**5. Results**

Figure 6. Sampling directions from industrial area of Targoviste city according to the pollution rose

Sampling of soil was done at distances between 50 and 1000 meters from the source of pollution, from five different points, chosen according to triangle method. The results of metal concentration represent the average of these five samples. From each sampling point, samples were taken from three layers: the upper layer (0-5 cm depth), middle layer (5-20 cm depth) and lower layer (20-40 cm depth). These layers were chosen according with the depth to which the

The soil samples were processed in the laboratory for elemental analysis by ICP-AES. The soil samples were dried at 40 °C for 24 hours, ground to a fine powder, sieved at 250 µm (according

Determination of heavy metal concentration in soil was done on replicates samples by Inductively Coupled Plasma - Atomic Emission Spectrometry method (ICP-AES). The soils samples were mineralized in Berghof microwave digester, using a mixture 1:1 with nitric acid (according with Berghof method) prior to ICP-AES analyses. The advantage of ICP-AES is the multielemental detection (Cu, Zn, Sn, Pb, Co, Ni, Mn, Cr and Mo) [24]. For this research, analyses were conducted with Liberty 110 spectrometer of Varian brand. The minimal detection limits of device range according to the analysed element and is 0.4 mg/kg for Zn, Mn

**Figure 6.** Sampling directions from industrial area of Targoviste city according to the pollution rose

In soils with alluvial B horizon, such as soil in

the industrial area of the Targoviste city, colloidal order mineral fraction of this horizon contains large amounts of colloidal hydroxides (e.g. Fe(OH)3 and Al(OH)3) and various hydrated iron and aluminium sesquioxides free-form (mR2O3·nH2O) [23]. Large amounts of iron hydroxides in the humus horizon could be observed for the brown and reddish-brown soils from the industrial zone of Targoviste (Figure 5). The presence of these hydroxides is manifested by brown-yellowish, brown, reddish-brown, yellowishrusty or rusty lit of the horizon where they are

Characteristic types of soils for studied area are gray luvisol and gray brown luvisol

Bioaccumulation in upper and middle horizon was low; plant debris was mostly

(Figure 4) according SRTS-2003 (reddish brown after SRCS 1980), soils of a reddish hue, quite evident in the upper horizon and really evident in the middle horizon. Water and air permeability of the soil was moderate. Humus content was about 3%, nutrient supply was moderate, the soil reaction was low-acid with pH values in the range of 6.0 to 6.4, and the

decomposed by the action of fungi, and could be observed the formation of small amounts of humus with predominating fulvic acids. Due to intense alteration of mineral component occurs removal of clay colloid from the surface, with accumulation in the Bt horizon, where

deposited.

268 Environmental Risk Assessment of Soil Contamination

respectively. Land at NE, E and SE from the source of pollution, are grouped according with the use category in Zone II – agricultural fields sensitive to high concentrations of heavy

of pollution, from five different points, chosen according to triangle method. The results of metal concentration represent the average of these five samples. From each sampling point, samples were taken from three layers: the upper layer (0-5 cm depth), middle layer (5-20 cm depth) and lower layer (20-40 cm depth). These layers were chosen according with the

**4.2. Analytical methods**

to SR ISO 11464).

Sampling of soil was done at distances between 50 and 1000 meters from the source

roots of culture plant normally develop.

degree of base saturation was 80% to 85%.

the profile shows a textural differentiation.

**4. Material and method**  *4.1 Experimental design* 

Figure 5. Iron hydroxides

to reflect a snapshot of the impact of metallurgical activities in this area by particles emissions. Based on weather conditions and pollution direction compass of Dâmboviţa County (Figure 6), were determined that areas found at SW and W towards the emission source are the most affected. In that location have been chosen the harvest area Zone I – industrial fields, with two subzones, for SW and W directions

metals.

Sampling points were chosen

depth to which the roots of culture plant normally develop.

## **5.1. Statistical results of heavy metal concentration**

In the industrial area of Targoviste city, the concentration of heavy metals in soil was highly dependent on the metal species, the position of sampling point towards the source of pollution, the stack, and the depth of sampling. The general statistical results of heavy metal concentra‐ tion in studied area are presented in Table 2.

