PREPARATION OF BOTTOM DEPOSIT SAMPLES

E C O LO GIC AL C H E M IS T R Y AN D E N GIN E E R IN G S Vol. 15, No. 1

2008

Anna RABAJCZYK∗

PREPARATION OF BOTTOM DEPOSIT SAMPLES FOR SPECIATION ANALYSIS OF HEAVY METALS PRZYGOTOWANIE PRÓBEK OSADÓW DENNYCH DO ANALIZY SPECJACYJNEJ METALI CIĘśKICH

Summary: Growing interest in speciation issues requires solving many problems connected with environmental sample preparation for analysis and it is extremely complicated. This process requires huge knowledge related with sampling, transportation, preservation and storage of samples. Incorrect proceeding with samples results in chemical, physical and biological processes which run very fast and bring about changes of properties and concentration of analytes. It results in wrong assessment of environmental state. Appropriate proceeding with environmental sample in order to prepare it for analysis is necessary to prevent above-mentioned processes. On the basis of literature concerning selected metals (Zn, Cd, Pb, Al), issues connected with speciation analytics were presented and basic stages of analytical procedure of speciation determination of heavy metals in bottom deposit samples were characterized. Stages such as sampling and storage of bottom deposit samples, extraction, enrichment and determination were taken into account. Keywords: operational speciation analytics, zinc, cadmium, lead, aluminium, bottom deposit, sampling, preservation, storage, preparation of samples of solid material, detection

Introduction Bottom deposits are important component of water ecosystems. They are specific ecological niches in which benthic organisms develop. They are also feed source for water organisms such as small invertebrates and protozoa. Assessment of pollutant influence on life in water bodies requires examination of concentration and source of pollutants. In this aspect, bottom deposits which function as sorption column are particularly useful material for research aiming to determine main sources of pollutants and they explain what happens in water environment [1]. Conducted monitoring research include determination of general content of heavy metals what gives incomplete characteristic of environmental pollution rate and it does not give any information on chemical activity of analysed compounds. As far as metals ∗ Faculty of Mathematics and Natural Science, Swietokrzyska Academy im. Jana Kochanowskiego, ul. Świętokrzyska 15, 25-406 Kielce, tel. 041 349 64 18, tel./fax 041 362 66 23, email: [email protected]

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are concerned it is of great importance because their toxic influence on organisms appears at relatively low concentration of soluble and exchangeable forms. Determination of metal “mobility” that is its possibility to move into water and then to biogeochemical circulation [2, 3] is necessary to estimate water ecosystem state and metal hazard. Natural metal and secondary metal originated from pollution occurs in environment in various chemical forms. At least three aspects should be taken into account when estimating their mobility: 1) content of mobile form of metal that may directly participate in biocirculation including soluble metal forms, ion-exchangeable forms and labile complex metal associations, 2) stable metal form content as a potential reserve in biocirculation including among others chemisorptions ions, sparingly soluble salts, metal forms in complex associations with organic matter, 3) content of isomorphic pollutants (admixtures) of various metal forms especially silicate forms being a strategic reserve of metals in environment released to biocirculation in long-term periods or in aggressive conditions [2]. Taking into account relatively easy metal cation migration to water, it can be assumed that metal concentration in bottom deposits is a sensitive index of environmental cleanliness. Conducting an operational speciation analysis (fractionation) is necessary to obtain information on potential mobility of metals in examined environment and on assessment of influence of bottom deposit metals on environment which can be removed from the deposit as a result of change of physical, chemical or biological conditions [3]. Sequential extraction is used for that purpose [4].

Bottom deposit sampling and its pretreatment There is more and more literature concerning various aspects of analytics of environmental pollutants describing sample preparation for analysis. Determination of metal content in solid environmental sample such as bottom deposit requires appropriate handling which ensures obtaining reliable information on examined ecosystem cleanliness. Selection of wrong procedure may result in huge mistakes in sample preparation stages. These mistakes may lead to loss of determined element, for example by adsorption organic matter residues, and to contamination of sample by compounds from the air, laboratory ware or low purity reagents used [5, 6]. Preparation of environmental samples for analysis is complicated and timeconsuming. It is very often a result of complex matrix of sample. Essential operations and processes related to preparation of environmental samples are presented in Figure 1. Preliminary recognition of examined area is a first step that begins a process of bottom deposit sample preparation. Physiographical, geological and geobotanical factors have to be taken into account what enables monitoring of geochemical processes in sampling site. Current environmental state is evaluated in general on this stage as well as decisions on selection of method, sampling technique or using appropriate equipment are made [8].

