**d. Organic compounds**

Pollution by organic compounds is also a concern emerging from studies designed to address the topic of sealed landfills, as many recently banned compounds, dumped in landfills and numerous affected ecosystems, have been detected [26]. The organic compounds determined in the soil samples and the techniques used for this purpose were: total hydrocarbons by infrared spectrometry (UNE 77307); organochlorine insecticides and polychlorinated biphen‐ yls (PCBs) by gas chromatography (ISO 10382); and polycyclic aromatic hydrocarbons (PAHs) (ISO 18287) and phenols (U.S. E.P.A 3550B, U.S. E.P.A 3650B and U.S. E.P.A 8401) by gas chromatography. The reader is referred to [1] for descriptions of these techniques and their modifications for the present purposes.

Table 9 shows the great variety of organic pollutants that may be found in the Getafe landfill. Those detected at concentrations higher than permitted levels and widely distributed at the site were total hydrocarbons, PCBs, the PAHs with a greater number of rings and some organochlorine insecticides. In general, the sites showing most pollution of this type were those also showing most heavy metal pollution.

Given that total hydrocarbons were detected at all the sites in which these were examined (N=43), Table 10 presents the differences detected.


**Table 7.** Electrical conductivity (EC, µS cm-1) and anion concentration (mg kg-1) in soil samples collected from landfill proper.

The Complex Nature of Pollution in the Capping Soils of Closed Landfills: Case Study in a Mediterranean Setting http://dx.doi.org/10.5772/57223 213

**Landfill samples EC F- Cl- NO2 - NO3 - PO4 3- SO4 2-**

G- 23 132 5.5 4.6 1.4 5.4 0.0 26 G- 24 107 1.8 8.1 1.6 52 2.1 11 G- 45 114 2.6 12 1.5 3.3 2.1 8.5 G- 46 161 7.4 8.5 1.1 5.3 2.3 31 G- 47 116 2.4 8.9 1.7 7.6 1.6 10 G- 48 113 2.6 13 1.6 3.7 3.1 8.0

G- 6 175 2.8 6.4 0.7 3.0 0.0 147 G- 8 317 19 6.0 1.4 17 0.0 398 G- 11 159 7.6 7.7 1.0 3.6 0.0 41 G- 16 1853 10 38 1.3 70 0.0 4063 G- 17 587 14 10 1.4 22 0.0 592 G- 18 985 31 121 2.6 193 0.0 635 G- 19 1329 13 32 2.0 1152 0.0 691 G- 20 154 1.6 5.2 1.3 38 2.2 15 G- 21 171 2.5 6.3 0.9 94 0.9 91 G- 22 157 1.7 4.9 1.1 15 1.1 123 G- 39 366 18 8.6 3.0 41 0.0 214

G- 3 A 270 3.2 33 1.2 28 0.0 96 G- 3 F 340 1.6 30 1.5 110 5.4 67 G- 9 212 18 8.7 1.3 13 0.0 139 G- 10 237 17 5.3 1.1 12 0.0 194 G- 37 391 1.5 27 1.0 112 0.0 65 G- 38 369 4.2 60 1.3 7.3 0.0 656

G- 2 A 1490 3.8 135 2.9 93 2.0 1938 G- 2 F 1960 1.6 77 1.5 0.0 0.0 3322 G- 4 A 1490 3.7 125 1.9 148 2.9 1647 G- 4 F 1500 2.9 43 1.0 34 0.0 1729 G- 7 1878 10 85 1.3 20 1.0 4866

**Table 7.** Electrical conductivity (EC, µS cm-1) and anion concentration (mg kg-1) in soil samples collected from landfill

*Platform*

212 Environmental Risk Assessment of Soil Contamination

*Slope*

*Foot of slope*

*Discharge zones*

proper.


**Table 8.** Electrical conductivity (EC, µS cm-1) and anion concentration (mg kg-1) in soil samples collected from rubble tips.


**Table 9.** Maximum concentration of organic pollutants found in soils of Getafe landfill (mg kg-1) and maximum allowed values according to Spanish law (\*Ref, [27])

### **e. Factors linked to soil erosion**

Signs of soil erosion observed on the landfill's slopes prompted us to address this matter, given the significant effect that soil particle size and the loss of certain fractions can have on the ability of plant species to take root.

