Distribution and mobility of heavy metals

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ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF Distribution and mobility of metals in contaminated sites. Chemometric investigation of pollutant profiles Ornella Abollino a , Maurizio Aceto b , Mery Malandrino a , Edoardo Mentasti a, *, Corrado Sarzanini a , Renzo Barberis c a Department of Analytical Chemistry, University of Torino, Via P. Giuria 5, 10125 Torino, Italy b Department of Science and Advanced Technologies, University of East Piedmont, Corso Borsalino 54, 15100 Alessandria, Italy c Environmental Protection Agency of the Regional Government of Piedmont (ARPA Piemonte), Via della Rocca 49, 10123 Torino, Italy Received 10 July 2001; accepted 9 November 2001 ‘‘Capsule’’: Chemometrics allowed identification of groups of samples with similar characteristics. Abstract The distribution and mobility of heavy metals in the soils of two contaminated sites in Piedmont (Italy) was investigated, evalu- ating the horizontal and vertical profiles of 15 metals, namely Al, Cd, Cu, Cr, Fe, La, Mn, Ni, Pb, Sc, Ti, V, Y, Zn and Zr. The concentrations in the most polluted areas of the sites were higher than the acceptable limits reported in Italian and Dutch legisla- tions for soil reclamation. Chemometric elaboration of the results by pattern recognition techniques allowed us to identify groups of samples with similar characteristics and to find correlations among the variables. The pollutant mobility was studied by extraction with water, dilute acetic acid and EDTA and by applying Tessier’s procedure. The fraction of mobile species, which potentially is the most harmful for the environment, was found to be higher than the one normally present in unpolluted soils, where heavy metals are, to a higher extent, strongly bound to the matrix. # 2001 Published by Elsevier Science Ltd. All rights reserved. Keywords: Heavy metals; Contaminants; Soils; Mobility; Speciation 1. Aim of investigation The problem of contaminated soils is becoming of increasing concern for the environment because of the large number of polluted sites in existence (Ferguson and Kasamas, 1999). The main sources of soil pollution are improper waste dumping, abandoned industrial activities, incidental accumulation (e.g. leakage, corro- sion), atmospheric fallout, agricultural chemicals (Allo- way, 1994). Many contaminated sites date back to two or three decades ago, when environmental legislation on solid and liquid waste disposal was not as strict as nowadays. Before starting the reclamation of a site, the extent and distribution of contamination must be investigated, in order to identify the area to be treated and choose the proper clean-up strategy. A few examples of such investigations, with regard to heavy metal pollution, are the determination of arsenic, chromium and copper in Danish soils after spill of chemicals (Lund and Fobian, 1991), the evaluation of the heavy metal content around a disused mine in Korea (Jeong et al., 1997) and the assessment of arsenic contamination in Germany due to ore and industrial sources (Bombach et al., 1994). The present paper describes the characterisation of heavy metal pollution in the soils of two sites formerly used for industrial waste disposal. The horizontal and ver- tical distribution of contaminants was investigated and the concentrations were compared with the acceptable limits imposed by Italian and Dutch legislation (Minis- try of Housing, 1994; Ministerial Decree, 1999b) for soil reclamation. A chemometric treatment of the data was performed. The toxicity of metals depends not only on their total concentration, but also on their mobility and reactivity with other components of the ecosystem. The most com- mon way to study element mobility in soils is by treat- ment with extractants of different chemical properties 0269-7491/01/$ - see front matter # 2001 Published by Elsevier Science Ltd. All rights reserved. PII: S0269-7491(01)00333-5 Environmental Pollution & (&&&&) &–& www.elsevier.com/locate/envpol * Corresponding author. Tel.: +39-011-6707625; fax: +39-011- 6707615. E-mail address: mentasti@ch.unito.it (E. Mentasti). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF (Nowak, 1995; Szulczewski et al., 1997; Rauret, 1998). In this work the release of metals into water, dilute acetic acid and EDTA was investigated, and the Tes- sier’s partitioning scheme (Tessier et al., 1979) was applied to selected samples. The results obtained can be of use for the local authorities to decide about the necessity of reclamation of the two sites and the level of priority of the interven- tion, with respect to the situation of other polluted areas. Moreover, the data can be of interest to the European Environment Agency for its activities of soil monitoring. 2. Description of the experimental procedures 2.1. Site description The two investigated sites are located in northeast Piedmont, Italy. The first one (hereafter called site A) is in a flat area near the small town of Pieve Vergonte (3000 inhabitants), in the province of Verbania, located about 100 m from a small river. The zone stands on alluvial deposits of the river. The top layers of the soil are made of sand and silt. Groundwater flows at a depth of about 5 m. The contaminated area, whose estimated extension and volume are 5000 m 2 and 17,000 m 3 respectively, is made up of a mixture of industrial wastes and soil. The original soil is almost absent in the area and in its surroundings, because of repeated exca- vations; the soil covering the area, probably carried from nearby zones, is mainly made of gravel and sand. The presence of debris, probably coming from copper and brass foundries, can also be visually detected owing to the presence of coloured (mainly blue-green) spots due to metal salts and of small plastic strips, deriving from wire coatings. The material was not placed in a previously excavated area, but it forms an artificial relief with respect to the surroundings. The zone where the relief lies consists of three levels: the relief itself, an area at ground level, at least twice as wide, and an excavated basin about 7 m deep. The other site (hereafter called site B) is located near the town of Borgomanero (19,400 inhabitants), in the province of Novara. The contamination occurred because of the repeated floods