Preparation of bottom deposit samples for speciation analysis of heavy metals

Measurement of variable physicochemical parameters such as Eh, pH Selection of laboratory samples

Field analysis of samples

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Preliminary field research

Location and evaluation of research area Designating sampling sites and selection of sampling method

Particular field research

Field sketch and information card GPS coordinates Analysis of environmental parameters Phytosociological pictures Profiles

Sampling, storage and transportation of samples

Sampling of representative samples Bottom deposits sieving Prevention of degradation and contamination of samples

Sample preparation

Rubbing, drying, sieve analysis Sample weighing Solubilizing/enrichment Purification and volume reduction of extract Separation

Laboratory analysis

Interpretation of research results

Chemical Mineralogical

Selection of statistical method Analysis of selected parameters (geological, topographic, climatic, hydrological, edaphic, biological)

Fig. 1. Essential stages of environmental sample research aiming for metal speciation analysis [7, 8]

Bottom deposit sampling is a separate issue because this activity may be a reason for huge mistake being a part of final determination. There are special construction samplers and their use depends on analysis objective and examined area. Using equipment and techniques of sampling which make it possible not to disturb a structure of deposit surface layer should be the principle [9]. With regard to frequent multicomponent determination (trace elements) in the same samples, it is recommended to use equipment and sieves made of stainless steel and various polyethylene bags and bottles [6]. Moreover collection of sample duplicates in amount of one out of ten samples is recommended and it makes it possible to carry out control analyses [10]. Fluvial deposit samples should be collected at interval of 0÷25 cm and wet sieved in situ to obtain fraction less than 0.15 mm. It ensures obtaining homogeneous samples and removing all external impurities. Two-sieve kit should be used for that purpose: one of sieve mesh of 2 mm diameter to remove mesh fraction and the other one of 0.15 mm

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diameter together with appropriate bowl. Each watercourse deposit sample should consist of 5÷10 partial samples collected on 250÷500 m long segment (every 50 m) [11] and it should be collected in current zone what allows to avoid the influence of extraneous rock material from river-bank. During research planning stage it has to be taken into account that determination of trace elements only in aleurite-pelitic fraction or pelitic fraction gives overstated results which are not representative for examined environmental sample with regard to high content of natural sorbents [8]. Excess water should be removed from bottom deposit samples intended for heavy metal analysis so that some deposit components will not be dissolved. Collected material should be sieved and then dried at the room temperature so that mould and microorganisms do not develop what may cause redistribution of chemical components and even changes of isotopic content. After quartering dried samples are grounds in automatic agate mill to obtain 0.063 mm grain size fraction. Such material is then prepared by solubilization and extraction however selection of further methods depends on research goals and concentration of analytes determined.

Procedures of sequential extraction (fractionation) Determination of analytes concentration in the ng/g range is possible in many types of environmental samples while as far as solid samples are concerned it is more complicated. This is because particular chemical individuals and physical forms of given element may be transformed during sample preparation for analysis. Furthermore there are major differences between analytical signal values for given element depending on element form and concentration of analytes in samples is very diversified [3]. That is why extraction techniques are applied to separate analytes from matrix, to eliminate or reduce interference of other components and to condense an analytes to a level enabling determination [12]. Interest in sequential extraction technique for analysis of metals in bottom deposits grows systematically. Nowadays a dozen or so methods for selection of particular element fractions are known (Table 1). 5-stage Tessier method which allows to select 5 fractions or 3-stage method recommended by European Community Bureau of Reference (BCR) are used for characteristic of functional speciation of metals in bottom deposit [13]. One has to remember that lixiviating incomplete amount of metal in one stage of extraction may increase this amount in next stage that is why reagent and sequential extraction conditions should meet specified criteria which determines their practical usage: • components of used solutions should not form stable sparingly soluble complex compounds with ion extracted from environmental material to eluate, • solution pH should be lower than pH of hydroxydeposit precipitation from processed deposit, • extractant anion should be weak acid anion and strong acid should not be formed with participation of H+ exchangeable ion under extraction conditions, • sequential extraction conditions in research on mobile metal fractions should be as near as possible to environmental conditions [2].

