distribution of cd, ni, cr, and pb in amended soils from alicante province (se, spain)

Distribution of Cd, Ni, Cr, and Pb in Amended Soilsfrom Alicante Province (SE, Spain)

Francisco Pardo & Manuel Miguel Jordán &

Teófilo Sanfeliu & Silvia Pina

Received: 17 March 2010 /Accepted: 11 August 2010 /Published online: 25 August 2010# Springer Science+Business Media B.V. 2010

Abstract Heavy metals can be transferred from soils toother ecosystem parts and affect ecosystems and humanhealth through the food chain. Today the use ofbiosolids to improve the nutrient contents of a soil is acommon practice. Contamination of soils by potentiallytoxic elements (e.g., Cd, Ni, Cr, Pb) from amendmentsof biosolids is subject to strict controls within theEuropean Community in relation to total permissiblemetal concentrations, soil properties and intended use.In this context, heavy metal concentrations were studiedin agricultural soils devoted to vegetable crops in theprovince of Alicante (SE Spain), where an intensiveagriculture takes place. This study is aimed at ascertain-ing the chemical partitioning of Cd, Ni, Cr, and Pb inagricultural soils repeatedly amended with sludge.Selected soil properties relevant to control the mobilityand bioavaibility of heavy metals were analyzed for thegeneral characterisation of these agricultural soils. Thedistribution of chemical forms of Cd, Ni, Cr, and Pb in

five biosolids-amended soils was studied using asequential extraction procedure that fractionates themetal into soluble-exchangeable, specifically sorbed-carbonate bound, oxidizable, reducible, and residualforms. The biosolids incorporation has modified the soilcomposition, leading to the increment of heavy metals.The residual, reducible, and carbonate-sorbed formswere dominant. Detailed knowledge of the soil at theapplication site, especially pH, CEC, buffering capacity,organic matter, clay minerals, and clay content, isessential.

Keywords Biosolids . Amended soils . Heavy metals .

Sequential extraction . SE Spain

1 Introduction

Agronomic practices and other sources of heavymetals (e.g., atmospheric deposition for Cd and Pb(Jordán et al. 1998)) may also have some influence oncrop accumulation. Given the relevance of horticul-tural crops in the Mediterranean diet, it is highlynecessary to extend the experience of this work toother areas of the European Mediterranean region.

The sewage sludge (biosolids) can be used as soilamendments and fertilizers. The biosolid term wasofficially recognized in 1991 by the Water Environ-ment Federation (WEF). The chemical composition ofthe biosolids is quite variable and it depends on the

Water Air Soil Pollut (2011) 217:535–543DOI 10.1007/s11270-010-0607-6

F. Pardo : T. SanfeliuDepartment of Agrarian Sciences and Environment,University Jaume I,Campus de Riu Sec s/n,12080 Castellón, Spain

M. M. Jordán (*) : S. PinaDepartment of Agrochemistry and Environment,University Miguel Hernandez,Elche. Avda. de la Universidad s/n,Elche, Alicante 03202, Spaine-mail: [email protected]

origin of the effluent and on the processes that sludgehas been subjected to. These processes will determinethe different quantities of the sludge inorganiccompounds (Sommers 1977), and thus the extent towhich those compounds are associated to the sludgeorganic fraction (Jordan et al. Jordán et al. 2006).There are many reviews surveys that develop astatistical research on the sludge composition. It isabout a sludge rich in organic matter and in someelements such as N and P. On the other hand, thebiosolids despites a high electric conductivity due toits high salt concentration (Navarro-Pedreño et al.1997). The origin of the effluent will determine thepresence of toxic elements and agents. Sewage sludgecoming from wide urban areas with a substantialindustrial influence, usually show higher concentra-tions of metals typical of factories, like Cr and Ni.

