Contaminant Intrusion Research Articles

A New Model Approach for Vulnerability to Assess Seawater Intrusion Risk for Monastir Aquifer System, Tunisia

This paper presents the theory and application of a new vulnerability method (RIHM). The method is applied on Monastir shallow aquifer system, Tunisia. The results have been concluded from other established vulnerability assessment methods DRASTIC, SINTACS and GALDIT. As known, DRASTIC and SINTACS methods are not designed for seawater intrusion contamination but are useful to build the new model approach to assess groundwater vulnerability to seawater intrusion. RIHM parameters have been concluded after performed sensitivity analysis of the most important parameters of each method. Its vulnerability data are rated into four classes and assigned equal values ranging from less than 109 to 176.

A pilot study characterizing tetrachloroethylene exposure with exhaled breath in an impacted community

Martinsville, Indiana overlays four groundwater contamination plumes, including a U.S. Environmental Protection Agency (EPA)-designated Superfund site. The primary contaminants are tetrachloroethylene (PCE), trichloroethylene (TCE), and other volatile organic compounds (VOCs). Martinsville represents many similar communities facing the challenge of groundwater and soil contamination and vapor intrusion, where residents are often frustrated by the lack of help in understanding and addressing the problem. The objective of this study was to evaluate PCE in exhaled breath to identify and quantify exposure to PCE and to explore the extent and level of PCE exposure among community residents. We measured chlorinated VOCs in exhaled breath samples from 38 healthy individuals who lived either in a contamination area or outside any plume area. We also measured VOCs in indoor air and tap water samples collected from 10 homes. PCE was detected in all exhaled breath samples (mean: 6.6 μg/m3; range: 1.9–44 μg/m3) and tap water samples (mean: 0.74 μg/L; range: 0.39–0.92 μg/L). PCE was detected in six of nine (66%) homes with air concentrations ranging from 1.6 to 70 μg/m3, exceeding the EPA action level of 42 μg/m3. We did not detect TCE or any other chlorinated VOCs in these samples. PCE exposure occurred among individuals living on the EPA Superfund site, as well as among those living on other plume sites and those living outside any known plumes. Preventive measures should focus on identifying highly exposed groups and reducing their exposures, followed by addressing moderately elevated exposures in the community. Our results demonstrated that PCE in exhaled breath can be used as an effective tool in community engaged environmental health research to evaluate the extent and level of community exposure, increase awareness, and promote residents’ participation in research and site cleanup decision-making.

Reservoir operation under accidental MTBE pollution: A graph-based conflict resolution framework considering spatial-temporal-quantitative uncertainties

Given the hazardous effects of sudden dam reservoir contamination — as might occur upon the intrusion of the fuel additive methyl tert-butyl ether (MTBE) — the contaminant’s effect on the quality of allocated waters requires careful study. Employed to determine optimal reservoir operational rules in the case of sudden MTBE pollution, a risk-based simulation–optimization model was developed to simultaneously minimize unsatisfied water demand, the risk of violations of water quality standards, and the reservoir recovery time. Risks were assessed by considering various often-neglected pollution scenarios as a combination of location, quantity, and the season of pollution intrusion. The appropriateness of operational rules proved to depend upon thermal conditions and MTBE intrusion properties, confirming the necessity of considering location-quantity-season uncertainties. Social and regional conditions also occupied a dominant role in determining the level of satisfaction achieved under different water allocation strategies. Accordingly, by considering environmental conditions and local rules, a graph model for conflict resolution was established and used to reach a set of compromise operational rules. The developed framework could serve as a guide for water utilities to determine efficient reservoir operational rules after a sudden contaminant intrusion.

Pressure and Water Quality Integrated Sensor Placement Considering Leakage and Contamination Intrusion within Water Distribution Systems

Integrated sensors are installed in water distribution systems for the real-time detection of pipe leakage and contamination. We design a novel strategy for sensor placement to monitor leakages and...

