Organochlorine compounds in soils and sediments of the mountain Andean Lakes

Environmental Pollution 136 (2005) 253e266 www.elsevier.com/locate/envpol

Organochlorine compounds in soils and sediments of the mountain Andean Lakes Francesca Borghinia, Joan O. Grimaltb,*, Juan C. Sanchez-Hernandezc, Ricardo Barrad, Carlos J. Torres Garcı´ ae, Silvano Focardia a Department of Environmental Sciences, University of Siena, Via Mattioli 4, 53100 Siena, Italy Department of Environmental Chemistry (ICER-CSIC), Jordi Girona 18, 08034 Barcelona, Catalonia, Spain c Laboratory of Ecotoxicology, University of Castilla-La Mancha, Avda. Carlos III, s/n, 45071 Toledo, Spain d Aquatic Systems Research Unit, EULA - Chile Environmental Sciences Centre, University of Concepcion, Casilla 160-C, Concepcion, Chile e Izan˜a Atmospheric Observatory, National Institute of Meteorology, La Marina 20, 38071 Santa Cruz de Tenerife, Canary Islands, Spain

b

Received 30 April 2004; accepted 6 January 2005

Distribution of persistent organochlorine compounds in the Andean Mountain lakes is influenced by temperature. Abstract Semi-volatile organochlorine compounds (OC) were analyzed in remote Andean soils and lake sediments. The sampling sites covered a wide latitudinal gradient from 18
S to 46
S along Chile and an altitudinal gradient (10e4500 m). The concentrations were in the order of background levels, involving absence of major pollution sources in the high mountain areas. Significant correlations were found between log-transformed concentrations of hexachlorobenzene, a- and g-hexachlorocyclohexane in soils and total organic content (TOC). In addition, TOC-normalized concentrations of the most volatile OC showed a significant linear dependence with air temperature. This good agreement points to temperature as a significant factor for the retention of long range transported OC in remote ecosystems such as the Andean mountains, although other variables should not be totally excluded. The highest concentrations of OCs were achieved in the sites located at highest altitude and lowest temperature of the dataset. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Organochlorine compounds; Andean range; Long range transport; Soil; Lake sediments

1. Introduction The physico-chemical properties of organochlorine compounds (OCs) such as chemical stability and semivolatility afford their transport to long distances from their point of release, and condense in the colder regions of the earth (e.g., Arctic and Antarctica). The latitudinal distribution of these compounds as a consequence of the * Corresponding author. Tel.: C34 93 4006122; fax: C34 93 2045904. E-mail address: [email protected] (J.O. Grimalt). 0269-7491/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.envpol.2005.01.007

temperature gradients has been described to respond to a ‘‘global distillation effect’’ (Muir et al., 1990; Wania and Mackay, 1995, 1996). The atmospheric long-range transport of OCs toward higher latitude regions of the northern hemisphere has been documented (Simonich and Hites, 1995; Lohmann et al., 2001). Temperature gradients are also defined in mountain regions. Again, the ‘‘global distillation’’ process should involve transfer of the OC compounds from low to high altitudes. Recent studies on OC concentrations in fish and sediments collected from high mountain European lakes (Grimalt et al., 2001), soil samples in the Teide mountain (Canary

254

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

Islands, Spain; Ribes et al., 2002) and snow samples in western Canada (Blais et al., 1998) have shown that this temperature-dependent transfer effectively occurs and that OCs tend to accumulate in high altitude areas. Contrarily, there is a scarcity of data supporting an atmospheric transport for OC pollutants in the southern hemisphere leading to enrichment of OCs in cold remote areas. Although these compounds have been found in remote cold areas such as Antarctica (Larsson et al., 1992; Weber and Goerke, 1996), the knowledge concerning a temperature-dependence of their geographical distribution in the southern hemisphere is still incomplete. The aim of this study was to examine the altitudinal and latitudinal distribution of OC contaminants in the southern hemisphere to give evidence of a temperaturedependent accumulation in cold remote areas. The study was carried out in remote lakes distributed in the Andean range (Chile). The OC compounds pentachlorobenzene (PeCB), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), 4,4#-DDE, 4,4#-DDT and PCBs were analyzed in soil samples of the lake catchments and in sediment samples collected in some lakes. Soils were selected for study because of their absorption capacity of atmospherically transported pollutants (Harner and Mackay, 1995). Lake sediments witness compound accumulation after water column transport; they were sampled whenever possible.

2. Materials and methods 2.1. Materials Residue analysis n-hexane, dichloromethane, isooctane, methanol and acetone were from Merck (Darmstadt, Germany). Anhydrous sodium sulfate for analysis and powder copper (size !63 mm) were also from Merck. Neutral aluminum oxide type 507C was from Fluka AG (Buchs, Switzerland). Cellulose extraction cartridges were from Whatman Ltd (Maidstone, England). Aluminum foil was rinsed with acetone and let dry at ambient temperature prior to use. The purity of the solvents was checked by gas chromatography-electron capture detection (GC-ECD). No significant peaks should be detected for acceptance. Aluminum oxide, sodium sulfate and cellulose cartridges were cleaned by Soxhlet extraction with dichloromethane:methanol (2:1, v/v) during 24 h before use. The purity of the cleaned reagents was checked by ultrasonic extraction with n-hexane:dichloromethane (4:1; 3!20 mL), concentration to 50 mL and analysis by GC-ECD. No interferences were detected. Sodium sulfate and aluminum oxide were activated overnight at 400
C and 120
C, respectively. Copper was activated by sonication with 35.5% hydrochloric acid (3!3 mL) and then rinsed several times with Milli-Q water to neutral pH and, subsequently, with acetone for

water removal. This powder was stored under n-hexane prior to use (not later than 2 days after activation). PeCB, HCB, a-HCH, g-HCH, 4,4#-DDE, 4,4#-DDT and the PCB congeners nos. 18, 28, 30, 52, 70, 90, 101, 105, 110, 118, 123, 132, 138, 149, 153, 158, 160, 180, 194, 199 and 209 were from Cromlab (Barcelona, Catalonia, Spain). Standard mixtures in isooctane were prepared with these compounds for instrumental calibration. Surrogate solutions of PCB congeners #30 and #209 were prepared for recovery calculation. 1,2,3,4-Tetrachloronaphthalene (TCN) and octachloronaphthalene (OCN) were from Dr Ehrenstorfer (Augsburg, Germany). These compounds were used for the preparation of surrogate solutions for assessment of instrument stability. 2.2. Sampling Field sampling was conducted during July and August 1999 in remote areas distributed along the Andean range in Chile (Fig. 1). In several sampling sites it was possible to take lake sediment samples. Lakes from the northern Chile (Chungara, Surire, Cotacotani lakes) are situated above 3000 m a.s.l. (Table 1), and the central (Laja lake) and southern lakes (Castor, Venus, Risopatron lakes) are located below 800 m. Soil samples (0e5 cm depth) were taken after removal of the fresh surface litter, and the sediment samples were obtained by coring in the deepest part of each lake using a gravity coring system. Sediment cores were immediately divided into sections of 1 cm and only the surface (0e1 cm section) sediment was considered for the OC residues analysis. Samples were wrapped up with pre-rinsed aluminum foil, and frozen at 20
C in the laboratory. Samples were lyophilized and homogenized before analysis of OC residues. 2.3. Sample extraction and clean up Samples were weighed into Whatman Soxhlet cellulose thimbles, spiked with PCB congeners #30 and #209 and extracted with hexane:dichloromethane (4:1) for 16 h. All extracts were first concentrated by rotary vacuum evaporation to 1 mL and fractionated by column chromatography using 3 g of neutral alumina. OC were obtained by elution with 8 mL of hexane:dichloromethane (9:1). In the soil and sediment samples, activated copper (w0.5 g) was added to the eluate for removal of sulfur-containing compounds. This copper powder was removed by filtration though glass wool and rinsed with n-hexane. Elution solvent and rinses of soil and sediments extracts were concentrated to 50 mL in isooctane after rotary vacuum and nitrogen stream evaporation. 2.4. Instrumental analysis The extracts were injected into a Hewlett Packard 5890 Series II GC-ECD (Palo Alto, CA). A DB-5 fused

