As numerical modeling is an effective tool for managing groundwater resources and predicting future responses, in this study, the author has intended to assess groundwater flow through Modflow 6 and Model Muse into Po...As numerical modeling is an effective tool for managing groundwater resources and predicting future responses, in this study, the author has intended to assess groundwater flow through Modflow 6 and Model Muse into Pointe-Noire coastal aquifers. The results showed that the fourth scenario has the biggest effect on the drawdown and seawater intrusion extent. Different parameters including evapotranspiration, recharge, model boundary, etc. were adjusted to run the model. The fourth scenario with the highest pumping rate value caused a slight increase of head values over the values simulated.展开更多
Naturally occurring radium(^(223)Ra,^(224)Ra,^(226)Ra,and^(228)Ra)isotopes have been widely applied as geochemical tracers in marine environments,especially when estimating the submarine groundwater discharge(SGD).In ...Naturally occurring radium(^(223)Ra,^(224)Ra,^(226)Ra,and^(228)Ra)isotopes have been widely applied as geochemical tracers in marine environments,especially when estimating the submarine groundwater discharge(SGD).In this sense,the influencing factors and transport mechanism of radium isotope activity in aquifers can be key information for SGD estimation.This work evaluates the adsorption/desorption behavior of^(224)Ra and^(226)Ra in the solid-liquid phase through a leaching experiment and analysis of field data.The results suggested that radium isotope activity was positively correlated with salinity and grain size,in the case of abundant sediments.Through ion analysis,we found that the ions(Na^(+),Ca^(2+),Mg^(2+),and Ba^(2+))exchanged with radium isotopes in the process of transport.A 1-D reactive transport model was established to simulate the transport process of radium isotope in aquifers.The model successfully simulated the variation of radium isotope desorption activity with salinity and was subsequently verified in the field.This study contributes to the understanding of the geochemical behavior of radium isotopes in aquifers and provides guidance for selecting a suitable groundwater endmember in SGD estimation.展开更多
The synthesis of geological and petroleum research undertaken in the coastal Sedimentary Basin of the Pointe-Noire region enabled the establishment of a lithostratigraphic scale. It has been observed that the order in...The synthesis of geological and petroleum research undertaken in the coastal Sedimentary Basin of the Pointe-Noire region enabled the establishment of a lithostratigraphic scale. It has been observed that the order in which the series observed in outcrop and those encountered by deep wells succeed each other has allowed a value to be given to this relative scale. The study area corresponds to a longitudinal tectonic accident, fault or flexure. It belongs to the Cretaceous and Tertiary coastal sedimentary basin covered by the Plio-Pleistocene age formations (series of circuses), formed of highly permeable sands comprising multiple resistant horizons that store large bodies of water whose reserves are considered very important. Hydrographic network is composed of four main basins with a mediocre size. The quality of this groundwater is considered to be satisfactory for household consumption, but the sustainable management of these reserves requires constant checks on their quality as well as on the level of the reserves. All these resources put the agglomeration of Pointe-Noire close to large exploitable water reserves that meet the need for drinking water, even if, on the whole, the agglomeration is still experiencing many difficulties in terms of its drinking water supply.展开更多
A model is traced to evaluate and enumerate the significance of vulnerability to seawater intrusion due to excessive ground water withdrawals and some anthropogenic activities at coastal aquifers. So taking these issu...A model is traced to evaluate and enumerate the significance of vulnerability to seawater intrusion due to excessive ground water withdrawals and some anthropogenic activities at coastal aquifers. So taking these issues into account few thematic maps which were influencing the saline water intrusion were prepared and overlaid using Geographical Information Systems (GIS). Based on GALDIT method, the groundwater vulnerability cartography has been assessed. To reckon the GALDIT index it requires six parameters like aquifer type, aquifer hydraulic conductivity, depth to groundwater level (AMSL), distance from the shore, impact of existing status of seawater intrusion and thickness of the aquifer. This GALDIT is the indicator scores and summing them and dividing by the total weight for determining the relative role of each one. Apart from this an identification of saltwater intruded area is done by using indicators of saltwater intrusion like Cl/(HCO<sub>3</sub> + CO<sub>3</sub>) ratio and Na/Cl ratio. The vulnerability areas are classified as moderate with an area of 147.31 sq. km and low covering an area of 168.72 sq. km respectively based on the thematic maps. The final thematic map can be used for management of the coastal ground water resources.展开更多
