Pollution Plume Research Articles

Modeling the dispersion of wastewater pollutants in Gaza's coastal waters

The disposal of sewage water in Gaza City has emerged as a significant issue with extensive environmental repercussions. This study seeks to investigate the pollution plume resulting from the discharge of untreated or partially treated sewage water through Gaza City's main outlet into the Mediterranean Sea. Additionally, it aims to predict scenarios for various design configurations of submerged outfalls with either single-port or multi-port diffusers and compare these scenarios against the Environmental Protection Agency (EPA) recreational water quality criteria. According to the EPA, the concentration of Enterococci bacteria at the edge of the mixing zone should not exceed 35 CFU/100 ml to minimize the adverse environmental impact on the marine ecosystem.CORMIX software was utilized as a modeling tool to simulate the dispersion and attenuation behavior of pollutants resulting from this process and to conduct a sensitivity analysis to optimize the design configuration of the sewage disposal system. The simulation considered the influence of ambient conditions (ambient velocity, wind, and seawater density), effluent characteristics (density, flow rate, pollutant concentration, and pollutant decay rate), outfall configuration, and sea bathymetry.Simulation results indicate that a single-port diffuser is unsuitable according to EPA recreation standards. Multi-port unidirectional diffusers, extending 490 m from the shore into the water, meet the required standards. To a lesser extent, the multi-port staged distributor also meets the standards and is more recommended for counter-current situations.

On-site monitoring and numerical simulation on groundwater flow and pollution plume evolution in a hexavalent-chromium contaminated site

Accurately ascertaining spatiotemporal distribution of pollution plume is critical for evaluating the effectiveness of remediation technologies and environmental risks associated with contaminated sites. This study concentrated on a typical Cr(VI) contaminated smelter being currently remediated using pump-and-treat (PAT) technology. Long-term on-site monitoring data revealed that two highly polluted regions with Cr(VI) concentrations of 162.9 mg/L and 234.5 mg/L existed within the contaminated site, corresponding to previous chromium slag yard and sewage treatment plant, respectively. The PAT technology showed significant removal performance in these highly polluted areas (>160 mg/L) after six months of pumping, ultimately achieving complete removal of the pollutants in these high-pollution areas. Numerical simulation results showed that although the current remediation scheme significantly reduced the Cr(VI) pollution degree, it did not effectively prevent the incursion of the pollution plume into the downstream residential area after 20 years. Additionally, an improved measure involving supplementary pumping wells was proposed, and its remediation effects were quantitatively evaluated. Results indicated that the environmental pollution risk of groundwater downstream could be effectively mitigated by adding pumping wells, resulting in a reduction of the pollution area by 20 % in the case of adding an internal well and 41 % with the addition of external wells after 20 years. The findings obtained in this study will provide an important reference and theoretical guidance for the reliability analysis and design improvement of the PAT remediation project.

High-Resolution WRF Modeling of Wind and Thermal Regimes with LCZ in Almaty, Kazakhstan

This study evaluates the effectiveness of the Weather Research and Forecasting (WRF) model in simulating high-resolution atmospheric conditions for Almaty, Kazakhstan, a city prone to stagnant winter air. While the previously used Bougeault and Lacarrere scheme for parameterizing the planetary boundary layer was applied in high-resolution modeling, the number of vertical levels was increased, and a detailed local climate zones (LCZs) map was included. Ground-based observations from meteorological stations and monitoring stations, remote sensing data, and radiosonde measurements are used to verify the model. Comparison results with ground-based observations show that the WRF model with the LCZ map provides a better representation of the wind and thermal regimes of Almaty compared to the three-class land use map, including in high resolution. A good correspondence of wind direction is demonstrated by comparing the modeling results with pollutant transport plumes recorded by remote sensing data. In addition, a good correlation was found between land surface temperature from satellite data and air temperature simulated by WRF with a resolution of 333 m. A comparison of simulated data and aerological measurements confirmed that downscaling did not have a significant impact on boundary layer calculations. Analysis of turbulent processes showed that the adopted model effectively describes the attenuation and dissipation of turbulent kinetic energy and reflects the typical diurnal variations of meteorological processes in the atmosphere of Almaty in the anticyclonic winter period. The results of high-resolution WRF modeling can form the basis for the development of a hybrid system capable of modeling atmospheric processes at the building level.

