Attributing the influence of urban and industrial nitrous oxide emission sources on atmospheric concentrations measured at surface monitoring stations. A case study from Central Europe (Poland).

Abstract:

A regional study of the source-receptor relationship is analysed between the strong anthropogenic sources of nitrous oxide and the concentrations of this gas measured at two surface stations of distinct characteristics: urban (represented by Kraków station - KRK) and clean environment (high-mountain station Kasprowy Wierch - KAS). A long-term records of N₂O mixing ratios at both stations (2012-2014) provide the necessary statistics and temporal patterns. To achieve that purpose, a modeling framework has been established that utilizes the Stochastic Time-Inverted Lagrangian Model (STILT), driven by the meteorological fields from the Integrated Forecasting System and coupled to the IER hourly emission database.. The framework allowed spatial source apportionment of the nitrous oxide loads measured at both stations. The influences of the most important regional sources of N₂O have been analyzed, including Krakow agglomeration (waste, transport and power production) and chemical plant (nitric acid and caprolactam production), located ca. 100 km east of Krakow. The relative enhancement of these sources were analyzed against the reference scenario (all available European emission sources) and against the regional total.

The results have shown significant differences in the station characteristics, with very small enhancements of N₂O concentrations predicted for Kasprowy Wierch (maximum 2 ppb). For Kraków, the predicted concentrations were higher (close to 2 ppb monthly median). Influence of the sources located in Małopolska have been shown to be in the range of 20% - 80% with a temporal variability on daily and seasonal scales.

 The predictions of the model were validated against in-situ observations performed at both stations, pointing to possible misattribution of the local sources in Kraków.