Search

• 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]

Bioretention is a water management practice that is increasingly being applied for runoff quality control. Although previous Bioretention studies have used some techniques to improve nutrient removal, some nutrients still leach out. Therefore, this study used Cascaded Bioretention (CB) by connecting three Bioretention columns in series. The planted Bioretention Column was retrofitted by adding a subsurface drainage module (SDM) below the gravel layer to create a dual saturated zone. This study aimed to investigate the effect of the number of treatments, vegetation, and modified saturated zone on enhancing nutrient removal from agricultural runoff and to understand nutrient removal mechanisms. The removal efficiencies of NH3-N, NO3-N, NO2-N, and TN improved to 89.8%, 49.7%, 49.2%, and 53.4%, respectively. The only negative removal was ON, which significantly decreased by incorporating vegetation and a modified saturated zone. Increasing the number of treatments significantly enhanced TN and ON while maintaining stable removal for other nitrogen compounds. However, phosphorus was less sensitive to increasing the number of treatments. Nitrogen removal could be enhanced by different removal processes such as nitrification, denitrification, mineralization, assimilation by plant uptake, and Anammox. However, phosphorus removal was less complicated, as adsorption and infiltration are likely to be the main removal mechanisms. [ABSTRACT FROM AUTHOR]

Understanding groundwater recharge mechanisms is essential for reliable groundwater recharge estimation for sustainable groundwater resource assessment and management, especially in arid and semiarid areas. In this study, chloride, together with stable isotopes (18O and 2H), in 1‐year rainfall, soil water from representative profiles, and groundwater samples, collected in the Ordos Plateau, northern China were analysed. Groundwater recharge was estimated using unsaturated‐ and saturated‐zone chloride mass balance (CMB). An equation that describes the relationship between chloride concentrations in saturated zone water (Csz) and soil water residence time (τ) was derived. With the help of the relationship, chloride concentrations in unsaturated zone water (Cuz) and in groundwater (Csz) can be used to uncover water flow and chloride transport in the unsaturated zone. The relationship between Csz and Cuz indicates that, the groundwater was recharged mainly by intense rainfall events. Small rainfall events did not lead to groundwater recharge but contributed to the flux of chloride to soil surface. Stable isotopic compositions of 18O and 2H provided corroborative evidence of the recharge processes. The relationship between Csz and τ indicates further that there is no source of chloride in the groundwater other than that from precipitation. Thus, Csz can give more reliable recharge estimates. Cuz was influenced by heavy rainfall‐induced runoff, run‐on and bypass flow events and cannot give reliable recharge estimates. However, if used jointly with Csz, Cuz can help to gain insights into recharge processes and yield groundwater recharge estimates with higher certainty. The outcomes of this study can assist for groundwater recharge investigation and assessment in regions where the assumptions and boundary conditions necessary for the correct application of the CMB method may not be met. [ABSTRACT FROM AUTHOR]

The presented procedure is designed to develop a system of models of the aeration zone and the saturated zone aimed to give a quantitative description of pollutant migration from a near-surface source to groundwater table and to the discharge zones of groundwater flow. The procedure is applied to an area with identified chloride pollution of groundwater. The source of pollution is a salt store, which was operated in the period 1967–2007. The concentration of chloride ion did not decrease after the liquidation of pollution source because of the formation of a secondary source (salination zone) in the aeration zone. Models of the aeration zone and the saturated zone were developed for the area under consideration. The model of the saturation zone was calibrated by monitoring data (groundwater table and chloride-ion concentration). The plume of chloride-ion in the groundwater flow was reproduced in the model in absolute concentrations. The calculations of pollutant migration in the aeration zone was calculated in relative concentrations. Simulation results were used to determine time intervals characterizing the stages of pollution plume formation over the operation time of the salt store, as well as the stages of plume degradation after the store was liquidated. The effect of model parameters for both zones on the results of transport calculations was evaluated to reveal the most significant among them. A series of model scenarios was considered (conservative and softer) to determine the variability of model forecasts. Retrospective model calculations, along with monitoring data, were used to obtain more accurate estimates of parameters, which characterize the deposits in the aeration zone. [ABSTRACT FROM AUTHOR]