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

255

Fig. 1. Locations of the Andean Lakes under investigation for this study.

silica capillary column (30 m length, 0.25 mm i.d, 0.25 mm film thickness) coated with 5% phenyl 95% methylpolysiloxane was used for the analyses. The oven temperature program started at 90
C (holding time 2 min), increased to 150
C at 15
C min1 and finally to 280
C at 4
C min1 (holding time 10 min). Injector and detector temperatures were 270
C and 310
C, respectively. Helium was used as carrier gas (50 cm s1). Injection was performed in splitless mode, keeping the split valve closed for 35 s. Nitrogen was used as make-up gas (60 mL min1). Compound identification was confirmed by GC coupled to mass spectrometry in the chemical ionization mode and negative ion recording (Fisons 8000 Series, Mass Selective Detector 800 Series; ThermoQuest, Manchester, UK). The gas chromatograph was equipped with a non-polar fused silica capillary column HP-5-MS (30 m!0.25 mm i.d.!0.25 mm film thickness). Helium was used as carrier gas (1.1 ml min1). The oven temperature was programmed from 80
C (1 min) to 120
C at 15
C min1 and then to 300
at 4
C min1 with a final holding time of 10 min. The samples were injected in split/splitless mode (48 s) at 280
C (hot needle technique) and data acquisition started after a solvent

delay of 4 min. Ion source and transfer line temperatures were 150 and 280
C, respectively. Ammonia was used as reagent gas. Ion source pressure (currently 1.6 torr) was adjusted to maximize the perfluorotributylamine ions (m/z 312, 452, 633 and 671). Ion repeller was 1.5 V. Data were scanned from m/z 50 to 450 at 1 s per decade. Data were also acquired in selected ion monitoring mode with dwell time and span of 0.06 s and 0.10 a.m.u., respectively. 2.5. Quantification OCs were identified by retention index comparison by reference to tetrachloronaphthalene (TCN) and octachloronaphthalene (OCN). In some cases, structural identification was confirmed by GC-MS-NICI. Solutions of TCN and OCN were added to the vials prior to injection. Calibration curves (detector response vs amount injected) were performed for each compound to be quantified. The range of linearity of the detector was evaluated from the curves generated by representation of detector signal/amount injected vs amount injected. All measurements were performed in the ranges of linearity found for each compound. In some cases, the samples were rediluted and reinjected for fitting within the linear

256

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

Table 1 Sample site description and concentrations of the major organochlorine compounds in sediments and soils (ng g1 dw) Sampling sites

Latitude Longitude Altitude Temperature Precipitation TOC soils Sample PeCB (m a.s.l.)a (
C)b (mm year1)c (mg g1)

Chungara

18
15#S 69
11#W

4500

2.1

330

Cotacotani

18
11#S 69
14#W

4400

1.5

380

Surire

18
49#S 69
40#W

4300

1.4

340

Las Cuevas 1 Las Cuevas 2 Las Cuevas 3 Piedra del Aguila Antuco 2 Villarica Nahuelbuta Laja

18
20#S 18
22#S 18
25#S 37
47#S 37
23#S 39
17#S 37
50#S 37
19#S

69
20#W 69
37#W 69
40#W 73
20#W 71
29#W 72
13#W 72
59’W 71
37’W

4300 3700 3200 1330 1200 1125 770 700

1.2 1.6 3.8 5.2 6.1 5.8 8.6 9.1

240 nag na na 1300 2200 1400 1000

Angol Huelpil Castor

37
48#S 72
44#W 37
15#S 71
57#W 45
36#S 71
46#W

500 345 725

10.2 11.1 4.2

1100 1400 270

Verde Venus

45
34#S 72
40#W 45
33#S 72
30#W

720 700

4.2 4.4

1500 1200

Risopatron

44
16#S 72
32#W

10

8.9

4700

a b c d e f g

25 2.6 53 5 130 10 10 10 9 29 10 80 50 70 6 40 40 140 150 80 98 140 47 170

SDd SOe SD SO SD SO SO SO SO SO SO SO SO SD SO SO SO SD SO SO SD SO SD SO

HCH

!0.1 0.068 0.64 0.007 !0.1 0.27 0.091 0.25 0.015 0.003 0.37 0.034 0.17 0.030 0.19 0.044 0.24 0.005 0.34 0.027 0.48 0.009 0.26 0.10 0.15 0.062 0.010 0.011 0.024 0.004 1.4 0.050 0.53 0.053 0.031 0.041 1.4 0.25 2.0 0.056 0.031 !0.01 0.96 0.081 0.015 !0.01 0.25 0.39

HCB PCB 4,4#-DDE 0.055 ef 0.023 0.052 0.011 0.051 0.097 0.049 0.028 0.074 0.056 0.040 0.11 0.046 0.012 0.070 0.072 0.022 0.13 0.11 0.20 0.18 0.017 0.13

2.2 0.30 2.3 1.5 1.1 1.5 2.5 1.2 0.45 1.3 2.0 2.6 3.2 0.89 1.1 1.1 1.9 0.24 1.4 1.4 0.84 1.6 0.53 3.2

0.55 0.10 0.065 0.30 0.28 0.41 0.78 0.24 0.24 0.54 0.62 0.63 1.1 0.019 0.29 0.39 0.56 0.019 0.40 0.21 3.3 0.37 0.097 0.69

Meters above sea level. Annual average temperature. Annual average data obtained from the Chilean Department of Public Works. Sediments. Soils. Concentration below limit of detection. Not available.

range of the instrument. Quantification was performed by reference to TCN and OCN in order to correct for instrumental instabilities. The values were also corrected by recovery of PCB-30 and PCB-209. 2.6. Quality assurance Procedural blanks were performed with each set of eight samples. Briefly, detection and quantification limits were in the order of 10 pg g1. The method for sediments was validated by replicate (nZ4) analysis of reference sample BCR 536. The results obtained were in agreement with the certified values. Reproducibility was lower than 10% for all compounds and 13% for 4,4#-DDE. Quantification and detection limits were calculated from real samples as 10 times the signal/ noise ratio and were in the order of 10e40 pg. 2.7. Total organic carbon Determination of TOC was performed on acidified samples for the removal of carbonates. Instrumental measurements were performed by flash combustion at

