Local and regional modelling of NH3 surface exchange is required to quantify nitrogen deposition to, and emissions from, the biosphere. However, measurements and model parameterisations for many ...remote ecosystems – such as tropical rainforest – remain sparse. Using 1 month of hourly measurements of NH3 fluxes and meteorological parameters over a remote Amazon rainforest site (Amazon Tall Tower Observatory, ATTO), six model parameterisations based on a bidirectional, single-layer canopy compensation point resistance model were developed to simulate observations of NH3 surface exchange. Canopy resistance was linked to either relative humidity at the canopy level (RHz0′), vapour pressure deficit, or a parameter value based on leaf wetness measurements. The ratio of apoplastic NH4+ to H+ concentration, Γs, during this campaign was inferred to be 38.5 ± 15.8. The parameterisation that reproduced the observed net exchange of NH3 most accurately was the model that used a cuticular resistance (Rw) parameterisation based on leaf wetness measurements and a value of Γs=50 (Pearson correlation r=0.71). Conversely, the model that performed the worst at replicating measured NH3 fluxes used an Rw value modelled using RHz0′ and the inferred value of Γs=38.5 (r=0.45). The results indicate that a single-layer canopy compensation point model is appropriate for simulating NH3 fluxes from tropical rainforest during the Amazonian dry season and confirmed that a direct measurement of (a non-binary) leaf wetness parameter improves the ability to estimate Rw. Current inferential methods for determining Γs were noted as having difficulties in the humid conditions present at a rainforest site.
Intensively managed grazed grasslands in temperate climates are globally important environments for the exchange of the greenhouse gases (GHGs) carbon dioxide (CO2), nitrous oxide (N2O) and methane ...(CH4). We assessed the N and C budget of a mostly grazed and occasionally cut and fertilised grassland in SE Scotland by measuring or modelling all relevant imports and exports to the field as well as changes in soil C and N stocks over time. The N budget was dominated by import from inorganic and organic fertilisers (21.9 g N m−2 a−1) and losses from leaching (5.3 g N m−2 a−1), N2 emissions (2.9 g N m−2 a−1), and NOx and NH3 volatilisation (3.9 g N m−2 a−1), while N2O emission was only 0.6 g N m−2 a−1. The efficiency of N use by animal products (meat and wool) averaged 9.9 % of total N input over only-grazed years (2004–2010). On average over 9 years (2002–2010), the balance of N fluxes suggested that 6.0 ± 5.9 g N m−2 a−1 (mean ± confidence interval at p > 0.95) were stored in the soil. The largest component of the C budget was the net ecosystem exchange of CO2 (NEE), at an average uptake rate of 218 ± 155 g C m−2 a−1 over the 9 years. This sink strength was offset by carbon export from the field mainly as grass offtake for silage (48.9 g C m−2 a−1) and leaching (16.4 g C m−2 a−1). The other export terms, CH4 emissions from the soil, manure applications and enteric fermentation, were negligible and only contributed to 0.02–4.2 % of the total C losses. Only a small fraction of C was incorporated into the body of the grazing animals. Inclusion of these C losses in the budget resulted in a C sink strength of 163 ± 140 g C m−2 a−1. By contrast, soil stock measurements taken in May 2004 and May 2011 indicated that the grassland sequestered N in the 0–60 cm soil layer at 4.51 ± 2.64 g N m−2 a−1 and lost C at a rate of 29.08 ± 38.19 g C m−2 a−1. Potential reasons for the discrepancy between these estimates are probably an underestimation of C losses, especially from leaching fluxes as well as from animal respiration. The average greenhouse gas (GHG) balance of the grassland was −366 ± 601 g CO2 eq. m−2 yr−1 and was strongly affected by CH4 and N2O emissions. The GHG sink strength of the NEE was reduced by 54 % by CH4 and N2O emissions. Estimated enteric fermentation from ruminating sheep proved to be an important CH4 source, exceeding the contribution of N2O to the GHG budget in some years.
Recent studies have identified suggestive prenatal features of RASopathies (e.g., increased nuchal translucency NT, cystic hygroma CH, hydrops, effusions, congenital heart diseases CHD, ...polyhydramnios, renal anomalies). Our objective is to clarify indications for RASopathy prenatal testing. We compare genotype distributions between pre- and postnatal populations and propose genotype–phenotype correlations.
