Shallow Groundwater Quality Research Articles

Prediction of 1,2,4-trichlorobenzene natural attenuation in groundwater at a landfill in Kaifeng, China

1,2,4-trichlorobenzene (1,2,4-TCB) is one of the most common pollutants in landfill leachate that impacts shallow drinking groundwater quality; accordingly, the transport mechanism and capacity for remediation of this compound are important to the management of local water resource. In this study, a series of indoor experiments and analytical predictions revealed that the transportation of 1,2,4-TCB in groundwater is similar in medium sand and fine sand. Specifically, the peak time increases with distance between monitoring points and the source point, but the peak relative concentrations decrease with distance, indicating that the concentration of 1,2,4-TCB in groundwater is controlled by adsorption and biodegradation. In addition, transportation of water in a fine sand column was lower than that in a medium sand column; therefore, the adsorption and biodegradation of 1,2,4-TCB in groundwater was lower in the medium sand column. These findings demonstrate that 1,2,4-TCB in groundwater could be removed by natural degradation after about 5 years, but that other methods (permeable reactive barriers, air sparging or biosparging) should be applied in the field to shorten the remediation period and enhance water supply safety around landfill.

Reactive transport controls on sandy acid sulfate soils and impacts on shallow groundwater quality

AbstractDisturbance or drainage of potential acid sulfate soils (PASS) can result in the release of acidity and degradation of infrastructure, water resources, and the environment. Soil processes affecting shallow groundwater quality have been investigated using a numerical code that integrates (bio)geochemical processes with water, solute, and gas transport. The patterns of severe and persistent acidification (pH < 4) in the sandy, carbonate‐depleted podzols of a coastal plain could be reproduced without calibration, based on oxidation of microcrystalline pyrite after groundwater level decrease and/or residual groundwater acidity, due to slow vertical solute transport rates. The rate of acidification was limited by gas phase diffusion of oxygen and hence was sensitive to soil water retention properties and in some cases also to oxygen consumption by organic matter mineralization. Despite diffusion limitation, the rate of oxidation in sandy soils was rapid once pyrite‐bearing horizons were exposed, even to a depth of 7.5 m. Groundwater level movement was thus identified as an important control on acidification, as well as the initial pyrite content. Increase in the rate of Fe(II) oxidation lead to slightly lower pH and greater accumulation of Fe(III) phases, but had little effect on the overall amount of pyrite oxidized. Aluminosilicate (kaolinite) dissolution had a small pH‐buffering effect but lead to the release of Al and associated acidity. Simulated dewatering scenarios highlighted the potential of the model for risk assessment of (bio)geochemical impacts on soil and groundwater over a range of temporal and spatial scales.

Vegetative Treatment System Impacts on Groundwater Quality

<abstract><title><italic>Abstract.</italic></title> Increased environmental awareness has prompted the need for improved feedlot runoff control. Vegetative treatment systems (VTSs) provide a cost-effective option that may enhance environmental security by protecting water quality. Vegetative treatment systems are typically designed on the basis of hydraulic performance, which may result in excess application of some nutrients, specifically nitrogen and phosphorus. Groundwater quality monitoring is required to determine the effect, if any, that VTSs have on groundwater. Shallow groundwater (2 to 10 m) quality beneath six VTSs in Iowa was monitored over a four-year period. Monitoring wells were located upgradient, within, and downgradient of the VTSs. Groundwater samples were collected on a monthly basis and analyzed for ammoniacal nitrogen, chloride, nitrate-nitrogen, and fecal coliforms. A trend analysis was conducted to evaluate groundwater response patterns to VTS construction and use. In general, monitoring wells located within and downgradient of the VTS showed increasing trends in chloride and decreasing trends in nitrate concentrations. No trends for fecal coliforms or ammoniacal nitrogen were seen. Statistical analysis was performed to test for concentration differences between upgradient, within, and downgradient monitoring wells. In general, no differences in ammoniacal nitrogen concentration were seen. Fecal coliform concentrations were generally highest at the monitoring well within the VTS, but no difference was found between upgradient and downgradient concentrations. Chloride concentrations were generally significantly higher within and downgradient of the VTS when compared to the upgradient well; nitrate concentrations were generally significantly lower within and downgradient of the VTA than upgradient.