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Table 1 Examples of procedure of operating sequential extraction (fractionation) Methodology

Fractions

Source

1

2

3

MgCl2 CH3COOH/ CH3COONa NH2OH·HCl/CH3COOH H2O2/HNO3/CH3COONH4 HF/HClO4 (5:1)

Exchangeable Carbonate Oxide Organic matter Residue

[14]

H2O CH3COONH4/CH3COOH NH2OH·HCl/CH3COONH4/CH3COOH H2O2/HNO3/CH3COONH4 HClO4

Water-soluble Exchangeable Oxide Organic and sulphide Residue

[15]

KNO3 NaOH EDTA HNO3

Exchangeable Adsorbed compounds Organic matter Residue

[16]

H2O (distilled water) NaHCO3 + Na2S2O4 NaOH HCl NaOH

Water-soluble Organic and humus Humus Carbonate, Fe hydroxide and sulphide Kaolinite

[17]

CH3COONH4 CH3COOH/ CH3COONa NH2OH·HCl/HNO3 Oxalate buffer H2O2/HNO3/CH3COONH4 HNO3

Exchangeable Carbonate Mn oxide Fe oxide (amorphous) Organic and sulphide Residue

[18]

MgCl2 CH3COOH/ CH3COONa NH2OH·HCl/CH3COOH H2O2/HNO3/CH3COONH4 HNO3/HClO4 (2:1)

Exchangeable Carbonate Oxide Organic Residue

[19]

H2O CH3COONH4 C6H6/CH3OH C6H6/CH3OH/KOH HCl HF HCl/HClO4/HNO3

Water-soluble Exchangeable Organic (soluble) Organic (fulvic and humus acids) Mineral readily solubilizable Mineral sparingly solubilizable Insoluble organic matter

[20]

CH3COONH4 CH3COOH (NH4COO)2 H2O2/HNO3 HClO4/HNO3

Exchangeable Carbonate Fe and Mn oxide Sulphide Residue

[21]

Mg(NO3)2 EDTA C6H8O6/oxalate buffer NaOCl HNO3/HClO4/HF/KMnO4

Exchangeable EDTA-soluble Oxide Sulphide Residue

[22]

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CH3COONa NH2OH·HCl/HCl NH2OH·HCl/CH3COOH KClO3/HCl/HNO3 HF/HClO4/HNO3 CH3COOH NH2OH·HCl/HNO3 H2O2/CH3COONH4/HNO3

2

3

Exchangeable Fe hydroxide and Mn oxide Fe oxide (crystalline) Organic and sulphide Residue Carbonate Oxide Organic and sulphide

[23]

[24]

Sequential extraction of bottom deposit samples should be performed using water solution of appropriate content and classical laboratory techniques including several successive extraction procedures. These techniques are based on two assumptions: 1) extraction solution isolates only one form of all element forms in a sample, 2) readsorption of previously dissolved forms does not occur [3]. All analytical techniques applied in trace element analysis have to be conducted respecting all procedural rules and should ensure that: • sample decomposition should proceed quantitatively and inorganic components should be converted into soluble forms, • operation should be simple, fast and inexpensive, • it is possible to automate the process, • new matrix which is generated after decomposition should not be a barrier against determination using selected analytical method or technique [7]. However not all of these analytical techniques require the same sample decomposition rate (Table 2). Table 2 Division of sample decomposition techniques with regard to decomposition rate Techniques Techniques that do not require previous sample decomposition Techniques that require at least partial decomposition of sample Techniques that require total decomposition of sample

