Broad spectrum screening of 463 organic contaminants in rivers in Macedonia.

Target screening of 463 organic contaminants in surface water using ultra high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) with direct injection was performed in spring of 2015 in northern Macedonia, at six sampling sites in four rivers belonging to Vardar basin: Kriva, Zletovska, Bregalnica and Vardar. The aim of the study was to differentiate between various types of organic contamination characteristic for different types of anthropogenic activities, such as mining, agriculture, and urbanization. Depending on the studied river, 9-16% of analyzed compounds were detected. The highest total levels of organic contaminants were recorded in agriculturally impacted Bregalnica River (1839-1962ngL-1) and Vardar River downstream from the city of Skopje (1945ngL-1), whereas the lowest level was found in the mining impacted Zletovska River (989ngL-1). The principal organic contaminants of the Bregalnica River were herbicides (45-55% of all detected compounds; 838-1094ngL-1), with the highest concentrations of bentazone (407-530ngL-1) and molinate (84-549ngL-1), common herbicides in rice cultivation. The main organic contaminants in the other rivers were drugs (70-80% of all detected compounds), with antibiotics as a predominant drug class. The highest drug concentrations were measured in the Vardar River, downstream from Skopje (1544ngL-1). Screening of surface water by UHPLC-QTOF-MS was proven as a practical tool for fast collection of comprehensive preliminary information on organic contamination of natural waters, which can present a significant contribution in the monitoring and preservation of good ecological status of freshwater ecosystems.