Insights into interconnections between the shallow and deep systems from a natural CO2 reservoir near Springerville, Arizona

If carbon dioxide (CO2) sequestration into deep geologic reservoirs is to be accepted by the public and environmental regulators, the possibility of upward leakage into shallow groundwater should be acknowledged and those processes well-understood. Studies of natural CO2 reservoirs and their connection (or lack thereof) with the shallow subsurface is one way to explore these issues. A natural reservoir near Springerville, Arizona has leaked CO2 to the surface along a fault zone for thousands of years, creating large travertine deposits. In recent times, the CO2 leak rates have declined significantly yet the shallow aquifer is still highly enriched in CO2. In this study, using water level data and simulations we demonstrate that the fault zone likely provides hydrologic communication between the shallow aquifer and the deeper reservoir. It is reasonable to assume, therefore, that the source of the CO2 in wells completed within the fault zone is the deeper CO2 reservoir. We present water chemistry data to demonstrate the geochemical impact of this CO2 on shallow groundwater quality. Interestingly, arsenic concentrations are elevated, but other trace metals concentrations are not. Arsenic and chloride concentrations co-vary, suggesting perhaps an external source of both elements rather than an in situ release of As due to CO2 attack on shallow aquifer sediments. Observations at this site demonstrate that hydraulic communications between shallow and deep layers and upward CO2 migration does not preclude long-term viability of a substantial CO2 reservoir at depth. We present multi-phase flow simulations to illustrate possible mechanisms trapping the CO2 at depth. Collectively, these analyses show that some degree of upward CO2 leakage may not be necessarily incompatible with the overarching goals of sequestering CO2 and protecting shallow groundwater.

The Analysis of Shallow Groundwater Quality around Laemchabang Sanitary Landfill, Chonburi, Thailand

This study focused on quality of shallow groundwater collected around Laemchabang sanitary landfill Chonburi Province, Thailand. The sixteen public shallow wells were collected and analyzed for pH, cations (Ca2+, Mg2+, Na+ and K+), anions (HCO-3, Cl- and SO4 2-) and metals (As, Fe, Mn, Zn and Al). The results were reported by statistical and correlation techniques. It was found that, in some wells, metals such as Fe and Mn exceeded the acceptable limits. Thus, shallow groundwater around Laemchabang Sanitary Landfill would not be suitable for drinking. According to correlation analysis, pH value is positively correlated with HCO-3, Fe and Al. Ca2+ and Mg2+ are positively correlated with HCO-3 and Cl-. Arsenic is positively correlated with Fe and Mn. Most shallow groundwater samples in this area are the mixed type, Ca (Mg)Cl (SO4) type, which may occur from water-rock interaction and leakage from landfill to groundwater system.

Hydrological and Geomorphological Controls on the Water Balance Components of a Mangrove Forest During the Dry Season in the Pacific Coast of Nicaragua

Hydrological and geomorphological processes are key to mangrove forest growth and development. However, few mangrove hydrology studies exist in Central America. A 0.2 km2 mangrove forest on the Pacific coast of Nicaragua was investigated to determine the water balance dynamics during the dry season. The used multi-methods approach combined hydrology, hydrochemistry and geophysics. Precipitation is the main freshwater input. Beach ridges are the key geomorphologic features which allowed an increase in water storage of 351 m3d−1 during a 22 day period. Large precipitation events cause breaking of the beach ridges by excess water, suddenly emptying the system. Grey water and pit latrines from the nearby town influence shallow groundwater quality, but also provide extra nutrients for the mangrove forest. Groundwater chemistry is also affected by calcite dissolution and seawater. Refreshening and salinization processes are controlled by the general groundwater flow direction. Hydraulic and hydrochemical influence of seawater on coastal piezometers seems to be controlled by the elevation of the water table and the tidal amplitude. These conditions control forest subsistence during the dry season, which is essential for the mangrove forest to provide ecological and economic benefits such as protection against flooding, habitat for numerous species, and tourist attraction.