The variation of Cu concentration in the 0-5 cm layer of soil was higher than the variation on the profile. Cu concentration ranged from 578.4 mg/kg in the surface layer, to 170.4 mg/kg (5 -20 cm) and 152.4 mg/kg (20-40 cm). The Cu concentration variation showed that 75% of the samples had values of concentration up to 135.9 mg/kg, and only 25% of the samples had higher concentrations than this value. The same pattern of variation of Cu concentration was followed for the deeper layers. For the layer of 5-20 cm depth, most samples (75%) had concentrations within a narrow range, from 28.7 to 43.6 mg/kg and for the layer of 20-40 cm depth 75% of samples range between 22.0 to 55.2 mg/kg.

The variation of Zn concentration was very high at the surface of soil profile (827.7 mg/kg) and lower in the deeper layers of soil (128.8 mg/kg and 186.9 mg/kg respectively. In all the three studied layers, the concentration of Zn in most of the samples was placed in a very small range as compared to the magnitude of total concentration range. In the surface layer, 50% of the samples showed a concentration of Zn from 42.6 to 86.1 mg/kg and 75% were found between 42.64 to 225.03 mg/kg. The same pattern of distribution of Zn concentration was followed in the deeper layers, 75% of the samples being in a relatively narrow range of concentration from 44.4 to 72.9 mg/kg for the depth of 5-20 cm and 33.1 to 81.8 mg/kg for the layer of 20-40 cm depth.

The values of Sn concentration showed a higher homogeneity in soil when compared to Cu and Zn concentration. Sn concentration ranged from 92.7 mg/kg at the surface of profile to about 40 mg/kg in deeper layers (5-40 cm). The four quadrants of Sn concentration distribution showed narrow values, though there was a concentration of Sn values (50%) in the range 32.7 to 53.9 mg/kg for 0-5 cm layer. In the middle layer (5-20 cm), about 75% of the sample ranged from <LD to 20.9 mg/kg. At 20-40 cm depth, quadrants II and III of the concentration distri‐ bution were distributed on the interval from 15.39 to 22.8 mg/kg, the remaining 50% of the samples having values lower or higher than this range.


**Table 2** Statistical results of heavy metal concentration (mg/kg) in soil surrounding the industrial area of Targoviste city

The variability of Pb concentration was very high, most of the samples showing very low levels, even below the detection limit of the analytical method, in the entire soil profile studied, while some samples presented significant concentrations of Pb up to 294.3 mg/kg (0-5 cm), 121.0 mg/ kg (5 to 20 cm deep) and 145.6 mg/kg (20-40 cm). The distribution of the samples in terms of the concentration was varying, 75% of the samples from the surface of soil profile were in the range of concentrations from 0 to 92.1 mg/kg, and the remaining 25% were in the range of 92.1 to 294.3 mg/kg. The Pb distribution was less variable in the deeper layers, the four quadrants of the concentration being distributed at relatively equal intervals, especially for the depth 5-20 cm. Heterogeneity of the sample in terms of the concentration of lead in the ground was indicated by the high value of the standard deviation, higher than the average concentration throughout the studied soil profile.

**Metal Depth Mean±SD Min-Max Median Q1 Q3 Skewness Kurtosis Cu** 0-5 cm 125.5±162.6 22.0-600.4 36.5 30.9 135.9 2.1185 4.6664

270 Environmental Risk Assessment of Soil Contamination

**Zn** 0-5 cm 223.9±269.0 42.6-870.3 86.1 73.3 225.0 1.6278 1.3552

**Sn** 0-5 cm 65.1±30.2 32.7-125.4 53.9 41.9 84.8 0.7305 -0.7436

**Pb** 0-5 cm 76.4±98.9 0.6-294.3 43.3 0.66 92.1 1.3987 0.8529

**Co** 0-5 cm 16.2±4.8 7.1-23.5 17.3 12.9 19.1 -0.5281 -0.4808

**Ni** 0-5 cm 65.1±58.5 13.8-185.4 37.6 22.0 84.8 1.0999 -0.1291

**Mn** 0-5 cm 1579.7±352.3 1159.9-2348.0 1419.1 1373.2 1731.3 0.9420 0.0714

**Cr** 0-5 cm 114.6±125.5 13.7-315.6 25.1 21.6 205.7 0.7343 -1.3288

**Mo** 0-5 cm 7.2±7.8 0.6-23.4 4.5 0.6 10.5 1.0334 -0.1858

**Table 2** Statistical results of heavy metal concentration (mg/kg) in soil surrounding the industrial area of Targoviste

The variability of Pb concentration was very high, most of the samples showing very low levels, even below the detection limit of the analytical method, in the entire soil profile studied, while some samples presented significant concentrations of Pb up to 294.3 mg/kg (0-5 cm), 121.0 mg/

