The visibility on New Year's nights in the Netherlands is low during stagnant weather. This is due to the scattering and absorption of light by the aerosol-smoke from the fireworks. We made an ...assessment of the responsible aerosol-species. The investigation took place during the New Year's night of 2009. Measurements were made at a regional site in the centre of the country away from specific local sources. An Integrating Nephelometer measured the light-scattering by the inherent compounds after removal of water from the aerosol by drying the air. The actual light-scattering was determined in an open-air scatterometer; it was a factor of five higher than the “dry” value. The difference in actual and “dry” light-scattering can only be explained by water–uptake of the salty hygroscopic components of the aerosol. This hypothesis is substantiated by measurements of the composition of the aerosol. The size-dependent concentrations of the salty ionic species were determined on-line with a MARGA-“sizer”. These components were for a large part in particles in the size range that most effectively scatter light. The “dry” light-scattering was exerted by the inorganic salt components and the sooty carbonaceous material alike. However, the salty products from the fireworks are hygroscopic and take up water at the high relative humidities occurring that night. This explains the fivefold larger light-scattering by the wet ambient aerosol as compared to that by the dry aerosol in the integrating nephelometer. The visibility, which is the inverse of the open-air scattering, is thus indirectly governed by the salty products of the fireworks due to their uptake of water. Under stagnant weather conditions during New Year's nights in the Netherlands both the aerosol concentrations and the relative humidity are high; this implies that the ionic species govern the low visibilities in general, be it via their uptake of water.
•Aerosol particles from fireworks are optimal scatterers of visible light.•Water uptake by the salty ingredients led to a much larger scattering.•Visibility, inversely related to light-scattering, approached dense fog.
The mass concentration of black carbon (BC) particles in the
atmosphere has traditionally been quantified with two methods: as elemental
carbon (EC) concentrations measured by thermal–optical ...analysis and as
equivalent black carbon (eBC) concentrations when BC mass is derived from
particle light absorption coefficient measurements. Over the last decade,
ambient measurements of refractory black carbon (rBC) mass concentrations
based on laser-induced incandescence (LII) have become more common, mostly
due to the development of the Single Particle Soot Photometer (SP2)
instrument. In this work, EC and rBC mass concentration measurements from
field campaigns across several background European sites (Palaiseau,
Bologna, Cabauw and Melpitz) have been collated and examined to identify the
similarities and differences between BC mass concentrations measured by the
two techniques. All EC concentration measurements in PM2.5 were
performed with the EUSAAR-2 thermal–optical protocol. All rBC
concentration measurements were performed with SP2 instruments calibrated with the same
calibration material as recommended in the literature. The observed values
of median rBC-to-EC mass concentration ratios on the single-campaign level were
0.53, 0.65, 0.97, 1.20 and 1.29, respectively, and the geometric standard
deviation (GSD) was 1.5 when considering all data points from all five
campaigns. This shows that substantial systematic bias between these two
quantities occurred during some campaigns, which also contributes to the
large overall GSD. Despite considerable variability in BC properties and
sources across the whole dataset, it was not possible to clearly assign
reasons for discrepancies to one or the other method, both known to have
their own specific limitations and uncertainties. However, differences in
the particle size range covered by these two methods were identified as one
likely reason for discrepancies. Overall, the observed correlation between rBC and EC mass reveals a linear
relationship with a constant ratio, thus providing clear evidence that both
methods essentially quantify the same property of atmospheric aerosols,
whereas systematic differences in measured absolute values by up to a factor
of 2 can occur. This finding for the level of agreement between two current
state-of-the-art techniques has important implications for studies based
on BC mass concentration measurements, for example for the interpretation of
uncertainties in inferred BC mass absorption coefficient values, which are
required for modeling the radiative forcing of BC. Homogeneity between BC
mass determination techniques is also very important for moving towards a routine BC
mass measurement for air quality regulations.
The densest network for measuring air pollutant concentrations in Colombia is in Medellin, where most sensors are located in the heavily polluted lower parts of the valley. Measuring stations in the ...higher elevations on the mountains surrounding the valley are not available, which limits our understanding of the valley’s pollutant dynamics and hinders the effectiveness of data assimilation studies using chemical transport models such as LOTOS-EUROS. To address this gap in measurements, we have designed a new network of low-cost sensors to be installed at altitudes above 2000 m.a.s.l. The network consists of custom-built, solar-powered, and remotely connected sensors. Locations were strategically selected using the LOTOS-EUROS model driven by diverse meteorology-simulated fields to explore the effects of the valley wind representation on the transport of pollutants. The sensors transmit collected data to internet gateways for posterior analysis. Various tests to verify the critical characteristics of the equipment, such as long-range transmission modeling and experiments with an R score of 0.96 for the best propagation model, energy power system autonomy, and sensor calibration procedures, besides case exposure to dust and water experiments, to ensure IP certifications. An inter-calibration procedure was performed to characterize the sensors against reference sensors and describe the observation error to provide acceptable ranges for the data assimilation algorithm (<10% nominal). The design, installation, testing, and implementation of this air quality network, oriented towards data assimilation over the Aburrá Valley, constitute an initial experience for the simulation capabilities toward the system’s operative capabilities. Our solution approach adds value by removing the disadvantages of low-cost devices and offers a viable solution from a developing country’s perspective, employing hardware explicitly designed for the situation.
