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vadose zone

Mriganka De, Gurpal S Toor
Septic systems can be a major source of nitrogen (N) in shallow groundwater. We designed an in situ engineered drainfield with aerobic-anaerobic (sand-woodchips) and anaerobic (elemental sulfur-oyster shell) media to remove N in the vadose zone and reduce N transport to groundwater. Effluent was dispersed on top of the engineered drainfield (3.72 m infiltrative surface) and then infiltrated through the aerobic-anaerobic and anaerobic media before reaching natural soil. Water samples were collected over 64 sampling events (May 2012-December 2013) from three parts of the drainfield: (i) a suction cup lysimeter installed at the sand-woodchips interface, (ii) a pipe after effluent passed through the aerobic-anaerobic media, and (iii) a tank containing anaerobic media...
November 2016: Journal of Environmental Quality
Lior Avishai, Hagar Siebner, Ofer Dahan, Zeev Ronen
In this study, we examined the ability of top soil to degrade perchlorate from infiltrating polluted groundwater under unsaturated conditions. Column experiments designed to simulate typical remediation operation of daily wetting and draining cycles of contaminated water amended with an electron donor. Covering the infiltration area with bentonite ensured anaerobic conditions. The soil remained unsaturated, and redox potential dropped to less than -200mV. Perchlorate was reduced continuously from ∼1150mg/L at the inlet to ∼300mg/L at the outlet in daily cycles...
November 3, 2016: Journal of Hazardous Materials
Xueyuan Gu, Jinyu Xie, Xiaorong Wang, Les J Evans
Due to its mobility and toxicity, chromate [Cr(VI)] partitioning in soils, especially in the vadose zone, is an important environmental concern. The aim of this study was to develop a mechanism-based multi-surface complexation model using published parameters to predict the soil/water partitioning of Cr(VI) in 12 soils (previously depleted of organic matter) from China. The retention of Cr(VI) in soils was attributed to two reactive oxide surfaces: goethite and hydrous ferric oxide (HFO); however, modeling results showed that the best prediction was obtained with goethite alone, whereas the addition of HFO resulted in an overestimation of adsorption in some soils...
October 17, 2016: Journal of Hazardous Materials
Yu Yang, Yong-Hai Jiang, Xin-Ying Lian, Bei-Dou Xi, Zhi-Fei Ma, Xiang-Jian Xu, Da An
Hazardous waste landfill sites are a significant source of groundwater pollution. To ensure that these landfills with a significantly high risk of groundwater contamination are properly managed, a risk-based ranking method related to groundwater contamination is needed. In this research, a risk-based prioritization method for the classification of groundwater pollution from hazardous waste landfills was established. The method encompasses five phases, including risk pre-screening, indicator selection, characterization, classification and, lastly, validation...
September 24, 2016: Environmental Management
D Pedretti, A Molinari, C Fallico, S Guzzi
A series of experimental tracer tests were performed to explore the implications of the change in the pressure status of a heterogeneous bimodal aquifer for scale-dependent dispersion and mass-transfer processes. The sandbox was filled with sands and gravel channels and patches to form an alluvial-like bimodal aquifer. We performed multiple injections of a conservative tracer from 26 different locations of the sandbox and interpreted the resulting depth-integrated breakthrough curves (BTCs) at the central pumping well to obtain a scale-dependent distribution of local and field-integrated apparent longitudinal dispersivity (respectively, αL(loc) and αL(app))...
September 9, 2016: Journal of Contaminant Hydrology
Liangliang Wei, Kun Wang, Daniel R Noguera, Junqiu Jiang, Ben Oyserman, Ningbo Zhao, Qingliang Zhao, Fuyi Cui
Soil aquifer treatment (SAT) systems rely on extensive physical and biogeochemical processes in the vadose zone and aquifer for water quality improvement. In this study, the distribution, quantitative changes, as well as the speciation characteristics of heavy metals in different depth of soils of a two-year operated lab-scale SAT was explored. A majority of the heavy metals in the recharged secondary effluent were efficiently trapped by the steady-state operated SAT (removal efficiency ranged from 74.7% to 98...
December 2016: Chemosphere
Jong Yol Park, Marianne Ruidisch, Bernd Huwe
Previous studies have documented the occurrence of veterinary sulfonamide antibiotics in groundwater and rivers located far from pollution sources, although their transport and fate is relatively unknown. In mountainous agricultural fields, the transport behaviour can be influenced by climate, slope and physico-chemical properties of the sulfonamides. The objective of this research is to describe the transport behaviour of three sulfonamide antibiotics (sulfamethoxazole, sulfadimethoxine and sulfamethazine) in sloped agricultural fields located in the Haean catchment, South Korea...
