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To remediate historically polluted sites before their land-use changes, it is essential to understand the concentration distribution, geochemical fraction, and migratory behavior of As in soil with varied particle sizes for the use of a sieving procedure. This study investigated the amount and percentage of As in soil with different particle sizes (0.25, 0.25–1, and 1–2 mm) as well as its toxicity characteristic in leaching procedure at four previously contaminated sites in the Beijiang River Basin, South China. The results showed that the total As concentration in the collected soils ranged from 70.1 to 402.8 mg/kg, and only a few percent of soil particle samples had As contents below the local risk threshold value of 60 mg/kg. The amorphous hydrous oxide bound, crystalline hydrous oxide bound, and residual fractions (F3–F5) of the geochemical fraction of As in soil of polluted sites accounted for 82.2–95.7% of the total As distribution. However, the concentration of As in non-specifically bound fractions increased with the mass ratio of soil with coarse particle sizes due to the negative correlation of Fe-bearing minerals concentration with the mass ratio of soil with coarse particle size. According to redundancy analysis, soil with coarse particle sizes and non-specifically bound As were mostly responsible for the As concentration in the leachate. These findings confirmed that a sieving process was not suitable for the remediation of soil As at four historically contaminated sites in the Beijiang River Basin due to the high concentration of As in soil and non-negligible environmental risk of labile extractable As in soil with coarse particle size. [ABSTRACT FROM AUTHOR]

Remediation and preparation for development is a crucial aspect of the valorization of post-mining areas. This study is focused on technologies devoted to the cement stabilization of post-industrial waste and petroleum contaminated soils. Two case studies are presented. Case 1 is based on the stabilization works of waste from a closed chemical plant in order to turn it into an engineered landfill. The results form the basis for numerical studies of slope stability. The shorter case 2 is based on the laboratory testing of a soil–cement composite with regard to petroleum contamination and the application of active carbon to neutralize it in the course of deep soil mixing. Both cases, due to the use of slag cement, are not considered to be sustainable (due to a relatively high carbon footprint), but they represent current geotechnical practice and form a reference for a wide range of applications. Both cases show the positive impact of stabilization by means of the addition of a hydraulic binder. The effect of soil improvement is measurable in terms of the stability factor of landfill slopes. The effect of active charcoal addition seems to be a valuable improvement to standard deep soil mixing technology in the case of contaminated soil. The presented results, despite their local importance related to the cases under scrutiny, have an important educational and scientific value for the energy sector, where contaminated sites need to be valorized. [ABSTRACT FROM AUTHOR]

Remediation of heavy metals is a complex, difficult, and expensive exercise and commonly involves relocation of the problem from one place to another (e.g., a contaminated site to a hazardous waste landfill). Alternatively, bioremediation can be used so that metals can be sequestered into the woody portion of the plant, where they are fixed into the organic matter and remain undisturbed for extended periods (e.g., wetland area soils). A species of willow (Salix caroliniana) was investigated to ascertain its potential for use in the bioremediation of mercury. It was found that the plant did bioaccumulate mercury and did so especially in the wood compared to its leaves (8.8 to 1 ratio in the mercury activity; activity of 12,071 to 1164). While there is moderate potential for use in bioremediation, the measured concentration in the wood was quite low (average of 11.91 ppb). The low concentration was caused by the location of the sampled trees in environments that were either pristine or had low soil concentrations of mercury. Furthermore, 90% of the mercury accumulated in the leaves appeared to be adsorbed via atmospheric deposition in southwest Florida where there are minimal sources of anthropogenic mercury, but the region is impacted by Saharan dust, which does contain mercury. [ABSTRACT FROM AUTHOR]

In contaminated sites, remediation measures mostly depend on previous high-resolution site characterization (HRSC) results. In the case of industrial sites, where there is a high pollution risk for groundwater, many hydrogeological models are often achieved using stratigraphy results of geological drilling after the monitoring network design. This approach is only sometimes possible when contaminant back diffusion from small low-permeability lenses and layers occurs within a high-permeability aquifer. This framework needs a significant resolution that can be obtained by coupling preliminary stratigraphic data with specific in situ activities. Results from these additional investigations may help to locate low-permeability layers and, consequently, to identify the most vulnerable areas towards which groundwater management must be deepened. The use of gamma rays in combination with the analysis of the pluviometric and hydrometric data and together with the time series of the concentrations of a given analyte can provide indispensable support for site characterization, the development of numerical groundwater contamination models and remediation procedures when back diffusion occurs. In this study, within an industrial site in the province of Benevento (Italy), based on stratigraphy, a 3D hydrogeological model has been set up and coupled with results of natural gamma radioactivity logs to detect the release of Chromium VI from low-permeability lenses. [ABSTRACT FROM AUTHOR]