The application of biosolids on a culture soil is amethod which offers important benefits: firstly, thetransport and application costs are quite low (mostly if itis about dehydrated biosolids) in the case of culture soilslocated near the water treatment plant. Secondly, it ispossible to recycle fertilizers (N, P, and K) and organicmatter, by improving the physical and chemical featuresof the soil and by reducing the fertilizer costs. In fact, insome soil such as calcareous soils with low quantities ofFe, sludge may supply essential micronutrients (forinstance, Fe, Zn, Cu) even more efficaciously than thecommercial fertilizers (Hue 1995; McGrath et al. 2000;Kim et al. 2007). However, the use of biosolids mayalso have several problems, as the presence ofquantities of metals which could be toxic for plants,or which could contaminate ground-waters after beingleached (Richards et al. 1998; McLaren et al. 2004).More scientific studies have been conducted toinvestigate possible environmental and human healthrisks from the use of biosolids as soil amendments.These risks can be separated into short- and long-termrisks. Short-term risks are those that could result from asingle biosolids application, would occur within arelatively short period after biosolids application (daysto months), but generally would diminish within a shortperiod of time (less than a year). Such risks includeexcessively high soil pH, nutrient (NO3

− and PO43−)

leaching or runoff, and transfer of pathogens to farmanimals or humans. Long-term risks are those thatresult from repeated biosolids applications over manyyears and are associated primarily with the buildup oftrace elements in soils.

Much research on the depth-related distribution ofmetals through the profile of soils fertilized withbiosolids have shown that, in a short term, there is arelatively small downward movement of metals(Al-Solaimi 1987; McGrath 1987; Gebhardt et al.1988; Camobreco et al. 1996). In California, Williamset al. (1987) found that even after the application ofbiosolids up to a maximum of 1,800 dry matter tonsper hectare on a loam soil, Cd, Zn, Ni, Fe, and Cotend to remain in the zone of incorporation for a9-year period. Sludge used in the experiment caused aprogressive acidification with increasing rate ofapplication, but did not tend to increase metalmovement down the profile. With sludge applied tothe surface of grassland, Davis et al. (1988) found thatCd, Cr, Cu, Mo, Ni, Pb, and Zn moved into the top10 cm of the profile, with an average of 87% of themetals on the first 5 cm. In forest soils, Fiskell et al.(1984) found that most of the metals were limited tothe seven top centimetres of the profile of an acidsandy soil, although some downward movementcould be observed between the 6 and 30 months.

However, there are some authors suggesting ahigher degree of the movement of metals. Legret et al.(1988) found that, in a coarse textured soil which hadreceived several applications of sludge, Cd movedfrom the surface to depths of 60 to 80 cm, Ni to 40 to60 cm, Pb to 20 to 40 cm, but Cr remained in thesurface horizon. Juste and Solda (1977), working withthe same soil, stated that 3 years after the applicationof 100 dry matter tons per hectare of a sludgecontaining a high level of metal on an acid sandysoil, the concentrations of Cd, Cu, and Ni significant-ly increased in the horizons 0–20 and 20–40.

The level of pollution of soils by heavy metalsdepends on the retention capacity of the soil,especially on physicochemical properties (mineralogy,grain size, organic matter) affecting soil particlesurfaces and also on the chemical properties of themetal (Moral et al. 2005). These metals may beretained by soil components in the near surface soilhorizons or may precipitate or coprecipitate assulphides, carbonates, oxides or hydroxides withFe, Mn, and Ca (Adamo et al. 1996).

Several scientific studies currently focus on theincrease of heavy metal content in natural andagricultural soils, world-wide (Chang et al. 1992).Plant growth in fact may be affected by heavy metal,since a certain uptake of metals is likely to occur. In

536 Water Air Soil Pollut (2011) 217:535–543

most of cases, the transfer of metals to shoots isscarce, therefore toxic effects are observed on rootsmostly. Due to their heavy metal content, wastebiomasses are the main source of pollution. Moreover,the use of sludge and slurries in agriculture is steadilyincreasing as they represent cost effective fertilizers.Soil characteristics also determine availability toplants by controlling the speciation of the elements,temporary binding by particles surface (adsorption–desorption processes), precipitation reactions, andavailability in soil solution (Fotovat et al. 1997).The assessment of heavy metal content, dynamic andeffect in the soil is the first concern of scientists;however, it should be mentioned that results of manyresearches have often been approximated, and, some-times, contrasting.

