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The Liulin Spring is one of the ten most famous karst springs in the Shanxi province. The abundant karst groundwater resources support the economic and social development in the Luliang Prefecture. Therefore, the study of evolution and control factors of karst groundwater is of great significance to the sustainable utilization of water resources in the watershed. For revealing the evolution and control factors of karst groundwater in the Liulin Spring area, the main ion components of 29 karst groundwater samples from spring supply area, runoff area, discharge area, and deep buried area were analyzed. The results showed that the temperature and Na + , Ca 2+ , Mg 2+ , Cl - , HCO 3 - , and SO 4 2- concentrations increased continuously along the runoff route, from the recharge area to the runoff area, to the discharge area, and then to the deep burial area. K + , Na + , and Cl - mainly come from salt rock dissolution, and Ca 2+ , Mg 2+ , HCO 3 - , and SO 4 2- mainly come from the dissolution of calcite, dolomite, and gypsum. Because they are controlled by the continuous dissolution of salt rock and gypsum, the concentration of Na + , Cl - , and SO 4 2- in groundwater has increased greatly, with the maximum value being 50 times, 80 times, and 32 times of the minimum value, respectively. Under the influence of dedolomitization, the concentration of Ca 2+ and HCO 3 - in groundwater does not change significantly, the maximum is 2-3 times of the minimum. In the recharge area and runoff area, Na + and Cl - amounts are lower, and Ca 2+ and HCO 3 - are the main cations and anions in the groundwater. However, in the discharge area and deep buried area, Cl - and Na + exceed HCO 3 - , Ca 2+ , and Mg 2+ and become the main anions and cations in the groundwater. The hydrochemical type changes from HCO 3 -Ca·Mg in the supply area to HCO 3 ·SO 4 -Ca·Mg in the runoff area, to HCO 3 ·SO 4 -Ca·Na·Mg in the recharge area, and finally to Cl·HCO 3 -Na·Ca, Cl·HCO 3 -Na, and Cl-Na·Ca in the deep burial area.

Fluorescent substances are used as good tracers in dissolved organic matter (DOM) to identify the source of DOM and its geochemical behavior in a hydrological system. However, there are few studies on the karst aquifer system. Many parameters in karst systems affect the DOM spectral information. A typical karst watershed in Northern China was selected in this research. Excitation-emission matrices (EEMs), parallel factor analysis (PARAFAC), and hydrochemical data were applied to reveal the relationship between the composition and transformation of DOM fluorescent substances in different karst water-bearing spaces. The source of DOM and the effect of water chemistry on DOM transfer were also discussed. The results showed that DOM in exogenous surface water and karst surface water in the Yufu River watershed were mainly composed of tryptophan-like substances, while the DOM in shallow karst water and deep karst water consisted of tryptophan-like and tyrosine-like substances. A comprehensive analysis by fluorescence index (FI), biological index (BIX), and humification index (HIX) displayed that the DOM in shallow and deep karst water resulted from microbial decomposition. In contrast, the DOM in karst surface water and exogenous surface water resulted from land-based input and endogenous microbial decomposition, in which endogenous contributions occupy a large proportion. Due to the chemical parameters of karst water, these three kinds of fluorescent substances extracted by PARAFAC had obviously different characteristics, i.e., ① the tyrosine-like substances had a strong adaptability to Ca 2+ and HCO 3 - , and the proportion of the tyrosine in karst water was relatively large; ② the tryptophan substance followed an opposite trend; and ③ there was a significant positive correlation between fulvic acid and TDS, turbidity, Cl - , and SO 4 2- . Observations of the watershed runoff revealed that the DOM in shallow karst water in the upper reaches came mainly from the soil and microbial degradation. The organic matter underwent a large amount of microbial decomposition and exogenous input when the water was rejuvenated with springs. After infiltration to the deep karst water in the lower reaches, the DOM gradually were converted to low aromatic hydrocarbon organic compounds and decreased macromolecules of DOM. Subsequently, the fluorescence intensity was weakened. The principal component analysis (PCA) extracted three principal components. They were the water mineralization index, soil leaching index, and hydrochemical/biochemical process index. The water mineralization index consists of hydrochemical parameters reflecting the water infiltration, transformation, and flow conditions in the karst system. The soil leaching index contains TOC, NO 3 - , and protein-like indicators relating to the relationship between protein-like substances and soil and natural leaching. The hydrochemical/biochemical process index is composed of Ca 2+ , HCO 3 - , FI, and fulvic acid indicators that illustrate the water chemistry and biochemical processes in the karst water system. In addition, the study also showed that total fluorescence intensity, fulvate-like substances, and protein-like substances can be used as a tracer for rapid seepage, transformation, and aquifer fragility for karst water, respectively. The results of the study are important in understanding the biogeochemical cycle of DOM in the karst water system and also helpful for controlling organic pollution. It also provides a new tool for characterizing the geochemical processes of organic matter in karst system.

