Numerical modelling on fate and transport of coupled adsorption and biodegradation of pesticides in an unsaturated porous medium
TL;DR: In this article, a one-dimensional numerical model is developed to simulate the transport of pesticides in an unsaturated porous medium, considering the effect of adsorption and microbial degradation with inhibition in addition to conventional advective and dispersive transport.
Abstract: The vertical transport of pesticides from a surface application through an unsaturated porous medium system is of major concern to assess the vulnerability of groundwater contamination. In order to better understand the transport of pesticides in the groundwater, it is essential to understand the flow and predict the pesticide concentration in the unsaturated zone. A one-dimensional numerical model is developed to simulate the transport of pesticides in an unsaturated porous medium, considering the effect of adsorption and microbial degradation with inhibition in addition to conventional advective and dispersive transport. The effect of unsaturated soil parameters on the water flow dynamics and the factors governing the pesticide transport in an unsaturated porous medium is also numerically investigated. The numerical results suggest that the adsorption and biodegradation is an important sink in contaminant removal. In addition, the microbial growth inhibition due to pesticide restricts the potent...
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TL;DR: In this article, the authors evaluated the influence of OAs, mixed waste compost, and dried goat organic manure on the sorption of organophosphates, dichlorvos, and chlorpyrifos.
Abstract: Soil organic carbon enrichment by addition of organic amendments (OAs) is a common agricultural and gardening practice. Such amendments can cause ambiguous environmental effects; it could enhance the sorption of pesticides by increasing soil organic carbon content, and on the contrary, dissolved organic matter (DOM) from OAs could facilitate their leaching. This study evaluated the influence of OAs, mixed waste compost, and dried goat organic manure on the sorption of organophosphates, dichlorvos, and chlorpyrifos. Soil (15 cm depth) was collected from an agricultural field and stored. Dissolved organic matter (DOM) extracted from the amendments and the amended soils was characterized by fluorescence spectroscopy and Fourier transform infrared spectroscopy (FT-IR). Initially, studies were carried out to evaluate the effect of DOM from organic amendments (OA-DOM) and dissolved humic acids (HAs) as model DOM on the sorption of selected pesticides. In the later part, OAs (2.5 and 5% w/w) were added to the soil, and sorption experiments were carried out using amended soil to understand the combined effects of insoluble and soluble organic carbon fraction. As dichlorvos sorption was found to be very low, desorption experiments were conducted only for chlorpyrifos using 0.01 M CaCl2 and DOM solutions. The spectroscopic characterization of OA-DOM revealed that it mainly contained large amounts of highly humified and aromatic material. OA-DOM and HAs had a similar effect on pesticide sorption leading to a slight but not significant increase in dichlorvos sorption while a substantial reduction in chlorpyrifos sorption was observed. Surface tension analysis highlighted that OA-DOM and HAs might have caused greater solubilization of chlorpyrifos, thus reducing sorption. Further, it also promoted greater desorption of adsorbed chlorpyrifos. These results seem to be related to the humified and aromatic nature of OA-DOM and HAs, determining the interactions between hydrophobic chlorpyrifos and DOM. On the contrary, the addition of OAs to soil promoted greater chlorpyrifos and dichlorvos sorption, but a clear correlation between increase in soil organic carbon and pesticide sorption could not be established. The study highlighted that the net effect of OA application was an increase in pesticide sorption that depended on the nature of DOM and pesticide properties. The interactions of hydrophobic chlorpyrifos with DOM can lead to a significant reduction in sorption to such an extent that the sorption in the presence of substantial DOM concentration can be less than the sorption without it.
19 citations
TL;DR: The results indicated that the enriched microbes are promising candidates for insitu bioremediation of contaminated waters and soils.
Abstract: The study focuses on the biodegradation kinetics of organophosphate pesticides (OPs), chlorpyrifos and dichlorvos by enriched cultures and its application in pesticide transport models. Pseudomonas...
14 citations
Cites methods from "Numerical modelling on fate and tra..."
...More information about the model were explained in detailed in our previous works (Gaonkar, Suresh Kumar, and Nambi 2016; Gaonkar, Kumar, and Nambi 2016)....
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...…from this study can be used as input parameters for subsurface pesticide transport model developed in our earlier works to understand the subsurface fate and transport of these pesticides after soil surface application (Gaonkar, Kumar, and Nambi 2016; Gaonkar, Suresh Kumar, and Nambi 2016)....
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TL;DR: Under future climate change scenarios, where more intense precipitation is likely to result in higher infiltration rates and increased soil moisture, the potential for groundwater pollution from atrazine may be reduced, especially in areas with a long history ofAtrazine application to soil.