of a small stream, which today has a new course, caused by the insufficient size of the stream bed with respect to the flow in rainy periods. The stream collected wastewaters of local industries, some of which operating in the electroplating field, and its floods caused an accumulation of contaminants, mainly of inorganic nature, in the soil. The extension of the polluted area is estimated between 20,000 and 100,000 m 2 . The core of the contaminated zone is about 3000 m 2 wide: it is a flat, uncultivated area, covered by a layer of black sludge about 1.50 m deep carried by the floods, where a scant vegetation grows. The rest of the area is covered by trees and spontaneous plants. The land in the zone is made of alluvial deposits. The top layer of the soil, down to a depth of from 0.6 to 2 m, is composed of sand with silt and clay, with a low gravel content. This layer gives a discrete impermeability to the soil. Below there is an alluvial layer with sand and gravel, down to groundwater which flows at 4–5 m depth. Table 1 reports a brief description of the location of the single sampling points, which were chosen in a ran- dom fashion in order to cover the whole areas. A total of 33 samples was collected at site A, both at different points of the presumably most contaminated zone and in the surroundings. Some were sampled from the sur- face and others immediately below, at a depth of 10 cm. One specimen was obtained in a hole (1 m deep) dug on the relief. Two pieces of blue-green material were also collected. For comparison, a sample from a park in the city centre was considered. Fifteen samples were col- lected at different depths on one side of the relief, down to 330 cm. At site B 28 samples were collected from the core of the contaminated zone and its surroundings, both at the surface and 10 cm below. Also in this case, one soil specimen from the nearby town nearby was collected. Eleven samples were obtained from different depths, down to 160 cm, from one point in the central area of the core. The collected samples, referred to as ‘‘soil’’ in this paper, when coming from the most polluted areas of the sites, were not strictly ‘‘soil’’ but rather a material cov- ering the original soil, with the characteristics described above (mixture of soil and debris at site A, black sludge at site B). 2.2. Apparatus and reagents Most metal determinations were performed with a Varian Liberty 100 (Varian Australia, Mullgrave, Aus- tralia) inductively coupled plasma–atomic emission spectrometer (ICP–AES). The spectral interference of Fe and V, which have an emission line close to that one of La (379.478 nm), was taken into account by selecting background correction positions outside the interfering peaks. Alternatively, La can be determined at 407.672 nm. Standards for calibrations were prepared in ali- quots of sample blanks. Cadmium and lead, when present below the ICP–AES detection limits, were determined with a Perkin Elmer 5100 (Perkin Elmer, Norwalk, Connecticut, USA) elec- trothermal atomic absorption spectrometer (ETAAS) equipped with Zeeman-effect background correction. Sample dissolutions for the determination of total concentrations were performed in tetrafluormethoxyl (TFM) bombs, with a Milestone MLS-1200 Mega (Milestone, Sorisole, Italy) microwave laboratory unit. Analytical grade reagents were used throughout. Stan- dard metal solutions were prepared from concentrated 2 O. Abollino et al. / Environmental Pollution & (&&&&) &–& 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF Merck Titrisol stock solutions (Merck, Darmstadt, Germany). 2.3. Procedures All experiments were performed in triplicate and blanks were run simultaneously. The relative standard deviations of the results were typically below 10%. Higher deviations were observed, for some data, for extractions in water and acetate, owing to the low con- centrations measured; in some cases also the total concentrations in the polluted area at A site showed a variability higher than 10%, especially for copper, because of the heterogeneity of the samples. The evaluation of pH and EDTA-extractable frac- tions was performed according to the official methods of soil analysis envisaged by the Italian legislation (Minis- terial Decree, 1992). After completion of the experi- mental work, a new revision of official methods was issued (Ministerial Decree, 1999a), which in any case only slightly differs from the previous one. The leaching test with acetic acid was performed according to the Italian official methods for sludge analysis (Water Research Institute, 1985). 2.3.1. Sampling and pretreatment Surface samples were obtained with a trowel (after removing the top layer in contact with the atmosphere) and stored in plastic bags. In-depth samples at site B were collected with the aid of a motor-driven corer. The samples were air-dried and, after breaking the agglom- erates with a plastic hammer, sieved through a 2-mm sieve and ground with a ball mill. 2.3.2. pH Sample pH was determined in sample-water suspen- sions (8 g of sample in 20 ml of water). The suspensions were shaken and left standing overnight before the measurement (Ministerial Decree, 1992). 2.3.3. Sample digestion for total metal determination Aqua regia (5 ml) and 2 ml of hydrofluoric acid were added to 100 mg of sample in TFM bombs and heated in a microwave oven following the sequence: three steps Table 1 Description of sample collection points Site A sample Description Site B sample Description A1 Basin B1 Site core A2 10 cm below A1 B2 10 cm below B1 A3 Ground level B3 Site core A4 10 cm below A3 B4 10 cm below B3 A5 About 5 m far from the site B5 Site core A6 10 cm below A5 B6 Border of site core A7 Ground level B7 10 cm below B6 A8 10 cm below A7 B8 Just outside site core A9 Relief B9 10 cm below B8 A10 0 cm below A9 B10 Just outside site core A11 Relief, 30 m far from A9 B11 10 cm below B10 A12 10 cm below A11 B12 Vertical profile, 0–15 cm A13 Hole in the relief B13 Vertical profile, 15–30 cm A14 Border of the relief B14 Vertical profile, 30–40 cm A15 Coloured material from the relief B15 Vertical profile, 40–50 cm A16 Coloured material from the hole B16 Vertical profile, 50–65 cm A17 Vertical profile, 0–30 cm B17 Vertical profile, 65–80 cm A18 Vertical profile, 30–50 cm B18 Vertical profile, 80–100 cm A19 Vertical profile, 50–60 cm B19 Vertical profile, 