the local air-quality agency (Airparif) and a 2 km horizontal resolution atmospheric transport model. Tests are conducted for different realistic simulations of the spatial coverage, resolution, precision and accuracy of the imagery from sun-synchronous polar-orbiting missions, corresponding to the specifications of CarbonSat and Sentinel-5 or extrapolated from these specifications. First, OSSEs are conducted with a rather optimistic configuration in which the inversion system is perfectly informed about the statistics of the limited number of error sources. These OSSEs indicate that the image resolution has to be finer than 4 km to decrease the uncertainty in the 6 h mean emissions by more than 50 %. More complex experiments assess the impact of more realistic error estimates that current inversion methods do not properly account for, in particular, the systematic measurement errors with spatially correlated patterns. These experiments highlight the difficulty to improve current knowledge on CO₂ emissions for urban areas like Paris with CO₂ observations from satellites, and call for more technological innovations in the remote sensing of vertically integrated columns of CO₂ and in the inversion systems that exploit it.

M. Aubrecht, H. Bawden, C. Ballengee-Morris

D. Griffin, K. A. Walker, K. A. Walker et al.

This paper presents 8 years (2006–2013) of measurements obtained from Fourier transform spectrometers (FTSs) in the high Arctic at the Polar Environment Atmospheric Research Laboratory (PEARL; 80.05° N, 86.42° W). These measurements were taken as part of the Canadian Arctic ACE (Atmospheric Chemistry Experiment) validation campaigns that have been carried out since 2004 during the polar sunrise period (from mid-February to mid-April). Each spring, two ground-based FTSs were used to measure total and partial columns of HF, O₃, and trace gases that impact O₃ depletion, namely, HCl and HNO₃. Additionally, some tropospheric greenhouse gases and pollutant species were measured, namely CH₄, N₂O, CO, and C₂H₆. During the same time period, the satellite-based ACE-FTS made measurements near Eureka and provided profiles of the same trace gases. Comparisons have been carried out between the measurements from the Portable Atmospheric Research Interferometric Spectrometer for the InfraRed (PARIS-IR) and the co-located high-resolution Bruker 125HR FTS, as well as with the latest version of the ACE-FTS retrievals (v3.5). The total column comparison between the two co-located ground-based FTSs, PARIS-IR and Bruker 125HR, found very good agreement for most of these species (except HF), with differences well below the estimated uncertainties ( ≤ 6 &thinsp;%) and with high correlations (<i>R</i> ≥ 0. 8). Partial columns have been used for the ground-based to space-borne comparison, with coincident measurements selected based on time, distance, and scaled potential vorticity (sPV). The comparisons of the ground-based measurements with ACE-FTS show good agreement in the partial columns for most species within 6 &thinsp;% (except for C₂H₆ and PARIS-IR HF), which is consistent with the total retrieval uncertainty of the ground-based instruments. The correlation coefficients (<i>R</i>) of the partial column comparisons for all eight species range from approximately 0.75 to 0.95. The comparisons show no notable increases of the mean differences over these 8 years, indicating the consistency of these datasets and suggesting that the space-borne ACE-FTS measurements have been stable over this period. In addition, changes in the amounts of these trace gases during springtime between 2006 and 2013 are presented and discussed. Increased O₃ (0. 9 &thinsp;%&thinsp; yr⁻¹), HCl (1. 7 &thinsp;%&thinsp; yr⁻¹), HF (3. 8 &thinsp;%&thinsp; yr⁻¹), CH₄ (0.5 &thinsp;%&thinsp;yr⁻¹), and C₂H₆ (2. 3&thinsp;%&thinsp;yr⁻¹, 2009–2013) have been found with the PARIS-IR dataset, the longer of the two ground-based records.

T. Murschell, S. R. Fulgham, D. K. Farmer

Volatilization and subsequent processing in the atmosphere are an important environmental pathway for the transport and chemical fate of pesticides. However, these processes remain a particularly poorly understood component of pesticide lifecycles due to analytical challenges in measuring pesticides in the atmosphere. Most pesticide measurements require long (hours to days) sampling times coupled with offline analysis, inhibiting observation of meteorologically driven events or investigation of rapid oxidation chemistry. Here, we present chemical ionization time-of-flight mass spectrometry with iodide reagent ions as a fast and sensitive measurement of four current-use pesticides. These semi-volatile pesticides were calibrated with injections of solutions onto a filter and subsequently volatilized to generate gas-phase analytes. Trifluralin and atrazine are detected as iodide–molecule adducts, while permethrin and metolachlor are detected as adducts between iodide and fragments of the parent analyte molecule. Limits of detection (1 s) are 0.37, 0.67, 0.56, and 1.1 µg m⁻³ for gas-phase trifluralin, metolachlor, atrazine, and permethrin, respectively. The sensitivities of trifluralin and metolachlor depend on relative humidity, changing as much as 70 and 59, respectively, as relative humidity of the sample air varies from 0 to 80 %. This measurement approach is thus appropriate for laboratory experiments and potentially near-source field measurements.

Mark Davidson