Key Points
Regional groundwater model for North China Plain integrating most available data
Most comprehensive analyses to date of groundwater storage depletion in the NCP
Groundwater sustainability ...under complex hydrologic and socioeconomic conditions
The North China Plain (NCP) is one of the global hotspots of groundwater depletion. Currently, our understanding is limited on spatiotemporal variability in depletion and approaches toward more sustainable groundwater development in this region. This study was intended to simulate spatiotemporal variability in groundwater depletion across the entire NCP and explore approaches to reduce future depletion. Simulated predevelopment groundwater recharge (∼13 km3/yr) primarily discharged as base flow to rivers and evapotranspiration. Initial groundwater storage was estimated to be 1500 km3 of drainable storage in shallow aquifers and 40 km3 of compressive storage in deep aquifers. Simulated groundwater depletion from 1960s to 2008 averaged ∼4 km3/yr. Cumulative depletion was 50 km3 (∼20% of pumpage) in the piedmont district, 103 km3 (∼20%) in the central plain, and 5 km3 (12%) in the coastal plain. However, depletion varied with time: ∼2.5 km3/yr in the 1970s, ∼4.0 in the 1980s, ∼2.0 in 1990–1996; ∼7.0 in 1997–2001, and ∼4.0 in 2002–2008. Recharge also varied spatially, averaging ∼120 mm/yr and concentrated in the piedmont district (200–350 mm/yr) while lower in the central and coastal plains (50–100 mm/yr). Simulation of several alternatives, including managed aquifer recharge, increased water use efficiency, brackish water use, and interbasin water transfer, indicated that the combination of these strategies could be used to recover groundwater storage by 50 km3 over a 15‐year period. This study provides valuable insights for developing more sustainable groundwater management options for the NCP; the methods are useful for managing other depleted aquifers.
•Impacts of anthropogenic landscape change on groundwater recharge (GR) reviewed.•Agricultural and urban land conversion affect GR rates, locations and mechanisms.•Combination of tracer, physical and ...modelling techniques can be employed.•Quantifying effects of urbanisation on GR presents a major research challenge.
The impacts of anthropogenic modifications to the landscape on groundwater recharge rates, locations, and mechanisms are reviewed. The two major categories of change examined are conversion of land for agriculture and urbanization, both of which have significant effects on groundwater recharge. Techniques for identifying and quantifying the changes in recharge due to these impacts are discussed. Land-clearing for agriculture and surface water transfer for irrigation have resulted in order of magnitude increases in recharge rates in many semi-arid regions worldwide, causing ongoing land and water salinization and water-logging problems. While increased recharge by irrigation return flow may alleviate shallow groundwater depletion in some settings, this is complicated by the effect of unsaturated zone thickening, which reduces the fraction of potential recharge becoming actual recharge, and may result in new water quality risks such as nitrate contamination. Expansion of urban and peri-urban land and their associated surface and sub-surface infrastructure results in complex water balance changes that re-distribute groundwater recharge locations, modify recharge mechanism(s) and result in variable impacts on recharge rates (e.g., overall net decrease, increase or minimal change) and quality. While changes to groundwater recharge resulting from conversion of land for agriculture are relatively well understood, less is documented about the changes resulting from urbanization, due to a paucity of data from field-based studies. Two case studies from Beijing, China and Melbourne Australia are examined, which highlight these impacts and demonstrate some potential methodological techniques for this topic.
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•Six data-driven models were compared for predicting groundwater temporal dynamics.•Deep learning models outperformed tree-based machine learning models.•LSTM with encoder-decoder ...structure is superior among the deep learning models.•Human activities had a much stronger impact on NCP groundwater dynamics than climate change.
Data-driven models (DDMs) have gained increasing popularity in groundwater hydrology in recent years due to the advancement of machine learning algorithms and the flexibility of easily accessible data. For groundwater purposes, the differences in deep learning (DL) algorithms compared with traditional tree-based machine learning (TB) algorithms have not been fully investigated, and the importance of different input features for groundwater level simulation has rarely been addressed. In this study, we test and validate six DDMs for simulating the groundwater levels of the North China Plain (NCP) at selected boreholes. The NCP is a large alluvial aquifer system (144,000 km2) overexploited by massive water withdrawals since the 1960s. In our simulations, four DDMs were tree-based (random forest, XGBoost, gradient boosting regression, LightGBM), and two were deep learning algorithms (Vanilla-LSTM and encoder-decoder-LSTM). The results showed that deep-learning-based DDMs provided a better correlation to observed data than tree-based models. Additionally, encoder-decoder-LSTM had the best model performance among all DDMs, and it had the ability to generate compelling results (R2 = 0.61, RMSE = 0.73 m), although each individual driving factor had a low correlation to the simulation target. GINI coefficient analysis and permutation feature importance analysis were used to determine the ranking of different model driving factors for the interpretable results. The results showed that the factors related to human activities had a much stronger impact on groundwater level variation than other factors. A preprocessing procedure of the driving factors helps produce satisfactory simulations aimed at sustainable water management and aquifer restoration, especially in data-scarce areas.
