Pollutant Transport Model Research Articles

A two‐layer model for studying 2D dissolved pollutant runoff over impermeable surfaces

AbstractDissolved pollutants in stormwater are a main contributor to water pollution in urban environments. However, many existing transport models are semi‐empirical and only consider one‐dimensional flows, which limit their predictive capacity. Combining the shallow water and the advection–diffusion equations, a two‐dimensional physically based model is developed for dissolved pollutant transport by adopting the concept of a ‘control layer’. A series of laboratory experiments has been conducted to validate the proposed model, taking into account the effects of buildings and intermittent rainfalls. The predictions are found to be in good agreement with experimental observations, which supports the assumption that the depth of the control layer is constant. Based on the validated model, a parametric study is conducted, focusing on the characteristics of the pollutant distribution and transport rate over the depth. The hyetograph, including the intensity, duration and intermittency, of rainfall event has a significant influence on the pollutant transport rates. The depth of the control layer, rainfall intensity, surface roughness and area length are dominant factors that affect the dissolved pollutant transport. Finally, several perspectives of the new pollutant transport model are discussed. This study contributes to an in‐depth understanding of the dissolved pollutant transport processes on impermeable surfaces and urban stormwater management.

Numerical Modelling of Pollutant Transport in a Straight Narrow Channel using Upwind Finite Difference Method

River pollution has become an increasingly severe issue, resulting in the rapid depletion of freshwater resources. An accurate prediction of the transport of the pollutants is vital for effective mitigation measures. This paper presents the numerical modelling of pollutant transport in a straight narrow channel. The pollutant transport is modelled using an advection-diffusion equation. The equation is discretized using Finite Difference Method (FDM) with an explicit upwind scheme for the temporal term. The resulting system of simultaneous equations is solved using a direct method. The numerical model is validated against an existing analytical solution, and the results show good agreement between numerical prediction and analytical solution. The validated numerical model is applied to different cases of pollutant release mechanisms involving continuous and instantaneous pollutant releases. In both cases, the numerical model can capture the physics of the problem and able to provide valuable information on the time and spatial evolution of pollutant concentration. The model is extendable to higher dimension owing to its simplicity of discretization.

A hybrid first-order and WENO scheme for the high-resolution and computationally efficient modeling of pollutant transport

To improve the modeling quality of pollutant transport in shallow waters, different reconstruction schemes have been proposed to better link the edge values to the centroid values of a pollutant concentration in finite-volume shallow water models: a scheme of higher (lower) order generally has a better (poorer) quantitative accuracy but lower (higher) computational efficiency. Here, a numerical comparative study of several classical schemes is first conducted under a variety of pollutant distribution conditions. The results reveal that, for the condition of relatively uniform pollutant distribution, the numerical accuracy of a lower-order scheme (such as the first-order scheme or the MUSCL scheme) may be similar to that of a higher-order scheme (such as the WENO scheme). The second-order derivative of the concentration, here termed the nonlinear indicator (NI), correlates well with the discrepancies between the numerical solutions and analytical solutions. A threshold value of approximately 10−7∼10−6 m-2 for the NI is identified, above which a higher-order scheme may be required. Based on this understanding, a hybrid first-order and WENO scheme is proposed. Numerical case studies show that the hybrid scheme can successfully combine the efficiency of the first-order scheme with the high accuracy of the WENO scheme for pollutant modeling.

Multiscale Modeling of Convection and Pollutant Transport Associated with Volcanic Eruption and Lava Flow: Application to the April 2007 Eruption of the Piton de la Fournaise (Reunion Island)

Volcanic eruptions can cause damage to land and people living nearby, generate high concentrations of toxic gases, and also create large plumes that limit observations and the performance of forecasting models that rely on these observations. This study investigates the use of micro- to meso-scale simulation to represent and predict the convection, transport, and deposit of volcanic pollutants. The case under study is the 2007 eruption of the Piton de la Fournaise, simulated using a high-resolution, coupled lava/atmospheric approach (derived from wildfire/atmosphere coupled code) to account for the strong, localized heat and gaseous fluxes occurring near the vent, over the lava flow, and at the lava–sea interface. Higher resolution requires fluxes over the lava flow to be explicitly simulated to account for the induced convection over the flow, local mixing, and dilution. Comparisons with air quality values at local stations show that the simulation is in good agreement with observations in terms of sulfur concentration and dynamics, and performs better than lower resolution simulation with parameterized surface fluxes. In particular, the explicit representation of the thermal flows associated with lava allows the associated thermal breezes to be represented. This local modification of the wind flow strongly impacts the organization of the volcanic convection (injection height) and the regional transport of the sulfur dioxide emitted at the vent. These results show that explicitly solving volcanic activity/atmosphere complex interactions provides realistic forecasts of induced pollution.

