## 3 Results and Discussion
### Distribution of N and P in Overlying Water and Sediment  
The contents of NH\({}_{3}\)-N, TN, and TP in the overlying water and sediment were accurately tested and listed in Table S3. In the overlying water from different rivers, the contents of TN, NH\({}_{3}\)-N, and TP had significant spatial differences, as shown in Figure 2. TN content in Jingshui River was the highest, which was 11.8 \(\pm\) 4.2 mg/L (mean \(\pm\) standard deviation, the same below), and that in Yongchun River was the lowest (7.4 \(\pm\) 1.3 mg/L). The order of average TN content was Jingshui River > Xinkai River > West Lake > Yitong River > Chuan Lake > Yongchun River. The spatial distribution of NH\({}_{3}\)-N was similar to that of TN. The highest NH\({}_{3}\)-N content was 8.8 \(\pm\) 5.2 mg/L in Jingshui River, and the lowest one was 0.9 \(\pm\) 0.6 mg/L in Yongchun River. The average NH\({}_{3}\)-N content was sorted as follows: Jingshui River > West Lake > Xinkai River > Chuan Lake > Yitong River > Yongchun River. The highest content of TP was 1.3 \(\pm\) 1.2 mg/L in Xinkai River, and the lowest one was 7.4 \(\times\) 10\({}^{-2}\)\(\pm\) 1.4 \(\times\) 10\({}^{-2}\) mg/L in Yongchun River. The order of average TP content was Xinkai River > Chuan Lake > Jingshui River > West Lake > Yitong River > Yongchun River. The contents of TN, NH\({}_{3}\)-N, and TP in the overlying water were all high in the north and west of Changchun, and the lowest in the south. In the sediments of different rivers, the spatial distribution of NH\({}_{3}\)-N, TN, and TP contents varied greatly (Figure 3). TN content in Xinkai River was the highest, which was 7.3 \(\pm\) 3.7 mg/L, and that in Yongchun River was the lowest (2.7 \(\pm\) 1.3 mg/L). The order of average TN content was Xinkai River > Yitong River > Yongchun River > Chuan Lake > Jingshui River > West Lake. NH\({}_{3}\)-N content in Xinkai River was the highest, which was 3.2 \(\pm\) 4.1 mg/g, and that in Jingshui River was the lowest (1.4 \(\pm\) 0.6 mg/g). Average NH\({}_{3}\)-N content was sorted as follows: The order of average content was Xinkai River > Yongchun River > Yitong River > West Lake > Chuan Lake > Jingshui River. The highest TP content was 96.3 \(\pm\) 21.1 mg/g in Yongchun River, and the lowest was 50.3 \(\pm\) 17.3 mg/g in Chuan Lake. The order of average P content was Yongchun River > Yitong River > West Lake > Xinkai River > Jingshui River > Chuan Lake. The contents of NH\({}_{3}\)-N, TN, and TP in the sediment were generally high in the southern and western rivers of Changchun City, while relatively low in the north. Figure 2: The content of ammonia nitrogen (NH\({}_{3}\)-N), total nitrogen (TN), and total phosphorus (TP) in the overlying water of six rivers in Changchun City. There are significant diversities of N and P in the overlying water and sediment of six rivers from Changchun City, but whether the N and P content can further explain the different types of rivers needs to be further explored. Hence, the other physicochemical properties of overlying water and sediment were accurately tested into Table S4. All parameters were utilized for discriminant analysis of these six rivers. The classification based on the five discriminant functions is shown in Table S5; 95.1% of the cases were correctly classified. It can be seen from Table S6 that the cumulative percentage of eigenvalues of the first two discriminant functions was 75.7%, and that of the first three discriminant functions was 89.3%. The structure matrix of discriminant function is listed in Table 1. The scatter diagram of discriminant analysis is displayed in Figure 4. It can be well observed from the scatter diagram that the first and second discriminant functions separate the centroids of the six rivers. From the structure matrix, the most influential factor on the first discriminant function was the TP content in sediment, while the most influential factors on the second discriminant function were the Eh and TP content in the overlying water.