Vulnerability of Eco-Hydrological Environment in the Yellow River Delta Wetland

Gao, M.; Liu, S.; Zhao, G.; Yuan, H.; Wei, C.; Wu, Y., and Tang, J., 2014. Vulnerability of eco-hydrological environment in the Yellow River delta wetland.We investigated the relationship between groundwater head and oceanic tidal fluctuations in the Yellow River Delta wetland through on-site hydrological monitoring. Shallow groundwater heads were obviously affected by oceanic tide along the coastal zone. The ranges of the wetland zone can be readily assessed by measuring fluctuation amplitudes or lags. The results show that the influence radius is approximately 12 km to 18 km (when the correlation coefficient is 0.7 to 0.8) under the joint actions of oceanic tide and shallow groundwater seepage flow in clayey silt coastal wetland. A cross-sectional sketch of the coastal wetland model is developed based on monitoring data of groundwater and oceanic tidal fluctuations to study the vulnerability of the eco-hydrological environment in the Yellow River Delta wetland. The coastal wetland consists of three zones (the groundwater seepage zone, the tidal-induced transitional zone, and the tidal zone) with distinctly different hydraulic properties. Analytical solutions are used to estimate the vulnerability of the eco-hydrological environment in the wetland aquifer located in the NE part of the Yellow River Delta wetland, Shandong Province, China. Our results show that changes in the shallow groundwater quality of the wetland are significantly affected by natural factors, such as strong cutoff in the lower reaches, storm tides, and human engineering activities. The northern coastal wetland may be submerged without damp proof when the height of a storm tide reaches 2.4 m. The depth of shallow groundwater and the salinity gradient are key factors that contribute to the vulnerability of the ecological environment. The vulnerability of the eco-hydrological environment is derived from the joint actions of groundwater dynamics, hydrochemistry, and tidal-induced processes under sedimentary stress and water pressure.

Impact of wastewater from pig farm lagoons on the quality of local groundwater

The objective of this study was to determine the degree of contamination of the shallow groundwater and the quality of drinking water, on the locations of three pig farms employing liquid manure cleaning systems, in lagoons without hydroisolation for storing wastewaters.For the purpose of monitoring the quality of shallow groundwater and its level, ten piezometers were installed on three pig farms, whereas the quality of drinking water was followed using samples from the local wells.The minimum fluctuations of shallow groundwater level were measured in the reference piezometers, whereas the highest variations (up to 4.19m) were detected in the piezometers drilled near the lagoons, indicating the infiltration of water from the lagoon. A significant correlation (P<0.001) between the amount of rainfall and the level of water in the piezometers, indicates the possible penetration of the pollutants from the earth surface to the groundwater. The measurements encompassed the physico-chemical parameters that characterize pig farm wastewater, viz. organic and suspended matter and dry matter. The results of measuring the parameters of wastewater, solid manure, and lagoon sediment indicate that efficient water purification occurred in the lagoons under natural conditions. The organic matter content in the lagoons was reduced by 85–90%, dry matter by 56–69%, suspended matter by 94–96%, total P by 31–50%, total N by 39–55%, Cu by 69–85%, and Zn by 83–89%. The results also show that most of the metals settled on the bed of the lagoon, reducing thus the risk of contamination of surface water and groundwater.The investigation showed large variations in the parameters of shallow groundwater on the locations of the farms. The concentrations of NH4+-N in water of the reference piezometers ranged between 0.02 and 1.52mg/L, while in the piezometers close to the lagoons they were up to 52.6mg/L. The content of total N in the reference piezometers was between 0.14 and 22.4mg/L, while in the piezometers close to the source of contamination it reached 90.4mg/L. Also, at one of the farms the amounts of P and Cl− measured in the piezometers close to the lagoon were up to 7 and 5 times higher than in the reference piezometer. The correlations between electrical conductivity (EC) and Cl−, SO42−, Na+, K+, between total N and NH4+-N, NO3−-N and organic N by Kjeldahl (ONK) and various metals in the shallow groundwater, indicate their common origin from farm wastewaters.On the other hand, the results clearly indicate that there was no degradation of the quality of the drinking water in the deeper layers, and none of the drinking water quality parameters showed significant variation during the investigation period. This is explained by the presence of 4–6m thick clay layer between the lagoon and the drinking water aquifer.Overall, this study clearly shows that the pollution of shallow groundwater on the farms is of a local character, and that here is no significant pollution of groundwater sources, despite the fact that farms employing liquid manure cleaning systems have been in operation for many decades.