100–115 cm A20 Vertical profile, 60–100 cm B20 Vertical profile, 115–130 cm A21 Vertical profile, 100–135 cm B21 Vertical profile, 130–145 cm A22 Vertical profile, 135–155 cm B22 Vertical profile, 145–160 cm A23 Vertical profile, 155–160 cm B23 About 5 m North to the site core A24 Vertical profile, 160–190 cm B24 About 5 m South to the site core A25 Vertical profile, 190–218 cm B25 About 5 m West to the site core A26 Vertical profile, 218–238 cm B26 About 5 m East to the site core A27 Vertical profile, 238–260 cm B27 About 200 m S-E to the site core A28 Vertical profile, 260–280 cm B28 City centre A29 Vertical profile, 280–300 cm A30 Vertical profile, 300–320 cm A31 Vertical profile, 320–330 cm A32 About 400 m far from the site A33 Centre of the town O. Abollino et al. / Environmental Pollution & (&&&&) &–& 3 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF of 5 min each (at a power of 250, 400, 500 W, respec- tively) followed by a final 3 min step at 600 W. Then 0.7 g of boric acid were added and the bombs were further heated for 10 min at 250 W. Finally the samples were filtered and diluted to 100 ml (Bettinelli et al., 1989; Aceto et al., 1994; Gulmini et al., 1994). 2.3.4. Available metal fraction The extractant was a 0.02 mol dm À3 EDTA solution containing 0.5 mol dm À3 CH 3 COONH 4 in 2.5% acetic acid and brought to pH 4.65Æ 0.05. Twenty-five milli- litres of the extractant were added to aliquots of 5.0 g of sample. The suspension was shaken for 30 min, filtered and the extract was analysed (Ministerial Decree, 1992). 2.3.5. Leaching tests Leaching tests were performed with HPW and CH 3 COOH. As to the former, a suspension prepared and treated as described for pH measurement was cen- trifuged and the supernatant was separated and analysed. The leaching test with acetic acid was performed on a suspension of 1.0 g of sample in 16 ml of HPW brought to pH 5Æ0.2 by addition of 0.5 mol dm À3 acetic acid. The suspension was shaken for 24 h; the pH was peri- odically checked and maintained at the original value. Afterwards the suspension was centrifuged and the supernatant was separated and analysed (Water Research Institute, 1985). 2.3.6. Sequential extractions The sample (1.0 g) was sequentially extracted with different reagents according to the following procedure (Tessier et al., 1979): (1) 8 ml of 1 mol dm À3 MgCl 2 , for 1 h, at room temperature; (2) 8.0 ml of 1 mol dm À3 CH 3 COONa, added with CH 3 COOH (pH 5.0), for 5 hours, at room temperature; (3) 20 ml of 0.04 mol dm À3 NH 2 OH. HCl in 25% CH 3 COOH, for 6 h at 96Æ 3  C; (4) 5.0 ml of 30% H 2 O 2 and 3.0 ml of 0.02 mol dm À3 HNO 3 , for 5 h at 85Æ2  C, followed by addition (after cooling) of 5 ml of 3.2 mol dm À3 CH 3 COONH 4 in 20% HNO 3 , dilution to 20 ml, and further extraction for 30 min at room temperature. After each step the suspension was centrifuged, the supernatant was separated and the solid phase was added with the reagents for the subsequent extraction. The extracts were diluted to 25 (first fraction), 50 (sec- ond fraction) and 100 (next two fractions) ml, stabilised by the addition of concentrated nitric acid (25, 50 and 100 ml respectively) and analysed in order to calculate the element percentages extracted in each fraction. The residual element percentages (fifth fraction) were com- puted from the total concentrations by subtraction. The mass balance was evaluated for a few samples by com- paring the total metal content with the sum of the metal percentages extracted in the five fractions after digestion and analysis of the fifth fraction. The recovery was high (i.e. > 90%) for Cd, Cr, Cu, Ni, Pb, Zn (i.e. the heavy metals of greatest interest from the environmental point of view) and Al, whereas Fe, Mn, Ti, V, Zr were par- tially lost (recoveries ranged between 67 and 82%). Zir- conium was mostly lost in the first extraction step, manganese in the fourth one, whereas losses of the other elements took place in all the first four steps, probably during filtration of the surnatant. 2.3.7. Chemometric data treatment Two unsupervised methods (Hierarchical Cluster Analysis, HCA, and Principal Component Analysis, PCA) and a supervised one (Discriminant Analysis, DA) were applied to the data. The treatment was performed with XlStat, an add-in package of Microsoft Excel. HCA was run applying Ward’s method of agglom- eration and squared Euclidean distance as similarity measure. All variables were standardised by transform- ing data into Z-scores (i.e. (xÀx m )/, where x m stands for the average). Dendrograms were obtained. As to DA, two classes were defined a priori, con- sidering samples from sites A and B respectively. Uni- variate ANOVA was used to calculate F-ratios and find out variables with higher discriminating power. Prob- abilities of class membership were calculated for all samples. 3. Results and discussion 3.1. Total metal concentrations Fifteen metals, namely Al, Cd, Cu, Cr, Fe, La, Mn, Ni, Pb, Sc, Ti, V, Y, Zn and Zr, were determined. Tables 2–3 report their concentrations and the pH values, in samples collected at sites A and B respec- tively. The corresponding ranges, averages and medians are reported in Table 4; to allow an easier interpretation of the results, calculations were performed for three groups of data: (1) all samples except A15 and A16, which consist of coloured material, and the vertical profile; (2) all samples except A15, A16, the vertical pro- file and the ones outside the most polluted area; (3) vertical profile. Of course a detailed mapping of the contamination cannot be achieved from the relatively small number of sample points, but the results obtained allow anyway to make some considerations about the distribution and extent of the pollution in the areas. It must be recalled that the considered elements are present in unpolluted soils at what can be defined ‘‘background level’’, both as a result of natural phe- nomena, such as the contribution of the parent material, and of common anthropogenic activities (e.g. agri- culture, traffic, etc.). We can suspect or confirm the pres- ence of pollution when the concentrations are higher than the typical values for soils found in literature and 4 O. Abollino et al. / Environmental Pollution & (&&&&) &–& 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF exceed the levels present in the nearby areas: in fact in some (albeit uncommon) cases high concentrations of one or more elements have a natural origin, as in some soils in California rich in selenium (Halloway, 1990). In this study, in order to assess the presence and extension of contamination, the concentrations of some elements measured at the sites were compared with the normal ranges and the most common values typically present in soils (Halloway, 1990; Merian, 1991) and with the maximum admissible levels in soils according to Italian (Ministerial Decree, 1999a,b) and Dutch (Ministry of Housing, 1994) legislations. These data are collected in Table 5, which also reports, for comparison, the mean content in the earth’s crust (Weast, 1974). 