The remediation of a polluted site relies, as a first stage, on the proper delineation of the contamination sources. In classical investigations, soil and water samples are collected throughout the field. These measurements allow a quantitative characterization of the gathered materials but only provide information about the medium in the vicinity of the points where they were collected. On the other hand, geophysical techniques can provide a quasi-continuous coverage of the investigated field. This paper describes a geophysical survey that was performed on an industrial site impacted by a chlorinated DNAPL. The precise location of the contamination was needed for the treatment of the saturated zone, while the unsaturated zone was remediated by general excavation of the sediments, followed by separate treatment. As this excavation allowed to get closer to the saturated zone, geophysical measurements were conducted at the bottom of the pit. Whereas Electrical Resistivity Tomography measurements only brought little information, Ground Penetrating Radar drew the remediation operations towards an area that preliminary point measurements had not identified as a possible source location.

The demand for clean and adequate water is rising rapidly with increasing population. This growing demand for water necessitates the measurement of the quantity and quality of water. Simulation modeling has become increasingly popular in the last two decades largely because of their predictive ability. This paper reviews the approaches for simulation modeling in groundwater resources management, focusing on models that have been used to simulate contaminant transport through the aquifer system. Recent research papers that have integrated the models for unsaturated and saturated zones have also been studied and described. Integrated models require assessment of the complex interactions between the groundwater zones and the movement of water and solute through them. Due to this, integrated models provide a more accurate modeling approach than models that have been independently developed for saturated and unsaturated zones. Application of such models is encouraged at the regional level to arrive at the best groundwater management decisions. Practitioner points: In the past few decades, modeling of contaminant transport in groundwater systems has seen tremendous applications.A number of models exist that independently simulate flow and solute transport in unsaturated and saturated zones.Recently, focus has been given on developing advanced coupled modeling approaches that require less inputs and run times. [ABSTRACT FROM AUTHOR]

Indigenous soil microbial communities play a pivotal role in the in situ bioremediation of contaminated sites. However, research on the distribution characteristics of microbial communities at various soil depths remains limited. In particular, there is little information on the assembly of microbial communities, especially those with degradation potential, in the vadose and saturated zones of hydrocarbon-contaminated sites. In this study, 18 soil samples were collected from the vadose zone and saturated zone at a long-term hydrocarbon-contaminated site. The diversity, composition, and driving factors of assembly of the soil bacterial community were determined by high-throughput sequencing analysis. Species richness and diversity were significantly higher in the vadose zone soils than in the saturated zone soils. Significant differences in abundance at both the phylum and genus levels were observed between the two zones. Soil bacterial community assembly was driven by the combination of pollution stress and nutrients in the vadose zone but by nutrient limitations in the saturated zone. The abundance of dechlorinating bacteria was greater in the saturated zone soils than in the vadose zone soils. Compared with contaminant concentrations, nutrient levels had a more pronounced impact on the abundance of dechlorinating bacteria. In addition, the interactions among dechlorinating bacterial populations were stronger in the saturated zone soils than in the vadose zone soils. These findings underscore the importance of comprehensively understanding indigenous microbial communities, especially those with degradation potential, across different soil layers to devise specific, effective in situ bioremediation strategies for contaminated sites. [Display omitted] • Significant differences exist in soil bacterial communities between the vadose zone and saturated zone. • Limited nutrients are key driving factors for bacterial community assembly in the saturated zone • More abundant dechlorinating bacteria exist in the saturated zone soils than the vadose zone soils • Nutrient levels have a greater impact on dechlorinating bacteria than contaminants • Interactions among dechlorinating bacteria are stronger in the saturated zone compared to the vadose zone. [ABSTRACT FROM AUTHOR]