Examples • • • • • • • • • •

Notes

Instrumental Neutron Activation Analysis INAA techniques applying X-ray fluorescent spectrometry Contamination of sample techniques applying Zeeman fluorescent spectroscopy and loses of analytes can be avoided techniques applying Graphite Furnace Atomic Absorption Spectrometry for solid samples Accuracy of results is not Graphite Furnace Atomic Absorption Spectrometry closely related to sample GFAAS decomposition rate, however Flame Atomic Absorption Spectrometry FAAS there is a matrix effect risk Inductively Coupled Plasma Atomic Emission connected with organic Spectrometry ICP-AES matter remained in a sample electrochemical techniques: Cathodic Stripping Total decomposition Voltamperometry CSV, Anodic Stripping Voltamof sample and stabilization perometry ASV of chemical form in which potentiometry using ion-selective electrodes analyte exists is required spectroscopy techniques

Division of sample decomposition techniques can be done taking into account conditions of the process. According to these criteria, techniques are most frequently divided into two groups: „dry” and ,,wet” (Fig. 2).

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Sample decomposition techniques

„dry” decomposition techniques Incineration Mineralization in oxygen plasma Sample decomposition in Schöniger bottle Sample decomposition in oxygen bomb Sample decomposition in dynamical system Melting

„wet” decomposition techniques Dissolution in hot acids Decomposition in oxidizing mixtures ultrasound-aided Sample decomposition using UV radiation Techniques using microwaves

Fig. 2. Techniques of environmental sample decomposition

Nowadays „wet” decomposition techniques play more important role than „dry” decomposition in analytics of environmental pollutants. Decomposition of sample matrix caused by oxygen released from acids in raised temperature. HNO3, H2SO4, HClO4, HF and H2O2 acids are used as primary oxidizing factors. “Wet” decomposition may proceed both in open and closed system at the same time closed system is highly recommended for trace element analysis because it allows to avoid loss of analytes and secondary sample contamination. It also allows to carry out decomposition in raised temperature and pressure and it results of shortening the time of process [7, 25]. “Wet” sample decomposition proceeds at significantly lower temperatures than those of “dry” sample decomposition. However sample does not decompose completely very often and coprecipitation of analytes with deposit appeared in oxidizing mixture used for decomposition. That is why laboratory ware for “wet” decomposition must be made of pure and chemical resistant materials preferably of quartz [7]. To extract metal from sample, solutions of increasing ability to extract metal are used, from forms weakly combined with deposit solid fraction to more permanently combined fractions of less mobility thus they do not potentially threaten the environment [13]. A release of strongly combined forms incorporated into matrix requires destruction of material what is done using concentrated acids or their mixtures. Analysed material is treated with consecutive extractant and each successive extractant is more chemically active [26]. Efficiency and repeatability of multistage extraction techniques directly depend on: • chemical properties, selectivity and efficiency of selected extractants, • order of particular steps, • working conditions such as: extractant pH and concentration, leaching time, mass ratio of solid to solution, extraction temperature, atmosphere type above solution (air, nitrogen), phase separation method (influence of centrifugation velocity and time, type of filters, etc.), • specific “matrix effects” connected with content of phases and elements and with readsorption [2].

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Preparation of bottom deposit sample for speciation analysis of selected metals (examples) Speciation analysis using Rudd et al. method [27] was applied in research aiming to determine zinc bioavailability in bottom deposits of „Dziećkowice” water basin (Fig. 3). In this work forms of zinc weakly combined in bottom deposit, that is exchangeable and adsorbed forms were assumed as bioavailable forms [28]. Sampling, storage and transportation of samples

1. Sampling using Eckman-Birge type sampler. 2. Separation of beds of 2 cm thickness into polypropylene containers. 3. Transportation.

1. 2. 3. 4.

Samples preparation

Drying to constant mass at 105ºC. Grinding in mortar. Weighing samples (1 g each). Sample solubilizing within 24 hours in consecutive solutions: 1.0 M KNO3, 0.5 M KF, 0.1 M Na4P2O7, 0.1 M EDTA and 6.0 M HNO3 in proportion of 1:40 spin-drying for 10 min washing with distilled water in amount of 10 cm3 spin-drying for 5 min residue mineralization using HNO3/HF mixture extract acidification by concentrated HNO3 to 1% HNO3 concentration 5. Microwave mineralization using HNO3/HF mixture.