Review of drivers and threats to coastal groundwater quality in China

With rapid socio-economic development, China's coastal areas are among the fastest growing and most economically dynamic regions in the world. Under the influence of climate change and human activities, protecting the quality of coastal groundwater has emerged as one of the key environmental and resource management issues for these areas. This paper reviews (for the first time) groundwater quality data for the coastal basins of China, where over 600 million people live, focussing on key inorganic indicators/pollutants; groundwater salinity, nitrate, fluoride, and arsenic. These pollutants present major water quality issues and are also valuable as indicators of wider processes and influences impacting coastal groundwater quality – e.g. saltwater intrusion, agricultural pollution and release of geo-genic contaminants. We discuss the major drivers causing water quality problems in different regions and assess future trajectories and challenges for controlling changes in coastal groundwater quality in China. Multiple processes, including modern and palaeo seawater/brine migration, groundwater pumping for agricultural irrigation, pollution from agrochemical application, rapid development of aquaculture, urban growth, and water transfer projects, may all be responsible (to different degrees) for changes observed in coastal groundwater quality, and associated long-term health and ecological effects. We discuss implications for sustainable coastal aquifer management in China, arguing that groundwater monitoring and contamination control measures require urgent improvement. The evolution and treatment of coastal groundwater quality problems in China will serve as an important warning and example for other countries facing similar pressures, due to climate change, coastal development, and intensification of anthropogenic activity in coming decades.

Material distortion in laser-based additive manufacturing of fuel cell component: Three-dimensional numerical analysis

Laser powder bed fusion (LPBF), an important additive manufacturing (AM) technique, has received a great deal of research attention and industrial application. The capability to fabricate complicated shapes and structures enables this technique to be applied for the manufacturing of rapid prototypes and complex parts. In operation, the constant melting and cooling of metal powders in a layer-by-layer fashion leads to large gradients and a rapid evolution of temperature, which may cause considerable residual stress and deformation. Polymer electrolyte membrane (PEM) fuel cells are a major type of fuel cells that operate under low temperature with high efficiency. PEM fuel cell components must be free of major distortion to avoid leakage of the reactant gases, intrusion of contaminants, and a large interfacial resistance. In this study, a three-dimensional (3D) numerical study is conducted to investigate the residual stress and deformation in a fuel cell inlet/outlet fitting directly built on the bipolar plate by LPBF. Both Inconel 718 (IN718) and stainless steel 316 L (SS316L) are used as the building materials. The distortion prifle predictions are compered with literature data. Additionally, the validated tool is employed to investigate several major parameters in LPBF fabrication to assess their impacts on distortion, including laser power, laser speed, and layer thickness. In our case, the laser power and speed have a significant impact on the distortion of the inlet/outlet fitting. SS316L shows a much less distortion (about 40 µm) than that of IN71 (about 90 µm) for the maximum distortion and a nearly 30% smaller average distortion at all measuring locations. The middle height of the fitting is subject to the largest distortion. A strain parameter ε* is discussed to facilitate the analysis of the simulation results.

GPR for earth and environmental applications: Case studies from India

Ground Penetrating Radar (GPR) is widely applied for rapid and precise mapping of the near surface structures. We performed GPR survey using Terra Sirch-3000 single channel control GPR meter with 2D data collection for civil engineering, environmental, archeological, geological features, aquifer contamination and seawater intrusion studies in Indian context. The 200 MHz and 400 MHz frequency antennae with adjusted dielectric constant, scans per unit, range, transmit rate, gain points, and filters were used for attaining the targets depth up to 3–8 m. The collection of GPR data was on Geologic Scan, Utility Scan, Structure Scan, and Terra SIRch modes with resolution of 16 bits, and was processed in RADAN (version 5.0) using various options to get clear anomaly of the targets. Based on the targets, the scanned images were verified with excavations, electrical resistivity tomography, and soil and water chemistry which were complementing with the GPR anomalies. Results demonstrated in this article are, 1) identification of caving in trenchless MS pipe of 1700 mm diameter with feasibility for trenchless technology, 2) discovery of ancient temple, 3) deciphering a subsurface intrusive body (i.e. dolerite dyke), 4), detection of clandestine pipes, 5) demarcating fresh groundwater zones within industrial clusters, and 6) identification of seawater intrusion in coastal area. The study establishes that the GPR works as rapid tool in unraveling shallow subsurface complexities with high-resolution images and offers a geophysical tool for wide range of earth and environmental management.