LD – limit of detection

city

5-20 cm 61.1±55.0 28.7-199.1 35.1 32.5 43.6 1.8284 1.9995 20-40 cm 63.3±53.1 22.0-174.5 38.1 35.4 55.2 1.5680 0.7874

5-20 cm 74.3±42.9 44.4-173.2 54.1 48.4 72.9 1.5888 1.0601 20-40 cm 75.6±50.61 33.1-220.1 53.1 49.4 81.8 1.9591 4.0515

5-20 cm 12.9±12.9 <LD-44.4 14.9 <LD 20.9 0.8094 0.8786 20-40 cm 17.8±10.9 <LD-38.2 19.4 15.4 22.8 -0.3501 0.0826

5-20 cm 47.9±42.6 <LD-121.0 42.5 20.86 64.1 0.7683 -0.5585 20-40 cm 34.0±43.6 <LD-145.6 26.3 <LD 35.6 1.5800 2.0421

5-20 cm 14.7±5.1 6.7-21.5 13.6 10.3 19.4 -0.0702 -1.6268 20-40 cm 13.1±4.0 6.7-19.9 14.9 9.5 15.6 -0.3423 -0.9854

5-20 cm 20.2±15.9 8.7-52.7 13.1 12.3 14.8 1.6371 0.8719 20-40 cm 23.2±23.9 4.4-72.4 14.2 8.3 17.7 1.5576 0.7595

5-20 cm 1348.9±243.6 758.9-1677.3 1384.1 1322.7 1504.3 -1.2771 1.5204 20-40 cm 1367.5±327.9 720.4-1763.1 1486.3 1258.4 1601.1 -1.0239 -0.1494

5-20 cm 46.0±51.7 16.2-168.3 22.7 17.81 30.4 1.7522 1.5205 20-40 cm 41.0±52.9 8.2-159.9 18.3 13.8 21.5 1.6981 1.1754

5-20 cm 3.0±3.4 <LD-10.8 1.2 0.7 5.1 1.1289 0.2488 20-40 cm 2.4±3.3 <LD-9.7 1.0 0.6 1.6 1.6104 0.9883 The concentrations of Co in the samples were distributed homogeneously throughout the range of concentrations for both the upper layer and deeper layers of 5-20 cm and 20-40 cm respectively. The homogeneity of the samples was indicated by the low values of standard deviation, between 29% and 34% of the average, and by the median value that was very close to the average value, 17.3 mg/kg, 13.6 mg/kg, respectively 14.9 mg/kg for the three depths. On the surface of the soil profile, 50% of the analysed samples were in the range of concentration from 12.9 to 19.1 mg/kg.

In surface layer of soil, the range of Ni concentration varied widely, up to 185.4 mg/kg. The soil sample from surface layer presented heterogeneous distribution of Ni, with 75% of the samples from 0-5 cm depth showing a concentration ranging 13.8 to 84.8 mg/kg, and only 25% of the samples ranging 84.8 to 185.4 mg/kg. The Ni concentration variation was lower in deeper layers; most of the samples (75%) were covered by a much narrower range of concentration from 8.7 to 14.8 mg/kg for 5-20 cm depth, and 4.4 to 17.7 mg/kg for 20-40 cm depth.

Distribution of samples within the range of Mn concentration was uniform and 50% of the samples were within the range of 1373.2 to 1731.3 mg/kg, while the remaining 50% of the samples from the surface of the soil profile were higher or lower than this range. The same pattern of samples distribution was followed in the deeper layers, where 50% of the samples were concentrated in the middle of the range of Mn concentration. The standard deviation of the Mn concentration indicates that the samples had similar values of concentration for each layer, accounting 22%, 18% and 24% respectively for the three layers of 0-5 cm, 5-20 cm and 20-40 cm.

The wide variation of Cr concentration in the samples was reflected by the high value of standard deviation, greater than the average concentration for all three depths. Half of the samples from 0-5 cm layer of soil showed Cr concentrations in a very small range between 13.7 and 25.1 mg/kg. The remaining 50% of the samples were distributed in a wider concentration range between 25.1 and 315.6 mg/kg. At depths greater than 5 cm, 75% of the investigated samples had concentrations of Cr in a narrow range of 14.2 mg/kg for the depth of 5-20 cm and 13.3 mg/kg for the depth of 20-40 cm, while the remaining 25% had concentrations in the range of 137.9 mg/kg and 138.4 mg/kg respectively for the two layers of soil.