The distribution of metals among various compart-ments or chemical forms can be measured by asequential extraction procedure (Tessier et al. 1979;Singh et al. 1998). The knowledge of how contami-nants are partitioned among various chemical formsallows a better insight into the mechanisms of retentionand release involved in the process of migration anddecontamination (Cabral and Lefebvre 1998).

The present study was designed to examine thepartition of selected heavy metals in biosolids-amended soils from SE Spain, and also to relate thedistribution patterns of metals between chemicalphases to soil components.

2 Material and Methods

For each studied area 15 surface soil samples (0–15 cm)were taken. Collected cores were mixed thoroughlytogether and a representative sample was taken to sendto the laboratory. So, five representative surface soilsthat were polluted as a result of agricultural activitieswere used in this experiment. The biosolids-amendedsoils were selected for diversity of physicochemicalproperties; especially pH and carbonate content(Table 1). The soils are classified as non-calcareous(soil 1) and calcareous soils (soils 2 to 5). Figure 1shows the location of the sampling sites. Soil 1 is abiosolids-amended soil in Torrellano (Elche) area. Theprevailing cultivations are almond-trees, followed byolive-trees. Soils 2 to 4 are similar biosolids-amendedsoils that had been irrigated with polluted water fromSax area (Alicante, Spain) in an vineyard experimental

plot studied by Miguel Hernández University. Soil 5 isfrom a quarry biosolids disposal experimental plot inRedovan (Alicante, Spain). These soils have lowcapacity use and erosion risk. In addition, there areother terrace fields destined for cultivation of carob,olive, hazel and almond-trees.

The experimental soils were crushed, 2 mm sieved,mixed and stored at air-dried conditions. Total contentsof metals were determined following microwave diges-tion using HNO3 and analyzed by inductively coupledplasma mass spectrometry (Krishnamurti et al. 1994;Pérez, 2001).

The sequential extraction procedure was adaptedfrom procedures developed by Shuman (1985);Beckett (1989) and Ahnstrom and Parker (1999).The soluble-exchangeable fraction is the commonbioavailable form of an element being present as freeions and soluble complexes in soil and is usuallyextracted with diluted Sr, Ca, or Mg salts (Moral et al.2005). Dissolution of soil carbonates was in a buffersolution of sodium acetate at pH 5. This extractioncould include some specifically sorbed metals. Theheavy metals associated with soil organic matter weredetermined after extraction of OM with alkalinereagents and oxidation with H2O2. Ahnstrom andParker (1999) suggest the use of NaOCl to avoid thealteration of Mn oxides, Fe oxides, and silicateminerals. The metals bound in lattices of secondaryoxides, were extracted by an ascorbate-oxalatemethod (Shuman 1982) that avoided Zn contamina-tion associated with the citrate-bicarbonate-dithionitemethod and optimizes dissolution of amorphous andcrystalline Fe oxides. The residual fraction wasdissolved by microwave digestion with HNO3 (Moralet al. 2005).

Triplicate 4.0 g portions were weighed into 100 mlpolycarbonate centrifuge tubes and sequentiallyextracted as follows:

F1: Soluble-exchangeable phase: Each sample wasreacted with 30 ml of 0.1 M SrCl2 in a shaker(3,600 rph) for 2 h at 20°C.

F2: Specifically sorbed-carbonate bound: the residuewas treated with 60 ml of 1.0M NaOAc pH 5.0and shaken for 5 h at 20°C. This extraction wasperformed several times until ΔpH <0.1 in thesupernatant.