3.1.1. Site A Abnormally high levels of Cd, Cu, Pb and Zn were found at site A. In particular, the presence of copper is related to the disposal of electric cables. The most pol- luted zone is the relief, in which an overall increase of these four elements and, to a lesser extent, of chromium, manganese, nickel and zirconium can be observed. The concentrations of these metals are smaller in the basin, even if a contamination of cadmium, copper, lead and zinc is present. Also the neighbouring zone under the vegetation has relatively high levels of Cu, Pb and Zn. The concentrations at the base of the relief usually fall between the ones in the relief and under the vegetation. The contents of Cr and Ni do not exceed the typical ranges, but in many samples are above the common values reported in Table 5 and, especially in the vertical profile (whose behaviour will be discussed below), are higher than in the surroundings: therefore an input of these elements with the waste can be supposed. The same hypothesis is valid for manganese, whose level in the vertical profile, moreover, is higher than typical values. Some samples on the relief (A9, A10, A12, A13) are also rich in zirconium, which might have been con- tained in the wastes as well. The concentrations found a few hundred meters from the site are not higher than the ones present in the sample collected in the city centre, which can be assumed to be unaffected by the waste disposal which caused the contamination of the site; in both cases the Table 2 Total metal concentrations (mg/kg) and pH at site A Sample pH Al Cd Cr Cu Fe La Mn Ni Pb Sc Ti V Y Zn Zr A1 6.41 62029 16.1 513 426 29092 16.5 737 32.4 301 9.42 3286 39.5 15.8 677 10.3 A2 6.65 65825 21.2 51.3 903 32223 16.6 915 40.5 955 10.3 3196 46.9 15.7 1388 < 10.0 A3 6.68 71971 12.6 110 3592 32972 20.1 1951 68.9 2505 11.0 3296 46.1 17.9 4576 < 10.0 A4 7.16 66443 28.7 102 8270 34185 22.1 2324 77.6 3869 10.2 3138 39.8 19.1 10143 12.0 A5 4.43 65692 3.21 112 1782 37422 23.4 1733 65.0 2867 8.89 3317 44.1 16.3 3918 10.9 A6 4.94 82704 1.21 73.0 744 41108 23.8 917 33.1 432 9.88 3724 44.0 16.1 1153 < 10.0 A7 6.84 69075 15.2 120 5219 33537 20.5 2169 81.0 4682 10.5 2992 42.7 18.2 7834 < 10.0 A8 7.00 70340 18.4 154 7895 33361 21.1 3095 102 5833 9.97 2855 39.9 16.2 13955 10.3 A9 5.52 68388 22.5 190 9957 44939 29.4 3155 185 11083 10.6 3753 45.7 22.1 14532 22.5 A10 5.70 67668 26.3 409 20059 36460 16.9 7313 496 20717 7.54 2565 51.0 12.9 30243 44.4 A11 6.16 62389 22.4 119 15371 40014 20.1 4792 148 9572 8.56 3160 38.0 16.4 20868 11.9 A12 5.43 61670 70.5 134 28172 39964 19.8 7688 290 13553 7.87 2354 31.4 17.1 47681 17.3 A13 6.04 36436 44.1 301 19835 30011 12.7 3050 223 22296 < 2.00 707 26.7 5.81 36963 29.3 A14 5.31 70304 3.11 59.0 2081 39121 27.9 1283 < 30.0 1176 11.3 3924 35.5 23.2 1789 < 10.0 A15 5.99 68293 52.1 200 27992 43949 23.7 4493 239 14750 9.41 2926 54.7 18.7 24850 21.4 A16 5.93 36420 18.4 155 171549 12011 7.62 1879 439 7196 4.97 1226 17.5 6.69 51557 22.3 A17 5.49 66822 126 254 37703 62085 13.4 20604 418 39094 6.39 1706 58.8 10.6 47271 22.6 A18 5.49 54202 160 191 43913 58835 9.99 44724 441 59217 5.30 1271 60.9 8.04 55417 20.6 A19 5.49 54150 34.8 329 26401 20493 16.4 8720 370 21239 5.33 1845 37.1 9.43 36788 53.3 A20 5.74 62791 46.2 499 33697 45163 13.7 2011 477 38014 4.47 1270 36.4 9.57 49912 58.2 A21 5.74 79315 37.3 531 26054 68781 16.7 4435 317 56797 4.78 1486 53.7 8.57 66547 66.3 A22 5.74 68348 44.6 279 13208 19066 14.7 3990 408 19657 5.71 2027 42.8 10.7 45221 64.8 A23 5.88 71978 120 459 22351 59650 15.4 10403 542 35613 4.50 1923 68.4 10.1 54422 46.3 A24 5.88 56434 77.8 302 22627 45086 13.9 18420 282 30069 4.93 1765 57.2 11.0 45304 41.7 A25 5.88 55615 46.3 483 28492 37571 9.4 17050 289 37050 3.00 1051 37.3 7.99 51774 48.7 A26 5.87 64672 62.4 386 26134 48444 14.3 13816 305 33045 4.85 1869 45.6 10.9 45108 39.2 A27 5.87 58161 45.6 311 21575 43769 11.57 10188 255 26449 4.89 1614 43.8 9.45 35475 32.5 A28 5.98 52281 37.7 352 21279 34177 10.2 11675 271 21279 3.44 1219 40.2 8.07 40064 41.0 A29 5.88 54322 48.4 259 20695 39293 12.9 7218 236 22613 4.82 1445 38.4 9.13 31020 31.0 A30 5.75 66399 39.6 356 22712 48785 18.3 6781 341 32283 4.90 1883 48.1 10.3 42636 44.0 A31 5.87 64248 27.8 337 21162 45689 16.7 7721 294 27291 5.58 1814 40.5 11.6 38733 41.1 A32 7.75 61730 < 7.50 47.2 41.8 32877 10.1 705 < 30.0 119 11.2 4115 36.8 16.9 108 < 10.0 A33 6.49 59380 < 7.50 63.8 73.6 45457 12.1 850 < 30.0 69.4 13.5 7600 66.2 14.1 255 < 10.0 O. Abollino et al. / Environmental Pollution & (&&&&) &–& 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF contents of Cr, Cu, Pb, Ni, Mn and Zn are inside the typical ranges. Al, Fe, La, Sc Ti, V and Y concentrations do not show a definite trend as a function of sampling position. The level of iron on the relief is higher than at the base and in the basin, but lower than in the city center: it is likely that the disposed wastes contained iron, causing a local increase in its concentration, even if the levels reached are not abnormal. An input of lanthanum with the wastes may have occurred, since its concentrations are slightly higher at the site than in the city centre and the surrounding area. The pH is lower in the relief than in the surrounding area (except under vegetation). The concentrations of Cd, Cu, Mn, Ni, Pb, Zn and Zr are lower in surface samples than 10 cm below, with a few exceptions. In most cases the levels of La, Sc, Ti, V and Y show the opposite behaviour. There is not a reg- ular trend for Al, Cr or Fe. The concentrations of Cd, Cr, Cu, Mn, Ni, Pb, Zn and Zr in the vertical profile are similar or even higher than the ones found on the relief surface, confirming the presence of a bulk