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There are abundant low-medium temperature geothermal resources in southern China; however, a lack of research into their properties restricts the utilization of the geothermal energy. To expand the geothermal energy potential in southern China, it is vital to clarify the nonvolcanic geothermal system mechanisms. This study aimed to elucidate the mechanisms for the Changshou geothermal field, as a representative structurally controlled convective geothermal system, by analyzing the geophysical and hydrochemical data. The surface-to-subsurface (400 m depth) electrical resistivity structure of the geothermal field was obtained by 2D inversion of two intersecting controlled-source audio-frequency magnetotellurics and electrical resistivity tomography geophysical profiles. We have identified the cap rock, reservoir, and fluid pathways of the geothermal system and verified them via drilling results. The cap was composed of Quaternary sediments and Cretaceous sandstone with moderate resistivity (10–50 Ωm), and the geothermal reservoir and fluid pathways were composed of dolomites and fracture zones with low resistivity (less than 5 Ωm), respectively. The hydrochemical results found that the geothermal water was of the type HCO3·SO4−Ca·Mg, with low values of total dissolved solids resulting from shallow groundwater mixing. Isotope analyses indicated that the geothermal water was derived from precipitation in the Dahong Mountains, southeast of the geothermal field. The average temperature of the geothermal reservoir, as estimated by chalcedony and K-Mg geothermometers, was 53°C. Based on the geothermal gradient calculation, the circulation depth of the groundwater was 1500 m, with the circulation process driven by heat flows originating deep within the earth. The Changshou geothermal field was identified as a potential source of energy for residential heating in winter, owing to the large flow (2700 m3/d) and high permeability (24.03 m/d) of the geothermal reservoir.

International audience; This study evaluates the simulation of the seasonal cycle of water isotopic composition over Tibetan Plateau regions (TP) from six isotope-enabled general circulation models (GCMs) participating in the second Phase of Stable Water Isotope Intercomparison Group. For both meteorological factors (precipitation rate and wind field) and isotopic composition, GCMs generally agree with reanalysis data and in-situ observations, but there is a significant spread across models and the isotopic seasonality is systematically underestimated. In the southern TP, the precipitation isotopic composition is more depleted in summer than in winter, and the amplitude of the simulated isotopic seasonal variations is primarily driven by the amplitude of the simulated upstream precipitation. In contrast, in the northern TP, the precipitation isotopic composition is more depleted in winter than in summer, and the amplitude of the simulated seasonal variability of isotopes is mainly driven by the simulated strength of the zonal wind. We conclude that the skill of a GCM to simulate the seasonal cycle in the isotopic composition depends mainly on the skill of the GCM to simulate the Indian summer monsoon precipitation and the westerlies. The same causes contributing to the underestimated seasonality at present-day may also contribute to the underestimated δ 18 O change at the mid-Holocene.

Stable isotopes (18O/16O and 2H/1H) are fingerprints of water molecules and thus can be used to gain insight on water circulation. Especially, the factors controlling the isotopic composition of precipitation should be identified because they act as baseline determinants of the isotopic variations of surface water and groundwater. Here, using the HYSPLIT model, we attribute observed isotope variations to different moisture sources and characterize the isotopic composition of meteoric precipitation in Northwest China. Results show that the westerlies play a dominant role across the region throughout the year, while other moisture sources only affect some parts of the region during a specific season, i.e., Arctic airflow only affects the Altay Mountains as far as the Middle Tianshan Mountains; the East Asia Monsoon only affects the region east of 100° E longitude during the summer; and summer rainfall of local origin may contribute to the precipitation budget of basin areas. Given the different moisture sources across Northwest China, a local meteoric water line (NWMWL) of δ2H = 6.8δ18O − 1.6 is observed. Our findings not only can provide valuable insights into the mechanism of precipitation isotope fractionation in Northwest China but also can contribute to a better understanding of regional climate and hydrological studies.