Mercury concentration measurements were compiled from 72 sites located throughout seven departments of Colombia using field information gathered from 2016-2021 by Pure Earth, an international non-profit organization, and secondary information from previously conducted studies. These measurements and other data such as type of contaminated resource (water, soil), resource use (fishing, agricultural, residential, and industrial), estimated at-risk population, and permissible contamination limits were entered into Pure Earth's Toxic Site Identification Program (TSIP) database. Using information from the TSIP database, the Blacksmith Index, a contaminated site intervention prioritization index, was calculated for all 72 sites. After applying exclusion criteria to the sites for this study, the results show that approximately 55,095 people are affected by mercury contamination in 44 sites. Of these study sites, the site with the highest Blacksmith Index value and therefore, the highest health risk due to mercury contamination, is La Bocana in the department of Valle del Cauca. [ABSTRACT FROM AUTHOR]

This study focused on the mixing of a solute, assumed to be conservative, introduced to one arm of an afterbay reservoir, between Keswick and Shasta Dams on the Sacramento River near Redding, California. Rhodamine water tracer (WT) dye served as the solute in a field experiment, and was introduced over 4.5 h and monitored for 4 days by sondes moored in the reservoir. The scenario was modeled numerically using the Delft3D flexible mesh (FM) hydrodynamic and mixing model, with measured inflows, outflows, water level, water temperatures, and bathymetry as input. Manning's n and horizontal eddy viscosity served as the (constant) model calibration parameters, and each was adjusted an order of magnitude below the default values to force observed and modeled dye hydrographs to match in arrival time and duration. The low friction factor was concluded to be due to a combination of low flow speeds coupled with energy dissipation inherent to the model. The model and surface drifters equipped with dual-frequency Global Navigation Satellite System equipment revealed velocities in the 1–5 cm/s range in much of the domain during the experiment. Simple analytical expressions were shown to be useful for estimating distance to full cross-sectional mixing, steady-state concentrations, and time to reach them, but the numerical model is required for investigation of the approach to steady state, and at locations where flows intersect. Time to steady-state concentrations was 1.5–13 days for 10 simulations that spanned a wide range of inflow conditions. Model sensitivity tests suggest that wind and heat fluxes were not important during the field study, but simulations of a summer scenario with small inflows of cold water upstream in warm weather should consider water temperature. Both field observations and numerical model results showed inflow to one arm of the reservoir reaching full cross-sectional mixing before plunging below the water surface near the intersection of this arm with the reservoir's main stem. Model results are being used to guide management decisions related to inflows to the reservoir from a relic mining site that is also a USEPA Superfund site. [ABSTRACT FROM AUTHOR]

Contaminated waste sites proliferate across the United States. However, current cleanup incentives fail to induce necessary private sector engagement. Environmental taxation can be a crucial instrument for addressing this issue. This Note begins by exploring why neither the free market, nor regulation is well-suited to manage contamination cleanups on abandoned properties. The Note then proposes a two-phase tax reform for addressing hazardous waste. First, Congress should expand the incentives available to developers to perform the necessary cleanups. Second, an effluent tax should be implemented on large quantity hazardous waste producers to promote the polluter-pays principle and to enhance the efficiency of waste management. This second phase should be introduced in conjunction with the phasing out of detrimental expenditures that distort market forces in favor of polluting behaviors. [ABSTRACT FROM AUTHOR]

Methods to improve the efficiency of bioremediation of hydrocarbon-contaminated sites involves the assessment of microbial consortia in culture. In the present study, the cooperative capabilities of indigenous bacteria, yeast and fungi, as naturally-occurring consortia isolated from chronically contaminated sites in Trinidad, were screened to determine the most efficient associations that resulted in maximum oil clearance. Thirty naturally-occurring consortia involving both known biosurfactant-producing and non-producing isolates were screened. A total of sixteen combinations of yeast with fungi and bacteria with fungi were found to be the most efficient at crude oil deterioration based on >70% a zone of clearance around the original inoculum site on different media. The study revealed a difference in degradation action of strain-specific combinations which confirmed that the development of microbial consortia is both strain- and site-specific. Those consortia composed of biosurfactant-producing members were the most efficient at crude oil removal. [ABSTRACT FROM AUTHOR]

