bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of liquid–liquid phase separation and relative humidity on the heterogeneous OH oxidation of inorganic–organic aerosols: insights from methylglutaric acid and ammonium sulfate particles
Authors: Lam Hoi Ki , Xu Rongshuang , Choczynski Jack , Davies James F. , Ham Dongwan , Song Mijung , Zuend Andreas , Li Wentao , Tse Ying-Lung Steve , Chan Man Nin 
Published: February 2021

Abstract. Organic compounds residing near the surface of atmospheric aerosol particles
are exposed to chemical reactions initiated by gas-phase oxidants, such as
hydroxyl (OH) radicals. Aqueous droplets composed of inorganic salts and
organic compounds can undergo phase separation into two liquid phases,
depending on aerosol composition and relative humidity (RH). Such phase
behavior can govern the surface characteristics and morphology of the
aerosols, which in turn affect the heterogeneous reactivity of organic
compounds toward gas-phase oxidants. In this work, we used an aerosol flow
tube reactor coupled with an atmospheric pressure ionization source (direct
analysis in real time) and a high-resolution mass spectrometer to
investigate how phase separation in model aqueous droplets containing an
inorganic salt (ammonium sulfate, AS) and an organic acid (3-methylglutaric
acid, 3-MGA) with an organic-to-inorganic dry mass ratio (OIR) of 1 alters
the heterogeneous OH reactivity. At high RH, 3-MGA/AS aerosols were aqueous
droplets with a single liquid phase. When the RH decreased, aqueous 3-MGA/AS
droplets underwent phase separation at ∼75 % RH. Once the
droplets were phase-separated, they exhibited either a core–shell,
partially engulfed or a transition from core–shell to partially engulfed
structure, with an organic-rich outer phase and an inorganic-rich inner
phase. The kinetics, quantified by an effective heterogenous OH rate
constant, was found to increase gradually from 1.01±0.02×10-12 to 1.73±0.02×10-12 cm3 molec.−1 s−1 when the RH decreased from 88 % to 55 %. The heterogeneous reactivity of phase-separated droplets is slightly
higher than that of aqueous droplets with a single liquid phase. This could
be explained by the finding that when the RH decreases, higher
concentrations of organic molecules (i.e., 3-MGA) are present at or near the
droplet surface, which are more readily exposed to OH oxidation, as
demonstrated by phase separation measurements and model simulations. This
could increase the reactive collision probability between 3-MGA molecules
and OH radicals dissolved near the droplet surface and secondary chain
reactions. Even for phase-separated droplets with a fully established
core–shell structure, the diffusion rate of organic molecules across the
organic-rich outer shell is predicted to be fast in this system. Thus, the
overall rate of reactions is likely governed by the surface concentration of
3-MGA rather than a diffusion limitation. Overall, understanding the aerosol
phase state (single liquid phase versus two separate liquid phases) is
essential to better probe the heterogenous reactivity under different
aerosol chemical composition and environmental conditions (e.g., RH).
High-resolution hybrid inversion of IASI ammonia columns to constrain US ammonia emissions using the CMAQ adjoint model
Authors: Chen Yilin , Shen Huizhong , Kaiser Jennifer , Hu Yongtao , Capps Shannon L. , Zhao Shunliu , Hakami Amir , Shih Jhih-Shyang , Pavur Gertrude K. , Turner Matthew D. , Henze Daven K. , Resler Jaroslav , Nenes Athanasios , Napelenok Sergey L. , Bash Jesse O. , Fahey Kathleen M. , Carmichael Gregory R. , Chai Tianfeng , Clarisse Lieven , Coheur Pierre-François , Van Damme Martin , Russell Armistead G. 
Published: February 2021

