Soil Column Tests Research Articles

A new integrated surface and subsurface flows model and its verification

A new coupled model for simulating surface and subsurface flows in a fully integrated way is presented. This model contains two sub-models; one is the 2D kinematic wave approximation of the Saint Venant’s equations used to model runoff, and another is Richards’ equation for variably saturated subsurface flow. In this model, boundary conditions (the conditions describing groundwater discharge at the land surface or surface water infiltration into the subsurface) could be eliminated through mathematic transformations of the governing equation of surface and subsurface flows. The solution of surface and subsurface flows could be simultaneous. And the surface domain and subsurface domain could be considered as a fully integrated domain. This approach naturally provides pressure and fluxes continuity along land surface. In order to assess this modelling approach, several classical validations, verification and application test cases are presented. For overland flow solely, the model is compared to an analytical solution and to commonly use hydrological models. The integrated model is then validated with a sandbox laboratory experiment and a soil column test. Finally, the effects of rainfall intensity, hydraulic conductivity of soils and initial bulk water content of soils to runoff and infiltration of a homogeneous soil slope are studied under different conditions.

Salinity and Soluble Organic Matter on Virus Sorption in Sand and Soil Columns

The objective of this research was to study the sorption and transport of bacteriophage MS-2 (a bacterial virus) in saturated sediments under the effect of salinity and soluble organic matter (SOM). One-dimensional column experiments were conducted on washed high-purity silica sand and sandy soil. In sand column tests, increasing salinity showed distinct effect on enhancing MS-2 sorption. However, SOM decreased MS-2 sorption. Using a two-site reversible-irreversible sorption model and the double layer theory, we explained that pore-water salinity potentially compressed the theoretical thickness of double layers of MS-2 and sand, and thus increased sorption on reversible sorption sites. On irreversible sorption sites, increasing salinity reversed charges of some sand particles from negative to positive, and thus converted reversible sorption sites into irreversible sites and enhanced sorption of MS-2. SOM was able to expand the double layer thickness on reversible sites and competed with MS-2 for the same binding place on irreversible sites. In sandy soil column tests, the bonded and dissolved (natural) soil organic matters suppressed the effects of pore-water salinity and added SOM and significantly reduced MS-2 adsorption. This was explained that the bonded soil organic matter occupied a great portion of sorption sites and significantly reduced sorption sites for MS-2. In addition, the dissolved soil organic matter potentially expanded the double layer thickness of MS-2 and sandy soil on reversible sorption sites and competed with MS-2 for the same binding place.

Estimation of mass transport parameters of gases for quantifying CH4 oxidation in landfill soil covers

Methane (CH(4)), which is one of the most abundant anthropogenic greenhouse gases, is produced from landfills. CH(4) is biologically oxidized to carbon dioxide, which has a lower global warming potential than methane, when it passes through a cover soil. In order to quantify the amount of CH(4) oxidized in a landfill cover soil, a soil column test, a diffusion cell test, and a mathematical model analysis were carried out. In the column test, maximum oxidation rates of CH(4) (V(max)) showed higher values in the upper part of the column than those in the lower part caused by the penetration of O(2) from the top. The organic matter content in the upper area was also higher due to the active microbial growth. The dispersion analysis results for O(2) and CH(4) in the column are counter-intuitive. As the upward flow rate of the landfill gas increased, the dispersion coefficient of CH(4) slightly increased, possibly due to the effect of mechanical dispersion. On the other hand, as the upward flow rate of the landfill gas increased, the dispersion coefficient of O(2) decreased. It is possible that the diffusion of gases in porous media is influenced by the counter-directional flow rate. Further analysis of other gases in the column, N(2) and CO(2), may be required to support this hypothesis, but in this paper we propose the possibility that the simulations using the diffusion coefficient of O(2) under the natural condition may overestimate the penetration of O(2) into the soil cover layer and consequently overestimate the oxidation of CH(4).

Measurement of geotextile-water characteristic curve using capillary rise principle

This paper presents the experimental procedure to obtain the water characteristic curve of a geosynthetic material. The capillary rise principle was used to obtain both drying and wetting water characteristic curves. The water characteristic curves obtained from the tests were then verified using numerical analyses of soil column tests. The soil column was constructed using 0.51 m thick fine sand overlying a drainage product made of three-dimensional polypropylene monofilaments combined with two layers of polypropylene geotextile. The numerical analysis results of drawdown and rainfall tests show good agreement with the experimental data. This is an indication that the material properties, including the water characteristic curve of the geosynthetic material, were accurately measured.

