scholarly journals How Does the Periodic Groundwater Table Fluctuation Impact on Chlorinated Vapor Intrusion?

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Honghong Zhang ◽  
Yu Ye ◽  
Xin Yang
Keyword(s):  
Vadose Zone ◽  
Dynamic Equilibrium ◽  
Groundwater Table ◽  
Sensitivity Analyses ◽  
Vapor Intrusion ◽  
Contaminant Source ◽  
High Soil Moisture ◽  
Order Of Magnitude ◽  
Groundwater Table Fluctuation ◽  
Table Condition

Periodic groundwater table fluctuations are found frequently in natural aquifers due to sea tides or seasonal recharge. However, their impact on the transport of volatile organic compounds in the vadose zone released from a groundwater contaminant source (i.e., vapor intrusion) has not been well known. A 2D numerical model was developed to explore vapor intrusion processes in the sandy vadose zone, subject to a fluctuating groundwater table with a range of fluctuation amplitudes and periods. A carcinogenic compound, Trichloroethylene (TCE), was chosen as the groundwater contaminant of interest in the current study and assumed to transport into the dwelling through a crack at the corner of the basement. Results showed that the resistant effect caused by high soil moisture contents in the thin capillary fringe is weakened by periodic groundwater table fluctuations, resulting in a higher concentration of gaseous TCE at the building foundation crack, in comparison with that under a static groundwater table. The increase of the gaseous TCE concentration was induced by the enhancement of diffusion and advection due to groundwater table fluctuations. Sensitivity analyses indicated that a higher amplitude and frequency of fluctuations lead to a higher TCE concentration at the crack under the dynamic equilibrium condition. Specifically, compared with the static groundwater table condition, the TCE concentration at the crack increased by one order of magnitude under the condition of groundwater table fluctuations with an amplitude of 0.2 m and a period of one day. The results obtained could provide insights into the importance of the amplitude and frequency of groundwater table fluctuations on vapor intrusion.

scholarly journals Stormwater harvesting in ephemeral streams: how to bypass clogging and unsaturated layers

2021 ◽  
Author(s):  
José D. Henao Casas ◽  
Fritz Kalwa ◽  
Marc Walther ◽  
Randolf Rausch
Keyword(s):  
Vadose Zone ◽  
Numerical Models ◽  
Water Storage ◽  
Sensitivity Analyses ◽  
Ephemeral Streams ◽  
Infiltration Rates ◽  
Stormwater Harvesting ◽  
Harvesting Systems ◽  
Study Case ◽  
Recharge Rates

AbstractTo cope with water scarcity in drylands, stormwater is often collected in surface basins and subsequently stored in shallow aquifers via infiltration. These stormwater harvesting systems are often accompanied by high evaporation rates and hygiene problems. This is commonly a consequence of low infiltration rates, which are caused by clogging layers that form on top of the soil profile and the presence of a thick vadose zone. The present study aims to develop a conceptual solution to increase groundwater recharge rates in stormwater harvesting systems. The efficiency of vadose-zone wells and infiltration trenches is tested using analytical equations, numerical models, and sensitivity analyses. Dams built in the channel of ephemeral streams (wadis) are selected as a study case to construct the numerical simulations. The modelling demonstrated that vadose-zone wells and infiltration trenches contribute to effective bypassing of the clogging layer. By implementing these solutions, recharge begins 2250–8100% faster than via infiltration from the bed surface of the wadi reservoir. The sensitivity analysis showed that the recharge rates are especially responsive to well length and trench depth. In terms of recharge quantity, the well had the best performance; it can infiltrate up to 1642% more water than the reservoir, and between 336 and 825% more than the trench. Moreover, the well can yield the highest cumulative recharge per dollar and high recharge rates when there are limitations to the available area. The methods investigated here significantly increased recharge rates, providing practical solutions to enhance aquifer water storage in drylands.

scholarly journals Vulnerability assessment and potential contamination of unconfined aquifers

2018 ◽  
Vol 19 (4) ◽  
pp. 1008-1016 ◽  
Author(s):  
J. Caprario ◽  
A. S. Rech ◽  
A. R. Finotti
Keyword(s):  
Vadose Zone ◽  
Vulnerability Index ◽  
The Other ◽  
Sensitivity Analyses ◽  
Drastic Model ◽  
Groundwater Availability ◽  
Unconfined Aquifers ◽  
Direct Infiltration ◽  
The Subject ◽  
The Impact

Abstract The decline in groundwater availability and quality has become a worldwide issue and has been the subject of several studies in recent decades. In this sense, the goal of this study is to assess the vulnerability of the Campeche Aquifer (Florianopolis, Brazil), identifying potential areas of possible contamination by the direct infiltration of runoff in drainage compensatory techniques. To achieve this goal, the following methodological steps were used: (1) data collection and preparation, (2) application of the DRASTIC model, (3) sensitivity analysis and (4) analysis of potential contamination by compensatory techniques. The results show that approximately 33% of the aquifer area presented moderate vulnerability to contamination. However, 29% of the remaining areas had high and extremely high vulnerability. Analysing the potential of contamination with drainage compensatory structures we verified that approximately 95% of them are located in areas of vulnerability classified as moderate and high. The other 5% were identified in areas with extremely high vulnerability. Sensitivity analyses indicated that the removal of topography, soil type and the impact of the vadose zone caused a large variation in vulnerability index. It is evident that there is a high potential of contamination of groundwater by direct infiltration of drainage compensatory structures.

scholarly journals Vadose zone infiltration and its implication for groundwater contamination risk assessment in Siloam village, Limpopo province, South Africa

2019 ◽  
Vol 11 (2) ◽  
Author(s):  
Ivo Arrey ◽  
John O. Odiyo ◽  
Rachel Makungo ◽  
Milton Kataka
Keyword(s):  
South Africa ◽  
Risk Assessment ◽  
Vadose Zone ◽  
Root Zone ◽  
Risk Identification ◽  
Groundwater Table ◽  
Limpopo Province ◽  
Zone Model ◽  
Organic Additives ◽  
Moisture Fluxes

Risk assessment methods and approaches are useful for environmental planning and decision-making when dealing with risk identification and reduction in a changing global context. This is particularly true for arid and semi-arid regions, such as Siloam village, Limpopo province, South Africa, where it is a common practice to apply fertilisers to the soil during planting season for increasing crop yield. Estimates of vadose zone soil moisture fluxes were used to determine the likelihood of applied agricultural fertilisers to reach the groundwater table. This study combines field observations in the study area and a one-dimensional numerical model to explore the moisture fluxes and their implications for contaminant transport in the vadose zone. Model simulations revealed a lag time of 117 days at topsoil and 913 days beyond the root zone for deep percolation of soluble non-reactive inorganic and organic additives to reach the groundwater table. Preliminary results of this study suggest that the vadose zone is permeable and the groundwater is vulnerable to contamination within the evaluated time scale. Given that disaster risks are inevitable, reasonable methods for control and mitigation of agricultural impacts at this site are highly recommended.

Lab-based investigation of enhanced BTEX attenuation driven by groundwater table fluctuation

Chemosphere ◽  
2017 ◽  
Vol 169 ◽  
pp. 678-684 ◽  
Author(s):  
Y.S. Yang ◽  
Panpan Li ◽  
Xi Zhang ◽  
Mingjie Li ◽  
Ying Lu ◽  
...  
Keyword(s):  
Groundwater Table ◽  
Groundwater Table Fluctuation
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