Emission factors of particulate matter （PM）, element carbon （EC）, organic carbon （OC）, SO2, NOx, CO, CO2, and ten ions （Na^＋, NH4^＋, K^＋, Mg^2＋, Ca^2＋, Fˉ, Clˉ, NO2ˉ, NO3ˉ, SO42ˉ） were estimated from ...the domestic burning of four types of commonly produced crop residues in rural China： rice straw, wheat straw, corn stover, and cotton stalk, which were collected from the representative regions across China. A combustion tower was designed to simulate the cooking conditions under which the peasants burned their crop residues in rural China, to measure the emission factors. Results showed that wheat straw had the highest emission factor for the total PM （8.75 g/kg） among the four crop residues, whereas, corn stover and wheat straw have the highest emission factor for EC （0.95 g/kg） and OC （3.46 g/kg）, respectively. Corn stover also presents as having the highest emission factors of NO, NOx, and CO2, whereas, wheat straw, rice straw, and cotton stalk had the highest emission factors of NO2, SO2, and CO, respectively. The water-soluble ions, K^＋ and Clˉ, had the highest emission factors from all the crops. Wheat straw had a relatively higher emission factor of cation species and Fˉ, Clˉ, NO2ˉ than other residues.
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•Wood lignin derived carbon quantum dots for in-situ photothermal thermogenesis.•Green fabrication strategy of wood resources with ecological and economic merits.•Evaporation ...performance of 1.18 kg·m−2 with efficiency up to 79.5% was achieved.•Fast induced thermogenesis performance and water adsorption via capillary force.•Water transportation and evaporation mechanisms were comprehensively revealed.
Photothermal evaporation and desalination via renewable solar energy has promising potential to alleviate freshwater scarcity. However, recent reported systems usually lack sufficient environmental compatibility, ecological security, and energy-saving concern. Here, a novel and green photothermal evaporation system with ecological and economic advantages was designed. An evaporation performance of 1.18 kg·m−2 (1.09 kg·m−2·h−1) with up to 79.5% efficiency at one sun illumination (1 kW·m−2) was achieved. More importantly, a series of simulation and numerical modelling was synchronously developed to analyze in-depth the main factors that affect water transportation and evaporation processes. The channel size, temperature distribution, and formed gradient were carefully investigated and discussed. Notably, this system exhibited satisfactory repeatability and stability. In addition, only a few photothermal components are required in this system, which will also bring a significant economic merit. Taken together, this work successfully provides new insights into developing a sustainable photothermal evaporation system with ecologically friendly property and satisfactory performance in practical application. Moreover, it also reveals the corresponding water transportation and photothermal evaporation mechanisms, and maximizes the evaporation efficiency.
•We estimate the GWS depletion and remaining exploitable GWS in Cangzhou in 1960–2010.•The total exploitable deep GWS in Cangzhou decreased by 49.8%∼52.2% during 1960–2010.•Groundwater ...overexploitation leads to permanent loss of groundwater storage capacity.•InSAR is an effective tool for assessing sustainability of a confined aquifer system.
Deep groundwater (confined groundwater) is the major water source in Cangzhou, situated in the North China Plain. Long-term deep groundwater overexploitation has resulted in substantial groundwater storage (GWS) depletion. Quantifying the influence of long-term overexploitation on deep groundwater resources is extremely important to maintain the sustainability of the confined aquifer system. In this study, we estimate the amount of total exploitable GWS and total GWS depletion during 1960–2010 in the confined aquifer system across Cangzhou by combining use of the InSAR deformation, estimated skeletal storativity, hydraulic head observations, and hydrogeological data. The total exploitable GWS in Cangzhou was 26.1 ± 21.3 km3 and decreased by 13.0 ± 8.1 km3 ∼ 13.6 ± 8.5 km3 until 2010, accounting for 49.8%∼52.2% of the total amount. It is worth noting that 87.4%∼87.9% of the total GWS depletion is irreversible, leading to a substantial permanent loss of groundwater storage capacity. Our results suggest that the long-term overexploitation has threatened the water supply security in Cangzhou. It is demonstrated that InSAR can be an effective tool for assessing the “physical state” and “sustainable development potential” of a confined aquifer system.