Biofilm-associated infections are difficult to treat in the clinics because the bacteria embedded in biofilm are ten to thousand times more resistant to traditional antibiotics than planktonic ones. Here, a smart hydrogel comprised of aminoglycoside antibiotics, pectinase, and oxidized dextran was developed to treat local biofilm-associated infections. The primary amines on aminoglycosides and pectinase were reacted with aldehyde groups on oxidized dextran via a pH-sensitive Schiff base linkage to form the hydrogel. Upon bacterial infection, the increased acidity triggers the release of both pectinase and aminoglycoside antibiotics. The released pectinase efficiently degrades extracellular polysaccharides surrounding the bacteria in biofilm, and thus greatly sensitizes the bacteria to aminoglycosides. The smart hydrogel efficiently eradicated biofilms and killed the embedded bacteria both n tvitro and in vivo. This study provides a promising strategy for the treatment of biofilm-associated infections.

The Jimo hot spring in Shandong Peninsula, China, is a typical coastal geothermal system. The geothermal water has a very high salinity (10.8 g/L) and the origin of the salt is key to utilization of this geothermal resource. A systematic investigation of the hydrochemistry and isotopes (δ11B, 87Sr/86Sr, δ18O, δD, 13CDIC and 14CDIC) of water from 14 geothermal wells was conducted. The results show that the geothermal waters from the high-temperature center and eastern part of the geothermal field are Cl-Na·Ca-type waters with Br/Cl (8 × 10−4–1.0 × 10−3), Na/Cl (0.63–0.70) and δ11B values (15.9–17.2‰) that are lower than those of seawater. The western geothermal waters are dominated by Cl-Na-type waters with Br/Cl and Na/Cl values similar to those of seawater. The depleted δD and δ18O compositions and the corrected 14CDIC age suggest that Jimo geothermal waters are mixtures of late Pleistocene to early Holocene and younger meteoric waters. An improved Br/Cl-Na/Cl diagram, ion mass balance calculations and δ11B values indicate that halite and K-salt dissolution and subsequent cation exchange formed the dominant Cl-Na·Ca-type geothermal water, and this was then modified into a small amount of Cl-Na-type water in the western area by mixing with minor seawater entrapped in the unconsolidated sediments. The 87Sr/86Sr ratios (0.710613–0.710726) of the geothermal waters reflect water–rock reactions in the sandstone. The improved Br/Cl-Na/Cl diagram, Piper plot and boron isotopic dataset containing saline waters from coastal geothermal systems worldwide further confirm that the salinity in the Jimo geothermal water originated from dissolution of marine evaporites.

Hot dry rock is an almost inexhaustible source of geothermal energy. Since the first attempt to extract thermal energy from hot dry rock in America in the 1970s, successive studies have been conducted in many countries. Recently, high-temperature rock (exceeding 180 °C) was drilled in the Gonghe basin, northeastern Tibetan Plateau, marking a significant breakthrough in the exploration of hot dry rock resources in China. A proper understanding of the origin of the hot dry rock in the Gonghe basin is essential to the evaluation of the geothermal resource potential and to the establishment of an enhanced geothermal system in the basin. In the present research, we attempt to seek clues from the radiogenic heat production of the rocks. In all, 52 core samples collected from the main boreholes in the Gonghe basin were measured for the concentrations of radioisotopes. The heat production values were determined to be 1.21–2.02 μW m−3 for the sedimentary rocks, yielding an arithmetic mean of 1.67 ± 0.29 μW m−3, and 1.17–5.81 μW m−3 for the basal granitic rocks, yielding a mean of 3.20 ± 1.07 μW m−3. The results show that the radiogenic heat production of the granitic rocks is approximately that of global Mesozoic-Cenozoic granites, which is further corroborated by an extensive compilation of heat production data for granitic rocks in the immediate vicinity of the study area (average of 2.07 ± 0.97 μW m−3, n = 136). Based on the heat production data sets combined with available geological and geophysical information, the crustal heat production contribution is determined. The results show that the heat contribution from the crust is about 48.3 mW m−2, accounting for ∼47.3% of terrestrial heat flow. Compared with the regional background heat flow, the high heat flow in the Gonghe basin may be attributed to an additional heat flow contribution (∼27 mW m−2) from a heat anomaly (probably related to partial melting) at shallow depth, which is evidenced by the low-resistivity anomalies in the magnetotelluric survey results. Thus, this study emphasizes that the anomalous heat flow and the hot dry rock geothermal resources in the Gonghe basin may be the combined effects of the radiogenic heat contribution from the thickened crust and the heat contribution from a local heat anomaly beneath the Gonghe basin.