Electric resistivity survey was carried out in three selected dumpsites in Gusau metropolis for groundwater contamination. The dumpsites were investigated by conducting Vertical Electrical Soundings (VES) using Schlumberger array with maximum current electrode separations of 180 m. Five VES were conducted on each dumpsite making a total of fifteen VES along three profiles. The field data obtained from VES were analyzed using WinGlink softwar. The VES results revealed three subsurface layers. The topsoil had resistivity ranging from 1.45 Ωm to 48.2 Ωm while the thicknesses varied from 0.47 m to 3.37m across the profiles. The second layer's resistivities varied from 5.4 Ωm to 144.35 Ωm and their thicknesses' ranges from 1.36 m to 16.93 m. The third geoelectric layer had resistivity from 70.0 Ωm to 6003.0 Ωm. The results indicated that the top soils in all the dumpsites were characterized by very low resistivity depicting possible pollution and contamination. Findings from this study indicated that there may be possible contamination of shallow groundwater system in the nearest future if proper mitigation measures are not taken into consideration at the dumpsites. [ABSTRACT FROM AUTHOR]

Millions of contaminated sites worldwide need to be remediated to protect the environment and human health. Although numerous remediation technologies have been developed, selecting optimal technologies is challenging. Several multiple criteria decision-making methods for screening the optimal remediation technology have been proposed, but they mostly focus on a specific area rather than the whole contaminated site. In recent years, the "contamination source control—process blocking—in situ remediation" technology mix model has gradually gained high appreciation. Nevertheless, the screening of technologies within each chain of this model relies heavily on arbitrary personal experience. To avoid such arbitrariness, a petroleum-contaminated site containing light non-aqueous phase liquids (LNAPLs) was used as an example, and a scientific screening and combination procedure was developed in this study by considering the distribution characteristics of contaminants. Through the procedure, a technology mix, which includes institutional control, risk monitoring, emergency response, multiphase extraction, interception ditch, monitoring of natural attenuation, hydrodynamic control, as well as some alternative technologies, was found, aiming at different locations and strata. The clear spatial relationship concept promises to enhance the effectiveness of contaminated site remediation. The proposed method only gave us a technical framework and should be tested and enriched in future studies. [ABSTRACT FROM AUTHOR]

Environmental justice is an important topic that can be better understood by using the tools of economics. The author of this article describes a data integration exercise that connects data available through government portals: the Environmental Protection Agency's "Superfund Sites Where You Live" interactive map, data on Net Present Values from Superfund Records of Decisions (ROD), and FRED. Created with the principles of backward design, the exercise uses cooperative learning by having students take ownership of sites chosen for investigation, as well as build and test hypotheses regarding the relationship between per capita GDP and site location/cleanup cost. [ABSTRACT FROM AUTHOR]

Reactive powder concrete (RPC) is an efficient type of fine-grained concrete with extreme strength and durability characteristics. The use of RPC allows the construction of such unique objects as pedestrian and automobile bridges, thin-walled architectural forms, protective structures, hazardous waste storage facilities, etc. Obtaining RPC provides for the mandatory use of a significant amount of microsilica as an active mineral additive, which is not always available for use. The article presents the results of comparing the strength characteristics of RPC obtained on microsilica and with its complete replacement with fly ash activated by milling with sodium silicate fluoride. The studies were carried out using mathematical planning of the experiment. Experimental-statistical models of RPC water demand and compressive and flexural strength at different ages have been obtained and analyzed. It is shown that the use of activated ash in the RPC makes it possible to obtain concrete with a strength of 100...110 MPa in 28 days. A method for calculating the composition of the RPC using the obtained models is proposed. [ABSTRACT FROM AUTHOR]

Bioremediation as a bioprocess has great potential to reduce the toxicity of heavy metals such as lead (Pb) from contaminated sites. In this study, the Pb-bioremediation potential of bacteria was evaluated by strain improvement and by preparing different Consortium. To improve the Pb-bioremediation efficiency, the one factor at a time was used to optimize the process factors responsible such as pH, temperature and initial Pb concentration. Among the studied bacteria, mixture culture (containing both strains) was more able to remove Pb than a single culture. Our result found that the most resistant bacterial strain against lead were S1C3 (1) and S4C7 (2). Among these, S1C3 exhibited the highest resistance to lead. Solubilisation of lead in water sample was observed through the consortium of these two bacteria. The 5 consortium were prepared viz. Wild (1+2), UV (1+2), EtBr (1+2), W (1) +UV(2), W (2)+UV (1). These prepared consortia were inoculated in lead medium. After examination through the atomic absorption, it was found that consortium of UV treated bacteria showed maximum removal tendency among the other consortium. [ABSTRACT FROM AUTHOR]