Abstract. Ammonia (NH3) emissions have large impacts on air quality and nitrogen
deposition, influencing human health and the well-being of sensitive
ecosystems. Large uncertainties exist in the “bottom-up” NH3 emission
inventories due to limited source information and a historical lack of
measurements, hindering the assessment of NH3-related environmental
impacts. The increasing capability of satellites to measure NH3
abundance and the development of modeling tools enable us to better
constrain NH3 emission estimates at high spatial resolution. In this
study, we constrain the NH3 emission estimates from the widely used
2011 National Emissions Inventory (2011 NEI) in the US using Infrared
Atmospheric Sounding Interferometer NH3 column density measurements
(IASI-NH3) gridded at a 36 km by 36 km horizontal resolution. With a
hybrid inverse modeling approach, we use the Community Multiscale Air Quality Modeling System (CMAQ) and its multiphase adjoint model to optimize NH3 emission estimates in April, July, and October.
Our optimized emission estimates suggest that the total NH3 emissions
are biased low by 26 % in 2011 NEI in April with overestimation in the Midwest
and underestimation in the Southern States. In July and October, the
estimates from NEI agree well with the optimized emission estimates, despite
a low bias in hotspot regions. Evaluation of the inversion performance using
independent observations shows reduced underestimation in simulated ambient
NH3 concentration in all 3 months and reduced underestimation in
NH4+ wet deposition in April. Implementing the optimized NH3
emission estimates improves the model performance in simulating PM2.5
concentration in the Midwest in April. The model results suggest that the
estimated contribution of ammonium nitrate would be biased high in a priori
NEI-based assessments. The higher emission estimates in this study also
imply a higher ecological impact of nitrogen deposition originating from
NH3 emissions.
Concentrations, particle-size distributions, and dry deposition fluxes of aerosol trace elements over the Antarctic Peninsula in austral summer
Authors: Fan Songyun , Gao Yuan , Sherrell Robert M. , Yu Shun , Bu Kaixuan 
Published: February 2021

Abstract. Size-segregated particulate air samples were collected during the
austral summer of 2016–2017 at Palmer Station on Anvers Island, western Antarctic Peninsula,
to characterize trace elements in aerosols. Trace
elements in aerosol samples – including Al, P, Ca, Ti, V, Mn, Ni, Cu, Zn, Ce,
and Pb – were determined by total digestion and a sector field inductively
coupled plasma mass spectrometer (SF-ICP-MS). The crustal enrichment factors
(EFcrust) and k-means clustering results of particle-size distributions
show that these elements are derived primarily from three sources: (1) regional crustal emissions, including possible resuspension of soils
containing biogenic P, (2) long-range transport, and (3) sea salt. Elements
derived from crustal sources (Al, P, Ti, V, Mn, Ce) with
EFcrust<10 were dominated by the coarse-mode particles
(>1.8 µm) and peaked around 4.4 µm in diameter,
reflecting the regional contributions. Non-crustal elements (Ca, Ni, Cu, Zn,
Pb) showed EFcrust>10. Aerosol Pb was primarily dominated
by fine-mode particles, peaking at 0.14–0.25 µm, and likely was
impacted by air masses from southern South America based on air mass back
trajectories. However, Ni, Cu, and Zn were not detectable in most size
fractions and did not present clear size patterns. Sea-salt elements (Ca,
Na+, K+) showed a single-mode distribution and peaked at 2.5–4.4 µm. The estimated dry deposition fluxes of mineral dust for the
austral summer, based on the particle-size distributions of Al measured at
Palmer Station, ranged from 0.65 to 28 mg m−2 yr−1 with a mean of
5.5±5.0 mg m−2 yr−1. The estimated dry deposition fluxes
of the target trace elements in this study were lower than most fluxes
reported previously for coastal Antarctica and suggest that atmospheric
input of trace elements through dry deposition processes may play a minor
role in determining trace element concentrations in surface seawater over
the continental shelf of the western Antarctic Peninsula.
Global trends and European emissions of tetrafluoromethane (CF4), hexafluoroethane (C2F6) and octafluoropropane (C3F8)
Authors: Say Daniel , Manning Alistair J. , Western Luke M. , Young Dickon , Wisher Adam , Rigby Matthew , Reimann Stefan , Vollmer Martin K. , Maione Michela , Arduini Jgor , Krummel Paul B. , Mühle Jens , Harth Christina M. , Evans Brendan , Weiss Ray F. , Prinn Ronald G. , O'Doherty Simon 
Published: February 2021