F3: Oxidizable phase: the residue was mixed with10 ml of 5% NaOCl at pH 8.5 and reacted in a

Water Air Soil Pollut (2011) 217:535–543 537

water bath (90°C) for 30 min. This procedurewas repeated four times in order to maximizeoxidation of the organic matter.

F4: Reducible phase: the residue was mixed with40 ml of 0.2M oxalic acid+0.2M ammoniumoxalate+0.1M ascorbic acid adjusted to pH 3with NH4OH in a water bath (90°C) for 30 min.This procedure was repeated four times.

F5: Residual phase: the residue was oven-dried,pulverized and mixed. Duplicate 0.400 g sub-samples were digested by microwave digestionwith 20 ml HNO3.

Following Moral et al. (2005) protocol, betweeneach step, the residue was suspended in 5 ml of 0.1MNaCl to displace entrained solution and limit metalresorption. All these rinse solutions were collected withthe preceding extract and centrifuged for 10 min at1,735 g, and the supernatant filtered into volumetricflasks containing 10 μg In-Rh l−1. All the extracts andstandard solution were acidified to 1% HNO3. ICP-MSdeterminations were obtained with matrix-matchedstandards.

3 Results and Discussion

The soils studied showed a wide range of physicochem-ical properties (Table 1). Organic C content rangedfrom 0.60% to 2.64%, with the highest level for thebiosolids-amended soil and with the highest pollutionby Cd (soil 4). CEC ranged from 0.15 to 0.35 molckg−1. The pH value of the soils mainly depends on thepresence or not of carbonates. Total Cd content ranged

Properties Non-calcareous soil Calcareous soils

Soil 1 Soil 2 Soil 3 Soil 4 Soil 5

pH (1/2.5) 6.51 8.15 8.25 7.95 7.80

EC (1:5)/dS m−1 0.40 0.75 0.60 1.00 1.47

Sand/% 61.0 19.0 18.5 19.0 34.5

Silt/% 22.0 67.5 69.0 72.0 61.5

Clay/% 17.0 13.5 12.5 9.0 4.0

Total CaCO3/% 3.4 50.0 50.5 48.9 37.8

Active CaCO3/% 1.8 16.5 15.7 15.8 13.5

Organic C/% 0.60 2.08 2.01 2.54 1.10

CEC/molc kg-1 0.15 0.30 0.32 0.35 0.25

Total Fe/mgkg-1 11,040 13,800 10,800 12,570 10,290

Total Mn/mgkg-1 467 344 342 472 375

Total Cu/mgkg-1 15.5 66.0 35.1 50.1 20.2

Total Zn/mgkg-1 26.0 260 95.0 140 105

Total Cd/mgkg-1 6.0 79 102 210 4.5

Total Ni/mgkg-1 7.5 35.5 38.2 52.5 30.5

Total Cr/mgkg-1 17.9 29.7 32.1 38.8 24.8

Total Pb/mgkg-1 28.0 230 32.0 35.0 27.0

Table 1 Chemicaland physical properties ofthe sewage sludge-amendedsoils selected

0 40 km

Alicante

Provinceof Albacete

Provinceof Murcia

Provinceof Valencia

MED

ITER

RANEA

N

SEA

NSpain

France

Por

tuga

l

Provinceof Alicante

Fig. 1 Location of the sampling sites


from 6 to 210 mgkg−1. Total Ni content ranged from7.5 to 52.2 mgkg−1. Total Cr content ranged from 17.9to 38.8 mgkg−1. Total Pb content ranged from 28 to230 mgkg−1.

In Table 2, recovery expressed as the sum ofselected metals for sequential extraction of metals inthe different fractions is compared with the totalconcentrations obtained with a microwave digestion.A good percentage recovery for the metals studied hasbeen found (>87%).