1025
C and thermic conductivity detection with a CHNS Elemental Analyser EA1108 (ThermoQuest). Limit of detection was 0.1%. 2.8. Statistical analysis Analysis for the effects of mean annual temperatures at each sampling site and TOC on the concentrations of OC compounds were performed using analysis of covariance (Statistica software, version 6, StatSoft, Inc., Tulsa, OK, USA). To normalize data and stabilize variances, TOC and OC concentrations were logarithmically transformed. This statistical method tests the effect of the categorical variable latitude, after adjusting the effects of the influential continuous variables temperature and TOC, taken as covariates. A significant interaction factor means that the relationship between log-transformed OC concentrations and the covariate differ among sampling sites. In this case, log-OC concentrations are normalized to the significant covariate to test the difference between sampling sites. The latitude of the sampling sites grouped the dataset in three categories: north (18
11#Se18
49#S), center

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

(37
15#Se39
17#S) and south (44
16#Se45
36#S). Correlations among the dependent variables and between the air temperature and OC concentrations were performed using the Spearman’s correlation test. 3. Results and discussion 3.1. Meteorological information Trade winds prevail at 18
S whereas westerlies dominate at 37
S and 45
S. Data on mean annual precipitation was obtained from the Chilean Department of Public Works. The lakes at 18
S exhibit much lower rates (240e380 mm year1) than at 37
S (1000e2200 mm year1) or 45
S (1200e4700 mm year1). Castor lake is a specific case of low precipitation at 45
S (270 mm year1). The calculations of the mean annual average air temperatures involved two steps. First, a ground dataset of monthly average measurements obtained from meteorological stations situated between 5 and 94 m a.s.l. were compiled for periods between 7 and 30 years. The stations included in this preliminary dataset were Arica (18
28#S, 70
20’W, 15 years of compiled data), Antofagasta (23
42#S, 70
24’W, 22 years), Valparaiso (33
1#S, 71
38’W, 30 years), Valdivia (39
48#S, 73
14’W, 29 years), Ancud (41
47#S, 73
52’W, 30 years), Puerto Aisen (42
24#S, 72
42’W, 8 years), Cabo Raper (46
50#S, 75
38’W, 8 years), Los Evangelistas (52
23#S, 75
7’W, 16 years) and Punta Arenas (53
10#S, 70
54’W, 15 years). Two stations situated at higher altitude, Santiago (33
27#S, 70
42’W, 14 years, 520 m) and Potrerillos (26
30#S, 69
27’W, 7 years, 2850 m), were also included in this group. The data provided by these meteorological stations was used for calculation of sea level annual average temperatures over a latitudinal gradient. Second, vertical temperature profiles between surface and 500 mb (approximately 5000 m a.s.l.) were obtained using Television InfraRed Observation Satellites (TIROS) and National Oceanic and Atmospheric Administration (NOAA) databases. Compilation of the available monthly averages for the standard levels of atmospheric pressure (1978e1988) allowed the calculation of monthly vertical thermal gradients which resulted in the following annual gradient estimates: 0.0046
C m1, 0.006
C m1 and 0.0062
C m1 at 18
S 70
W, 38
S 70
W and 46
S 70
W, respectively. Combination of the ground level temperature data with these vertical gradients afforded the estimation of the annual average temperature at each sampling site (Table 1). These temperature estimates agree with local descriptions of the climatic conditions in the Andean mountains. 3.2. Organochlorine compounds in soils Concentrations of OCs in soil samples varied between 0.32 and 3.2 ng g1 for total PCBs, 0.10 and 1.1 ng g1

257

for total DDTs (sum of 4,4#-DDE and 4,4#-DDT), !0.001 and 0.39 ng g1 for total HCHs (sum of a-HCH and g-HCH) and 0.007e0.18 ng g1 for HCB (Table 1). These concentrations are difficult to compare with literature data from worldwide sites because of differences in sampling and analytical techniques and the number of isomers (DDTs or HCHs) or congeners (PCBs) included in the sums of compounds. Nevertheless, having in mind these considerations, the OC concentrations in Andean soils can be taken as low (Fig. 2). The range of PCB concentrations found in our study was one order of magnitude lower than that generally reported for soils from industrial areas of Austria (6.4e 95 ng g1; Weiss et al., 1994) and Poland (4.6e3400 ng g1; Falandysz et al., 2001), rural sites of UK and Norway (1.2e2000 ng g1; Creaser et al., 1989; Alcock et al., 1993; Sanders et al., 1995; Lead et al., 1997), Germany (8.4e59 ng g1; Wilcke and Zech, 1998), Brasil (27e49 ng g1; Wilcke et al., 1999) and Thailand (1.1e6.2 ng g1; Thao et al., 1993) or woodland regions of Norway (5.3e30 ng g1; Calamari et al., 1991) and USA (7.5e250 ng g1; Smith et al., 1993). PCB concentrations similar but still higher to those found in these Andean sites have been reported in woodland regions of Germany (0.2e4.8 ng g1; Krauss et al., 2000) and Austria (0.2e7.5 ng g1; Weiss et al., 1998). Concentrations of DDTs (sum of 4,4#-DDT and 4,4#DDE) have been previously reported for soils collected in the lake catchment area of two coastal Chilean lakes (0.1e1.4 ng g1; Barra et al., 2001) and they were similar to DDT concentrations found in our soil samples (Table 1). These ranges are lower than the concentrations reported in industrial/urban areas from Germany (500e 400,000 ng g1; Wilken et al., 1994) and Poland (8.6e 2400 ng g1; Falandysz et al., 2001) or woodland regions of USA (2.1e270 ng g1; Smith et al., 1993) and Austria (up to 22 ng g1; Weiss et al., 1998). Total HCH, a-HCHCg-HCH, from these Andean soils are also lower than those reported elsewhere, e.g. concentrations reported in urban/industrial areas of Poland range between 0.36 and 110 ng g1 (Falandysz et al., 2001) and in woodland regions of Austria between 0.6 and 6.6 ng g1 (Weiss et al., 1998). Andean soil HCB concentrations are also lower than soil values reported in urban/industrial areas of Germany (100e1300 ng g1; Wilken et al., 1994) and Poland (0.19e30 ng g1; Falandysz et al., 2001) and lower than in woodland regions of Austria (up to 1.9 ng g1; Wilken et al., 1994). The low values of the Andean soils reflect the absence of local pollution sources near the sampling sites and are consistent with the lower use of organochlorine compounds in the southern hemisphere. These Andean soil concentrations are also much lower than those reported for total PCBs and DDTs in mountain soils located

258

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

Fig. 2. Range of organochlorine concentrations in Andean soils compared with those from industrial, urban and remote areas of the northern hemisphere. References: (1) Ribes et al., 2002; (2) Grimalt et al., 2004; (3) Holoubek et al., 1994, 1998; (4) Wilken et al., 1994; (5) Falandysz et al., 2001; (6) Smith et al., 1993; (7) Covaci et al., 2001; (8) Bidleman and Leone, 2004; (9) Kim and Smith, 2001; (10) Weiss et al., 1998; (11) Krauss et al., 2000; (12) Weiss et al., 1998; (13) Wilcke and Zech, 1998; (14) Weiss et al., 1994; (15) Backe et al., 2004.