Influence of the subsurface physical barrier on nitrate contamination and seawater intrusion in an unconfined aquifer

Coastal areas are facing not only environmental problems associated with seawater intrusion (SWI) but also health and ecological problems caused by excessive nitrate (NO3−) contamination. The installation of a subsurface physical barrier (SPB) is one of the common methods employed to reduce or prevent SWI, but there are few studies on the impact of SPBs on NP in groundwater. Through laboratory experiments and numerical simulations, the effects of the hydraulic gradient (HG), the nitrate concentration of the set groundwater nitrate pollution source, the relative height of the SPB (HP’) and the relative distance between the SPB and the saltwater boundary on the NP of groundwater in the presence of SWI, subsurface dams and cut-off walls were studied. Evaluation indicators were established to evaluate the degree and shape of the SWI and NP. To better describe the relationship between the velocity distribution and changes in the velocity distribution area and the degree of NP and SWI, the velocity distribution in the presence of SWI and a SPB was summarized separately. The results showed that when there was SPB, low-velocity zones were formed on both sides of the SPB, which not only slowed the migration of NO3− but also changed the shape of the NO3−-contaminated area. The closer to the SPB area the pollutants were, the more obvious the obstruction effect. The obstruction effect of adding the cut-off wall on NP was more obvious than that of adding the subsurface dam wall. The selected HG and Hp’ were important factors affecting NP and SWI. The higher HG was, the more serious the NP, the lower the HG, and the stronger the degree of SWI. Adding SPBs reduces the impact of HGs on NP and SWI. Therefore, the design of SPBs in coastal areas should focus on aspects related to these two factors.

Impacts of irrigation and nitrate fertilization scenarios on groundwater resources quantity and quality of the Almyros Basin, Greece

Abstract Irrigation and nitrate fertilization scenarios were combined and simulated for crop water irrigation demands and nitrogen applications based on experiments on crop cultivation practices. Two irrigation practices (deficit irrigation and rainfed conditions) were applied to the main crop types of the Almyros Basin, a coastal basin located in Thessaly, Greece. The Almyros groundwater system suffers from progressive water balance deficit, nitrate contamination and seawater intrusion due to groundwater abstractions for agricultural irrigation to cover crop water demands in the dry season. The impacts of the irrigation and nitrate fertilization scenarios on groundwater resources quantity and quality were simulated using an Integrated Modelling System consisting of models of surface hydrology (UTHBAL), groundwater hydrology (MODFLOW), crop growth/nitrate leaching (REPIC), contaminant transport (MT3DMS), and seawater intrusion (SEAWAT), for the historical period of 1991–2018. The results of the scenarios were evaluated with the indicators of Crop Water Productivity (CWP) for crop yields and irrigation water, Partial Factor Productivity (PFP) for Nitrogen Use Efficiency, and Economic Water Productivity (EWP) for the gross profits of the irrigation water.

A multi-tracer approach for understanding the functioning of heterogeneous phreatic coastal aquifers in humid tropical zones

ABSTRACT In many areas around the world, phreatic coastal aquifers are vulnerable to contamination and saltwater intrusion. This study aims to explore the hydrodynamic functioning of the coastal phreatic aquifer of the Urabá region, Colombia, based on the identification of hydrogeochemical processes and groundwater residence and transit times. Hydrodynamic data showed a fast response of the piezometric levels to precipitation with a maximum time lag of 48 h. Mean annual recharge was estimated at 19% with respect to precipitation. Another recharge mode is linked to infiltration from surface water, according to the hydrodynamic results. The main geochemical process identified is hydrolysis due to dissolved carbon dioxide, inducing silicate weathering and resulting in predominant HCO3-Ca-Mg facies. Monitoring of δ18O and δ2H compositions combined with 3H, 14C, chlorofluorocarbons (CFCs) and SF6 contents showed a fast recharge in the aquifer. Groundwater dating indicates recent waters mixed with older (>40 years) waters.

An Analytical Model for the Decontamination of Water Distribution Systems Using Slug‐Feed Method of Disinfection

AbstractThe increasing risk of intentional, negligent, or accidental intrusion of biological, chemical, or radioactive contaminants in water distribution systems is becoming a major concern that has significant and adverse impacts on public health. As such, it is important to have an effective, robust, and flexible plan that can be readily implemented to minimize the impact of these contamination events. However, limited research has been focused on the strategic planning of the decontamination process of the contaminated infrastructure. This paper proposes an analytical method for modeling the slug‐feed method of disinfection given the drainage and disinfectant dosage profiles. The efficacy of the proposed method has been demonstrated by using it as the evaluation function in a genetic algorithm optimization of two case studies. Results show the proposed method exhibits higher robustness compared to the procedures defined in the current standard and literature. The main contributions of this study are to (1) provide a robust and accurate model to describe the slug‐feed method of disinfection, (2) offer additional resource utilization flexibility for water authorities, and (3) providing additional levels of district metered areas prioritization.