Laboratory Study on the Mobility of Heavy Metals in Residual Compacted Soil

Studies on heavy metal behavior in soil have received considerable attention and have helped to increase the understanding of their mobility and retention in the environment. Given the scarcity of information available in the literature on heavy metal transport parameters in Brazilian tropical soils, the main contribution of this paper is improving the knowledge about the mobility of some of these elements in compacted residual gneissic soil. Laboratory soil column tests together with chemical, physical and micromorphological analyses were performed on soil samples. The artificial contaminant solution used in the tests was prepared by addition of nitrate salts of Mn2+, Zn2+, Cd2+, Cu2+, Pb2+ and Cr3+. The main conclusions were as follows. Initial percolation of distilled water to saturate the soil without counter pressure influenced the column test results since the soil structure was altered, especially when a large pore volume was percolated. Hydraulic conductivity values decreased significantly in all soil columns with contaminant solution percolation. The metals Cu, Pb and Cr remained totally retained in the soil. Comparison of Mn transport parameters determined in the present study with those obtained in a previous one showed that for the tests performed Mn mobility was practically independent of soil hydraulic conductivity when all other factors were held constant.

Experimental Study of Fluorine Transport Rules in Unsaturated Stratified Soil

Abstract With the aid of soil column test models, the transport rules of fluorine contaminants in unsaturated stratified soils are discussed. Curves of F− concentrations at different times and sites in the unsaturated stratified soil were obtained under conditions of continuous injection of fluoride contaminants and water. Based on the analysis of the actual observation data, the values between computed results and observed data were compared. It is shown that the chemical properties of fluorine ions are active. The migration process of fluorine ions in soils is complex. Because of the effect of adsorption and desorption, the curve of the fluorine ion breakthrough curve is not symmetric. Its concentration peak value at each measuring point gradually decays. The tail of the breakthrough curve is long and the process of leaching and purifying using water requires considerable time. Along with the release of OH− in the process of fluorine absorption, the pH value of the soil solution changed from neutral to alkalinity during the test process. The first part of the breakthrough curve fitted better than the second part. The main reason is that fluorine does not always exist in the form of fluorinions in groundwater. Given the long test time, fluorinions possibly react with other ions in the soil solution to form complex water-soluble fluorine compounds. Only the retardation factor and source-sink term have been considered in our numerical model, which may leads to errors of computed values. But as a whole the migration rules of fluorine ions are basically correct, which indicates that the established numerical model can be used to simulate the transport rules of fluorine contaminants in unsaturated stratified soils.

Surface Seals Reduce 1,3‐Dichloropropene and Chloropicrin Emissions in Field Tests

Reducing emissions is essential for minimizing the impact of soil fumigation on the environment. Water application to the soil surface (or water seal) has been demonstrated to reduce 1,3-dichloropropene (1,3-D) emissions in soil column tests. This study determined the effectiveness of water application to reduce emissions of 1,3-D and chloropicrin (CP) in comparison to other surface seals under field conditions. In a small-plot field trial on a Hanford sandy loam soil (coarse-loamy, mixed, superactive, nonacid, thermic Typic Xerorthents) in the San Joaquin Valley, CA. Telone C35 (61% 1,3-D and 35% CP) was shank-applied at a depth of 46 cm at a rate of 610 kg ha-1. Soil surface seal treatments included control (no tarp and no water application), standard high density polyethylene (HDPE) tarp over dry and pre-irrigated soil, virtually impermeable film (VIF) tarp, initial water application by sprinklers immediately following fumigation, and intermittent water applications after fumigation. The atmospheric emissions and gas-phase distribution of fumigants in soil profile were monitored for 9 d. Among the surface seals, VIF and HDPE tarp over dry soil resulted in the lowest and the highest total emission losses, respectively. Intermittent water applications reduced 1,3-D and CP emissions significantly more than HDPE tarp alone. The initial water application also reduced emission peak and delayed emission time. Pre-irrigated soil plus HDPE tarp reduced fumigant emissions similarly as the intermittent water applications and also yielded the highest surface soil temperature, which may improve overall soil pest control.