The traditional method of Bouyoucos to determine sand, mud and clay fractions was used on all 57 soil samples. In addition, the Mastersizer-S was used to assess particle size by the dispersion and diffraction of a laser light beam as it crosses a suspension of the sample. This technique and the sample preparation method are described in [1]. Particle size was deter‐ mined in 43 of the samples to establish the type of particle that may be lost through erosion. Significant differences in this variable were detected in several fractions of fine sand between soil from the landfill cap and soil from the rubble tips. These results are provided in Figure 5 and table 11. The high standard deviation of the data determined that only differences in the sand fraction of the rubble tip soil were significant.

Although the results obtained using both granulometric techniques are not comparable since the first method gives a percentage weight while the second procedure provides percentage volumes, both revealed that the most marked differences among the higher zones, slopes and lower zones occur in the rubble tips adjacent to the landfill. Table 11 shows the different


**Table 10.** Total concentration of hydrocarbons (HC, mg kg-1) in points of landfill proper and rubble tips and maximum allowed values according to Spanish law (Ref, [27])

**e. Factors linked to soil erosion**

allowed values according to Spanish law (\*Ref, [27])

sand fraction of the rubble tip soil were significant.

of plant species to take root.

Signs of soil erosion observed on the landfill's slopes prompted us to address this matter, given the significant effect that soil particle size and the loss of certain fractions can have on the ability

**Pollutant Max conc. Ref\* Pollutant Max conc. Ref\***

Naphthalene 0.23 1 Alfa-HCH 0.01 0.01 Acenaphthene 0.04 6 Beta-HCH 0.27 0.01 Fluorene 0.09 5 Gamma-HCH 0.48 0.01 Anthracene 0.46 45 Hexachlorobenzene 0.04 0.01 Fluoranthene 2.59 8 Endosulfan 0.07 0.6 Pyrene 2.03 6 p.p'-DDE 0.02 0.6

Chrysene 1.11 20 Total concentration 3408 50

Indene-1,2,3-(cd)pyrene 1.63 0.3 Phenol 0.05 7 Dibenzo(a,h)anthracene 0.14 0.03 Cresols 0.02 4

*PCBs* 3.05 0.01 Pentachlorophenol 0.01 0.01

**Table 9.** Maximum concentration of organic pollutants found in soils of Getafe landfill (mg kg-1) and maximum

2,4,6-trichlorophenol 0.01 0.9

Benzo(b)fluoranthene 1.85 0.2 Conc. of aromatics 335 Benzo(k)fluoranthene 0.89 2 Conc. of aliphatics 3073

*PAHs Insecticides*

214 Environmental Risk Assessment of Soil Contamination

1,2-benzanthracene 0.99 0.2 *Hydrocarbons*

Benzo(a)pyrene 1.56 0.02 *Phenols*

The traditional method of Bouyoucos to determine sand, mud and clay fractions was used on all 57 soil samples. In addition, the Mastersizer-S was used to assess particle size by the dispersion and diffraction of a laser light beam as it crosses a suspension of the sample. This technique and the sample preparation method are described in [1]. Particle size was deter‐ mined in 43 of the samples to establish the type of particle that may be lost through erosion. Significant differences in this variable were detected in several fractions of fine sand between soil from the landfill cap and soil from the rubble tips. These results are provided in Figure 5 and table 11. The high standard deviation of the data determined that only differences in the

Although the results obtained using both granulometric techniques are not comparable since the first method gives a percentage weight while the second procedure provides percentage volumes, both revealed that the most marked differences among the higher zones, slopes and lower zones occur in the rubble tips adjacent to the landfill. Table 11 shows the different

**Figure 5.** Mean percentage of each textural fraction determined by Bouyoucos technique in samples from platforms (P), slopes (S), foots of slopes (FS) and discharge zones (D) in landfill proper and tips. Different letters mean significant differences between means in the same area (Bonferroni, 95%)

granulometric fractions analyzed. For the rubble tips, results indicate the dragging of fine sands from slopes towards the lower zones accompanied by the consequent build-up of coarse sands. Although with a lack of significance, differences were also observed in the remaining fractions.

These data do not seem to clearly indicate the signs produced by the in situ transport of particles from the higher to the lower zones of slopes and discharge areas. No distinguishing factors were revealed in a discriminatory analysis (figure 6). The findings of such a study also indicate the heterogeneity of the situations arising on even a single slope and increase the complexity of understanding the plant colonization pattern, which may vary as small patches depending on these variations produced on a small scale.