near to industrial sites such as the Giant Mountains (CzechePolish border) where concentration ranges of 5e140 ng/g and 20e5100 ng/g, respectively, have been found (Holoubek et al., 1994, 1998). The concentrations of HCB in the soils of these high mountain lakes and the Giant Mountains, 0.47e48 ng/g are more similar (Holoubek et al., 1994, 1998) but still lower in the Andes. Comparison with previously reported values in remote subtropical (Teide) or temperate (Pyrenees and Tatra) mountains shows similar concentrations values in the case of total PCBs, 0.04e9.2 ng g1 (Ribes et al., 2002; Grimalt et al., 2004), but still lower in the Andean mountains. DDTs, HCHs and HCB in Teide, 0.01e

40 ng g1, 0.001e1 ng g1 and 0.01e3.2 ng g1, respectively (Ribes et al., 2002; Grimalt et al., 2004), exhibit higher concentrations than in the Andes (Fig. 2). 3.3. Organochlorine compounds in sediments Sediment samples were taken in Chungara, Cotacotani, Surire, Laja, Castor, Venus and Risopatron (Fig. 1, Table 1). Total PCB concentrations in the sediments from the Andean lakes range between 0.24 and 2.3 ng g1 (Table 1). These concentrations are much lower than the levels reported in Lake Superior (7.8e18 ng g1 (Jeremianson et al., 1994), Wisconsin (2.6e89 ng g1;

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

Swackhamer and Armstrong, 1986), Ontario (180e850 ng g1; Eisenreich et al., 1989) or Canadian (2.4e39 ng g1; Muir et al., 1995) and Finnish Lakes (2.9e5.6 ng g1; Vartianen et al., 1997) (Fig. 3). They are in the range of those reported in Lake Baikal (0.08e6.1 ng g1; Iwata et al., 1995) or Siskiwit (Swackhamer et al., 1988). Total HCHs range between !0.005 and 0.23 ng g1 which is again significantly lower than the concentrations found in the Canadian lakes (0.03e4.3 ng g1; Muir et al., 1995) and similar to those reported in Lake Baikal (0.02e 0.11 ng g1; Iwata et al., 1995). Total DDTs range between 0.019 and 4.1 ng g1 (Table 1) exhibiting similar values to those reported in Canadian lakes (0.05e7 ng g1; Muir et al., 1995) and Lake Baikal (0.007e2.1 ng g1; Iwata et al., 1995) and much lower

259

than those in polluted sites such as Lake Ontario (180e 850 ng g1; Muir et al., 1995). HCB range between 0.011 and 0.20 ng g1 which is again similar to the concentrations found in the Canadian lakes (0.09e1.8 ng g1; Muir et al., 1995) and Lake Baikal (0.005e0.16 ng g1; Iwata et al., 1995) and lower than those found in Lake Ontario (10e200 ng g1; Eisenreich et al., 1989). Direct comparison between the OC concentrations in the soils and lake sediments is difficult because OC accumulation is influenced by sediment focusing factor, accumulation fluxes and other aspects. As a general trend, OC concentrations in soils and sediments are of the same order of magnitude but the highest OC concentrations are found in the soils (Table 1). However, HCB and 4,4#-DDE (Lake Venus, Table 1) constitute an

Fig. 3. Range of organochlorine concentrations in surface sediments from the Andean mountain lakes compared with those from remote lakes of the northern hemisphere. References: (1) Iwata et al., 1995; (2) Jeremianson et al., 1994; (3) Swackhamer and Armstrong, 1986; (4) Eisenreich et al., 1989; (5) Muir et al., 1995; (6) Vartianen et al., 1997; (7) Rawn et al., 2001; (8) cited in Rawn et al., 2001; (9) Berglund et al., 2001; (10) Grimalt et al., 2004; (11) Cleemann et al., 2000.

260

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

exception being in higher concentrations in the lake sediments. Lake to lake comparison also shows higher OC concentrations in soils than sediments in all lakes except Chungara where all compounds but PeCB exhibit higher sediment values. 3.4. Dependence of OC concentrations from total organic carbon TOC in soils range between 2.6 and 170 mg g1 (Table 1), these values are similar to those encountered in other mountain areas such as Teide (0e3400 m, Tenerife, Canary Islands, 28
N 16
W), the Pyrenees (2240 m) or the Tatras (1783e2057 m) (Grimalt et al., 2004). They span over a smaller interval than those in the Teide gradient (0.5e320 mg g1; Ribes et al., 2002). TOC in sediments range between 25 and 140 mg g1 (Table 1), exhibiting similar ranges as previously described in European high mountain lakes (23e230 mg g1; Grimalt et al., 2001, 2004). Correlation of the soil OC concentrations at each site with soil organic matter (Table 1) shows significant r2 coefficients in most cases (Table 2). Both OC and TOC concentrations were log transformed before correlation in order to have normal distributed variables according to the KolmogoroveSmirnov test. Soil organic matter is generally considered as a preferential site for the sorption of hydrophobic pollutants (Marschner, 1999; Pignatello, 1998). The good correlation between log(OC) and log(TOC) is in agreement with recent studies encompassing the global distribution of PCBs and HCB in background surface soils (Meijer et al., 2003) and suggests that the geographical distribution pattern of these compounds is approaching steady state, in equilibrium with soil properties, and absence of punctual pollution episodes. Furthermore, significant relationships (r2O0.60, p!0.05) were observed among the TOC-normalized OC concentrations in the soil samples, except for a-HCH. These highly significant correlations among the OCs could suggest a global atmospheric transport for these chemicals in Chile reaching maximum OC concentrations in the high mountain areas (O3,000 m a.s.l.) of the northern Chile (Fig. 4). In contrast, the sediment OC concentrations are not correlated to TOC, only in the case of PCB congener #101/ 90 a linear regression coefficient with p!0.1 (but pO0.05) is observed. All other OC exhibit r2 values with pO0.1. 3.5. Temperature dependence The sampling sites considered in this study are distributed over large altitudinal and latitudinal gradients. In the absence of significant local pollution sources, temperature dependence is the primary factor to be evaluated for OC accumulation.