The range of Mo concentration was higher in the surface of soil profile (22.8 mg/kg) compared to the range of concentration of deeper layers of soil (10.8 mg/kg and 9.7 mg/kg respectively). The majority of samples (75%) showed low levels of Mo, up to 10.5 mg/kg on the surface and 5.1 mg/kg and 1.6 mg/kg in the deeper layers of 5-20 cm and 20-40 cm respectively. The concentration varied greatly, with values of standard deviation higher than the mean concentration.

#### **5.2. Horizontal distribution of heavy metals**

The horizontal distribution of heavy metals and level of metal pollution in the industrial area of Targoviste city was established by comparing to the Romanian legislation [3], which regulates normal values, alert thresholds and action levels for different trace elements by use of soils, agricultural and industrial land (Table 3).


**Table 3** Normal values and alert thresholds of heavy metal concentration (mg/kg) for agricultural and industrial soil in Romania [3]

The concentration of Cu on the surface layer of soil differed greatly between the two studied zones (I and II) (Table 4). Thus, in Zone I, on the SW and W directions towards the emission source, the concentration of Cu reached 401.44 mg/kg and 134.58 mg/kg, values of 7 to 20 times higher than normal levels in this category of soils [25]. In Zone II, the concentrations of Cu on the NE, E and SE directions were slightly greater than the normal value of concentration, ranging between 22.37 and 36.61 mg/kg.

In the case of Zn, the maximum values allowed for industrial soil, 700 mg/kg were overcome on W direction to the source, while the value on SW direction was below that limit, but exceeded the normal value of Zn in soil. The soils in Zone II showed a deficiency of Zn at surface layer and in the deeper layers. In the upper horizon, the Zn concentration was between 46.03 and 86.07 mg/kg, values that are below the normal value of this element in soil [26].

Sn concentrations in the analysed soils were above normal values (Table 4) in both the Zone I and Zone II. A concentration of about 6 times the normal limit was found in soils under the SW direction. For other samples, the concentration of Sn in soil ranged from 33.77 to 82.90 mg/ kg, the lowest value being on E direction and the highest on SE direction.

Although the normal value of Pb in soil is 20 mg/kg, the concentration of this element in the studied samples of soils did not exceed the threshold. The soil in Zone II showed the lowest concentration. In the SE direction, Pb concentration in soil was the highest, 43.35 mg/kg. The soil in the Zone I, showed values of Pb concentration that exceeded 4 to 12 times the normal values: 85.38 mg/kg in the SW direction and 252.00 mg/kg on the W direction.

The concentrations of Co in soils were not much higher than the normal values of metal concentration in soil. Higher values were found in the soil from Zone I, 19.93 mg/kg in the W Assessment of Historical Heavy Metal Pollution of Land in the Proximity of Industrial Area of Targoviste, Romania http://dx.doi.org/10.5772/58304 273


respectively. The concentration varied greatly, with values of standard deviation higher

The horizontal distribution of heavy metals and level of metal pollution in the industrial area of Targoviste city was established by comparing to the Romanian legislation [3], which regulates normal values, alert thresholds and action levels for different trace elements by use

**Limit Cu Zn Sn Pb Co Ni Mn Cr Mo NV** 20 100 20 20 15 20 900 30 2 **ATA** 100 300 35 50 30 75 1500 100 5 **ATI** 250 700 100 250 100 200 2000 300 15

**Table 3** Normal values and alert thresholds of heavy metal concentration (mg/kg) for agricultural and industrial soil in

The concentration of Cu on the surface layer of soil differed greatly between the two studied zones (I and II) (Table 4). Thus, in Zone I, on the SW and W directions towards the emission source, the concentration of Cu reached 401.44 mg/kg and 134.58 mg/kg, values of 7 to 20 times higher than normal levels in this category of soils [25]. In Zone II, the concentrations of Cu on the NE, E and SE directions were slightly greater than the normal value of concentration,

In the case of Zn, the maximum values allowed for industrial soil, 700 mg/kg were overcome on W direction to the source, while the value on SW direction was below that limit, but exceeded the normal value of Zn in soil. The soils in Zone II showed a deficiency of Zn at surface layer and in the deeper layers. In the upper horizon, the Zn concentration was between 46.03 and 86.07 mg/kg, values that are below the normal value of this element in soil [26].

