Journal of Contaminant Hydrology 145 (2013) 54–66

Contents lists available at SciVerse ScienceDirect

Journal of Contaminant Hydrology

j ourna l homepage: www.e lsev ie r .com/ locate / jconhyd

Prospective modeling with Hydrus-2D of 50 years Zn and Pb movements inlow and moderately metal-contaminated agricultural soils☆

Danilo Rheinheimer dos Santos a, Philippe Cambier b,c, Fábio Joel Kochem Mallmann a,Jérôme Labanowski b,d, Isabelle Lamy b, Daniel Tessier b, Folkert van Oort b,⁎a Departamento de Solos, Universidade Federal de Santa Maria, 97.105-900 Santa Maria, Rio Grande do Sul, Brazilb INRA, UR251, Pessac, RD 10, F-78026 Versailles Cedex, Francec INRA, UMR1091, EGC, F-78850, Thiverval-Grignon, Franced CNRS, UMR6008, LCME, Université de Poitiers-ESIP, 40, Avenue du Recteur Pineau, F 86022 Poitiers, France

a r t i c l e i n f o

☆ “Capsule”: a two-site hydrodynamic model setparameters simulated the 2005–2055 migration of Zn⁎ Corresponding author. Tel.: +33 130833251.

E-mail address: vanoort@versailles.inra.fr (F. van O

0169-7722/$ – see front matter © 2012 Elsevier B.V. Ahttp://dx.doi.org/10.1016/j.jconhyd.2012.12.001

a b s t r a c t

Article history:Received 2 February 2012Received in revised form 26 November 2012Accepted 3 December 2012Available online 20 December 2012

Results of detailed modeling of in situ redistribution of heavy metals in pedological horizons oflow and moderately metal contaminated soils, considering distinctly different long-term landuse, are scarcely reported in literature. We used Hydrus-2D software parameterized withabundant available local soil data to simulate future Zn and Pb movements in soilscontaminated by metallurgical fallout in the 20th century. In recent work on comparingdifferent modeling hypotheses, we validated a two-site reactive model set with adjustedchemical kinetic constant values by fitting the 2005 Zn and Pb concentration profiles in soils,with estimated 1901–1963 airborne Zn and Pb loads (Mallmann et al., 2012a). In thepresent work, we used the same approach to simulate 2005–2055 changes in Zn and Pbdepth-distribution and soil-solution concentrations, comparing two hypotheses of chemicalequilibrium: i) the validated two-site model (one site at equilibrium and the other involved inkinetic reactions with pore water) set with adjusted kinetic EDTA extraction constants, and ii)a non-linear one-surface site adsorption equilibrium model. Simulated transfers were foundgenerally lower and more realistic when using the two-site model. Simulations showed thatconsistent Zn redistribution and loss occurred in the moderately contaminated soil until 2055,i.e., more than one century after the main metal deposition, but negligible in low contaminatedsoils. Transfer of Pb was small in the three soils and under both hypotheses. In 2055, simulatedZn outflow concentrations remained under threshold values for drinking water.

© 2012 Elsevier B.V. All rights reserved.

Keywords:Prospective modelingHydrus-2DZincLeadMetal distributionKinetic EDTA extractionsAgricultural soil

1. Introduction

Environmental contamination by heavy metals is a growingproblem, becoming more critical in many agricultural areas ofthe planet. Major sources of metal contamination are chemicalfertilizers and organic manure application, mining activities,sanitary landfills, soil amendments with sewage sludge, wastewater irrigation and atmospheric deposition (Carrillo-González

with EDTA extractionand Pb in soils.

ort).

ll rights reserved.

et al., 2006; Escarré et al., 2010; van Oort et al., 2008).Atmospheric fallout deposition of metals on the soil's surface,from industrial activity, often shows deposition rates increasingwith duration and intensity of this activity, and decreases withdistance from the industrial pollution source (van Oort et al.,2009).

Metal loads from atmospheric deposition at the soil'ssurface often rapidly alter under soil conditions (Bataillardet al., 2003). Hence, liberated metals either interact with soilsolid phases or are dissolved into the soil solution where theymaymigrate to the groundwater. The rates ofmetal movementin soils depend on a wide range of physical and chemicalsoil characteristics. With respect to physical properties, the

55D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

interconnectivity of macropores accelerates the water flow,reducing the contact time of solutes with the reactive soilfraction, which influences the transfer of contaminants indepth (Jarvis, 2007; Shipitalo et al., 2000). Soil mineralogy andorganic constitution are also key factors controlling metalmigration, due to high affinity of different functional groups ofsuch soil constituents for heavy metals (Sposito, 1989).

The use of mathematical models to simulate long-term,retrospective or prognostic redistribution of heavy metals insoils is often hampered by lacking validation due to un-certainties about historic metal inputs and/or absence ofdetailed pedological and physicochemical soil and soil solutiondata (van der Grift and Griffioen, 2008). Yet, such data isessential for a relevant prediction of the fate of contaminants insoils and of possible environmental damage. For example,Charbeneau et al. (2003) recommended the use of reactivesolute transport models to predict the movement of metals insoil profiles and their transfer to the groundwater. Cerník et al.(1994) applied different sets of equations to simulate thetransport of Cu and Zn issued from a copper smelter inneighboring soils and found more or less quantitative agree-ments with observed metal depth profiles. They hypothesizedthat processes like bioturbation and preferential path flow couldexplain the deviation of modeled distributions from real onesnear the soil surface. Streck and coworkers (e.g., Beyer et al.,2009; Streck and Richter, 1997) also used convection-dispersionand adsorption equations, with further description of spatialheterogeneities, to compare theoretical results and the surveyeddistributions of Cd in areas polluted by non-ferrous metallurgicplants or waste-water irrigation. Beyer et al. (2009) assessedthat preferential paths should be of low relevance relative tobulk transport for strongly sorbing metals. Degryse andSmolders (2006) presented arguments and data on Cd and Znleaching in polluted and unpolluted soils in favor of thehypothesis of local equilibrium between the different phases.They also estimated that metals in soils and atmospheric fallout,particularly Zn, cannot be considered homogeneously labile.Goldberg et al. (2007) reviewed transport models of reactivesolutes, focusing on models including surface complexationreactions of metals, referring to “a few field-scale applications”.Jacques et al. (2008) applied the code HP1 to the dynamic ofmajor and trace cations in an agricultural soil profile by couplingthe detailedmodeling of chemical reactions by PHREEQ-C to thesolute transport model Hydrus-1D. Their study pointed out theinfluence of transient flow and changing geochemical condi-tions. Yet, in most applications evoked above on transport oftrace metals in soils, the kinetic laws that may govern surfacereactions have not been considered, even if they are presentin some mechanistic adsorption models. On the contrary,semi-empirical models based on multi-site, equilibrium andnon-equilibrium reactions have been applied to cationic andanionic trace species (Jardine et al., 2011; Selim, 2002). Amongthe wide panels of available models, the Hydrus-2D softwarealso offers the possibility to introduce two types of reactivesurface sites on solid soil particles, one considered instanta-neously at equilibrium with the soil solution, the other oneinvolved in kinetic sorption reactions (Šimůnek et al., 1999).Running of this model for field applications requires hypothesesand/or data on chemical partitioning of metals with respect tosorption–desorption in different soil horizons (Mallmann et al.,2012a, 2012b).

