Harmful effects of diesel emissions can be investigated via exposures of human epithelial cells, but most of previous studies have largely focused on the use of diesel particles or emission sources that are poorly representative of engines used in current traffic. We studied the cellular response of primary bronchial epithelial cells (PBECs) at the air-liquid interface (ALI) to the exposure to whole diesel exhaust (DE) generated by a Euro V bus engine, followed by treatment with UV-inactivated non-typeable Haemophilus influenzae (NTHi) bacteria to mimic microbial exposure. The effect of prolonged exposures was investigated, as well as the difference in the responses of cells from COPD and control donors and the effect of emissions generated during a cold start. HMOX1 and NQO1 expression was transiently induced after DE exposure. DE inhibited the NTHi-induced expression of human beta-defensin-2 (DEFB4A) and of the chaperone HSPA5/BiP. In contrast, expression of the stress-induced PPP1R15A/GADD34 and the chemokine CXCL8 was increased in cells exposed to DE and NTHi. HMOX1 induction was significant in both COPD and controls, while inhibition of DEFB4A expression by DE was significant only in COPD cells. No significant differences were observed when comparing cellular responses to cold engine start and prewarmed engine emissions.

A first direct intercomparison of aerosol vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations, performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) in summer 2009, is presented. Five out of 14 participants of the CINDI campaign reported aerosol extinction profiles and aerosol optical thickness (AOT) as deduced from observations of differential slant column densities of the oxygen collision complex (O4) at different elevation angles. Aerosol extinction vertical profiles and AOT are compared to backscatter profiles from a ceilometer instrument and to sun photometer measurements, respectively. Furthermore, the near-surface aerosol extinction coefficient is compared to in situ measurements of a humidity-controlled nephelometer and dry aerosol absorption measurements. The participants of this intercomparison exercise use different approaches for the retrieval of aerosol information, including the retrieval of the full vertical profile using optimal estimation and a parametrised approach with a prescribed profile shape. Despite these large conceptual differences, and also differences in the wavelength of the observed O4 absorption band, good agreement in terms of the vertical structure of aerosols within the boundary layer is achieved between the aerosol extinction profiles retrieved by the different groups and the backscatter profiles observed by the ceilometer instrument. AOTs from MAX-DOAS and sun photometer show a good correlation (R>0.8), but all participants systematically underestimate the AOT. Substantial differences between the near-surface aerosol extinction from MAX-DOAS and from the humidified nephelometer remain largely unresolved.

Intensive measurements of submicron aerosol particles and their chemical composition were performed with an Aerosol Chemical Speciation Monitor (ACSM) at the Cabauw Experimental Site for Atmospheric Research (CESAR) in Cabauw, the Netherlands, sampling at 5 m height above ground. The campaign lasted nearly 1 year from July 2012 to June 2013 as part of the EU-FP7-ACTRIS project (Q-ACSM Network). Including equivalent black carbon an average particulate mass concentration of 9.50 µg m−3 was obtained during the whole campaign with dominant contributions from ammonium nitrate (45 %), organic aerosol (OA, 29 %), and ammonium sulfate (19 %). There were 12 exceedances of the World Health Organization (WHO) PM2.5 daily mean limit (25 µg m−3) observed at this rural site using PM1 instrumentation only. Ammonium nitrate and OA represented the largest contributors to total particulate matter during periods of exceedance. Source apportionment of OA was performed season-wise by positive matrix factorization (PMF) using the multilinear engine 2 (ME-2) controlled via the source finder (SoFi). Primary organic aerosols were attributed mainly to traffic (8–16 % contribution to total OA, averaged season-wise) and biomass burning (0–23 %). Secondary organic aerosols (SOAs, 61–84 %) dominated the organic fraction during the whole campaign, particularly on days with high mass loadings. A SOA factor which is attributed to humic-like substances (HULIS) was identified as a highly oxidized background aerosol in Cabauw. This shows the importance of atmospheric aging processes for aerosol concentration at this rural site. Due to the large secondary fraction, the reduction of particulate mass at this rural site is challenging on a local scale.