Integrated framework to assess soil potentially toxic element contamination through 3D pollution analysis in a typical mining city

Soil potentially toxic elements (PTEs) pollution of contaminated sites has become a global environmental issue. However, given that previous studies mostly focused on pollution assessment in surface soils, the current status and environmental risks of potentially toxic elements in deeper soils remain unclear. The present study aims to cognize distribution characteristics and spatial autocorrelation, pollution levels, and risk assessment in a stereoscopic environment for soil PTEs through 3D visualization techniques. Pollution levels were assessed in an integrated manner by combining the geoaccumulation index (Igeo), the integrated influence index of soil quality (IICQs), and potential ecological hazard index. Results showed that soil environment at the site was seriously threatened by PTEs, and Cu and Cd were ubiquitous and the predominant pollutants in the study area. The stratigraphic models and pollution plume simulation revealed that pollutants show a decreasing trend with the deepening of the soil layer. The ranking of contamination soil volume is as follows: Cu > Cd > Zn > As > Pb > Cr > Ni. According to the IICQs evaluation, this region was subject to multiple PTE contamination, with more than 60% of the area becoming seriously and highly polluted. In addition, the ecological hazard model revealed the existence of substantial ecological hazards in the soils of the site. The integrated potential ecological risk index (RI) indicated that 45.7%, 10.13%, and 4.15% of the stereoscopic areas were in considerable, high, and very high risks, respectively. The findings could be used as a theoretical reference for applying multiple methods to integrate evaluation through 3D visualization analysis in the assessment and remediation of PTE-contaminated soils.

Extreme ozone episodes in a major Mediterranean urban area

Abstract. This study analyses three extreme ozone (O3) episodes that occurred in Barcelona (NE Spain) during the summers of 2015, 2018, and 2019. These episodes exceeded the EU's hourly information threshold (180 µg m−3) for the first time since at least the year 2000, raising concerns due to Barcelona's large population. By employing experimental data and various modelling tools, our main objective is to elucidate the underlying phenomena of these recent O3 episodes and improve predictive capabilities. The findings indicate that the factors contributing to these occurrences are largely consistent across episodes. These factors, with estimated O3 contributions specified for particular instances, comprise (i) initial O3 accumulation in surrounding coastal areas; (ii) weekend occurrence, accompanied by the corresponding weekend effect (+15 µg m−3); and (iii) the prevalence of Tramontana meteorological conditions during above-normal temperatures, which (iv) force the convergence of multiregional polluted air masses to the city (+45–65 µg m−3). Major source areas include regions of southern France through the Gulf of Lion, the interior of the Mediterranean, and eastern Spanish coastal regions, including Barcelona's pollution plume. Some of these factors, which may manifest in the days preceding the episodes, are observable or can be anticipated. This study enhances understanding of the mechanisms driving extreme O3 episodes recently observed in Barcelona and provides valuable insights for prediction.

Green buffers near industrial plants, examples in Jefferson County TX

Green buffers between industrial plants and residential areas have multiple purposes in mitigating air pollution and protecting the environment. This study focuses on providing information on examples of green space development by industries near residential areas in Jefferson County, Texas. One represents a full buffer where residences were totally removed, another is a partial buffer where some residences were removed in a neighborhood and the third represents vegetation of a formerly industrial facility. Additional estimates on benefits of buffer spaces with respect to a pollutant plume are also considered. The study used geospatial and property data from 1966 to 2020. The transition from a residential area to a full or partial buffers highlights possible mitigation of air pollution impacts while serving additional functions, such as boosting stormwater infiltration and improving the aesthetic attractiveness of the area. The transformation from oil tanks to forested space may display the potential for environmental remediation, but not all spaces are suitable for fully forested buffers, as safety and other limitations should be considered. With the analysis of the classic Plume Equation insights can be provided regarding the possible impact of green buffers on ground-level pollutant concentrations. The calculations for atmospheric stability classes A-F and for various stack heights provide an understanding of how different conditions may affect the pollutant concentrations. The presence of a green buffer can play a crucial role in controlling ground-level pollution concentrations and reduce a community’s perception of risk.