Abstract. Perfluorocarbons (PFCs) are amongst the most potent greenhouse gases listed under the United Nations Framework Convention on Climate Change (UNFCCC). With atmospheric lifetimes on the order of thousands to tens of thousands of years, PFC emissions represent a permanent alteration to the global atmosphere on human timescales. While the industries responsible for the vast majority of these emissions – aluminium smelting and semi-conductor manufacturing – have made efficiency improvements and introduced abatement measures, the global mean mole fractions of three PFCs, namely tetrafluoromethane (CF4, PFC-14), hexafluoroethane (C2F6, PFC-116) and octafluoropropane (C3F8, PFC-218), continue to grow. In this study, we update baseline growth rates using in situ high-frequency measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) and, using data from four European stations, estimate PFC emissions for northwest Europe. The global growth rate of CF4 decreased from 1.3 ppt yr−1 in 1979 to 0.6 ppt yr−1 around 2010 followed by a renewed steady increase to 0.9 ppt yr−1 in 2019. For C2F6, the growth rate grew to a maximum of 0.125 ppt yr−1 around 1999, followed by a decline to a minimum of 0.075 ppt yr−1 in 2009, followed by weak growth thereafter. The C3F8 growth rate was around 0.007 ppt yr−1 until the early 1990s and then quickly grew to a maximum of 0.03 ppt yr−1 in 2003–2004. Following a period of decline until 2012 to 0.015 ppt yr−1, the growth rate slowly increased again to ∼ 0.017 ppt yr−1 in 2019. We used an inverse modelling framework to infer PFC emissions for northwest Europe. No statistically significant trend in regional emissions was observed for any of the PFCs assessed. For CF4, European emissions in early years were linked predominantly to the aluminium industry. However, we link large emissions in recent years to a chemical manufacturer in northwest Italy. Emissions of C2F6 are linked to a range of sources, including a semi-conductor manufacturer in Ireland and a cluster of smelters in Germany's Ruhr valley. In contrast, northwest European emissions of C3F8 are dominated by a single source in northwest England, raising the possibility of using emissions from this site for a tracer release experiment.
The Portable Ice Nucleation Experiment (PINE): a new online instrument for laboratory studies and automated long-term field observations of ice-nucleating particles
Authors: Möhler Ottmar , Adams Michael , Lacher Larissa , Vogel Franziska , Nadolny Jens , Ullrich Romy , Boffo Cristian , Pfeuffer Tatjana , Hobl Achim , Weiß Maximilian , Vepuri Hemanth S. K. , Hiranuma Naruki , Murray Benjamin J. 
Published: February 2021

Abstract. Atmospheric ice-nucleating particles (INPs) play an important role in determining the phase of clouds, which affects their albedo and lifetime. A lack of data on the spatial and temporal variation of INPs around the globe limits our predictive capacity and understanding of clouds containing ice. Automated instrumentation that can robustly measure INP concentrations across the full range of tropospheric temperatures is needed in order to address this knowledge gap. In this study, we demonstrate the functionality and capacity of the new Portable Ice Nucleation Experiment (PINE) to study ice nucleation processes and to measure INP concentrations under conditions pertinent for mixed-phase clouds, with temperatures from about −10 to about −40 ∘C. PINE is a cloud expansion chamber which avoids frost formation on the cold walls and thereby omits frost fragmentation and related background ice signals during the operation. The development, working principle and treatment of data for the PINE instrument is discussed in detail. We present laboratory-based tests where PINE measurements were compared with those from the established AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Within experimental uncertainties, PINE agreed with AIDA for homogeneous freezing of pure water droplets and the immersion freezing activity of mineral aerosols. Results from a first field campaign conducted at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) observatory in Oklahoma, USA, from 1 October to 14 November 2019 with the latest PINE design (a commercially available PINE chamber) are also shown, demonstrating PINE's ability to make automated field measurements of INP concentrations at a time resolution of about 8 min with continuous temperature scans for INP measurements between −10 and −30 ∘C. During this field campaign, PINE was continuously operated for 45 d in a fully automated and semi-autonomous way, demonstrating the capability of this new instrument to also be used for longer-term field measurements and INP monitoring activities in observatories.
Subsurface flow and phosphorus dynamics in beech forest hillslopes during sprinkling experiments: how fast is phosphorus replenished?
Authors: Rinderer Michael , Krüger Jaane , Lang Friederike , Puhlmann Heike , Weiler Markus 
Published: February 2021