Large networks of expensive instruments are often used to independently quantify and monitor urban CO2 emissions with sufficient level of detail. However, many developing regions cannot afford such a monitoring effort. We explore the use of a simple, less costly method to constrain urban emissions using only two measurement sites, one upwind and one downwind of the city of Rotterdam in the Netherlands. This provides an interesting dataset of concentration gradients of multiple combustion tracers over an urban-industrial complex. We find clear emission signals from three source sectors, mainly related to industrial activities in the port and from residential areas. We estimate the anthropogenic CO2 emissions for three footprints from our observations and find them in reasonable agreement with the Dutch National Emission Registration (NER) database after accounting for biogenic fluxes. The large confidence interval for one of the footprints illustrates that the presence of point sources complicates the flux estimates. Additionally, we were able to pinpoint a limitation in the emission database using observed fossil fuel CO:CO2 ratios, although the applicability of this method is limited for the footprint with a large influence from point source emissions. There is also a large variability in the observed ratios per footprint, which indicates that the dominant source type varies over time. Finally, we show that the fossil fuel CO concentration can be used to calculate fossil fuel CO2 if their emission ratio is well-known.

This study aims to quantify the impact of black carbon from inland shipping on air quality, expressed as elemental carbon (EC) near inland waterways in The Netherlands. Downwind measurements of particle numbers and EC were used to establish emission factors for EC from inland shipping using inverse modelling. These emission factors were combined with data on energy consumption to derive annual average emissions rates for all Dutch waterways. A line source model was applied to compute the contribution of inland shipping to annual average EC concentrations for around 140,000 people living within 200 m of busy waterways in The Netherlands. The results showed that they are exposed to additional EC concentrations of up to 0.5 μg EC per m3 depending on the shipping volume and distance from the waterway. In view of the envisaged growth in water transport, this underlines the need to reduce combustion emissions from inland shipping. Targeting “gross” polluters may be the most effective approach since 30% of ships cause more than 80% of the total emissions.

From June to July 2009 more than thirty different in-situ and remote sensing instruments from all over the world participated in the Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The campaign took place at KNMI’s Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands. Its main objectives were to determine the accuracy of state-ofthe-art ground-based measurement techniques for the detection of atmospheric nitrogen dioxide (both in-situ and remote sensing), and to investigate their usability in satellite data validation. The expected outcomes are recommendations regarding the operation and calibration of such instruments, retrieval settings, and observation strategies for the use in ground-based networks for air quality monitoring and satellite data validation. Twenty-four optical spectrometers participated in the campaign, of which twenty-one had the capability to scan different elevation angles consecutively, the so-called Multi-axis DOAS systems, thereby collecting vertical profile information, in particular for nitrogen dioxide and aerosol. Various in-situ samplers and lidar instruments simultaneously characterized the variability of atmospheric trace gases and the physical properties of aerosol particles. A large data set of continuous measurements of these atmospheric constituents has been collected under various meteorological conditions and air pollution levels. Together with the permanent measurement capability at the CESAR site characterizing the meteorological state of the atmosphere, the CINDI campaign provided a comprehensive observational data set of atmospheric constituents in a highly polluted region of the world during summertime. First detailed comparisons performed with the CINDI data show that slant column measurements of NO 2, O4 and HCHO with MAX-DOAS agree within 5 to 15 %, vertical profiles of NO2 derived from several independent instruments agree within 25 % of one another, and MAX-DOAS aerosol optical thickness agrees within 20–30 % with AERONET data. For the in-situ NO2 instrument using a molybdenum converter, a bias was found as large as 5 ppbv during day time, when compared to the other in-situ instruments using photolytic converters.

The development of a radiation fog layer at the Cabauw Experimental Site for Atmospheric Research (51.97 degrees N, 4.93 degrees E) on 23 March 2011 was observed with ground-based in situ and remote sensing observations to investigate the relationship between visibility and radar reflectivity. The fog layer thickness was less than 200 m. Radar reflectivity values did not exceed -25 dBZ even with visibilities less than 100 m. The onset and evaporation of fog produce different radar reflectivity-visibility relationships. The evolution of the fog layer was modeled with a droplet activation model that used the aerosol size distribution observed at the 60-m altitude tower level as input. Radar reflectivity and visibility were calculated from model drop size spectra using Mie scattering theory. Since radiative cooling rates are small in comparison with cooling rates due to adiabatic lift of aerosol-laden air, the modeled supersaturation remains low so that few aerosol particles are activated to cloud droplets. The modeling results suggest that the different radar reflectivity-visibility relationships are the result of differences in the interplay between water vapor and cloud droplets during formation and evaporation of the fog. During droplet activation, only a few large cloud droplets remain after successfully competing for water vapor with the smaller activated droplets. These small droplets eventually evaporate (deactivate) again. In the fog dissolution/evaporation stage, only these large droplet need to be evaporated. Therefore, to convert radar reflectivity to visibility for traffic safety products, knowledge of the state of local fog evolution is necessary.