mass of disposed wastes. There is not a regular trend in the concentrations as a function of depth, with the exception of copper which tends to decrease with increasing depth; in any case for many elements (Cd, Cr, Cu, Ni, Pb, Zn, Fe, Zr and V) larger fluctuations and generally higher concentrations are observed in top layers than in deeper ones. The highest value for Al, Cd, Cr, Cu, Fe, Mn, Pb, Zn and Zr is between 30 and 135 cm, whereas the lowest in many cases is below. One of the pieces of material analysed (A15) has con- centrations similar to ones of the relief, whereas the other (A16) has a very high copper level and low con- tent of Fe and of La, Sc, Ti, V and Y. In general the metal distribution is heterogeneous, owing to the heterogeneous mixing of the soil with par- ticles coming from the waste. From the above observations the metals can be divi- ded into four groups: (1) Cd, Cu, Pb and Zn, which are present at very high levels at the site; (2) Cr, Mn and Ni, by which the site is supposed to be contaminated (see also the discussion on legislation below), but to a lesser extent; (3) Fe, La and Zr, in which an input from wastes is supposed but whose level is not a sign of pollution; (4) Al, Sc, Ti, V and Y whose concentrations in the pol- luted area and in the surroundings are similar. There- fore it can be presumed that the elements of the first three groups have both geochemical and (to different extents) anthropogenic sources, whereas the ones of group four have mainly a geochemical origin. Table 3 Total metal concentrations (mg/kg) and pH at site B Sample pH Al Cd Cr Cu Fe La Mn Ni Pb Sc Ti V Y Zn Zr B1 5.00 58931 4.75 3593 5753 29933 28.3 259 1418 687 9.07 4712 43.9 20.2 679 42.8 B2 4.06 58150 8.05 2880 4013 29246 33.9 251 741 864 8.61 5027 43.6 19.5 417 44.8 B3 5.17 50390 5.54 3016 5743 29022 27.4 265 1983 703 3.20 3808 40.9 19.8 1053 42.4 B4 4.51 48639 2.74 3160 5032 28635 26.8 230 1140 657 7.26 4105 40.9 17.1 598 40.5 B5 4.97 64379 0.98 312 3953 29966 32.5 281 969 533 8.02 4611 36.7 19.1 517 38.0 B6 5.80 64067 0.54 4523 7657 28501 41.7 259 1964 1162 9.86 6273 46.3 22.0 868 50.9 B7 6.08 64961 3.03 3905 4092 29487 24.4 240 1021 393 8.23 5172 50.0 12.1 723 54.2 B8 5.30 31514 0.17 2781 2485 19005 19.8 521 1471 675 5.46 3888 27.2 13.6 738 20.9 B9 5.66 59799 0.15 2101 1537 27674 23.8 328 856 244 8.53 4693 40.9 11.9 618 51.5 B10 5.22 61453 1.34 179 3151 34306 24.6 372 1142 621 7.32 4613 43.4 17.9 849 38.5 B11 4.96 55802 1.43 338 5778 30075 21.9 259 1272 751 5.79 5273 38.6 14.9 804 37.8 B12 4.41 63029 0.84 3123 3478 29412 31.8 265 697 156 9.50 4431 38.2 23.1 346 43.6 B13 3.92 67849 1.37 4683 3310 31394 31.7 258 648 159 9.79 5978 37.1 22.9 466 43.8 B14 3.81 88936 0.55 299 1019 39147 27.7 311 128 15.7 12.8 3947 46.3 16.7 191 60.3 B15 3.43 86985 2.96 140 787 36757 26.3 320 261 10.3 11.9 3741 55.0 16.9 393 65.5 B16 3.42 83775 2.87 199 1721 33967 23.2 348 412 10.3 11.7 3588 52.3 19.0 713 59.6 B17 3.99 81668 0.89 184 373 36370 31.6 455 1037 10.4 11.9 3689 47.2 20.5 957 45.0 B18 5.49 78555 0.22 128 80.0 37125 26.2 473 132 9.16 11.4 3691 51.7 18.4 147 47.0 B19 4.56 77734 0.61 860 1110 35784 28.8 391 406 57.6 11.3 3916 49.0 19.8 355 47.5 B20 5.63 72181 0.12 170 126 33379 25.3 404 98.0 11.7 10.4 3350 49.5 17.8 127 35.2 B21 6.05 73021 0.14 152 82.0 36502 19.2 437 179 8.33 12.1 3638 53.1 16.5 142 33.6 B22 5.74 71518 0.10 < 20.0 86.2 39333 17.4 624 158 5.59 11.5 3773 43.7 15.1 138 66.5 B23 5.75 50079 < 0.05 2958 2075 34372 24.5 269 863 664 < 2.00 5365 57.8 10.8 909 63.6 B24 4.16 45356 < 0.05 55.28 74.3 38252 29.2 337 33.0 21.0 3.18 3782 56.5 3.48 109 88.9 B25 4.17 41888 < 0.05 37.7 62.6 28110 17.8 394 30.1 293 3.88 3210 37.3 5.66 108 67.2 B26 5.24 54600 < 0.05 752 2148 27877 23.5 591 222 355 7.84 3344 32.3 13.5 853 48.7 B27 5.53 62844 1.14 49.7 26.8 30382 26.2 338 32.4 54.2 7.62 3574 48.4 10.9 103 87.0 B28 7.01 57323 < 0.05 68.3 20.6 43176 28.3 779 31.3 28.1 11.3 6038 23.8 18.9 125 36.8 6 O. Abollino et al. / Environmental Pollution & (&&&&) &–& 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF 3.1.2. Site B High concentrations of Cd, Cu, Cr, Ni, Pb and Zn were found at site B. In particular, the presence of Cr and Ni could be due to an input from factories manufacturing taps and fittings. The contamination is spread all over the core of the site, and below the vegetation growing just outside it. At a short distance from the core (points B23, 24, 25, 26) there is still a certain level of contamination, but less pronounced than in the core; there are some exceptions, such as the high levels of Cr, Pb and Zn in sample B23. Metal concentrations are within normal ranges about 200 m from the site and in the city centre. No enrichment of Mn, Al, Fe, Sc, Ti, V or Zr in the site is observed. A few samples (e.g. B2, B6) have a relatively high concentration of lanthanum, but it is not possible to say whether it is due to contamination. A decrease in metal concentration from the surface to the layer underneath was observed in many cases. As to the vertical profile, the concentrations of Cd, Cr, Cu, Ni and Pb, are higher in the top layers, and tend to decrease below 40 cm. Many data in the lower layers are above the common values (Table 5) but still within the typical ranges, even if some local maxima are pres- ent, such as for Ni (sample B17), Cd (B15–B16) and for Cr, Cu and Pb (B19). The concentrations of zinc increases down to 80 cm. A general trend to higher values at depth than on the surface is observed for Al, Fe, Mn, Sc, V and Y. The concentrations of La and, partially, of Ti tend to decrease with depth, whereas those of zirconium do not show any trend. The pH value is lower than 4 at a depth of between 15 and 80 cm: it is likely that this low value is due to an input of acidic wastewater. In general, the metals can be divided into two groups: (1) Cd, Cr, Cu, Ni, Pb and Zn, whose concentrations are heavily affected by anthropogenic inputs, and (2) Al, Fe, Mn, Sc, Ti, V and Zr, which are mainly of geo- chemical origin. 