The effect of neglecting spatial variations of the parameters in pollutant transport modeling in rivers

For many environmental projects and plans, it is necessary to model pollutant transport in rivers. Pollutant transport modeling is a complex phenomenon with multiple factors affecting it. The basic governing equation describing pollutant transport is advection–dispersion equation. There are two main parameters in this equation, namely, dispersion coefficient and flow velocity. In non-uniform flow regimes, these parameters are both spatially variable, therefore, solution of the advection–dispersion equation usually accomplished using numerical methods. Spatial variability of these parameters makes it hard to determine them, particularly for dispersion coefficient in which determining it for non-uniform flows using the corresponding formulas or calibration is an uncertain and challenging task. In this study, based on non-dimensionalized transport equation and the Monte Carlo simulation technique, a methodology is presented for evaluating the effects of spatial variability of the parameters on concentration distribution in rivers. The results imply that for many practical cases of pollutant transport modeling in rivers, spatial variations of flow velocity and dispersion coefficient can be neglected with a reasonable error. Consequently, for these cases, constant-coefficient pollutant transport equation can be applied instead of the variable-coefficient one, hence, simple analytical solutions can be employed rather than complicated numerical models. The proposed approach was applied for a real case study, successfully. It is emphasized that the results of the study are fairly general and can provide insight and simplification in different stages of pollutant transport modeling in rivers.

Another Proof of Existence of Global Weak Solutions to 1D Pollutant Transport Model

This paper is devoted to the study of pollutant transport model by water in dimension one. The model studied extend the
 results obtained in ( Roamba, Zabsonré & Zongo, 2017) . However, our model does not take into account cold pressure
 term and the quadratic friction term as in (Roamba, Zabsonré & Zongo, 2017) which are considered regularizing terms to
 show the existence of global weak solutions of your model. Without these regularizing terms, we show the existence of
 global weak solutions in time with a periodic domain.

A least squares method for identification of unknown groundwater pollution source

Abstract The identification of unknown groundwater pollution sources is one of the most important premises in groundwater pollution prevention and remediation. In this paper, an exploratory application of a least squares method to identify the unknown groundwater pollution source is conducted. Supported by a small amount of observation data and the analytical solutions of the pollutant transport model, the initial concentration, the leakage location and the pollutant mass are identified by using the least squares method under a sand tank experiment and a gas station area. In the sand tank experiment, it is found that the fitting errors of three cross-sections are within 6%. In the gas station area, it is found that the results are nearly consistent with the site investigation information. The results indicate that the least squares method has considerable application values in the identification of groundwater pollution sources.

Quantifying and predicting ecological and human health risks for binary heavy metal pollution accidents at the watershed scale using Bayesian Networks

The accidental leakage of industrial wastewater containing heavy metals from enterprises poses great risks to resident health, social instability, and ecological safety. During 2005–2018, heavy metal mixed pollution accidents comprised approximately 33% of the major environmental ones in China. A Bayesian Networks-based probabilistic approach is developed to quantitatively predict ecological and human health risks for heavy metal mixed pollution accidents at the watershed scale. To estimate the probability distributions of joint ecological exposure once a heavy metal mixed pollution accident occurs, a Copula-based joint exposure calculation method, comprised of a hydro-dynamic model, emergent heavy metal pollution transport model, and the Copula functions, is embedded. This approach was applied to the risk assessment of acute Cr6+-Hg2+ mixed pollution accidents at 76 electroplating enterprises in 24 risk sub-watersheds of the Dongjiang River downstream watershed. The results indicated that nine sub-watersheds created high ecological risks, while only five created high human health risks. In addition, the ecological and human health risk levels were highest in the tributary (the Xizhijiang River), while the ecological risk was more critical in the river network, and the human health risk was more serious in the mainstream of the Dongjiang River. The quantitative risk assessment provides a substantial support to incident prevention and control, risk management, as well as regulatory decision making for electroplating enterprises.

