Water inrush accident in the mining area is a potential hazard in the coal mining industry. Detailed detection of the inrush flow paths remains a challenge for the industry. In this study, taking the Panbei coal mine as an example, a new strategy of hydraulic tomography (HT) inversion is proposed. In order to improve the accuracy of inversion, the geological information of the site is brought into the HT inversion as a boundary condition. Then, we analyze the effect of different inversion sequences and prior information on the inversion results of HT. Finally, we use the results of HT compared with tracer test results and groundwater level contour map to determine the preferential flow paths of the study area. The results showed that: (1) The inversion sequence will not significantly impact the HT results because the distribution of K and S.S. obtained by inversion does not have a significant deviation. (2) The sequential inversion with prior information has higher accuracy than the traditional continuous inversion. HT an identify the location of fault zones. (3) Combined with the tracer test results, it can be determined that the DF1 (fault zone) has strong conductivity, while the F70 (fault zone) and WF1 (fault zone) are weakly permeable. Then, combined with the contour map of the groundwater level, it can be inferred that the preferential flow paths of groundwater in the study area. From the C3I formation outcrop, water was supplied by the Panji anticline. Groundwater mainly flows from northwest to southeast; most groundwater flow paths are along the development direction of the fault zone. The results of this paper verify that HT is a promising technology for exploring the groundwater preferential flow paths in the coal mine area.

Determining the spatial hydraulic parameters of aquifers is of paramount importance for the development and utilization of groundwater in water source areas. However, most methods are unable to accurately characterize the heterogeneity of aquifers because of the influences of complex geology, hydrogeology, structure and insufficient information. Hydraulic tomography (HT) is an effective and robust method for hydraulic parameter inversion to characterize heterogeneity. In this study, a two-dimensional HT model was established to simulate hydraulic parameter fields for a fractured karst aquifer in the Zhangji water source area (Xuzhou city, China). Steady-state hydraulic tomography (SSHT) and transient hydraulic tomography (THT) with different prior information conditions were applied to determine the high-permeability area and water-rich zones, and to infer possible locations of karst conduits and strong runoff paths in the water source area. The results indicate that: (1) THT can better reveal larger-scale heterogeneous characteristics of hydraulic properties compared to SSHT. The hydraulic conductivity distribution estimated by THT correlates well with the geological conditions of the area, especially in identifying water-rich zones formed by faults and other formations. (2) When combined with geological conditions, HT possesses the ability to identify strong runoff paths in fractured karst aquifers. (3) Accurate prior information, which is more relevant to the head response information, is conducive to obtaining more acceptable HT results. (4) THT can simultaneously identify high-permeability and high-storage zones, and the analysis of the overlap of these two regions has the potential to predict underground water reservoirs, which is of the utmost importance for the development and utilization of groundwater resources in water source areas.

Submarine groundwater discharge (SGD) serves as an important pathway for the transport of dissolved carbon from land to ocean, significantly affecting the coastal biogeochemical cycles. However, the impact of SGD-derived dissolved carbon on the coastal carbon budget remains poorly understood. This study first quantified SGD and associated dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and total alkalinity (TA) fluxes in Daya Bay using mass balance models based on radium isotopes (Ra-223, Ra-224, Ra-226 and Ra-228). We then constructed carbon mass balance models to evaluate the impact of SGD-derived carbon on the buffering capacity against coastal ocean acidification. The estimated SGD fluxes ranged from 0.80 x 10(7) to 2.64 x 10(7) m(3) d(-1). The DIC, DOC and TA fluxes from SGD were 17.90-36.44 mmol m(-2) d(-1), 0.93-2.13 mmol m(-2) d(-1), and 21.19-28.47 mmol m(-2) d(-1), respectively. Based on carbon mass balances, the DIC flux from SGD was 19-39 times the riverine input, accounting for 27.16 % similar to 37.64 % of the total carbon source. These results suggest that SGD is a major contributor to DIC, significantly affecting the coastal carbon budget. Furthermore, the average TA:DIC ratio of groundwater discharging into Daya Bay was approximately 1.13. High TA exports enhance the buffering capacity of the coastal ocean and contribute bicarbonate to the ocean, playing a significant role in the ocean carbon sequestration process. This study demonstrates the importance of SGD-derived dissolved carbon in the assessment of coastal carbon budgets.