Laboratory analysis

AAS method in acetylene-air flame.

Interpretation of research results

Statistica for Windows ver. 5.1 pl.

Fig. 3. Scheme of preparation of bottom deposit sample from „Dziećkowice” water basin in order to determine zinc bioavailability using speciation analysis by Rudd et al. method [27]

Correctness of determinations was checked out applying benchmark addition method while method accuracy was carried out using analysis of reference material CRM - 277 obtaining 537±10 mg/kg (certified value 547±12 mg/kg). In order to determine correlation between metal content in bottom deposit and matrix, Kuang-Chung et al. [29] team carried out research on deposit in five rivers in south Taiwan: Yenshui, Tsengwen, Chishui, Potzu and Peikang (Fig. 4) using modified 5-stage sequential extraction procedure (SEP) [14, 30]. Interpretation of obtained results was carried out using correlation analysis, principal component analysis and linear regression analysis. All laboratory wares used by authors were washed with 10% (v/v) HNO3 within 4 hours, rinsed with deionized water and dried. Accuracy of measurements was determined by triple analysis of metal concentration in bottom deposit samples collected from separate depth of examined rivers.

Preparation of bottom deposit samples for speciation analysis of heavy metals Sampling, storage and transportation of samples

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1. Sampling using Wildco type sampler (USA). 2. Transportation.

Samples preparation

1. Placing fractions in polypropylene containers depending on depth of collected bed (0÷10 cm, 10÷30 cm, >30 cm). 2. Drying with nitrogen stream free of oxygen (< 0.04% O2). 3. Weighing samples (3 g each). 4. Sample solubilizing in consecutive solutions: 1 M NH4OAc (pH = 7) and shaking within 30 min at room temp. 1 M NaOAc (pH = 5 using HOAc) shaking within 5 hours at room temp. 0.1 M NH2OH·HCl in 0.1 M HNO3 shaking within 30 min 0.04 M NH2OH·HCl in 25% (v/v) HAc heating for 6 hours at 96ºC 0.1 M HNO3, 30% H2O2 heating for 5 hours at 85ºC, 3.2 M NH4OAc w 20% HNO3 and shaking within 30 min at room temp. 5. Spin-drying for 20 min (after each stage of sequential extraction).

Laboratory analysis

AAS method (GBC, AA960)

Interpretation of research results

Correlation Analysis, CA Principal Component Analysis, PCA Linear Regression Analysis, LRA

Fig. 4. Scheme of preparation of bottom deposit sample from 5 rivers in south Taiwan for analysis of heavy metal content

Sanghoon et al. [31], Choi et al. [32], Chrastný et al. [33], Mathew et al. [34] or Panda et al. [35] also applied the sequential extraction of Tessier et al. [14]. Dawson and Macklin [36] for determination of Pb, Zn, Cu and Cd in bottom deposit from Aire River in south Yorkshire applied 5-stage Tessier sequential extraction modified by Lum [37] and Bradley [38]. Zhu et al. [39] determined Cu, Pb, Ni and Cd content in bottom deposit from Dongping River in China using 3-stage sequential extraction recommended by BCR [40]. During research they also analysed influence of grain size on obtained results (Fig. 5). All laboratory ware used for analysis were washed with 10% (v/v) HNO3 within 24 hours, rinsed with deionized water and dried. Uncertainty of measurement method was determined by benchmark addition (BCR No. 40) obtaining ±5% of certified value. Shen et al. [41] as well as Kolowski-Rodrigues and Laquintinie Formoso [42] also applied 3-stage BCR procedure for bottom deposit analysis to determine heavy metals such as Cu, Fe, Mn, Ni, Pb and Zn in separate fractions. Liquid extraction techniques of solid sample including new solutions using additional factors such as ultrasonic waves or microwave radiation are applied more and more often in order to extract separate fractions of metal in bottom deposit. The task of supporting factors is to increase process efficiency, to reduce processing time, costs and solvent consumption [3] (Fig. 6).

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Sampling, storage and transportation of samples

1. Sampling using gripping device with polypropylene spoon. 2. Fractionation by mechanical sieving through mesh of 280, 163, 78, 63 µm. 3. Placing separate fractions in hermetically sealed polyethylene containers. 4. Lowering temp. to 4ºC. 5. Transportation.