Geometry, Extent, and Chemistry of Fermentative Hot Spots in Municipal Waste Souk Sebt Landfill, Ouled Nemma, Beni Mellal, Morocco

The presence of fermentative hotspots in municipal waste dumps has been reported for several decades, but no study has focused on their size and shape. The uncontrolled landfill of Soub Sekt, covering an area of about 8 hectares in the Tadla plain in Morocco, is the source of a permanent pollution plume in the groundwater, detected by self-potential (SP) measurements. The study aims to detect and characterize these hotspots as well as the leachates that form within them. These hotspots are typically circular and smaller than 3 m in size, and they are concentrated within recent waste deposits. Intense electron transfer activities, particularly during redox reactions leading to metal solubilization, result in very low SP values (down to −60 mV), facilitating their detection. Several successive field campaigns suggest that they are active for 2–3 weeks. Due to the low permeability of the soils, highly mineralized leachates (average Electrical Conductivity 45 mS cm−1) rich in organic ions accumulate on the soil surface at the base of the waste windrows. There, they evolve by concentration due to evaporation and oxidation due to slow diffusion of atmospheric O2. Despite the small size of the hotspots generating the leachates, the accumulation of leachates in ponds and the low soil permeability limits the percolation rate, resulting in moderate but permanent groundwater pollution.

Cooperative Deep Reinforcement Learning for Dynamic Pollution Plume Monitoring Using a Drone Fleet

Cooperative Deep Reinforcement Learning for Dynamic Pollution Plume Monitoring Using a Drone Fleet

Neglected flow direction detection in landfill water cycle: Precise characterization of leachate distribution through joint inversion of electrical resistivity and self-potential data

The leakage of leachate is a crucial but often overlooked hydrological process in the landfill water cycle. The concealed leakage of leachate not only leads to soil and groundwater pollution in surrounding areas but also affects the distribution of water and the metabolism of organic matter within the landfill. To accurately quantify this concealed hydrological process, we propose a method for detecting leachate leakage based on joint inversion of multi-source geophysical exploration data. By integrating multiple geophysical exploration data (resistivity and self-potential information), we reconcile the spatial differences in different exploration data to improve the accuracy of leachate and its pollution plume imaging. Additionally, we introduce an efficient alternating iteration technique within the joint inversion framework to ensure convergence of separately inverted models toward similar spatial structures. Simulation results indicate that: (1) for the early detection of small-scale high-concentration leachate pollution, the proposed confidence-induced joint inversion framework (CI-JIF) improves precision by 15.6 % compared to separate inversions. (2) for the detection of leachate long-term diffusion, CI-JIF accurately delineates the distribution of widespread high-concentration leachate, improving precision by 17.4 % compared to separate inversions. Further on-site experiments demonstrate that CI-JIF can more accurately reconstruct the distribution of leachate.

Combined effects of aquifer heterogeneity and subsurface dam on nitrate contamination in coastal aquifers

Subsurface dams are effective for seawater intrusion mitigation, yet they can cause upstream nitrate accumulation. This research examines the interplay between subsurface dam construction and aquifer layering on nitrate pollution in coastal settings, employing numerical models to simulate density-driven flow and reactive transport. The study reveals that while subsurface dams are adept at curbing seawater intrusion, they inadvertently broaden the nitrate accumulation zone, especially when a low-K layer is present. Heterogeneous aquifers see more pronounced nitrate accumulation from subsurface dams. This effect is pronounced as it influences dissolved organic carbon dynamics, with a notable retreat inland correlating with the expansion of the nitrate pollution plume. A critical finding is that controlling seawater intrusion via dam height adjustment within the Effective Damming Region effectively reduces nitrate levels and bolsters freshwater output. However, exceeding the critical threshold—where the dam surpasses the low-K layer's bottom—results in a substantial shift in nitrate concentration, underscoring the need for precise dam height calibration to avoid aggravating nitrate pollution. This study's innovative contribution lies in its quantification of the nuanced effects of subsurface dams in stratified aquifers, providing an empirical basis for dam design that considers the layered complexities of coastal aquifers. The insights offer a valuable framework for managing nitrate contamination, thus informing sustainable coastal groundwater management and protection strategies.

