Broad spectrum screening of 463 organic contaminants in rivers in Macedonia

• UHPLC-QTOF-MS applied for screening of organic contamination of rivers in Macedonia.
• Vardar basin rivers (Kriva, Zletovska, Bregalnica, Vardar) included in the study.
• the highest herbicide levels found in Bregalnica related to rice cultivation.
• the highest drug levels found in Vardar, downstream of Skopje, capital of Macedonia.
• large contribution to database on organic contamination of freshwaters worldwide.

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 (1839–1962 ng L−1) and Vardar River downstream from the city of Skopje (1945 ng L−1), whereas the lowest level was found in the mining impacted Zletovska River (989 ng L−1). The principal organic contaminants of the Bregalnica River were herbicides (45–55% of all detected compounds; 838–1094 ng L−1), with the highest concentrations of bentazone (407–530 ng L−1) and molinate (84–549 ng L−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 (1544 ng L−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.