A new approach to estimate pollutant emissions based on trajectory modeling and its application in the North China Plain

Abstract

Emission information is crucial for air quality modeling and air quality management. In this study, a new approach based on the understanding of the relationship between emissions and measured pollutant concentrations has been proposed to estimate pollutant emissions and source contributions. The retrieval can be made with single point in-situ measurements combined with backward trajectory analyses. The method takes into consideration the effect of planetary boundary layer height on pollutant mixing and transport. It is independent of energy statistics and therefore can provide frequent updates on emission information. The spatial coverage can be further improved by using measurements from several sites and combining the derived emission fields. The method was applied to yield the source distributions of black carbon (BC) and CO in the North China Plain (NCP) using in-situ measurements from the HaChi (Haze in China) Campaign and to evaluate contributions from specific areas to local concentrations at the measurement site.Results show an emission field for the NCP that is comparable to the INTEX-B inventory can be retrieved and directly applied to quantify areal source contributions. Compared to emissions in 2006, increased CO and BC emissions were found. Uncertainty analyses show that in-situ measurements of CO and BC bear errors below 0.1 ppm and 12%, respectively. WRF model underestimates the PBLH under stable conditions. On average, an error of 1% in the modeled PBLH results in 1% variation in the derived emissions. The trajectory displacement errors are mostly within 1.5 times the grid size.