Further Insights Into Interconnections between the Shallow and Deep Systems from a Natural CO2 Reservoir Near Springerville, Arizona, U.S.A.

If carbon dioxide (CO 2 ) sequestration into deep geologic reservoirs is to be accepted by the public and environmental regulators, the possibility of upward leakage into shallow groundwater should be acknowledged and those processes well-understood. Studies of natural CO 2 reservoirs and their connection (or lack thereof) with the shallow subsurface is one way to explore these issues. A natural reservoir near Springerville, Arizona, U.S.A. has leaked CO 2 to the surface along a fault zone for thousands of years, creating large travertine deposits. In recent times, the CO 2 leak rates have declined significantly yet the shallow aquifer is still highly enriched in dissolved CO 2 . In previous studies, using water level data and simulations we demonstrate that the fault zone provides hydrologic communication between the shallow aquifer and the deeper reservoir. It is reasonable to assume, therefore, that the source of the CO 2 in wells completed within the fault zone is the deeper CO 2 reservoir. We present water chemistry data to demonstrate the geochemical impact of this CO 2 on shallow groundwater quality. Interestingly, arsenic concentrations are elevated, but other trace metals concentrations are not. Previous studies [1] , [2] , [3] showed that CO 2 originating from magmatic and deep crustal origin is migrating upward along the fault and dissolving into the shallow groundwater. Saline waters are also mixing, to a much lesser degree, but their source was unknown. Here we present strontium isotope data that clearly shows the source to be water/rock interactions with reservoir rocks, which include Paleozoic carbonates, evaporites and shale units.

Seasonal variation in the microbial quality of shallow groundwater in the Kathmandu Valley, Nepal

To develop effective groundwater pollution control strategies for the Kathmandu Valley, Nepal, seasonal variations in microbial quality and their underlying mechanisms must be understood. However, to date, there are no studies that address these topics. In this study, groundwater samples from dug wells were collected during the dry and wet seasons from 2009 to 2012, and Escherichia coli (E. coli) and total coliforms were analysed. Three wells were monitored each month for a year. Microbial concentrations in shallow groundwater were significantly higher during the wet season than during the dry season. Analyses of rainfall and E. coli concentrations in different seasons indicated that a high level of faecal material infiltration during the rainy season may have caused the seasonal variations in microbial quality. A moderate to strong relationship between E. coli concentrations and groundwater level suggested that the rise in groundwater levels during the wet season may be another reason for this variation. This long time-scale survey detected a significant decline in the microbial quality of shallow groundwater during the wet season as compared with the dry season. We propose that the infiltration of contaminants and change in groundwater level are the two probable mechanisms for the observed seasonal differences.

Isotopic and geochemical identification of main groundwater supply sources to an alluvial aquifer, the Allier River valley (France)

