Stable N isotope ratio in airborne total suspended particles and precipitation in Uljin from the East Sea

Abstract

The N isotopic values in the anthropogenic sources are relatively conserved in the NO3- formed in the airborne total suspended particles (TSP) and precipitation because photochemical processes in the atmosphere are not involved to N atoms.Thus, the direct analyses of δ15N-NO3- values in the TSP and precipitation formed in the atmosphere are potentially useful measures of identifying the sources and seasonal variations for atmospheric anthropogenic N (NANTH). In our research, the δ15N-NO3- values in TSP and precipitation samples collected from the Uljin station adjacent to the East Sea for three years were analyzed. The results indicated that the highest values for δ15N-NO3- (average of 8.59 ± 0.54‰ for TSP and 3.38 ± 1.5‰ for precipitation) were observed in winter (November to February) with the highest dry deposition rates for NOx (including NO3- and NO2- the average of 3.08 ± 0.12 mmol m-2 month-1) were observed for winter. The 66% of the wind routes passed through the polluted air masses from the northeastern China that was the populated cities under the influences of coal combustion and biomass burning for domestic winter heating. Contrary to winter trend, the lowestvalue δ15N-NO3- (average of 1.47 ± 0.9‰ for TSP) was observed for summer in TSP samples with the lowest dry deposition rate for NOx (average of 0.97 ± 0.33 mmol m-2 month-1). Most of the wind direction blowing to the Uljin station for s