The temperature influence can be examined using the Boltzmann equation in the following form: CX =CA ZA,expðB=TÞ

ð1Þ

where CX and CA refer to the solid sample and air concentrations, respectively, T is temperature in degrees Kelvin and A and B are constants (Thao et al., 1993; Wilcke et al., 1999). In the context of the present study, CX may stand for concentrations in soils or sediments. According to this equation, representation of the log-transformed ratios between OC concentrations in soils and sediments and air OC concentrations and the reciprocal of the mean annual air temperatures in degrees K should give rise to a linear expression. The soil concentrations were normalized to TOC due to the significant relationship between OC and TOC reported in the previous section. The absence of atmospheric concentration data renders the application of Eq. (1) more difficult. Previously reported atmospheric OC concentrations in remote high altitude sites have revealed rather constant values independently of air origin or location (van Drooge et al., 2002). Thus, Eq. (1) can be simplified by only considering OC concentrations in soils (normalized to TOC) or sediments and reciprocal of temperature. However, studies involving sites at different elevation showed that air OC concentrations at high altitude in the free troposphere were lower than near sea level by a factor of two (Knap and Binkley, 1991; Hoff et al., 1998; van Drooge et al., 2002). Despite these previous results, in the absence of direct atmospheric measurements in the Andean region, corrections due to possible altitude differences of air OC concentrations have been avoided. This approach constitutes the most conservative methodology and minimizes temperature influence. However, it provides the most solid results upon observation of temperature dependence. The whole soil dataset (nZ17) encompasses annual average temperatures between 2.1
C and 11
C (DTZ 13.2
C). Calculation of the correlation coefficients for Eq. (1) shows a significant dependence ( p!0.05) from annual average temperature for most compounds (Table 2). In sediments, significant correlations are observed for the more hydrophobic PCB congeners, e.g. #138 ( p!0.1), #158/160 ( p!0.01) and #180 ( p!0.01) (Table 2). In this case, the smaller dataset (nZ7) renders more difficult the identification of the linear correlations with lowest statistical significance. In addition, the process of incorporation from atmosphere to sediments involves the partitioning through the water column which adds another factor of variability between samples. Aire sediment interactions are more complex than the aire soil interactions described in Eq. (1) because in the former case there is an additional process of water solubilization. In principle, only the most hydrophobic

Table 2 Concentration ranges and regression coefficients for the correlation of the soil concentrations of the TOC normalized organochlorine compounds (in log scale) vs reciprocal of absolute annual average temperature at the sampling site Compound

Soilsa

Sedimentsb


DTZ13.2 C (2.1, 11); nZ17

PeCB a-HCH HCB g-HCH PCB-18 PCB-28/31 PCB-52 PCB-70 PCB-101/90 PCB-110 PCB-123/149 PCB-118 PCB-105/132 PCB-138 PCB-158/160 PCB-180 4,4#-DDE 4,4#-DDT







TOC

18 S

37 S

45 S

All

DTZ10.6 (1.5, 9.1); nZ7

DTZ5.9 (2.1, 3.8); nZ6

DTZ5.8 (5.2, 11); nZ7

DTZ4.7 (4.2, 8.9); nZ4

DTZ11.2 (2.1, 9.1); nZ7

Cmin, Cmax

r2

Slope

DHc

Cmin, Cmax

r2

Cmin, Cmax

r2

Cmin, Cmax

r2

Cmin, Cmax

r2

Cmin, Cmax

r2

1.5, 250 !0.1, 43 0.53, 17 !0.1, 8.0 0.26, 22 0.24, 57 0.59, 40 0.55, 31 0.70, 90 0.38, 32 1.3, 47 0.25, 18 0.35, 12 1.4, 69 0.05, 2.0 0.47, 5.9 2.7, 140 0.31, 12

0.37* 0.17 0.44** 0.49** 0.32* 0.22 0.26* 0.28* 0.23 0.19 0.31* 0.21 0.23 0.28* 0.28* 0.40** 0.22 ed

13000 11000 11000 15000 13000 11000 12000 11000 12000 10000 12000 10000 10000 10000 11000 9200 10000 e

110 93 93 130 100 93 96 94 97 85 99 87 85 85 92 77 84 e

3.9, 52 0.05, 43 0.87, 17 0.11, 7.7 1.4, 22 3.6, 57 3.0, 40 1.8, 31 5.2, 91 1.7, 31 3.6, 47 0.82, 18 0.90, 12 4.7, 69 0.064, 2.0 0.92, 5.9 10, 140 0.87, 11

e 0.64* 0.75* 0.69* 0.62* 0.68* e e e e e e e 0.60* 0.95** 0.79** e 0.94**

14, 250 !0.1, 43 2.9, 17 !0.1, 7.7 1.45, 22 3.9, 57 3.9, 40 3.7, 31 6.0, 51 3.0, 24 12, 47 3.1, 11 3.1, 12 5.0, 69 0.51, 2.0 1.8, 5.9 17, 140 2.4, 11

e e e 0.91** 0.60 e e 0.68* e 0.82* e 0.81* 0.65 e e 0.66* e 0.87**

3.2, 34 0.05, 1.4 0.53, 2.5 0.11, 0.72 0.86, 4.5 1.9, 10 1.3, 17 1.0, 18 2.9, 27 1.5, 31 2.0, 30 0.82, 18 0.57, 10 4.7, 12 0.06, 1.9 0.71, 1.6 8.2, 46 0.87, 3.7

e e e e e e e e e e e e e e e e e e

1.5, 27 0.25, 2.1 0.75, 1.5 0.26, 1.3 0.26, 0.7 0.24, 1.9 0.59, 1.3 0.55, 6.4 0.7, 3.0 0.38, 0.99 1.3, 1.9 0.25, 1.15 0.35, 0.59 1.4, 4.1 0.05, 0.22 0.47, 0.63 2.6, 4.0 0.31, 0.77

e e e e e e e e e e e e e e e e e e

!0.001, 0.16 !0.001, !0.001 0.011, 0.20 !0.001, 0.27 !0.001, 0.31 !0.001, 0.063 !0.001, 0.15 0.015, 0.20 !0.001, 1.2 0.008, 0.16 0.034, 0.16 0.029, 0.14 0.001, 0.21 !0.001, 1.1 !0.001, 0.026 !0.001, 0.036 0.019, 3.3 !0.001, 0.78

e e e e e e 0.27 e 0.35 e 0.28 0.34 e 0.45 0.98** 0.66* e e

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

All




The coefficients have been calculated over the whole dataset and over sample subgroups of the same TOC (5 and 10 mg g1) or latitude (18
S, 37
S, 45
S). *p!0.05. **p!0.01. a Calculated over TOC normalized concentrations (ng g1 TOC). b Calculated over dry weight concentrations (ng g1). c Enthalpies in kJ mol1. d Values without statistical significance ( p>0.1).