Summary Hydrodynamic, hydrochemical, and isotopic investigations were carried out on 18 points, including boreholes, piezometers, and surface waters, from February 2011 to August 2012, to assess groundwater quality in the unconfined shallow alluvial aquifer of the Allier River (one of the main tributary of the Loire River). The study area, located near the city of Clermont-Ferrand (France), plays an important socio-economic role as the alluvial aquifer is the major source of drinking water for about 100,000 inhabitants. The objective of the project aims at understanding the functioning of alluvial aquifers that occupy a pre-eminent position in the hydrogeologic landscape both for their economic role – production of drinking water and agricultural development – and for their ecological role. Moreover, this study also targets at determining the factors and processes controlling shallow groundwater quality and origin. The water circulates from the south, with a natural alimentation from the hills in the non-pumped part of the alluvial aquifer. In the pumping zone, this general behaviour is altered by the pumping that makes the water from the Allier River enter the system in a large proportion. Four end-members have been identified for the recharge of the alluvial groundwater: rainfall, Allier River, surrounding hills’ aquifer and the southern non-pumped part of the alluvial system. Results indicate that, despite the global Ca–HCO 3 water type of the groundwater, spatial variations of physico-chemical parameters do exist in the study area. Ionic concentrations increase from the Allier River towards east due either to the increase in the residence time or a mixing with groundwater coming from the aquifer’s borders. Stable isotopes of the water molecule show the same results: boreholes close to the river bank are recharged by the Allier River (depleted values), while boreholes far from the river exhibit isotopic contents close to the values of hills’ spring or to the southern part of the alluvial aquifer, both recharged by local precipitation. One borehole (B65) does not follow this scheme of functioning and presents values attesting of a probable sealing of the Allier River banks. Based on these results, the contribution of each end-member has been calculated and the functioning of the alluvial system determined.

Effect of Wastewater Treated by EM Reused for Irrigation on Shallow Groundwater Quality

In allusion to environmental pollution brought about by wastewater irrigation, EM technology was introduced to study the feasibility of EM application in wastewater irrigation. The results show that EC, NO3--N and TN value of EM treatment in shallow groundwater are all less than those of WW treatment as a whole. In all samples, 59.3% NO3--N values are in the alert status, and when irrigation amount reaches 360mm, treatment WW has caused shallow groundwater pollution. TN concentration in treatment WW-3 on June 27 and July 9 is more than 110 mg/L. It suggests that NO3--N can easily penetrate into shallow groundwater with wastewater irrigation and there is insurance of groundwater pollution in the long-term wastewater irrigation. It also indicates that application of wastewater treated by EM reused for irrigation is feasible. TP values are all very low and suggest the pollution of P does not happen.

Impact of Shallow Groundwater Quality Evolution in Kunming Urban by Human Activities

Chemical components of the groundwater change with time and space due to the influence of environmental geological conditions and human activities, where the human activity is one of the main factors which cause the deterioration of groundwater quality. In this paper, the monitoring data of shallow groundwater in Kunming urban has been collected and analyzed. The results indicates that with the acceleration of the industrialization and urbanization process, the chemical characteristics of groundwater have been changed, such as the total dissolved solid (TDS) and nitrogen, including ammonium nitrogen, nitrite nitrogen, and nitrate nitrogen concentration increase gradually. TDS and ammonium nitrogen can be used as indicators that reflect the influence of human activities on the shallow groundwater quality in Kunming urban and characterize obvious pollution of groundwater quality respectively. Based on the reason analysis for TDS increase in groundwater, basic mechanism of the influence of human activities on groundwater quality in the study areas are discussed, which is expected to provide scientific basis for pollution prevention and control of shallow groundwater quality in Kunming urban.

Research on Hydrochemistrical Characteristics of Shallow Groundwater from Huainan City

Based on previous studies, 130 shallow groundwater samples are collected from Huainan city according to some rules, and 21 indexes of the groundwater samples are tested by different instruments. Moreover, the important works have been done, including statistical characteristics of groundwater components, and divided different types of hydrochemistry, analyses of the relationships between the hardness and Ca2+/Na+, Mg2+/Na+, TDS and the ES. The correlation between heavy metals and conventional components has been discussed. Finally, main components have influence on the quality of shallow groundwater by the method of principal component analysis.

