Matthias Karl

A study of new particle formation in the marine boundary layer over the central Arctic Ocean using a flexible multicomponent aerosol dynamic model

ABSTRACT Enhancement of number concentrations of particles with sizes less than 25 nm diameter has been frequently observed in the boundary layer over the central Arctic Ocean during summer. The sectional aerosol dynamics model for Marine Aerosol Formation (MAFOR) was applied to evaluate the capability of different nucleation mechanisms to reproduce nucleation events observed during three expeditions (1996, 2001 and 2008) onboard the Swedish icebreaker Oden. Model calculations suggest that a source rate of a condensable organic vapour (OV) of about 2×105 cm−3 s−1 is required to reproduce observed growth of nucleation mode particles. Nucleation rates predicted by the newly proposed combined sulphuric acid nucleation mechanism, which best described new particle formation in the Arctic, ranged from 0.04 to 0.1 cm−3 s−1. This mechanism additively combines ion-mediated nucleation and cluster activation, and treats condensation of OV without correction of the Kelvin effect. In several events, the simultaneous number enhancement of particles in the 20–50 nm size range remained unexplained by the nucleation mechanisms. This lends support to alternative theories such as the fragmentation of marine gels (≈200–500 nm diameter in size) by physical or chemical processes.

Modelling atmospheric oxidation of 2-aminoethanol (MEA) emitted from post-combustion capture using WRF-Chem

Carbon capture and storage (CCS) is a technological solution that can reduce the amount of carbon dioxide (CO2) emissions from the use of fossil fuel in power plants and other industries. A leading method today is amine based post-combustion capture, in which 2-aminoethanol (MEA) is one of the most studied absorption solvents. In this process, amines are released to the atmosphere through evaporation and entrainment from the CO2 absorber column. Modelling is a key instrument for simulating the atmospheric dispersion and chemical transformation of MEA, and for projections of ground-level air concentrations and deposition rates. In this study, the Weather Research and Forecasting model inline coupled with chemistry, WRF-Chem, was applied to quantify the impact of using a comprehensive MEA photo-oxidation sequence compared to using a simplified MEA scheme. Main discrepancies were found for iminoethanol (roughly doubled in the detailed scheme) and 2-nitro aminoethanol, short MEA-nitramine (reduced by factor of two in the detailed scheme). The study indicates that MEA emissions from a full-scale capture plant can modify regional background levels of isocyanic acid. Predicted atmospheric concentrations of isocyanic acid were however below the limit value of 1 ppbv for ambient exposure. The dependence of the formation of hazardous compounds in the OH-initiated oxidation of MEA on ambient level of nitrogen oxides (NOx) was studied in a scenario without NOx emissions from a refinery area in the vicinity of the capture plant. Hourly MEA-nitramine peak concentrations higher than 40 pg m(-3) did only occur when NOx mixing ratios were above 2 ppbv. Therefore, the spatial variability and temporal variability of levels of OH and NOx need to be taken into account in the health risk assessment. The health risk due to direct emissions of nitrosamines and nitramines from full-scale CO2 capture should be investigated in future studies.

A new flexible multicomponent model for the study of aerosol dynamics in the marine boundary layer

A new sectional aerosol dynamics model, MAFOR, was developed with the focus to study nucleation in the marine boundary layer. Novel aspects of the model are (1) flexibility in the treatment of gas phase chemistry, (2) treatment of liquid phase chemistry, which can be extended according to needs and (3) simultaneous calculation of number and mass concentration distributions of a multicomponent aerosol as functions of time. Comparison with well-documented aerosol models (MONO32 and AEROFOR), a comprehensive data set on gas phase compounds, aerosol size distribution and chemical composition obtained during theA OE-96 (Arctic Ocean Expedition, 1996)was used to evaluate the model. Dimethyl sulphide decay during advection of an air parcel over the Arctic pack ice was well captured by the applied models and predicted concentrations of gaseous sulphuric acid and methane sulphonic acid range up to 1.0 × 106 cm−3 and 1.8 × 106 cm−3, respectively. Different nucleation schemes were implemented in MAFOR which allow the simulation of new particle formation. Modelled nucleation rates from sulphuric acid nucleation via cluster activation were up to 0.21 cm−3 s−1 while those from ion-mediated nucleationwere below 10−2 cm−3 s−1. Classical homogeneous binary and ternary nucleation theories failed to predict nucleation over the central Arctic Ocean in summer.

Estimating domestic wood burning emissions of particulate matter in two Nordic cities by combining ambient air observations with receptor and dispersion models.

The major emission source of primary PM2 (5) in many Nordic countries is wood burning for domestic heating Though direct measurements of wood burning emissions are possible under controlled conditions, emission inventories for urban scale domestic heating are difficult to calculate and remain uncertain As an alternative method for estimating these emissions, this paper makes use of ambient air measurements chemical analysis of filter samples receptor models, dispersion models, and simple inverse modelling methods to infer the emission strengths A comparison of dispersion models with receptor models indicates that the dispersion models tend to overestimate the contribution from wood burning The inverse modelling results are found to agree with those from the receptor modelling Though both the receptor and inverse modelling point to an overestimation of the wood burning emissions of PM2 (5), it is not possible to assign this solely to errors in the emissions inventory as a dispersion model error can be significant It is recommended to improve plume rise and urban canopy meteorological descriptions in the dispersion models before these models are of sufficient quality to allow quantitative assessments of emission inventories

Source-Receptor and Inverse Modelling to quantify urban PARTiculate emissions (SRIMPART)

Airborne particulate matter (PM) is considered to be a significant health risk for humans. Yet, concentration levels in much of Europe still remain high. One of the major emission sources of primary PM2.5 (airborne particle matter with a diameter < 2.5 m) in Nordic countries is wood burning due to domestic heating. Unfortunately, emission inventories for wood burning are difficult to determine and there is a large uncertainty in the impact of these emissions on air quality. In SRIMPART we have applied independent methods to assess the contribution of wood burning to the total PM2.5 concentrations in three Nordic cities (Oslo, Lycksele and Helsinki). These methods include receptor modelling, based on chemical analysis of filter samples, and inverse modelling using dispersion models. The results show that estimates of emissions based on wood consumption or based on the methods applied in SRIMPART have a similar level of uncertainty and so it is not possible to categorically state which is the most correct. However, both methods do agree within their respective uncertainties and this provides support that the long term average emissions from wood burning are correct to within a factor of two.

The Impact of Emissions from Ships in Ports on Regional and Urban Scale Air Quality

Ships emit considerable amounts of pollutants, not only when sailing, but also during their stay in ports. This is of particular importance for harbor cities because ship emissions contribute to regional and urban air pollution. However, only few studies investigated the specific effect of shipping emissions on air pollution in cities. It is difficult to estimate the emissions from ships in harbors only from the technical specifications of the ships because their activities during their stay at berth differ a lot and are not well known. A multi-level approach was used to calculate the total emissions of ship activities in the port of Hamburg. The resulting emission inventory served as input for the Chemical Transport Model systems TAPM and CityChem. To investigate the impact of ship emissions on air pollution in the Hamburg area two different model runs for January and July 2013 were performed; one model run including land-based emissions and the ship emissions and a model run just including the land-based emissions. The modeling outcomes are compared with air quality data and resulted in dispersion maps of pollutants (PM2.5 and NO2) from harbor related ships in the Hamburg metropolitan area. On the urban scale, the highest concentrations are located in the port area of Hamburg. The monthly averaged NO2 concentrations mostly remain within the harbor area and the southwest region of Hamburg. The regional background concentrations in the metropolitan area are only slightly increased by shipping emissions from the harbor.