August 31, 2016: Environmental Science and Pollution Research International
Tony Carr, Haishun Yang, Chittaranjan Ray
Water Productivity (WP) of a crop defines the relationship between the economic or physical yield of the crop and its water use. With this concept it is possible to identify disproportionate water use or water-limited yield gaps and thereby support improvements in agricultural water management. However, too often important qualitative and quantitative environmental factors are not part of a WP analysis and therefore neglect the aspect of maintaining a sustainable agricultural system. In this study, we examine both the physical and economic WP in perspective with temporally changing environmental conditions...
2016: PloS One
A P Blaschke, J Derx, M Zessner, R Kirnbauer, G Kavka, H Strelec, A H Farnleitner, L Pang
Contamination of groundwater by pathogenic viruses from small biological wastewater treatment system discharges in remote areas is a major concern. To protect drinking water wells against virus contamination, safe setback distances are required between wastewater disposal fields and water supply wells. In this study, setback distances are calculated for alluvial sand and gravel aquifers for different vadose zone and aquifer thicknesses and horizontal groundwater gradients. This study applies to individual households and small settlements (1-20 persons) in decentralized locations without access to receiving surface waters but with the legal obligation of biological wastewater treatment...
December 15, 2016: Science of the Total Environment
Yuan-zhu Zhang, Qiu-fang He, Yong-jun Jiang, Yong Li
In a karst groundwater system, it develops complex multiple flows because of its special geological structure and unique physical patterns of aquifers. In order to investigate the characteristics and transport patterns of ammonia, nitrite and nitrate in epikarst water and subterranean stream, the water samples were collected monthly in a fast-urbanizing karst region. The results showed distinctive characteristics of three forms of inorganic nitrogen. The concentration of inorganic nitrogen was stable in the epikarst water while it was fluctuant in the subterranean stream...
April 15, 2016: Huan Jing Ke Xue= Huanjing Kexue
Zohre Kurt, E Erin Mack, Jim C Spain
When anoxic polluted groundwater encounters the overlying vadose zone an oxic/anoxic interface is created, often near the capillary fringe. Biodegradation of volatile contaminants in the capillary fringe can prevent vapor migration. In contrast, the biodegradation of nonvolatile contaminants in the vadose zone has received comparatively little attention. Nonvolatile compounds do not cause vapor intrusion, but they still move with the groundwater and are major contaminants. Aniline (AN) and diphenylamine (DPA) are examples of toxic nonvolatile contaminants found often at dye and munitions manufacturing sites...
September 20, 2016: Environmental Science & Technology
Mohammad Ali Baghapour, Amir Fadaei Nobandegani, Nasser Talebbeydokhti, Somayeh Bagherzadeh, Ata Allah Nadiri, Maryam Gharekhani, Nima Chitsazan
BACKGROUND: Extensive human activities and unplanned land uses have put groundwater resources of Shiraz plain at a high risk of nitrate pollution, causing several environmental and human health issues. To address these issues, water resources managers utilize groundwater vulnerability assessment and determination of protection. This study aimed to prepare the vulnerability maps of Shiraz aquifer by using Composite DRASTIC index, Nitrate Vulnerability index, and artificial neural network and also to compare their efficiency...
2016: Journal of Environmental Health Science & Engineering
Elia Scudiero, Scott M Lesch, Dennis L Corwin
Soil spatial variability has a profound influence on most agronomic and environmental processes at field and landscape scales, including site-specific management, vadose zone hydrology and transport, and soil quality. Mobile sensors are a practical means of mapping spatial variability because their measurements serve as a proxy for many soil properties, provided a sensor-soil calibration is conducted. A viable means of calibrating sensor measurements over soil properties is through linear regression modeling of sensor and target property data...
July 2016: Journal of Environmental Quality
Oliver Kuras, Paul B Wilkinson, Philip I Meldrum, Lucy S Oxby, Sebastian Uhlemann, Jonathan E Chambers, Andrew Binley, James Graham, Nicholas T Smith, Nick Atherton
A full-scale field experiment applying 4D (3D time-lapse) cross-borehole Electrical Resistivity Tomography (ERT) to the monitoring of simulated subsurface leakage was undertaken at a legacy nuclear waste silo at the Sellafield Site, UK. The experiment constituted the first application of geoelectrical monitoring in support of decommissioning work at a UK nuclear licensed site. Images of resistivity changes occurring since a baseline date prior to the simulated leaks revealed likely preferential pathways of silo liquor simulant flow in the vadose zone and upper groundwater system...