Stratified migration and distribution of the constituents of coal tar in the stratum

Coal tar (CT) is widely used in the rubber industry to produce a reinforcing substance known as carbon black. Due to the complexity constituents of CT, the migratory dynamics of its constituents have not been characterized, resulting in contamination of soil and groundwater. To understand the migration and distribution characteristics of different nature components of CT in the study site, the distribution and migration patterns of total petroleum hydrocarbons (TPHs), polycyclic aromatic hydrocarbons (PAHs), and Dense Non-Aqueous Phase Liquids (DNAPLs, ρ≫1 g/cm³) in soil and groundwater in a rubber enterprise were characterized and analyzed. We found that: the different components in CT settle at different points in the soil as they migrate, exhibiting stratification. Specifically, TPHs in soil and groundwater are mainly concentrated in the shallow layer near the tank area, and the maximum concentration is 113,000 mg/kg; PAHs are more migratory than TPHs, and the maximum concentration of PAHs is 7408 mg/kg. Most PAHs are concentrated in the middle layer and above; DNAPLs tend to be transported to deeper stratum, penetrating deeper into the terrain and aggregating into pools (depth＞13 m). In addition, the inherently slow flow of groundwater slower groundwater flow does not significantly impact the further migration of pooled DNAPLs, but it does influence the orientation of their pollution plume. This study provides a more accurate characterization of the dynamics of pollutants associated with rubber enterprises; these results bring forth a theoretical basis for the remediation and management of pollution linked with CT.

A new two-step particle tracking and channels model method for preferential 3-D flow and transport in large DFNs of fractured aquifers

A new two-step method has been developed for predicting three-dimensional (3-D) pollutant plumes and breakthrough curves (BTC) in fractured aquifers. Predicting fluid motion fields and pollutant concentrations in groundwater is a challenging task, due to the difficulties in building a 3-D discrete fracture network (DFN) with the same geometry of fractures and interconnections as in the studied aquifer and the computational complexity of the problem being modeled. To improve the representation of DFN, geological characterization of fracture apertures was performed using field well-pumping data as the prerequisite for the modeling approach. The modeling was performed in two steps: first, 3-D particle tracking following streamline (PTFS) simulations in DFN backbones, and second, a 3-D channels model (CM) analytical solution. The PTFS simulations captured the mean properties of the 3-D velocity field relevant to spatial and temporal transport along preferential flow pathways of a fractured aquifer. The 3-D CM solution yielded the exact BTC of concentrations accounting for the slowest flow pathways typically excluded from DFN backbones extraction methods. The PTFS/CM simulations were initially performed at the lab scale on a 3-D 20 m rock block from the Bari (South Italy) fractured aquifer. Results were consistent with the chlorophyll-A BTC obtained from a well-to-well tracer experiment. Subsequently, the capability of the new method was tested by increasing the scale of simulations to a larger 3-D DFN of 200 m with 2,200 fractures. The resultant BTC was obtained in 32 min, showing the proposed PTFS/CM technique can rapidly determine complex 3-D solutions in heterogeneous fracture-dominated aquifers. The applied Lagrangian and Eulerian techniques can provide quasi-deterministic BTCs and 3-D maps of pollutant concentrations, avoiding extensive computations required for conforming mesh methods. Moreover, the solution does not require multiple randomly arranged DFN realizations, as in particle tracking-based stochastic methods. These results have significant implications in modeling transport at the aquifer scale, where DFNs are composed of thousands of fractures.