ESTIMATING DISPERSION COEFFICIENT FROM SOIL-COLUMN TEST

ABSTRACT Tracer test in a soil column is one of the reliable techniques for the estimation of dispersion coefficient. In a tracer movement test, the exit concentration known as breakthrough curve with time is observed from known input in the form of step change in the concentration input. In the present paper, two methodologies viz., summation distribution graph and Z-transform of transfer function of the process have been proposed for the estimation of dispersion coefficient from the data on soil-column test. Application of the methodologies has been demonstrated on the published data. The results indicated that the proposed methods have better potential to estimate the dispersion coefficient with reliable accuracy. A summation distribution graph approach can easily perform on a simple scientific calculator whereas; later one needs linear optimization technique.

Adsorption of nitrate as a groundwater pollutant by soil particles

This study discusses nitrogen adsorption in several soil samples of the Kanto loam collected from two locations in the Kanto plain. Their chemical properties were assessed on each of the soil samples as well as on pure allophane clay by instrumental analysis using batch and soil column tests.
 Nitrogen-nitrate adsorption by soil samples was determined by a 10-hour batch test using a nitric acid solution of 0.14 mmol. A saturation column test was conducted to obtain a breakthrough curve and calculate the coefficients of dispersion and retardation. The extent of nitrate adsorption in soil samples was confirmed by percolation with 0.14 mmol nitric acid through columns packed with the soil sample and silicate sand.
 In the batch test, it was found that the amount of nitrate adsorption was greater in allophane-rich volcanic ash soils with the amount of nitrate adsorption increasing under conditions of low pH. The breakthrough curve determined by the column test showed that the coefficient of retardation increased in allophane-rich soils.
 Adsorption of nitrates by Kanto loam soils was thus found to be dependent upon the content of allophane and amorphous material in the soil. Since the positive charge of allophane has the potential to reduce the nitrate content in groundwater, it can be effectively applied to reduce nitrate contamination in groundwater.

Determination of transport parameters for heavy metal in residual compacted soil using two methodologies

Values of the hydrodynamic dispersion coefficient and retardation factor obtained using the traditional and cumulative mass methods of column test analysis for zinc, manganese, and cadmium in a compacted soil are compared. The soil under study is from the B horizon of a residual gneissic tropical soil used for construction of the liner for the sanitary landfill in the District of Visconde do Rio Branco, Minas Gerais (MG), Brazil. To evaluate the behavior of landfill leachate heavy metals through the soil, soil column tests were performed on samples of compacted soil. A computational program that uses an optimization procedure to generate values of the hydrodynamic dispersion coefficient and retardation factor was developed to facilitate interpretation of the results obtained by the cumulative mass method. Values of the retardation factor and hydrodynamic dispersion coefficient were not influenced by the method of determination, even when a reduced number of effluent samples was used by the cumulative mass method. The use of the cumulative mass method, based on a reduced number of pore volumes, reduces the time and cost involved in the tests.Key words: heavy metals, column test, cumulative mass method.

Dissolution kinetics of high explosives particles in a saturated sandy soil

Solid phase high explosive (HE) residues from munitions detonation may be a persistent source of soil and groundwater contamination at military training ranges. Saturated soil column tests were conducted to observe the dissolution behavior of individual components (RDX, HMX, and TNT) from two HE formulations (Comp B and C4). HE particles dissolved readily, with higher velocities yielding higher dissolution rates, higher mass transfer coefficients, and lower effluent concentrations. Effluent concentrations were below solubility limits for all components at superficial velocities of 10–50 cm day − 1 . Under continuous flow at 50 cm day − 1 , RDX dissolution rates from Comp B and C4 were 34.6 and 97.6 μg h − 1 cm − 2 (based on initial RDX surface area), respectively, significantly lower than previously reported dissolution rates. Cycling between flow and no-flow conditions had a small effect on the dissolution rates and effluent concentrations; however, TNT dissolution from Comp B was enhanced under intermittent-flow conditions. A model that includes advection, dispersion, and film transfer resistance was developed to estimate the steady-state effluent concentrations.