The Wujing River, the largest river in Guizhou Province, is one of the most important water resources for social and economical development. Recently, with the fast population proliferation and rapid economic growth, the drainage basin is intensively interfered by anthropogenic activities. The hydrochemistry of surface water was analyzed from the upper-middle reaches of Wujiang River for investigating the hydrochemical characteristics and their main influencing factors. The results showed that the major cations of the four rivers were Ca²⁺ and Mg²⁺, accounting for more than 70%, and the main anions were HCO₃⁻ and SO₄²⁻, occupying more than 85%. The hydrochemical characteristics in the four rivers were found to be of HCO₃-Ca type, and mainly determined by the carbonate rock dissolution, while only a small proportion of them were of HCO₃ · SO₄-Ca type, reflecting the influence of SO₄²⁻ from anthropogenic activities. Compared to hydrochemical data in 1999, there was an obvious increase in cations and anions concentrations, majorly in NO₃⁻, SO2- ion concentrations, which were significantly affected by human activities. The Na⁺, K⁺ , Cl⁻ in the river mainly came from atmospheric precipitation, and Ca²⁺, HCO₃⁻, Mg²⁺, mainly came from carbonate rocks dissolution, while NO₃⁻ and SO₄²⁻ mainly came from human activities. According to principal component analysis and correlation analysis, hydrochemical composition of Liuchong River was affected by human activity, and that in the upstream of Sancha River was controlled by atmospheric precipitation and the dissolution of carbonate rocks, that to the downstream was enhanced by human activities. The main ion of Maotiao River was controlled by atmospheric precipitation and carbonate rocks dissolution, and also affected by human activity. The Nanming River, the Qingshui river's tributary, was mainly affected by human activity, while the middle and lower reaches of Qingshui River were affected by both the atmospheric precipitation and human activity.

Groundwater and surface water from the Upper and Middle Reaches of the Wujiang River were sampled and analyzed for the hydrochemistry and Carbon isotope in DIC. Then hydrochemical characteristics and the main influencing factors were investigated, and the contributions of carbonate dissolution by sulphuric acid to total(Ca2+ + Mg2+) and HCO3 were calculated using the stoichiometry method. The results showed that the advantage cations of groundwater and surface water is Ca2+, which accounted for more than 50% and the advantage anions is HCO3- and SO(4)2-, which accounted for more than 85%. The hydrochemical characteristics of most samples were of Ca-HCO3 type, and a small part of HCO3.SO4-Ca, reflecting a few samples affected by SO(4)2- from human source. The δ13CDIC of groundwater and surface water, varying from -12. 98%o to -6. 36%o with a changeable molar ratio between (Ca2+ + Mg2+) and HCO3- of 1. 11 to 1. 90, indicated that sulfuric acid has an important influence on hydrochemistry and δ3CDIC. The contributions of carbonate dissolution by sulphuric acid to total (Ca2+ + Mg2+) and HCO3 in groundwater ranged from 20. 59% to 92. 87% (average 51. 50%), and from 11. 47% to 86. 69% (average 36. 90%). While the contributions of carbonate dissolution by sulphuric acid to total (Ca2+ + Mg2+) and HCO3- in surface water ranged from 56. 14% to 94. 55% (with an average of 76. 89%), and 39. 02% to 89. 66% (with an average of 64.24%), respectively, demonstrated that sulphuric acid is an important agent of carbon rock weathering. The results of this study have a great significance for the protection and development and utilization of water resources in the Wujiang River basin and for karst carbon cycle research.

The riverine carbon flux is a critical component of global carbon cycle. Riverine water samples were collected from eleven hydrometric stations in the main stream of Pearl River and its tributaries during April and July, 2012. The samples were analyzed for the space and seasonal distribution characteristics of the riverine suspended substance and carbon compositions. Carbon fluxes and erosion modulus of Pearl River basin were also estimated in Boluo, Shijiao, Gaoyao, namely Dongjiang, Beijiang, Xijiang, in these two hydrological seasons. The results showed that the total suspended substance (TSS) and organic carbon, including total particulate organic carbon (POC) and dissolved organic carbon (DOC) have higher concentration in the high-water season than that in the normal-water season. Dissolved inorganic carbon (DIC) has an overwhelming concentration compared to other carbon compositions in Pearl River basin. The DIC concentration shows an order of Xijiang, Beijiang and Dongjiang from high to low. The percentage of allogenic POC in Xijiang, Beijiang and Dongjiang are 78%, 72%, 26%, respectively, and C3 plants are the main sources of allogenic POC in those three tributaries. The transported fluxes of TSS, total carbon (TC), POC, particulate inorganic carbon (PIC), DOC, DIC, total particulate carbon (TPC) and total organic carbon (TOC) are 134 x 10(12),12.69 x 10(12), 2.50 x 10(12), 1.01 x 10(12), 1.13 x 10(12), 8.05 x 10(12), 3.51 x 10(12) and 3.65 x 10(12) g x a(-1), respectively, and the erosion modulus of those compositions are 309 x 10(6), 28.98 x 10(6), 5.75 x 10(6), 2.27 x 10(6), 2.56 x 10(6), 18.4 x 10(6), 8.02 x 10(6) and 8.31 x 10(6) g x (km2 x a)(-1), respectively. Compared with average values of global large rivers, the erosion modulus of DOC, POC, and TOC in Pearl River basin are higher than the corresponding values.