Abstract: The objective of this study was to assess the persistence and transport of atrazine at high infiltration rates expected from higher intensity precipitation associated with climate change scenarios in the midwestern U.S. The transport and transformation of atrazine was monitored in column experiments at high infiltration rates (64–119 mm d−1) associated with increased precipitation intensity. The optimum linear sorption and the lumped Monod biokinetic parameters were determined by inverting observed break-through curves (BTCs) using the advection–dispersion–sorption–degradation model. Batch microcosm studies were also conducted to examine the effect of moisture content (5%, 15% and 25%) on atrazine degradation and support the column results. BTCs from both soil types with continuous atrazine input showed a characteristic pattern of a pulse input i.e. lag phase prior to rapid atrazine degradation. The rate of atrazine leaching at higher infiltration rates was not fast enough to counteract the effect of enhanced degradation. Higher infiltration rates enriched the distribution of hydroxyatrazine in the soil profile for sandy loam, but their effect was minimal in loam soil. The pattern of degradation obtained in batch microcosms agreed with the column results. In both soils, mean half-life of atrazine was lower (4–8 days) at high soil moisture contents. Under future climate change scenarios, where more intense precipitation is likely to result in higher infiltration rates and increased soil moisture, the potential for groundwater pollution from atrazine may be reduced, especially in areas with a long history of atrazine application to soil.
14 citations
TL;DR: In this paper, a coupled sorption-biodegradation sink term including advanced biokinetics and inhibition effect for nitrogen movement in saturated soil was proposed for better prediction of the existing advection-dispersion-reactive transport model by a coupled SBS.
10 citations
TL;DR: In this article, a simulation study is conducted based on the one-dimensional numerical model considering Richard's equation for unsaturated water flow and solute transport which takes into account the effect of both adsorption and biodegradation with inhibitory effect to understand pesticide transport in an unsaturated porous medium.
Abstract: The pesticides applied on the soil surface can be transported vertically downwards through the unsaturated porous system and lead to groundwater contamination. Proper agricultural management practices such as selection of appropriate irrigation techniques, choosing proper irrigation rates, and application of optimum pesticide dosages are necessary to prevent leaching of pesticides to greater depths thus preventing groundwater contamination. A simulation study is conducted based on the one-dimensional numerical model considering Richard’s equation for unsaturated water flow and solute transport which takes into account the effect of both adsorption and biodegradation with inhibitory effect to understand pesticide transport in an unsaturated porous medium. The study addresses the influence of irrigation rate, type of irrigation, and pesticide dosage on soil moisture and pesticide concentration distribution. The numerical results suggest that higher water application rates can carry the pesticides to greater depths. Pulsed irrigation can slightly reduce water losses through the root zone when compared to continuous irrigation. The comparison of the wetting patterns and the pesticide distribution obtained in continuous and pulsed irrigation helps to decide the use of a particular irrigation strategy in order to achieve suitable goals. In addition, the results from this study bring out better understanding of the effect of pesticide concentration and dosage on the resultant pesticide distribution in the unsaturated zone and the pesticide potential to cause groundwater contamination. The better analysis of outputs from this study can help in improving and designing better agricultural management strategies, carrying out risk assessment and bioremediation studies.
6 citations
Additional excerpts
...(9) (Park and Bae 2009; Gaonkar et al. 2016). l ¼ lmax Cp Kcp þ Cp Ki Ki þ Cp ð9Þ In Eq....
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References
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TL;DR: This paper presents numerical and parameter estimation models for the analysis of virus transport and the identification of transport parameters in the unsaturated zone and indicates that the numerical model’s predictions are in excellent agreement with the analytical predictions.
Abstract: This paper presents numerical and parameter estimation models for the analysis of virus transport and the identification of transport parameters in the unsaturated zone. The numerical model couples a mass conservative fully implicit finite difference model simulating moisture flow in the unsaturated zone with the hybrid finite volume model for virus transport. The accuracy of the numerical scheme is tested for both advection- and dispersion-dominated transport. The comparison of the numerical model with the analytical solution indicates that the numerical model’s predictions are in excellent agreement with the analytical predictions. The parameter estimation is formulated as a nonlinear least-squares minimization problem in which the parameters are estimated by minimizing the deviations between the model-predicted and experimentally observed virus concentrations. A parameter estimation procedure is developed by coupling the numerical model simulating one-dimensional virus transport in the unsatura...
12 citations
"Numerical modelling on fate and tra..." refers methods in this paper
...The model with the first-order reaction term was validated using the data from Ojha et al. (2012) (Figure 3(c) and (d))....
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...…by ogata and Banks (1961) (b) verification at Pe = 100 with analytical solution by ogata and Banks (1961) (c) validation at Pe = 1 with published data from ojha et al. (2012) (d) validation at Pe = 100 with published data from ojha et al. (2012) (refer Table 3 for details). water content with more…...
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...…(b) verification at Pe = 100 with analytical solution by ogata and Banks (1961) (c) validation at Pe = 1 with published data from ojha et al. (2012) (d) validation at Pe = 100 with published data from ojha et al. (2012) (refer Table 3 for details). water content with more negative pressure head....
