PM and mass closure

Example of modelled PM10 (left), and measured versus modelled PM10 (right) in the Netherlands
The quality of the air is under considerable threat, and particulate matter (PM) poses part of this threath to our health. The variations in natural PM concentrations across time and space, however, are rather uncertain. This is partly caused by the lack or only poor inclusion of description of these PM fractions in air quality models. For the Netherlands, the current models underestimate the PM10 concentrations by about 40 to 50%. For proper assessment of PM levels, understanding of the underlying mechanisms, and ultimately, for regulatory purposes, closing this gap of uncertainty in the models is indispensable.
PM modelling for the Netherlands
Recently, the LOTOS-EUROS model has been further developed to close in on the gap of the current knowledge of PM by including (improved) parameterisations for several of the natural and anthropogenic PM compounds and through the coupling of global air quality model TM5 and LOTOS EUROS. This was work partly conducted under auspices of the Netherlands Research Programme on Particulate matter (BOP)a national programme on PM10 and PM2.5, funded by the Netherlands Ministry of Housing, Spatial planning and the Environment (VROM).
BOP Project
The goal of the BOP programme is to reduce uncertainties about PM and the number of policy dilemmas, which complicate development and implementation of adequate policy measures. BOP is a framework of cooperation, involving four Dutch institutes: the Energy Research Centre of the Netherlands (ECN), the Netherlands Environmental Assessment Agency (PBL), the Environment and Safety Division of the National Institute for Public Health and the Environment (RIVM), and TNO. The four instititues collaborated on an approach for dealing with these objectives, by means of integration of mass and composition measurements of PM10 and PM2.5, model development. Within BOP, TNO provided in a first effort for a modelling framework for PM components
  • sea salt
  • soil dust
  • secondary organic particles from natural sources
for use in the LOTOS-EUROS.
Sea salt aerosol makes a natural contribution to particulate matter (PM10) and cannot be influenced by abatement strategies. In the Netherlands the sea salt contribution is subtracted from PM10 according European regulations when checking compliance to PM10 limit values. Within BOP, the model description was updated to the combination of emission parameterisations that are considered to be state-of-the-art. The BOP measurements and the efforts to compile foreign data have provided in the first opportunity for a more extensive validation. For the Netherlands, one year of sodium measurements, which is a good indicator for sea salt, was combined with new results from the LOTOS-EUROS model, for an improved insight on sea salt and its contribution to PM10 and PM2.5 in the Netherlands.
Soil dust
Contribution of traffic (re)suspension (CM) to PM10 in 2005
Crustal material or soil particles typically contribute between 5 and 20% to the ambient PM10 mass. Despite the importance of crustal material in total PM10 mass, the sources are still scarcely understood and not (well) represented in emission inventories or air quality models. Within BOP a methodology was designed to check firstorder estimates of various source strengths in Europe and in the Netherlands, in particular. Simple and therefore transparent emission functions for were developed for the following three sources:
  • wind erosion
  • (re-)suspension by traffic
  • (re-)suspension by agricultural land management
Additionally the impact of desert dust was checked by application of desert dust boundary conditions (inferred from the global TM5 model).
Carbonaceous Material
Chemistry transport models underestimate the concentrations of carbonaceous material. Secondary organic aerosol (SOA) may contribute significantly to the observed OC levels. However, due to the complex nature of the formation and behavior of both biogenic and anthropogenic organic aerosol (SOA), the present models still lack their inclusion.
Mayor anthropogenic emissions are concentrated in several areas/countries, and in large areas within Europe the biogenic emissions dominate over anthropogenic emissions. Moreover, current knowledge indicates that biogenic VOCs are more efficient at forming secondary organic aerosol than those of anthropogenic origin. Hence, state-of-the-art biogenic emission parameterisations are essential input to models for assessing their influence on SOA and O3 formation.
Within BOP, the modelling of biogenic volatile organic carbon emissions was improved for a better description of the formation of secondary organic aerosol (SOA) in the LOTOS-EUROS model.
Modelling of PM properties
The simulation of particulate matter requires continous research on how to describe the aersol properties in a realistic and computational efficient way. One of the implementation tested in LOTOS-EUROS uses the 'M7' description.