Identification of micropollutants in Ergene river and their biotransformation potential under anaerobic conditions

Ergene River spans Thrace from northeast to southwest and joins to Maritsa River, then falls to Aegean Sea at Turkey-Greece border. The river suffers pollution from different sources such as industrial and urban discharges, runoff from agricultural and animal farms. In this study, 222 micropollutants which are listed as contaminants of emerging concern or priority substances, 18 heavy metals and 13 conventional water pollution parameters were measured in 300 samples taken from 75 points on Ergene River at four seasons in the years of 2017-2018. Moreover, major source of micropollutants as well as pollutant fingerprint of major pollution source zones in the watershed were identified. Among the most important conventional parameters, COD, varied between 17 to 1660 mg/L during the year. The highest COD values were observed next to the Evrensekiz OIZ as well as Büyükkarıştıran OIZ consist of different industries such as textiles, dyes, food and chemical industries. Arsenic, aluminum, zinc, copper, lead and chromium concentrations reached to 1.0, 83.9, 33.6, 14.6 and 7.1 mg/L next to the OIZs, respectively. 131, 135, 96 and 103 organic micropollutants were detected in at least one point during summer, fall, winter and spring sampling, respectively. Concentration of micropollutants ranged from 10 ng/L to 330 mg/L. The micropollutants embraced a wide spectrum of chemicals originated from various industrial, agricultural and domestic activities. Benzotriazoles, hexa(methoxymethyl) melamine (HMMM), tris (2-butoxyethyl) phosphate (TBEP) and benzalkonium chlorides (BACs) were the most frequently detected chemicals as well as the ones with the highest concentration. OIZs located next to the Çorlu and Ergene Creeks as well as Büyükkarıştıran OIZ were the main sources of those pollutants. For instance, HMMM was mainly originated from the textile industries located in Büyükkarıştıran OIZ. In addition, biotransformation potential of the aforementioned micropollutants which are mainly discharged from textile and metal industries into the river, at the simulated water-sediment system was tested under anaerobic and sulfate reducing conditions. Benzotriazoles and TBEP were degraded partially whereas no biodegradation was determined for HMMM and BACs. The outcomes of this study can be used to understand the fate of dominant contaminants in the river sediment and develop future pollution mitigation strategies for Ergene River.