In Northern France, a major metallurgical plant producedzinc and lead out of metal ores between 1902 and 1963. Thisindustrial complex generated important atmospheric dustemissions, mainly of Zn, Pb, and to a lesser extent of Cd, andCu, leading to considerable metal fallout deposition on soilsover an area of some tens of km2, estimated at ≈20,000 tons(van Oort et al., 2009). The soil cover, mainly sandy texturedsoils, was extensively studied between 1996 and 2005,generating a wide panel of geochemical data: (1) field surveyand geostatistical mapping of spatial distribution of total Znand Pb concentrations in the 0–30-cm surface layer ofagricultural and forest soils (van Oort et al., 2007, 2009),emphasized a general decrease with an increase in distanceto the former metallurgical plant. Such studies revealed astrong variability of Zn-to-Pb concentration ratio in the topsoils, due to consistent migration of Zn toward depth. SmallerZn/Pb values were found for more acidified and/or coarsesand textured soils, often under forest stand; (2) work ofFernandez et al. (2007, 2008, 2010) and Labanowski et al.(2007, 2008) focused on the role of agricultural land use andmanagement on metal distribution. They established detailed‘metal concentration–depth’ relations and demonstratedclearly different Zn and Pb concentration profiles for soilsunder conventional arable (CA) land or under permanentpasture (PP), despite comparable total metal contaminantinputs; (3) such different metal pollution incorporationwas mainly due to a different biological activity, notably ofearthworms, with densities quantified by Nahmani et al.(2003): 392 and 52 worms m−2 in the PP and CA soils,respectively; (4) using Pb isotope signatures, Fernandez et al.(2008) concluded that anthropogenic Pb occurred in the PPsoil down to 1-m deep, but was found restricted to the upper60 cm of the CA soil, predominantly located in the plowlayer; (5) in situ monitoring of metal concentrations ingravitational soil water was carried out by lysimetry for3 years (2000–2003) in soils under different land uses(Citeau, 2004). Soil water was collected with a 1–2-monthinterval, depending on local climatic events. For agriculturalland, Zn concentration in the soil solution was about ahundredfold higher than that of Pb. Zinc was found predom-inantly as free and dissolved Zn2+, contrarily to Pb, which ismainly present in a colloidal form associated to iron oxides(Citeau et al., 2003; van Oort et al., 2006). Concentrations of Cdin solution were generally much smaller than for Pb (Citeau,2004).

Mallmann et al. (2012a) simulated the past incorporationand redistribution of Zn and Pb in three soil profiles underagricultural land use of this area, by using Hydrus-2D set withthe available pedogeochemical and kinetic extraction data, andcombined with detailed historical information about themetallurgical smelter activity (Hardy, 1970). They obtained abetter correspondence with present-day metal concentrationdistributions by considering the two-site model than byassuming complete sorption equilibrium. The main objectiveof the present work was to use the recent validated two-sitemodel set with kinetic chemical constants for the prognosticmid-term 2005–2055 simulations of the fate of Zn and Pb inthese soil profiles, and to compare the results with simulationsunder a hypothesis of complete equilibrium. A second, morepractical objective was the assessment of metal losses fromsoils and consequent risks for groundwater contamination. In

56 D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

our work, we focused on the movement of Zn and Pb since(i) they are representative for mobile and little or non-mobilemetals, respectively; (ii) they represent the main metalelements emitted by metallurgical activity; (iii) large data setwere available for Zn and Pb in soil horizons, gravitational soilsolution and kinetic chemical extractions.

2. Materials and methods

2.1. Soil sites and selected physicochemical data

The study soils were under agricultural management,located at an increasing distance from a former zinc smeltercomplex in Northern France (Fig. 1), and affected by atmo-spheric fallout containing mainly Zn and Pb (van Oort et al.,2009). The main period of metal deposition, related to thehighest metallurgical activity was between 1908–1914 and1923–1930 (Hardy, 1970; Mallmann et al., 2012a). Three soilprofiles, loamy-sand textured eutric cambisols (IUSS WorkingGroup WRB, 2006) with four or five distinct horizons wereselected, previously studied by Mallmann et al. (2012a). Thesesoils developed in comparable parent material derived fromTertiary marine Ostricourt sand deposits containing predomi-nantly quartz, feldspar and glauconite grains. The clay miner-alogical composition was dominated by illite and smectite,illite–montmorillonite interstratified minerals, as well as somekaolinite. Micromorphological study (van Oort et al., 2007)showed the presence of moderate to frequent coarse and finecharcoal particles and an occasional occurrence of sand-sizedindustrial waste fragments.

We applied the simulation approach on a moderatelycontaminated soil, managed under conventional arable landuse where Zn and Pb concentrations in the surface horizonswere about a tenfold of the local chemical background level(Fernandez et al., 2007), designated as CA(++), and ontwo low contaminated soils, about a threefold of the localchemical background level, one under conventional arableland and the other under permanent pasture, designated asCA(+) and PP(+), respectively.

Scarpe

CA(++)

CA(+)

MORTAGNE-DU-NORD

1000 m

former industrialplant

PP(+)

Fig. 1. Location of the former metallurgical plant and of

The CA(++) soil was mainly used for maize–wheatproduction, located at about 750 m from the former metal-lurgical plant. For all soil horizons, total concentrations of Znand Pb after tri-acid digestion of soil samples (HF, HClO4,HCL, NF X31-147, Afnor, 2004), and key parameters guidingwater flow were measured (Afnor, 2004): clay, silt, and sandcontents; bulk density from the field with horizontalcylinders; and organic carbon content. In addition, concen-trations of Zn and Pb were determined in gravitational water,collected between 2000 and 2003 by in situ zero-tensionlysimeters placed at the lower limit of pedological horizons(Citeau et al., 2003).

The CA(+) and PP(+) soils were located at 2750 m and3100 m, respectively, from the industrial site. Macro- andmicro-morphological characteristics, soil physicochemical dataand metal distribution in these two soils were extensivelystudied by Fernandez et al. (2007, 2010). The CA(+) soil wasalso under maize–wheat rotation and conventionally tilledfor about 100 years. The PP(+) soil was under continuousgrassland since the beginning of the 20th century. Both soilsincluded 5 characteristic horizons within the first meter, butwith distinct characteristics. A striking difference was thedarker soil color and larger organic matter contents in thePP(+) soil, deeply incorporated in subsurface horizons by anintense earthworm activity (Fernandez et al., 2010; Nahmaniet al., 2003). In the CA(+) and PP(+) soils, the same soilcharacteristics were determined as for CA(++) (Table 1),except soil water chemistry (see Section 2.3).

2.2. Water flow and transport simulation

Using Hydrus-2D to simulate water flow and associated Znand Pb transport, we considered the two-dimensional flow inthe vertical plane and rectangular flow domain (Šimůnek et al.,1999), constructing a computer experimental domainwith 1-mdepth and 1-cm width, using high density nodes (Mallmannet al., 2012a). The van Genuchten water retention modeland van Genuchten–Mualem hydraulic conductivity modelwere used. The top boundary condition was consideredatmospheric time-variable. Daily precipitation and potential

Escaut

estateforest

PARIS.

the three studied soil profiles in northern France.

Table 1Chemical parameters of soil horizons under arable land (CA(++), CA(+)) and permanent pasture (PP(+)) used for simulation of Zn and Pb movements in the soilprofiles with the Hydrus-2D model.