Major Ion Chemistry of Shallow Groundwater in the Dongsheng Coalfield, Ordos Basin, China

A hydrogeochemical study was conducted in the Dongsheng Coalfield, Ordos Basin, China, to identify the mechanisms responsible for the chemical compositions of the shallow groundwater and to document water quality with respect to agricultural and drinking supply standards, prior to mining. Tri-linear diagrams, principal component analysis, and correlation analysis were used to reveal the hydrogeochemical characteristics of the shallow groundwater, and the potential water–rock interactions. In general, the major cations and anions were present at low concentrations, but were relatively higher around Jiushenggong than elsewhere in the study area. Groundwater around Jiushenggong has a long residence time and is also subject to extensive evapotranspiration. The dominant hydrochemical facies are HCO3-Ca, HCO3-Na, and mixed HCO3-Ca·Na·Mg types. Increases in major ion concentrations along the flow path, including Na, Cl, and SO4, coincide with increases in total dissolved solids. The predominant mechanism controlling groundwater chemistry proved to be the dissolution of carbonates, gypsum, and halite. Cation exchange and mixing with local recharge water are also important factors. The shallow groundwater quality in the study area is suitable for agricultural and drinking purposes.

Characterization of shallow groundwater quality in the Lower St. Johns River Basin: a case study

Characterization of groundwater quality allows the evaluation of groundwater pollution and provides information for better management of groundwater resources. This study characterized the shallow groundwater quality and its spatial and seasonal variations in the Lower St. Johns River Basin, Florida, USA, under agricultural, forest, wastewater, and residential land uses using field measurements and two-dimensional kriging analysis. Comparison of the concentrations of groundwater quality constituents against the US EPA's water quality criteria showed that the maximum nitrate/nitrite (NO x ) and arsenic (As) concentrations exceeded the EPA's drinking water standard limits, while the maximum Cl, SO 4 (2-) , and Mn concentrations exceeded the EPA's national secondary drinking water regulations. In general, high kriging estimated groundwater NH 4 (+) concentrations were found around the agricultural areas, while high kriging estimated groundwater NO x concentrations were observed in the residential areas with a high density of septic tank distribution. Our study further revealed that more areas were found with high estimated NO x concentrations in summer than in spring. This occurred partially because of more NO x leaching into the shallow groundwater due to the wetter summer and partially because of faster nitrification rate due to the higher temperature in summer. Large extent and high kriging estimated total phosphorus concentrations were found in the residential areas. Overall, the groundwater Na and Mg concentration distributions were relatively more even in summer than in spring. Higher kriging estimated groundwater As concentrations were found around the agricultural areas, which exceeded the EPA's drinking water standard limit. Very small variations in groundwater dissolved organic carbon concentrations were observed between spring and summer. This study demonstrated that the concentrations of groundwater quality constituents varied from location to location, and impacts of land uses on groundwater quality variation were profound.

On modeling the potential impacts of CO2 sequestration on shallow groundwater: Transport of organics and co-injected H2S by supercritical CO2 to shallow aquifers

Proper site selection for CO2 geologic storage requires assessing the impact of potential leakage of CO2 from deep subsurface reservoirs to overlying drinking water aquifers. Although recent studies have largely focused on the mobilization of trace elements in response to the intrusion of CO2 into such aquifers, in this paper we investigate two other leakage issues and potential effects on groundwater quality: the transport of organic compounds by supercritical CO2 from deep storage reservoirs and the upward migration of CO2 with co-injected H2S. Numerical simulations show that organic compounds that may be present at depth, such as benzene, could be mobilized by supercritical CO2 and migrate with the leaking CO2. Modeling results also show that upon the transport of CO2+H2S mixtures through a hypothetical leakage pathway, H2S arrival in the shallower aquifer is delayed in comparison with that of CO2 due to the preferential dissolution of H2S into the aqueous phase. The potentially adverse impacts of leakage on shallow groundwater quality may be exacerbated for cases of leaking CO2+H2S, compared to intrusion of pure CO2, possibly leading to the mobilization of thiophilic elements such as arsenic. Geochemical reactions included in the simulations involve adsorption/desorption, reductive dissolution of goethite, precipitation of pyrite, siderite, and arsenic sulfide phases. The models presented are generic in nature, exploring important processes regarding organic compounds and co-injected H2S, and calling attention to the need for more site-specific studies taking into account the variability and uncertainty of key hydrogeologic and geochemical parameters.