Attentional processes and contamination-related intrusion distress

Whilst people with high contamination fear may not experience a greater number of contamination-related intrusions than people with low contamination fear, they tend to experience heightened distress in response to such intrusions. The aim of the present study was to test the hypothesis that attentional bias to contamination-relevant information, and the variability of this attentional bias, moderates the degree to which high contamination fearful but not low contamination fearful individuals experience distress in response to contamination-related intrusions. Individuals with high (n = 31) or low (n = 44) contamination fear completed a lab-based session including questionnaires, a dot-probe measure of contamination-related attentional bias and attentional bias variability, and a contamination stressor video. Participants then completed a week-long contamination intrusions diary. There were significant differences in intrusion distress between those with low and high contamination fear in the anticipated direction, and attentional bias significantly moderated this relationship. Regardless of contamination fear level, greater attentional bias variability was associated with greater intrusion distress. These findings suggest that reducing attentional bias variability could potentially help to reduce distress elicited by contamination-related intrusions, while also highlighting the fact that attentional bias towards threat may protect against such distress in low contamination fearful individuals.

An analytical model of vapor intrusion with fluctuated water table

Intrusion of subsurface contaminants in vapor phase from groundwater into overlying buildings through cracks or other pathways poses potential risk to human health. Previous studies indicated that water table fluctuations may have significant impacts on vapor intrusion, resulting in fluctuated concentrations of indoor volatile organic compounds (VOCs). Analytical solutions for vapor intrusion processes are flexible tools in predicting VOC concentrations and assessing health risks of VOC-contaminated sites. However, an analytical solution considering the impacts of fluctuated water table is not available. In this study, an analytical model of the vapor intrusion with fluctuated water table was developed. The VOC transport in unsaturated zones was described by diffusion equation and the varying water table was treated as a moving boundary. The residual VOCs in the unsaturated zone induced by water table fluctuations were also considered and were described by a source term of the vapor diffusion. The analytical solution was tested with its numerical solution. The results indicate that the fluctuated water table affects the dynamics of VOCs mainly in two ways, changing the length of vapor migration path and delivering the residual VOCs into the unsaturated zone. The VOC concentration at the outlet varies inversely with the water table fluctuation owing to the release processes of the residual VOCs dominate. The analytical solution matches well to the laboratory experiment data in an existing study and could be a simple tool for the risk assessment of vapor intrusion when considering the impacts of water table fluctuations.

Long-term analysis of the relationships between indoor and outdoor fine particulate pollution: A case study using research grade sensors

The growing concern of air quality and its associated health-related impacts has led to increased awareness of pollutant exposure. Most human populations spend the majority of their time indoors and the COVID-19 pandemic has likely exacerbated this behavior. While significant amounts of research have focused on outdoor air quality, to date there have been no studies that examined simultaneous long-term trends on indoor and outdoor air quality on a site using research-grade sensors. We measured fine particulate matter (PM2.5) for a year using sensors located on the rooftop, air handling room, and indoor office space in a building and captured the impacts of three types of regularly occurring elevated pollution events: wintertime atmospheric inversions, wildfires, and fireworks. The events had different magnitudes and durations, and infiltration rates varied for each event leading to dissimilar indoor air pollution levels. The building's air handling unit and different environmental conditions (lower indoor humidity and temperature during the winter) combined to reduce indoor pollution from inversion events however, particulate matter from wildfires and fireworks infiltrated at higher rates. Together, this suggests possible intervention strategies, such as ventilation rates and filter upgrades, that could be used to mitigate contaminant intrusion during elevated pollution events. This year-long study illustrates an array of ways that elevated pollution events interact with the protective effects that buildings have against air pollution for its occupants. Furthermore, we show that outdoor air pollution is an important variable to consider when studying indoor air quality as contaminant infiltration is strongly dependent on the specific pollution source.

Robust Placement of Water Quality Sensor for Long-Distance Water Transfer Projects Based on Multi-Objective Optimization and Uncertainty Analysis

It is important to place water quality sensors along open channels in long-distance water transfer projects optimally for rapid source identification and efficient management of sudden water contamination. A new framework which considers multiple objectives, including earliest detection time, lowest missing detection rate and lowest sensor cost, and combines the randomness of injected contaminant type and contaminant incident consisting of contaminant intrusion location, time and mass, was established to obtain optimal placement of water quality sensor with better robustness in this paper. The middle route of the South-to-North Water Diversion Project in China was chosen as a case study, and it was found that both missing detection rate and detection time decrease with sensor cost gradually; furthermore, given the higher detecting precision, the detection accuracy and efficiency would be improved, a smaller number of water quality sensors would be needed, and the ten key placement positions where sensor with different detecting precision placed could be identified. Under the constraints of the allowable maximum missing detection rate, 1.00%, and detection time, 120.00 min, the detecting precision of 0.20 mg/L and 38 sensors placed could be selected as the optimal sensor placement scheme. Finally, with the consideration of contaminant uncertainty, the sensor placement scheme with better robustness could be constructed. The proposed framework would be helpful in solving the problem of water quality sensor placement with high practicality and efficiency in long-distance water transfer projects.