Sn concentrations in the analysed soils were above normal values (Table 4) in both the Zone I and Zone II. A concentration of about 6 times the normal limit was found in soils under the SW direction. For other samples, the concentration of Sn in soil ranged from 33.77 to 82.90 mg/

Although the normal value of Pb in soil is 20 mg/kg, the concentration of this element in the studied samples of soils did not exceed the threshold. The soil in Zone II showed the lowest concentration. In the SE direction, Pb concentration in soil was the highest, 43.35 mg/kg. The soil in the Zone I, showed values of Pb concentration that exceeded 4 to 12 times the normal

The concentrations of Co in soils were not much higher than the normal values of metal concentration in soil. Higher values were found in the soil from Zone I, 19.93 mg/kg in the W

kg, the lowest value being on E direction and the highest on SE direction.

values: 85.38 mg/kg in the SW direction and 252.00 mg/kg on the W direction.

NV – normal values; ATA – alert threshold for agricultural soil; ATI – alert threshold for industrial soil

than the mean concentration.

272 Environmental Risk Assessment of Soil Contamination

Romania [3]

**5.2. Horizontal distribution of heavy metals**

of soils, agricultural and industrial land (Table 3).

ranging between 22.37 and 36.61 mg/kg.

**Table 4** Horizontal distribution of heavy metal concentrations (mg/kg) in the industrial area of Târgovişte city

direction and 20.42 mg/kg in the SW direction. The soils in the Zone II showed values of Co concentrations that varied between 8.94 and 17.48 mg/kg. The lowest value was on E direction, and the highest value on SE direction.

The concentration of Ni in soils varied widely in the two studied zones. In Zone I, the con‐ centration of Ni was between 4 and 8 times higher than the normal value of metal concentration in soil, 83.84 mg/kg in the W direction and 166.64 mg/kg on the SW direction. The soil in Zone II showed Ni concentration close to normal values, ranging from 15.01 to 37.39 mg/kg. The highest value was for the Ni concentration on SE direction.

Concentration of Mn in the soil was two times higher than the normal value and range between 1264.26 mg/kg and 2156.48 mg/kg. The lowest value of Mn concentration was on SW direction and the higher on the W direction.

Concentrations of Cr in soils from the industrial area were very different between the two studied zones. In Zone I, the concentrations were extremely high compared to the normal limit (30 mg/kg), reaching values over 10 times higher: 200.33 mg/kg and 312.33 mg/kg on SW and W directions respectively. In Zone II, Cr concentration showed values below the normal concentration of Cr in this type of soil, and varied between 13.88 and 24.98 mg/kg [27].

Molybdenum concentration in the surface layer of soil varied within wide limits, irrespective of the position towards the source of pollution. In Zone I, concentration of Mo has the minimum value in the W direction (0.6 mg/kg), and the maximum value in the SW direction (9.79 mg/ kg). This value was about 5 times higher than the normal value of Mo concentration in soil. In Zone II, the concentration of this metal varied also within wide limits, from 0.65 mg/kg in the E direction to 20.57 mg/kg in the NE direction. The recorded values were more than 10 times higher than normal values.

#### **5.3. Vertical distribution of heavy metals** Molybdenum concentration in the surface layer of soil varied within wide limits,

The vertical distribution of heavy metals in the soil profile (0 – 40 cm) is shown in figures 7 – 14, which indicates the level of heavy metals in the three soil layers: 0 – 5 cm, 5 – 20 cm and 20 – 40 cm. For each layer, linear regression was calculated to indicate correlations of heavy metal concentrations with the pH. has the minimum value in the W direction (0.6 mg/kg), and the maximum value in the SW direction (9.79 mg/kg). This value was about 5 times higher than the normal value of Mo concentration in soil. In Zone II, the concentration of this metal varied also within wide limits, from 0.65 mg/kg in the E direction to 20.57 mg/kg in the NE direction. The recorded values were more than 10 times higher than normal values.

irrespective of the position towards the source of pollution. In Zone I, concentration of Mo

The high concentrations of Cu in the SW direction were maintained at very high level in the depth of soil profile (Figure 7). In the W direction, Cu concentration decrease to depth of 40 cm to levels of 27 mg/kg. The soil in Zone II showed similar values of Cu concentration on the entire profile of soil. Between the Cu concentration and the pH of soil was observed a moderate correlation in the surface layer of soil (0.3) and very low correlations for the two deeper layers. All the correlations were positive. *5.3 Vertical distribution of heavy metals*  The vertical distribution of heavy metals in the soil profile (0 – 40 cm) is shown in figures 7 – 14, which indicates the level of heavy metals in the three soil layers: 0 – 5 cm, 5 – 20 cm and 20 – 40 cm. For each layer, linear regression was calculated to indicate correlations of heavy metal concentrations with the pH. The high concentrations of Cu in the SW direction were maintained at very high level in the depth of soil profile (Figure 7). In the W direction, Cu concentration decrease to depth

