With the intensification of human activities, the water resource environment in the karst mountainous area of central Shandong has undergone significant changes, directly manifested in the cessation of karst spring flows and the occurrence of karst collapses within the spring basin in the Laiwu Basin. To support the scientific development and management of karst water, this study utilizes comprehensive analysis and deuterium-oxygen isotope test data from surveys and sampling of 20 typical karst springs conducted between 2016 and 2018. By integrating mathematical statistics, correlation analysis, and ion component ratio methods, the study analyzes the genesis, hydrochemical ion component sources, and controlling factors of typical karst springs in the Laiwu Basin. The results indicate that the genesis of karst springs in the Laiwu Basin is controlled by three factors: faults, rock masses, and lithology, and can be classified into four types: water resistance controlled by lithology, by faults ,by basement and by rock mass. The karst springs are generally weakly alkaline freshwater, with the main ion components being HCO3- and Ca2+, accounting for approximately 55.02% and 71.52% of the anion and cation components, respectively; about 50% of the sampling points have a hydrochemical type of HCO3·SO4-Ca·Mg. Stable isotope (δ18O and δD) results show that atmospheric precipitation is the primary recharge source for karst springs in the Laiwu Basin, and there is varying degrees of evaporative fractionation and water-rock interaction during the groundwater flow process, resulting in significantly higher deuterium excess (d-excess) in sampling points on the southern side of the basin compared to the northern side, indicating clear differentiation. The water-rock interaction during the karst groundwater flow process and human activities are the main controlling factors for the formation of hydrochemical components: the dissolution of carbonate rocks, mainly calcite, is the primary source of HCO3-, SO42-, Ca2+, and Mg2+; the dissolution of salt rocks and reverse cation exchange adsorption contribute to the weak surplus of Ca2+ and Mg2+ and the deficit of Na+ and K+ ions in karst springs; calculated saturation index (SI) values indicate that gypsum, aragonite, calcite, and dolomite in the springs are saturated, while the SI value of salt rock is unsaturated. The mixing of urban domestic sewage, agricultural planting activities, and the use of manure also contribute to the formation of Cl- and NO3- ions in karst springs.

With the intensification of human activities, the water resource environment in the karst mountainous area of central Shandong has undergone significant changes, directly manifested in the cessation of karst spring flows and the occurrence of karst collapses within the spring basin in the Laiwu Basin. To support the scientific development and management of karst water, this study utilizes comprehensive analysis and deuterium-oxygen isotope test data from surveys and sampling of 20 typical karst springs conducted between 2016 and 2018. By integrating mathematical statistics, correlation analysis, and ion component ratio methods, the study analyzes the genesis, hydrochemical ion component sources, and controlling factors of typical karst springs in the Laiwu Basin. The results indicate that the genesis of karst springs in the Laiwu Basin is controlled by three factors: faults, rock masses, and lithology, and can be classified into four types: water resistance controlled by lithology, by faults, by basement, and by rock mass. The karst springs are generally weakly alkaline freshwater, with the main ion components being HCO₃⁻ and Ca²⁺, accounting for approximately 55.02% and 71.52% of the anion and cation components, respectively; about 50% of the sampling points have a hydrochemical type of HCO₃·SO₄-Ca·Mg. Stable isotope (δ¹⁸O and δD) results show that atmospheric precipitation is the primary recharge source for karst springs in the Laiwu Basin. There are varying degrees of evaporative fractionation and water–rock interaction during the groundwater flow process, resulting in significantly higher deuterium excess (d-excess) in the sampling points on the southern side of the basin compared to the northern side, indicating clear differentiation. The hydrochemical composition of the karst groundwater system is predominantly governed by water–rock interactions during flow processes and anthropogenic influences. Carbonate dissolution (primarily calcite) serves as the principal source of HCO₃⁻, SO₄²⁻, Ca²⁺, and Mg²⁺, while evaporite dissolution and reverse cation exchange contribute to the slight enrichment of Ca²⁺ and Mg²⁺ alongside depletion of Na⁺ and K⁺ in spring waters. Saturation indices (SI) reveal that spring waters are saturated with respect to gypsum, aragonite, calcite, and dolomite, but undersaturated for halite. The mixing of urban domestic sewage, agricultural planting activities, and the use of manure also contributes to the formation of Cl⁻ and NO₃⁻ ions in karst springs.