The estuary-bay system is a common and complex coastal environment.However,quantifying submarine groundwater discharge(SGD)and associated nutrient fluxes in the complex coastal environment is challenging due to more d...The estuary-bay system is a common and complex coastal environment.However,quantifying submarine groundwater discharge(SGD)and associated nutrient fluxes in the complex coastal environment is challenging due to more dynamic and complicated riverine discharge,ocean processes and human activities.In this study,SGD and SFGD(submarine fresh groundwater discharge)fluxes were evaluated by combining stable and radium isotopes in the Guangdong-Hong Kong-Macao Greater Bay Area(GBA),a typical estuary-bay system.We first built a spatially distributed radium mass balance model to quantify SGD fluxes in coastal areas of GBA integrating the Pearl River Estuary(PRE),bays and shelf.We then used the stable water isotope(d2 H and d18O)end-member mixing model to distinguish submarine fresh groundwater discharge(SFGD)from SGD.Based on the 228Ra mass balance,the estimated SGD fluxes in the PRE,adjacent bay,and shelf areas were(6.14±2.74)×10^(8) m^(3) d^(-1),(3.00±1.11)×10^(7) m^(3) d^(-1),and(5.00±5.64)×10^(8) m^(3) d^(-1),respectively.Results showed that the largest area-averaged SGD was in the PRE,followed by that in the adjacent shelf and the bay.These differences may be mainly influenced by ocean forces,urbanization and benthic topographies controlling the variability of groundwater pathways.Further,the three end-member mixing model of ^(228)Ra and salinity was developed to confirm the validity of the estimated SGD using the Ra mass balance model.In the two models,groundwater endmember and water apparent age estimation were the main sources of uncertainty in SGD.The estimated SFGD flux was(1.39±0.76)108 m^(3) d^(-1),which accounted for approximately 12%of the total SGD.Combining stable and radium isotopes was a useful method to estimate groundwater discharge.Moreover,the estimated SGD associated dissolved inorganic nitrogen(DIN)flux was one order of magnitude higher than other DIN sources.SGD was considered to be a significant contributor to the DIN loading to the GBA.The findings of this study are expected to provide valuable information on coastal groundwater management and environmental protection of the GBA and similar coastal areas elsewhere.展开更多
The coastal plain aquifer down gradient of Wad Essaquia Elhamra(WEE),is the main source of groundwater in the arid region of Laayoune Essaquia El Hamra located in south of Morocco.The over-exploitation of this aquifer...The coastal plain aquifer down gradient of Wad Essaquia Elhamra(WEE),is the main source of groundwater in the arid region of Laayoune Essaquia El Hamra located in south of Morocco.The over-exploitation of this aquifer over the last decade for water supply,agriculture and industry led to deterioration of groundwater quality,including seawater intrusion.The objective of this study is to investigate the spatial variation of groundwater quality,and to assess the influence of sea water intrusion on the groundwater quality using hydro-chemical tools.Several measurement campaigns of physico-chemical parameters of the groundwater were performed,which shows a very high mineralization ratios versus chloride,confirming the double influence of mixing mechanisms of fresh and saline waters and the water-rock interactions.Computed seawater fraction for sampled water shows that the average mixing rate of seawater intrusion reached 10.5%,confirming the marine intrusion in the aquifer.The highest values were registered in coastal wells.In the upstream around Laayoune and the spreading area,nitrate concentrations exceed 50 mg/L which is the threshold set by the World Health Organization,revealing a high level of contamination by domestic sewage.The combination of ionic ratios and seawater fraction is a useful tool to assess marine intrusion.This study reveals that the phenomenon of marine intrusion is not the only process that dominates hydrochemistry of ground water.The high groundwater mineralization is also due to rockwater interaction associated with reverse ion exchange with clay material and anthropogenic pollutants.展开更多
文摘As numerical modeling is an effective tool for managing groundwater resources and predicting future responses, in this study, the author has intended to assess groundwater flow through Modflow 6 and Model Muse into Pointe-Noire coastal aquifers. The results showed that the fourth scenario has the biggest effect on the drawdown and seawater intrusion extent. Different parameters including evapotranspiration, recharge, model boundary, etc. were adjusted to run the model. The fourth scenario with the highest pumping rate value caused a slight increase of head values over the values simulated.
