•Mean residence times of shallow groundwater were aged by tritium time-series data.•A negative correlation between groundwater age and ions was demonstrated.•Groundwater became more vulnerable to ...anthropogenic contaminants under intensive exploitation.
The deterioration of water quality in shallow groundwater systems over the past decades has attracted increased amounts of attention from hydrogeologists. Groundwater vulnerability and its changes are the factors that cause groundwater deterioration. Combining of the mean residence times (MRTs) with chemical characteristics of groundwater can be applied to understand groundwater vulnerability and its changes. The groundwater MRTs ranged from 6 to 180 years, with MRTs of 6 to 77 years in the shallow aquifer. Spatial distribution of groundwater MRTs suggested that young groundwater trended to extend. Relatively uniform MRTs and concentrations of ions were found above the main pumped well depth. High concentrations of ions (K+, Na+, Ca2+, Mg2+, HCO3−, Cl- and SO42-) were mainly distributed in the western piedmont plain areas with short turnover time but with low productivity, meaning that the aquifer is susceptible to human activities and hardly migrate out. Elevated concentrations of nitrate and others ions (such as K+, Ca2+, Cl- and SO42-) also were observed in moderately old groundwater (20 < MRTs < 80 years), indicating that some mixing with recent water within MRTs < 20 years likely occurs through vertical drainage from the upper to deeper in the single aquifer and that lateral flow occurs along flow paths towards the piezometric depressions caused by the pumping in urban areas. Slightly elevated HCO3− and K+ were found at east of the areas with long residence times suggested that water-salt equilibrium had also been disrupted. Therefore, the anthropogenic influence exceeded the natural attenuation in the current groundwater environment on the piedmont plain. And the Shijiazhuang groundwater system was identified to be tending more vulnerable under anthropogenic influence. Some measures must be taken to significantly reduce groundwater withdrawal and pollutant discharge.
The source characterization of nitrate (NO
3
−
) in groundwater of Muling-Xingkai Plain (MXP) and the influence of NO
3
−
on the water environment were studied by hydrogeochemical and multivariate ...statistical analysis. A total of 164 groundwater samples were collected, and the samples were classified into three clusters by using hierarchical cluster analysis. Cluster 1 (C1), accounting for 13% of total samples, was mainly located in local residential zones where the top soils were the medium-textured sediments. Cluster 2 (C2) and cluster 3 (C3) were mainly located in farmlands and residential zones where the clay sediments were overlaying the aquifers. The soil media covering the aquifers was an important factor controlling the concentration of NO
3
−
in groundwater, which determined the infiltration rate of wastewater and the redox environment of aquifers. Only the samples in C1 exceeded the WTO standards for NO
3
−
(50 mg/L), and the samples in C2 and C3 had low NO
3
−
concentration (less than 10 mg/L). The excessive NO
3
−
in groundwater was observed in the shallow groundwater under local residential zones, and it was closely related to the anthropogenic activities since the 1950s. The domestic sewage was responsible for the elevated NO
3
−
contents in the MXP. Then, it was still necessary to construct the sewage disposal system in rural areas to further protect the groundwater resource to avoid the formation of extensive nitrogen pollution. At present, NO
3
−
in the groundwater mainly shows a fertilizer and natural rainwater origin and is not demonstrating the significant deterioration of groundwater qualities and water environment.
The use of isotope tracers as a tool for assessing aquifer responses to intensive exploitation is demonstrated and used to attain a better understanding of the sustainability of intensively exploited ...aquifers in the North China Plain. Eleven well sites were selected that have long-term (years 1985–2014) analysis data of isotopic tracers. The stable isotopes δ
18
O and δ
2
H and hydrochemistry were used to understand the hydrodynamic responses of the aquifer system, including unconfined and confined aquifers, to groundwater abstraction. The time series data of
14
C activity were also used to assess groundwater age, thereby contributing to an understanding of groundwater sustainability and aquifer depletion. Enrichment of the heavy oxygen isotope (
18
O) and elevated concentrations of chloride, sulfate, and nitrate were found in groundwater abstracted from the unconfined aquifer, which suggests that intensive exploitation might induce the potential for aquifer contamination. The time series data of
14
C activity showed an increase of groundwater age with exploitation of the confined parts of the aquifer system, which indicates that a larger fraction of old water has been exploited over time, and that the groundwater from the deep aquifer has been mined. The current water demand exceeds the sustainable production capabilities of the aquifer system in the North China Plain. Some measures must be taken to ensure major cuts in groundwater withdrawals from the aquifers after a long period of depletion.