• A screening tool named Colloids-Enhanced Transport (CET) model is developed. • The CET model is based on the enhanced transport of organic pollutants by soil colloids. • The CET model can predict the leaching potential of organic pollutants into groundwater. • The CET model can be used to derive soil quality standards or cleanup target levels. Modeling the fate and transport of organic pollutants at contaminated sites is critical for risk assessment and management practices, such as establishing realistic cleanup standards or remediation endpoints. Against the conventional wisdom that highly hydrophobic persistent organic pollutants (POPs) (e.g., polybrominated diphenyl ethers and polycyclic aromatic hydrocarbons) in surface soils are essentially immobile, mounting evidence has demonstrated the potential of these contaminants leaching into the groundwater, due to enhanced transport by soil colloids. Here, we develop a Colloids-Enhanced Transport (CET) model, which can be used as a simple screening tool to predict the leaching potential of POPs into groundwater, as mediated by soil colloids. The CET model incorporates several processes, including the release of POPs-bearing colloids into the porewater, the vertical transport of colloids and associated POPs in the vadose zone, the mixing of POPs-containing soil leachate with groundwater, and the migration of POPs-bearing colloids in saturated zone. Thus, using parameters that can be easily obtained (e.g., annual rainfall, soil type, and common hydrogeological properties of the subsurface porous media), the CET model can estimate the concentrations of POPs in the saturated zone from the observed POPs concentrations in surface or shallow subsurface zones. The CET model can also be used to derive soil quality standards or cleanup endpoints by back-calculating soil concentrations based on groundwater protection limits. [Display omitted] [ABSTRACT FROM AUTHOR]

• PBDEs and PAHs often co-exist at e-waste recycling sites. • Considerable amounts of BDE-209 and phenanthrene are leached from surface soil. • Leaching potential of BDE-209 is closely related to the release of mineral particles. • Leaching potential of phenanthrene correlates with dissolved organic carbon. Polybrominated biphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) are commonly detected contaminants at e-waste recycling sites. Against the conventional wisdom that PBDEs and PAHs are highly immobile and persist primarily in shallow surface soils, increasing evidence shows that these compounds can leach into the groundwater. Herein, we compare the leachabilities of PBDEs vs. PAHs from contaminated soils collected at an e-waste recycling site in Tianjin, China. Considerable amounts of BDE-209 (0.3–2 ng/L) and phenanthrene (42–106 ng/L), the most abundant PBDE and PAH at the site, are detected in the effluents of columns packed with contaminated soils, with the specific concentrations varying with hydrodynamic and solution chemistry conditions. Interestingly, the leaching potential of BDE-209 appears to be closely related to the release of colloidal mineral particles, whereas the leachability of phenanthrene correlates well with the concentration of dissolved organic carbon in the effluent, but showing essentially no correlation with the concentration of mineral particles. The surprisingly different trends of the leachability observed between BDE-209 and phenanthrene is counterintuitive, as PBDEs and PAHs often co-exist at e-waste recycling sites (particularly at the sites wherein incineration is being practiced) and share many similarities in terms of physicochemical properties. One possible explanation is that due to its extremely low solubility, BDE-209 predominantly exists in free-phase (i.e., as solid (nano)particles), whereas the more soluble phenanthrene is mainly sorbed to soil organic matter. Findings in this study underscore the need to better understand the mobility of highly hydrophobic organic contaminants at contaminated sites for improved risk management. [Display omitted] [ABSTRACT FROM AUTHOR]

Judah Schept's book, "Coal, Cages, Crisis," explores the connection between the construction of new prisons and former mountain top removal coal mines. The book focuses on the proposed federal prison in Letcher County, Kentucky, which has faced opposition from community members and organizations. Schept examines the role of public-private planning commissions in supporting these projects and highlights the economic argument of job creation through prisons. The book also delves into the racial and class dynamics of Appalachia, emphasizing how racial capitalism has contributed to disinvestment and poverty in the region. Additionally, Schept discusses the intersection of prison history and environmental justice, particularly the environmental risks faced by incarcerated individuals. Overall, "Coal, Cages, Crisis" provides a comprehensive analysis of the complex issues surrounding prisons, the coal industry, and the well-being of working people in Appalachia. [Extracted from the article]

Protecting the health of pregnant women from environmental stressors is crucial for reducing the burden of non-communicable diseases. In industrially contaminated sites, this action is particularly challenging due to the heterogeneous pollutant mixtures in environmental matrices. The aim of this study was to evaluate distribution patterns of mercury, hexachlorobenzene and polychlorobiphenyls in the serum of 161 pregnant women recruited in the framework of the Neonatal Environment and Health Outcomes (NEHO) cohort and living both inside and outside the National Priority Contaminated Site (NPCS) of Priolo. Food macro-categories were determined, and serum levels of contaminants were used to perform k-means cluster analysis and identify the role of food in pollutant transfer from the environment. Two groups of mothers with high and low measured pollutant levels were distinguished. Concentrations in mothers in the high-exposure cluster were at least twofold for all the evaluated pollutants (p < 0.0001) and included mothers living inside and outside NPCS, with a predominance of individuals from the NPCS (p = 0.045). Fish consumption was higher in the high-exposure cluster (p = 0.019). These findings suggest a link between contamination of environmental matrices such as sediment with maternal exposure, through the intake of local food. Such consideration appears poorly investigated in the context of contaminated sites. [ABSTRACT FROM AUTHOR]