Samples preparation

1. Keeping samples to reach room temp. 2. Weighing samples 1 g each (from each fraction). 3. Sample solubilizing in consecutive solutions: 0.11 M HAc shaking within 16 hours at room temp. 0.1 M NH2OH·HCl (pH = 2 using HNO3) shaking within 16 hours at room temp. 4. 30% H2O2, waiting 1 hour, 30% H2O2, heating for 1 hour at 85ºC, 1 M NH4Ac shaking within 16 hours at room temp. 5. HNO3/HClO4/HF etching. 6. Spin-drying for 20 min (after each stage of sequential extraction). 7. Before analysis extracts were stored in PTFE containers at 4ºC.

Laboratory analysis

ICP-MS Aglent 7500a

Interpretation of research results

Statistica for Windows Transmission Electron Microscopy (TEM)

Fig. 5. Scheme of preparation of bottom deposit sample from Dongping River in China for analysis of selected metal content

Technique of microwave assisted mineralization meets analysts' expectations in range of improvement of the process of preparing a sample for analysis [5]. Microwaves allow to significantly reduce a time of sample processing, to mineralize a sample completely, and to drastically limit loss of elements and sample impurities in comparison with other methods. This type of mineralization may be practically applied to all kinds of samples including those considered as almost indecomposable with traditional techniques [5, 43]. One has to remember that apart from many advantages like for example efficacy of organic and inorganic matter decomposition, small amount of solvents used or short extraction time, microwave assisted mineralization technique shows also some disadvantages such as: • necessity of using a solvent which absorbs microwave radiation (except water in a sample), • necessity for caution (closed system), and necessity of cooling a system, • necessity to introduce a filtration stage. Research on speciation analysis of Al, Zn, Cd and Pb in bottom deposits of rivers in Swietokrzyskie Region, Poland carried out by the author are an example of microwave assisted sequential extraction [3, 44, 45]. The research revealed that the method proposed is fast, inexpensive, simple end efficient for preparation a bottom deposit sample for determination of trace metals in a sample with AAS and it markedly shortens an analysis

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time. Moreover small amount of chemical reagents is sufficient to perform the process and insignificant amount of side products, which are not dangerous to the environment, is generated in comparison with the traditional method. With regard to lack of certified reference materials for bottom deposit samples, accuracy of sequential extraction methods applied was estimated by summing partial concentrations and comparing them to total concentration of analyte and by comparing obtained concentration values to those obtained after Tessier sequential extraction procedure was applied [14]. Analyte extraction from solid samples to liquid phase

Classical extraction techniques using solvent

Techniques using liquid in supercritical state (Supercritical Fluid Extraction, SFE)

Techniques using additional factors supporting extraction process

Shaking with solvent

Ultrasound-supported extraction (sonification)

Extraction in Soxhlet apparatus

Medium Pressure Liquid Extraction (MPLE)

Analyte extraction in solvent stream from sample placed in column

Accelerated extraction under conditions of raised pressure and temperature (Accelerated Solvent Extraction, ASE)

Homogenization with solvent (grinding)

Leaching

Microwave-Assisted Extraction (MAE)

Extraction with liquid in supercritical state (EFLE, SALE)

Fig. 6. Techniques of analyte extraction from solid samples [7]

There is also an ultrasound assisted analyte extraction process and then it will depend on ultrasound wave power, a phase at which a wave reaches its maximum, a time of exposition of a sample to these waves, type and concentration of acid, temperature of the process and chemical properties of matrix [46]. Average time of ultrasound assisted extraction amounts from a few minutes to 30 minutes. Values similar to those obtained in Soxhlet apparatus after an extraction lasting more than ten hours are presented during this period [26]. An analysis aimed to determine Cu, Pb, Zn, Ni and Mn in bottom deposit samples collected from Kizil River and Hafik Pond in Sivas city in Turkey is an example of ultra-

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sound assisted sequential extraction [46]. The research showed that the method proposed is fast, inexpensive, simple and efficient when preparing a sample to determine trace metals in bottom deposit sample with AAS, and what is more analysis duration is shortened. Additionally, small amount of chemical reagents is sufficient to perform the extraction, insignificant amount of side products, which are not dangerous to the environment, is generated, and no toxic fumes appear. The only disadvantage is that the sample is not completely etched [47].

