Stable carbon and nitrogen isotope ratio in PM1 and size segregated aerosol particles over the Baltic Sea

Abstract

We analysed δ¹³C of total carbon (TC) and δ¹⁵N of total nitrogen (TN) in submicron (PM₁) and size segregated aerosol particles (PM_0.056–2.5) collected during a cruise in the Baltic Sea from 9 to 17 November 2012. PM₁ were characterized by the highest δ¹³C (–26.4‰) and lowest δ¹⁵N (–0.2 and 0.8‰) values when air masses arrived from the southwest direction (Poland). The obtained δ¹³C values indicated that combined emissions of coal and diesel/gasoline combustion were the most likely sources of TC. The depleted δ¹⁵N values indicated that TN originated mainly from liquid fuel combustion (road traffic, shipping) during this period. The lowest δ¹³C and highest δ¹⁵N values were determined in PM₁ samples during the western airflow when the air masses had no recent contact with land. The highest δ¹⁵N values were probably associated with chemical aging of nitrogenous species during long-range transport, the lowest δ¹³C values could be related to emissions from diesel/gasoline combustion, potentially from ship traffic. The δ¹³C analysis of size-segregated aerosol particles PM_0.056–2.5 revealed that the lowest δ¹³C values were observed in the size range from 0.056 to 0.18 µm and gradual ¹³C enrichment occurred in the size range from 0.18 to 2.5 µm due to different sources or formation mechanisms of the aerosols.