Extremely high Zn concentration from the surface layer of soil did not maintained in depth. Below 5 cm depth the concentration of Zn decreased to values lower than 35 mg/kg (Figure 8). In the SW direction, the concentration of Zn in the deeper layers of soil remained at levels comparable to the surface layer, ranging between 154.38 and 194.28 mg/kg. The lowest values were in the middle of the soil profile, and the highest values on surface layer. The design of the Zn distribution in soil was maintained in Zone II. The highest concentrations were on the surface, decreased in the middle of soil profile, and increased in the lower part of the profile. The concentrations of Zn to this area were between 46.03 and 86.07 mg/kg. Correlation between the Zn concentrations in the soil with its pH is strong in the upper layer (0.48), and very low to depth. of 40 cm to levels of 27 mg/kg. The soil in Zone II showed similar values of Cu concentration on the entire profile of soil. Between the Cu concentration and the pH of soil was observed a moderate correlation in the surface layer of soil (0.3) and very low correlations for the two deeper layers. All the correlations were positive. Extremely high Zn concentration from the surface layer of soil did not maintained in depth. Below 5 cm depth the concentration of Zn decreased to values lower than 35 mg/kg (Figure 8). In the SW direction, the concentration of Zn in the deeper layers of soil remained at levels comparable to the surface layer, ranging between 154.38 and 194.28 mg/kg. The lowest values were in the middle of the soil profile, and the highest values on surface layer. The design of the Zn distribution in soil was maintained in Zone II. The highest concentrations were on the surface, decreased in the middle of soil profile, and increased in the lower part of the profile. The concentrations of Zn to this area were between 46.03 and

86.07 mg/kg. Correlation between the Zn concentrations in the soil with its pH is strong in

Figure 7. Copper vertical distribution in soil and correlation with pH **Figure 7.** Copper vertical distribution in soil and correlation with pH

the upper layer (0.48), and very low to depth.

Assessment of Historical Heavy Metal Pollution of Land in the Proximity of Industrial Area of Targoviste, Romania http://dx.doi.org/10.5772/58304 275

Figure 8. Zinc vertical distribution in soil and correlation with pH In contrast to Cu and Zn, Sn distribution in the soil profile showed a very wide **Figure 8.** Zinc vertical distribution in soil and correlation with pH

E direction to 20.57 mg/kg in the NE direction. The recorded values were more than 10 times

The vertical distribution of heavy metals in the soil profile (0 – 40 cm) is shown in figures 7 – 14, which indicates the level of heavy metals in the three soil layers: 0 – 5 cm, 5 – 20 cm and 20 – 40 cm. For each layer, linear regression was calculated to indicate correlations of heavy metal

Molybdenum concentration in the surface layer of soil varied within wide limits, irrespective of the position towards the source of pollution. In Zone I, concentration of Mo has the minimum value in the W direction (0.6 mg/kg), and the maximum value in the SW direction (9.79 mg/kg). This value was about 5 times higher than the normal value of Mo concentration in soil. In Zone II, the concentration of this metal varied also within wide limits, from 0.65 mg/kg in the E direction to 20.57 mg/kg in the NE direction. The recorded values

The high concentrations of Cu in the SW direction were maintained at very high level in the depth of soil profile (Figure 7). In the W direction, Cu concentration decrease to depth of 40 cm to levels of 27 mg/kg. The soil in Zone II showed similar values of Cu concentration on the entire profile of soil. Between the Cu concentration and the pH of soil was observed a moderate correlation in the surface layer of soil (0.3) and very low correlations for the two deeper layers.

The vertical distribution of heavy metals in the soil profile (0 – 40 cm) is shown in figures 7 – 14, which indicates the level of heavy metals in the three soil layers: 0 – 5 cm, 5 – 20 cm and 20 – 40 cm. For each layer, linear regression was calculated to indicate

The high concentrations of Cu in the SW direction were maintained at very high level in the depth of soil profile (Figure 7). In the W direction, Cu concentration decrease to depth of 40 cm to levels of 27 mg/kg. The soil in Zone II showed similar values of Cu concentration on the entire profile of soil. Between the Cu concentration and the pH of soil was observed a moderate correlation in the surface layer of soil (0.3) and very low correlations for the two