261

262

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

Northern Chile Central Chile

γ-HCH

101

Southern Chile 100 r2 = 0.71

10-1

4,4’-DDE

103

r2 = 0.61

102 101 r2 = 0.86

100

4,4’-DDT

102

r2 = 0.76

101 100 r2 = 0.75

10-1

ΣPCBs

103

r2 = 0.83

r2 = 0.60

102 101 100 -1 10

r2 = 0.86 100

101

HCB

102

r2 = 0.97 0.1

1

γ-HCH

10

100

101

102

4,4'-DDE

r2 = 0.83 103

10-1

100

101

102

4,4-DDT

Fig. 4. Scatterplot matrix of significant ( p!0.05) correlations between organochlorine concentrations in the Andean soils.

compounds, those remaining in the particulate phase in the water column, are susceptible of incorporation into the underlying sediments. Accordingly, in the dataset of the present study only the more hydrophobic compounds are therefore observed to exhibit temperature dependence (Table 2). In the case of the more volatile compounds, the exchange between atmosphere and sediment is probably hindered by water column processes. The observed correlations involve concentration changes between lowest and highest temperatures of about one order of magnitude (Fig. 5). Previous studies in a subtropical high mountain (Teide, Canary Islands; Ribes et al., 2002) showed a temperature dependence on soil OC accumulation, between 1.5 and 2 orders of magnitude. In this latter case, the temperature interval was 15
C and the atmospheric concentrations above the inversion layer were half than those below this limit. Thus, the concentration values assigned to the term CA in Eq. (1) involved an increase of two times the CX/CA ratio when comparing below and above this boundary. As indicated

above, this CA term has been considered constant in the present study. Despite this assumption the temperature dependence of soil and sediment OC concentrations in the Andean mountains is significant (Table 2) involving that higher levels are found at higher altitudes, at the sites located further away from human influence. The higher OC amounts in these samples cannot be attributed to higher precipitation rates since these are lowest in the group of samples of highest OC concentrations. On the other hand, the temperature dependence is observed irrespectively of OC source. That is, industrial products, e.g. PCBs and PeCB, pesticides, e.g. DDTs and HCHs, and compounds of mixed origin, e.g. HCB. Further insight into the significance of the soil results can be obtained by selection of a soil subset of uniform TOC, e.g. between 5 and 10 mg g1 (nZ7). The resulting correlation coefficients also illustrate clear temperature dependence. Thus, the coefficients exhibit even higher r2 values in comparison to the calculation including the whole dataset (Table 2) and they are significant ( p!0.05 or 0.01). However, the lower number of samples involves

263

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

10.0

PeCB

10.0

R2 = 0.6156

10.0

0.1 0.0035

0.0036

0.0037

0.1 0.0035

TEMPERATURE (1/°K)

PCB-18

0.0036

0.0037

0.1

0.0035

TEMPERATURE (1/°K)

10

R2 = 0.5514

HCB R2 = 0.561

1.0

1.0

1.0

10

a-HCH R2 = 0.4949

PCB-52

10.0

R2 = 0.5584

0.0036

0.0037

TEMPERATURE (1/°K)

PCB-105 R2 = 0.4258

1.0

1 0.0035

0.0036

0.0037

TEMPERATURE (1/°K)

1 0.0035

0.0036

0.0037

TEMPERATURE (1/°K)

0.1 0.0035

0.0036

0.0037

TEMPERATURE (1/°K)

Fig. 5. Correlation plots for the TOC normalized concentrations of organochlorine compounds vs reciprocal of temperature (K).

less statistical power for detection of small trends within OC soil variability. Thus, the statistically significant correlations are observed for a lower number of compounds. 3.6. Altitudinal dependence Representation of the database in groups of the same latitude allows the evaluation of the significance of altitude in the observed temperature dependence. Accordingly, the soil samples have been grouped in three subsets, 18
S, 37
S and 45
S, and the linear dependencies between log-transformed concentrations and reciprocal of temperature have been examined in each of them independently. The correlation coefficients of the soil samples collected at 18
S (lakes Chungara, Cotacotani, Surire and Las Cuevas 1, 2 and 3) are again significant ( p!0.05 or 0.01) (Table 2). However, the smaller number of samples requires much higher correlation coefficients for statistical significance which in practice renders more difficult the observation of the linear correlations for all compounds. Re-elaboration of Eq. (1) for the calculation of the expected concentration differences at various temperature intervals show that an important parameter determining the concentration increases is the minimal temperature represented by the dataset: DCZA,ðexpB=Tmin CDTÞ  ðexpðB=Tmin ÞÞ

ð2Þ

where DT and Tmin are the temperature intervals and the minimum temperature value represented by the dataset, respectively and DC is the expected concentration difference. This expression predicts different concentration gradients for the same temperature interval at different temperature values. An increase of 5.9
C between 2.1
C and 9.1
C (samples at latitude 18
S) involves a concentration decrease of about 2.2 ng g1. In contrast, the temperature increases of 5.8
C (5.2
C and 11
C) and 4.6
C (4.4
C and 8.9
C) for the soil samples at 37
S and 45
S, respectively, involve concentration differences of 0.74 ng g1 in both cases (Fig. 6). Obviously, smaller concentration differences are a priori more difficult to detect within sample variability. No statistically significant differences are therefore observed at 37
S and 45
S. The above reported concentration intervals have been calculated using the same A and B constants, such as the currently observed values of 9!1018 and 11,000, respectively (Table 2). Use of other constant values will give other concentration increments but the relative differences will remain the same. The higher concentrations of these OC at higher altitude is consistent with the results of previous studies on mountain sites from other areas (Blais et al., 1998; Grimalt et al., 2001; Ribes et al., 2002). However, these studies show the accumulation of different OC groups. The data on the European mountain lakes (Grimalt et al., 2001) and Teide mountain (Ribes et al., 2002) are those more directly comparable with the present set of

DIFFERENCE OF CONCENTRATIONS (ng·g -1)

264

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

3.7. Enthalpies

-6

-5

∆T=

The correlations between soil concentrations and the reciprocal of temperature afford the calculation of airesoil exchange pseudo-enthalpies:

14 12

-4

10

DHZS,R,lnð10Þ

8 6

-3

5 4

-2 18°S -1 45°S 0

-5

-4

-3

-2

-1

0

1

2

3

4

37°S 5

6

TEMPERATURE AT HIGHEST ELEVATION (°C) Fig. 6. Expected concentration differences for minimal temperatures and temperature intervals as predicted from theoretical solid surfaceair adsorption (Eq. (3)). The plot predicts different concentration ranges for the same temperature intervals at different temperature minima. All plots were calculated for AZ9!1018 and BZ11000 K1. Use of other constants will change the absolute values but not the relative differences.

Andean lakes at 18
S since they encompass similar air average annual air temperatures, 1.45e8.7
C, 4.9e 20
C and 2.1e3.8
C, respectively. The Teide and the Andean mountain data exhibit a close agreement since the concentrations of nearly all OC increase with altitude. Only the compounds of present or recent use in agricultural applications (HCHs and DDTs, respectively) did not show altitude dependence in Teide. In contrast, the results from the European lakes only show altitudinal dependence for the OC compounds with volatilities lower than 102.5 Pa. The difference between Andean and European lakes cannot be attributed to the temperatures represented by the samples included in both studies. However, the European lake study only includes samples obtained within the lakes (fish and sediments) whereas the Andean series essentially encompass samples in direct contact with air (soils). In this respect, the above reported series of Andean lake sediments only showed temperature dependence for OC with volatilities lower than 102.5 Pa (Table 2). That is, like in the European lakes. On the other hand, studies on snow OC concentrations in a series of European high mountain lakes show significant correlation with altitude for compounds with volatilities higher than 102.5 Pa (Carrera et al., 2001). The closer parallelism between European snow and soil Andean samples is probably due to direct air exchange in these two types of samples.