**Table 11.** Mean (M) and standard deviation (SD) of percentages of each granulometric fraction in different areas of landfill and tips. Different letters in the same range of particle size mean significant differences between means (Bonferroni, 95%)

#### **3.3. Heterogeneous distribution of pollutants**

Through PCA, we tried to gain insight into the structure of the soil cap used to seal the landfill. In Figure 7A, it may be seen that the first axis, or component, is closely and positively linked to heavy metal and organic compound pollution although Na and F also appeared in this group of variables, and negatively related to soil fertility due to the presence of K and P. The second component was more related to soil salinity, represented by electrical conductivity, chlorides, sulfates, nitrates and nitrites. When organic components and the trace elements Hg and As were excluded, results failed to vary significantly and the first component continued to be positively and closely linked to the presence of heavy metals and negatively linked to that of K (Figure 7B). The second component, more related to salinity or electrical conductivity, this time was linked more to chlorides than the other anions.

granulometric fractions analyzed. For the rubble tips, results indicate the dragging of fine sands from slopes towards the lower zones accompanied by the consequent build-up of coarse sands. Although with a lack of significance, differences were also observed in the remaining

These data do not seem to clearly indicate the signs produced by the in situ transport of particles from the higher to the lower zones of slopes and discharge areas. No distinguishing factors were revealed in a discriminatory analysis (figure 6). The findings of such a study also indicate the heterogeneity of the situations arising on even a single slope and increase the complexity of understanding the plant colonization pattern, which may vary as small patches

> **Fine sand A**

Platform M 0.34 1.93 2.69 7.64 13.7 16.4 23.8 33.4

Slope M 0.46 3.12 3.32 8.85 14.0 14.8 16.7 38.6

Foot of Slope M 0.76 3.87 3.59 9.15 14.3 16.2 13.8 38.4

Discharge zone 0.35 2.30 4.43 11.9 17.6 15.6 13.0 34.8

Slope M 0.20 1.72 3.10 8.89 a 14.5 a 13.3 14.2 b 44.1

Foot of Slope M 0.34 2.30 4.45 12.9 ab 20.1 ab 16.7 12.9 ab 30.4

Discharge zone M 0.26 2.76 5.78 16.0 b 22.9 b 17.8 9.73 a 24.8

**Table 11.** Mean (M) and standard deviation (SD) of percentages of each granulometric fraction in different areas of landfill and tips. Different letters in the same range of particle size mean significant differences between means

Through PCA, we tried to gain insight into the structure of the soil cap used to seal the landfill. In Figure 7A, it may be seen that the first axis, or component, is closely and positively linked

**Range of particle size (mm)**

**<0.002 0.002-0.02 0.02-0.05 0.05-0.1 0.1-0.2 0.2-0.5 0.5-1 1-3.2**

*SD 0.23 0.65 1.39 4.28 6.72 3.10 9.05 14.5*

*SD 0.50 2.28 0.64 2.06 3.4 3.51 7.65 13.9*

*SD 0.65 2.81 0.64 1.87 1.81 3.95 1.55 3.84*

*SD 0.25 0.62 1.37 4.14 6.21 3.8 2.92 15.8*

*SD 0.23 0.45 1.02 3.27 5.03 5.4 1.79 14.5*

*SD 0.21 1.08 2.30 4.95 3.42 1.30 2.20 10.2*

**Fine sand C**

**Medium sand**

**Coarse sand**

**Very coarse sand**

**Fine sand B**

depending on these variations produced on a small scale.

**Clay Mud**

fractions.

216 Environmental Risk Assessment of Soil Contamination

**Area**

*Landfill*

*Tips*

(Bonferroni, 95%)

**3.3. Heterogeneous distribution of pollutants**

**Figure 6.** Representation of discriminant functions calculated with Mastersizer results of landfill soil samples, grouped in platforms (P), slopes (S), foots of slopes (FS) and discharge zones (D).

These findings confirm our previous results indicating that despite the uneven distribution of pollutants, at the most polluted sites all pollutants contribute to this contamination. The PCA plot of points on the new axes (Figures 7C and 7D) serves to visually identify the sites showing highest heavy metal pollution as the landfill slopes and those with the greatest salinity as the rubble tips. The platforms emerged as the least polluted sites both in terms of heavy metals and salts contents.

The chemical analysis results reveal great heterogeneity in both the distributions and concen‐ trations of pollutants. As an example of the complexity of the problem addressed, Zn concen‐ trations range from 9 mg kg-1 to 23000 mg kg-1; maximal Cd concentrations are 308 mg kg-1 (of which 85% represents the easily soluble fraction) and the maximal concentration of total hydrocarbons is 3408 mg kg-1.

The spatial distributions of these factors determined using a Geographical Information System (ArcMapTM software, v. 9.3.1., ESRI) are depicted in Figure 8.