Summary Operating speciation analysis (fractionation) includes research on element distribution between mineral forms (fractions): • exchangeable - claylike, • carbonate, • oxide readily reducing - Mn, • oxide medium reducing - Fe, • organic and/or sulphide, • residual [8]. Range of analysis of chemical fractions depends on division into stages (from 3-stages to 6-stages), reagent aggressiveness and research conditions. Accuracy of sequential extraction methods applied may be estimated by summing partial concentrations and comparing them to total concentration of examined element. However applied procedures of sequential extraction most frequently concern selection of metal groups and they are not always selective for individual analyte. Some research workers question results obtained by mineral speciation methods because of instability of examined forms, influence of too many variables on each extraction stage such as sample graining, type of dominant matrix and chemical composition of sample, order and time of extraction, solution of different minerals and element resorption, shape and size of laboratory wares, changes of temperature, way of mixing, centrifugation velocity, porosity of filters and lack of appropriate certified reference materials [8]. Moreover a large number of sequential extraction methods applied to speciation analysis of metals in bottom deposits hinders comparing and discussing the results thus evaluation of water ecosystem cleanliness state is impossible locally and globally. That is why it appears to be necessary to proceed further research on unification of procedure of bottom deposit sample preparation for speciation analysis of heavy metals and on preparation of appropriate certified reference materials what will enable above-mentioned methods to be verified and controlled.

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[27] Rudd T., Lake D.L., Mehrotra I., Sterritt R.M., Kirk P.W.W., Campbell J.A. and Lester J.N.: Characterisation of metal forms in sewage sludge by chemical extraction and progressive acidification. Sci. Total. Environ., 1988, 74, 149-175. [28] Wiechuła D., Kwapuliński J. and Loska K.: Zastosowanie specjacji w badaniu biodostępności cynku w osadach dennych zbiornika „Dziećkowice”. Cynk w środowisku - problemy ekologiczne i metodyczne, Zeszyty Naukowe Komitetu „Człowiek i Środowisko” PAN, 2002, 33, 183-188. [29] Kuang-Chung Y., Li-Jyur T., Shih-Hsiung Ch. and Shien-Tsong H.: Correlation Analyses on Binding Behavior of Heavy Metals with Sediment Matrices. Water Res., 2001, 35, 2417-2428. [30] Belzile N., Lecomte P. and Tessier A.: Testing readsorption of trace elements during partial chemical extractions of bottom sediments. Environ. Sci. Technol., 1898, 23, 1015-1020. [31] Sanghoon L., Ji-Won M. and Hi-Soo M.: Heavy metals in the bed and suspended sediments of Anyang River, Korea: implications for water quality. Environ. Geochem. Health, 2003, 25, 433-452. [32] Choi S.C., Choi T.W.H., Tsang C.W., Li X.D. and Wai O.W.H.: Distribution of cadmium, chromium, copper, lead and zinc in marine sediments in Hong Kong waters, Environ. Geolog., 2006, 51, 455-461. [33] Chrastný V., Komárek M., Tlustoš P. and Švehla J.: Effects of flooding on lead and cadmium speciation in sediments from a drinking water reservoir. Environ. Monit. Assess., 2006, 118, 113-123. [34] Mathew M., Mohanraj R., Azeez P.A. and Pattabhi S.: Speciation of heavy metals in bed sediments of Wetlands in Urban Combater, India. Bull. Environ. Contam. Toxicol., 2003, 70, 800-808. [35] Panda U.C., Rath P., Sahu K.C., Majumdar S. and Sundaray S.K.: Study of geochemical association of some trace metals in the sediments of Chilika Lake: a multivariate statistical approach. Environ. Monit. Assess., 2006, 123, 125-150. [36] Dawson E.J. and Macklin M.G.: Speciation of heavy metals in floodplain and flood sediments: a reconnaissance survey of the Aire Valley, West Yorkshire, Great Britain. Environ. Geochem. Health, 1998, 20, 67-76. [37] Lum K.R.: The potential availability of P, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in urban particulate matter. Environ. Technol. Lett., 1982, 3, 57-62. [38] Bradley S.B.: Suspended sediments in regulated rivers. PhD Thesis, University College of Wales, Aberystwyth 1984. [39] Zhu Y., Zou X., Feng S. and Tang H.: The effect of grain size on the Cu, Pb, Ni, Cd speciation and distribution in sediments: a case study of Dongping Lake, China. Environ. Geolog., 2006, 50, 753-759. [40] Davidson C.M., Thomas R.P. and McVey S.E.: Evaluation of a sequential extraction procedure for the speciation of heavy metals in sediments. Anal. Chim. Acta, 1994, 291, 277-286. [41] Shen J., Liu E., Zhu Y., Hu S. and Qu W.: Distribution and chemical fractional of heavy metals in recent sediments from Lake Taihu, China. Hydrobiologia, 2007, 581, 141-150. [42] Kolowski-Rodrigues M.L. and Laquintinie Formoso M.L.: Geochemical distribution of selected heavy metals in stream sediments affected by tannery activities. Water Air Soil Pollut., 2006, 169, 167-184. [43] Srogi K.: Zastosowanie ekstrakcji wspomaganej promieniowaniem mikrofalowym - MAE - w kontroli zanieczyszczenia środowiska. Wiad. Chem., 2006, 60, 399-419. [44] Bezak-Mazur E. and Rabajczyk A.: Analiza specjacyjna glinu w stałych próbkach środowiskowych. Mat. Konf. nt. Mikrozanieczyszczenia w środowisku człowieka. Wyd. Politechniki Częstochowskiej, Częstochowa, 2002, 48, 55-63. [45] Rabajczyk A., Bezak-Mazur E. and Widłak M.: Zastosowanie mineralizacji mikrofalowej do analizy specjacyjnej glinu w osadach dennych. Ecol. Chem. Eng./Chem. InŜ. Ekol., 2001, 8, 503-513. [46] Al-Merey R., Al-Masari M.S. and Bozou R.: Cold ultrasonic acid extraction of copper, lead and zinc from soils samples. Anal. Chim. Acta, 2002, 452, 143-148. [47] Elik A.: Ultrasonic-assisted leaching of trace metals from sediments as a function pH, Science Direct. Talanta, 2007, 71, 790-794.