Three hundred fifty-two chromosomal microarray–negative cases sent for prenatal RASopathy testing between 2012 and 2019 were collected. For most, 11 RASopathy genes were tested. Postnatal cohorts (25 patients with available prenatal information and 108 institutional database genotypes) and the NSeuroNet database were used for genotypic comparisons.
The overall diagnostic yield was 14% (50/352), with rates >20% for effusions, hydrops, and CHD. Diagnostic yield was significantly improved in presence of hypertrophic cardiomyopathy (HCM), persistent or associated CH, any suggestive finding combined with renal anomaly or polyhydramnios, or ≥2 ultrasound findings. Largest prenatal contributors of pathogenic variants were PTPN11 (30%), RIT1 (16%), RAF1 (14%), and HRAS (12%), which considerably differ from their prevalence in postnatal populations. HRAS, LZTR1, and RAF1 variants correlated with hydrops/effusions, and RIT1 with prenatal onset HCM.
After normal chromosomal microarray, RASopathies should be considered when any ultrasound finding of lymphatic dysplasia or suggestive CHD is found alone or in association.
Under the EU Air Quality Directive (AQD) 2008/50/EC member states are required to undertake routine monitoring of PM2.5 composition at background stations. The AQD states for PM2.5 speciation this ...should include at least: nitrate (NO3−), sulfate (SO42−), chloride (Cl−), ammonium (NH4+), sodium (Na+), potassium (K+), magnesium (Mg2+), calcium (Ca2+), elemental carbon (EC) and organic carbon (OC). Until 2017, it was the responsibility of each country to determine the methodology used to report the composition for the inorganic components of PM2.5. In August 2017 a European standard method of measurement of PM2.5 inorganic chemical components (NO3−, SO42−, Cl−, NH4+, Na+, K+, Mg2+, Ca2+) as deposited on filters (EN16913:2017) was published. From August 2019 this then became the European standard method. This filter method is labour-intensive and provides limited time resolution and is prone to losses of volatile compounds. There is therefore increasing interest in the use of alternative automated methods. For example, the UK reports hourly PM2.5 chemical composition using the Monitor for AeRosols and Gases in Ambient air (MARGA, Metrohm, NL). This study is a pre-assessment review of available data to demonstrate if or to what extent equivalence is possible using either the MARGA or other available automatic methods, including the Aerosol Chemical Speciation Monitor (ACSM, Aerodyne Research Inc. US) and the Ambient Ion Monitor (AIM, URG, US).
To demonstrate equivalence three objectives were to be met. The first two objectives focused on data capture and were met by all three instruments. The third objective was to have less than a 50% expanded uncertainty compared to the reference method for each species. Analysis of this objective was carried out using existing paired datasets available from different regions around the world. It was found that the MARGA (2006–2019 model) had the potential to demonstrate equivalence for all species in the standard, though it was only through a combination of case studies that it passed uncertainty criteria. The ACSM has the potential to demonstrate equivalence for NH4+, SO42−, and in some conditions NO3−, but did not for Cl− due to its inability to quantify refractory aerosol such as sea salt. The AIM has the potential for NH4+, NO3−, SO42−, Cl− and Mg2+. Future investigations are required to determine if the AIM could be optimised to meet the expanded uncertainty criterion for Na+, K+ and Ca2+.
The recommendation is that a second stage to demonstrate equivalence is required which would include both laboratory and field studies of the three candidate methods and any other technologies identified with the potential to report the required species.
