Modelling secondary inorganic aerosol over the Netherlands during an episode of peak concentrations

Abstract

Air pollution is one of the largest environmental health risks both worldwide as well as in the Netherlands. The main contribution to air pollution in the Netherlands comes from aerosol (particulate matter), which consists of fine solid or liquid particles suspended in the air. Secondary inorganic aerosol (SIA) makes up the largest part of particulate matter pollution. High particulate matter concentrations present a health risk as inhaled particles can penetrate deep into the lungs. Aerosol chemistry is modelled here with the atmospheric chemistry and transport model WRF-Chem. This is done for high resolution domains focused on the Netherlands. A one month period between 10 January 2010 and 10 February 2010 with high observed peaks in SIA concentrations is studied. Boundary and initial conditions for meteorological and chemical parameters are taken from external data sets and models. Emissions of SIA precursor gases are based on data from the European Centre on Emission Inventories and Projections and the Dutch Pollutant Release and Transfer Register. Results show that the WRF-Chem model underestimates SIA concentrations by 40 %, in line with results from other models. Modelled temporal variations in SIA concentrations generally match those found in the measurements. Two of the three peaks in SIA concentrations observed during the study period are also present in the model results. The other peak is strongly underestimated, likely due to an overestimation of modelled wind speeds at the time preventing the accumulation of pollutants in the air. Temporal variations in the nitrate and ammonium concentrations are better captured by the model than those in the sulfate concentrations. Sensitivity calculations show that reducing Dutch NOx emissions is most effective towards reducing SIA concentrations, but reducing SO2 or NH3 emissions is also beneficial. Simulation of the European emission reductions for 2030 from the 2016 NEC Directive indicates that the goal of decreasing the negative health effects of particulate matter pollution by 50 % may be obtained for the SIA fraction of particulate matter.