Parameters CA(++) soil horizons, thickness, cm CA(+) soil horizons, thickness, cm PP(+) soil horizons, thickness, cm

Ap0–33

B133–45

B245–80

C80–100

Ap0–26

B126–44

B244–72

Cg172–87

Cg287–100

A110–6

A126–26

AB26–53

ACg53–76

Cg276–100

SoilClay, g kg−1 98 121 172 116 59 57 45 52 280 89 86 67 64 184Fe tot, g 100 g−1 1.3 1.6 2.1 1.8 1.0 0.9 0.9 1.3 4.7 1.0 1.2 1.1 1.1 3.1pH 6.51 6.6 6.7 6.8 6.4 6.3 6.6 6.6 6.7 5.6 5.7 5.7 5.9 6.3

ZincTotal, mg kg−1 445 239 56.8 40.0 111 63.6 37.9 27.0 39.1 75.1 79.6 58.9 55.7 43.2Solution, μg l−1 4780 2880 840 500 123 129 62.0 51.1 58.5 174 191 212 231 95.6β 0.41 0.37 0.07 0.01 0.27 0.36 0.22 0.13 0.01 0.36 0.33 0.39 0.39 0.02λ, 10−5 day−1 1.4 8.5 7.6 10.6 3.1 3.8 4.0 4.6 1.2 1.9 2.5 4.7 1.8 0.3KF 3.33 2.51 1.30 1.28 8.94 4.99 4.73 3.85 5.17 4.78 4.84 3.32 2.96 4.15n 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65 0.65

LeadTotal, mg kg−1 97.3 17.7 14.2 12.4 59.0 12.2 10.4 9.0 9.6 46.9 52.2 17.6 8.1 4.4Solution, μg l−1 2.85 1.90 2.16 1.62 2.71 1.22 0.86 0.80 0.76 4.70 4.60 2.50 1.37 0.69β 0.51 0.10 0.06 0.05 0.18 0.11 0.12 0.15 0.04 0.68 0.48 0.28 0.27 0.21λ, 10−5 day−1 0.5 2.0 4.7 1.1 5.5 4.9 4.0 4.2 6.6 4.2 3.92 10.1 8.7 1.4KF 2 255 567 417 469 1 426 582 661 616 689 706 806 454 351 341n 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85

β = the fraction of heavy metals adsorbed at instantaneous chemical equilibrium; λ = time constant kinetic for 1-β (1% of measured value); KF andn=parameters of the Freundlich isotherm for β sites, calculated with total and solution in mol g−1 and mol l−1, respectively.

57D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

evapotranspiration were estimated from local meteorologicaldata for the period between 01/01/1995 and 31/12/2004,provided by Météo France. The mean rain precipitation was867 mm year−1, and the mean potential evapotranspirationwas 740 mm year−1. Means of minimal and maximal annualtemperatures were 7.0 °C and 15.1 °C, respectively. For the50 years of simulation we used a repetition of 5 periods,meteorologically supposed identical to 1995–2004.We consid-ered negligible the input of Zn by rain precipitation and for Pb,we used the concentration of 2.7 μg l−1 of rain water reportedby Citeau (2004). Physical parameters used for modeling weretaken from Mallmann et al. (2012a). Briefly, the residual soilwater content (θr), the saturated soil water content (θs), αVG

and n parameters of the soil water retention function, aswell asthe saturated hydraulic conductivity (Ks) were estimated withthe Rosetta software (USDA-USSL, Riverside, California) fromclay, silt and sand contents, bulk density, and water content atpotentials of −33 and −1500 kPa. The water contents wereestimated from pedotransfer functions by using clay, silt andorganic carbon contents and the soil bulk density (Bruand et al.,2004). The pore-connectivity factor used for simulations was0.5 and was considered similar for all horizons (Šimůnek et al.,1999).

2.3. Physicochemistry of metal pollutants

The first simple hypothesis consisted in completesoil-solution equilibrium within each horizon, following theFreundlich isotherm (Eq. (1)).

Seq ¼ KFCn ð1Þ

where Seq is the fraction of heavy metals retained by thesolid phases at instantaneous chemical equilibrium, C is theconcentration of metals in soil solution, and KF and n

are adjusting parameters which vary with the type andconcentration of metals, and with the nature of soil constitu-ents. From publications that estimated this isotherm parame-ters for Zn, we retained here n=0.65 (Arias et al., 2005; Lairet al., 2006). For Pb, we retained n=0.85, the mean valueobtained by Buchter et al. (1989) on 8 soils. Then, for eachhorizon of CA(++), we fitted KF from the median of metalconcentrations measured from 2000 to 2003 in gravitationalwaters by Citeau (2004).

For the CA(+) and PP(+) soils, available data on thecomposition of soil solutions was insufficient. Therefore, weused the multiple regression equations proposed by Sauvéet al. (2000), and justified in Mallmann et al. (2012a). Inorder to introduce kinetics in soil-solution exchange, samplesof each horizon were submitted to kinetic extractionsfollowing Bermond et al. (1998). EDTA extractions (0.05 M,soil:solution ratio of 1:10, pH 6.6) were carried out and metalconcentrations determined after 5′, 15′, 30′, 60′, 120′, 8 h,16 h and 24 h. Two fractions were quantified from thetwo-site kinetic modeling described by Fangueiro et al.(2005):

Q ¼ Q1 1−e−κt� �

þ Q2 1−e−λt� �

ð2Þ

where Q (mg kg−1)=extractedmetal at time t; Q1=fractionof readily extractable metal, associated to the rate constant κ;Q2=fraction of less extractable metal, associated to rateconstant λ. Since κ values correspond to half-life constantsin the order of magnitude of minute, for transport modelingQ1 was considered at instantaneous equilibrium, and setequal to βQT. Then we considered that the remaining fractionQT−βQT could be desorbed or re-adsorbed at long-term inthe field, to allow comparison with the previous modelwhere the whole metal QT was supposed in equilibrium with

58 D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

the solution. However, the rate constant related to thisfraction is difficult to determine, but should be lower than theλ parameters determined by EDTA kinetic extractions for theQ2 fraction. Mallmann et al. (2012a) justified the choice of field(long-term) rate constants proportional to the rate constants λ,fitting only one parameter, the percentage of λ values, to makethe simulations of past metal accumulations and transfersconsistent with available historical and present data. Table 1presents all chemical parameters, including β and adjusted λvalues, used for modeling with Hydrus-2D for horizons of theCA(++), CA(+) and PP(+) soils, whereas physical parameterswere taken fromMallmann et al. (2012a). Using Hydrus-2D, wesimulated Zn and Pb transport for 2005–2055 in the three soils,under two hypotheses for metal reactivity:

(i) the fraction of metals at equilibrium with the soilsolution was the readily EDTA-extractable fraction, theremaining metal pool being subject to a kineticadsorption–desorption process according to rate con-stants, validated by Mallmann et al. (2012a);

(ii) 100% of metals present in each horizon was consideredat instantaneous chemical equilibrium with the soilsolution.

2.4. Processes not considered in simulations

The successful simulations on long-termmetal migrationin sandy textured soils by Mallmann et al. (2012a) consid-ered mainly solute transport and sorption processes withkinetic equations. Hence, there was no need to increase thecomplexity of the used model by modeling other transportaspects such as preferential path flow, often difficultto parameterize and only little relevant in such sandy soilscontaining mostly inter-granular pores, or colloidal facili-tated metal transfer, shown by Citeau et al. (2003) to be oflittle importance in the studied soils. Bioturbation wasreported to be significant in the soil under permanentpasture (Fernandez et al., 2010), but in all three studiedsoils, the main transport of Zn occurred in the form ofdissolved metal ions (Citeau et al., 2003). The ageing processleading to decrease metal accessibility would be difficult toquantify and, as shown by Seuntjens et al. (2001), it wouldconcern a minor fraction in real field situations. Besides, in

Table 2Stocks of Zn and Pb in different horizons of the CA(++) soil, in 2005 and after 50 yewith adjusted λ values and 100% adsorbed at chemical instantaneous equilibrium.

Metal reactivity hypothesis/horizons Soil depth, cm Zinc, kg ha−1

10/01/2005 31/12/205

Two-site model with adjusted λ valuesAp 0–33 2098.8 1433.4B1 33–45 439.1 438.8B2 45–80 308.2 566.9C 80–100 132.1 265.4Total 0–100 2978.2 2704.5

100% at equilibriumAp 0–33 2098.8 1222.3B1 33–45 439.1 566.5B2 45–80 308.2 819.5C 80–100 132.1 252.4Total 0–100 2978.2 2860.7

our work, this process is globally considered by usingadjusted kinetic constants in the Hydrus-2D model.

