Int. J. Environ. Res., 6(2):565-570, Spring 2012ISSN: 1735-6865

Received 11 March 2011; Revised 25 Oct. 2011; Accepted 5 Dec. 2011

*Corresponding author E-mail: tnasrabadi@gmail.com

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Evaluating the Effects of Fertilizers on Bioavailable Metallic Pollution of soils,Case study of Sistan farms, Iran

Ghaderi, A.A.1, Abduli, M.A.1, Karbassi, A.R.1, Nasrabadi, T.1*, Khajeh, M.2

1 Graduate Faculty of Environment, University of Tehran, P.O.Box 14139-6535, Tehran, Iran2 Department of Chemistry, University of Zabol, Zabol, Iran

ABSTRACT: Present study determines not only the total amounts of metals (Cr, Cu and Pb) in superficialagricultural soil of Sistan area in Eastern Iran, but also the chemical partitioning of these elements in sevenstatistically selected cases. The analysis was run for local soil, soil treated by non-contaminated organic,compost and chemical fertilizers as well as soil treated by metal-contaminated fertilizers. The samplingcampaign was done in Zabol University research farm in 2009. The grab samples were taken from sevendifferent cases, the chemical partitioning analysis was performed and metallic concentrations were detectedusing FAAS. It may be concluded that the bioaccessibility of metals Cu and Cr would be increased in case ofimposed contamination where the soil is treated with all three kinds of fertilizers. Although a relatively similardistribution pattern is seen between anthropogenic and geopogenic portions of bulk concentration in all threekinds of fertilizers, chemical fertilizer seems to manifest a more risky condition. According to the resultsachieved by cluster analysis, a close correlation exists between Cu and Cr behavior which may be attributed tothe geological texture of the study area. In accordance with the results gained by partitioning analysis, IPOLLindex values also show contaminated chemical fertilizer as the most risky case for all three metals in comparisonwith others.

Key words: Agricultural soil, Metallic pollution, Bioavailability, Fertilizer, Sistan

INTRODUCTIONContamination caused by agricultural, municipal

and industrial activities is the major cause of poor waterquality among many countries (Nasrabadi et al., 2010a;Nabi bidhendi et al., 2007; Nasrabadi et al., 2009;Karbassi et al., 2007; Zhang et al., 2005; Ebise andInoue 2002; Nakano et al., 2004). Poorly managedagricultural operations can lead to contamination ofsurface and groundwaters by nutrients and pesticides(Nasrabadi et al., 2011; Novotny 1999; Gunninghamand Sinclair 2005). The regular use of different types ofpesticide and fertilizer products in agriculture will causedispersion within the environment by means of drift,run-off and drainage (Kolpin et al., 1998; Guzzella et al.2006). This may result in residues being encounteredin groundwaters (Lacorte and Barcelo 1996), riverwaters (Irace-Guigand et al., 2004; Claver et al., 2006),and also in coastal waters and lakes (Konstantinou etal., 2006), suggesting that mobilization can occur andthat residues can be found far away from the point ofapplication.

Lots of studies on runoffs from agricultural zoneshave been carried out detecting various fertilizers andpesticides in different hydrological and soil conditions(Karpouzas et al., 2005; Miao et al., 2003; Nakano etal. 2004; Villa et al., 2003). In Iran, agricultural activitiesare highly dependent on the use of fertilizers andpesticides due to climatic and soil conditions, thusposing a potential risk to the quality standards of waterresources.

Composting is defined as the biologicaldecomposition and stabilization of organic substratesunder conditions which allow development ofthermophilic temperatures as a result of biologicallyproduced heat, with final products sufficiently stablefor storage and application to land without adverseenvironmental effects (Polprasert, 1996). In general,the chemical and physical characteristics of compostwould vary according to the nature of the startingmaterial, the condition under which the compostingoperation is carried out and the extent of thedecomposition (Hamuda et al., 1998).

