*Article* **Physico-Chemical Characterization of an Urban Rainwater (Zagreb, Croatia)**

**Palma Orlovi´c-Leko <sup>1</sup> , Kristijan Vidovi´c 2,\* , Irena Cigleneˇcki <sup>1</sup> , Dario Omanovi´c <sup>1</sup> , Mathieu Dutour Sikiri´c <sup>1</sup> and Ivan Šimuni´c <sup>3</sup>**


Received: 20 December 2019; Accepted: 22 January 2020; Published: 28 January 2020

**Abstract:** The characterization of organic matter (OM) and trace elements (TEs) was conducted in bulk precipitation samples collected in an urban area of Croatia (Zagreb center), from January 2009 to October 2011 (N = 31). Characterization of OM was performed by measurement of dissolved (DOC) and particulate forms of organic carbon (POC), as well as surface-active substances, copper complexing capacity and reduced sulfur species which were determined electrochemically. Concentrations of TEs (Al, Fe, Zn, Cr, Ba, Mn, Cu, Sr, Ti, Pb, V, Ni, Rb, Sb, As, Sn, Se, Co, Cd, Mo) were analyzed by HR ICP-MS. The most important outcome of this study is confirmed relatively low concentrations of DOC (0.69–4.86 mgC L−<sup>1</sup> ) and TEs. Daily fluxes of Zn, Pb, Ni, As, and Cd were two to three times lower than that of those reported for an urban industrial site in Europe. Additionally, this study shows that the value and reactivity of rainwater DOC has not considerably changed if compared with the results from the 1998–1999 study (0.78–4.39 mgC L−<sup>1</sup> ). High traffic density and thermal power plants are assumed to be the main local sources of pollutants in Zagreb. Using Al as a reference element, it was found that Cd, Sb, and Cu were associated with anthropogenic sources. The solubility of Sr, Zn, Cd, Ni, Cr, As, and Rb was higher than 70%. Another critical characteristic of precipitation composition is episodic variation in POC concentration because of Saharan dust transport. Obtained data can be valuable for environmental quality assessment, as well as for insight into atmospheric deposition processes.

**Keywords:** organic carbon; surface-active substances; trace elements; reduced sulfur species; long-range transport