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH<30–40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties – especially the aerosol light scattering – are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol scattering coefficient σsp(λ) was measured dry and at various, predefined RH conditions between 20 and 95% with a humidified nephelometer. The scattering enhancement factor f(RH,λ) is the key parameter to describe the effect of RH on σsp(λ) and is defined as σsp(RH,λ) measured at a certain RH divided by the dry σsp(dry,λ). The measurement of f(RH,λ) together with the dry absorption measurement (assumed not to change with RH) allows the determination of the actual extinction coefficient σep(RH,λ) at ambient RH. In addition, a wide range of other aerosol properties were measured in parallel. The measurements were used to characterize the effects of RH on the aerosol optical properties. A closure study showed the consistency of the aerosol in-situ measurements. Due to the large variability of air mass origin (and thus aerosol composition) a simple parameterization of f(RH,λ) could not be established. If f(RH,λ) needs to be predicted, the chemical composition and size distribution need to be known. Measurements of four MAX-DOAS (multi-axis differential optical absorption spectroscopy) instruments were used to retrieve vertical profiles of σep(λ). The values of the lowest layer were compared to the in-situ values after conversion of the latter ones to ambient RH. The comparison showed a good correlation of R2 = 0.62–0.78, but the extinction coefficients from MAX-DOAS were a factor of 1.5–3.4 larger than the in-situ values. Best agreement is achieved for a few cases characterized by low aerosol optical depths and low planetary boundary layer heights. Differences were shown to be dependent on the applied MAX-DOAS retrieval algorithm. The comparison of the in-situ extinction data to a Raman LIDAR (light detection and ranging) showed a good correlation and higher values measured by the LIDAR (R2 = 0.82−0.85, slope of 1.69–1.76) if the Raman retrieved profile was used to extrapolate the directly measured extinction coefficient to the ground. The comparison improved if only nighttime measurements were used in the comparison (R2 = 0.96, slope of 1.12).

Atmospheric aerosol particles affect the Earth's radiative balance both in the cloud-free and the cloudy atmosphere. The direct effect of aerosols is related with scattering and absorption of solar radiation, and as a consequence, reduction of the amount of radiation reaching the surface. The best parameter that quantifies this effect is the aerosol extinction, which can be derived from vertical, as well as, horizontal measurements. The purpose of this paper is to compare the aerosol optical properties registered by two types of instruments. The first is a standard 5-wavelength hand-held sun photometer yielding the vertical column extinction, the second a 7-wavelength transmissometer developed at TNO. This multi-band transmissometer provides horizontal, path-integrated transmission data at 7 wavelengths within the visible/infra red spectral range. The data used in the comparison were collected during an experiment near Scripps Pier in La Jolla near Sail Diego, in November 2006.

Sun photometer measurements at the AERONET station at the North Sea coast in The Hague (The Netherlands) provide a climatology of optical and physical aerosol properties for the area. Results are presented from the period January 2002 to July 2003. For the analysis and interpretation these data are coupled to chemical aerosol data from a nearby station of the Dutch National Air Quality Network. This network provides PM10 and black carbon concentrations. Meteorological conditions and air mass trajectories are also used. Due to the location close to the coast, the results are strongly dependent on wind direction, i.e. air mass trajectory. In general the aerosol optical properties are governed by industrial aerosol emitted form various industrial, agricultural and urban areas surrounding the site in almost all directions over land. For maritime air masses industrial aerosols are transported from over the North Sea, whereas very clean air is transported from the NW in clean polar air masses from the North Atlantic. In the winter the effect of the production of sea salt aerosol at high wind speeds is visible in the optical and physical aerosol data. In these cases fine and coarse mode radii are similar to those reported in the literature for marine aerosol. Relations are derived between the Ångström coefficients with both the fine/coarse mode fraction and the ratio of black carbon and PM10.