•Comparison of EN16913:2017 filter method for speciated inorganic PM2.5 against automatic methods.•Automatic methods have the potential to demonstrate equivalence for some or all species.•Further field and laboratory studies are required to demonstrate equivalence for speciated PM2.5
Air pollution in urban environments has been shown to have a negative impact on air quality and human health, particularly in megacities. Over recent decades, Delhi, India, has suffered high ...atmospheric pollution, with significant particulate matter (PM) concentrations as a result of anthropogenic activities. Organic aerosols (OAs) are composed of thousands of different chemical species and are one of the main constituents of submicron particles. However, quantitative knowledge of OA composition, their sources and their processes in urban environments is still limited. This is important particularly in India, as Delhi is a massive, inhomogeneous conurbation, where we would expect the apportionment and concentrations to vary depending on where in Delhi the measurements/source apportionment is performed, indicating the need for multisite measurements. This study presents the first multisite analysis carried out in India over different seasons, with a focus on identifying OA sources. The measurements were taken during 2018 at two sites in Delhi, India. One site was located at the India Meteorological Department, New Delhi (ND). The other site was located at the Indira Gandhi Delhi Technical University for Women, Old Delhi (OD). Non-refractory submicron aerosol (NR-PM1) concentrations (ammonium, nitrate, sulfate, chloride and organic aerosols) of four aerosol mass spectrometers were analysed. Collocated measurements of volatile organic compounds, black carbon, NOx and CO were performed. Positive matrix factorisation (PMF) analysis was performed to separate the organic fraction, identifying a number of conventional factors: hydrocarbon-like OAs (HOAs) related to traffic emissions, biomass burning OAs (BBOAs), cooking OAs (COAs) and secondary OAs (SOAs).A composition-based estimate of PM1 is defined by combining black carbon (BC) and NR-PM1 (C-PM1= BC + NR-PM1). No significant difference was observed in C-PM1 concentrations between sites, OD (142 ± 117 µg m-3) compared to ND (123 ± 71 µg m3), from post-monsoon measurements. A wider variability was observed between seasons, where pre-monsoon and monsoon showed C-PM1 concentrations lower than 60 µg m-3. A seasonal variation in C-PM1 composition was observed; SO42- showed a high contribution over pre-monsoon and monsoon seasons, while NO3- and Cl- had a higher contribution in winter and post-monsoon. The main primary aerosol source was from traffic, which is consistent with the PMF analysis and Aethalometer model analysis. Thus, in order to reduce PM1 concentrations in Delhi through local emission controls, traffic emission control offers the greatest opportunity. PMF–aerosol mass spectrometer (AMS) mass spectra will help to improve future aerosol source apportionment studies. The information generated in this study increases our understanding of PM1 composition and OA sources in Delhi, India. Furthermore, the scientific findings provide significant information to strengthen legislation that aims to improve air quality in India.
The Amazon rainforest presents a unique, natural laboratory for the study of surface–atmosphere interactions. Its alternation between a near-pristine marine-influenced atmosphere during the wet ...season and a vulnerable system affected by periodic intrusions of anthropogenic pollution during the dry season provides an opportunity to investigate some fundamental aspects of boundary-layer chemical processes. This study presents the first simultaneous hourly measurements of concentrations, fluxes, and deposition velocities of the inorganic trace gases NH3, HCl, HONO, HNO3, and SO2 as well as their water-soluble aerosol counterparts NH4+, Cl−, NO2-, NO3- and SO42- over the Amazon. Species concentrations were measured in the dry season (from 6 October to 5 November 2017), at the Amazon Tall Tower Observatory (ATTO) in Brazil, using a two-point gradient wet-chemistry instrument (GRadient of AErosols and Gases Online Registration, GRAEGOR) sampling at 42 and 60 m. Fluxes and deposition velocities were derived from the concentration gradients using a modified form of the aerodynamic gradient method corrected for measurement within the roughness sub-layer. Findings from this campaign include observations of elevated concentrations of NH3 and SO2 partially driven by long-range transport (LRT) episodes of pollution and the substantial influence of coarse Cl− and NO3- particulate on overall aerosol mass burdens. From the flux measurements, the dry season budget of total reactive nitrogen dry deposition at the ATTO site was estimated as −2.9 kg N ha-1a-1. HNO3 and HCl were deposited continuously at a rate close to the aerodynamic limit. SO2 was deposited with an average daytime surface resistance (Rc) of 28 s m−1, whilst aerosol components showed average surface deposition velocities of 2.8 and 2.7 mm s−1 for SO42- and NH4+, respectively. Deposition rates of NO3- and Cl− were higher at 7.1 and 7.8 mm s−1, respectively, reflecting their larger average size. The exchange of NH3 and HONO was bidirectional, with NH3 showing emission episodes in the afternoon and HONO in the early morning hours. This work provides a unique dataset to test and improve dry deposition schemes for these compounds for tropical rainforest, which have typically been developed by interpolation from conditions in temperate environments. A future campaign should focus on making similar measurements in the wet season in order to provide a complete view of the annual pattern of inorganic trace gas and coarse aerosol biosphere–atmosphere exchange over tropical rainforest.
