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In the arid to semi-arid district of Chengcheng, Weinan City, in central Shaanxi Province, diminishing groundwater reserves in the shallow Quaternary (QLB) aquifer and elevated fluoride in the similarly shallow Permo-Triassic (PTF) aquifer, have promoted interest in the development of groundwater resources in the deep but poorly understood Cambrian-Ordovician carbonate aquifer system (COC). To investigate the origin of the COC groundwaters and the relationship between the deep and shallower systems, a hydrochemical study was undertaken involving 179 major and minor ion analyses, 39 stable isotope analyses (δD and δ18 O), and 14 carbon isotope analyses (14 C and δ13 C). PHREEQC 3.0 was used to investigate mixing. Hydrochemical data support the presence of a well-connected regional flow system extending southwards from the more mountainous north. Stable isotope data indicate that the COC groundwaters originate as soil zone infiltration, under a much cooler regime than is found locally today. This is confirmed by 14 C, which indicates the groundwater to be palaeowater recharged during the late Pleistocene (∼10-12 ka B.P.). The presence of nitrate in the COC groundwaters suggests leakage from overlying shallow aquifers currently provides an additional source of COC recharge, with major faults possibly providing the primary pathways for downward vertical flow.

Throughout China, both coal and water are very important resources; however, serious conflict can arise between mining of deep coal reserves and essential aquifer resources. The problem is particularly severe in eastern China where a deep, thick, and productive Ordovician limestone aquifer immediately underlies Permo-Carboniferous coal-bearing sediments and poses a serious threat to the safety of coal exploitation. The problems are caused by high water pressures in the Ordovician aquifer and the risk of catastrophic flooding at the coalface caused by strong upward flow across a relatively thin aquitard. The problem can be alleviated by mine dewatering, but this generates large volumes of contaminated wastewater that require safe disposal. In a feasibility study carried out at Yanzhou coalfield, eastern China, hydrogeological studies have been undertaken to explore options for utilizing water pumped during mining operations, thus making more efficient use of the Ordovician groundwater reserves. The groundwaters are recharged at outcrops but readily become SO4·Cl–Ca·Mg in character with TDS increasing considerably with depth. Focusing on the Xinglongzhuang coal mine, test pumping and development of a transient groundwater flow model of the system have allowed alternative strategies for pressure management to be investigated. The study shows that coal-mining operations can proceed safely with as few as six underground dewatering boreholes removing 1800 m3/h. Moreover, the extracted water could be utilized after treatment to reduce sulfate concentrations. The coordinated exploitation approach demonstrated in this study provides a good example of wise environmental stewardship that other extractive industries would do well to consider.

The Great Lakes Basin (GLB) holds vast reserves of groundwater, the great majority of which eventually drains to the lakes. Urban growth significantly affects both the quality and quantity of this groundwater and thereby represents a potential threat to the long-term viability of the Great Lakes hydrologic system. Urban areas import, manufacture, store, transport, and utilise large volumes of chemicals, a proportion of which inevitably finds its way to the shallow sub-surface. In many cases, potentially polluting chemicals are applied directly to urban surfaces (e.g. as road salts, fertilizers and pesticides), are stored in the subsurface (e.g. gasoline tanks) or are released to the subsurface (e.g. septic systems). Because most of the basin's larger urban areas rely almost exclusively on lake-based supplies, very little attention is given to the accumulation of contaminants in shallow urban groundwaters and the serious risks they pose. Assessment of the problem is complicated by the widespread use of urban fill and a complex network of drains, pipes and tunnels that create “urban karst”, a shallow artificial aquifer, unique to urban settings, that exerts a major, yet often unpredictable influence on groundwater flow and contaminant transport. Management of ground water pollution, and its impact on the receiving Great Lakes, will require rigorous audits of all urban sources of contamination together with the development and calibration of groundwater flow and transport models that will enable the fate of urban pollutants to be reliably predicted even when groundwater is not used for supply.

