Identification of Hydrochemical Characteristics, Spatial Evolution, and Driving Forces of River Water in Jinjiang Watershed, China

Abstract

Rivers are an important source of water in humid regions, but their availability is greatly limited by water chemistry. In order to accurately identify the changes in river water chemical composition, the compositional analysis method (CoDA) is proposed from the perspective of compositional data analysis theory, which considers the geochemical riverine system as a whole and detects the compositional changes of the entire watershed. The basic data analysis is carried out by traditional analysis methods, and the results show that the hydrochemical characteristics of different sections of the basin have significant features. The water chemistry of Dongxi River is of the HCO3− Ca type. The water of the Xixi River shows a gradual evolution from the HCO3-Ca type and high SO42− content in the upper reaches to the Cl-Ca type in the lower reaches. The hydrochemistry of river water in the watershed is mainly affected by rock weathering leaching (PC1) and agricultural and domestic pollutant discharge (PC2), with a contribution rate of 48.4% and 19.7%, respectively. Rock weathering, mining, and agricultural pollution are the main factors affecting the chemical composition of river water in different regions. The spatial composition of a single sample at different scales is monitored by the Mahalanobis distance approach in an iterative manner to minimize the influence of a single anomaly on the composition center. The results show that the main reasons for the change in river water chemical composition along the Xixi River are attributed to mine pollution, domestic pollution, and tea plantation and that along the Dongxi River is caused by domestic pollution. The hydrochemical composition changes after the confluence of the Xixi River and Dongxi River are mainly affected by human activities and seawater in urban areas. This research could provide new perspectives and methods for detecting the influences of human and natural factors on the hydrochemistry of river water in humid regions worldwide.

Spatial Distribution Patterns of Phytoplankton and Their Relationship with Environmental Factors in the Jinjiang River, China

“…Based on the national water quality data and field investigations conducted in the East and West Jinjiang between 2020 and 2023, it was observed that the pH and DO values in the East Jinjiang River were significantly higher than those in the West Jinjiang River, while the nutrient concentrations showed the opposite trend. These findings aligned with the results obtained by Zhu et al (2024) [31]. The differences in pH values between the West and East Jinjiang Rivers may be attributed to variations in water chemistry in the two watersheds, which showed that the water chemistry in the East Jinjiang River was dominated with an abundance of HCO 3 − Ca type, and the water in the West Jinjiang River was rich in SO 4…”

“…The differences in pH values between the West and East Jinjiang Rivers may be attributed to variations in water chemistry in the two watersheds, which showed that the water chemistry in the East Jinjiang River was dominated with an abundance of HCO3 − Ca type, and the water in the West Jinjiang River was rich in SO4 2− [31]. Furthermore, the relatively high nutrient concentrations in the West Jinjiang River could be linked to the extensive use of fertilizers in the tea plantations surrounding the river, as well as domestic and mine pollution [31]. TN and TP concentrations in the Jinjiang River, during early spring, often exceeded eutrophication thresholds.…”

“…2− [31]. Furthermore, the relatively high nutrient concentrations in the West Jinjiang River could be linked to the extensive use of fertilizers in the tea plantations surrounding the river, as well as domestic and mine pollution [31]. TN and TP concentrations in the Jinjiang River, during early spring, often exceeded eutrophication thresholds.…”

“…Previous studies have mainly focused on the hydrological characteristics [26], water quality, non-point source pollution simulation, heavy metal pollution, and distribution patterns of plankton in the Jinjiang River [26][27][28][29][30]. These studies have elucidated the hydrochemical characteristics, spatial evolutions, and driving forces in the Jinjiang River basin [31], and found that variations in the water chemistry in the West Jinjiang River were primarily due to pollution from mines, domestic sources, and tea plantations, and pollution along the East Jinjiang River was from domestic sources. Changes in water chemistry occurred after the confluence of the West and East Jinjiang Rivers, primarily influenced by human activities and urban sewage.…”

“…Changes in water chemistry occurred after the confluence of the West and East Jinjiang Rivers, primarily influenced by human activities and urban sewage. Additionally, variations in pH and nutrient concentrations in the Jinjiang River were observed [31], and the pollutants were mainly COD Mn , NH 3 -N, and TP [31]. Furthermore, Chen has investigated the distributions of zooplankton in the Jinjiang River during normal, flood, and drought periods [27].…”