Deep-borehole heat exchangers (DBHE) are generally coaxial pipes installed in deep boreholes and has become an alternative approach to utilize geothermal energy. Since the performance of the DBHE system can be affected by several parameters, it is important to optimize the design of parameters for the DBHE. In this paper, based on the analytical method, we carried out the sensitivity analysis of DBHE design parameters, including outer pipe diameter, inner pipe diameter, flow rate, outer pipe materials, grout materials, and borehole depth during continuous operation for 4 months. The sensitivity analysis results indicate that the heat extraction rate can be significantly affected by outer pipe diameter, borehole depth, and flow rate. The effects of grout materials, inner pipe diameter and outer pipe materials are of second-order. Finally, an optimization method based on the lowest Average Energy Cost index was proposed to optimize these DBHE design parameters under different geological conditions. Given the cost in this study, a combination scheme of all the optimal parameters is given for different depth wells under different geological conditions.

Assessment of available heat capacity in the shallow ground is important to the development of ground source or geothermal heat pumps. A new volumetric method-based approach is proposed for evaluating shallow geothermal potential by combining microtremor survey results. Parameters such as thickness of clay and sandy gravel layers can be achieved by processing the microtremor filed data. The study area was divided into grids based on the different exploration sites. The heat present in each small unit was calculated using the revised volumetric method. This division into small units improved the accuracy of assessment of the geothermal potential and helped plot the distribution map of the available heat amount, which indicated optimal locations for development and utilization of shallow geothermal resources. Jimo, China was used as an example to depict the calculation flow. Since the microtremor survey method can identify the thickness of clay, sandy gravel, and fresh bedrock layers in shallow ground, the amount of shallow geothermal resources present above fresh bedrock was calculated. In Jimo, the amount of exploitable geothermal resources, using the traditional volumetric method, was found to be 4.92 × 1012 kJ. The proposed calculation method not only provided a higher corresponding value of 6.96 × 1012 kJ but also showed the regions with the highest potential of shallow geothermal resources. Hence, this approach provides an alternative method for geothermal potential assessment which can be used globally.

Recycled moisture contributed by continental evaporation and transpiration plays an important role in regulating the hydrological processes and atmospheric humidity budget in arid inland river basins. However, knowledge of moisture recycling within many large inland basins and the factors that control moisture recycling is generally lacking. Based on a three-component isotopic mixing model, we assessed the characteristics of moisture recycling in China’s semi-arid Heihe River Basin. During the active growing season, almost half of the precipitation in the upper reaches was provided by local moisture recycling, and the main contribution came from transpiration. In the middle reaches, almost half of the precipitation in the artificial oasis and the desert-oasis ecotone was also provided by local moisture recycling, and the transpiration fraction (fTr) and evaporation fraction (fEv) of the artificial oasis differed from those of the desert-oasis ecotone. In the lower reaches, less than 25% of the precipitation was provided by local moisture recycling. Mean fTr values were relatively low in the Gobi (15.0%) in the middle reaches and in the riparian forest at Ejina (25.6%) in the lower reaches. The positive correlations between fTr and both precipitation and relative humidity suggest that higher precipitation and relative humidity promote transpiration fraction, whereas higher vapor pressure deficit reduces transpiration fraction. The positive correlation between fEv and temperature and vapor pressure deficit, and the negative correlation between fEv and relative humidity indicate that higher temperature and vapor pressure deficit promotes evaporation fraction, whereas higher relative humidity reduces the evaporation fraction. Our results show that contributions of recycled moisture (especially transpiration) to local precipitation play an important role in regional water resource redistribution in the arid and semi-arid region of northwestern China.