Bentonite has been an essential component of geosynthetic clay liners due to its low hydraulic conductivity, which has been used as a barrier against hazardous pollutants in landfills. During the drying and wetting processes caused by high temperatures and leachate in landfills, the hydro-structural characteristics of bentonite vary as the moisture content change. This article investigates the effect of dry density and multi-walled carbon nanotubes (MWCNTs) content on the soil shrinkage characteristic curve (SSCC), the soil free-swelling characteristic curve (SFSCC), the soil water characteristic curve (SWCC), and microstructure of bentonite during the drying and wetting processes. Experimental results indicate that the addition of MWCNTs can slow down the volume variation of bentonite at the normal shrinkage stage and at the initial swelling stage and improve the water retention capacity in the low suction range. Meanwhile, reducing bentonite's dry density can increase the void ratio during drying, decrease the void ratio during wetting, and improve the water retention capacity in the low suction range. Dry density and MWCNTs content both have no influence on the SSCC at the residual shrinkage stage and the zero shrinkage stage, the SFSCC at the residual swelling stage, and the SWCC at the high suction range. [ABSTRACT FROM AUTHOR]

Background and Aim: The primary domestic animal in Somali communities is the goat. Their main economic importance is as a food source and a main form of agriculture in the country. There has been a recent decline in the goat population in Somalia, which may be due to the shortage of feed and an increasingly contaminated environment that is affecting the population's food supply and nutritional status. This study aimed to estimate the prevalence and the factors associated with indigestible foreign bodies (IFBs) ingestion in goats in Mogadishu, Somalia. Materials and Methods: A cross-sectional study was conducted at the Somalia Meat Company in Mogadishu, Somalia, in February 2022. A total of 250 goats were included in this study, and records were kept on age, sex, body condition, and location. Following the slaughter, goats were inspected for IFBs, and their stomach compartments were incised and examined. Indigestible foreign body classifications was noted and subjected to analysis using the Statistical Package for the Social Sciences version 26.0. Results: A total of 90/250 (36%; 95% confidence interval [CI]: 30.1-42.3) goats presented IFBs, being 71/90 (79%; 95% CI: 69-87) in the rumen, 12/90 (13%; 95% CI: 7-22) in the reticulum, and seven/90 (8%; 95% CI: 3-15) on both. The most observed IFBs were plastic in 71/90 (79%; 95% CI: 69-87), followed by ropes in eight/90 (10%; 95% CI: 5-18). A high IFB prevalence was observed in goats aged >2-≤3 years (44%), followed by >3 years (36%). The lowest frequency was observed in goats aged <2 years (30%). Overall, there was an association between IFBs in goats and poor body conditions (χ² = 47%, p < 0.04). Conclusion: The absence of a plastic waste disposal system in the area, and communal free-grazing of livestock in highly contaminated sites, appeared to be significant contributors to the high occurrence of IFBs in goats. Therefore, appropriate policies for solid waste management should be implemented. [ABSTRACT FROM AUTHOR]

Hazardous healthcare waste (HCW) management system is one of the most critical urban systems affected by the COVID-19 pandemic due to the increase in waste generation rate in hospitals and medical centers dealing with infected patients as well as the degree of hazardousness of generated waste due to exposure to the virus. In this regard, waste network flow would face severe problems without taking care of hazardous waste through disinfection facilities. For this purpose, this study aims to develop an advanced decision support system based on a multi-stage model that was combined with the random forest recursive feature elimination (RF-RFE) algorithm, the indifference threshold-based attribute ratio analysis (ITARA), and measurement of alternatives and ranking according to compromise solution (MARCOS) methods into a unique framework under the Fermatean fuzzy environment. In the first stage, the innovative Fermatean fuzzy RF-RFE algorithm extracts core criteria from a finite set of initial criteria. In the second stage, the novel Fermatean fuzzy ITARA determines the semi-objective importance of the core criteria. In the third stage, the new Fermatean fuzzy MARCOS method ranks alternatives. A real-life case study in Istanbul, Turkey, illustrates the applicability of the introduced methodology. Our empirical findings indicate that "Pendik" is the best among five candidate locations for sitting a new disinfection facility for hazardous HCW in Istanbul. The sensitivity and comparative analyses confirmed that our approach is highly robust and reliable. This approach could be used to tackle other critical multi-dimensional problems related to COVID-19 and support sustainability and circular economy. [ABSTRACT FROM AUTHOR]