基金The Joint Funds of the National Natural Science Foundation of China under contract Nos U22A20580 and U2106203the National Natural Science Foundation of China under contract No.41706067the Open Project Program of Key Laboratory of Ecological Warning,Protection&Restoration for Bohai Sea,Ministry of Natural Resources under contract No.2022108.
文摘Naturally occurring radium(^(223)Ra,^(224)Ra,^(226)Ra,and^(228)Ra)isotopes have been widely applied as geochemical tracers in marine environments,especially when estimating the submarine groundwater discharge(SGD).In this sense,the influencing factors and transport mechanism of radium isotope activity in aquifers can be key information for SGD estimation.This work evaluates the adsorption/desorption behavior of^(224)Ra and^(226)Ra in the solid-liquid phase through a leaching experiment and analysis of field data.The results suggested that radium isotope activity was positively correlated with salinity and grain size,in the case of abundant sediments.Through ion analysis,we found that the ions(Na^(+),Ca^(2+),Mg^(2+),and Ba^(2+))exchanged with radium isotopes in the process of transport.A 1-D reactive transport model was established to simulate the transport process of radium isotope in aquifers.The model successfully simulated the variation of radium isotope desorption activity with salinity and was subsequently verified in the field.This study contributes to the understanding of the geochemical behavior of radium isotopes in aquifers and provides guidance for selecting a suitable groundwater endmember in SGD estimation.
文摘The synthesis of geological and petroleum research undertaken in the coastal Sedimentary Basin of the Pointe-Noire region enabled the establishment of a lithostratigraphic scale. It has been observed that the order in which the series observed in outcrop and those encountered by deep wells succeed each other has allowed a value to be given to this relative scale. The study area corresponds to a longitudinal tectonic accident, fault or flexure. It belongs to the Cretaceous and Tertiary coastal sedimentary basin covered by the Plio-Pleistocene age formations (series of circuses), formed of highly permeable sands comprising multiple resistant horizons that store large bodies of water whose reserves are considered very important. Hydrographic network is composed of four main basins with a mediocre size. The quality of this groundwater is considered to be satisfactory for household consumption, but the sustainable management of these reserves requires constant checks on their quality as well as on the level of the reserves. All these resources put the agglomeration of Pointe-Noire close to large exploitable water reserves that meet the need for drinking water, even if, on the whole, the agglomeration is still experiencing many difficulties in terms of its drinking water supply.
文摘A model is traced to evaluate and enumerate the significance of vulnerability to seawater intrusion due to excessive ground water withdrawals and some anthropogenic activities at coastal aquifers. So taking these issues into account few thematic maps which were influencing the saline water intrusion were prepared and overlaid using Geographical Information Systems (GIS). Based on GALDIT method, the groundwater vulnerability cartography has been assessed. To reckon the GALDIT index it requires six parameters like aquifer type, aquifer hydraulic conductivity, depth to groundwater level (AMSL), distance from the shore, impact of existing status of seawater intrusion and thickness of the aquifer. This GALDIT is the indicator scores and summing them and dividing by the total weight for determining the relative role of each one. Apart from this an identification of saltwater intruded area is done by using indicators of saltwater intrusion like Cl/(HCO<sub>3</sub> + CO<sub>3</sub>) ratio and Na/Cl ratio. The vulnerability areas are classified as moderate with an area of 147.31 sq. km and low covering an area of 168.72 sq. km respectively based on the thematic maps. The final thematic map can be used for management of the coastal ground water resources.