A tracer model nowcast/forecast study of the Tampa Bay, Piney Point effluent plume: Rapid response to an environmental hazard

An emergency discharge of nutrient-rich effluent from the defunct Piney Point fertilizer stack into Tampa Bay at Port Manatee occurred from 30 March–8 April 2021. This resulted in a pollutant plume that evolved over time and space across the entire bay, including its environmentally sensitive marine preserves, and out onto the adjacent continental shelf. As a rapid response to environmental concerns, the plume evolution was simulated using the high resolution, unstructured grid, Tampa Bay Coastal Ocean Model (TBCOM) nowcast/forecast system, with an embedded tracer module that included realistic point discharge rates. Normalized tracer distributions were automatically updated each day, providing 1-day hindcasts and 3.5-day forecasts. Due to mixing and advection, tracer concentration was quickly reduced by two or more orders of magnitude as the plume spread out. Highest tracer concentrations hugged the southeastern Tampa Bay shoreline during the first week. Lower tracer concentrations were gradually advected to the western side of Tampa Bay, and the tracer was slowly flushed out of the bay to be transported primarily northward along the coast. The modeled plume evolution served as principal guidance for coordinating environmental monitoring by state, local and academic personnel. The model results also provide a basis for future multidisciplinary studies.

Characteristics and sources of atmospheric ammonia at the SORPES station in the western Yangtze river delta of China

Ammonia (NH3) is an important air pollutant with crucial impacts on air quality, ecosystems and climate change. However, NH3 is not included in routine air quality monitoring and the availability of long-term NH3 measurements is still limited, resulting in large uncertainties in our knowledge of the spatial distribution and sources of NH3. Here we performed 1 year (March 2021–February 2022) of atmospheric NH3 measurements at a regional background station, the Station for Observing Regional Processes of the Earth System (SORPES) in the western Yangtze River Delta of China. We found that the annual mean NH3 concentration was 12.2 ± 4.6 ppb and exhibited apparent seasonal variations, with a maximum in June and a minimum in February, influenced by agricultural activities, air temperature, gas-particle partitioning and precipitation. Moreover, air temperature and absolute humidity correlated well with NH3, indicating that they are important factors in influencing NH3 levels. The diurnal variation of NH3 showed a single peak in the morning and higher concentrations during the day. In spring and autumn, the NH3 morning peak can be attributed to dew evaporation. The air mass backward trajectory, local wind direction and velocity analysis suggested that NH3 was influenced by both local emissions and regional transport from nearby cities. During the COVID-19 lockdown, a strong reduction of NOx (−77%) and a weak reduction of NH3 (−14%) were observed compared to the pre-lockdown, highlighting that traffic emissions have a minor impact on NH3 at the SORPES station. Our results provide more insights into the characteristics and sources of atmospheric NH3 in background regions influenced by mixed air pollution plumes.

Numerical simulation of different pollutant control measures around an old landfill contaminated site: A field scale study

The remediation of contaminated soils is a great challenge for global environmental sciences and engineering. The landfill was a kind of infrastructure to deal with waste from different sources while it would also cause the threat to groundwater. Cut-off walls and pumping wells were usually applied in the landfill to prevent the spread of pollutants to wider areas. However, the combination of using both of methods was rarely analyzed, especially using field data for calibrating and fitting groundwater flow and pollutant transport. 7 monitoring wells were arranged in the study area to survey the subsurface seepage. The pollution monitoring was carried out for a period of 50 days, covering 31 types of inorganic and organic pollutants. The concentration of 2,4,6-trichlorophenol (TCP) was 556.7 times greater than the standard concentration. A coupled numerical model of groundwater flow and pollutant transport was developed to assess the effectiveness of various control methods. Three options were tested, including the implementation of a single cut-off wall as well as a combination of a cut-off wall and a pumping well, for preventing the discharge of pollutants from landfills. The combination of a cut-off wall and a pumping well is the best strategy for removal of TCP. The combination approaches lead to a reduction of pollution plumes by a factor of 11 compared to the case without pollution control measures. The research findings may provide a basis and reference for the application of cutoff walls and pumping well in landfill sites or contaminated groundwater.