Abstract. The phosphorus (P) concentration of soil solution is of
key importance for plant nutrition. During large rainfall events, the P
concentration is altered by lateral and vertical subsurface storm flow (SSF)
that facilitates P mobilization, redistribution within the soil profile and
potential P export from the ecosystem. These processes are not well studied
under field conditions. Important factors of the replenishment of P
concentrations in soil solutions are the rate of P replenishment (by biotic
and abiotic processes) and the P buffering capacity of soils. Lab
experiments have shown that replenishment times can vary between minutes and
months. The question remains of how P concentrations in lateral and vertical
SSF vary under natural field conditions. We present results of large-scale
sprinkling experiments simulating 150 mm throughfall at 200 m2 plots on
hillslopes at three beech forests in Germany. We aimed at quantifying
lateral and vertical SSF and associated P concentrations on the forest
floor, in the mineral soil and in the saprolite during sprinkling experiments in
spring and summer. The sites differed mainly in terms of soil depth,
skeleton content and soil P stock (between 189 and 624 g/m2 in the top 1 m soil depth). Vertical SSF in the mineral soil
and in the saprolite was at least 2 orders of magnitude larger than
lateral SSF at the same depth. Vertical and lateral SSF consisted mainly of
pre-event water that was replaced by sprinkling water. Higher P
concentrations in SSF in the first 1 to 2 h after the onset of SSF indicated
nutrient flushing, but P concentrations in the mineral soil and saprolite
were nearly constant thereafter for most of the experiment despite a strong
increase in SSF. This suggests that P in the soil solution at all three
sites was replenished fast by mineral or organic sources. If chemostatic
transport conditions would dominate in SSF, annual P losses at the lateral
and vertical boundary of a forest plot could be approximated by knowing the
average P concentration and the water fluxes in forest soils. A rough
estimation of the annual P loss based on this simplified assumption for one
of our sites with longer SSF data resulted in an annual P loss of
3.16 mg/m2/a. This P loss is similar to estimates from a previous study
at the same site using bi-weekly groundwater samples. Our approximated
annual P loss in SSF was in a similar order of magnitude as P input by dry
and wet deposition and by mineral weathering. Despite the fact that P losses
from the ecosystem seem to be small, the translocation of P from the forest
floor to the mineral soil might be of high relevance at sites with low P
stocks where the forest floor is the dominant source for the P nutrition of
trees.
The climate benefit of carbon sequestration
Authors: Sierra Carlos A. , Crow Susan E. , Heimann Martin , Metzler Holger , Schulze Ernst-Detlef 
Published: February 2021

Abstract. Ecosystems play a fundamental role in climate change mitigation by photosynthetically fixing carbon from the atmosphere and storing it for a period of time in organic matter. Although climate impacts of carbon emissions by sources can be quantified by global warming potentials, the appropriate formal metrics to assess climate benefits of carbon removals by sinks are unclear.
We introduce here the climate benefit of sequestration (CBS), a metric that quantifies the radiative effect of fixing carbon dioxide from the atmosphere and retaining it for a period of time in an ecosystem before releasing it back as the result of respiratory processes and disturbances.
In order to quantify CBS, we present a formal definition of carbon sequestration (CS) as the integral of an amount of carbon removed from the atmosphere stored over the time horizon it remains within an ecosystem. Both metrics incorporate the separate effects of (i) inputs (amount of atmospheric carbon removal) and (ii) transit time (time of carbon retention) on carbon sinks, which can vary largely for different ecosystems or forms of management.
These metrics can be useful for comparing the climate impacts of carbon removals by different sinks over specific time horizons, to assess the climate impacts of ecosystem management, and to obtain direct quantifications of climate impacts as the net effect of carbon emissions by sources versus removals by sinks.
Crowdsourced air traffic data from the OpenSky Network 2019–2020
Authors: Strohmeier Martin , Olive Xavier , Lübbe Jannis , Schäfer Matthias , Lenders Vincent 
Published: February 2021