Results for the sequential extraction of Cd, Ni, Crand Pb, are summarized in Figs. 2, 3, 4, and 5 aspercentages of the total metal in each fraction. Thedifferences in Cd adsorption were attributed mainly tothe soil pH induced by biosolids application. Soilstreated with biosolids increased the amount ofexchangeable Cd but reduced the amount of com-plexed Cd (Moral et al. 2005). For soil 1, the majorityof the Cd was recovered in the oxidizable (>10%) andreducible (>80%) fractions (Fig. 1). The main fractionwas the reducible pool probably due to the exogenousnature of the contamination (polluted sediments andbiosolids) and the presence of Fe oxides. Cadmiumwas recovered mainly in the sorbed-carbonate andresidual fractions for the calcareous soils (>72%).Mahler (1988) found that Cd, both native or sludge-derived, was mainly in the carbonate fraction. Soils 2to 4 are quite similar in Cd partition, with a Cdsorbed-carbonate pool between 70% to 82% of thetotal Cd. For soil 5 biosolids was again the origin ofsorbed-carbonate Cd (>25%) but for this soil therewas a majority of Cd in the residual form (>66%).Most Cd in soil 5 was in the residual fraction and maybe a consequence of Cd compounds present insediments that form the parent materials of soils ofthis area. We observed an increasing exchangeable Cd

fraction with increasing organic matter in the soil,which is consistent with the findings of Lamy et al.(1993). In the calcareous soils amended with biosolids(soil 2 to 5), a low percentage of Cd was soluble-exchangeable, probably due to metal chelation thatincreases metal solubility in alkaline conditions.

Probably clay size fraction contained the highestamount of the total Cd. However, silt and sandfractions of the amended soils also retained appre-ciable amounts of Cd. Speciation studies revealedthat metal-organic complex-bound Cd was the mostpredominant compared to other particulate-boundCd species in the clay size fractions of the soilstreated with biosolids. We observed an increasingexchangeable Cd fraction with increasing organicmatter in the soil The distribution of total Cd in thedifferent soil particle size fractions and the speci-ation of particulate-bound Cd in the clay sizefractions varied with the soil type (p.e. soil 5 hasonly a 4% of clay fraction). The results indicatethat clay size fractions can retain Cd making it lessavailable; however, the influence of farming prac-tices, which affect Cd mobility, should not beoverlooked.

The majority of the Ni was recovered in theresidual phase (45–50%) and to a lesser extent inthe reducible fraction of the soil (12–45%). Thiscould indicate the presence of this metal in mineralsin the soil parent materials. For the calcareous soils,the sequence of Ni partition was F5>F2>F3 exceptfor soil 4. Narwal et al. (1999) found a very highcorrelation between Ni in reducible and residual formsand the content of Fe and Mn oxides in soils. As for Cd,an important proportion of Ni is in sorbed-carbonateform. As similar percentage of soluble-exchangeable.

Only the strong acids are capable of extractingchromium entirely from soils. This indicates that Cr istightly bound in the matrix and would not be easilyrelease under natural conditions (Ahumada et al. 2004;Karathanasis and Johnson 2006). The residual fractionwas the main Cr fraction in the calcareous soils (75–85%) and in soil 1 (>50%), with a very high percentagein this phase. A similar partition of Cr was observed forthe calcareous soils with the sequence F5>F4>F3. Theamount of Cr sorbed on carbonate (<5%) surfaces waslower than the soluble-exchangeable pool (<2.5%). Insoil 1, there are an important percentage of metal assoluble-exchangeable phase and as reducible phase.This soil has a pH=6.5 and chromium was mainly

Table 2 Extraction efficiency of metals, the sum of the variousextractions expressed as a percentage of the total content

Metal Soil number

1 2 3 4 5

Cd 93±3 88±3 96±3 99±3 94±8

Ni 103±5 94±4 104±7 96±3 95±5

Cr 90±6 100±3 108±3 110±5 99±3

Pb 91±7 90±2 100±3 91±3 98±3


present in mobile and mobilizable phases. The reduciblephase had high percentage of chromium from wheremobilization can occur with change in environmentalconditions. Thus, results from this study can indicate thebioavailability of chromium in Torrellano area.

