Urea: An important piece of Water Soluble Organic Nitrogen (WSON) over the Eastern Mediterranean

The role of atmospheric urea on the biogeochemical cycle of Water Soluble Organic Nitrogen (WSON) in the Eastern Mediterranean was assessed by collecting and analyzing wet and dry deposition samples and size segregated aerosols during a one year period (2006). In rain water volume weighted mean (VWM) concentration of urea was found equal to 5.5 μM. In atmospheric particles the average concentration of urea in coarse and fine mode was 0.9 ± 1.9 nmol N m− 3 (median 0.0 nmol N m− 3) and 2.2 ± 3.0 nmol N m− 3 (median 1.1 nmol N m− 3), respectively. The percentage contribution of urea to WSON fraction was 0% and 20% in coarse and fine particles respectively. On an annual basis 0.81 mmol m− 2 and 1.78 mmol m− 2 of urea were deposited via wet and dry deposition, contributing to WSON by 10% and 11% respectively. Regression analysis of urea with the main ions and trace metals measured in parallel suggest that soil and anthropogenic activities significantly contribute to atmospheric urea. Comparison of dry deposition of urea using size segregated deposition velocities with urea collected on a glass bead collector suggested the existence of significant fraction of urea in the gas phase.

► Our study investigates the role of urea in the Eastern Mediterranean Nitrogen cycle.
► In aerosols urea was mainly found in the fine mode (about 20% of WSON).
► On an annual basis urea deposition contributes to WSON by about 10%.
► Origin and sources of urea are accessed via multi regression analysis.
► Our results suggested the existence of significant fraction of urea in gas phase.