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Amendment with compost alone may initiallyincrease plant growth by improving the nutrient statusof the soil and by immobilisation of metals, but afterdegradation of the organic matter of the compost, theadsorbed metals might be released and become availableagain to plants and animals. In contrast to the widepublication of many studies which report theimmobilisation of metals with composts, a limitednumber report the possibility that compostamendments increase the leaching or extractability ofmetals. For example it has been shown that certaincomposts in combination with specific soils increasearsenic leaching (Cao et al., 2003; Mench et al., 2003).There are also references on the mobilization effectsof composts on other metals of concern. Clemente etal. (2006) reported increased bioavailability of copperafter amendment of a soil from a lead-zinc mine areawith a compost made from olive leaves and the solidfraction of olive-mill waste water. Interestingly, bothzinc and lead were effectively immobilised by thecompost. Dissolved organic matter is known tomobilise Cu and Pb through complexation but not Cdand Zn (Bradl, 2004).

Due to the toxicity and ability of the heavy metalsto accumulate in the biota, pollution by these metals isa serious problem (Morillo et al., 2002). One of themost crucial properties of these metals, whichdifferentiate them from other toxic pollutants, is thatthey are not biodegradable in the environment (Rauretet al., 1999). The heavy metal concentration in aquaticecosystems has increased considerably as a result ofinputs from human production and consumptionactivities (Nabi Bidhendi et al., 2007).

Information on total concentrations of metals aloneis not sufficient to assess the environmental impact ofpolluted sediments because heavy metals are presentin different chemical forms in sediments (easilyexchangeable ions, metal carbonates, oxides, sulfides,organometallic compounds, ions in crystal lattices ofminerals, etc.), which determine their mobilizationcapacity and bioavailability (Yu et al., 2001). Severalmethods for determining the different forms of metalsin sediments are described in the scientific literature(Nasrabadi et al., 2010b). The most widely used methodsare based on sequential extraction procedures wherebyseveral reagents are used consecutively to extractoperationally defined phases from the sediment in asequence. For this study, the sequential extractionprocedure proposed by the European UnionsStandards, Measurements, and Testing program wastaken in to consideration (Rauret et al., 1999; Morilloet al., 2002; Nasrabadi et al., 2020b). This schemeconsists of three successive extractions that allow usto associate the metals with one of the following

phases: acid-soluble phase (fraction 1), reducible phase(fraction 2), oxidizable phase (fraction 3), and a fourthphaseresidual or inert (fraction 4).

Present study determines not only the totalamounts of metals (Cr, Cu and Pb) in superficialagricultural soil of Sistan area in Eastern Iran, but alsothe chemical partitioning of these elements in sevenstatistically selected cases. The analysis was run forlocal soil, soil treated by non-contaminated organic,compost and chemical fertilizers as well as soil treatedby metal-contaminated fertilizers. Such finding makesit possible to know the mobility of metals in the soiland accordingly their bioavailability in the environment.Furthermore, a couple of soil metallic pollution indicesare also considered to evaluate the degree of pollutionwithin the study area.

MATERIALS & METHODSThe sampling campaign was done in Zabol

University research farm in 2009. The study area islocated in 61 31" longitude and 31 2" Latitude with anapproximate altitude of 478 meters from sea level. Thefield was divided into squares with one square meterof surface area. In non-contaminated segments the soilwas simply treated by organic, compost and chemicalfertilizers while in the metal-contaminated segmentsthe treated soil was also exposed to CuCl2.2H2O,CrCl3.6H2O and Pb(No3)2 to simulate the metallicpollution. The Grab samples were taken from sevendifferent cases. The samples were immediately sealedand stored at 4_C until their arrival at the laboratory.Grain size fraction less than 63 lm was chosen foranalysis (Nasrabadi et al., 2010a; Karbassi et al., 2007).All the sieving and sequential extraction procedureswere performed in a glove box purged with nitrogen(Lopez-Sanchez et al., 1996). The total metal contentwas determined by digesting the samples with a mixtureof HNO3HClO4 in a microwave oven. CEM 3010 high-pressure digestion bombs (consisting of a body madeof a specific microwave-transparent polymer with aTeflon cup and cover) were used for sample digestion.These bombs, designed specifically for microwaveheating, are chemically inert and combine theadvantages of closed highpressure (13.8 bar) and high-temperature digestion. The concentration of theanalytes in this solution was analysed by FAAS(Khajeh,,2009).The chemical partitioning of metals wasdetermined by means of the sequential extractionscheme proposed by the European Unions Standards,Measurements and Testing Program (SM and T,formerly BCR). This scheme consists of threesuccessive extractions (Table 1) that make it possibleto determine the association of the metals in threephases: acid-soluble, reducible and oxidizable.