Quantum dots (QDs) confer a wide range of optical properties to pigments/inks. With new products and applications entering the market, the airborne emissions of QDs-incorporating inks during usage ...stage at consumer scale (e.g. household printing) and their corresponding impacts towards human health and the environment need to be investigated. In the present work Cadmium Telluride (CdTe) QDs have been selected as a case study. The targets of this study comprise: (i) the characterization under controlled conditions of the emissions during inkjet printing of a prototype of a CdTe QDs nanoadditivated ink and (ii) the assessment of the feasibility to derive human health and freshwater effect factors (EF) for potentially released CdTe QDs with the USEtox® consensus model. Mean particle size after 60 minutes inkjet printing corresponded to 59.52 nm. For human health EF calculation an extrapolation to the human EF of other nanomaterials has been proposed considering CdTe QDs’ specific surface area whereas for the calculation of the freshwater EF, few of the data available have revealed suitable. A generic constraint to calculate both EFs for CdTe QDs released throughout the life cycle of a product incorporating them is related to the absence of information corresponding to their specific (eco)toxicological impacts.
Even if it has been claimed that Life Cycle Assessment is an essential tool to analyze, evaluate, understand and manage the environmental and health impacts of nanotechnology, few studies incorporate ...characterization factors (CFs) for human toxicity and freshwater ecotoxicity accounting for the impacts of engineered nanomaterials (ENMs) beyond their manufacturing stage. The objective of the present work consisted in identifying the correspondence between the information required and outputs provided by the USEtox® consensus model (which is not nanospecific) and the SimpleBox4Nano model (which accounts for nanospecific processes, e.g. aggregation, attachment and dissolution for Fate Factor derivatization) in order to assess the possibility of integrating the two to derive size-dependent CFs for the varying sizes of ENMs throughout their life cycle. The possibility to combine and integrate the two models appeared to be limited since there is no absolute correspondence between the two of them.
Radiocarbon analysis is a widely-used tool for source apportionment of aerosol particles. One of the big challenges of this method, addressed in this work, is to isolate elemental carbon (EC) for 14C ...analysis. In the first part of the study, we validate a two-step method (2stepCIO) to separate total carbon (TC) into organic carbon (OC) and EC against the EUSAAR_2 thermal-optical method regarding the recovered carbon concentrations. The 2stepCIO method is based on the combustion of OC in pure oxygen at two different temperature steps to isolate EC. It is normally used with a custom-built aerosol combustion system (ACS), but in this project, it was also implemented as a thermal protocol on a Sunset OC-EC analyzer. Results for the recovered EC mass concentration showed poor agreement between the 2stepCIO method on the ACS system and on the Sunset analyzer. This indicates that the EC recovery is sensitive not only to the temperature steps, but also to instrument-specific parameters, such as heating rates. We also found that the EUSAAR_2 protocol itself can underestimate the EC concentration on untreated samples compared to water-extracted samples. This is especially so for highly loaded filters, which are typical for 14C analysis. For untreated samples, the EC concentration on long-term filter samples (two to five days sampling time) was 20–45% lower than the sum of EC found on the corresponding 24-h filter samples. For water-extracted filter samples, there was no significant difference between long-term and the sum of daily filter samples. In the second part of this study, the 14C was measured on EC isolated by the 2stepCIO method and compared to methods from two other laboratories. The different methods agree well within their uncertainty estimates.
Satellite-based aerosol optical depth (AOD) has gained popularity as a powerful data source for calibrating aerosol models and correcting model errors through data assimilation. However, simulated ...airborne particle mass concentrations are not directly comparable to satellite-based AODs. For this, an AOD operator needs to be developed that can convert the simulated mass concentrations into model AODs. The AOD operator is most sensitive to the input of the particle size and chemical composition of aerosols. Furthermore, assumptions regarding particle size vary significantly amongst model AOD operators. More importantly, satellite retrieval algorithms rely on different size assumptions. Consequently, the differences between the simulations and observations do not always reflect the actual difference in aerosol amount.