The appropriate division of underground drinking water source protection zones is a low-cost method of preventing water source pollution and ensuring a supply of safe drinking water. Based on FEFLOW, ...a groundwater flow model of large water sources was established for Luan River, North China. Trace lines of particle reverse migration for 100 and 1000 days were obtained by random walks. According to the trace morphology, the water sources in the riverside water source area were divided into four categories. The first- and second-grade protection areas were delimited by ArcGIS, with areas of 0.375 and 1.20 km2. The local and global sensitivity of the permeability coefficient (K) and effective porosity (ne) effects on the area of groundwater protection zones were calculated. The area of the protection zones was positively correlated with K and negatively correlated with ne. The variation in the protected zone caused by the simultaneous changes in K and ne is the same as that of ne alone, and the global sensitivity is closer to the local sensitivity of ne. This indicates that ne has a greater impact than K on the scope of groundwater protection zones. Moreover, global sensitivity is not simply a superposition of local sensitivity, and the interaction between parameters can reduce the effect of a parameter acting alone on the delineation of protection zones. This also shows that the global sensitivity is closer to the actual situation than the local sensitivity, thus providing a scientific basis for the delimitation and monitoring of water source protection zones.
Rivers are the main supply sources in inland areas for human activities, but they are also regarded as the most susceptible water bodies to pollutants. Understanding the key factors influencing the ...chemical characteristic is the basis for water supply and public health concern. And it is helpful for the protection of surface water under the influence of human activities. To reveal the hydrochemical process of river water and the key factors affecting the chemical compositions, a total of 33 samples from rivers in Muling-Xingkai Plain are collected for principal component analysis and hydrochemical analysis. Results indicate that river water is characterized by the type of HCO
3
-Ca and mixed HCO
3
-Ca·Na. But some samples with relative high nitrate content have Cl
−
as the dominant anion. The natural sources of chemical ions in river water are silicate and carbonate minerals. The chemical fertilizers only slightly influence the chemical compositions of river water due to the retardation of black soil with weak permeability. The chemical compositions of river water in Muling river are significantly influenced by domestic sewage compared with that in Abuqin river and Qihulin river. The widespread thick black soils play a key roles in protecting the river quality and groundwater quality, and human activities only play a limited roles in determining the river quality in the Muling-Xingkai Plain. At present, the contents of major chemical ions in river water meet the irrigation standard. Although the irrigation with river water do not lead to the food safety issue, the government agencies should adopt adequate measures to control the indiscriminate discharge of domestic sewage and application of fertilizers for preventing the accumulation of pollutants in rivers. This study is beneficial to the efficient management of surface water resources in agricultural areas with similar geological conditions and hydrogeological conditions.
Groundwater quality in the Muling–Xingkai Plain (MXP) is closely related to food security and human health. The chemical composition of groundwater in MXP has attracted great attention. A total of ...168 groundwater samples were collected in MXP, and principal component analysis, chemical ion analysis and stable isotopic analysis were used to explore key factors affecting the chemical composition and hydrochemical evolution process of groundwater. Results show sources of chemical ions in groundwater are silicate minerals, carbonate minerals and domestic sewage. Domestic sewage is responsible for groundwater with high levels of Cl−, SO42− and NO3−, but a reduction environment can lead to groundwater with a high level of NH4+ due to nitrification. Human activity and soil media together influence groundwater chemical composition. Groundwater with a high level of chemical ions is mainly collected from wells near river channels, where coarse-textured soils are overlying aquifers. The black soil far away from river channels can retard the infiltration of wastewater. Agricultural activities do not directly lead to deterioration of groundwater qualities, and agricultural non-point-source pollution does not occur in MXP. Nearly 70% of the population in MXP is living in the southern plain, where the influence of sewage on groundwater chemical composition is obvious. Thus, shallow groundwater far away from river channels is the best choice for irrigation. Some measures should be implemented to control the discharge of domestic sewage for the protection of groundwater. In addition, it is necessary to avoid the transformation of the redox environment of groundwater in the northern plain.