This review describes the instrumental use that the central power of Mexico makes of the territory of Hidalgo state, which is a consequence of colonialism, the intense metabolism of Mexico City (CDMX), and the neoliberal policies derived from the North American Free Trade Agreement (NAFTA). To do this, the term "garbagization" was used to describe the subaltern position of Hidalgo state in relation to the interests of CDMX and the processes of capital accumulation. The consequences of this phenomenon, evident in the environmental degradation caused by mining, the cement industry, and sewage from CDMX, are presented. The concepts of "sacrifice zones" and "environmental hells" are used to explain community actions against the deterioration of air quality in the Apaxco-Tula-Atotonilco corridor, the construction of a hazardous waste landfill in Zimapán, the Tula de Allende Water Plan, and the construction of a sanitary landfill in Atitalaquia. The paper concludes that these actions respond to the historical garbagization of the affected communities and summarizes some key factors to reverse it. [ABSTRACT FROM AUTHOR]

The foam-blocking material formula was optimized through single factor and uniform mixing design experiment methods. The effect of foam material on blocking volatile organic compounds" VOCs) was estimated by VOCs release chamber combined with GC. The structure and stability of foam were characterized by dynamic foam analyzer. The result showed that the volatilization blocking rate of tetrachloroethylene- enemy-heptane and toluene by form was close to 100% within 5 hand the foam structure was stable after 5 h of foaming. The engineering application method of foam-blocking material was established through the engineering demonstration experiment on contaminated site. As the result showed that the foam block rate of VOCs pollutants was 98% within 5 h. [ABSTRACT FROM AUTHOR]

Physics‐based groundwater flow modeling is a useful tool for the design and optimization of pump‐and‐treat systems for groundwater site cleanup. Numerical methods like finite differences and finite elements, and hybrid analytic elements, require boundary conditions (BC) to be assigned to the outer domain of the grid, mesh, or line elements. These outer BC do not always correspond with hydrogeologic features. Common practice in model setup is to either: (1) extend the model domain boundary outward such that introduced artificial outer BCs (e.g., first type head specified, second type flux specified) do not have undue influence on near‐field scale simulations; or (2) assign outer BCs to capture the effective far‐field influence (e.g., third type head‐dependent flux). Groundwater flow modeling options for assigning BCs were demonstrated for the extensively documented Dual Site Superfund cleanup in Torrance, California. The existing MODFLOW models for the Dual Site scale and the Los Angeles basin scale document the current hydrogeologic conceptual site model. Simplified analytic element AnAqSim models at the LA Basin scale, West Coast Subbasin scale, and Dual Site scale, were used for mapping near‐field domain velocity vector fields and pathline envelopes. The pump‐treat‐inject system demonstrated hydraulic containment and showed pathline envelopes relatively insensitive to BC choices. However, the near‐field domain boundary groundwater flow fields were sensitive to BC choices. The Los Angeles basin case study demonstrated the use of analytic element groundwater modeling for testing stress dependent boundaries during site pump‐treat‐inject design. Article impact statement: Analytic element model demonstrates impact of boundary conditions choices for pump‐treat‐inject system in retrospective case study Los Angeles basin. [ABSTRACT FROM AUTHOR]

This review elucidates different bioremediation approaches used for degradation of HCH from contaminated sites. It highlights the significance of degradative pathways, microbial diversity and impact of different environmental factors for developing viable bioremediation strategies. The application of innovative biotechnological approaches and a thorough understanding of HCH biodegradation pathways show great promise for the creation of long-term solutions to HCH pollution and the restoration of polluted soil ecosystems. Bioremediation technologies viz. biostimulation, bioaugmentation, phytoremediation have been considered till date for treating HCH-contaminated sites. Different bacterial and fungal strains have been reported for degradation of HCH residues. However, these methods are limited to γ-HCH degradation, at laboratory scale and achieving lower success rate for large scale demonstration trials. This review presents a theoretical background for degradation of different HCH isomers in soil through plants, microbes and through their cooperative interactions. This work briefly overviews the substantial contamination of the environment by HCH residues, along with spontaneous evolution of degradation pathways through various HCH degrading microbes. Bioremediation mechanism and pathways of HCH degradation through plants and microbes have been discussed thoroughly. Through molecular and genetic investigations, the complex metabolic pathways used by these microbes, including reductive dechlorination, hydrolysis, and ring cleavage, has been clarified. This study seeks to give a thorough summary of recent discoveries and developments in bioremediation methods for soil HCH degradation. Numerous microbial consortia, including fungi, plants, and bacteria have been recognised as important participants in the transformation of HCH. [ABSTRACT FROM AUTHOR]