ð3Þ

where S is the slope of the regression line and R the gas constant at 8.314 J K1 mol1. Most enthalpy soil values range between 80 and 100 kJ mol1 (Table 2). These field constants are close to the enthalpies of phase change between octanol and air calculated in laboratory experiments, 66e93 kJ mol1 (Harner and Bidleman, 1996). However, comparison of both types of values must be done with caution. The field series correspond to different sites from which a constant annual average air temperature is assumed whereas the octanoleair values were obtained from laboratory systems in which temperatures are fixed by experimental design. Furthermore, deviations from linearity of some field data may also have significant influence on the overall slope values. Last but not least, possible introduction of corrections for different air concentrations at different altitudes (see discussion above) would also influence the final enthalpy values. The comparison between both datasets is therefore only done on a tentative basis. Having in mind these constraints, the higher airesoil enthalpies than theoretical octanoleair values probably evidence sorption effects other than simple linear adsorption, increasing the retention of these compounds in soil organic matter (Hoff et al., 1998). The higher enthalpies observed from the field data indicate that the intensity of these effects is also related to ambient temperature being more relevant at low values.

4. Conclusions The OC concentrations in the soils and sediments from the high mountain Andean lakes considered in the present study range among the lowest values ever reported in remote sites. The log-transformed concentrations of most OC in soils exhibit significant correlations with total organic content (TOC) which is consistent with the general correlation between soil OC and TOC from soils of remote areas (Meijer et al., 2003). Log transformed OC concentrations in soils (TOC normalized) cannot be related to differences in atmospheric precipitation; they show a significant linear dependence from reciprocal of temperature independently of the origin of the compounds, e.g. industrial, agricultural or mixed. The sediment OC concentrations exhibit an exponential dependence with reciprocal of

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

temperature mostly for the less volatile PCBs. This agreement gives grounds to temperature as a significant factor for the retention of long range transported OC in remote ecosystems such as the Andean mountains. Thus, the samples in direct contact with the atmosphere (soils) show high temperature dependencies of the more volatile compounds and those collected under lake water (sediments) emphasize the temperature dependencies of the less volatile OC. The phase transfer enthalpies calculated from the soil values exhibit similar but slightly higher values than those determined in laboratory experiments. The difference points to retention mechanisms other than linear adsorption for the accumulation of OC in these high mountain areas. In the context of the samples selected for study, the observed temperature dependencies are related to altitude. Thus, the samples situated at higher elevation show higher concentrations. Besides temperature intervals, the ultimate accumulation factor determining the altitudinal OC concentration differences concerns the lowest annual average air temperature in the sample set under study. That is, the one currently corresponding to the point situated at highest elevation. Acknowledgements This work was supported by FONDECYT No. 1010640 and the EU funded project GLOBAL-SOC (ENV4-CT97-0503). We thank CONAF-Chile (Corporacio´n Nacional Forestal) for permission to take samples in natural parks and reserves.

References Alcock, R.E., Johnston, A.E., McGrath, S.P., Berrow, M.L., Jones, K.C., 1993. Long-term changes in the polychlorinated biphenyl (PCB) content of United Kingdom soils. Environmental Science and Technology 27, 1918e1923. Backe, C., Cousins, I.T., Larsson, P., 2004. PCB in soils and estimated soil-air exchange fluxes of selected PCB congeners in the south of Sweden. Environmental Pollution 128, 59e72. Barra, R., Cisternas, M., Urrutia, R., Pozo, K., Pacheco, P., Parra, O., Focardi, S., 2001. First report on chlorinated pesticide deposition in a sediment core from a small lake in central Chile. Chemosphere 45, 749e757. Berglund, O., Larsson, P., Ewald, G., Okla, L., 2001. Influence of trophic status on PCB distribution in lake sediments and biota. Environmental Pollution 113, 199e210. Bidleman, T.F., Leone, A.D., 2004. Soil-air exchange of organochlorine pesticides in the Southern United States. Environmental Pollution 128, 49e57. Blais, J.M., Schindler, D.W., Muir, D.C.G., Kimpe, L.E., Donald, D.B., Rosenberg, B., 1998. Accumulation of persistent organochlorine compounds in mountains of western Canada. Nature 395, 585e588. Calamari, D., Bacci, E., Focardi, S., Gaggi, C., Morosini, M., Vighi, M., 1991. Role of plant biomass in the global environmental

265

partitioning of chlorinated hydrocarbons. Environmental Science and Technology 25, 1489. Carrera, G., Ferna´ndez, P., Vilanova, R.M., Grimalt, J.O., 2001. Persistent organic pollutants in snow from European high mountain areas. Atmospheric Environment 35, 245e254. Cleemann, M., Riget, F., Paulsen, G.B., Boer, J., Klungsøyr, J., Aastrup, P., 2000. Organochlorines in Greenland lake sediments and landlocked Arctic char (Salvelinus alpinus). The Science of the Total Environment 245, 173e185. Covaci, A., Hura, C., Schepens, P., 2001. Selected persistent organochlorine pollutants in Romina. The Science of the Total Environment 280, 143e152. Creaser, C.S., Fernandes, A.R., Harrad, S.J., Hurst, T., Cox, E.A., 1989. Background levels of polychlorinated biphenyls in British soils. II. Chemosphere 19, 1457e1466. Eisenreich, S.J., Capel, P.D., Robbins, J.A., Bourbonniere, R., 1989. Accumulation and diagenesis of chlorinated hydrocarbons in lacustrine sediments. Environmental Science and Technology 23, 1116e1126. Falandysz, J., Brudnowska, B., Kawano, M., Wakimoto, T., 2001. Polychlorinated biphenyls and organochlorine pesticides in soils from the southern part of Poland. Environmental Contamination and Toxicology 40, 173e178. Grimalt, J.O., van Drooge, B.L., Ribes, A., Vilanova, R.M., Fernandez, P., Appleby, P., 2004. Persistent organochlorine compounds in soils and sediments of European high altitude mountain lakes. Chemosphere 54, 1549e1561. Grimalt, J.O., Fernandez, P., Berdie´, L., Vilanova, R.M., Catalan, J., Psenner, R., Hofer, R., Appleby, P.G., Rosseland, B.O., Lien, L., Massabuau, L.C., Battarbee, R.W., 2001. Selective trapping of organochlorine compounds in mountain lakes of temperate areas. Environmental Science and Technology 35, 2690e2697. Harner, T., Bidleman, T.F., 1996. Measurements of octanol-air partition coefficients for polychlorinated biphenyls. Journal of Chemical and Engineering Data 41, 895e899. Harner, T., Mackay, D., 1995. Measurement of octanol-air partition coefficients for chlorobenzenes. Environmental Science and Technology 29, 1599e1606. Hoff, R.M., Brice, K.A., Halsall, C.J., 1998. Nonlinearity in the slopes of Clausius-Clapeyron plots for SVOCs. Environmental Science and Technology 32, 1793e1798. Holoubek, I., Caslavsky, J., Vancura, R., Kocan, A., Chovancova, J., Petrik, J., Drobna, B., Cudlin, P., Triska, J., 1994. Project Tocoen: the fate of selected organic pollutants in the environment. Part XXIV. The content of PCBs and PCDDs/Fs in high-mountain soils. Toxicological and Environmental Chemistry 45, 189e197. Holoubek, I., Triska, J., Cudlin, P., Caslavsky, J., Karl-Werner, S., Kettrup, A., Kohoutek, J., Cupr, P., Schneiderova, E., 1998. Project Tocoen (Toxic organic compounds in the environment). Part XXXI. The occurrence of POPs in high mountain ecosystems of the Czech Republic. Toxicological and Environmental Chemistry 66, 17e25. Iwata, H., Tanabe, S., Ueda, K., Tatsukawa, R., 1995. Persistent organochlorine residues in air, water, sediments, and soils from the Lake Baikal region, Russia. Environmental Science and Technology 29, 792e801. Jeremianson, J.D., Hornbuckle, K.C., Eisenreich, S.J., 1994. PCBs in Lake Superior, 1978e1992: decreases in water concentrations reflect loss by volatilization. Environmental Science and Technology 28, 903e914. Kim, J.H., Smith, A., 2001. Distribution of organochlorine pesticides in soils from South Korea. Chemosphere 43, 137e140. Knap, A.H., Binkley, K.S., 1991. Chlorinated organic compounds in the troposphere over the Western North Atlantic Ocean measured by aircraft. Atmospheric Environment 25A, 1507e1516. Krauss, M., Wilcke, W., Zech, W., 2000. Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in forest soils: depth