2,4,6-TCP migrates and transforms in different cultivated soil in China: Kinetic analysis and mechanistic modeling

Organochlorine pesticides are widely used in agriculture, wood preservation, pulp bleaching and other fields, which increased the pollution risk of cultivated land. In this study, a typical organochlorine pesticides-2,4,6-TCP was conducted as the target pollutants to investigated the migration and transformation characteristics in different cultivated soils in China. The results indicated that the adsorption of 2,4,6-TCP in soil samples was in order: black soil＞laterite＞fluvo-aquic soil, and the maximum adsorption was 71.0870, 27.0575 and 6.1292 mg/kg, respectively. The dispersion coefficient of black soil, laterite and fluvo-aquic soil was 0.0329, 0.0501 and 0.0149, and the hysteretic factor R was 5.381, 1.455 and 2.238, respectively, indicating that the migration ability of 2,4,6-TCP in different cultivated soils samples was in order: black soil＞laterite＞fluvo-aquic soil. The fitting results of one-dimensional migration model indicated that the model well reflected the migration and transformation of 2,4,6-TCP in different cultivated soil samples. Meanwhile, the Two-dimensional migration model fitting results indicated that the maximum concentration of 2,4,6-TCP of different cultivated soil samples were found along the longitudinal flow direction, reaching 40% of the initial pollution concentration at 15 m, corresponding to the center of the pollutant plume.

Detection of forest fires and pollutant plume dispersion using IoT air quality sensors

The widespread adoption of Internet of Things (IoT) sensors has revolutionized our understanding of the formation and mitigation of air pollution, significantly improving the accuracy of predictions related to air quality and emission sources. This study demonstrates the use of IoT air quality sensors to detect forest fire incidents by focusing on an area affected by forest fires in Tak Province, Thailand, from January to May 2021. We employed PM2.5 and carbon monoxide measurements from IoT sensors for forest fire detection and utilized the number of hotspots reported through satellite and human observations to identify forest fire incidents. Our data analysis revealed three distinct periods with forest fires and three periods without fires (non-forest fires). For model training, two forest fire and non-forest fire periods were selected and the remaining periods were set aside for validation. J48, a computer algorithm that helps make decisions by organizing information into a tree-like structure based on key characteristics, was used to construct the decision-tree model. Our model achieved an accuracy rate of 72% when classifying forest fire incidents using the training data and a solid accuracy of 69% on the validation data. In addition, we investigated the dispersion of PM2.5 plumes using a regression model. Notably, our findings highlighted the robust explanatory power of the lag time in PM2.5, for predicting PM2.5, in the next 15 min. Our analysis highlights the potential of IoT-based air quality sensors to enhance forest fire detection and predict pollution plume dispersion once fires are detected.

A numerical assessment of the dispersion of dissolved pollutants in the Arabian Gulf associated with the Barakah nuclear power plant