Extremely high Zn concentration from the surface layer of soil did not maintained in depth. Below 5 cm depth the concentration of Zn decreased to values lower than 35 mg/kg (Figure 8). In the SW direction, the concentration of Zn in the deeper layers of soil remained at levels comparable to the surface layer, ranging between 154.38 and 194.28 mg/kg. The lowest values were in the middle of the soil profile, and the highest values on surface layer. The design of the Zn distribution in soil was maintained in Zone II. The highest concentrations were on the surface, decreased in the middle of soil profile, and increased in the lower part of the profile. The concentrations of Zn to this area were between 46.03 and 86.07 mg/kg. Correlation between the Zn concentrations in the soil with its pH is strong in

Figure 7. Copper vertical distribution in soil and correlation with pH

R² = 0.0824

6.00 7.00 8.00

R² = 0.0662

6.00 7.00 8.00

SW

W

NE

E

SE

0-5cm 5-20 cm 20-40 cm

Extremely high Zn concentration from the surface layer of soil did not maintained in depth. Below 5 cm depth the concentration of Zn decreased to values lower than 35 mg/kg (Figure 8). In the SW direction, the concentration of Zn in the deeper layers of soil remained at levels comparable to the surface layer, ranging between 154.38 and 194.28 mg/kg. The lowest values were in the middle of the soil profile, and the highest values on surface layer. The design of the Zn distribution in soil was maintained in Zone II. The highest concentrations were on the surface, decreased in the middle of soil profile, and increased in the lower part of the profile. The concentrations of Zn to this area were between 46.03 and 86.07 mg/kg. Correlation between the Zn concentrations in the soil with its pH is strong in the upper layer (0.48), and very low

higher than normal values.

concentrations with the pH.

All the correlations were positive.

to depth.

**Cu concentration (mg/kg)**

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00 400.00 450.00

**5.3. Vertical distribution of heavy metals**

274 Environmental Risk Assessment of Soil Contamination

were more than 10 times higher than normal values. *5.3 Vertical distribution of heavy metals* 

correlations of heavy metal concentrations with the pH.

deeper layers. All the correlations were positive.

the upper layer (0.48), and very low to depth.

R² = 0.3003

6.00 7.00 8.00

**Figure 7.** Copper vertical distribution in soil and correlation with pH

variance (Figure 9). The surface layer showed Sn concentration much higher than in depth. For all studied direction, was observed that the concentration of Sn decreased towards the centre, and grow on the bottom of the profile. Correlation between the Sn concentrations and the pH of soil is positive, but to a different extent, depending on the depth. Thus, the surface layer had a very low correlation, in the 5-20 cm layer the correlation was low, and the bottom of soil profile the correlation was moderate (> 0.4). Distribution of Pb in the soil did not follow a pattern, but varied from one area to another. Thus, the high Pb concentration from the surface, in the W direction, decreased In contrast to Cu and Zn, Sn distribution in the soil profile showed a very wide variance (Figure 9). The surface layer showed Sn concentration much higher than in depth. For all studied direction, was observed that the concentration of Sn decreased towards the centre, and grow on the bottom of the profile. Correlation between the Sn concentrations and the pH of soil is positive, but to a different extent, depending on the depth. Thus, the surface layer had a very low correlation, in the 5-20 cm layer the correlation was low, and the bottom of soil profile the correlation was moderate (> 0.4).

sharply towards the middle of soil profile, and continues to decrease to the bottom of the profile (Figure 10). In the SW and E directions, the Pb concentration was higher in the middle and lower soil profile than in the upper horizon, far exceeding the normal value of Pb concentration in soil. In the NE and SE directions, Pb concentrations were similar throughout the entire soil profile. The correlation between the Pb concentrations in soil and the pH decreased from the surface to the depth of soil profile. The correlation was moderate positive in the upper layer (0.47), and low but positive to the bottom of soil profile. 100.00 120.00 R² = 0.1099 R² = 0.0003 6.00 7.00 8.00 Distribution of Pb in the soil did not follow a pattern, but varied from one area to another. Thus, the high Pb concentration from the surface, in the W direction, decreased sharply towards the middle of soil profile, and continues to decrease to the bottom of the profile (Figure 10). In the SW and E directions, the Pb concentration was higher in the middle and lower soil profile than in the upper horizon, far exceeding the normal value of Pb concentration in soil. In the NE and SE directions, Pb concentrations were similar throughout the entire soil profile. The correlation between the Pb concentrations in soil and the pH decreased from the surface to the depth of soil profile. The correlation was moderate positive in the upper layer (0.47), and low but positive to the bottom of soil profile.