Rainfall is one of the most significant natural factors for inducing landslides. The shallow saturated zone formed in slopes during rainfall is an important factor in inducing shallow landslides. In this paper, the characteristics and influencing factors of the saturated zone in soil slopes, and the relationship between the soil surface permeability coefficient and the rainfall intensity are analyzed. In this research, the equation that characterizes the rainfall intensity by the soil saturation is built based on the Mualem-van Genuchten model, which mathematically describes the soil water characteristics of unsaturated soils. Using this model, the target saturation of the slope surface during rainfall can be determined accurately, with an average deviation of − 0.008. Based on the equations, the innovative critical curve model of the rainfall intensity−time required to form the shallow saturated zone is established and calculated. The influence of the soil material, slope angle, rainfall intensity and antecedent rainfall on the critical curve for the shallow saturated zone is analyzed. The results indicate that for slopes of 30°~40°, it is easy for the shallow saturated zone to form, and the previous rainfall after more than 16 days has little impact on the critical curve. Furthermore, an innovative landslide prediction model, based on the critical curve for the shallow saturated zone and I-D modeling, is proposed to provide benchmarks for the prediction-specific characteristics of deep or shallow landslides, which is verified by the case of the Madiwan landslide. [ABSTRACT FROM AUTHOR]

One of the global geohazard issues discuss among scientists is soil liquefaction phenomenon. The incidents occurred at Palu in September 2018 and Aceh in December 2004, triggered soil liquefaction phenomenon which lead severe damages and lives. The common research on the geohazard issue include geotechnical methods (SPT and CPT) and geophysical methods (MASW and seismic). This study was conducted at Meuraxa district (Banda Aceh) and Baitussalam district (Aceh Besar) to introduce the capability of Electrical Resistivity Tomography (ERT) to predict the soil liquefaction phenomenon. The 2-D resistivity data were process using res2dinv inversion software to produce resistivity inversion models which then correlated with published results. The study identified that the resistivity values of 0.1 - 10 Ω m i s a soil saturated zone which affected by seawater intrusion and concludes that the study areas predicted by ERT have a high potential of soil liquefaction phenomenon to be occurred. [ABSTRACT FROM AUTHOR]

A comprehensive subsurface monitoring program should include contaminant detectors in both the vadose and saturated zones. Vadose zone detectors can provide an early warning of an impending groundwater contamination problem, and also yield information relevant to placing groundwater monitoring wells. Moisture probes, gas monitoring wells, and pore-liquid samplers deployed in the vadose zone complement groundwater detection wells. The objective(s) of a monitoring program, spatial-scales, and hydrogeology are important considerations for designing subsurface monitoring networks. Often, these networks are used to detect potential releases or characterize existing contamination beneath land-based waste storage facilities. A case study in Santa Barbara, California, U.S.A., illustrates the utility of vadose zone monitoring in characterizing a gasoline contamination problem and guiding the placement of groundwater monitoring wells.

Greywater is an alternative water resource, having many favourable characteristics over stormwater or wastewater. In particular, it can be supplied consistently and generated close to desirable end-use applications. Although greywater is considered to contain a low level of contamination, treatment is still required before the end-use, and passive filtration such as biofiltration became a popular option due to its low maintenance and low energy consumption. To this end, a laboratory experiment was conducted with synthetic greywater over 12 months to test the influence of operational characteristics and design factors on pathogen removal from greywater. The role of plants types, saturated zone, and the absence/inclusion of antimicrobial material were tested in a total of 80 biofilter columns. The results showed that the biofilters obtained a median E. coli logarithmic removal of 3.0 across the tested configurations and produced quality of water that meets indoor non-potable use standard (NRMMC, 2006). Further, the infiltration rate and event size were found to significantly influence E. coli removal in greywater biofilters (ANOVA, p < 0.05). The presence of antimicrobial media also significantly improved E. coli removal (up to 1.4 log) compared to non-amended media (ANOVA, p < 0.05). Vegetation also played a significant role in removing E. coli (ANOVA < 0.05). This study successfully suggested the great potential for the application of biofilters to greywater treatment and identified key design factors for consideration prior to implementation. [ABSTRACT FROM AUTHOR]