Identifying Contaminant Intrusion in Water Distribution Networks under Water Flow and Sensor Report Time Uncertainties

Contamination events in water distribution networks (WDNs) could have severe health and economic consequences. Contaminants can be deliberately or accidentally introduced into the WDN. Quick identification of the injection location and time is important in devising a mitigation plan to prevent further spread of the contaminant in the network. A method of identifying the possible intrusion point in a given network and reporting data is to use an inverse calculation by backtracking the potential path of the contaminant in the network. However, there is an element of uncertainty in the data used for calculation, particularly in water flow and sensor report time. Given the uncertainties, a method was developed in this study for fast and accurate contaminant source identification. This paper proposes a comparison filter of results by first identifying potential contaminant locations through backtracking, followed by a forward calculation to determine the injection time range, thereby reducing the potential suspects and providing likeliness comparison among the suspects. The effectiveness of the proposed method was examined by applying it to a benchmark WDN. By simulating uncertainties and filtering through the results, several possible contaminant intrusion locations and times were identified.

Validation and Measurement Invariance of the Leuven Obsessional Intrusions Inventory in Two Different Cultures.

Obsessions – recurrent unwanted intrusive thoughts – are one of the two pillars of the Obsessive Compulsive Disorder (OCD). Although OCD has been reported across many different cultures, research on these cultural variations is hampered by the lack of cross-culturally sound instruments to assess intrusive thoughts. The aim of the current study is to investigate the psychometric properties of the recently developed Leuven Obsessional Intrusions Instrument (LOII) in two different cultural contexts. Turkish (N = 663) and Belgian (N = 496) participants were sampled from non-clinical student populations. Results from confirmatory factor analyses yielded a shortened version of the LOII (i.e., LOII-R) with a four-factor solution – aggressive, sexual, and contamination intrusions, and ‘just-right’ doubts – as the best fitting model across both cultures. The model met most criteria for strong measurement invariance, and proved to be both valid and reliable. The results of this study suggest that the LOII-R is a good candidate for cross-cultural studies on obsessional intrusions.

Risk-Based Models for Optimal Sensor Location Problems in Water Networks

AbstractWater distribution networks (WDNs), as vital systems of any city, are vulnerable to the intrusion of contamination, and the security of WDNs is of great importance. A promising approach for...

ENVIRONMENTAL LEAKAGE POLLUTIONS EVALUATIONS IN URBAN WATER DISTRIBUTION NETWORK USING UNACCOUNTED WATER PRINCIPLES (SHOKUHIEH INDUSTRIAL TOWN IN IRAN)

Consideration of non-revenue water in urban water distribution networks is of special importance in planning urban water distribution network and in water consumption. Water loss, especially in the distribution networks, forms a large part of the unaccounted for water (UFW). Considering the serious crisis in water resources, and taking into account the existing limitations of supplying hygienic drinking water, increasing attempts must be made at reducing the volume of water loss. The present study evaluated the environmental effects of pollution leakage from broken pipes into the water distribution network in the Shokuhieh. General principles and concepts of UFW, apparent loss was reviewed. Based on these concepts, probable pipe break points, and the resulting contaminants entering the network were considered. A software model of the water distribution network in the study area was then used to investigate qualitative and quantitative results related to intrusion of contaminants into the water distribution network and diffusion of pollutants into the network. Results of the present study and physicochemical tests performed on water revealed that BOD and COD concentrations increased from 5-10 to 10-20 mg/L and the coliform count rose from zero to 20 MPN as a result of pipe breaks in the distribution network.

Limitations of E. coli Monitoring for Confirmation of Contamination in Distribution Systems due to Intrusion under Low Pressure Conditions in the Presence of Disinfectants

AbstractLow/negative pressure events that increase the risk of contaminant intrusion may take place in distribution systems and may become more common in ageing infrastructure. Guidance on whether ...