Receptor modelling of secondary and carbonaceous particulate matter at a southern UK site
Complementary approaches have been taken to better understand the sources and their spatial distribution for secondary inorganic (nitrate and sulphate) and secondary or- ganic aerosol sampled at a rural site (Harwell) in the southern United Kingdom. A concentration field map method was ap- plied to 1581 daily samples of chloride, nitrate and sulphate from 2006 to 2010, and 982 samples for organic carbon and elemental carbon from 2007 to 2010. This revealed a rather similar pattern of sources for nitrate, sulphate and secondary organic carbon within western/central Europe, which in the case of nitrate, sulphate, organic carbon and secondary or- ganic carbon, correlated significantly with EMEP emissions maps of NOx, SO2, and VOC respectively. A slightly more southerly source emphasis for secondary organic carbon may reflect the contribution of biogenic sources. Trajectory clus- ters confirm this pattern of behaviour with a major contri- bution from mainland European sources. Similar behaviours of, on the one hand, sulphate and organic carbon and, on the other hand, EC and nitrate showed that the former are more subject to regional influence than the latter in agreement with the slower atmospheric formation of sulphate and secondary organic aerosol than for nitrate, and the local/mesoscale in- fluences upon primary EC. However, careful analysis of back trajectories and Concentration Field Maps indicates a strong contribution of mainland European sites to EC concentra- tions at Harwell. In a separate study, measurements of sul- phate, nitrate, elemental and organic carbon were made in 100 simultaneously collected samples at Harwell and at a Geoscientific suburban site in Birmingham (UK). This showed a significant Instrumentation correlation in concentrations between the two sites for all of Methods and the secondary constituents, further indicating secondary or- Data Systems Open Access ganic aerosol to be a regional pollutant behaving similarly to sulphate and nitrate.