Because of land subsidence in Nantong City caused by aquifer pumping, studies have been undertaken using a 3D groundwater flow model linked to a 1D land subsidence model to optimize the rates and distribution of abstraction. Model results to the end of 2022 show that the current pumping regime will cause subsidence rates to exceed established control targets by over 40% locally. However, a radical redistribution of pumping wells including the greater use of shallower aquifers will potentially allow annual yields to be increased threefold to around 128 × 106 m3 without exceeding those targets. The results of this work have important implications for the sustainable development of groundwater resources in Nantong City and demonstrate the considerable benefits of modelling for proactive aquifer management and protection against subsidence.

Groundwater is one of the main sources of drinking and agricultural water in arid and semi-arid regions but is becoming increasingly threatened by contamination. Vulnerability mapping has been used for many years as an effective tool for assessing the potential for aquifer pollution and the most common method of intrinsic vulnerability assessment is DRASTIC ( D epth to water table, net R echarge, A quifer media, S oil media, T opography, I mpact of vadose zone and hydraulic C onductivity). An underlying problem with the DRASTIC approach relates to the subjectivity involved in selecting relative weightings for each of the DRASTIC factors and assigning rating values to ranges or media types within each factor. In this study, a clustering technique is introduced that removes some of the subjectivity associated with the indexing method. It creates a vulnerability map that does not rely on fixed weights and ratings and, thereby provides a more objective representation of the system’s physical characteristics. This methodology was applied to an aquifer in Iran and compared with the standard DRASTIC approach using the water quality parameters nitrate, chloride and total dissolved solids (TDS) as surrogate indicators of aquifer vulnerability. The proposed method required only four of DRASTIC’s seven factors – depth to groundwater, hydraulic conductivity, recharge value and the nature of the vadose zone, to produce a superior result. For nitrate, chloride, and TDS, respectively, the clustering approach delivered Pearson correlation coefficients that were 15, 22 and 5 percentage points higher than those obtained for the DRASTIC method.

Ground fissures in China have garnered increasing international attention in recent years due to their areal extensiveness, large scale, and high hazard potential. These fissures, especially those in the Fen-Wei Basin and North China Plain, severely restrict planning and construction in big cities, threaten the operation of underground and above ground railways, and cause serious economic loss. Recent research shows that ground fissures in China occur mainly in sedimentary basins and develop along active faults and at the edges of groundwater cones of depression. Most of these fissures are caused by the combined action of tectonic stress and hydrodynamic force. Effective ground fissure disaster reduction technologies are developed and they include pumping control, reasonable avoidance, adaption to deformation, and local strengthening. This paper provides an overview on ground fissure studies in China and demonstrates how research results can serve economic development and geohazard mitigation.

The standard degree-day, temperature-index approach to calculating snowmelt generation and refreezing (the SDD method) is convenient and popularly used but seriously miscalculates the volumes of water that change phase on days when temperatures fluctuate either side of the freezing point. Additionally, the SDD method does not provide any estimate of the duration of daily melting and refreezing events. A modified version of the standard formula is introduced (the MDD method) that overcomes such problems by removing dependence on a single temperature index (the average daily temperature estimated over a 24-h period beginning at midnight) and instead transfers reliance onto daily air temperature extremes (maximum and minimum temperatures) at known times of occurrence. In this way, the modified formula retains the simplicity of the standard approach while targeting those segments of the diurnal air temperature curve that directly relate to periods of melting and freezing. Newly introduced temperature and time degree-day parameters allow the duration of melting and refreezing events to be estimated. The MDD method was evaluated for two sites in the snow-belt region of Canada where the availability of hourly records of daily temperature allowed the required MDD input parameters to be calculated reliably and thus used for comparative purposes. During testing, the MDD input parameters were obtained from daily temperature extremes and their times of occurrence, using two alternative approaches to synthetic air temperature curve generation, one linear, the other trigonometric. Very good agreement was obtained in both cases and confirms the value of the MDD approach. However, there is no significant benefit to be gained by using air temperature approximating functions more complicated than the linear method for supplementing the missing continuous air temperature measurements. Finally, the MDD approach is not seen as a replacement for the regular SDD method, so much as tool that can be applied when the SDD methodology is likely to become unreliable. This is best achieved by using a hybrid SDD-MDD algorithm that invokes the MDD approach only when the necessary conditions arise.

