The abundance of microplastic pollution along the Jajroud river of Tehran: Estimating the water quality index and the ecological risk

The reduction of renewable freshwater and the increased variety of water pollutants have made governments establish well-documented monitoring programs to maintain the quality of water resources. The Jajroud river, as a primary source of surface water, has supplied 30% of the drinking water of Tehran for more than 55 years. The present study aimed to calculate the water quality index (WQI), determine the abundance of microplastics (MPs) pollution and evaluate the induced-ecological risk. Seven samples of water and four samples of wastewater sources from the Jajroud River were collected three times. The physicochemical and microbial properties, the abundance of MPs, and the type of polymer in this river were determined using standard procedures. The WQI exceeded 76.1 in all sampling points, indicating that the water had of good quality. Ammonia was the main factor involved in the reduction of the WQI. The average abundance of MPs in water and wastewater samples was 12.14 +/- 10.07 and 30.62 +/- 9.33 particles. L-1, respectively. The fibers (70.96%) and 1-2.5 mm (30.25%) were the dominant shape and size of MPs in water, while fibers (73.05%) with sizes smaller than 0.2 mm (29%) were predominate for MPs in wastewater samples. The dominant polymers were polystyrene (PS) and polypropylene (PP), which comprised 65% and 26% of water samples and 68% and 21% of wastewater samples. An ecological risk evaluation showed that the polymer hazard index (PHI) for water and wastewater was in the range of 17.4-22.6 and 201.-24.4, respectively, indicating hazard level III for both. The values of the pollution load index (PLI) and potential ecological risk index (PERI) for water and wastewater samples were lower than 10 and 150, which indicated a hazard level at I and a minor risk, respectively. Organic nitrogen and phosphorous, temper-ature, NO3-, NO2-, and total organic carbon were determined to be the physicochemical parameters with the most significant influence on MPs abundance in the Jajroud River by regularized canonical correlation analysis (RCCA).