유기인계 및 카바메이트계 농약의 토주용탈과 대류이동성 모형에 의한 이동성 예측

농약별 수직이동 양상을 파악하고, 흡착계수와 토양관련 매개변수를 이용하여 대류이동성 모형(Convective mobility test model)으로 예측한 용탈 속도와 비교 평가하기 위하여 강서통(논), 중동통(밭), 예산통(산림토양) 및 신엄통(화산회토)을 사용하여 카바메이트계 농약 metolcarb, molinate, fenobucarb 및 dimepiperate와 유기인계 농약 isazofos, diazinon, fenitrothion, parathion 및 chlorpyrifos-methyl의 도주용탈실험을 수행하였다. 각 농약을 <TEX>$50{\mu}g/cm^2$</TEX> 수준으로 토주 상단에 처리하였을 때 토심 10 cm 이동 후 용탈되는 농약별 최대용탈(peak) 농도는 화산회토를 제외한 3종 토양의 경우 metolcarb <TEX>$6.5{\sim}12.6mg/L$</TEX>, molinate <TEX>$2.6{\sim}5.0mg/L$</TEX>, fenobucarb <TEX>$4.5{\sim}7.8mg/L$</TEX>, dimepiperate <TEX>$0.39{\sim}1.36mg/L$</TEX> isazofos <TEX>$1.1{\sim}4.6mg/L$</TEX>, diazinon <TEX>$0.01{\sim}0.14mg/L$</TEX>, fenitrothion 0.01 mg/L 미만<TEX>${\sim}0.70mg/L$</TEX> 및 parathion 0.01 mg/L 미만<TEX>${\sim}0.44mg/L$</TEX> 수준이었고 chloipyrifos-methyl은 네 토양 모두에서 용탈되지 않았다. Peak 농도 출현까지 소요된 용탈수량은 metolcarb <TEX>$1.1{\sim}2.1$</TEX> pore volume(PV), molinate <TEX>$1.6{\sim}3.3$</TEX> PV, fenobucarb <TEX>$1.6{\sim}3.3$</TEX> PV, isazofos <TEX>$2.1{\sim}4.4$</TEX> PV, diazinon <TEX>$6{\sim}15$</TEX> PV 및 dimepiperate <TEX>$8{\sim}21$</TEX> PV 수준이었다. 대류이동성 모형에 의한 예측결과는 대부분의 토양-농약 조합에서 토주용탈 양상과 일치하였고 표준조건(water flux 1 cm/일)에서 예측된 이동소요시간에 따라 metolcarb는 most mobile, molinate와 fenobucarb, isazofos는 mobile내지 most mobile, dimepiperate는 moderately mobile이나 mobile, diazinon은 mobile, fenitrothion과 parathion은 slightly mobile 또는 mobile, chloipyrifos-methyl은 immobile이나 slightly mobile 등급에 속하는 것으로 나타났다. This study was conducted to investigate the downward mobility of pesticides using soil columns and to compare the experimental results with values predicted from Convective mobility test model. Nine pesticides such as metolcarb, molinate, fanobucarb, isazofos, diazinon, fenitrothion, dimepiperate, parathion and chlorpyrifos-methyl were used for leaching test in soil column for four soils; Jungdong (upland soil), Gangseo (paddy soil), Yesan (forest soil), and Sineom(upland, volcanic ash-derived soil) series. The peak concentrations leached from 10 cm-columns of three soils except Sineom series ranged 6.5 to 12.6 mg/L for metolcarb, 2.6 to 5.0 mg/L for molinate, 4.5 to 7.8 mg/L for fenobucarb, 0.39 to 1.36 mg/L for dimepiperate, 1.1 to 4.6 mg/L for isazofos, 0.01 to 0.14 mg/L for diazinon, lower than 0.01 to 0.70 mg/L for fenitrothion and lower than 0.01 to 0.44 mg/L for parathion. But chlorpyrifos-methyl was not leached from any soil columns. Elution volumes to reach the peak of metolcarb, molinate, fenobucarb, isazofos, diazinon, and dimepiperate in the leachate ranged 1.1 to 2.1 pore volume (PV), 1.6 to 3.3 PV, 1.6 to 3.3 PV, 2.1 to 4.4 PV, 6 to 15 PV, and 8 to 21 PV, respectively. On the same water flux conditions, convection times estimated by Convective mobility test model were coincided with results from soil column test in most of the soil-pesticide combinations applied. Based on convection times estimated by the model at standard conditions (water flux 1 cm/day), metolcarb was classified as most mobile, molinate, fenobucarb and isazofos as mobile or most mobile, dimepiperate as moderately mobile or mobile, diazinon as mobile, fenitrothion and parathion as slightly mobile or mobile and chlorpyrifos-methyl as immobile or slightly mobile.