3.1.3. Legislation limits The results were compared with the maximum acceptable concentrations in soils reported in the Table 4 Mean, median, ranges of total concentrations (mg/kg) at sites A and B Site Mean a Median a Range a Mean b Median b Range b Mean c Median c Range c pH A 6.16 6.29 4.43–7.75 6.02 5.74 5.31–6.16 5.77 5.87 5.49–5.98 B 5.21 5.22 4.06–7.01 5.16 5.17 4.06–6.08 4.59 4.41 3.42–6.05 Al A 65128 66134 36436–82704 65781 62030 36436–70304 61983 62791 52281–79315 B 54716 57323 31514–64961 56190 58931 31514–64961 76841 77734 63029–88936 Cd A – 17.3 1.21–70.5 21.8 33.25 3.11–70.5 63.6 46.2 27.8–160 B – 0.98 < 0.05–8.05 2.61 1.43 0.15–8.05 0.97 0.61 0.10–2.96 Cr A 131 111 47.2–409 142 127 59.0–301 355 337 191–531 B 1806 2101 37.7–4523 2435 2880 179–4523 – 184 < 20.0–4683 Cu A 7776 4406 41.8–28172 8879 17603 2081–28172 25867 22712 13208–43913 B 3153 3151 20.6–7657 4472 4092 1537–7657 1107 787 80.0–3478 Fe A 36421 35323 29092–45457 36029 39543 3011–40014 45126 45163 19066–68781 B 30472 29487 19005–43176 28714 29246 1900–34306 35379 36370 29412–39333 La A 19.6 20.1 10.1–29.4 20.8 20.0 12.7–27.9 13.8 13.9 9.40–18.3 B 26.7 26.2 17.8–41.7 27.7 26.8 19.8–41.7 26.3 26.3 17.4–31.8 Mn A 2667 2060 705–7688 2937 3921 1283–7688 12517 10188 2011–44724 B 351 281 230–779 297 259 230–521 390 391 258–624 Ni A – 73.3 < 30.0–496 – 186 < 30.0–290 350 317 236–542 B 893 969 30.1–1983 1271 1142 741–1983 378 261 98.0–1037 Pb A 6252 3368 69.4–22296 7132 11563 1176–22296 33314 32283 19657–59217 B 512 621 21.0–1162 663 675 244–1162 41.2 10.4 5.59–159 Sc A – 10.1 < 2.00–14 – 8.22 < 2.00–11.3 4.86 4.89 3.00–6.39 B – 7.62 < 2.00–11.3 7.40 8.02 3.20–9.86 11.3 11.5 < 2.00–12.8 Ti A 3374 3241 707–7600 3019 2757 707–3924 1613 1706 1051–2027 B 4558 4613 3210–6273 4743 4693 3808–6273 3977 3741 3350–5978 V A 42.1 41.3 26.7–66.2 40.8 3305 26.7–38.0 47.3 43.8 36.4–68.4 B 41.7 40.9 23.8–57.8 41.1 40.9 27.2–50.0 47.6 49.0 37.1–55.0 Y A 16.5 16.4 5.81–23.2 16.6 16.8 5.81–23.2 9.70 9.57 7.99–11.6 B 14.8 14.9 3.48–22.0 17.1 17.9 11.9–22.0 18.8 18.4 15.1–23.1 Zn A 12255 6205 108–47681 13980 28916 677–47681 45713 45221 31020–66457 B 592 679 103–1053 715 723 417–1053 361 346 127–957 Zr A – 10.3 < 10.0–44.4 – 14.6 < 10.0–29.3 43.4 41.7 20.6–66.3 B 50.3 44.8 20.9–88.9 42.0 42.4 20.9–54.2 49.8 47.0 33.6–66.5 a All samples excluding A15, A16 and the vertical profile (A1–A14 and A32–A33; B1–B11 and B23–B28). b All samples excluding A15, A16, vertical profile and the ones outside the most polluted area (A1–A14; B1–B11). c Vertical profile samples (A17–A31; B12–B22). O. Abollino et al. / Environmental Pollution & (&&&&) &–& 7 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF Italian legislation 6 for the reclamation of contaminated sites and with Dutch intervention values (Ministry of Housing, 1994), formerly known as C values (Table 5). Italian limits depend on land use, and are lower for public and private green areas and residential sites (‘‘A’’ limits) and higher for industrial areas (‘‘B’’ limits). At site A, the levels of Cd, Cu, Pb and Zn exceed ‘‘A’’ and ‘‘B’’ limits in most samples; the concentrations of Cr and Ni are higher than ‘‘A’’ limits, but below ’’B’’ ones. Copper, chromium and nickel contents at site B are above both limits in many samples, whereas lead and zinc, and in some cases cadmium, are between ‘‘A’’ and ‘‘B’’ values. All samples exceeding ‘‘A’’ and some of the samples exceeding ‘‘B’’ levels have concentrations above Dutch intervention values, which are intermediate between the two Italian sets of limits, and are to be considered, according to the official terminology, ‘‘seriously pol- luted’’. 3.1.4. Chemometric processing The results were processed by PCA and HCA, in order to obtain a visual representation of the data set and gain insight into the distribution of the pollutants by detecting similarities or differences which would be more difficult to identify only by looking at the tables. As to PCA, both scores, which allow us to recognise groups of samples with similar behaviour, and loadings, which show the correlation among variables, were evaluated and reported as biplots. The first three PCs were computed, but only PC1 and PC2 gave useful information. The data for the horizontal (including 10 cm depth) and vertical profiles were processed both together and separately: the results of the separate treatment will be described hereafter, and hints on the joint processes, which provided little further informa- tion, will be given. This paper reports some PC and dendrogram plots, as an example, for this and the fol- lowing sections. All other PCA and HCA plots are available on request from the authors. As to site A, the following observations can be made: for the data set relative to the horizontal profile, the variance explained by the first two PCs is 22 and 49% respectively (71% in all). The plot of PC1 vs. PC2 is reported in Fig. 1a; in this figure, as well as in the other PCA plots shown in the paper, the position of the loadings is marked with a squared frame. Fig. 1a shows a certain degree of similarity for samples A1– A8, which were collected outside the relief, but still at the site or very close to it. Samples A32 and A33, collected outside the polluted area, are somewhat apart but not very far from them. The specimens from the relief (A9–A13, with the exception of A14) are in other zones of the plot. They are distanced from each other, owing to the heterogeneity of the wastes. The combined plot shows that they are mainly characterized by high concentrations of the polluting elements. One of the pieces of material (A16) is com- pletely isolated from the other samples, confirming its different characteristics, and is strongly characterised by its copper content; the metals belonging to the first two above identified groups, together with zirconium, are correlated, with the exception of copper which stands alone. They have opposite values of PC1 with respect to the other Table 5 Typical concentration ranges and most common values present in soils, average abundance in the earth’s crust, acceptable concentrations in soils for Italian legislation (A: limits for public and private green areas and residential use; B: limits for commercial and industrial use of soil), target and intervention values for Dutch legislation (values in mg/kg unless otherwise stated) Range Common values a Earth’s crust Limit (A) Limit (B) Target value Intervention value pH 4–8.5 Al 81,300 Cd 0.01–2.0 0.2–1 0.15 2 10 0.8 12 Cr 5–1500 70–100 200 150 800 100 380 Cu 2–250 20–30 70 120 600 36 190 Fe 0.7–4.2% 50,000 La 18 Mn 20–10,000 1000 1000 Ni 2–750 50 80 120 500 35 210 Pb 2–300 10–30 (rural) 16 100 1000 85 530 30–100 (urban) Sc5 Ti 4400 V 3–500 90 150 90 250 Y 2.5–250 28 Zn 1–900 50 