2.5. Modeling exercises and sensitivity tests

A great number of simulation exercises were run andparameterizationwas optimized before presenting final resultsin the present work. Such preliminary work was time- andeffort-demanding and not detailed here. Some sensitivity testsneeded for this work, particularly those related to the mainadjustable parameter of the kinetics hypothesis were discussedpreviously in Mallmann et al. (2012a). Moreover, we runspecific tests for the simulations of this work, showing that thetotal amounts of Zn and Pb stored in the three soil profiles afterthe further 50 years had a low variation (less than 5%) whenwe used half or doubled values of the adjusted kinetic constant(λ).

3. Results and discussion

3.1. Simulating Zn and Pb transfers in the moderately contam-inated CA(++) soil

Results of simulations with Hydrus-2D of the movements ofZn and Pb in soil horizons and soil solution during the2005–2055 period for the CA(++) soil are presented in Table 2and Fig. 2. Under hypothesis (i), the two-site adsorption modelset with experimental β and adjusted λ values (Mallmann et al.,2012a) simulated a loss of Zn from the surface Ap horizon after50 years of about 30% (−665.4 kg ha−1) but such a lossreached 876.5 kg Zn ha−1 (>40%) under hypothesis (ii) of100% instantaneous equilibrium. The Ap horizon acted as asource of Zn for the underlying soil horizons, but Zn concentra-tions in the soil solution outflowing the surface horizon wereclearly smaller than under the hypothesis (ii) of instantaneousequilibrium, about twofold smaller in 2055 (Fig. 2a). Moreover,the maximum Zn concentration in the soil solution occurred atabout 50-cm depth, i.e., 2.5 mg l−1 under the two-site adsorp-tion hypothesis, in comparison to 4.4 mg l−1 with the hypoth-esis (ii). In the kineticmodel,when unpolluted rainwater entersthe profile, a limited desorption rate of Zn from the soil matrixinduces a lower concentration than following the equilibrium

ars simulated by Hydrus-2D model considering a two-site adsorption model

Lead, kg ha−1

5 Difference % 10/01/2005 31/12/2055 Difference %

−665.4 −31.7 459.28 459.49 0.21 0.05−0.3 −0.1 32.48 32.94 0.45 1.37258.6 83.9 76.87 76.74 −0.13 −0.17133.4 101.0 40.94 41.09 0.16 0.38

−273.7 −9.2 609.57 610.26 0.68 0.11

−876.5 −41.8 459.28 459.24 −0.04 −0.01127.4 29.0 32.48 33.21 0.73 2.20511.3 165.9 76.87 76.58 −0.29 −0.38120.3 91.1 40.94 41.20 0.26 0.64

−117.5 −3.9 609.57 610.23 0.66 0.11

Zn in soil solution, mg l-1

0 1 2 3 4 5S

oil d

epth

, cm

0

10

20

30

40

50

60

70

80

90

100

20052055 - at equilibrium2055 - two site

Total Zn, mg kg-1

0 100 200 300 400 500

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

Pb in soil solution, µg l-1

0 1 2 3 4 5

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

Total Pb, mg kg-1

0 25 50 75 100 125

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

a b

c d

Fig. 2. Distribution of solution and total concentrations of zinc and lead in a moderately contaminated arable soil profile (CA(++)) measured in 2005 andsimulated by Hydrus-2D for 2005–2055 using models following instantaneous equilibrium or two-site adsorption with adjusted λ values. a) Zn concentration insolution, b) total soil Zn concentration, c) Pb concentration in solution, d) total soil Pb concentration.

59D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

hypothesis. Then, as soon as this element runs into a horizonwith a lower concentration of Zn in solution, it is adsorbed, butless efficiently than following a complete equilibrium hypoth-esis. Hence, the simulation with the two-site model consideringa kinetic fraction leads to a reduced metal transfer from the topto the lower part of the Ap horizon, and to the subsurfacehorizons (Fig. 2b). At the lower limit of the Ap horizon, the Znconcentration in the soil solution, which was in 2005 muchhigher than at the top of the B1 horizon, tends to become closeto that 2005 Zn solution concentration of the B1 horizon(Fig. 2a). Consequently, the B1 horizon is simply “crossed” by

the Zn coming from the surface horizon (Fig. 2, Table 2). In theB2 horizon, the simulated Zn concentration in the soil solutionusing the two-site model was lower than that simulated atinstantaneous equilibrium, but bothwere higher than the initialconcentration. This B2 horizon acts as a sink, under bothhypotheses, but Zn interception was lower with the two-sitemodel. Finally, at the bottom of the profile, the two-site modelsimulated larger Zn transfers to the C horizon and to depths of>1 m than with the equilibrium hypothesis (Table 2), linked tohigher concentrations in solution in this deep soil horizon(Fig. 2a).

60 D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

In terms of metal stocks in horizons, the displaced Zn wasre-adsorbed in deeper horizons (Table 2), notably the moreiron and clay rich B2 (+258.6 kg ha−1) and C horizon(+133.4 kg ha−1), whereas the Zn concentration of the B1horizon remained unchanged. By comparison, under thehypothesis (ii) of 100% instantaneous equilibrium between themetal elements and the soil constituents, and the accumulatedZn amounts in the B1, B2, and C horizons would reach +127.4,+511.3, and +120.3 kg ha−1, respectively. With a view togeneral statements on a slow transfer in agricultural soils of Znoriginating from atmospheric metal fallout contamination todeeper soil horizons and aquifers (McBride et al., 1997), oursimulations under hypothesis (i) were considered as morerealistic. In particular, a more reduced decrease of the Znconcentration in the surface horizon is more consistent with itsenhanced retention in agricultural plow layers under arableland, due to a strong interaction with organic and mineralconstituents and favored by liming and fertilizing practices(Leguédois et al., 2004; McBride et al., 1997). Finally, the overallloss of Zn from the soil profile (>1-m depth) in 2055 was b10%of the initial soil Zn stock (about 9% under hypothesis (i), and 4%under hypothesis (ii)).

For Pb, the simulations run under both hypotheses showedonly little variations in concentrations neither in the soilhorizons nor in the solution (Table 2, Fig. 2c,d). The estimatedPb outflow at −1-m depth was lower than the estimatedatmospheric Pb input (2.7 μg Pb l−1, i.e., 1.2 kg ha−1) duringthe considered period of 50 years, but both the output andinput amounts were small with respect to the accumulated Pbstocks in the moderately contaminated CA(++) soil (Table 2).Such findings are consistent with the very lowmobility of leadobserved in soils under arable land use, and generally ascribedto the high affinity of lead for organic matter and phosphates,and a high soil pH maintained by agricultural practices. Due tosuch lowPb concentrations in the soil solution, the variations ofthe Pb stocks in soil horizons for simulation under hypothesis(i) were small: +0.21 kg ha−1 (+0.05%) in the Ap, +1.37% inthe B1, –0.17% in the B2, and +0.38% in the C horizons. Suchredistributions among the different soil horizons were smallerthanwhen performing simulations under the hypothesis (ii) ofinstantaneous equilibrium. Under hypothesis (ii), simulationsrevealed a negative balance of −0.04 kg ha−1 for the Aphorizon (Table 2), but an overall increase of+0.66 kg Pb ha−1

for the total 1-m deep soil profile, which is very similar towhatwas found under hypothesis (i).