Processes in vertical-flow reed beds: nitrification, oxygen transfer and soil clogging

Vertical-flow reed beds (VF) with intermittent feeding are extremely reliable regarding aerobic processes. For a save operation with high nitrification rates and without soil clogging it is essential to preserve aerobic conditions in the filter. The challenge is to keep aerobic conditions in the filter without oversizing the system (economical aspects). It is very difficult to determine the current oxygen content in the filters because it ultimately results from complex interactions of a large number of different influencing parameters such as loading rate, degree of clogging, temperature, and hydraulic behaviour of the reed bed. To gain better knowledge of this complex system, different tests and examinations were carried out over several years. Focusing on the questions of identification and the description of conversion and transport processes (water/gas), a full-scale treatment plant under clogged and non-clogged conditions was investigated in detail. Additionally soil column test were carried out. The results make it possible to describe some of the processes and their interactions in the filter body. Recommendations for a safe and controlled operation can be derived.

Mesh-free Method for Soil-water Coupled Problem within Finite Strain and Its Numerical Validity

A formulation of the Element-Free Galerkin Method (EFG method), i.e., one of the mesh-free/meshless methods developed in the field of computational mechanics for solving partial differential equations, is furnished for consolidation within finite strain and its validity for application to soil-water coupled problems is examined through a numerical analysis. The numerical strategy is constructed to solve a set of governing equations, e.g., the equilibrium for the nominal stress rate and the continuity of pore water, and the numerical discretization of the weak form of the governing equations leads to an updated Lagrangian scheme. The accuracy of the proposed numerical strategy is examined through an analysis of unconfined compression tests and simple shear tests under undrained and plane strain conditions through a comparison of stress paths integrated directly from the Cam-clay model within the framework of finite strain. It is also revealed that the particular type of weight function to be adopted in the moving least-squares (MLS) approximation, even in the same order, can determine the resultant shape functions of the EFG method for both the displacement and the pore water pressure field such that they are smoother than those of the usual FEM. The functions are advantageous in that they avoid spatial instability in the numerical solutions for pore water pressure under undrained conditions appearing in saturated soil column tests, where the shape function of the pore water pressure in the conventional FEM computation is adopted as a lower order than that of the displacement to remedy this type of numerical difficulty. To emphasize the applicability and the feasibility of the mesh-free computation, the consolidation phenomena are demonstrated in the analysis of a punch problem for a soft soil foundation which has stress singularity under both ends of a rigid loading platen for the same problem which Yatomi et al. (1989) solved with FEM.

Surfactant Effects on Residual Water and Oil Saturations in Porous Media

A series of soil column tests was performed to determine surfactant effects on residual water and oil saturations in porous media. In particular, these tests focused on the impact of submicellar surfactant solutions and the potential application of these low concentration systems to light nonaqueous phase liquid (LNAPL) contamination in the vadose zone. One set of tests involved surfactant flushing in soil‐filled columns followed by drainage to residual water saturation and LNAPL injection to determine the subsequent residual LNAPL saturation. Another set of tests involved surfactant application to a soil‐filled column already holding residual LNAPL saturation to promote the release of the previously trapped LNAPL. Test results showed surfactant systems could reduce both residual water and oil saturations by up to 50%. In addition, submicellar surfactant systems were equally effective as supramicellar solutions in reducing residual water saturations and potentially more effective at reducing residual oil saturations. Submicellar surfactant applications to a medium‐grained (0.85–0.425 mm) soil containing residual LNAPL saturations were effective at releasing up to 50% of the previously trapped residual LNAPL. These applications were less successful in a fine‐grained soil as full drainage of water and LNAPL was unachievable due to high capillary pressures. Overall, observations suggest low concentration surfactant solutions may have the ability to release significant amounts of previously trapped LNAPL in the vadose zone, potentially increasing free‐product recovery rates and lowering LNAPL saturations to levels more favorable for biodegradation. The decrease in overall saturations (both water and oil) in a contaminated vadose zone could also present an increase in air permeability, thus enhancing other vadose zone treatment technologies such as bioventing or soil vapor extraction.

