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The application of biochar can affect soil properties and retention of fertilizer nitrogen, but its effects and mechanism on the retention capacity of different forms of nitrogen in soils are still uncertain. In this study, an indoor soil column leaching experiment was conducted using vegetable soil samples with 3% rice husk biochar by mass prepared at 450 °C by pyrolysis and 150 mg N/kg 15N-labeled urea. Adding biochar increased the soil pH, thus alleviating soil acidification caused by fertilizer nitrogen application. It also increased the content of soil organic carbon, total nitrogen and available phosphorus while decreasing that of NH4+-N and NOX−-N(NO3−-Nand NO2−-N) in soils. NOX−-N was the predominant form in the leachate of all treatments, accounting for 63.15–87.90% of the total N loss. Compared to the urea-alone application (the N treatment), incorporating biochar and urea (the RBN treatment) significantly reduced total N and NOX−-N loss by 19.99% and 25.95%, respectively, while showing slight effects on NH4+-N loss. The 15N results show that fertilizer N retention in soil increased by 13.67%, while inorganic 15N leaching decreased by 25.97% after the biochar addition, compared to that in the N treatment. The RBN treatment increased fertilizer N losses in other ways (e.g., organic N leaching, ammonia and NOx volatilization) by 21.72%. Effects of biochar application on other N losses need to be further investigated. Biochar application can reduce the leaching of inorganic 15N and improve fertilizer N retention in the soil. Thus, the potential risk of fertilizer N on the quality of water bodies can be reduced.

The Xiong’an New Area is abundant in geothermal resources due to its unique geological structure. To address whether large-scale deep geothermal exploitation will induce a fault slip, we first determined the initial in situ stress field using shallow (~4000 m) in situ stress measurements from the North China plain. After characterizing the in situ stress field, we analyzed the initial stability of the main active faults in the sedimentary strata of the Rongcheng deep geothermal reservoir based on the Mohr–Coulomb failure criteria. Assuming that this area will be subjected to forty years of continuous fluid injection, we calculated the excess pore pressure in the deep geothermal reservoir and, subsequently, estimated the fault slip potential of the main active faults in this region from 2021 to 2060. Our results indicated that both the in situ stress field in the shallow crust of the Xiong’an New Area and the Middle-Late Pleistocene active faults will initially maintain a stable state. With constant fluid injection for forty years at six geothermal wells in the Rongcheng deep geothermal reservoir, the maximum superposed excess pore pressure at a single well is 18 MPa; this excess pore pressure value impacts the stress state of faults within 8 km of the well location. These pore pressure perturbations heavily impact the F5-10, F5-11, and F9-2 segments of the Rongcheng uplift boundary fault, with FSP values of 92%, 23%, and 47% in 2060, respectively. Porosity exacts little impact on the fault slip potential on the boundary fault segments of F5-10 and F9-2 in the Rongcheng deep geothermal reservoir, while an enhanced permeability can weaken the FSP values for these faults. The predicted maximum moment magnitude of an induced earthquake due to continuous injection of forty years can be up to Mw 5.0 with a 5% fluid loss in the Rongcheng deep geothermal reservoir. Long-term water injection may increase the ambient thermoelastic stress to the point where faults in a critical (or subcritical) stress state become unstable. The results can provide a reference for geothermal development in terms of injection rate and locations of geothermal wells.

In the published article [1], the authors realized some errors in the affiliation and email address of Yang Hong, and thus wish to make the following revisions: Add the Affiliation 5 “School of Civil Engineering and Environmental Science, University of Oklahoma, Norman, OK 73019, USA” for Yang Hong Change the email address of Yang Hong to yanghong@ou [...]

The availability of lake bathymetry maps is imperative for estimating lake water volumes and their variability, which is a sensitive indicator of climate. It is difficult, if not impossible, to obtain bathymetric measurements from all of the thousands of lakes across the globe due to costly labor and/or harsh topographic regions. In this study, we develop a new digital lake bathymetry model (DLBM) using the step-wise water recession method (WRM) to generate 3-dimensional lake bathymetric maps based on the digital elevation model (DEM) alone, with two assumptions: (1) typically, the lake’s bathymetry is formed and shaped by geological processes similar to those that shaped the surrounding landmasses, and (2) the agent rate of water (the thickness of the sedimentary deposit proportional to the lake water depth) is uniform. Lake Ontario and Lake Namco are used as examples to demonstrate the development, calibration, and refinement of the model. Compared to some other methods, the estimated 3D bathymetric maps using the proposed DLBM could overcome the discontinuity problem to adopt the complex topography of lake boundaries. This study provides a mathematically robust yet cost-effective approach for estimating lake volumes and their changes in regions lacking field measurements of bathymetry, for example, the remote Tibetan Plateau, which contains thousands of lakes.