132 150 1500 140 720 Zr 220 a Values for agricultural soils 8 O. Abollino et al. / Environmental Pollution & (&&&&) &–& 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF elements: this component may therefore be connected to their origin. The pH is anticorrelated to most of the pollutants; two main groups can be identified from the dendro- gram reported in figure 1b: one is made by most samples from the relief and by the two pieces of material; the second group contains the other samples and it is possible to distinguish: (1) sample A33 (city centre) which stands on its own; (2) group A3-A4-A7- A8, coming from the ground level; for the data regarding the vertical profile, the variance explained by the first two PCs is 34 and 24 respec- tively (58% in all). In the plot of PC1 vs. PC2 (not shown) samples A17 and A18, corresponding to the first two layers, stand out because of the high con- centrations of Cd, Cu, Mn, Fe (for A17) and Zn (for A18). A21 and A23 form a separate group due to the high content of Al, Fe, Pb, La, Zn and Zr (for A21), and Al, Fe, Cd, Ni, Ti, V and Zn (for A23). No sig- nificant distribution can be identified for the other samples, apart from the close resemblance of A20 and A24; as to the loadings, the polluting elements are less strictly correlated than in the horizontal profile, even if they are in the same area of the plot and load posi- tively on PC1, with the exception of Zr and Cr. pH is anticorrelated to this groups of variables. V and Fe behave like the pollutants, whereas Al, Sc, La, Ti and Y are in other areas of the plot. It can be supposed that PC1 is connected to the elements of mainly anthropogenic origin and PC2 to the ones of a mainly geochemical source; HCA confirms the different characteristics of the first two layers; when the data for site A are processed all together, the variance explained by the first two PCs is 50 and 19% respectively (69% in all). The samples for ver- tical and horizontal profiles form two groups in the plot of PC1 vs. PC2, the former being characterised by their content in polluting elements; exceptions to this distribution are A10 and A13, which show a stronger similarity with the vertical samples, and A16, the piece of material, which is isolated from the other specimen. Two clusters corresponding to horizontal and vertical (plus A10, A13, A16) profile samples are also present in the dendrogram. Data processing for site B gave the following results: as to the horizontal profile, the variance explained by the first two PCs is 38 and 19% respectively (57% in all). According to the plot of PC1 vs. PC2 (Fig. 2a) samples B1–B11, collected in the core or just outside, and B23–B27, from the surroundings, form two groups; samples B8 and B9, collected under the vege- tation grown just outside the site core, have a stron- ger similarity to the second group. Sample B28 from the city centre is clearly differentiated from all the others. Group B1–B11 is characterized by the pre- sence of the polluting elements. Sample B6 stands out because of its high content of Cr, Cu, La, Pb and Zn; the correlation among the elements identified as pol- lutants (Cd, Cr, Cu, Ni, Pb, Zn) is evident. Such ele- ments are anticorrelated to Mn and Fe. A weak correlation is also present among Al, La, Sc, Ti and Y. The pollutants have high positive loading on PC1: this component therefore takes account of the pollu- tion of the site. On the other hand, PC2 is influenced by the elements of mainly geochemical origin. Sur- prisingly, pH is unrelated to the pollutants: a high pH value would be expected to be connected to high metal concentrations because it stabilises metal oxide and hydroxide forms and reduces their mobility; the dendrogram in Fig. 2b confirms the different characteristics of specimen B28 and, apart from sam- ples B23 and B26, the division between groups B1– B11 and B23–B27. The closeness of most samples coming from the core of the site (B1–B4), is also apparent; as to the vertical profile, the variance explained by the first two PCs is 51 and 23% respectively (74% in all). The scores on PC1 of the first two layers (B12 and Fig. 1. Combined plot of scores and loadings obtained by (a) PCA and (b) dendrogram for horizontal profile samples at site A (total metal concentrations). O. Abollino et al. / Environmental Pollution & (&&&&) &–& 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 ENPO 2364 Disk used No. pages 17, DTD=4.3.1 Version 7.5 ARTICLE IN PRESS UNCORRECTED PROOF B13) are very different from those of the layers below. A differentiation between groups B14–B17 and B18– B22 (with sample B19 as an outlier) is also present; the group of the polluting elements is more scattered than in the horizontal profile, but it still has loadings on PC1 of the opposite sign with respect to many elements of a mainly geochemical source. PC1 is almost unaffected by pH, which on the other hand heavily loads on PC2. pH is anticorrelated to Cd and Zn and, at a lower level, to Ni, La, Zr, Al; HCA confirms the observations made above: the first two layers from a separate cluster, and groups B14- B17 and B18-B22 are again present, with sample B19 being closer to the former; when all data for site B are considered together, the variance explained by the first three PCs is 38 and 18% respectively (56% in all). The sampling locations can be divided into three main groups: (1) the hor- izontal profile in the site core or just outside it (B1– B11), together with the first two layers of the vertical profile (B12–B13), characterized by a high content of contaminants; (2) the deeper layers of the vertical profile (B14–B22); (3) the samples collected in the surroundings of the site (B24–B27), excluding B23, and in the city centre (B28). The corresponding den- drogram showed a similar clustering. The data for sites A and B were also treated together. The variance explained by the first two PCs is 40 and 17% respectively (57% in all). Three groups are present, corresponding to (1) most A samples, (2) B samples from the horizontal profile, (3) vertical B samples and some A ones. A samples are characterized by their con- tent in Cu or Cd, Pb, Zn, Mn, and B ones by Cr and Ni. Specimens from A and B sites are also differentiated in the dendrogram. Data processing with DA allowed us to identify all samples as belonging to the expected classes (> 99.9% probability), i.e. to the site of collection, except B20, which was classified as ‘‘A’’ type, and B21, which was assigned to the correct class but with 74.5% probability. The two pieces of materials (A15 and A16) were exclu- ded from the data set because they were not actually ‘‘soil’’ samples. The variables with the highest dis- criminating power were Cd (F=31.79), Cu (F=36.50), La (F=51.72), Pb (F=35.92), Ti (F=37.02), Zn (F=50.28). The tabulated F value for a confidence level of 95% is 4.00. 