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...
Citations
More filters
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)....
[...]
...…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)....
[...]
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....
[...]
References
More filters
01 Jan 1961
TL;DR: In this paper, a more direct method is presented for solving the differential equation governing the process of dispersion in a semi-infinite medium having a plane source at z = 0.
Abstract: Published papers indicate that most investigators use the coordinate transformation (x ut) in order to solve the equation tor dispersion of a moving fluid in porous media. Further, the boundary conditions O=0 at x=«> and 0=00 at x= «> for Z>0 are used, which results in a symmetrical concentration distribution. This paper presents a solution of the differential equation that avoids this transformation, thus giving rise to an asymmetrical concentration distribution. It is then shown that this solution approaches that given by symmetrical boundary conditions, provided the dispersion coefficient D is small and the region near the source is not considered. INTRODUCTION In recent years considerable interest and attention have been directed to dispersion phenomena in flow through porous media. Scheidegger (1954), deJong (1958), and Day (1956) have presented statistical means to establish the concentration distribution and the dispersion coefficient. A more direct method is presented here for solving the differential equation governing the process of dispersion. It is assumed that the porous medium is homogeneous and isotropic and that no mass transfer occurs between the solid and liquid phases. It is assumed also that the solute transport, across any fixed plane, due to microscopic velocity variations in the flow tubes, may be quantitatively expressed as the product of a dispersion coefficient and the concentration gradient. The flow in the medium is assumed to be unidirectional and the average velocity is taken to be constant throughout the length of the flow field. BASIC EQUATION AND SOLUTION Because mass is conserved, tl^e governing differential equation is determined to be d<7 (1) v where D=dispersion coefficient C= concentration of solute in the fluid u= average velocity of fluid or superficial velocity/ porosity of medium x= coordinate parallel to flow y,z coordinates normal to flow 2=time. In the event that mass transfer takes place between the liquid and solid phases, the differential equation becomes _ 5(7 d(7 &F where F is the concentration of the solute in the solid phase. The specific problem considered is that of a semiinfinite medium having a plane source at z=0. Hence equation 1 becomes Initially, saturated flow of fluid of concentration, (7=0, takes place in the medium. At t Q, the concentration of the plane source is instantaneously changed to (7=(70 . Thus, the appropriate boundary conditions are <7(co,£)=0; *> The problem then is to characterize the concentration as a function of x and t. To reduce equation 1 to a more familiar form, let (4) A-l 586211 61 2 A-2 FLUID MOVEMENT IN EARTH MATERIALS Substituting equation 4 into equation 1 gives The boundary conditions transform to = Co exp ( It is thus required that equation 5 be solved for a timedependent influx of fluid at 2=0. The solution of equation 5 may be obtained readily by use of Duhamel's theorem (Carslaw and Jaeger, 1947, p. 19): If C=F(x,y,z,t) is the solution of the diffusion equation for semi-infinite media in which the initial concentration is zero and its surface is maintained at concentration unity, then the solution of the problem in which the surface is maintained at temperature (t) is
875 citations
"Numerical modelling on fate and tra..." refers methods in this paper
...Similarly, the performance of the present contaminant transport model was verified by comparing the model predictions at low and high Peclet numbers with the analytical solution given by Ogata and Banks (1961) (Figure 3(a) and (b))....
[...]
... Present transport model (a) verification at Pe = 1 with analytical solution 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…...
[...]
...…transport model (a) verification at Pe = 1 with analytical solution 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…...
[...]
TL;DR: The IGBP/T data set includes some groups of soils, e.g., Andosols and Ferralsols, whose properties are extremely different from those of most temperate soils.
271 citations
"Numerical modelling on fate and tra..." refers background in this paper
...This phenomenon is likely in sands or structured soils (Hodnett and Tomasella, 2002)....
[...]
TL;DR: The enhancement of the microbial activity inhydrocarbon-contaminated soil can be achieved with the combination of stepwise soil inoculation and nutrient additions.
Abstract: Biodegradation of diesel oil was performed using adiesel oil-degrading bacterial consortium, in bothlaboratory and pilot scale experiments. The bacterialconsortium was prepared in liquid for laboratory testsand for pilot scale experiments, it was prepared intwo steps, liquid and then in soil. The concentrationof diesel in soil treated with the bacterialconsortium was reduced to <15% of the initialconcentration, within a period of five weeks in bothlaboratory (135 to 19.32 g diesel kg (soil dryweight)-1) and pilot scale (118 to 17.5 g dieselkg (soil dry weight)-1) experiments, incomparison with controls (without bacterialconsortium), in which initial concentration of dieselwas reduced by only 5 and 15%, respectively. Dieselbiodegradation rate with the bacterial consortium was2.13 g diesel kg (soil dry weight)-1 d-1, itwas slightly enhanced by the addition ofNH4NO3 in the presence of bacterialconsortium 2.78 g diesel kg (soil dry weight)-1d-1. The enhancement of the microbial activity inhydrocarbon-contaminated soil can be achieved with thecombination of stepwise soil inoculation and nutrient additions.
185 citations
TL;DR: Pesticides in the surface water samples from Bhandara and Yavatmal region exceeded the EU (European Union) limit of 1.0 μg/L but were within the WHO guidelines for individual pesticides.
Abstract: The organochlorines (OClPs) and organophosphates (OPPs) pesticides in surface and ground water having intensive agriculture activity were investigated to evaluate their potential pollution and risks on human health. As per USEPA 8081 B method, liquid-liquid extraction followed by Gas-Chromatographic technique with electron capture detector and mass selective detector (GC-MS) were used for monitoring of pesticides. Among organochlorines, α,β,γ,δ HCH’s, aldrin, dicofol, DDT and its derivatives, α,β endosulphan’s and endosulphan-sulphate were analysed; dichlorovos, ethion, parathion-methyl, phorate, chlorpyrifos and profenofos were determined among organophosphates. As compared to ground water, higher concentrations of OClPs and OPPs were found in surface water. Throughout the monitoring study, α - HCH (0.39 μg/L in Amravati region),α - endosulphan (0.78 μg/L in Yavatmal region), chlorpyrifos (0.25 μg/L in Bhandara region) and parathion-methyl (0.09 μg/L in Amravati region) are frequently found pesticide in ground water, whereas α,β,γ-HCH (0.39 μg/L in Amravati region), α,β - endosulphan (0.42 μg/L in Amravati region), dichlorovos (0.25 μg/L in Yavatmal region), parathion-methyl (0.42 μg/L in Bhandara region), phorate (0.33 μg/L in Yavatmal region) were found in surface water. Surface water was found to be more contaminated than ground water with more number of and more concentrated pesticides. Among pesticides water samples are found to be more contaminated by organophosphate than organochlorine. Pesticides in the surface water samples from Bhandara and Yavatmal region exceeded the EU (European Union) limit of 1.0 μg/L (sum of pesticide levels in surface water) but were within the WHO guidelines for individual pesticides.
135 citations
"Numerical modelling on fate and tra..." refers background in this paper
...In the past few years, the detection of potentially harmful chemicals frequently in surface and groundwaters has become an issue of serious concern (Kumar et al. 2011; Lari et al. 2014; Morrison and Newell 1999)....
[...]
TL;DR: In this paper, a 15 m×15 m field plots, a Te Awa silt loam and a Twyford fine sandy loam, located in Hawkes Bay, New Zealand, were applied with bromide, picloram, atrazine, and simazine.
112 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)....
[...]