In an earlier paper [1], data from our Multi-Band Radiometer Transmissometer (MSRT) were used to compare the ratio of extinction coefficients in different spectral bands during periods of changing visibility conditions. This ratio is an indication of the characteristics and origin (eg rural or maritime) of the haze- or fog particles, present in the measurement path. In this paper we will analyze the VAMPIRA transmission data in more detail by separating the contributions due to molecular extinction, scattering and (potentially) refraction. In our analysis we take the contribution due to scattering in order to obtain the characteristics of the Particle Size Distribution (PSD). For this purpose we take the average value and the slope of the measured transmission level in two neighboring spectral bands. Via a special simulation tool, developed for Junge-type PSD's, the slope of the PSD (defined: Junge exponent) and its value at a particle diameter of I gm (Junge coefficient) can be determined via a set of retrieval steps. Reference is made to a similar approach [2] where in stead of a Junge distribution, three contiguous lognormal distributions are taken. The associated procedure for the Junge-type PSD is explained in detail in this paper and applied to the VAMPIRA transmission data. The versatility of the new retrieval method is demonstrated, especially when wavelengths around I pm are chosen (a somewhat higher number than the diameter of the majority of the particles, so that most of the scattering is in the so-called Rayleigh regime). It is obvious, that the method fails in conditions of dense fog, when the transmission levels (average value and slope) over the 8.6 km path approach zero. The results are compared with in-situ PSD measurements, carried out simultaneously with a PMS (Particle Measurement System) probe at the pier near the Surendorf shore station. In many conditions different results appear due to the fact that the MSRT system delivers path integrated data, while the PMS probe measures locally in a small volume. The MSRT data, collected over an overseas path, are more relevant to be used in the data analysis of the shore based sensor systems [3], measuring simultaneously signal values of distant point targets. The MSRT system has a higher signal to noise ratio and due to the shorter time constant, rapid fluctuations in particle characteristics are observed, not measured by the PMS probe. The availability of reliable aerosol characteristics (i.e. Junge exponent and -coefficient) allows a more precise interpretation of the data from the surveillance systems.

A first version of the integrated model EOSTAR (Electro-Optical Signal Transmission and Ranging) to predict the performance of electro-optical (EO) sensor systems in the marine atmospheric surface layer has been developed. The model allows the user to define camera systems, atmospheric conditions and target characteristics, and it uses standard (shipboard) meteorological data to calculate atmospheric effects such as refraction, turbulence, spectrally resolved transmission, path- and background radiation. Alternatively, the user may specify vertical profiles of meteorological parameters and/or profiles of atmospheric refraction, either interactively or in data files with a flexible format. Atmospheric effects can be presented both numerically and graphically as distorted images of synthetically generated targets with spatially distributed emission properties. EOSTAR is a completely mouse-driven PC Windows program with a user-friendly interface and extended help files. Most calculations are performed in real-time, although spectral transmission and background radiation calculations take up to a few seconds for each new meteorological condition. The program can be used in a wide range of applications, e.g., for operational planning and instruction.

The application of long-range infrared observation systems is challenging, especially with the currently available high spatial resolution infrared camera systems with resolutions comparable with their visual counterparts. As a result of these developments, the obtained infrared images are no longer limited by the quality of system but by atmospheric effects instead. For instance, atmospheric transmission losses and path radiance reduce the contrast of objects in the background and optical turbulence limits the spatial resolution in the images. Furthermore, severe image distortion can occur due to atmospheric refraction, which limits the detection and identification of objects at larger range. EOSTAR is a computer program under development to estimate these atmospheric effects using standard meteorological parameters and the properties of the sensor. Tools are provided to design targets and to calculate their infrared signature as a function of range, aspect angle, and weather condition. Possible applications of EOSTAR include mission planning, sensor evaluation and selection, and education. The user interface of EOSTAR is fully mouse-controlled, and the code runs on a standard Windows-based PC. Many features of EOSTAR execute almost instantaneous, which results in a user friendly code. Its modular setup allows its configuration to specific user needs and provides a flexible output structure.

Scattering by atmospheric aerosols is one of the environmental parameters determining the range performance of optical and infrared sensors. Extinction of the target contrast along the path due to scattering is difficult to estimate in real operational conditions due to uncertainties in the size distribution of the particles, their constitution and concentration along the path. Knowledge on their behaviour allows calculation of the atmospheric transmission by means of standard scattering formulae. In-situ measurement of the characteristics of the particles by means of counters provides data of limited value due to the possible impact of the direct environment. The data may also be not representative for the particles at other locations along the path. Similarly the measurement of the particle characteristics by means of LIDAR provide an asymmetric view, while the backscatter by the particles is difficult to translate into extinction coefficients in forward direction. Multi-band transmissometry along the path of interest provides however direct information on the real atmospheric propagation characteristics. Furthermore the multi-band data allow the validation of the aerosol model, to be used in transmission models such as MODTRAN. The VAMPIRA trials, organised in March/April 2004 by Germany in the Baltic Sea near Echernforde, provided an opportunity to test the usefulness of a 7-channel optical/IR transmissometer, developed at TNO-FEL. In this paper the set-up of the system is desribed and samples of data are presented. The multi-band transmission data, collected over an 8.6 km path over water, are compared with extinction values obtained from in-situ particle measurements. The data show clearly that the aerosols have rural characteristics during most of the time.