October 1, 2016: Science of the Total Environment
R Hall, L Murdoch, R Falta, B Looney, B Riha
Application of remediation methods in contaminated vadose zones has been hindered by an inability to effectively distribute liquid- or solid-phase amendments. Injection as aerosols in a carrier gas could be a viable method for achieving useful distributions of amendments in unsaturated materials. The objectives of this work were to characterize radial transport of aerosols in unsaturated porous media, and to develop capabilities for predicting results of aerosol injection scenarios at the field-scale. Transport processes were investigated by conducting lab-scale injection experiments with radial flow geometry, and predictive capabilities were obtained by developing and validating a numerical model for simulating coupled aerosol transport, deposition, and multi-phase flow in porous media...
July 2016: Journal of Contaminant Hydrology
William H Schlesinger
Recent field studies have reported anomalous CO2 uptake using eddy-covariance techniques in arid and semi-arid ecosystems. The rates of CO2 uptake are incompatible with changes in situ of organic carbon pools. Here I examine several potential mechanisms of abiotic CO2 uptake in arid and semi-arid soils: atmospheric pressure-pumping, carbonate dissolution, and percolation of soil water through the vadose zone. Each mechanism is deemed inadequate to explain the observations of the eddy-covariance systems, which must now be questioned for their accuracy...
May 2, 2016: Global Change Biology
Pauline Sidoli, Laurent Lassabatere, Rafael Angulo-Jaramillo, Nicole Baran
The transport of pesticides to groundwater is assumed to be impacted by flow processes and geochemical interactions occurring in the vadose zone. In this study, the transport of S-metolachlor (SMOC) and its two metabolites ESA-metolachlor (MESA) and OXA-metolachlor (MOXA) in vadose zone materials of a glaciofluvial aquifer is studied at laboratory scale. Column experiments are used to study the leaching of a conservative tracer (bromide) and SMOC, MESA and MOXA under unsaturated conditions in two lithofacies, a bimodal gravel (Gcm,b) and a sand (S-x)...
July 2016: Journal of Contaminant Hydrology
Junyu Zhou, Baojing Gu, William H Schlesinger, Xiaotang Ju
Soil nitrate is important for crop growth, but it can also leach to groundwater causing nitrate contamination, a threat to human health. Here, we report a significant accumulation of soil nitrate in Chinese semi-humid croplands based upon more than 7000 samples from 141 sites collected from 1994 to 2015. In the 0-4 meters depth of soil, total nitrate accumulation reaches 453 ± 39, 749 ± 75, 1191 ± 89, 1269 ± 114, 2155 ± 330 kg N ha(-1) on average in wheat, maize, open-field vegetables (OFV), solar plastic-roofed greenhouse vegetables (GHV) and orchard fields, respectively...
2016: Scientific Reports
M Oostrom, M J Truex, G V Last, C E Strickland, G D Tartakovsky
For sites with a contaminant source located in the vadose zone, the nature and extent of groundwater contaminant plumes are a function of the contaminant flux from the vadose zone to groundwater. Especially for thick vadose zones, transport may be relatively slow making it difficult to directly measure contaminant flux. An integrated assessment approach, supported by site characterization and monitoring data, is presented to explain current vadose zone contaminant distributions and to estimate future contaminant flux to groundwater in support of remediation decisions...
June 2016: Journal of Contaminant Hydrology
Yinon Yecheskel, Ishai Dror, Brian Berkowitz
The vadose zone is a critical region controlling fate and transport of contaminants in soils and, ultimately, groundwater. It is therefore important to understand the behavior of engineered nanoparticles (ENPs) in this zone, as a potential group of emerging contaminants. Soil is a significant sink for ENPs; however, only a few studies have considered the fate and transport of ENPs in partially saturated systems, representative of the vadose zone. Here, transport behavior of three commonly used ENPs--gold (Au-NPs), silver (Ag-NPs) and zinc oxide (ZnO-NPs)--is investigated in partially saturated sand columns...
July 5, 2016: Journal of Hazardous Materials
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