Solar radiometer sensing of multi-year aerosol features over a tropical urban station: direct-Sun and inversion products

Abstract. The AErosol RObotic NETwork (AERONET) is the most developed ground-based network for aerosol remote sensing and has been playing a significant role not only in monitoring air quality for protecting human health but also in assessing the radiative budget of our planet Earth. In this paper, we report the direct-Sun and inversion products, comprising of spectral variation of aerosol optical depth (AOD), associated Ångström exponent (AE), fine- and coarse-mode aerosol fractions, aerosol size distribution (ASD), refractive index (RI), asymmetry parameter (AP), single scattering albedo (SSA), aerosol radiative forcing (ARF) and columnar concentration of gas constituents such as water vapor (H2O), obtained from a Cimel Sun–sky radiometer, functioning in Pune, India, under the AERONET program since October 2004. These long-term measurements carried out from 2005 to 2015 could serve as an urban aerosol optical long-term average or climatology. The AOD long-term variations at all wavelengths, considered in the study, exhibited an increasing trend, implying year-to-year enhancement in aerosol loading. The mean seasonal variations in AOD from cloud-free days indicated greater values during the monsoon season, revealing dominance of hygroscopic aerosol particles over the station. Contribution by different aerosol types to AOD has also been deduced and discussed, and dominance of a mixed type of aerosols (44.85 %) found, followed by combination of biomass burning and urban industrial aerosols (22.57 %) compared to other types of aerosols during the study period. The long-term datasets, derived aerosol and trace gas products play a significant role in understanding aerosol climate forcing, trends and evaluation of regional air pollution and validation of aerosol transport models over the study region.

Coastal pollutant transport modeling using smoothed particle hydrodynamics with diffusive flux

The Smoothed Particle Hydrodynamics (SPH) method is used in this paper to simulate the transport process of coastal pollutant by solving the two-dimensional (2D) depth averaged advection-diffusion equation in Lagrangian framework. To avoid directly discretizing the second-order derivatives, the diffusion terms are decomposed into two first-order derivatives by introducing the diffusive flux. To verify the proposed Lagrangian particle model, numerical experiments on four typical tests are performed, including the discontinuity, pure advection, grid anisotropy and large deforming flow. The high-resolution Total Variation Diminishing (TVD) scheme - the modified TVD Lax–Friedrichs method with Superbee limiter (MTVDLF-Superbee) - is also implemented for detailed comparison. The simulation results indicated that the present SPH-based model has better performance than MTVDLF-Superbee. In addition, the stability, convergence and efficiency of the proposed model are numerically analyzed. The Lagrangian particle model with diffusive flux gives satisfactory results with big time step and hence allows large Courant number, guaranteeing the computational efficiency.

Analysis of assimilation capacity for conservation of water quality: controllable discharges of pollutants

Protection of water quality from the hazards of industrial, agricultural, urban, and other sources of pollutants has been a big concern for water resources managers in recent decades. Sources of pollutants are often classified into different large categories, which can be predicted by modeling. In this investigation, a river-reservoir system with the controllable pollution source was chosen and a one-dimensional pollutant transport model was considered to calculate the assimilation capacity (AC) of the river. All of the modeling procedures were processed and accomplished with the analytical solution and also by numerical methods, QUICK (quadratic upwind differencing) approach and SEF (symmetric exponential function) method, by simulating in MATLAB. Results for symmetrical pollution entrance demonstrate that in the domain of Cs (allowable concentration) from 0.13 to 0.71 mg/l, the amount of $$ \overline{{\mathrm{c}}_{\mathrm{a}}} $$ (mean area of unallowable concentration) is in the range of 0.28–0.68, 0.3–0.63, and 0.63–0.56 mg/l for analytical, SEF, and QUICK methods, respectively. Therefore, the amounts of $$ \overline{{\mathrm{c}}_{\mathrm{a}}} $$ by SEF acquire more similarity to analytical method than QUICK. A novel general relationship is determined to calculate AC of the river by applying nonlinear regression to the obtained data from SEF method and then verified with the measured values of nitrate concentration for Karun River in Iran. Statistical parameters, R2, RMSE, and MAE, for the proposed relationship were equal to 0.955, 0.186, and 0.065 in the modeling calibration and also were 0.912, 0.251, and 0.093 compared with the laboratory data, respectively.

