Illustrating the benefit of using hourly monitoring data on secondary inorganic aerosol and its precursors for model evaluation

Abstract

Abstract. Secondary inorganic aerosol, most notably ammonium nitrate and ammonium sulphate, is an important contributor to ambient particulate mass and provides a means for long range transport of acidifying components. The modelling of the formation and fate of these components is challenging. Especially, the formation of the semi-volatile ammonium nitrate is strongly dependent on ambient conditions and the precursor concentrations. For the first time an hourly artefact free data set from the MARGA instrument is available for the period of a full year (1 August 2007 to 1 August 2008) at Cabauw, the Netherlands. This data set is used to verify the results of the LOTOS-EUROS model. The comparison showed that the model underestimates the SIA levels. Closer inspection revealed that base line values appear well estimated for ammonium and sulphate and that the underestimation predominantly takes place at the peak concentrations. For nitrate the variability towards high concentrations is much better captured, however, a systematic relative underestimation was found. The model is able to reproduce many features of the intra-day variability observed for SIA. Although the model captures the seasonal and average diurnal variation of the SIA components, the modelled variability for the nitrate precursor gas nitric acid is much too large. It was found that the thermodynamic equilibrium module produces a too stable ammonium nitrate in winter and during night time in summer, whereas during the daytime in summer it is too unstable. We recommend to improve the model by verification of the equilibrium module, inclusion of coarse mode nitrate and to address the processes concerning SIA formation combined with a detailed analysis of the data set at hand. The benefit of the hourly data with both particulate and gas phase concentrations is illustrated and a continuaCorrespondence to: M. Schaap (martijn.schaap@tno.nl) tion of these measurements may prove to be very useful in future model evaluation and improvement studies. Based on our findings we propose to implement a monitoring strategy using three levels of detail within the Netherlands.

Role of ambient ammonia in particulate ammonium formation at a rural site in the North China Plain

“…As listed in Table 1, the concentration of NH 3 at the NCP rural site was lower than that reported at Asian and African urban sites such as Lahore (Pakistan; Biswas et al, 2008), Colonelganj (India; Behera and Sharma, 2010), and Cairo (Egypt; Hassan et al, 2013) but higher than those from other areas in China, Europe, and North America (Plessow et al, 2005;Yao et al, 2006;Lin et al, 2006;Walker et al, 2006;Hu et al, 2008;Meng et al, 2011Meng et al, , 2014Shen et al, 2011;Schaap et al, 2011;Makkonen et al, 2012;Behera et al, 2013;Gong et al, 2013;Li et al, 2014). For example, the NH 3 at the NCP rural site was higher than that found at the Shangdianzi regional background station in the NCP (Meng et al, 2011), Lin'an regional background station in the Yangtze River Delta (YRD) in eastern China (Meng et al, 2014), and the rural site in Beijing .…”

Semi-continuous gas and inorganic aerosol measurements at a Finnish urban site: comparisons with filters, nitrogen in aerosol and gas phases, and aerosol acidity

“…Yet another method that is based on the same principle is the Dionex Gas Particle Ion Chromatography (GPIC) system that measures concentrations of water-soluble inorganic aerosol constituents (Cl − , NO ) and their associated precursor gases (HCl, SO 2 , HNO 3 , NH 3 ) (Godri et al, 2009). The ability to measure both water-soluble aerosol and the precursor gas concentrations at a high time resolution has recently been shown to be especially valuable for evaluating models, for instance the secondary inorganic aerosol formation (Schaap et al, 2011) and the gas-aerosol partitioning of ammonium nitrate (Aan de Brugh et al, 2012).…”

Top‐down estimate of China's black carbon emissions using surface observations: Sensitivity to observation representativeness and transport model error

“…Through statistical analysis for both measured and modeled data points, Gilardoni et al [2011] pointed out that monthly or annual mean observations might not be suitable for evaluating BC modeling. Schaap et al [2011] illustrated that using observational data with higher temporal resolution (hourly data) generated more accurate model evaluation for secondary inorganic aerosols. Only two studies were found to use the hourly data [Hakami et al, 2005;Kondo et al, 2011b].…”