This essay investigates relationships among friendship, self-fashioning and temporality in Philips’s elegies, which question traditional expressions of transcendent solace by placing resistant, intertextual consolations within secular frameworks. The majority of Philips's elegies dwell within the contingencies of mediating absences, as all of the parting poems reveal, illuminating the bonds of friendship that yield their worldly singularities through occasions of loss. Philips devises friendship and self-fashioning as tropes for her poems' concerns with heightened psychological (and increasingly intertextual) events that merge private and public spheres of discourse. Through her dialogic subjectivities, Philips crafts a kairic literary history for her counter-public as a challenge to teleological historiography. Such contiguities among co-poets and poems illustrate Philips's unique historical imagination, her keen attunement to regenerative secular temporality, and her contribution to the emergenc...

The district of Chengcheng lies within Weinan city in central Shaanxi Province. It suffers from serious water shortages, a dilemma that is amplified by elevated concentrations of fluoride in the groundwater, a primary source of domestic water supply. To determine the extent and origin of the fluoride problem, a study was undertaken involving 144 groundwater samples collected from two aquifers in the region: the shallow Quaternary overburden aquifer (QLB) (10 samples) and the more widely utilized Permo–Triassic-fractured rock aquifer (PTF) (134 samples). Spatial analysis of the hydrochemical data shows that concentrations of fluoride in the PTF increase from north to south, generally following the direction of groundwater flow. 50 % of the samples show fluoride in excess of the 1.0 mg/L drinking water quality standard. Statistical analysis of data from the Permo–Triassic-fractured rock aquifer shows the fluoride to correlate positively with Ca2+, Na+, and HCO3 − and suggests mineral dissolution involving fluorite (CaF2) to be the primary source of the elevated fluoride. Analysis using PHREEQC reveals the groundwaters to be oversaturated with respect to calcite but undersaturated with respect to fluorite, and support such a hypothesis. Significantly, a positive relationship between NO3 − and F− for the PTF groundwaters suggests that trace amounts of fluoride in applied fertilizers may provide an additional source of fluoride. 28 water samples were also investigated using stable isotopes (δD and δ18O) and reveal that aquifer recharge is primarily due to irrigation water derived from the Shibaochuan Reservoir at high elevation to the north west of the study area, the irrigation water undergoing significant evaporation prior to entering the aquifer. The concentrating effect of evaporation also contributes to the elevated fluoride problem.

The transport behaviour of nitrite in a shallow sedimentary aquifer in northwest China was investigated in the laboratory by conducting a soil column experiment under flow velocity and temperature conditions likely to be encountered in field situations. The transport characteristics of nitrite are not well known scientifically and the purpose of the study was to provide data that are considered essential for the development of programs for aquifer remediation and groundwater quality protection. The soil column experiment was performed at a constant flow rate for a period of 12 days using a 40 cm column. It involved a 1.5 mmol/L solution of sodium nitrite to which sodium bromide had been added as a chemically conservative tracer. The data were analysed using the CXTFIT 2.0 model code for the one-dimensional convective–dispersive transport of solutes. The breakthrough curve (BTC) for bromide revealed an average linear flow velocity of 0.3445 cm/h for the experiment and a longitudinal dispersivity of 4.16 cm for the sediment. The effective porosity was determined to be 29 %. The BTC for nitrite showed a significant delay compared to the bromide BTC, presumably due to some form of chemical reaction. Significantly, outflow concentrations of nitrite approached 1.5 mmol/L (the input value) towards the end of the experiment (after 10 days) indicating that the nitrite emerging at that time had not undergone significant chemical transformation during its passage through the column. Curve matching showed that nitrite behaviour could be represented by invoking chemical retardation using a retardation factor that begins at 2.5 and gradually decreases over time to a value of 1. However, the BTC for nitrite is better explained by the pH-dependent, chemical transformation of nitrite, presumably to nitrate or nitrogen gas, at the leading edge of the advancing chemical front that gives the appearance that nitrite is being retarded. Nitrite in more alkaline conditions behind the advancing front is significantly less affected by chemical transformation such that the apparent retardation effect diminishes. Further work is required to provide details on the nature of the reactions taking place and the constraints under which they operate.