Preparation of bottom deposit samples for speciation analysis of heavy metals

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PRZYGOTOWANIE PRÓBEK OSADÓW DENNYCH DO ANALIZY SPECJACYJNEJ METALI CIĘśKICH Streszczenie: Rosnące zainteresowanie problematyką specjacji wymaga rozwiązywania wielu problemów związanych z przygotowaniem próbek środowiskowych do analizy i jest niezwykle skomplikowane. Proces ten wymaga ogromnej wiedzy dotyczącej zarówno pobierania, transportu, utrwalania, jak i przechowywania próbek. Skutkiem nieprawidłowego postępowania z pobranym materiałem są zachodzące w nim procesy chemiczne, fizyczne oraz biologiczne, które przebiegają bardzo szybko i powodują zmiany charakteru oraz stęŜeń analitów. Wynikiem tego jest błędna ocena stanu środowiska. Aby zapobiec tym procesom, konieczne jest odpowiednie postępowanie z próbką środowiskową w celu przygotowania jej do analizy. Na podstawie literatury dotyczącej wybranych metali (Zn, Cd, Pb, Al) przedstawiono zagadnienia związane z analityką specjacyjną oraz scharakteryzowane zostały podstawowe etapy procedury analitycznej stosowanej do oznaczania specjacyjnego metali cięŜkich w próbkach osadów dennych z uwzględnieniem takich etapów m.in., jak pobieranie i przechowywanie próbek osadów dennych, ekstrakcja, wzbogacanie oraz oznaczanie. Słowa kluczowe: analityka specjacyjna operacyjna, cynk, kadm, ołów, glin, osad denny, pobieranie, konserwacja, przechowywanie, przygotowanie próbek materiału stałego, detekcja