Integrating nephelometers are widely used for monitoring and research applications related to air pollution and climate. Several commercial versions of the instrument are available and are in wide ...use in the community. This article reports on results from a calibration and intercomparison workshop where several units of the three most widely used nephelometer models were tested with respect to their CO
2
calibration accuracy and stability and non-idealities of their angular illumination function. Correction factors that result from the non-ideal illumination due to truncation of the sensing volumes in the near-forward and near-backward angular ranges and for non-Lambertian illumination from the light sources are presented, in particular for two models that have not previously been tested in this respect. The correction factors ranged from 0.95 to 1.15 depending on the model of nephelometer and aerosol size distribution. Recommendations for operational data analysis in context of these and previous performance tests are presented.
Vertical profiles of the aerosol particles hygroscopic properties, their mixing state as well as chemical composition were measured above northern Italy and the Netherlands. An aerosol mass ...spectrometer (AMS; for chemical composition) and a white-light humidified optical particle spectrometer (WHOPS; for hygroscopic growth) were deployed on a Zeppelin NT airship within the PEGASOS project. This allowed one to investigate the development of the different layers within the planetary boundary layer (PBL), providing a unique in situ data set for airborne aerosol particles properties in the first kilometre of the atmosphere. Profiles measured during the morning hours on 20 June 2012 in the Po Valley, Italy, showed an increased nitrate fraction at ∼ 100 m above ground level (a.g.l.) coupled with enhanced hygroscopic growth compared to ∼ 700 m a. g. l. This result was derived from both measurements of the aerosol composition and direct measurements of the hygroscopicity, yielding hygroscopicity parameters (κ) of 0.34 ± 0.12 and 0.19 ± 0.07 for 500 nm particles, at ∼ 100 and ∼ 700 m a. g. l., respectively. The difference is attributed to the structure of the PBL at this time of day which featured several independent sub-layers with different types of aerosols. Later in the day the vertical structures disappeared due to the mixing of the layers and similar aerosol particle properties were found at all probed altitudes (mean κ ≈ 0.18 ± 0.07). The aerosol properties observed at the lowest flight level (100 m a. g. l.) were consistent with parallel measurements at a ground site, both in the morning and afternoon. Overall, the aerosol particles were found to be externally mixed, with a prevailing hygroscopic fraction. The flights near Cabauw in the Netherlands in the fully mixed PBL did not feature altitude-dependent characteristics. Particles were also externally mixed and had an even larger hygroscopic fraction compared to the results in Italy. The mean κ from direct measurements was 0.28 ± 0.10, thus considerably higher than κ values measured in Italy in the fully mixed PBL.
Official air quality monitoring networks are often scarce and unevenly spatially distributed. In recent years, the use of low-cost sensors next to official networks is increasing. These additional ...networks provide measurements of high spatial and temporal resolution and potentially reveal patterns and emissions sources that are hard to detect with conventional methods. In this work, the data assimilation method implemented around the LOTOS-EUROS chemistry transport model is employed to assimilate measurements from heterogenous low-cost sensor networks around the city of Eindhoven in the Netherlands in November 2021. Three data assimilation experiments are performed and evaluated against a free run of the model. In the first one, measurements from the low-cost Innovatief Lucht Meetsysteem (ILM) network are exploited. In the second one, the citizen science network SamenMeten is used and in the third one, a combination of both datasets is applied. In the assimilation experiments at a domain around the city of Eindhoven, it is shown to be essential to use boundary conditions from an assimilation on a larger domain to account for the variability in pollution that originates from sources outside the domain of interest. Such an improvement in boundary conditions counts for a decrease in the initial free run negative biases of 45% for PM10 and 23% for PM2.5 in the city of Eindhoven. The assimilation of low-cost measurements in the region after the correction of the boundary conditions decreases the absolute PM10 biases in the 3 independent official stations over the city of Eindhoven further from −4.4 μg m−3 to about 0.8 μg m−3 averaged over the three experiments. Also, the correlation coefficient is increased from 0.75 to 0.89 and the normalized root mean square is decreased from 0.47 to 0.25. We conclude that the improved boundary conditions and assimilation of observations from dense low-cost networks are able to improve the LOTOS-EUROS simulations at urban scale.
Display omitted
•Assimilation of particulate matter measurements over Eindhoven area in the Netherlands using low-cost sensors.•Impoved PM10 and PM2.5 simulations over Eindhoven using measurements from official and low-cost networks.•Updated PM emissions estimated from the assimilation experiments are higher than the a priori emissions.•Assimilations of PM suggest changes in temporal profiles of updated emissions.
PDF