3.2. Simulation of Zn and Pb transfers in low contaminated soils

3.2.1. The CA(+) soilBetween 2005 and 2055, the soil solution Zn concentration

in the upper part of the Ap horizon decreased. As observed forthe CA(++) soil, the trend of the Zn concentration profile wasdiffered following the considered hypothesis of chemicalequilibrium. In the Ap horizon, Zn solution concentrationswere smaller for simulations with the two-site model (Fig. 3a).Below the Ap horizon, the concentration of Zn in the soilsolution was found close to the initial 2005 average Znconcentration used in the simulations. Consequently, thesimulations predicted a limited transfer of Zn from the upperto the lower part of the horizon (Fig. 3b), and only small Znamounts were transferred to deeper horizons (≈2% of the Zn

stock of the Ap horizon, under both hypotheses, Table 3). Thesimulated concentration of Zn in the soil solution of the B1horizon decreased, mainly in its lower part, and concomitantlyincreased in the upper part of the B2 horizon, enhancing the Zntransfer between these two horizons (Fig. 3b). A small part ofthe downward moving Zn was adsorbed in the Cg1 horizon,simulated under both chemical hypotheses. Finally, the Cg2horizon, due to its higher contents of clay (28%) and iron oxides(≈4.5%), a nearly neutral pH (6.7) as well as a fairly high Zncontent in 2005 (≈40 mg kg−1, Table 1), was found to act as aZn source for a depth of >1 m. Such Zn loss from the soil waslarger under the hypothesis of 100% instantaneous equilibrium(Table 3).

Unlike findings for the CA(++) soil, in the lowermetal-contaminated CA(+) soil, three horizons acted as asource for Zn downward migration (Ap, but also the B1 andC2g horizons), whereas the B2 and C1g horizons had a role ofZn accumulating sinks, for simulations under both hypothesesof chemical equilibrium. Yet, themagnitude of gains and lossesin each horizon was generally larger under the 100% instanta-neous equilibrium hypothesis than what was observed withthe two-site model, with total downward movements of 23.6and 17.6 kg Zn ha−1, and internal redistribution of 14.4and 10.5 kg Zn ha−1, respectively (Table 3). The final Zn lossfrom the soil (>1-mdepth)was small and varied little betweenmodeling under hypotheses (i) and (ii):−7.1 kg ha−1 (−0.8%)and−9.2 kg ha−1 (−1.0%), respectively.

For Pb, the simulations run under both hypotheses in theCA(+) soil revealed very small changes in the soil solutionmainly at the interface with the atmosphere (Fig. 3c) due toPb input via rainwater, and minor variations at the transitionof Ap–B1 and B1–B2 horizons. Without plowing, the currentPb deposit remained in the first centimeters of the soil. Onlysmall transfers occurred from the lower part of the Ap to theupper part of the B1 horizon and from the lower part of theB1 to the upper part of the B2 horizon (Fig. 3d). Consequent-ly, the total amount of Pb in the profile will slightly increasein 2055, particularly in the B1 horizon (Table 3). At −1 m,low amounts of Pb are lost from the soil, under bothhypotheses. Such small simulated Pb transfers to depthwere consistently lower than past exogenous Pb movementsduring the 20th century, which were estimated at ≈7.5% byFernandez et al. (2007) between the Ap and B2 horizons.

3.2.2. The PP(+) soilIn the PP(+) soil, Zn concentrations in solution were higher

in all soil horizons, under both hypotheses (Fig. 4a) than in theCA(+) soil (Fig. 3a), mainly ascribed to lower pH values in thepermanent grassland soil (Table 1). Under the hypothesis of100% instantaneous equilibrium, the Zn concentrations insolution were slightly higher than with the two-site modeluntil 60 cm-depth (Fig. 4a). In all A horizons (A11, A12, ABand ACg), the simulated Zn solution concentrations tendedto decrease between 2005 and 2055 (Fig. 4a), as did thecorresponding Zn stocks (Table 4). The large difference ofinitial Zn solution concentrations between the ACg and Cg2horizon enhanced consistent Zn movements towards the C2ghorizon.

Overall budgeting following the model at instantaneousequilibriumdemonstrates that about 56%of the 28.0 kg Zn ha−1

desorbed from the A horizons (6.5+4.9+2.4+14.2) is

Zn in soil solution, µg l-1

0 30 60 90 120 150S

oil d

epth

, cm

0

10

20

30

40

50

60

70

80

90

100

20052055 - at equilibrium2055 - two site

Total Zn, mg kg-1

0 30 60 90 120 150

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

Pb in soil solution, µg l-1

0 1 2 3 4

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

Total Pb, mg kg-1

0 20 40 60 80

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

a b

c d

Fig. 3. Distribution of solution and total concentrations of zinc and lead in a low-contaminated arable soil profile (CA(+)) measured in 2005 and simulated byHydrus-2D for 2005–2055 using models following instantaneous equilibrium or two-site adsorption with adjusted λ values. a) Zn concentration in solution,b) total soil Zn concentration, c) Pb concentration in solution, d) total soil Pb concentration.

61D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

adsorbed at the upper part of the Cg2 horizon (15.8 kg ha−1)and 12.2 kg ha−1 is lost from the soil profile (Table 4). Using thetwo-sitemodel, Zn concentrations in solution at the lower part ofthe ACghorizon and at the top of the Cg2 horizon are higher thanunder hypothesis (ii) due to the influence of upper horizons andthe uncompleted sorption on Cg2 constituents. Consequently,the amount of Zn intercepted in the Cg2 horizon (3.6 kg ha−1) isonly 17.5% of the total Zn loss of the upper horizons. In addition,83% (17.1 kg Zn ha−1) is moved to a soil depth of >1 m,representing about 1.9% of the total Zn stock in the first meter

(Table 4). Such a loss was almost 2.5 times the Zn loss observedfor the CA(+) soil. This higher Zn mobility in PP(+) A horizons,affected by bioturbation, with respect to the CA(+) soil is inagreement with the findings on increased Zn extractabilityinduced by a high earthworm activity (Cheng and Wong, 2002;Fernandez et al., 2010; Wen et al., 2004) and a lower soil pHvalue. Furthermore, the intensive earthworm activity willphysically incorporate all solid and sorbed species to depth, andthe predictionwith the two-sorption site transportmodel shouldbe considered as a scenario of minimal mobility.

Table 3Stocks of Zn and Pb in 2005 in different horizons of the CA(+) soil and after 50 years simulated by Hydrus-2D model considering a two-site adsorption model withadjusted λ values and 100% adsorbed at chemical instantaneous equilibrium.

Metal reactivity hypothesis/horizons Soil depth, cm Zinc, kg ha−1 Lead, kg ha−1

10/01/2005 31/12/2055 Difference % 10/01/2005 31/12/2055 Difference %

Two-site model with adjusted λ valuesAp 0–26 414.0 405.0 −9.0 −2.2 219.31 219.33 0.02 0.01B1 26–44 192.3 186.8 −5.5 −2.8 36.88 37.69 0.81 2.15B2 44–72 164.5 173.9 9.4 5.7 45.02 45.19 0.17 0.37Cg1 72–87 66.4 67.5 1.1 1.6 22.09 22.10 0.01 0.04Cg2 87–100 90.4 87.4 −3.1 −3.4 22.16 22.10 −0.06 −0.27Total 0–100 927.6 920.6 −7.1 −0.8 345.45 346.40 0.95 0.27

100% at equilibriumAp 0–26 414.0 405.4 −8.6 −2.1 219.31 219.04 −0.27 −0.12B1 26–44 192.3 184.1 −8.2 −4.3 36.88 37.83 0.96 2.54B2 44–72 164.5 175.9 11.4 7.0 45.02 45.19 0.17 0.38Cg1 72–87 66.4 69.4 3.0 4.5 22.09 22.13 0.04 0.17Cg2 87–100 90.4 83.7 −6.8 −7.5 22.16 22.00 −0.17 −0.77Total 0–100 927.6 918.5 −9.2 −1.0 345.45 346.19 0.73 0.21