Studying the vertical distribution of aerosol particle physical and chemical properties in the troposphere is essential to understand the relative importance of local emission processes vs. ...long-range transport for column-integrated aerosol properties (e.g. the aerosol optical depth, AOD, affecting regional climate) as well as for the aerosol burden and its impacts on air quality at the ground. The main objective of this paper is to investigate the transport of desert dust in the middle troposphere and its intrusion into the planetary boundary layer (PBL) over the Po Valley (Italy), a region considered one of the greatest European pollution hotspots for the frequency that particulate matter (PM) limit values are exceeded. Events of mineral aerosol uplift from local (soil) sources and phenomena of hygroscopic growth at the ground are also investigated, possibly affecting the PM concentration in the region as well. During the PEGASOS 2012 field campaign, an integrated observing–modelling system was set up based on near-surface measurements (particle concentration and chemistry), vertical profiling (backscatter coefficient profiles from lidar and radiosoundings) and Lagrangian air mass transport simulations by FLEXPART model. Measurements were taken at the San Pietro Capofiume supersite (44°39′ N, 11°37′ E; 11 m a.s.l.), located in a rural area relatively close to some major urban and industrial emissive areas in the Po Valley. Mt. Cimone (44°12′ N, 10°42′ E; 2165 m a.s.l.) WMO/GAW station observations are also included in the study to characterize regional-scale variability. Results show that, in the Po Valley, aerosol is detected mainly below 2000 m a.s.l. with a prevalent occurrence of non-depolarizing particles ( > 50 % throughout the campaign) and a vertical distribution modulated by the PBL daily evolution. Two intense events of mineral dust transport from northern Africa (19–21 and 29 June to 2 July) are observed, with layers advected mainly above 2000 m, but subsequently sinking and mixing in the PBL. As a consequence, a non-negligible occurrence of mineral dust is observed close to the ground ( ∼ 7 % of occurrence during a 1-month campaign). The observations unambiguously show Saharan dust layers intruding the Po Valley mixing layer and directly affecting the aerosol concentrations near the surface. Finally, lidar observations also indicate strong variability in aerosol on shorter timescales (hourly). Firstly, these highlight events of hygroscopic growth of anthropogenic aerosol, visible as shallow layers of low depolarization near the ground. Such events are identified during early morning hours at high relative humidity (RH) conditions (RH > 80 %). The process is observed concurrently with high PM1 nitrate concentration (up to 15 µg cm−3) and hence mainly explicable by deliquescence of fine anthropogenic particles, and during mineral dust intrusion episodes, when water condensation on dust particles could instead represent the dominant contribution. Secondly, lidar images show frequent events (mean daily occurrence of ∼ 22 % during the whole campaign) of rapid uplift of mineral depolarizing particles in afternoon–evening hours up to 2000 m a.s.l. height. The origin of such particles cannot be directly related to long-range transport events, being instead likely linked to processes of soil particle resuspension from agricultural lands.
We describe a case of collodion baby diagnosed prenatally by ultrasound. Classic signs (ectropion, flattened nose, and eclabion) were detected on routine ultrasound at 21 weeks of gestation. At ...birth, the presence of collodion membrane was confirmed and subsequently, the diagnosis of an autosomal recessive congenital ichthyosis due to compound heterozygosity of the TGM1 gene was made.
The increasing use of intensive agricultural practices can lead to damaging
consequences for the atmosphere through enhanced emissions of air pollutants.