Large-scale ground source heat pump systems (GSHPs) are increasingly used for space heating and cooling. In comparison to small-scale GSHPs, large GSHPs are often coupled with hundreds of borehole heat exchangers (BHE), which are more susceptible to significant ground temperature changes due to the intense thermal interactions between the BHE. In this study, we developed a new model to optimize the operation of large-scale GSHPs to mitigate the underground heat/cold accumulation. The Daxing Airport GSHP system, containing 10497 BHE, making it the largest GSHP system in the world, was selected as the target for performance optimization. Four key parameters were optimized, including the cooling/heating starting sequence, operation continuity, thermal load variability, and partition mode. Our results revealed that extreme cold accumulation mainly exists between the BHE arrays, rather than inside a single array. We recommend that spacing of adjacent BHE arrays should be greater. Meanwhile, an operational sequence of cooling, with intermittent operation and constant thermal load, is also suggested. In comparison, the partition mode only lowers the thermal anomaly inside the BHE array. Our findings imply that for large-scale GSHPs, the distance between BHE arrays is the most critical factor impacting performance, which differs from small-scale GSHPs.

Observing the isotopic evolution of snow meltwater helps in understanding the process of snow melting but remains a challenge to acquire in the field. In this study, we monitored the melting of two snowpacks near Baishui Glacier No. 1, a typical temperate glacier on the southeastern Tibetan Plateau. We employed a physically based isotope model (PBIM) to calculate the isotopic composition of meltwater draining from natural snowpacks. The initial condition of the PBIM was revised to account for natural conditions, i.e., the initial δ 18 O stratigraphy of snow layers before melting. Simulations revealed that the initial heterogeneity of δ 18 O in snow layers as well as ice-liquid isotopic exchange were responsible for most variations of δ 18 O in snow meltwater, whereas new snow and wind drift could result in sudden changes of the isotopic composition of the meltwater. The fraction of ice involved in the isotopic exchange (f) was the most sensitive parameter for the model output. The initial δ 18 O in the snowpack is mirrored in meltwater in case of small f and is smoothed with a large exchange fraction f. The other unknown parameter of the PBIM is the dimensionless rate constant of isotopic exchange, which depends on water percolation and initial snow depth. The successful application of the PBIM in the field might not only be useful for understanding snow melting process but might also provide the possibility of predicting the isotopic composition of snow meltwater and improve the accuracy of hydrograph separation. Plain Language Summary Understanding the process of snow melting is vital for water resources management and protection in the mountainous regions of the Tibetan Plateau. Variations of stable isotopes of oxygen and hydrogen in snow meltwater might give important insights into the process of snow melting. Here we observed and simulated the isotopic composition of snow meltwater of two snowpacks near Baishui Glacier No. 1, which is on the southeastern Tibetan Plateau. The simulations indicate that the isotopic heterogeneity in snow layers as well as ice-liquid isotopic exchange accounts for most of the isotopic variations in meltwater. The successful simulation of isotopic evolution in meltwater provides the possibility of simulating the isotopic composition in natural snow meltwater, which is important for hydrograph separation and paleoclimate studies.

International audience; Daily precipitation samples were collected at four sites in Mount Yulong and Mount Meili regions of southeastern Tibetan Plateau and analyzed for isotopic composition. Combined with water vapor isotopic composition derived from satellites data (Infrared Atmospheric Sounding Interferometer, Tropospheric Emission Spectrometer, and Greenhouse gases Observing Satellite), the factors controlling the variability in the isotopic composition of precipitation are investigated at the synoptic, intraseasonal, and seasonal time scales. At the seasonal scale, the isotope composition in precipitation is controlled by processes along air mass trajectories affecting the water vapor at the large scale (>200 km), especially upstream deep convection and air mass origin, and by local processes transforming the large‐scale water vapor isotopic composition into the precipitation composition, especially rain evaporation and local circulation. At the intraseasonal and synoptic scales, the isotope composition in precipitation is mainly controlled by these local processes. The shorter the time scale of isotopic variations, the smaller the spatial imprint of these variations. The fact that different factors control the isotopic variability at different time scales calls for caution when applying relationships observed at these time scales to interpret isotopic variations at paleoclimatic time scales. While general circulation models successfully capture the isotopic variability and its controlling factors at the seasonal scale, it fails to simulate them at shorter time scales, because it fails to simulate the local processes.