62 D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

For Pb, the variations of solution concentrations andtransfers between horizons of the PP(+) soil were small, andcomparable to values simulated for the CA(+) soil. However,the changes of the concentrations in the soil solution at theinterface between the horizons were more pronounced andvisible all along the soil profile (Fig. 4c,d). As for Zn, thishigher mobility of Pb can be related to a higher extractabilityobserved in soils with high earthworm activity (Fernandezet al., 2010) and lower soil pH, and possibly to the presenceof dissolved organic matter (Jordan et al., 1997). Additionally,the saturated hydraulic conductivity is higher in this grasslandsoil compared to the soils under arable land (Mallmann et al.,2012a). Nevertheless, the stock of Pb in each horizon hardlyvaries during the 50 years simulated. No losses of Pb from theprofile (>1 m) were estimated by simulations under bothhypotheses (Table 4): due to atmospheric Pb inputs by rainfallduring the 50 years, the two hypotheses showed a gain of0.99 kg Pb ha−1. Yet, the increasing Pb amounts in the Cg2horizon (+1.38% for the two-sitemodel and+2.01% under thehypothesis of instantaneous equilibrium) corroborate findingsof Fernandez et al. (2008) using Pb isotopic compositions, whoconcluded that anthropogenic lead clearly moved to depths of>80 cm. Finally, lead transfer in long-term (>100 years)grassland soils, in addition to higher Pb concentrations in thesoil's solution, is also explained by the mechanical incorpora-tion of soil particles from the surface horizons to the depth dueto the activity of earthworms (Fernandez et al., 2010; Nahmaniet al., 2003).

3.3. Metal movement and risk of groundwater contamination

During the 50-year simulation period, the Zn contaminationplume deepens (Figs. 2, 3 and 4), notably in the CA(++) soil.The Zn concentrations in the soil solution at−1-mdepth of theCA(++), CA(+) and PP(+) profiles, predicted for 2055 by theHydrus-2D model under the two-site hypothesis were 1.56,0.03 and 0.07 mg l−1 (Table 5), in comparison to 0.89, 0.04 and0.07 mg l−1, for the100% at instantaneous chemical equilibri-um hypothesis, respectively. Table 5 shows that for the CA(++)

soil, Zn concentrations in solution at −1-m soil depth in 2055

continuously increased with respect to the initial 2005 Znconcentrations. Despite such a threefold increase of Zn insolution, its 2055 concentration remained under limit levels fordrinking water (5.0 mg Zn l−1 — France, 1989). Yet, it isremarkable to see that in 2055, about 130 years after the mainperiod (1910–1930) of themetal fallout deposition (Mallmannet al., 2012a) the Zn concentration in solution at −1-m depthstill will increase. In the low contaminated soils, such Znconcentration in solution at −1-m depth remained stable, orslightly decreased after 2015. Cerník et al. (1994), using amathematical model of reactive transport to estimate the Znmigration in a soil profile contaminated by atmosphericdeposition found a low amount of zinc transferred to thegroundwater even after 300 years. In addition, the effects offuture climate change in Western Europe for sandy soils werereported to project lowered Zn and Cd concentrations insurface waters (Visser et al., 2012). Our soils have low clayand oxide contents, but present nearly neutral pH values dueto their agricultural management. Consequently, the smallamounts of Zn reaching the groundwater will only little affectthis resource, contrarily to soils with very low pH values suchasmetal contaminated forest soils,where amajor part of the Zndeposited in the surface layers was already transferred below1-m depth (van Oort et al., 2009). Yet, considering our workfocusing on low and moderately contaminated soils, and thestill increasing Zn concentrations in solution at−1-m depth inthe CA(++) soil, our findings raise questions about the risks ofgroundwater contamination in more strongly polluted soils,occurring more close to the former metallurgical plant, mostoften under a private garden, or a poplar stand (van Oort et al.,2009) and more acidified as arable land soils. Beyer et al.(2009) predicted concentrations of Cd that aremore exceedingthe sanitary limit, leaching down from pastures contaminatedby a metallurgic plant, but with acid surface horizons(pHb5.5). Degryse and Smolders (2006) also obtainedalarming experimental and calculated concentrations of Cdand Zn but, once again, for strongly acidified soils.

For Pb, the simulations with Hydrus-2D revealed nosignificant alterations of its concentration in the soil solutionfor the next 50 years (Table 5), in any part of the soil profiles.

Zn in soil solution, µg l-1

0 50 100 150 200 250S

oil d

epth

, cm

0

10

20

30

40

50

60

70

80

90

100

20052055 - at equilibrium2055 - two site

Total Zn, mg kg-1

0 20 40 60 80 100

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

Pb in soil solution, µg l-1

0.0 1.5 3.0 4.5 6.0

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

Total Pb, mg kg-1

0 15 30 45 60

Soi

l dep

th, c

m

0

10

20

30

40

50

60

70

80

90

100

a b

c d

Fig. 4. Distribution of solution and total concentrations of zinc and lead in a low-contaminated permanent pasture soil profile (PP(+)) measured in 2005 andsimulated by Hydrus-2D for 2005–2055 using models following instantaneous equilibrium or two-site adsorption with adjusted λ values. a) Zn concentration insolution, b) total soil Zn concentration, c) Pb concentration in solution, d) total soil Pb concentration.

63D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

The simulated values were always b6.0 μg l−1, far belowmaximum lead concentrations reported by the Frenchlegislation of water quality (50.0 μg l−1 — France, 1989).

4. Conclusions

We applied a Hydrus-2D two site model under thehypothesis of kinetically governed chemical reactions be-tween metals and the soil solid phase, recently validated byMallmann et al. (2012a), to simulate the 2005–2055-changesin the Zn and Pb concentration profiles in three agricultural

soils under distinctly different long term land use, contam-inated by metallurgical fallout predominantly during the1910–1930s. The results were compared with the simula-tions under the hypothesis of 100% of instantaneousequilibrium. To our knowledge, it is the first time that sucha validated model on real situations, including repartitioncoefficients issued from laboratory EDTA extractions andkinetic parameters proportionally adjusted to field condi-tions, was used for prognostic modeling of field data. Ourmain work findings are of potential use for decision makers,not only in France but also elsewhere.

Table 4Stocks of Zn and Pb in 2005 in different horizons of the PP(+) soil and after 50 years simulated by Hydrus-2D model considering a two-site adsorption model withadjusted λ values and 100% adsorbed at chemical instantaneous equilibrium.

Metal reactivity hypothesis/horizons Soil depth, cm Zinc, kg ha−1 Lead, kg ha−1

10/01/2005 31/12/2055 Difference % 10/01/2005 31/12/2055 Difference %

Two-site model with adjusted λ valuesA11 0–6 51.8 47.1 −4.7 −9.2 32.35 33.02 0.67 2.04A12 6–26 235.8 228.4 −7.4 −3.1 154.50 153.53 −0.97 −0.63AB 26–53 230.6 227.7 −2.9 −1.3 68.82 69.56 0.75 1.07ACg 53–76 187.0 181.5 – 5.5 −2.9 27.36 27.65 0.29 1.06Cg2 76–100 171.1 174.7 3.6 2.1 17.24 17.48 0.24 1.38Total 0–100 876.3 859.4 −17.1 −1.9 300.26 301.25 0.99 0.33

100% at equilibriumA11 0–6 51.8 45.3 −6.5 −12.5 32.35 33.01 0.66 2.01A12 6–26 235.8 230.9 −4.9 −2.1 154.50 153.36 −1.13 −0.74AB 26–53 230.6 228.2 −2.4 −1.1 68.82 69.67 0.85 1.23ACg 53–76 187.0 172.8 −14.2 −7.6 27.36 27.61 0.25 0.91Cg2 76–100 171.1 186.9 15.8 9.3 17.24 17.59 0.35 2.01Total 0–100 876.3 864.1 −12.2 −1.4 300.26 301.25 0.99 0.33

64 D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

For the moderately contaminated soil under arable landuse, a consistent movement of Zn was predicted: >30% of the2005 Zn stock in the Ap horizonmoved to greater depth, and in2055, about 10% loss of the total Zn stock of the 1-m soil profiletowards the groundwater. For this soil, the simulations ofchanging Zn concentration profiles were found more realisticwhen using the two-site model with a kinetic part than underthe hypothesis of 100% instantaneous equilibrium, in particularwith respect to the future decrease of Zn contents in the surfaceAp horizon. For Pb in the moderate, and for Zn and Pb inthe two low-contaminated soils, simulations under bothhypotheses were found to be little different. In the twolow-contaminated soils, despite comparable initial metalfallout inputs, the metal concentrations in the soil solutionwere consistently larger under grassland than under arableland use, a two-fold for Zn and 1.5-fold for Pb, particularly inthe upper 60–70 cm, abundantly reworked by earthworms.Yet, metal movements in the grassland soils will be even moreimportant, since biological perturbation was not considered inour models.