The main goal of this study is to investigate long-term dispersion of quasi-conservative pollutants in the Arabian Gulf, such as anthropogenic radionuclides, associated with regular and potential accidental emissions of those from the recently commissioned Barakah nuclear power plant (BNPP) in the western United Arab Emirates (UAE). In particular, discharge of tritium 3H, which is expected to be present in the cooling water effluent during normal operation of the plant, raises concerns about eventual build-up of tritium and tritiated water plume in the poorly flushed western UAE region. A good understanding of the transport processes in the sea is also essential for contingency planning in case of accidental releases of harmful radionuclides such as Cesium 137Cs, and it provides basis for more comprehensive models of the marine radioactivity. To achieve this goal, a three-dimensional unstructured-grid hydrodynamic and tracer dispersion model of the Arabian Gulf, focusing on the western UAE area, was established using Semi-implicit Cross-scale Hydroscience Integrated System (SCHISM). The model was validated against water level, current and temperature data collected in the UAE waters during 2017–2018. The horizontal resolution of the numerical mesh of this model varied from approximately 4 km in the Sea of Oman to 0.1 km near Barakah to properly account for the effect of numerous small islands, narrow straits between them, and other fine-scale coastal features on the hydrodynamic. Two types of scenarios were considered: (1) direct continuous release of a tracer dissolved in the BNPP's heated effluent, and (2) offshore fallouts from the atmosphere onto the water surface. The simulations were conducted over the period of 2 years. Direct continuous tracer discharge was found to cause a notable accumulation of it in the Southern Shallows region, especially Barakah – Sir Bani Yas – Dalma – Yasat Islands zone, where the volume-averaged concentration converged to approximately 7.4% of the excess concentration of the tracer in the BNPP effluent, with the Gulf-averaged saturation concentration projected at approximately 0.37%. The quasi-half-saturation states for these two regions were reached in approximately 0.4 and 1.8 years, respectively. A pollutant plume resultant from an atmospheric fallout generally tends to move eastward along the UAE coast, with the separation occurring in the western approaches of the Strait of Hormuz, between Dubai and Ras Al Khaimah, where a denser near-bed portion continues sinking down and then exits into the Sea of Oman, while a near-surface portion is entrained into the general counterclockwise circulation in the Gulf, and it is carried along the Iranian coast to the upper northwestern Gulf. After the period of 2 years, 60–70% of the total initial tracer load is estimated to be washed out from the Gulf. Despite relatively low probability of the occurrence of such wind conditions, which could result in radionuclide fallouts north of Dalma Island, a notably faster spread of contaminated waters, with the estimated 5–6 weeks for a peak concentration to reach Abu Dhabi City in the studied case, would make emergency response more challenging.

Tracking groundwater pollution plumes at landfill sites using borehole hydrochemical and hydrodynamic profile (BHHP) method

Groundwater pollution at landfill sites poses a significant risk to human health and ecological security. However, efficiently tracking pollution plumes in a polluted aquifer with variable pollutants remains challenging. In order to track groundwater pollution plumes at landfill sites, an in-situ borehole hydrochemical and hydrodynamic profile (BHHP) method was developed. Total dissolved solids (TDS), oxidation-reduction potential (ORP), and ammonia nitrogen were selected as the hydrochemical indicators. Meanwhile, the hydrodynamic indicators included flow direction and flow velocity of groundwater. Among the three hydrochemical indicators, TDS and ORP were analyzed to be the prior alternative ones for the BHHP application. The BHHP method was successfully applied to track groundwater pollution plumes at a typical valley-type landfill site and its neighboring downstream zone. Consequently, four groundwater pollution plumes of different types and different scales were identified in both horizontal and vertical directions within the depth of 0–50 m, and the various pollution sources for the detected pollution plumes were revealed. Furthermore, the BHHP method was validated using sampling test results of groundwater chloride and chemical oxygen demand at the surveyed landfill site.

Spatiotemporal distribution and pollution control of pollutants in a Cr(VI)-contaminated site located in Southern China

Soil and groundwater Cr(VI) pollution resulting from improper disposal and accidental spills is a critical problem worldwide. In this study, a comprehensive study was conducted to assess the hydrogeological conditions of a contaminated site, obtain spatiotemporal distribution and trend forecasts of pollutant Cr(VI), and determine the feasibility of applying clayey engineered barriers for pollution control. The results showed that the hydraulic conductivity (K) of the clayey barrier (1.56E-5 m/d) is several orders of magnitude lower than that of the stratum beneath the contaminated site, with K values ranging from 0.0014 to 4.76 m/d. Cr(VI) exhibits high mobility and a much higher concentration in the vadose zone, with maximum values of 6100 mg/kg in topsoil and 2090 mg/L in the perched aquifer. The simulation results indicated that the groundwater in the vicinity of the contaminated site, as well as downstream of the Lianshui River, is seriously threatened by Cr(VI). Notably, the pollution plume could occur downstream of the Lianshui River after 8 years. The retention efficiency of clayey engineered barriers will decrease over time, at 61.6% after 8 years and 33% after 20 years. This work contributes to an in-depth understanding of Cr(VI) migration at contaminated sites.