A new significant aspect in the utilization of hydrothermal energy in China is the large-scale exploitation using multiwells from a single geothermal site. This requires detailed hydrogeochemical investigations to gain insight about deep groundwater circulation. At the Xiongxian karst geothermal site in North China, where the demonstration project of large-scale utilization was conducted, 40 boreholes with depths from 1000 to 1800 m were drilled in a region of 50 km2. A total of 25 water samples were collected, and temperature loggings were conducted in 16 of these wells. At the site scale, the hydraulic head was observed to decline from SW to NE, i.e., orthogonal to that at the regional scale. Moreover, the geothermal groundwater temperature, borehole temperature gradient, and heat flow in the caprock all exhibited the same spatial trend with the groundwater head. Based on the hydrogeochemical and temperature logging data, this was explained by mixing of lateral recharging groundwater with ascending thermal fluids through the Xiongxian Fault, after excluding the causes of pumping activities and geologic structure. In addition, geothermal groundwater 81Kr age was estimated to be approximately 760 k yr, which is much older than the 14C age of 20 to 30 k yr. The older 81Kr age implies a low renewability of deep groundwater circulation, which should be considered in terms of sustainable management in relation to the large-scale utilization of geothermal resources.

Rekeng geothermal system in Eastern Himalayan syntax is found to exhibit the strongest surface manifestations in the western Sichuan plateau, with numerous boiling springs, fumeroles and geysers. What is the heat source of such a high temperature system? Is there a magmatic heat source to support it? In this study we have attempted to seek clues from the isotope geochemistry of geothermal fluids. The stable isotope δ2H and δ18O composition of geothermal water suggests that it is recharged by precipitation and snow melt of the surrounding mountains. The chemical type of the geothermal water is alkaline HCO3-Na as a result of water-CO2-rock interaction. Geothermal reservoir temperature in the fractured metamorphic rock is estimated to be between 200 °C–225 °C, using the chemical geothermometers and the chemical thermodynamic modeling approach. During the degassing process upon rising, 0.05 mol/L CO2 has escaped from the geothermal fluid. Evidence from the relationships among major ions and geothermal suite (Li, B, F, As) indicate that the hot springs shared the same parent source fluid and they mixed with cold groundwater to different levels in the subsidiary fractures near surface. Carbon isotope signatures show that the CO2 enriched geothermal gas is 95% of crustal metamorphic origin. Additionally, based on helium isotope analysis, the mantle magmatic 3He signatures have been largely obliterated since it accounts for no more than 5%, implying there is no underlying mantle-derived magma chamber acting as heat source. Therefore, a significant portion of heat is likely converted from crustal deformation in view of the regional tectonic background as Eastern Himalayan syntax.

Geothermal resources are practical and competitive clean-energy alternatives to fossil fuels, and study on the recharge sources of geothermal water supports its sustainable exploitation. In order to provide evidence on the recharge source of water and circulation dynamics of the Tangshan Geothermal System (TGS) near Nanjing (China), a comprehensive investigation was carried out using multiple chemical and isotopic tracers (δ2H, δ18O, δ34S, 87Sr/86Sr, δ13C, 14C and 3H). The results confirm that a local (rather than regional) recharge source feeds the system from the exposed Cambrian and Ordovician carbonate rocks area on the upper part of Tangshan Mountain. The reservoir temperature up to 87 °C, obtained using empirical as well as theoretical chemical geothermometers, requires a groundwater circulation depth of around 2.5 km. The temperature of the geothermal water is lowered during upwelling as a consequence of mixing with shallow cold water up to a 63% dilution. The corrected 14C age shows that the geothermal water travels at a very slow pace (millennial scale) and has a low circulation rate, allowing sufficient time for the water to become heated in the system. This study has provided key information on the genesis of TGS and the results are instructive to the effective management of the geothermal resources. Further confirmation and even prediction associated with the sustainability of the system could be achieved through continuous monitoring and modeling of the responses of the karstic geothermal reservoir to hot-water mining.