Considering that themaximal pollutant deposition occurredduring the early decennia of the 20th century, our work reportsnew data on the fate of trace metals in soil under agricultural

Table 5Decennial mean Zn and Pb concentrations in soil solution at −100-cm depth, calcmodel with adjusted λ values and 100% adsorbed at chemical instantaneous equili

Soil Hypothesis Year

2005 2015

Zn concentration (mg l−1)CA(++) Two-site 0.500 0.841

100% equilibrium 0.500 0.504CA(+) Two-site 0.059 0.028

100% equilibrium 0.059 0.049PP(+) Two-site 0.096 0.074

100% equilibrium 0.096 0.078Pb concentration (μg l−1)

CA(++) Two-site 1.620 1.620100% equilibrium 1.620 1.620

CA(+) Two-site 0.760 0.702100% equilibrium 0.760 0.735

PP(+) Two-site 0.690 0.624100% equilibrium 0.690 0.659

land use, more than 100 years after the main soil pollutionperiod. Such data are little available in literature. The simulatedsoil outflow solution concentrations (>1-m soil depth) for Znwere predicted to continuously increase in the moderatelycontaminated soil until 2055, i.e., aftermore than 130 years, butthey tended to decrease slightly in the low contaminated soils,as soon as 2015. Both Zn and Pb outflow solution concentra-tions for the next 50 years were found to remain below Frenchthreshold levels for drinking water.

Our findings on increasing Zn concentrations in themoderately contaminated agricultural soil raise questionsfor risks of metal contamination of groundwater in morestrongly polluted soils, or under more acidified, wooded land,where the absence of fertilizing practices will not havereducing metal mobility effects.

Acknowledgments

The authors greatly acknowledge Sebastien Breuil ofINRA-Versailles for help with soil sampling and samplepreparation, François Lafolie of INRA-Avignon and DalvanJosé Reinert and Maria Alice Santanna — UFSM/Brazil for

ulated for the studied 2005–2055 period, considering a two-site adsorptionbrium.

2025 2035 2045 2055

1.089 1.288 1.439 1.5580.559 0.636 0.715 0.8920.027 0.027 0.027 0.0270.046 0.044 0.043 0.0410.074 0.073 0.072 0.0720.073 0.070 0.068 0.066

1.620 1.620 1.620 1.6201.620 1.620 1.620 1.6200.698 0.693 0.689 0.6860.724 0.716 0.709 0.7040.606 0.595 0.588 0.5820.646 0.637 0.630 0.623

65D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

their much constructive discussion on water fluxes in soils,and Jirka Šimůnek for his helpful advice.

References

Afnor, 2004. Évaluation de la qualité des sols. Recueil Normes etRéglementation. Méthodes d'analyse chimique, 1. AFNOR, Paris.

Arias, M., Pérez-Novo, C., Osorio, F., Soto, E.L.B., 2005. Adsorption anddesorption of copper and zinc in the surface layer of acid soils. Journal ofColloid and Interface Science 288, 21–29.

Bataillard, P., Cambier, P., Picot, C., 2003. Short term transformations of leadand cadmium compounds in soil after contamination. European Journalof Soil Science 54, 365–376.

Bermond, A., Yousfi, I., Ghestem, J.P., 1998. Kinetic approach to the chemicalspeciation of trace metals in soils. Analyst 123, 785–789.

Beyer, C., Altfelder, S., Duijnisveld, W.H.M., Streck, T., 2009. Modelling spatialvariability and uncertainty of cadmium leaching to groundwater in anurban region. Journal of Hydrology 369, 274–283.

Bruand, A., Duval, O., Cousin, I., 2004. Estimation des propriétés de rétentionen eau des sols à partir de la base de données SOLHYDRO: une premièreproposition combinant le type d'horizon, sa texture et sa densitéapparente. Étude et Gestion des Sols 11, 323–332.

Buchter, B., Davidoff, B., Amacher, M.C., Hinz, C., Iskandar, I.K., Selim, H.M.,1989. Correlation of Freundlich Kd and n retention parameters with soilsand elements. Soil Science 148, 370–379.

Carrillo-González, R., Šimůnek, J., Sauvé, S., Adriano, D., 2006. Mechanismsand pathways of trace element mobility in soils. Advances in Agronomy91, 111–178.

Cerník, M., Federer, P., Borkovec, M., Sticher, H., 1994. Modelling of heavymetal transport in a contaminated soil. Journal of Environmental Quality23, 1239–1248.

Charbeneau, R.J., Linz, D.G., Newell, C.J., Rixey, W.G., Ryan, J.A., 2003.Transport of contaminants in soil. In: Lanno, R.P. (Ed.), ContaminatedSoil: From Soil–Chemical Interactions to Ecosystem Management.SETAC, Pensacola — USA, pp. 217–249.

Cheng, J., Wong, M.H., 2002. Effects of earthworms on Zn fractionation insoils. Biology and Fertility of Soil 36, 72–78.

Citeau, L., 2004. Etude de colloïdes naturels présents dans les eauxgravitaires de sols contaminés: relation entre nature des colloïdes etréactivité vis-à-vis des métaux (Zn, Cd, Pb, Cu). Doctoral thesis, INA-PG,Paris.

Citeau, L., Lamy, I., van Oort, F., Elsass, F., 2003. Colloidal facilitated transfer ofmetals in soils under different land use. Colloids and Surfaces A:Physicochemical and Engineering Aspects 217, 11–19.

Degryse, F., Smolders, E., 2006. Mobility of Cd and Zn in polluted andunpolluted Spodosols. European Journal of Soil Science 57, 122–133.

Escarré, J., Lefèbvre, C., Raboyeau, S., Dossantos, A., Gruber, W., Cleyet-Marel,J.C., Frérot, H., Noret, N., Mahieu, S., Collin, C., van Oort, F., 2010. Heavymetal concentration survey in soils and plants of the Les Malines miningdistrict (Southern France): implications for soil restoration. Water, Air,and Soil Pollution 216, 485–504.

Fangueiro, D., Bermond, A., Santos, E., Carapuça, H., Duarte, A., 2005. Kineticapproach to heavy metal mobilization assessment in sediments: chooseof kinetic equations and models to achieve maximum information.Talanta 66, 844–857.

Fernandez, C., Labanowski, J., Cambier, P., Jongmans, A.G., van Oort, F., 2007.Fate of airborne metal pollution is soils as related to agriculturalmanagement. 1. Zn & Pb in soil profiles. European Journal of Soil Science58, 547–559.

Fernandez, C., Monna, F., Labanowski, J., Loubet, M., van Oort, F., 2008.Anthropogenic lead distribution in soils under arable land and permanentgrassland estimated by Pb isotopic compositions. Environmental Pollution156, 1083–1091.

Fernandez, C., Labanowski, J., Jongmans, A.G., Bermond, A., Cambier, P., Lamy,I., van Oort, F., 2010. Fate of airborne metal pollution in soils as related toagricultural management: 2. Assessing the role of biological activity inmicro-scale Zn and Pb distributions in A, B and C horizons. EuropeanJournal of Soil Science 61, 514–524.