Surfactant Effects on Residual Water and Oil Saturations in Porous Media

A series of soil column tests was performed to determine surfactant effects on residual water and oil saturations in porous media. In particular, these tests focused on the impact of submicellar surfactant solutions and the potential application of these low concentration systems to light nonaqueous phase liquid (LNAPL) contamination in the vadose zone. One set of tests involved surfactant flushing in soil-filled columns followed by drainage to residual water saturation and LNAPL injection to determine the subsequent residual LNAPL saturation. Another set of tests involved surfactant application to a soil-filled column already holding residual LNAPL saturation to promote the release of the previously trapped LNAPL. Test results showed surfactant systems could reduce both residual water and oil saturations by up to 50%. In addition, submicellar surfactant systems were equally effective as supramicellar solutions in reducing residual water saturations and potentially more effective at reducing residual oil saturations. Submicellar surfactant applications to a medium-grained (0.85–0.425 mm) soil containing residual LNAPL saturations were effective at releasing up to 50% of the previously trapped residual LNAPL. These applications were less successful in a fine-grained soil as full drainage of water and LNAPL was unachievable due to high capillary pressures. Overall, observations suggest low concentration surfactant solutions may have the ability to release significant amounts of previously trapped LNAPL in the vadose zone, potentially increasing free-product recovery rates and lowering LNAPL saturations to levels more favorable for biodegradation. The decrease in overall saturations (both water and oil) in a contaminated vadose zone could also present an increase in air permeability, thus enhancing other vadose zone treatment technologies such as bioventing or soil vapor extraction.

Errata for “Estimating Dispersion Coefficient and Porosity from Soil-Column Tests” by Sushil K. Singh

Errata for “Estimating Dispersion Coefficient and Porosity from Soil-Column Tests” by Sushil K. Singh

Experimental evidence on the role of gas in sediment liquefaction and mud volcanism

Abstract Mud volcanoes are structures that are formed through ‘cold volcanism’ and indicate soil liquefaction. Their evolution depends on the structure, state and excitation of fine-grained feeding sediments. The disturbance of the framework of a loose, fine-grained, saturated sediment causes shear deformation leading to a pore fluid pressure increase. Effective stresses are thereby reduced and can vanish; the soil is then totally liquefied. Small amounts of enclosed gas bubbles render the soil compressible and enhance local shearing, pore pressure build-up and structural damage. Liquefield, overpressurized sediments form mud chambers, whose excess pressure is released through cracks and other inherent weak channels caused, for example, by density variations in the overlying strata. Experiments were conducted on small-scale soil columns and on model slopes, using quartz powder as model material. Soil column tests were aimed at determining the influence of gas bubbles with regard to the liquefaction process, whereas model slope tests were targeted at the collapsability of gentle slopes, subject to atmospheric pressure changes. Different initial porosities were achieved through ion content variation. Liquefaction of fine-grained sediments and subsequent volcano evolution could be produced.

110mAg root and foliar uptake in vegetables and its migration in soil

110mAg, as a radionuclide of corrosion products in water-cooled nuclear reactors, was detected in the liquid effluents of Guangdong Daya Bay Nuclear Power Station (GNPS) of Daya Bay under normal operation conditions. Experiments on a simulated terrestrial agricultural ecosystem were carried out using the pot experiment approach. The most common plants in Hong Kong and the South China vegetable gardens such as lettuce, Chinese spinach, kale, carrot, pepper, eggplant, bean, flowering cabbage, celery, European onion and cucumber were selected for 110mAg root and foliar uptake tests. The results show that carrot, kale and flowering cabbage have the greatest values of soil to plant transfer factor among the vegetables, while 110mAg can be transferred to Chinese spinach via foliar uptake. Flowering cabbage, the most popular leafy vegetable locally, could be used as a biomonitor for the radioisotope contamination in vegetables. Soil column and adsorption tests were also carried out to study the leaching ability and distribution coefficient ( K d) of 110mAg in the soil. The results show that most of the radionuclide was adsorbed in the top 1 cm of soil regardless of the pH value. The K d was also determined.

Estimating Dispersion Coefficient and Porosity from Soil-Column Tests

A simple method for simultaneous and explicit estimation of dispersion coefficient and porosity from laboratory data on soil-column tests is presented. It makes use of the peak derivative of the observed breakthrough curve (BTC). An objective procedure for approximate location of the peak is suggested based upon a parabolic fit through three consecutive points around the peak. The computations involved are simple and can be done on a calculator. The method does not require either the rate of flow or the cross-sectional area of the soil-column for estimating the dispersion coefficient. This completely avoids the possible errors involved in the measurement of these quantities. The new method does not require the full BTC to be observed, however, its application does require data slightly beyond the time at which the exit concentration reaches half the input concentration. Application of the method on a number of laboratory data sets shows that it can yield a reliable estimate of the dispersion coefficient and porosity using only a few points near the peak. The method is applicable for high values (>100) of the piclet number.