Int. J. Environ. Res., 6(2):565-570, Spring 2012

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Furthermore, a fourth phase, residual or inert (fraction4), was determined as the difference between the totalmetal content and the sum of the contents in the threeprevious phases.

RESULTS & DISCUSSIONBulk and chemical partitioning concentrations of

metals Cu, Pb and Cr in local soil are shown in Table 2.In comparison with average shale values, the bulkconcentration of Cu and especially Cr are far belowthe common limits. However, the Pb bulk concentrationis roughly twice as the one in shale.

Bulk and chemical partitioning concentrations ofmetals in the soil samples treated by clean (Table 3)and metal-contaminated fertilizers (Table 4) are alsoanalyzed. Three different kind of fertilizers (organic,

Table 1. Extractants used in each extraction step and the extraction phases of sediments in the sequentialextraction procedure (Morillo et al., 2002)

Extraction step Reagentconcentrationtime Sediment phase

1 Acetic acid (CH3COOH)0.11 mol l _ 116 h Acid-soluble

(exchangeable ions, carbonates)

2 Hydroxylamine hydrochloride (NH2OHHCl)0.5 mol l

_ 1 (pH 2 with HNO3)16 h Reduc ible

(iron/manganese oxides)

3 Hydrogen peroxide H2O28.8 mol l _ 11 h at

room temperature + 2 h at 85 C+ ammonium acetate (CH3COO NH4)1.0 mol l _ 1 (pH 2 with HNO3)16 h

Oxidizable (organic substances and

sulfides)

Table 2. Chemical partitioning of metals in local soil (mg/kg)

Shale values

Geopogenic %

Anthropogenic %

Oxidizable Concentration

Reducible Concentration

Exchangeable Concentration

Bulk Concentration Metal

45 67.4 31.6 1.17 .75 5.33 22.94 Cu

20 31.2 68.8 2.28 6.3 17.84 38.36 Pb

90 68.9 31.1 .32 .21 .65 3.79 Cr

compost and chemical) are considered in each analysiscampaign.To assess the intensity of metal contamination in soilsamples, the geochemical accumulation index wascalculated using:

Igeo = Log2 [Cn/(1.5 x Bn)] (1)

Where Igeo is the geochemical accumulation index, Cnis the sediment metal concentration and Bn is the metalconcentration in the shale (Gonzalez-Macias et al.,2006; Forstner et al. 1990; Muller 1979).In the present study, a newly developed formula whichis a modification of the Igeo is introduced as follows((Karbassi et al., 2008):

IPOLL = Log2 [Bc/Lp] (2)

Table 3. Chemical partitioning of metals in soil treated by non-contaminated fertilizers

Organic Fertilizer

Geopogenic %

Anthropogenic %

Oxidizable Concentration

Reducible Concentration

Exchangeable Concentration

Bulk Concentration Metal

66.8 33.2 1.386 .752 5.856 24.1 Cu 27.6 72.4 2.65 6.52 21.11 41.81 Pb 67.2 32.8 .407 .232 .774 4.31 Cr

Compost 69 31 1.62 .64 5.69 25.67 Cu

31.6 68.4 2.97 5.62 21.18 43.56 Pb 67.8 32.2 .46 .15 .84 4.53 Cr

Chemical fertilizer 66.1 33.9 1.13 .84 5.9 23.21 Cu 30 70 2.26 6.37 18.75 39.12 Pb

67.4 32.6 .346 .16 .703 3.86 Cr

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Monitoring of Faults

Table 4. Chemical partitioning of metals in soil treated by metal-contaminated fertilizersOrganic fertilizer

Geopogenic %

Anthropogenic %

Oxidizable Concentration

Reducible Concentration

Exchangeable Concentration

Bulk Concentration Metal

36.5 63.5 .78 .97 31.85 52.96 Cu 41.2 58.8 6 1.06 60.53 115 Pb 32.2 67.8 1.60 .85 9.36 17.44 Cr

Compost 53.1 46.9 1.88 .646 28.1 65.26 Cu 44.4 55.6 6.62 1.04 60.83 123.25 Pb 28.4 71.6 2.32 .52 10.97 19.3 Cr