However, there are few direct measurements of ...the surface–atmosphere exchange
of trace gases and water-soluble aerosols over agricultural grassland,
particularly of reactive nitrogen compounds. In this study, we present
measurements of the concentrations, fluxes and deposition velocities of the
trace gases HCl, HONO, HNO3, SO2 and NH3 as well as their
associated water-soluble aerosol counterparts Cl−, NO2-,
NO3-, SO42- and NH4+ as determined hourly
for 1 month in May–June 2016 over agricultural grassland near Edinburgh,
UK, pre- and postfertilisation. Measurements were made using the Gradient
of Aerosols and Gases Online Registrator (GRAEGOR) wet-chemistry two-point
gradient instrument. Emissions of NH3 peaked at
1460 ngm-2s-1 3 h after fertilisation, with an
emission of HONO peaking at 4.92 ngm-2s-1 occurring 5 h
after fertilisation. Apparent emissions of NO3- aerosol
were observed after fertilisation which, coupled with a divergence of
HNO3 deposition velocity (Vd) from its theoretical maximum
value, suggested the reaction of emitted NH3 with atmospheric
HNO3 to form ammonium nitrate aerosol. The use of the conservative
exchange fluxes of tot-NH4+ and tot-NO3- indicated
net emission of tot-NO3-, implying a ground source of
HNO3 after fertilisation. Daytime concentrations of HONO remained
above the detection limit (30 ng m−3) throughout the campaign,
suggesting a daytime source for HONO at the site. Whilst the mean Vd of
NH4+ was 0.93 mm s−1 in the range expected for the
accumulation mode, the larger average Vd for Cl− (3.65 mm s−1),
NO3- (1.97 mm s−1) and SO42- (1.89 mm s−1) reflected the
contribution of a super-micron fraction and decreased with increasing
PM2.5∕PM10 ratio (a proxy measurement for aerosol size), providing
evidence – although limited by the use of a proxy for aerosol size – of a
size dependence of aerosol deposition velocity for aerosol chemical
compounds, which has been suggested from process-orientated models of aerosol
deposition.
We present the first real-time composition of submicron particulate matter
(PM1) in Old Delhi using high-resolution aerosol mass spectrometry
(HR-AMS). Old Delhi is one of the most polluted locations ...in the world, and
PM1 concentrations reached ∼ 750 µg m−3
during the most polluted period, the post-monsoon period, where PM1 increased
by 188 % over the pre-monsoon period. Sulfate contributes the largest
inorganic PM1 mass fraction during the pre-monsoon (24 %) and monsoon
(24 %) periods, with nitrate contributing most during the post-monsoon period
(8 %). The organics dominate the mass fraction (54 %–68 %) throughout the
three periods, and, using positive matrix factorisation (PMF) to perform
source apportionment analysis of organic mass, two burning-related factors
were found to contribute the most (35 %) to the post-monsoon increase. The
first PMF factor, semi-volatility biomass burning organic aerosol (SVBBOA),
shows a high correlation with Earth observation fire counts in surrounding
states, which links its origin to crop residue burning. The second is a
solid fuel OA (SFOA) factor with links to local open burning due to its high
composition of polyaromatic hydrocarbons (PAHs) and novel AMS-measured marker
species for polychlorinated dibenzodioxins (PCDDs) and polychlorinated
dibenzofurans (PCDFs). Two traffic factors were resolved: one
hydrocarbon-like OA (HOA) factor and another nitrogen-rich HOA (NHOA)
factor. The N compounds within NHOA were mainly nitrile species which have
not previously been identified within AMS measurements. Their PAH
composition suggests that NHOA is linked to diesel and HOA to compressed
natural gas and petrol. These factors combined make the largest relative
contribution to primary PM1 mass during the pre-monsoon and monsoon
periods while contributing the second highest in the post-monsoon period. A
cooking OA (COA) factor shows strong links to the secondary factor,
semi-volatility oxygenated OA (SVOOA). Correlations with co-located volatile
organic compound (VOC) measurements and AMS-measured organic nitrogen oxides
(OrgNO) suggest SVOOA is formed from aged COA. It is also found that a
significant increase in chloride concentrations (522 %) from pre-monsoon
to post-monsoon correlates well with SVBBOA and SFOA, suggesting that crop
residue burning and open waste burning are responsible. A reduction in
traffic emissions would effectively reduce concentrations across most of the
year. In order to reduce the post-monsoon peak, sources such as funeral
pyres, solid waste burning and crop residue burning should be considered
when developing new air quality policy.
PDF