Lead is one of the least concentrated elements bothin the soils and in the sludge and, the same as othermetals, it is predominantly found in the residualfraction (Ahumada et al. 2004). The main fraction forPb in calcareous soils was the residual phase (65–90%). In soil 1 residual phase is similar to reduciblephase (30–40%). The sequence of Pb partition in thecalcareous soils was very similar, F5>>F2>F3.Cabral and Lefebvre (1998) and Moral et al. (2005)found that soils contaminated with highly concentrated

Pb solutions showed an accumulation in the sorbed-carbonate phase. A large proportion of Pb was in theoxidizable phase (>10%) for soil 1, probably due to thepresence of Pb organic complex and/or Pb sulphides inthe parent materials (Moral et al. 2005).

No important mobility of heavy metals (Cd, Ni, Cr,and Pb) in amended calcareous soils (2–5 soils) has beenfound in the areas examined in this study. However innon-calcareous soils (soil 1) significant quantities ofmetals appear in soluble-exchangeable phases.

Interpretation of the preliminary results obtained inthis research is certainly useful to obtain a generalpicture of what has happened in these biosolids-amended soils, and to discover the environmentalproblems that such fertilization may lead to. No doubt,

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


F1 F2 F3 F4 F5

Fig. 2 Partition oftotal recovered Cd (%)in the five sewage sludge-amended soils. Legend:F1, soluble-exchangeablephase; F2, specificallysorbed-carbonate bound;F3, oxidizable phase; F4,reducible phase;F5, residual phase

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


F1 F2 F3 F4 F5

Fig. 3 Partition oftotal recovered Ni (%)in the five sewage sludge-amended soils. Legend:F1, soluble-exchangeablephase; F2, specificallysorbed-carbonate bound;F3, oxidizable phase; F4,reducible phase;F5, residual phase


this is a starting point to develop a mathematical studythat allows the modeling and evaluation of the evolutionand mobility of heavy elements in the calcareous andnon-calcareous soils in Alicante province.

4 Conclusions

Texture, high percentages of organic matter and thepresence of carbonate (soils 2–5) seem to suggest animportant retention of heavy metals by these compo-nents in these soils. Data obtained showed differentmetal distribution trend among the fractions in sludge-amended soils. This variability in metal bioavailabiliysuggests that total metal concentration may not be

appropriate as sensitive indicator for toxicity orenvironmental risk assessment. The biosolids incor-poration has modified the soil composition, leading tothe increment of heavy metals. The heavy metals inthis set of biosolids-amended soils were mostly andvariously associated with residual, reducible andcarbonate forms depending on the nature and proper-ties of the soils. Mainly, Ni, Cr, and Pb are associatedwith residual phase. However, Cd is mainly associat-ed with carbonate forms.

An appropriate strategy for a guideline in Alicanteprovince may be a two-tiered system that in the firstinstance requires an assessment of total metal concen-tration followed by bioavailability assessment using achemical extraction technique proposed in this paper.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


F1 F2 F3 F4 F5

Fig. 5 Partition oftotal recovered Pb (%)in the five sewage sludge-amended soils. Legend:F1, soluble-exchangeablephase; F2, specificallysorbed-carbonate bound;F3, oxidizable phase; F4,reducible phase;F5, residual phase

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


F1 F2 F3 F4 F5

Fig. 4 Partition oftotal recovered Cr (%)in the five sewage sludge-amended soils. Legend:F1, soluble-exchangeablephase; F2, specificallysorbed-carbonate bound;F3, oxidizable phase; F4,reducible phase;F5, residual phase


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distribution of cd, ni, cr, and pb in amended soils from alicante province (se, spain)

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