Abstract A laboratory-scale vertical flow constructed wetland system was designed and monitored to compare nitrogen removal rates and pathways from both saturated and unsaturated zones under a hydraulic loading rate and influent total nitrogen concentration of 1.5 m3/m2.d and 508 mg/L respectively. Weekly measurements of the concentrations of nitrogen compounds, chemical oxygen demand, temperature, dissolved oxygen, oxidation-reduction potential, and hydrogen ion concentration were taken throughout the study. At the end of the experiments, PCR analysis of 16S rRNA gene sequencing was performed to identify microbial communities in the unsaturated and saturated parts of the system. The nitrogen compounds were removed from the system after 182 days, with similar total nitrogen removal efficiencies (94% and 93%) for the unsaturated and saturated zones respectively. Heterotrophic nitrification/aerobic denitrification was the major pathway responsible for the removal of nitrogen compounds. Adsorption into the gravel bed also contributed to ammonium removal. Proteobacteria were the dominant bacterial strains involved in nitrogen transformation and accounted for 80% of the total bacteria in the unsaturated zone and 60% in the saturated zone. With little difference in the concentration removal efficiencies of the unsaturated and saturated zones, a more effective design would be an entirely saturated wetland as the total mass removal of nitrogen depends on the water volume stored, which at full saturation in this design was seven times greater per unit wetland volume than the unsaturated zone. Highlights • Nitrogen decay is similar in unsaturated and saturated zones of the wetland. • Nitrate is lost by heterotrophic nitrification and aerobic denitrification. • Nitrite is also lost by heterotrophic nitrification and aerobic denitrification. • Ammonium loss occurs by heterotrophic nitrification and biofilm adsorption. • Saturated water content is seven times greater than the unsaturated water content. [ABSTRACT FROM AUTHOR]

Abstract: Rivers originating in the granitic highlands of seasonally dry central Argentina provide water to 2 million people. These highlands comprise a complex landscape where a matrix of outcropping rock hosts vegetated patches that vary in response to long‐term grazing and fire. We characterized water storage dynamics across 20 sites representing 6 vegetation‐soil conditions with similar mid‐upslope positions in the landscape. We measured temporal and spatial variability of water inputs (rain and fog) and water stored at the unsaturated and saturated zones. We found that rainfall was highly seasonal, but fog occurred year‐round, likely representing an extra water source in areas with complex vegetation structure. Moreover, fog seems to regulate evapotranspiration/topsoil water dynamics. Water was stored in the saturated zone only during the rainy season. Piezometric response to rainfall was rapid but transient (dropping an average 15 cm/day), possibly buffering peak stormflows, reducing sediment yield, and delivering subsurface water downslope for potential storing throughout the year. Spatially, a reduction in soil depth (from 100 up to 9 cm) and vegetation structure (from woodlands to stonelands), with a degradation of topsoil conditions for infiltration were accompanied by a decline in water storage at the unsaturated (from 32% up to 14%) and saturated (from 46.3 up to 0 cm) zones. Taken together, our results support the infiltration trade‐off hypothesis, which states that vegetation structure benefits fog interception, soil properties that enhance water infiltration, subsurface flow paths, and storage. Long‐term disturbances have likely triggered a degradation of the hydrological function of seasonal highlands in central Argentina. [ABSTRACT FROM AUTHOR]

The introduction of a saturated zone (SZ) has been recommended to address the issue of nitrogen removal fluctuation in the bioretention system, which is one of the most versatile low-impact development facilities for urban stormwater management. Nine experimental columns were used to characterize the nitrogen concentration variations over the outflow during wetting periods and in SZ during the antecedent drying periods (ADPs), as well as compare removal efficiencies of various nitrogen species in systems with different SZ depths under alternate drying and wetting conditions. Results indicated that NO3--N concentrations in the outflow showed quasi-logistic curve-shaped variations over time: being low (<0.5 mg/L) in the early process, sharply increasing thereafter, and finally flattening around 3.0 mg/L with NO3- leaching; NH4+-N and organic nitrogen (ON) concentrations were consistently low around 0.5 mg/L and 1.8 mg/L, respectively during the wetting periods. NH4+ removal efficiency in bioretention systems was consistently high around 80%, not varying with the increasing SZ depth; ON removal efficiency had a slight rise from 57% to 84% and NO3- removal efficiency was significantly enhanced from -23% to 62% with the SZ depth increasing from 0 to 600 mm. Deeper SZ could store more runoff and promote more denitrification of NO3- and mineralization of ON during the ADPs, providing more "old" water with low NO3- and ON concentrations for water exchange with "new" inflow of higher NO3- and ON concentrations during the wetting periods. The total nitrogen (TN) removal, a combined result of the instantaneous removal through adsorption and retention in the upper soil layer during the wetting periods and the gradual removal via denitrification and mineralization in SZ during the ADPs, was also improved by increasing the SZ depth; TN removal efficiency was elevated from 35% to 73% when the SZ depth increased from zero to 600 mm. [ABSTRACT FROM AUTHOR]