Abstract. The OpenSky Network is a non-profit association that crowdsources the global collection of live air traffic control data broadcast by aircraft and makes them available to researchers. OpenSky's data have been used by over 100 academic groups in the past 5 years, with popular research applications ranging from improved weather forecasting to climate analysis. With the COVID-19 outbreak, the demand for live and historic aircraft flight data has surged. Researchers around the world use air traffic data to comprehend the spread of the pandemic and analyse the effects of the global containment measures on economies, climate and other systems. With this work, we present a comprehensive air traffic dataset, derived and enriched from the full OpenSky data and made publicly available for the first time (Olive et al., 2020; https://doi.org/10.5281/zenodo.3931948, last access: 9 February 2021). It spans all flights seen by the network's more than 3500 members between 1 January 2019 and 1 July 2020. The archive is being updated every month and for the first 18 months includes 41 900 660 flights, from 160 737 aircraft, which were seen to frequent 13 934 airports in 127 countries.
Synchronized high-resolution bed-level change and biophysical data from 10 marsh–mudflat sites in northwestern Europe
Authors: Hu Zhan , Willemsen Pim W. J. M. , Borsje Bas W. , Wang Chen , Wang Heng , van der Wal Daphne , Zhu Zhenchang , Oteman Bas , Vuik Vincent , Evans Ben , Möller Iris , Belliard Jean-Philippe , Van Braeckel Alexander , Temmerman Stijn , Bouma Tjeerd J. 
Published: February 2021

Abstract. Tidal flats provide valuable ecosystem services such as
flood protection and carbon sequestration. Erosion and accretion processes
govern the ecogeomorphic evolution of intertidal ecosystems (marshes and
bare flats) and, hence, substantially affect their valuable ecosystem
services. To understand the intertidal ecosystem development, high-frequency
bed-level change data are thus needed. However, such datasets are scarce due
to the lack of suitable methods that do not involve excessive labour and/or
costly instruments. By applying newly developed surface elevation dynamics (SED)
sensors, we obtained unique high-resolution daily bed-level
change datasets in the period 2013–2017 from 10 marsh–mudflat sites
situated in the Netherlands, Belgium, and the United Kingdom in contrasting physical and
biological settings. At each site, multiple sensors were deployed for 9–20 months to ensure sufficient spatial and temporal coverage of highly variable
bed-level change processes. The bed-level change data are provided with
synchronized hydrodynamic data, i.e. water level, wave height, tidal
current velocity, medium sediment grain size (D50), and chlorophyll a
level at four sites. This dataset has revealed diverse spatial
morphodynamics patterns over daily to seasonal scales, which are valuable to
theoretical and model development. On the daily scale, this dataset is
particularly instructive, as it includes a number of storm events, the
response to which can be detected in the bed-level change observations. Such
data are rare but useful to study tidal flat response to highly energetic
conditions. The dataset is available from 4TU.ResearchData (https://doi.org/10.4121/12693254.v4; Hu et al., 2020), which is expected to expand with additional SED sensor data from
ongoing and planned surveys.
Modeling the response of soil moisture to climate variability in the Mediterranean region
Authors: Mimeau Louise , Tramblay Yves , Brocca Luca , Massari Christian , Camici Stefania , Finaud-Guyot Pascal 
Published: February 2021

Abstract. Future climate scenarios for the Mediterranean region indicate a possible decrease in annual precipitation associated with an intensification of extreme rainfall events in the coming years. A major challenge in this region is to evaluate the impacts of changing precipitation patterns on extreme hydrological events such as droughts and floods. For this, it is important to understand the impact of climate change on soil moisture since it is a proxy for agricultural droughts, and the antecedent soil moisture condition plays a key role on runoff generation. This study focuses on 10 sites, located in southern France, with available soil moisture, temperature, and precipitation observations for a 10-year time period. Soil moisture is simulated at each site at the hourly time step using a model of soil water content. The sensitivity of the simulated soil moisture to different changes in precipitation and temperature is evaluated by simulating the soil moisture response to temperature and precipitation scenarios generated using a delta change method for temperature and a stochastic model (the Neyman–Scott rectangular pulse model) for precipitation. Results show that soil moisture is more impacted by changes in precipitation intermittence than precipitation intensity and temperature. Overall, increased temperature and precipitation intensity associated with more intermittent precipitation leads to decreased soil moisture and an increase in the annual number of days with dry soil moisture conditions. In particular, a temperature increase of +4 ∘C combined with a decrease of annual rainfall between 10 % and 20 %, corresponding to the current available climate scenarios for the Mediterranean, lead to a lengthening of the drought period from June to October with an average of +28 d of soil moisture drought per year.