基金supported by the National Natural Science Foundations of China(Nos.41890852,42077173)the Shenzhen Science and Technology Innovation Committee(No.JCYJ20190809142417287)State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control.
文摘The estuary-bay system is a common and complex coastal environment.However,quantifying submarine groundwater discharge(SGD)and associated nutrient fluxes in the complex coastal environment is challenging due to more dynamic and complicated riverine discharge,ocean processes and human activities.In this study,SGD and SFGD(submarine fresh groundwater discharge)fluxes were evaluated by combining stable and radium isotopes in the Guangdong-Hong Kong-Macao Greater Bay Area(GBA),a typical estuary-bay system.We first built a spatially distributed radium mass balance model to quantify SGD fluxes in coastal areas of GBA integrating the Pearl River Estuary(PRE),bays and shelf.We then used the stable water isotope(d2 H and d18O)end-member mixing model to distinguish submarine fresh groundwater discharge(SFGD)from SGD.Based on the 228Ra mass balance,the estimated SGD fluxes in the PRE,adjacent bay,and shelf areas were(6.14±2.74)×10^(8) m^(3) d^(-1),(3.00±1.11)×10^(7) m^(3) d^(-1),and(5.00±5.64)×10^(8) m^(3) d^(-1),respectively.Results showed that the largest area-averaged SGD was in the PRE,followed by that in the adjacent shelf and the bay.These differences may be mainly influenced by ocean forces,urbanization and benthic topographies controlling the variability of groundwater pathways.Further,the three end-member mixing model of ^(228)Ra and salinity was developed to confirm the validity of the estimated SGD using the Ra mass balance model.In the two models,groundwater endmember and water apparent age estimation were the main sources of uncertainty in SGD.The estimated SFGD flux was(1.39±0.76)108 m^(3) d^(-1),which accounted for approximately 12%of the total SGD.Combining stable and radium isotopes was a useful method to estimate groundwater discharge.Moreover,the estimated SGD associated dissolved inorganic nitrogen(DIN)flux was one order of magnitude higher than other DIN sources.SGD was considered to be a significant contributor to the DIN loading to the GBA.The findings of this study are expected to provide valuable information on coastal groundwater management and environmental protection of the GBA and similar coastal areas elsewhere.
文摘The coastal plain aquifer down gradient of Wad Essaquia Elhamra(WEE),is the main source of groundwater in the arid region of Laayoune Essaquia El Hamra located in south of Morocco.The over-exploitation of this aquifer over the last decade for water supply,agriculture and industry led to deterioration of groundwater quality,including seawater intrusion.The objective of this study is to investigate the spatial variation of groundwater quality,and to assess the influence of sea water intrusion on the groundwater quality using hydro-chemical tools.Several measurement campaigns of physico-chemical parameters of the groundwater were performed,which shows a very high mineralization ratios versus chloride,confirming the double influence of mixing mechanisms of fresh and saline waters and the water-rock interactions.Computed seawater fraction for sampled water shows that the average mixing rate of seawater intrusion reached 10.5%,confirming the marine intrusion in the aquifer.The highest values were registered in coastal wells.In the upstream around Laayoune and the spreading area,nitrate concentrations exceed 50 mg/L which is the threshold set by the World Health Organization,revealing a high level of contamination by domestic sewage.The combination of ionic ratios and seawater fraction is a useful tool to assess marine intrusion.This study reveals that the phenomenon of marine intrusion is not the only process that dominates hydrochemistry of ground water.The high groundwater mineralization is also due to rockwater interaction associated with reverse ion exchange with clay material and anthropogenic pollutants.