Rainfall Runoff and Dissolved Pollutant Transport Processes Over Idealized Urban Catchments

Urban stormwater runoff is often considered as one of the most significant contributors to water pollution. Particulates are commonly regarded as the primary form of pollutant transport in the urban environment, but the contribution from the dissolved pollutants can also be significant. This study aims to investigate the dissolved pollutant transport process over urban catchments, especially the effects of buildings and spatial distribution of pollutants. The concept of “exchange layer” has been adopted and an equation has been proposed to describe the release process of dissolved pollutant from the exchange layer to the runoff water. A horizontal two-dimensional water flow and pollutant transport model has been developed for predicting dissolved pollutant runoff based on the shallow water assumptions and the advection-diffusion equation. A series of laboratory experiments have been conducted to verify the proposed model. It has been demonstrated that both the rainfall runoff and the pollutant runoff can be predicted accurately. Buildings slow down the runoff and pollutant transport processes, especially when buildings are staggered. The non-uniform distribution of pollutants over the catchment greatly influences the pollutant transport process over the catchment. This work provides insight into the effects of buildings and initial pollutant distribution on the dissolved pollutant transport phenomenon, which can help better design the pollution mitigation strategies.

Study of Fuel-Smoke Dynamics in a Prescribed Fire of Boreal Black Spruce Forest through Field-Deployable Micro Sensor Systems

Understanding the combustion dynamics of fuels, and the generation and propagation of smoke in a wildland fire, can inform short-range and long-range pollutant transport models, and help address and mitigate air quality concerns in communities. Smoldering smoke can cause health issues in nearby valley bottoms, and can create hazardous road conditions due to low-visibility. We studied near-field smoke dynamics in a prescribed fire of 3.4 hectares of land in a boreal black spruce forest in central Alberta. Smoke generated from the fire was monitored through a network of five field-deployable micro sensor systems. Sensors were placed within 500–1000 m of the fire area at various angles in downwind. Smoke generated from flaming and smoldering combustions showed distinct characteristics. The propagation rates of flaming and smoldering smoke, based on the fine particulate (PM2.5) component, were 0.8 and 0.2 m/s, respectively. The flaming smoke was characterized by sharp rise of PM2.5 in air with concentrations of up to 940 µg/m3, followed by an exponential decay with a half-life of ~10 min. Smoldering combustion related smoke contributed to PM2.5 concentrations above 1000 µg/m3 with slower decay half-life of ~18 min. PM2.5 emissions from the burn area during flaming and smoldering phases, integrated over the combustion duration of 2.5 h, were ~15 and ~16 kilograms, respectively, as estimated by our mass balance model.

Numerical Study of Hydrodynamics and Water Quality in Qinhuangdao Coastal Waters, China: Implication for Pollutant Loadings Management

Protecting coastal area marine environments from pollution is critical to ensure sustainable development. However, the hydrodynamic and water environmental characteristics of many coastal waters are poorly understood. Furthermore, the levels of pollutants loading into coastal waters are rarely quantified. In this study, a hydrodynamic and pollutant transport model (based on MIKE 21 modules) was established in Qinhuangdao coastal waters, China. The simulated hydrodynamics and water quality parameters were highly congruent with measured values, exhibiting error levels below 20%. In Qinhuangdao coastal waters, the seawater flows primarily from southwest to northeast along the coast, with velocities in the range 0–0.4 m/s and 0–0.3 m/s during flood and ebb tides, respectively. Results from this study indicated that these waters were characterized by a weak tidal current, with mean velocities varying in the range 0–0.5 m/s. The chemical oxygen demand (COD) concentration of the coastal waters was in the range 0.1–3.7 mg/L, and the COD pollutants were diffused approximately 3–10 km off the coastline. The water environment carrying capacity (WECC) at each point source was also calculated based on the response coefficients; further, WECC in Qinhuangdao coastal waters was calculated at 544.01 t/a and 1088.02 t/a under two Chinese water quality levels (levels I and II), respectively. The results provided specific valuable information for controlling pollutants from rivers into coastal waters and managing the Qinhuangdao coastal waters environment.

The Piecewise Parabolic Method for the Parameters Estimation in an Ocean Pollutant Transport Adjoint Model

In this paper, a higher-order and conservative Piecewise Parabolic interpolation is proposed to estimate key parameters of an ocean pollutant transport model. The Piecewise Parabolic interpolation quality is verified by groups of experiments. The results show that the Piecewise Parabolic Method (PPM) in independent point scheme (IPS) can realize better parameter estimation with fewer independent points.