Plants play a critical role in the nutrient removal performance of stormwater biofilters. However, the influence of biofilter design on plant growth and subsequent implications for treatment performance are not well understood. A 12 month, laboratory-scale biofilter column experiment was conducted to investigate the response of Carex appressa to variations in biofilter design and implications for nutrient removal performance. Plant growth in Skye sand, a natural iron-coated sand with a strong capacity to immobilize phosphorus, was evaluated against a typical loamy sand filter media in biofilters with and without a saturated zone. Plant biomass correlated strongly with nutrient removal and was significantly greater in biofilters with a saturated zone, suggesting that inclusion of a saturated zone facilitates nutrient uptake. In the presence of a saturated zone, plants grown in Skye sand had a significantly higher specific root length, surface area and volume than plants grown in loamy sand, illustrating C. appressa ’ s ability to adapt root morphology to maintain growth under nutrient limited conditions. These root traits also correlated strongly with nutrient removal, suggesting that use of Skye sand in biofilters rather than loamy sand would be advantageous for nutrient removal. However, root adaptations, in particular increased etiolation, can make plants vulnerable to stressful environments (e.g. prolonged drying). Therefore, it is critical that a saturated zone be included in stormwater biofilters to increase growth and protect against drying. [ABSTRACT FROM AUTHOR]

Stormwater runoff greatly contributes to surface water pollution and deterioration of aquatic environment in urban areas. Biofilter, as low impact development (LID) technology, has been widely applied in controlling urban runoff pollution in recent years. A multi-layered biofilter with a saturated zone was employed in this study to test its removal efficiency of pollutants and the effect of saturation time on its performance with the real road runoff. Two groups of columns were built with different vegetations ( Zoysia matrella , ZM and a combination of Iris pseudacorus and Z. matrella , IZ). During a 2.5-month duration, five times of runoff dosing trials with collected stormwater were conducted at a load of 20–25 L day −1 . All filter systems had effective retention of particulate matters, with the turbidity removals of over 95%. The IZ group performed more efficiently than ZM systems in the removal of total phosphorus (TP), ammonia (NH 4 -N), nitrate (NO 3 -N) and turbidity. The mean removal of total nitrogen (TN) and TP was 49.8 ± 23.8% and 74.8 ± 9.9% in IZ group, and 42.6 ± 22.0% and 66.4 ± 12.2% in ZM group. Saturation time had significant effect on the removal of TN, TP and turbidity, whose concentrations declined with the saturation duration. The performances of biofilters were dynamic, as a function of media depth and retention time. The configuration of saturated zone and optimized depth of media layers (at least 0.75 m) can provide a favorable condition for nitrogen removal under random inflow condition. [ABSTRACT FROM AUTHOR]

Biochar has demonstrated promising performance as an amendment to biofilter soil media in removing fecal indicator bacteria (FIB) from simulated stormwater. However, there is no study that investigates its efficacy in treating natural stormwater runoff. Additional information, including the effects of antecedent dry period, microbial biofilm, and presence of a saturation zone on the performance of biochar-augmented biofilters are needed to inform their field implementation. This study uses laboratory column experiments to monitor FIB (enterococci and Escherichia coli ) and nutrient removal capacity of biochar-amended biofilters for 140 days using natural stormwater. Our study also investigates the effects of antecedent dry days (ADD) and the presence of a saturation zone (SZ) on the performance of lab-scale biochar-amended biofilters. The results suggest insignificant influence of the ADD and SZ on FIB removal performance, however biofilters with a SZ perform significantly better in removing nitrate-nitrogen compared to those without a SZ. In addition, it appears that the presence of biofilm augments nutrient removal capacity but reduces FIB removal capacity. Our observations indicate that biochar-amended biofilters are able to treat (to comply with recreational water quality standard for FIB) urban stormwater runoff for the duration of the experiment. Nitrate- and ammonium-nitrogen removal in the biologically aged biofilters is found to be 50–60% while the total dissolved phosphorus and the organic nitrogen removal is 20–30%. Our results inform full-scale design of biochar-amended biofilters in order to meet the total maximum daily load (TMDL) and municipal separate storm sewer system (MS4) permitting requirement for FIB and nutrients. [ABSTRACT FROM AUTHOR]