France. Décret no 89–3 du 3 janvier 1989. Relatif aux eaux destinées àla consommation humaine à l'exclusion des eaux minérales naturelles(J.O. du 4 janvier 1989). Available in: bhttp://www.mon-immeuble.com/Lois/decret89-3du3.01.1989.htm>. Accessed at: 19 Jan. 2009.

Goldberg, S., Criscenti, L.J., Turner, D.R., Davis, J.A., Cantrell, K.J., 2007.Adsorption–desorption processes in subsurface reactive transportmodeling. Vadose Zone Journal 6, 407–435.

Hardy, O., 1970. Croissance et déclin d'une implantation industrielle au XXesiècle: le zinc dans le pays de Saint-Amand. La compagnie franco-belgede Mortagne 1905–1948. (92 pp.).

IUSSWorking group WRB, 2006. World reference base for soil resources 2006,World Resources Reports No. 103, 2nd edition. FAO, Rome. (128 pp.).

Jacques, D., Šimůnek, J., Mallants, D., van Genuchten, M.Th., 2008. Modelingcoupled hydrologic and chemical processes: long-term uranium trans-port following phosphorus fertilization. Vadose Zone Journal 7, 698–711.

Jardine, P.M., Mehlhorn, T.L., Bailey, W.B., Brooks, S.C., Fendorf, S., Gentry,R.W., Phelps, T.J., Saiers, J.E., 2011. Geochemical processes governing thefate and transport of chromium(III) and chromium(VI) in soils. VadoseZone Journal 10, 1058–1070.

Jarvis, N.J., 2007. A review of non-equilibrium water flow and solute transportin soil macropores: principles, controlling factors and consequences forwater quality. European Journal of Soil Science 58, 523–546.

Jordan, R.N., Yonge, D.R., Hathhorn, W.E., 1997. Enhanced mobility of Pb inthe presence of dissolved natural organic matter. Journal of ContaminantHydrology 29, 59–80.

Labanowski, J., Sebastia, J., Foy, E., Jongmans, A.G., Lamy, I., van Oort, F., 2007.Fate of metal-associated POM in a soil under arable land use contaminatedby metallurgical fallout in northern France. Environmental Pollution 149,59–69.

Labanowski, J., Monna, F., Bermond, A., Cambier, P., Fernandez, C., Lamy, I.,van Oort, F., 2008. Kinetic extractions to assess mobilization of Zn, Pb,Cu, and Cd in a metal-contaminated soil: EDTA vs. citrate. EnvironmentalPollution 152, 693–701.

Lair, G.J., Gerzabek, M.H., Haberhauer, G., Jakusch, M., Kirchamnn, H., 2006.Response of the sorption behaviour of Cu, Cd, and Zn to different soilmanagement. Journal of Plant Nutrition and Soil Science 169, 60–68.

Leguédois, S., van Oort, F., Jongmans, T., Chevallier, P., 2004. Morphology,chemistry and distribution of neoformed spherulites in agricultural landaffected by metallurgical point-source pollution. Environmental Pollu-tion 130, 135–148.

Mallmann, F.J.K., Rheinheimer dos Santos, D., Cambier, P., Labanowski, J.,Lamy, I., Santanna, M.A., Tessier, D., van Oort, F., 2012a. Using a two site-reactive model for simulating one century changes of Zn and Pbconcentration profiles in soils affected by metallurgical fallout. Environ-mental Pollution 162, 294–302.

Mallmann, F.J.K., Rheinheimer dos Santos, D., Ceretta, C.A., Cella, C., Šimůnek,J., van Oort, F., 2012b. Modeling field-scale vertical movement of zincand copper in a pig slurry-amended soil in Brazil. Journal of HazardousMaterials http://dx.doi.org/10.1016/j.jhazmat.2012.10.022.

McBride, M., Sauvé, S., Hendershot, W., 1997. Solubility control of Cu, Zn, Cd,and Pb in contaminated soils. European Journal of Soil Science 48, 337–346.

Nahmani, J., Lavelle, P., Lapied, E., van Oort, F., 2003. Effects of heavy metal soilpollution on earthworm communities in the north of France. Pedobiologia47, 663–669.

Sauvé, S., Hendershot, W., Allen, H.E., 2000. Solid-solution partitioning ofmetals in contaminated soils: dependence on pH, total metal burden, andorganic matter. Environmental Science & Technology 34, 1125–1131.

Selim, H.M., 2002. Modeling the transport and retention of inorganic in soils.Advanced Agronomy 47, 331–385.

Seuntjens, P., Tirez, K., Šimůnek, J., van Genuchten, M.Th., Cornelis, C.,Geuzens, P., 2001. Ageing effects on cadmium transport in undisturbedcontaminated sandy soil columns. Journal of Environmental Quality 30,1040–1050.

Shipitalo, M.J., Dick, W.A., Edwards, W.M., 2000. Conservation tillage andmacropore factors that affect water movement and the fate of chemicals.Soil & Tillage Research 53, 167–183.

Šimůnek, J., Sejna, M., van Genuchten, M.Th, 1999. The HYDRUS-2D softwarepackage for simulating the two-dimensional movement of water, heat,and multiple solutes in variably-saturated media. Version 2.0 IGWMC-TPS 53. International GroundWater Modeling Center, Colorado School ofMines, Golden — CO.

Sposito, G., 1989. The Chemistry of Soils. New York, Oxford.Streck, T., Richter, J., 1997. Heavy metal displacement in a sandy soil at the

field scale: II. Modeling. Journal of Environmental Quality 26, 56–62.van der Grift, B., Griffioen, J., 2008. Modelling assessment of regional

groundwater contamination due to historic smelter emissions of heavymetals. Journal of Contaminant Hydrology 96, 48–68.

van Oort, F., Jongmans, A.G., Citeau, L., Lamy, I., Chevallier, P., 2006. Metaltransport dynamics in soils as revealed by microscale zinc and leaddistribution patterns in subsurface horizons. European Journal of SoilScience 57, 154–166.

van Oort, F., Labanowski, J., Jongmans, T., Thiry, M., 2007. Le devenir despolluants métalliques dans les sols: révélateur d'impacts de l'activitéhumaine sur la pédogenèse? Étude et Gestion des Sols 14, 287–303.

van Oort, F., Jongmans, A.G., Lamy, I., Baize, D., Chevallier, P., 2008. Impacts oflong-term waste-water irrigation on the development of sandy luvisols:consequences for metal pollutant distributions. European Journal of SoilScience 59, 925–938.

vanOort, F., Thiry,M., Jongmans, A.G., Bourennane,H., Cambier, P., Lamy, I., Citeau,L., Nahmani, J., 2009. Pollutionsmétalliques: distributions hétérogènes de Zn,

66 D. Rheinheimer dos Santos et al. / Journal of Contaminant Hydrology 145 (2013) 54–66

Pb, Cd, et Cu et relations avec l'usage des sols. In: Cambier, P., Schvartz, C., vanOort, F. (Eds.), Contaminationsmétalliques des agrosystèmes et écosystèmespéri-industriels. Editions Quae, Versailles, France, pp. 15–44.

Visser, A., Kroes, J., van Vliet, M.T.H., Blenkinsop, S., Fowler, H.J., Broers,H.P., 2012. Climate change impacts on the leaching of a heavy metal

contamination in a small lowland catchment. Journal of ContaminantHydrology 127, 47–64.

Wen, B., Hu, X.Y., Liu, Y., Wang, W.S., Feng, M.H., Shan, X.Q., 2004. The role ofearthworms (Eisenia fetida) in influencing bioavailability of heavymetals in soils. Biology and Fertility of Soil 40, 181–187.