The stress imposed on groundwater resources due to intensively exploited aquifer has resulted in groundwater depletion in the North China Plain (NCP). Management of groundwater resources needs to ...understand the changes or dynamic responses due to the exploitation. The response of groundwater systems to intensive exploitation and groundwater availability were assessed by the combined use of conventional hydrochemical data and environmental isotopes in Shijiazhuang, NCP. The generally increased concentration of total dissolved solids (TDS), major cation and anion of groundwater in the past 40 years indicated high vulnerability of aquifer system but a short turn over time by intensive groundwater exploitation, which also was proved by changes of groundwater renewal rate estimated by tritium. The vertical distribution of tritium in aquifers showed that the active groundwater recharge zone has been extended from the depth of 100 to ~150 m since 1985, indicating an enhancement of active groundwater flushing of local groundwater system due to intensive groundwater abstraction. The enrichment trend of δ
18
O and δ
2
H value with groundwater abstraction, suggested the impacts of local recharge from irrigation return. The increase concentrations of nitrate with time indicated high aquifer vulnerability. A comprehensive effort should be developed for effective management strategies that ensure long-term, stable, and flexible water supplies to meet water demands in the NCP.
The stress imposed on groundwater resources due to intensively exploited aquifer has resulted in groundwater depletion in the North China Plain（NCP）. Management of groundwater resources needs to ...understand the changes or dynamic responses due to the exploitation. The response of groundwater systems to intensive exploitation and groundwater availability were assessed by the combined use of conventional hydrochemical data and environmental isotopes in Shijiazhuang, NCP. The generally increased concentration of total dissolved solids（TDS）, major cation and anion of groundwater in the past 40 years indicated high vulnerability of aquifer system but a short turn over time by intensive groundwater exploitation, which also was proved by changes of groundwater renewal rate estimated by tritium. The vertical distribution of tritium in aquifers showed that the active groundwater recharge zone has been extended from the depth of 100 to 150 m since 1985, indicating an enhancement of active groundwater flushing of local groundwater system due to intensive groundwater abstraction. The enrichment trend of δ18O and δ2H value with groundwater abstraction, suggested the impacts of local recharge from irrigation return. The increase concentrations of nitrate with time indicated high aquifer vulnerability. A comprehensive effort should be developed for effective management strategies that ensure long-term, stable, and flexible water supplies to meet water demands in the NCP.
The stress imposed on groundwater resources due to intensively exploited aquifer has resulted in groundwater depletion in the North China Plain（NCP）. Management of groundwater resources needs to ...understand the changes or dynamic responses due to the exploitation. The response of groundwater systems to intensive exploitation and groundwater availability were assessed by the combined use of conventional hydrochemical data and environmental isotopes in Shijiazhuang, NCP. The generally increased concentration of total dissolved solids（TDS）, major cation and anion of groundwater in the past 40 years indicated high vulnerability of aquifer system but a short turn over time by intensive groundwater exploitation, which also was proved by changes of groundwater renewal rate estimated by tritium. The vertical distribution of tritium in aquifers showed that the active groundwater recharge zone has been extended from the depth of 100 to ~150 m since 1985, indicating an enhancement of active groundwater flushing of local groundwater system due to intensive groundwater abstraction. The enrichment trend of δ~（18）O and δ~2H value with groundwater abstraction, suggested the impacts of local recharge from irrigation return. The increase concentrations of nitrate with time indicated high aquifer vulnerability. A comprehensive effort should be developed for effective management strategies that ensure long-term, stable, and flexible water supplies to meet water demands in the NCP.
Thick loess is deposited on the platform in the piedmont zone of Muling-Xingkai Plain (Muxing Plain), but the genesis of the Muxing loess is still unclear. The aims of this study are to analyze the ...grain size characteristics of Muxing loess collected from the cores of a typical borehole (ZK1) in the piedmont zone of Muxing Plain, and to verify its genesis. The Muxing loess is mainly composed of the particles with diameter less than 50 μm, with an average content of 92.48%. The coarse silt particles with diameter of 10-50 μm are the basic composition of aeolian sediments, and their average content is 44.34% for the Muxing loess, which is the mode class among the particles with different diameters. The grain size parameters and frequency curves are similar to those of the typical aeolian sediments. The distribution characteristic of the Muxing loess in the C-M scatter diagram is consistent with that of the Xi Feng loess. In addition, the discriminant analysis shows the Muxing loess mostly consists of aeolian sediments. Therefore, it can be concluded that the Muxing loess mainly resulted from aeolian deposition based on the grain size characteristics. Muxing Plain is dominated by the monsoon climate, and the wind-blown dusts are gradually deposited after being transported over long distances.