In the paper, we assess the mobility of copper and zinc in two sections, Granica and Kampinos, of the glacial and post-glacial sediments in the Kampinos National Park (Poland) and its buffer zone. The Granica section is practically devoid of carbonates and clay fraction, and the environment is markedly acidic. The other section, Kampinos, is characterized by a considerable content of carbonates (up to 20%) and clay fraction (up to 34%) with high sorption potential. The bonds of Zn and Cu cations with the solid phase occur mainly through adsorption and formation of salts, and through creation of chelated and complex connections. We found that, while sorption of Cu within the shallow groundwater zone under typical natural environment equilibrium conditions depends mainly on the content of the sorbing solid phase (i.e. organic matter and metal oxides and hydroxides), sorption of Zn within the shallow groundwater zone depends mainly on the fluctuating acidity and ionic strength of the groundwater, and to a lesser extent on the content and nature of the solid phase. The sorption process within the Kampinos section occurred predominantly on to three sorption media: clay fraction, organic matter and amorphous forms of Fe, Al and Mn. In the Granica section, because of the absence of clay fraction, sorption of the two metals occurred mainly with the organic matter and amorphous forms of Fe, Al and Mn. In addition, the sorption potential of the two metals in this section was low, because of the acidic pH of the environment, i.e. high availability of exchangeable hydrogen in the sorption complex. The concentrations of copper and zinc in the soil (S) were examined using both: the Lindsay and Norvell's and aqua regia methods. The methods of variable extraction capacity yielded very similar results for copper. In addition, the study found that the amounts of extracted zinc depended on the type of solution. The highest concentrations of zinc and copper were observed using the extraction with aqua regia. The results from determining zinc and copper concentrations (S) in the soil and rocks and the results of hydrochemical modelling show that the mobility of these two elements is highly limited by sorption processes; moreover, zinc is less effectively adsorbed than copper in these sections. [ABSTRACT FROM AUTHOR]

In the management of radionuclide release in the environment, the unsaturated zone could be a natural barrier to delay or to stop the radionuclide migration through the environment and to protect the groundwater from radiological risks. Thus, a suitable scientific evaluation of any radionuclide transport problems related to groundwater may to take into account the processes affecting flow through the unsaturated zone. In this work, an approach that involves the interactions between unsaturated zone and saturated zone both from hydrogeological and radionuclide transport point of view is proposed. This approach was tested developing a case study on an Italian nuclear site. The behavior of unsaturated zone as protective barrier for the groundwater was highlighted and identified as a fundamental aspect in the development of environmental analysis concerning the radionuclide transport into the environment. Promising results were found to improve the design of a radiological monitoring network. [ABSTRACT FROM AUTHOR]

Nitrate water pollution, which is mainly caused by agricultural activities, remains an international problem. It can cause serious long-term environmental and human health issues due to nitrate time-lag in the groundwater system. However, the nitrate subsurface legacy issue has rarely been considered in environmental water management. We have developed a simple catchment-scale approach to investigate the impact of historical nitrate loading from agricultural land on the nitrate-concentration trends in sandstones, which represent major aquifers in the Eden Valley, UK. The model developed considers the spatio-temporal nitrate loading, low permeability superficial deposits, dual-porosity unsaturated zones, and nitrate dilution in aquifers. Monte Carlo simulations were undertaken to analyse parameter sensitivity and calibrate the model using observed datasets. Time series of annual average nitrate concentrations from 1925 to 2150 were generated for four aquifer zones in the study area. The results show that the nitrate concentrations in ‘St Bees Sandstones’, ‘silicified Penrith Sandstones’, and ‘non-silicified Penrith Sandstones’ keep rising or stay high before declining to stable levels, whilst that in ‘interbedded Brockram Penrith Sandstones’ will level off after a slight decrease. This study can help policymakers better understand local nitrate-legacy issues. It also provides a framework for informing the long-term impact and timescale of different scenarios introduced to deliver water-quality compliance. This model requires relatively modest parameterisation and is readily transferable to other areas. [ABSTRACT FROM AUTHOR]