High-temperature aquifer thermal energy storage (HT-ATES) is a cost-effective and suitable technology to store large amounts of energy. HT-ATES has been demonstrated to be an efficient and stable tool to buffer seasonal imbalances and significantly reduce greenhouse gas emissions. Fractured reservoirs are widespread in sedimentary basins worldwide. However, naturally fractured reservoirs have received little attention as potential formations for HT-ATES. The main concern regarding thermal energy storage in naturally fractured formations is the high fracture permeability, which may result in fast fluid flow and an increase in thermal losses. Therefore, quantification of the effects of fracture flow is essential to HT-ATES site verification. An HT-ATES system in a generic fractured reservoir is simulated with a 3D stochastically generated discrete fracture network (DFN) model combined with a fluid flow and heat transport model. The pressure and temperature evolutions at the well are analyzed, and the total extracted energy and thermal recovery efficiency are evaluated. The results confirm that the presence of the DFNs enhances thermal loss and thereby results in a lower thermal recovery efficiency compared with those of an unfractured reservoir. Such a decrease can reach 20%. However, simulations show that naturally fractured reservoirs might be potential candidates for HT-ATES due to a larger injectivity. A further discussion is conducted to characterize the relative importance of the hydrogeological properties of the fractures and fracture network structure on the thermal behavior of the HT-ATES system. This study provides preliminary insights into the impacts of complex natural DFN on the thermal performance of HT-ATES in fractured reservoirs.

The northeastern Tibetan Plateau (NETP) represents the growth front of the Tibetan Plateau (TP) system. This region has long been recognized as a key in understanding the topographic response and crustal thickening of the entire TP. A heat flow anomaly (Gonghe Basin, 102 mW/m2) was found in the NETP. However, the heat-generation mechanism and the heat source of the Gonghe Basin are still debated as it is unclear whether they are related to magmatic melting activities. Herein, we provide systematic hydrogeochemical data of two types of geothermal waters (type I and II: geothermal waters sampled from within the basin and the mountainous regions, respectively) found in the region. Type I high δD (−85.0‰ to −59.0‰), δ18O (−11.1‰ to −8.0‰), Cl− (mostly range from 300 to 900 mg/L), and trace element, whereas type II has low δD (−97.1‰ to −89‰), δ18O (−13.0‰ to −11.8‰), Cl− (30 to 180 mg/L) and trace elements. Furthermore, we identified the existence of a high-temperature parent geothermal fluid based on the chloride – enthalpy model, it was estimated to possess a temperature of 310 °C and a circulation depth of 6.8–7.8 km. The parent geothermal fluid originated from snowmelt water, which later mixed with a magmatic fluid. The helium (He) ratios of geothermal gas ranged from 0.01 Ra to 0.18 Ra and indicated that the source of He was primarily from a crustal source. In addition to the heat flow analysis and magnetotelluric (MT) data, we suggested that the magmatic nature of the geothermal fluid is caused by a partial melt zone, which is ubiquitous in the middle to lower crust and serves as the heat source in the NETP. Finally, a conceptual model was built to illustrate the occurrence of magmatic fluid and its genesis. The findings will help to improve the understanding of the uplift of the TP and reveals the important role of deep groundwater circulation in the formation of high-temperature geothermal resources.

Stable isotopes of precipitation samples collected during two heavy rainfall events on July 29 and September 1, 2014 at 11 stations from Beijing Network of Isotopes in Precipitation, are analyzed to discuss eventful isotopic effects. No significant correlations between precipitation δ 18O and temperature/elevation are found. After correction with the Rayleigh distillation model for the rainfall on July 29, a significant correlation between isotopes and latitude was obtained for both rainfall events. This implies both rainfalls are formed by southern moisture sources, which were also confirmed by water vapor budget and HYSPLIT model.