Submarine groundwater discharge (SGD) can be as important as river discharge for marine ecosystems. Radium (Ra) isotopes are excellent tracers of SGD estimation, and the selection of groundwater radium end-members is the most critical step in using the radium mass balance model to evaluate SGD. However, where and when to collect groundwater Ra end-members and their relationship with groundwater flow were not fully considered in previous studies. Based on field investigations and numerical simulations, this study systematically analyzed the influence of groundwater flow on the spatial distribution of 224Ra activity, and a new method was proposed to determine groundwater Ra end-members by incorporating groundwater flow information in a sandy beach at Xiaojing Bay, China. The results show that the groundwater radium activity collected near the low tide mark at low tides may be the most suitable groundwater Ra end-member. Compared with the newly-proposed method, we found that the traditional methods for determining groundwater Ra end-members such as the mean value and quartile methods may overestimate the SGD rates. Our study provides new insights into the determination of groundwater Ra end-members in a tidal beach and highlights that the groundwater Ra end-members should be determined based on groundwater flow information in SGD estimations by radium mass balance model.

To disclose the distribution characteristics, the situation of flow and storage, and processes along flow paths of shallow groundwater in Tan-Lu fault zones, nine hundred and seven groundwater table elevations data and one hundred hydrochemical samples of shallow groundwater were taken from the Tan-Lu fault zone in Anhui province to analyze the characteristic of groundwater distribution. The geographic information system (GIS) method was used to analyze the spatial distribution characteristics of groundwater tables, total dissolved solids (TDS) and chloride ion (Cl − ). Geophysical prospecting, drilling material and regional hydrogeological survey were utilized to disclose groundwater storage and flow regime in the fault zone. The results show that the Tan-Lu fault zone in Anhui province has controlled groundwater flow into the Jiashan basin, Hefei basin, Chaohu area and Qianshan basin, which developed from north to south in this area. Groundwater in theses basins have recharged from surrounding areas to form a water storage space. Geophysical prospecting and drilling technology revealed that the Tan-Lu fault zone provided a flow channel and storage space for ground-water. Faults provide preferential channels in some areas for the groundwater flow and circulation, eventually deep hot-water flows upward and discharges in the form of hot-springs. The identification of the groundwater flow pathway can help to provide a reliable scientific basis for regional spatial development and utilization of groundwater resources.

Water inrush is a major hidden danger that decreases coal mining safety. Thus, preferential flowpaths of water inrush in mining areas must be investigated to prevent water disasters and guide grouting engineering. In this study, pumping and observation data of five boreholes were input into a 2D groundwater flow model established using VSAFT2 software for inversion to obtain the heterogeneous distribution information of the site. Then, the wide-field electromagnetic method was used to obtain the distribution of resistivity values at different depths in the local area. Finally, we compared and analyzed the relevant geological information of the site, such as the fault zones and karst collapse columns, obtained using the above two methods to determine the preferential flowpaths of water. The results show that (1) the hydraulic conductivity distribution estimated by hydraulic tomography is consistent with the location distribution of high-resistivity and low-resistivity areas identified by the wide-field electromagnetic method; (2) the high hydraulic conductivity zones obtained by hydraulic tomography are consistent with the known distribution of geological fault zones, which is important because water inrush accidents often occur in areas where fault zones exist; and (3) based on the comprehensive analysis of the above results, a preferential flowpaths of water inrush was identified. The flowpaths starts from the F35 fault zone, passes through KCC2, converges with the water from the middle part of fault zones F11 and F12, and finally supplies Dongfeng well D1. This paper compares HT results to resistivity estimates from independently conducted geophysical surveys. The identification of the groundwater flow pathway through HT can help to minimize future water in-rush accidents.