Sea‐level rise (SLR) will cause coastal groundwater to rise in many coastal urban environments. Inundation of contaminated soils by groundwater rise (GWR) will alter the physical, biological, and geochemical conditions that influence the fate and transport of existing contaminants. These transformed products can be more toxic and/or more mobile under future conditions driven by SLR and GWR. We reviewed the vulnerability of contaminated sites to GWR in a US national database and in a case comparison with the San Francisco Bay region to estimate the risk of rising groundwater to human and ecosystem health. The results show that 326 sites in the US Superfund program may be vulnerable to changes in groundwater depth or flow direction as a result of SLR, representing 18.1 million hectares of contaminated land. In the San Francisco Bay Area, we found that GWR is predicted to impact twice as much land area as inundation from SLR, and 5,282 additional state‐managed sites of contamination may be vulnerable to inundation from GWR in a 1.0 m SLR scenario. Increases of only a few centimeters of elevation can mobilize soil contaminants, alter flow directions in a heterogeneous urban environment with underground pipes and utility trenches, and result in new exposure pathways. Pumping for flood protection will elevate the saltwater interface, changing groundwater salinity and mobilizing metals in soil. Socially vulnerable communities are disproportionately exposed to this risk at both the national scale and in a regional comparison with the San Francisco Bay Area. Plain Language Summary: We estimated the number of sites with known contamination in the US Superfund program at the national scale and found 326 Superfund sites that may be exposed to inundation from below as rising sea levels push groundwater higher along the coast. California, North Carolina, Virginia, and New York have the largest area of federally managed contaminated land that may be exposed. Thousands of additional sites are managed by state agencies. We conducted a comparison in the San Francisco Bay Area that included state‐managed sites. We found that more than 5,000 sites in the San Francisco region may be exposed to rising groundwater with sea‐level rise (SLR) of 1.0 m, including 1,480 open sites, and an additional 3,817 closed sites that may contain residual contaminants. If the ratio of Superfund to state‐managed sites in this region (1:406) holds, the number of at‐risk contaminated sites nationally may be more than 132,000. Low‐income residents and people of color are disproportionately represented near these sites and therefore may face higher risks. Additional sub‐regional research is urgently needed to understand these exposures. Interactions will occur between the salinity of rising coastal groundwater and shallow pumping, affecting infrastructure and building foundations. Adaptation plans must consider rising groundwater to avoid widespread failures. Key Points: Rising sea levels will cause rising groundwater to inundate some coastal contaminated sites, mobilizing pollutants and causing corrosionWe found 326 Superfund sites that may be at risk nationally, and more than 5,000 state managed sites in a San Francisco Bay area comparisonSocially vulnerable communities are disproportionately exposed to this hazard, with potential impacts on indoor air, foundations and infrastructure [ABSTRACT FROM AUTHOR]

Areas immediately adjacent to 16 of the first US national priority (NPL) hazardous waste sites that also had pre‐superfund emergency actions were examined to measure local stigma. Four decades after their NPL designation, I found marked variation in these areas' social, public health and environmental attributes. About one‐third of these small areas fit the stereotype of stressed areas with environmental injustice challenges. Yet, another one‐third of these sites have better measurable outcomes than a combination of their host states and counties. For example, they have elevated levels of broadband access and their local jurisdictions are classified as safe and attractive to families. I conclude that long‐term stigma around a Superfund site was limited by US EPA actions, as well as by progressive state and local governments, and community groups, in other words, contributions from parties at multiple geographical scales. [ABSTRACT FROM AUTHOR]

At contaminated sites, groundwater monitoring results are commonly used (quantitatively or qualitatively) to predict remediation timeframes. If results are predictive, then there should be a strong positive correlation between attenuation rates for the first half of a temporal monitoring record and attenuation rates for the second half of the same record. We utilized the GeoTracker database to evaluate the power of historical groundwater monitoring results to predict future attenuation rates. For two data sets (petroleum and chlorinated solvent), we found a small negative correlation between the first‐order concentration vs. time attenuation rate observed during the earlier part of the monitoring record and the later part of the monitoring record: benzene—correlation coefficient (r) = −0.11, methyl tert‐butyl ether (MTBE)—r = −0.12, trichloroethene (TCE) = −0.12. For each data set, a small negative correlation between the first‐order attenuation rate observed during the earlier part of the monitoring record and the later part of the monitoring record was also observed for a subset of monitoring records exhibiting the best model fits (R2 > 0.8), a subset with a statistically significant (p < 0.05) positive attenuation rate for the first half of the monitoring record. For the TCE data set, this negative correlation was also observed for a subset of monitoring records with no change in site remedy during the monitoring period (r = −0.22). Our analysis suggests that the historical concentration vs. time attenuation rate for a contaminant at an individual site or monitoring well is a poor predictor of the future rate. [ABSTRACT FROM AUTHOR]