Karst groundwater samples were collected in the Xiongxian geothermal field for the δ18O and δ2H data analysis. Both the oxygen (-8.4‰ to -8.6‰) and hydrogen (-72.4‰ to -73.0‰) isotopes were found enriched than the precipitation (-9.4 to -11.7‰ for δ18O and -76‰ to -85‰ for δ2H, respectively) in the late Pleistocene, when the karst groundwater was recharged. The enriched oxygen isotope is attributed to water-dolomite interaction in low-middle temperature geothermal field. The water-dolomite ratio was calculated as 0.3, based on the oxygen isotope exchange. The enriched hydrogen isotope is deduced to be caused by bacterial SO42− reduction.

This paper synthesizes the research findings on the stable isotopes (δ 2 H and δ 18 O) of the water molecular, with respect to applications in tracing the natural water cycle. A general purpose diagram of δ 2 H versus δ 18 O may serve as a geo-indicator of various circulation processes the water is involved: hydrological, hydro-meteorological and hydro-geochemical. Equations and explanations are provided for a total of 13 lines in the diagram that are illustrated to show the fractionation and changes of stable isotopes when experiencing different processes: GMWL; Moisture recycling line; evaporation line, mixing lines with seawater and andesitic water, exchange lines with H 2 S, CO 2 , silicate mineral, hydrocarbon, carbonate and clay minerals. These lines serve as a basis in using water stable isotopes in the hydrological, hydrogeological and paleo-climate research.

Multistimuli-responsive hydrogels with specific functions have attracted great interest for biomedical applications; however, these smart hydrogels usually require the presynthesis of macromolecular building blocks with multiple ligands and the integration of bioactive cargoes into the gels. Here, a multistimuli-responsive hydrogel with potent antibacterial activity by a combination of supramolecular assembly and iminoboronate chemistry is reported. The hydrogel consists of all-small-molecule building blocks including aminoglycoside, guanosine, potassium ion, and a bifunctional anchor bearing both boronic acid and aldehyde groups. Guanosines form quadruplexes in the presence of potassium ions via supramolecular assembly, and the bifunctional anchor connects aminoglycosides, a class of potent antibiotics to cis-diol groups on quadruplexes via dynamic iminoboronate chemistry, yielding a smart hydrogel containing abundant antibiotics. The hydrogel is sensitive to multistimuli such as heat, acids, oxidants, glucose and crown ether, which promote the release of antibiotics from the gels. Moreover, the prepared hydrogels show potent antibacterial activities both in vitro and in vivo. The results provide a new option to prepare antibacterial hydrogels with multistimuli responsiveness via facile chemistry using all-small-molecule building blocks.

In densely inhabited urban areas, deep borehole heat exchangers (DBHE) have been proposed to be integrated with the heat pump in order to utilize geothermal energy for building heating purposes. In this work, a comprehensive numerical model was constructed with the OpenGeoSys (OGS) software applying the dual-continuum approach. The model was verified against analytical solution, as well as by comparing with the integrated heat flux distribution. A series of modeling scenarios were designed and simulated in this study to perform the DBHE system analysis and to investigate the influence of pipe materials, grout thermal conductivity, geothermal gradient, soil thermal conductivity, and groundwater flow. It was found that the soil thermal conductivity is the most important parameter for the DBHE system performance. Both thermally enhanced grout and the thermally insulated inner pipe will elevate the outflow temperature of the DBHE. With an elevated geothermal gradient of 0.04 °C m−1, the short-term sustainable specific heat extraction rate imposed on the DBHE can be increased to 150–200 W m−1. The quantification of maximum heat extraction rate was conducted based on the modeling of 30-year-long operation scenarios. With a standard geothermal gradient of 0.03 °C m−1, the extraction rate has to be kept below 125 W m−1 in the long-term operation. To reflect the electricity consumption by circulating pump, the coefficient of system performance (CSP) was proposed in this work to better quantify the system efficiency. With the typical pipe structure and flow rate specified in this study, it is found that the lower limit of the DBHE system is at a CSP value of 3.7. The extended numerical model presented in this study can be applied to the design and optimization of DBHE-coupled ground source heat pump systems.