Hydrochemistry and Its Controlling Factors of Rivers in the Source Region of the Nujiang River on the Tibetan Plateau

Abstract

The chemical composition of river water collected from the main stream of the Naqu and its tributaries was analyzed to reveal its hydrochemical characteristics and to evaluate the water quality for irrigation purposes. Based on 39 samples, the results revealed mildly alkaline pH values and total dissolved solids (TDS) values ranging from 115 to 676 mg/L, averaging 271 mg/L. Major ion concentrations based on mean values (mg/L) were in the order of Ca 2+ > Na + > Mg 2+ > K + for cations and HCO − 3 > SO 2− 4 > Cl − > CO 2− 3 for anions. Most hydrochemical types were of the Ca-HCO 3 (~74.36%) type. Cluster analysis (CA) suggested that the hydrochemical characteristics upstream of the main stream of the Naqu were obviously different from those from the middle and downstream of the main stream and its tributaries. The analysis shows that the Sangqu, Basuoqu, Mumuqu, Zongqingqu, Mugequ basin tributary, and the Gongqu basin tributary were mainly affected by carbonate weathering. Carbonate and silicate weathering commonly controlled the hydrochemistry upstream and downstream of the main Naqu, Chengqu, and Mugequ streams. The middle of the main stream of the Naqu was mainly affected by silicate weathering, and anhydrite/gypsum dissolution mainly affected the hydrochemistry of the main Gongqu stream. The quality of water samples was suitable for irrigation purposes, except for one sample from the main stream of the Mugequ.

The Chemical Weathering of Rocks and Its Carbon Sink Effect in the Naqu River Basin of the Nujiang River Source Area, Southwest China

“…The milliequivalent proportions (meq%) of predominant ions are graphically delineated on a Piper diagram [40], which was subsequently extrapolated onto a central diamond field to discern and appraise the hydrogeochemical facies and typologies inherent in these aqueous specimens, as shown in Figure 6. Considering these results in combination with those of our previous study [22], from 2016 to 2018, the most common type of water chemistry in the Naqu River basin was that with Ca-HCO3, which accounted for about 79.24%. The hydrochemical type was that of Ca-HCO3 in the upper reaches of Naqu, Sangqu, Basuoqu, and Mumuqu over the four years of the study (2016-2019); the hydrochemical type in the middle reaches of the Naqu River was that of Mg-HCO3, which indicated that the weathering of silicate may have affected the sources of ions in this section of the river.…”

“…Most of the Naqu River basin is located in a plateau subfrigid monsoon semi-humid climate zone, with intensive solar radiation and thin air. According to the analysis of the precipitation data, it can be seen that the average precipitation in the Naqu River basin is 478 mm, indicating the total rainfall [22]. The rainy season occurs from July to August and gradually decreases from east to west [23].…”

“…Our previous research used ion ratio diagrams and the Pearson correlation coefficient to qualitatively analyze the sources of ions in the Naqu River basin from 2016 to 2018 [22]. Two different analysis methods can be mutually corroborated.…”

“…The ion analysis results of all rivers in the Naqu River basin in 2019 showed that the carbonic-acid-mediated reaction was mainly the result of the chemical weathering of rocks. The analysis of water samples from the Naqu River basin's middle and upper regions from 2016 to 2018 showed that the chemical weathering of gypsum (CaSO 4 •2H 2 O) or anhydrite (CaSO 4 ) had a certain effect on the chemical composition of the Naqu River basin [22]. It was also speculated that the chemical weathering of carbonate rocks had a great influence on the chemical composition of the water of Basuoqu, Mumuqu, Zongqingqu, and Luoqu.…”

Hydrobiological characteristics of Ganga River at Barrage Bijnor, (Uttar Pradesh), India

“…Thus, there is great diversity in India's forest, wetlands, mangrove wildlife and marine areas. The richness in fauna and flora makes it as one of the 12 mega-biodiversity countries of the world (Wang et al, 2019).…”