Water Quality Assessment and Source Apportionment of Pollution in Shallow Groundwater System of Jiaozuo

Eight major pollution indicators are selected，which are nitrate, chloride, sulfate, hardness and other indicators through comprehensive monitoring and analysis of shallow groundwater in Jiaozuo area. Fuzzy comprehensive evaluation method is used to determine the water quality level of shallow groundwater. Multiple statistical analysis method is used to take advantage of qualitative and quantitative analysis of pollution sources to identify the main sources of pollution. The results indicate that the shallow groundwater quality is poor and the contaminated area is up to 81.82% in research area. There are three kinds of pollution characteristics of the sources which are the chemical industrial source, mechanical processing source and agricultural source. Their contribution rates to the shallow groundwater pollution of the whole area are 53.81%, 30.34% and 15.85% respectively.

Geochemical Study on CO2-rich Waters of Daepyeong Area, Korea: Monitoring Implication for CO2 Geological Storage

Geochemical monitoring was performed on dilute CO2-rich water as a natural analogue study of CO2 geologic storage. Field measurement and sampling for dissolved ions analyses and isotope analysis were carried out from July of 2009 to November of 2010. Spring and groundwater samples were classified into diluted CO2-rich water (average pH=4.6, EC=151 S/cm), concentrated CO2-rich water (average pH=6.1, EC=1,301), and ordinary groundwater (average pH=6.6, EC=201). pH, EC and dissolved major ions were not changed noticeably during monitoring period which indicates that reservoir of CO2-rich water was not affected by changes of surface condition and recharged groundwater. pH and EC of diluted CO2-rich water from this study area is lowest value among the CO2-rich waters from South Korea. On the other hand, concentrated CO2-rich water was also observed in 5 km north of diluted CO2 - rich water of Daepyeong area. Carbon isotope ratio (δ13 C) of concentrated CO2-rich water is -7.4% and average δ13 C of diluted CO2 rich water is -7.2% which indicates that the CO2 source of concentrated and diluted CO2-rich water could be closely related. The result of simple mixing model revealed that low pH and high TDIC (Total Dissolved Inorganic Carbon) concentration of diluted CO2-rich water was not explained by simple mixing between groundwater and concentrated CO2-rich water. Therefore, inflow of excess CO2 and/or secondary accumulated CO2 should be applied CO2-rich water system in Daepyeong area and reacted with host rock. A batch kinetic model was applied for simulating the ion concentration, pH and TDIC of diluted CO2-rich water after reacting with groundwater, rock and high CO2 condition (50.2 mmol/L). As a result of batch kinetic model, Na+ and K+ concentration of DPw-4 sample was reached in about 20 years. Conclusively, low EC, dissolved ions and high TDIC contents of dilute CO2-rich water indicate that water-rock interaction has been took place in short period of time after input of CO2. The result of this study implies that shallow groundwater quality except pH could not change significantly in the early stage of leakage of CO2. The water-rock reaction rate might not be fast enough in surface environment.

Assessment of the Impact of Open Waste Dumpsites on Groundwater Quality: A Case Study of the Onibu-Eja Dumpsite, Southwestern Nigeria

This research study assessed the impact of an open dumpsite on the quality of surface and shallow groundwater within its vicinity. Twenty water samples were collected and analyzed for physicochemical parameters, major ions, and trace metals.All major ions revealed concentrations within the acceptable limits of both standards, except chloride and sodium in some of the wells, probably due to addition of a disinfectant (“water guard”) and weathering of feldspars that characterize the basement rocks. For most of the trace metals, the concentrations were below detectable limits, except for zinc, iron, and manganese. However, iron and zinc concentrations fall well within the acceptable limit of both WHO and NSDWQ standards, while manganese concentrations were above the limit in most of the surface and shallow groundwaters downslope of the dumpsite. This could be attributed to leachates from the waste.