266

F. Borghini et al. / Environmental Pollution 136 (2005) 253e266

distribution as indicator of different date. Environmental Pollution 110, 79e88. Larsson, P., Ja¨rnmark, C., So¨dergren, A., 1992. PCBs and chlorinated pesticides in the atmosphere and aquatic organisms of Ross Island, Antarctica. Marine Pollution Bulletin 25, 281e287. Lead, W.A., Steinnes, E., Bacon, J.R., Jones, K.C., 1997. Polychlorinated biphenyls in UK and Norwegian soils: spatial and temporal trends. The Science of the Total Environment 196, 229e236. Lohmann, R., Ockenden, W.A., Shears, J., Jones, K.C., 2001. Atmospheric distribution of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs), and non-ortho biphenyls (PCBs) along a North-South Atlantic transect. Environmental Science and Technology 35, 4046e4053. Marschner, B., 1999. Sorption von polyzyklischen aromatischen kohlenwasserstoffen (PAK) und polychlorierten biphenylen (PCB) im boden. Journal of Plant Nutrition and Soil Science 162, 1e14. Meijer, S.N., Ockenden, W.A., Seetman, A., Breivik, K., Grimalt, J.O., Jones, K.C., 2003. Global distribution and budget of PCBs and HCB in background surface soils: implications for sources and environmental processes. Environmental Science and Technology 37, 667e672. Muir, D.C.G., Ford, C.A., Grift, N.P., Metner, D.A., Lockhart, W.L., 1990. Geographical variation of chlorinated hydrocarbons in burbot (Lola lota) from remote lakes and rivers in Canada. Archives of Environmental Contamination and Toxicology 19, 530e542. Muir, D.C.G., Grift, N.P., Lockhart, W.L., Wilkinson, P., Billeck, B.N., Brunskill, G.J., 1995. Spatial trends and historical profiles of organochlorine pesticides in Arctic lake sediments. The Science of the Total Environment 160/161, 447e457. Pignatello, J.J., 1998. Soil organic matter as a nanoporous sorbent of organic pollutants. Advances in Colloid Interface Science 76-77, 445e467. Rawn, D.F., Lockhart, W.L., Wilkinson, P., Savoie, D.A., Rosenberg, G.B., Muir, D.C., 2001. Historical contamination of Yukon Lake sediments by PCBs and organochlorine pesticides: influence of local sources and watershed characteristics. The Science of the Total Environment 280, 17e37. Ribes, A., Grimalt, J.O., Torres Garcia, C.J., Cuevas, E., 2002. Temperature and organic matter dependence of the distribution of organochlorine compounds in mountain soils from the subtropical Atlantic (Teide, Tenerife Island). Environmental Science and Technology 36, 1879e1885. Sanders, G., Jones, K.C., Hamilton-Taylor, J., Dorr, H., 1995. PCB and PAH fluxes to dated UK peat core. Environmental Pollution 89, 17e25. Simonich, S.L., Hites, R.A., 1995. Global distribution of persistent organochlorine compounds. Science 269, 1851e1854.

Smith, W.H., Hale, R.C., Greaves, J., Hugget, R.J., 1993. Trace organochlorine contamination of the forest floor of the White Mountain National Forest, New Hampshire. Environmental Science and Technology 27, 2244e2246. Swackhamer, D.L., Armstrong, D.E., 1986. Estimation of the atmospheric and nonatmospheric contributions and losses of polychlorinated biphenyls to lake Michigan on the basis of sediment records of remote lakes. Environmental Science and Technology 20, 879e883. Swackhamer, D.L., McVeety, B.D., Hites, R.A., 1988. Deposition and evaporation of polychlorobiphenyl congeners to and from Siskiwit Lake, Isle Royale, Lake Superior. Environmental Science and Technology 22, 664e672. Thao, V.D., Kawano, M., Tatsukawa, R., 1993. Persistent organochlorine residues in soils from tropical and sub-tropical Asian countries. Environmental Pollution 81, 61e71. Van Drooge, B.L., Grimalt, J.O., Torres Garcı´ a, C.J., Cuevas, E., 2002. Semivolatile organochlorine compounds in the free troposphere of the northeastern Atlantic. Environmental Science and Technology 36, 1155e1161. Vartianen, T., Maanio, J., Korhonen, M., Kinnunen, K., Strandman, T., 1997. Levels of PCDD, PCDF and PCB in dated lake sediments in subarctic Finland. Chemosphere 34, 1341e1350. Wania, F., Mackay, D., 1995. A global distribution model for persistent organic chemicals. The Science of the Total Environment 160/161, 211e232. Wania, F., Mackay, D., 1996. Tracking the distribution of persistent organic pollutants. Environmental Science and Technology 30, 390Ae396A. Weber, K., Goerke, H., 1996. Organochlorine compounds in fish off the Antarctic Peninsula. Chemosphere 33, 377e392. Weiss, P., Riss, A., Gschmeidler, E., Schentz, H., 1994. Investigation of heavy metal, PAH, PCB patterns and PCDD/F profiles of soil samples from an industrialized urban area (Linz, upper Austria) with multivariate statistical methods. Chemosphere 29, 2223e2236. Weiss, P., Lorbeer, G., Scharf, S., 1998. Vegetation/soil partitioning of semivolatile organic compounds. Organohalogen Compounds 39, 381e384. Wilcke, W., Zech, W.Z., 1998. Polychlorinated biphenyls (PCBs) in bulk soil and particle-size separates of soils in a rural community. Zeitschrift fu¨r Pflanzenerna¨hrung und Bodenkunde 161, 289e295. Wilcke, W., Lilienfein, J., do Carmo Lima, S., Zech, W., 1999. Contamination of highly weathered urban soils in Uberlandia, Brazil. Journal of Plant Nutrition and Soil Science 162, 539e548. Wilken, M., Walkow, F., Jager, E., Zeschmar-Lahl, B., 1994. Flooding area and sediment contamination of the river Mulde (Germany) with PCDD/F and other organic pollutants. Chemosphere 29, 2237e2252.