Human exposure to polychlorinated biphenyls embodied in global fish trade

International food trade poses food safety risks through the collateral transport of contaminants that are harmful to human health. Persistent organic pollutants, such as the polychlorinated biphenyl (PCB) congener PCB-153, are consumed via fish intake traded globally, but the estimated daily intake and risk to human health are poorly understood. Using a food trade pathway model, a global-scale atmospheric persistent organic pollutant transport model and UN Global Comtrade data, high PCB exposure was identified in Western Europe. Marine fish exported from Europe to Sub-Saharan African countries account for 84% of PCB-153 consumer exposure. In contrast, European fish consumers face reduced exposure to PCB-153 by consuming marine fish imported from countries where PCB-153 concentrations are low. People consuming aquaculture-farmed salmon fed with marine ingredients from PCB-153-contaminated seawaters face a higher PCB exposure. Our findings demonstrate that global fish trade can exacerbate PCB-153 exposure in regions where environmental PCB-153 levels are low. This approach demonstrates how the exposure to harmful food contaminants distributed through global food trade can be predicted and quantified. Food safety is jeopardized by the global trade in contaminated foods. Huang et al. demonstrate how consumer exposure to the toxic chemical polychlorinated biphenyl-153 (PCB-153) can be modelled and identify regions with high consumer PCB-153 exposure resulting from imported fish consumption.

Study of pollution transport through the rivers using aggregated dead zone and hybrid cells in series models

This paper aims at studying the data-based mechanistic pollution transport models of the aggregated dead zone (ADZ) and hybrid cells in series (HCIS) models. For a better understanding of them, it was tried to connect their parameters to the physical parameters of the classical advection–dispersion (ADE) model. A series of experiments were conducted using the laboratory model of the gravel bed river, and the sodium chloride solution was chosen as a conservative tracer. A new analytical solution of HCIS model, including triple dispersion cells, was developed. Also, the theoretical temporal moment equations were derived and attempted to develop explicit relationships for both ADZ and HCIS parameters based on hydraulically and geometrically variables. Detailed descriptions of the Pe number and the skewness coefficients (CSK) were presented, and the theoretical limit of CSK was extracted. It was concluded that the range of (0.93–1.24) for CSK is acceptable, which confirms the finding of previous investigators. A sensitivity analysis was operated to find the importance of different variables in estimating model parameters. Finally, the theoretical breakthrough curves of ADZ and HCIS models were drawn and confirmed with experimental BTCs. Statistical goodness of fit parameters of RMSE, DC, and MAE was calculated as triple sets of (0.0158, 0.99, 21.58 ppm), (0.0188, 0.97, 27.16 ppm), and (0.105, 0.83, 78.84 ppm) for ADZ, HCIS, and ADE models, respectively, which showed the superiority of data-based models to the classical ADE model.

Development of Non-Point Source Hybrid Cells in Series Model for Reactive Pollutant Transport in Natural Rivers

Development of Non-Point Source Hybrid Cells in Series Model for Reactive Pollutant Transport in Natural Rivers

On the Construction of Approximate Solutions for the 1D Pollutant Transport Model

The purpose of this paper is to build sequences of suitably smooth approximate solutions to the 1D pollutant transport model that preserve the mathematical structure discovered in (Roamba, Zabsonré, Zongo, 2017). The stability arguments in this paper then apply to such sequences of approximate solutions, which leads to the global existence of weak solutions for this model. We show that when the Reynold number goes to infinity, we have always an existence of global weak solutions result for the corresponding model.

Unified Description of Diffusion Coefficients from Small to Large Molecules in Organic-Water Mixtures.

Diffusion coefficients in mixtures of organic molecules and water are needed for many applications, ranging from the environmental modeling of pollutant transport, air quality, and climate, to improving the stability of foods, biomolecules, and pharmaceutical agents for longer use and storage. The Stokes-Einstein relation has been successful for predicting diffusion coefficients of large molecules in organic-water mixtures from viscosity, yet it routinely underpredicts, by orders of magnitude, the diffusion coefficients of small molecules in organic-water mixtures. Herein, a unified description of diffusion coefficients of large and small molecules in organic-water mixtures, based on the fractional Stokes-Einstein relation, is presented. A fractional Stokes-Einstein relation is able to describe 98% of the observed diffusion coefficients from small to large molecules, roughly within the uncertainties of the measurements. The data set used in the analysis includes a wide range of radii of diffusing molecules, viscosities, and intermolecular interactions. As a case study, we show that the degradation of polycyclic aromatic hydrocarbons (PAHs) by O3 within organic-water particles in the planetary boundary layer is relatively short (≲1 day) when the viscosity of the particle is ≲102 Pa s. We also show that the degradation times predicted using the Stokes-Einstein relation and the fractional Stokes-Einstein relation can differ by up to a factor of 10 in this region of the atmosphere.