A method for applying the James initiation criterion for explosives with thick cover plates is established. Impact data and corresponding shock induced detonation thresholds were collected and evaluated for flat steel projectiles of different diameters impacting PBX-9501 explosive charges covered by steel plates of various thicknesses. The analysis of the data demonstrated an improved prediction of the detonation thresholds of the explosive charges using the James criterion with a proper accounting of material strength effects, particularly for explosives with relatively thick cover plates. The approach is limited to impacts that produce a one-dimensional flow in the explosive.

Pumping-induced leakage across aquitards may induce a deterioration of water quality in multi-layer aquifer systems. It is critical to understand long-term trends of water quality parameters when assessing the sustainability of groundwater abstraction. Daily drinking water needs of 2.2 million people in Yinchuan region of northwest China are solely met by groundwater resources, but long-term groundwater withdrawal has created an extensive cone of depression (294 km2 in area) in confined aquifer causing increased vertical recharge. In this study, a model was established and calibrated with head data, then was incorporated with field tracer tests to provide key information on the hydro-dispersive characteristics of the contaminant for assessing both the current and future state of the aquifer system. The results confirmed a close association between water quality deterioration and high downward fluxes of high chloride groundwater, most notably near the center of the cone of depression. On a temporal scale, water quality degradation remains slow, largely due to the high, pre-existing storage of good quality water. Modeling suggests that the water quality in the upper confined aquifer will lose its potability over a 25 km2 and 50 km2 area within 200 years under the current and intensified pumping conditions, respectively. Elevated chloride values were also detected toward the east of the cone, highlighting the impact of hydrological settings on the vertical groundwater flow. Modeling of potential aquifer remediation shows an even slower response with a further 250 years or more required for potability to be restored in affected areas. The findings can provide valuable guidance to for decision makers and support the sustainable management of aquifer exploitation.

Isotopes and major ion hydrochemistry are used to investigate potential sources of nitrate contamination in shallow aquifers along the northern slope of the Qinling Mountains, west-central China. Locally, nitrate concentrations exceed a remarkable 850 mg/L, over 40 times background levels observed in fresh mountain springs, and a knowledge and understanding of the nitrate pollution sources is essential for the development of aquifer management and protection strategies that will allow the problem to be effectively controlled. Presently, none of the suspected pollutant sources generates concentrations of nitrate that even approach levels observed in the groundwater, and this is clearly a challenge in terms of assigning responsibility for the contamination and developing appropriate management plans. However, stable isotopes of hydrogen and oxygen (δD and δ18O) in study area waters demonstrate that the centrally located Jijiahe Reservoir and Shidi River have been a major source of aquifer recharge in recent times and are an obvious source of the contamination. Moreover, δ15N–NO3– and δ18O–NO3– determinations suggest that, while nitrate concentrations in the river and reservoir are currently relatively low, a local, long-established fertilizer factory that has likely released high-nitrogen waste to these nearby receptors in the past, is the primary pollutant source. On a positive note, it would appear that the majority of the nitrate contamination, albeit serious in terms of drinking water quality, represents a legacy of past practice and should show gradual improvement due to modern-day environmental protection initiatives, improved equipment, better monitoring and significantly enhanced methods of wastewater treatment. However, the isotope data do indicate that the aquifer continues to be impacted by other anthropogenic activities, including agriculture and livestock raising, downstream of the industrial area and in the eastern part of the study area, meaning that monitoring and active remediation strategies need to be continued with vigilance.