Chemical fertilizer 25 75 .746 .376 29.4 40.7 Cu 38 62 7.02 2.16 56.86 106.7 Pb

26.7 73.3 .675 .46 9.3 14.24 Cr

Table 5. Igeo values for the soil treated by contaminated and non-contaminated fertilizers

contaminated organic

fertilizer

contaminated organic

fertilizer

contaminated organic fertilizer

Non-contaminated

chemical fertilizer

Non-contaminated

compost

Non-

contaminated

organic

fertilizer

Local

soil Metal

-0.52 0.15 -0.14 -1.34 -1.18 -1.27 -1.35 Cu 1.62 1.83 1.73 0.18 0.33 0.27 0.15 Pb

-2.03 -1.60 -1.74 -3.92 -3.69 -3.76 -3.94 Cr

Table 6. Ipoll values for the soil treated by contaminated and non-contaminated fertilizers

contaminated chemicalfertilizer

contaminated compostfertilizer

contaminated

organic

fertilizer

Non-

contaminated

chemical fertilizer

Non-

contaminated

compost

Non-

contaminated

organic fertilizer

Local soil

Metal

2.00 0.91 1.45 0.59 0.53 0.58 0.56 Cu

1.39 1.17 1.27 1.73 1.66 1.85 1.68 Pb 1.90 1.81 1.63 0.56 0.56 0.57 0.53 Cr

Fig. 1. Dendrogram showing clustering of metals

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CONCLUSIONThe current study determines the bulk

concentration and also the chemical partitioning ofmetals (Cr, Cu and Pb) in superficial agricultural soil ofSistan area in Eastern Iran in samples collected fromlocal soil, soil treated by non-contaminated organic,compost and chemical fertilizers as well as soil treatedby metal-contaminated fertilizers. It is concluded thata similar pattern exists in metallic bulk concentrationsas well as partitioning phases (exchangeable, reducibleand oxidizable concentrations) between the virgin soiland the one treated by clean fertilizers (Tables 2 and3). In other words, non of the fertilizers may remarkablychange the soil affinity of sorption/desorptionprocesses in case where no metallic pollution isimposed. However, another scenario is observed whenthe soil is exposed to metallic pollution (Table 4). Theanthropogenic portion of metals Cu and Cr isapproximately doubled in soil samples treated bycontaminated fertilizers in comparison with virgin soilsamples. Conversely, the mobility of Pb is slightlydecreased in the latter case. Accordingly, it may beconcluded that the bioaccessibility of metals Cu andCr would be increased in case of imposedcontamination where the soil is treated with all threekinds of fertilizers. Although a relatively similardistribution pattern is seen between anthropogenic andgeopogenic portions of bulk concentration in all threekinds of fertilizers, chemical fertilizer seems to manifesta more risky condition. Such slight difference may bedue to the lack of organic materials in chemical fertilizersin comparison with compost and organic ones whichdecrease the formation of organo-metallic compounds.According to the results achieved by cluster analysis,

a close correlation exists between Cu and Cr behaviorwhich may be attributed to the geological texture ofthe study area. Regarding Pb, the high bulkconcentration (around twice the average shale value),the remarkable anthropogenic share in totalconcentration (around 70 %) as well as the behaviorindependency to other two metals indicate a relativelydifferent source. Proximity of studied farms to the mainroad and consequently being exposed to a graduallong-term load of vehicle fuels in different forms maybe introduced as the main reason of such metallicpollution in the samples. Regarding index approach,as the geochemical index does not consider thebioavailable metallic pollution of soil samples and justfocuses on the comparison between the existent bulkconcentrations with that of shale, the interpretation ofindex values falls mostly within the not pollutedcategory. However, as it was indicated before the Pbstatus is changed between not polluted and slightlypolluted level because of its high initial concentration.On the other hand, IPOLL smoothly intervenes the roleof bioavailable contamination in final interpretation.Accordingly the pollution level of Cu and Cr incontaminated fertilizers is reported to be slightlypolluted while the one in clean fertilizers is not polluted.Furthermore, in accordance with the results gained bypartitioning analysis, IPOLL values also introducecontaminated chemical fertilizer as the most risky casefor all three metals in comparison with others.

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