We present detailed high-resolution emission inventories of black carbon (BC) and organic carbon (OC) from China in the year 2000. The latest fuel consumption data, including fossil and biomass fuels ...and socio-economic statistics were obtained from government agencies, mostly at the county level. Some new emission factors (EFs) from local measurements also were used. National and regional summaries of emissions are presented, and gridded emissions at 0.2°×0.2° resolution are shown. Our calculated emissions were 1500 Gg for BC and 4100 Gg for OC, mainly due to the burning of coal and biofuels. The carbonaceous aerosol emissions estimated here are higher than those in previous studies, mainly because coal burning by rural industries and residences were previously underestimated. More carbonaceous aerosols are emitted from eastern China than western China. A strong seasonal dependence is observed for emissions, with peaks in May and October and low emissions in April and July; this seasonality is mainly due to patterns in residential heating and agriculture waste open burning.
Using natural tracer profiles to study migration of porewater salinity can help determine fluid fluxes and the timescales of salinization and freshening in coastal regions. Saline groundwater ...associated with evaporation and transgression events is widely distributed in the North China Plain (NCP). However, the fluid flux, time scales, and importance of different salinization processes are poorly constrained, particularly in areas beyond the limit of marine influence. Chloride (Cl) and δ18O profiles were obtained from two boreholes: one drilled at the edge of the piedmont alluvial fan (HS borehole) and one in the coastal region (G1 borehole). Numerical simulation of Cl and δ18O profiles confirmed diffusion‐dominated solute transport but also indicated slow upward advective flow over geological timescales. The profile modeling at HS indicated that salinization related to evaporation has occurred since the Late Pleistocene. Assessment of alternative conceptual models indicates that intensive groundwater pumping in recent decades has also caused significant downward movement of saline porewater (e.g., movement of brackish water at ~0.6 m/yr), mixing modern or Holocene water with Pleistocene water. The coastal Cl profile modeling in contrast shows that porewater salinity can be primarily attributed to salt diffusion during four transgression/regression cycles since the late Middle Pleistocene. The Cl transport appears never to have reached an equilibrium state during the glacial‐interglacial cycles. This suggests not only that trapped Holocene seawater is still present and leaching into adjacent sediments but also that Pleistocene water has never been entirely flushed from the deep part of the coastal sediments.
Key Points
Mechanisms and timescales of salinization/freshening processes were studied in coastal region where marine and nonmarine sources coexist
Diffusion dominated migration of porewater salinity affected by upward advection and downward flow caused by intensive pumping
Pleistocene water has never been entirely flushed from coastal sediments during glacial‐interglacial cycles
BackgroundPancreatic cancer (PC) is a common malignancy of the digestive system and is characterized by poor prognosis and early metastasis. Tumor immune escape plays an important role in PC ...progression. Programmed death 1 (PD1) blockade therapy is a promising treatment for patients with PC, but is yet to achieve significant clinical effects so far. Interferon gamma (IFN-γ) is a soluble dimeric cytokine that is closely associated with tumor immune surveillance and cytotoxicity. IFN-γ suppresses a variety of tumor-derived cytokines in PC, such as CXCL8. In the present study, we investigated the therapeutic efficacy of combined anti-PD1 and IFN-γ treatment in PC.MethodsBxPC-3 and Panc-1 human PC cell lines were used to construct a murine PC model. Blood samples (n=44) and surgical resection specimens (n=36) from human patients with PC were also collected. χ2 test, two-tailed unpaired t-test or Kaplan-Meier survival analysis was used to calculate p values.ResultsPD1/PD-L1 signaling was overexpressed in PC tumor-bearing mice. Anti-PD1 prevented tumor growth if initiated early after tumor inoculation; however, delayed anti-PD1 treatment showed limited benefit. Murine PC model had a preferential expansion of CXCR2+CD68+ macrophages, and these cells showed an immunosuppressive nature (M2 polarization). PC tumors overexpressed CXCL8 and tumor-derived CXCL8 deficiency prohibited the trafficking of CXCR2+CD68+ macrophages. IFN-γ suppressed the expression of tumor-derived CXCL8, and combined with IFN-γ treatment, delayed anti-PD1 treatment showed significant antitumor effects. Thus, we conclude that murine CXCR2+CD68+ macrophages traffic to PC tumors by tumor-derived CXCL8 and mediate local immunosuppression, which limits the efficacy of PD1 blockade therapy. IFN-γ suppresses tumor-derived CXCL8 and inhibits the tumor trafficking of CXCR2+CD68+ macrophages by blocking the CXCL8–CXCR2 axis to enhance anti-PD1 efficacy. Human PC also produces high levels of CXCL8. Patients with PC present elevated CXCR2 expression on peripheral and tumor-infiltrating CD68+ macrophages, which are associated with advanced tumor stage and poor prognosis.ConclusionOur findings suggest that IFN-γ is a translatable, therapeutic option to improve the efficacy of PD1 blockade therapy by preventing trafficking of CXCR2+CD68+ macrophages via blocking the CXCL8–CXCR2 axis.
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