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TL;DR: A model for describing rates of pesticide-substrate biodegradation in soil has been modified by incorporating the effect of toxicity of pesticides on microorganisms, and it is found that Ks is insensitive to loss of efficacy (LE 1).
12 citations
"Numerical modelling on fate and tra..." refers methods in this paper
...China et al. (2004) used a simulation model to perform sensitivity analysis for biodegradation of pesticides in soil, but it was a theoretical study in which only the pesticide biodegradation, including the toxicity, was considered using Haldane kinetics and it did not include the transport in the…...
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TL;DR: A model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined, and manganese oxide (MnO2, which is present in the soil) and NO3−$_{3}^{-}$ (applied to enhance biodegradation) can be used as electron acceptors for anaerobic degradation.
Abstract: Transport and degradation of de-icing chemical (containing propylene glycol, PG) in the vadose zone were studied with a lysimeter experiment and a model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined. The lysimeter experiment indicated that aerobic as well as anaerobic degradation occurs in the vadose zone. Therefore, the model included both types of degradation, which was made possible by assuming advection-controlled (mobile) and diffusion-controlled (immobile) zones. In the mobile zone, oxygen can be transported by diffusion in the gas phase. The immobile zone is always water-saturated, and oxygen only diffuses slowly in the water phase. Therefore, the model is designed in a way that the redox potential can decrease when PG is degraded, and thus, anaerobic degradation can occur. In our model, manganese oxide (MnO2, which is present in the soil) and NO
$_{3}^{-}$
(applied to enhance biodegradation) can be used as electron acceptors for anaerobic degradation. The application of NO
$_{3}^{-}$
does not result in a lower leaching of PG nor in a slower depletion of MnO2. The thickness of the snowcover influences the leached fraction of PG, as with a high infiltration rate, transport is fast, there is less time for degradation and thus more PG will leach. The model showed that, in this soil, the effect of the water flow dominates over the effect of the degradation parameters on the leaching at a 1-m depth.
11 citations
"Numerical modelling on fate and tra..." refers methods in this paper
...In addition, numerical models have been developed and used to explain the water flow and contaminant behaviour in unsaturated porous systems (Berlin et al. 2013, 2015; Mohanasundaram et al. 2013; Pang et al. 2000; Schotanus et al. 2014)....
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17 Jan 2012-Journal of Environmental Science and Health Part B-pesticides Food Contaminants and Agricultural Wastes
TL;DR: Overall, the application of napropamide in the selected Malaysian soils would not pose a threat to the environment except in soil with low organic matter and clay content and high hydraulic conductivity, such as the Baging soil.
Abstract: This study was carried out to determine the sorption-desorption, degradation and leaching of napropamide in selected Malaysian soils. The sorption capacities of the selected Malaysian soils for napropamide were the following in descending order: Linau > Teringkap > Gunung Berinchang > Jambu > Rudua > Baging soil. The results indicate that napropamide degradation decreased with increasing soil sorption capacity. Napropamide was leached out earlier in the Baging soil than the other soils. Overall, the application of napropamide in the selected Malaysian soils would not pose a threat to the environment except in soil with low organic matter and clay content and high hydraulic conductivity, such as the Baging soil.
6 citations
"Numerical modelling on fate and tra..." refers background in this paper
...Several researchers have carried out studies on the subsurface fate and transport of pesticides along with various other organic and inorganic contaminants (French et al. 2001; Hmimou et al. 2014; Sadegh-Zadeh et al. 2012; Symons et al. 1988)....
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TL;DR: In this article, an attempt has been made to model fluid flow through a geological unit consisting of sandy-clay and clayey soil with significant macro pores, and the results suggest that the depths associated with soil moisture fronts are significantly different by applying a dual continuum approach with reference to the co...
Abstract: In this study, an attempt has been made to model fluid flow through a geological unit consisting of sandy-clay and clayey soil with significant macro pores. Considering such a geological formation using a single-continuum approach may not always be justified as the porosity and permeability contrast between the soil matrix and macro pore vary by several orders of magnitude and not by a scale factor. Under such circumstances, deducing the mean values of parameters such as porosity and permeability using conventional Representative Elementary Volume from a single continuum becomes nearly impossible. For this purpose, a numerical model has been developed to investigate the consequences of applying both equilibrium model or Single-Porosity Medium (SPM) and non-equilibrium model or Dual-Porosity Medium (DPM) approaches for the same soil types. Numerical results suggest that the depths associated with soil moisture fronts are significantly different by applying a dual continuum approach with reference to the co...
3 citations
"Numerical modelling on fate and tra..." refers methods in this paper
...In addition, numerical models have been developed and used to explain the water flow and contaminant behaviour in unsaturated porous systems (Berlin et al. 2013, 2015; Mohanasundaram et al. 2013; Pang et al. 2000; Schotanus et al. 2014)....
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