Heterogeneous glacial deposits dominate large parts of the Northern Hemisphere. In these landscapes, high‐resolution characterization of the geology is crucial for understanding contaminant transport. Geological information is mostly obtained from multiple boreholes drilled during a site investigation, but such point‐based data alone do not always provide the required resolution to map small‐scale heterogeneity between boreholes. Crosshole ground penetrating radar (GPR) is suggested as a tool for adding credible geological information between boreholes at contaminated site investigations in industrial sites where infrastructure, such as electrical installations, can pose a challenge to other geophysical methods. GPR data are sensitive to the dielectric permittivity and the bulk electrical conductivity, which can be related to the distribution of water content and sand/clay occurrences. Here we present a detailed crosshole GPR dataset collected at an industrial contaminated site in a clay till setting. The data are processed using a novel inversion approach where information on changes in the velocity and attenuation of the radar signal are obtained independently. The GPR results are compared to borehole logs, grain size analyses, and relative permeability data from the site. The GPR data analysis provided valuable information on the understanding of the lateral geological variability. A silt layer with a thickness of a few decimeters, likely important for flow characterization, was confirmed and resolved by GPR data. Our findings suggest that crosshole GPR has the potential for contributing with high‐resolution geological information by filling the data gap between boreholes, thereby becoming a relevant tool in contaminated site investigations. [ABSTRACT FROM AUTHOR]

Heavy metal accumulation increases concentrations of toxic contaminants in soil and the environment. They possess momentous warnings to ecosystems throughout the world. Industries and agricultural activities introduce heavy metals/metalloids into the ecosystem which affects agricultural crops and poses various potential health threats to humans and animals by entering the food chain. Therefore, neglecting its deleterious effects on the environment may worsen the current situation. Thus, the need for bioremediation is of paramount importance in the reclamation of polluted soils and lands. The technique involves the use of microorganisms, such as bacteria, fungi, and algae, to lower/remove the toxicity of contaminants in affected regions. It is an environment-friendly, efficient, and cost-effective solution for soil heavy metal and metalloid degradation in both in situ and ex-situ conditions. Microorganisms can also be genetically modified to be efficient for pollutant degradation. Better alternatives such as nanobioremediation, vermiremediation, and genetically modified microbes have been discussed in detail. These integrated approaches can be more effective than conventional approaches for the restitution of contaminated sites and reducing the toxicity of hazardous compounds. The present review will provide a deep interpretation of the various bioremediation techniques, their merits, and their limitations to the readers. It will also give insights on how these techniques can be implemented as future support to direct the global problem of metal remediation. [ABSTRACT FROM AUTHOR]

Soil–bentonite cut-off walls have been widely used to control landfill pollution but they do not have good chemical compatibility with landfill leachate. Attapulgite can be substituted for bentonite in landfill cut-off walls. However, little is known about the chemical compatibility of attapulgite cut-off walls and leachate. This study experimentally investigated the chemical compatibility of attapulgite cut-off wall specimens with organic and inorganic contaminants and found that a sand–attapulgite cut-off wall has good chemical compatibility with organic contaminants. A CaCl2 solution was used to represent inorganic contaminants, and chemical oxygen demand (COD) was used as an indicator of organic content. The hydraulic conductivity of the cut-off wall initially decreased and then increased to become approximately constant as Ca2+ concentration increased. Changes in COD concentration were divided into a decreasing stage (0–10,000 mg/L) and a constant stage (10,000–40,000 mg/L). The increase or decrease in hydraulic conductivity was by no more than one order of magnitude. The increase in the hydraulic conductivity of the sand–attapulgite cut-off wall is explained in terms of bound water content and pore structure. An increase in Ca2+ concentration decreased the bound water content of the cut-off wall while the CaCl2 solution increased macropore and mesopore volume and decreased small pore volume in the sand–attapulgite cut-off wall. The purpose of this study was to elucidate the chemical compatibility of a sand–attapulgite cut-off wall with organic and inorganic contaminants and to increase the understanding of the interactions between the cut-off wall and the contaminants. The results of this research are informative for improving the application, design, and construction of sand–attapulgite cut-off walls. [ABSTRACT FROM AUTHOR]