3.2. Mobility Extraction studies were carried out in order to inves- tigate the mobility of the metals and therefore their possible release into the environment and their toxicity. Experiments were carried out by extraction with reagents of different chemical properties, in order to identify fractions of analytes with different labilities. Extractions with water and EDTA solutions were per- formed on samples from the depth profiles. The first layers at site A were mixed together (three by three) in order to have a sufficient amount of specimen for all experiments. The leaching test with acetic acid, per- formed at pH 5.0 according to Italian official methods of sludge analysis (Water Research Institute, 1985), was applied only to site A, because the pH of the water sus- pensions of most site B samples was already lower than 5.0. Tessier’s protocol was applied to two samples for each site. PCA and HCA were performed on the percentages extracted in water, acetic acid and EDTA. 3.2.1. Leaching with water The leaching test with pure water was performed in order to evaluate the fraction of metals weakly bound to the matrix, e.g. present as inorganic soluble salts. The results can also give a preliminary indication on the possible release of pollutants by rains, although of course the laboratory experimental conditions are dif- ferent from the on-site situation. Moreover, it is likely that most of the very labile metal fraction has already been leached over the years. The percentages of metals solubilised by water, their median and ranges are reported in Table 6. As can be seen, the extracted Fig. 2. Combined plot of scores and loadings obtained by (a) PCA and (b) dendrogram for horizontal profile samples at site B (total metal concentrations). 10 O. Abollino et al. / Environmental Pollution & (&&&&) &–& 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 [...]... 293, 15 December 1999 Ministry of Housing, 1994 Spatial Planning and the Environment Intervention and Target Values—Soil Quality Standards The Netherlands Nowak, B., 1995 Sequential extraction of metal forms in the soil near a roadway in southern Poland Analyst 120, 737–739 Rauret, G., 1998 Extraction procedure for the dewtermination of heavy metals in contaminated soil and sediment Talanta 46, 449–455... partitioning of the new national Institute of Standards and Technology Standard Reference Materials by sequential extraction using ICP AE Spectrometry Analyst 120, 1415–1419 Lund, W., 1990 Speciation analysis—why and how? Fresenius J Anal Chem 337, 557–564 Lund, U., Fobian, A., 1991 Pollution of two soils by arsenic, chromium and copper, Denmark Geoderma 49, 83–103 Merian, E., 1991 Metals and their Compounds... extractions of calcium, copper, iron and manganese in a Lagoon Sediment Analyst 119, 2075–2080 Halloway, B.J., 1990 Heavy Metals in Soils Blackie, London Hani, H., 1990 The analysis of inorganic and organic pollutants in soil with special regard to their bioavailability Intern J Environ Anal Chem 39, 197–208 Jeong, J.H., Song, H.J., Jeong, G.H., 1997 Depth profiles and the behaviour of heavy metal atoms... our experience, the fractions of heavy metals such as Cu, Pb and Zn, extracted by EDTA in unpolluted soils are much lower (a few percentage units), because they bind more to the soil matrix, although the trend of the higher lability of bivalent metals still exists Cr, whose total concentration is also influenced by the work of man, is only weakly released, probably because of its inertness Therefore the... 81 82 83 84 85 The high pollutant mobility favours their release into the environment and hence their potential harmfulness 86 87 88 89 4 Conclusions 90 91 The investigation on the two sites allowed us to identify the nature of the pollutants and to give a preliminary indication of the extension of the contamination If a deeper understanding of the characteristics of the area is required, the guidance... layers, in the plot of PC1 vs PC2 The distribution of variable loadings is different from the one observed with leaching in water or acetate, due to the different extraction mechanism involved Cu, Zn, Mn and Cd are correlated, and anticorrelated to Pb Trivalent elements lay in one quadrant of the plot (together with Ti and Ni) whereas the two other elements at high valence state, Zr and V, are scattered... (A9 and B1) and the other from a deeper layer (A20, 60–100 cm and B17, 65– 80 cm) The percentages of metals in the five fractions are reported in Table 9 Of course, when considering these data, the extent of metal recovery (see Section 2.3.6) must be taken into account It must be borne in mind that, as with any speciation scheme for soil, these results are operationally defined, since the phenomena of. .. speciation scheme for soil, these results are operationally defined, since the phenomena of redistribution and adsorption usually take place during extractions: in any case the partitioning of the metals into five fractions gives an indication of their reactivity and hence of their availability to the environment and their potential harmful effects Exchangeable elements are present at site A at very low... copper The third fraction mainly contains Cu, Zn and most Mn, but also significant amounts of other elements such as Cd, Cr and Fe Low percentages (generally < 5%) are present in the fourth fraction The highest levels ( > 90%) of several elements are in the residual fraction, which on the other hand contains only 20% or less of Cu and Mn In many cases the order of extractability in the fractions is 1< 2 . allowed identification of groups of samples with similar characteristics. Abstract The distribution and mobility of heavy metals in the soils of two contaminated. 7.5 ARTICLE IN PRESS UNCORRECTED PROOF Distribution and mobility of metals in contaminated sites. Chemometric investigation of pollutant profiles Ornella Abollino a ,