0.00 20.00 40.00 60.00 80.00 **Sn concentration (mg/kg)**SW W NE E SE R² = 0.4283 6.00 7.00 8.00 6.00 7.00 8.00 The distribution of Co on the soil profile varied from one point to another (Figure 11). In the SW, SE and E directions, the Co concentration in the soil increased slightly in the middle of soil profile and decreased sharply towards the bottom of it. In the W direction, the Co concentration decreased sharply towards the centre of soil profile and continues to decrease to the bottom thereof. In the NE direction, the Co concentration is higher in the lower part of the profile as compared to the upper layers. The correlation between the Co concentrations in soil and pH varied on the soil profile as intensity. In the upper layers, the correlation is positive, but very low (<0.2), while the lower layers showed weak negative correlation (0.2 - 0.4).

Figure 9. Tin vertical distribution in soil and correlation with pH 0-5cm 5-20 cm 20-40 cm Nickel concentration varied along the profile of soil. Much higher values were observed in the surface layer of soil compared to the values representing the concentration of Ni in the middle of the profile. At the bottom of the profile, the concentrations increased slightly (Figure 12).

Figure 9. Tin vertical distribution in soil and correlation with pH **Figure 9.** Tin vertical distribution in soil and correlation with pH

Figure 10. Lead vertical distribution in soil and correlation with pH Figure 10. Lead vertical distribution in soil and correlation with pH The distribution of Co on the soil profile varied from one point to another (Figure 11). **Figure 10.** Lead vertical distribution in soil and correlation with pH

R² = 0.0755

6.00 7.00 8.00

profile.

0.00

5.00

10.00

15.00

For soil samples collected in the SW direction, the metal concentrations maintained at high value on the entire soil profile compared to other directions. In the W direction, the surface layer showed much higher concentrations of Ni, and in the deeper layers the value of Ni concentration were still high. The correlation between the Ni concentrations in soil and the pH was low, positive and decreased in intensity with the depth profile. The distribution of Co on the soil profile varied from one point to another (Figure 11). In the SW, SE and E directions, the Co concentration in the soil increased slightly in the middle of soil profile and decreased sharply towards the bottom of it. In the W direction, the Co concentration decreased sharply towards the centre of soil profile and continues to decrease to the bottom thereof. In the NE direction, the Co concentration is higher in the lower part of the profile as compared to the upper layers. The correlation between the Co In the SW, SE and E directions, the Co concentration in the soil increased slightly in the middle of soil profile and decreased sharply towards the bottom of it. In the W direction, the Co concentration decreased sharply towards the centre of soil profile and continues to decrease to the bottom thereof. In the NE direction, the Co concentration is higher in the lower part of the profile as compared to the upper layers. The correlation between the Co concentrations in soil and pH varied on the soil profile as intensity. In the upper layers, the correlation is positive, but very low (<0.2), while the lower layers showed weak negative

Except for samples collected west from the pollution source, distribution of Mn was approxi‐ mately uniform throughout the soil profile, the concentration ranging between 942.32 mg/kg and 1578.64 mg/kg at 5-20 cm depth, and between 796.68 and 1631.13 mg/kg at 20-40 cm depth (Figure 13). The surface layer showed a low correlation between the Mn concentrations and correlation is positive, but very low (<0.2), while the lower layers showed weak negative correlation (0.2 - 0.4). correlation (0.2 - 0.4). 20.00 25.00 **Co concentration (mg/kg)** R² = 0.217

SW

6.00 7.00 8.00

W

NE

E

SE

Figure 11. Cobalt vertical distribution in soil and correlation with pH Nickel concentration varied along the profile of soil. Much higher values were observed in the surface layer of soil compared to the values representing the concentration of Ni in the middle of the profile. At the bottom of the profile, the concentrations increased slightly (Figure 12). For soil samples collected in the SW direction, the metal concentrations maintained at high value on the entire soil profile compared to other directions. In the W direction, the surface layer showed much higher concentrations of Ni, and in the deeper layers the value of Ni concentration were still high. The correlation between the Ni concentrations in soil and the pH was low, positive and decreased in intensity with the depth

0-5cm 5-20 cm 20-40 cm

6.00 7.00 8.00

R² = 0.2217

concentrations in soil and pH varied on the soil profile as intensity. In the upper layers, the

Assessment of Historical Heavy Metal Pollution of Land in the Proximity of Industrial Area of Targoviste, Romania http://dx.doi.org/10.5772/58304 277

Figure 11. Cobalt vertical distribution in soil and correlation with pH **Figure 11.** Cobalt vertical distribution in soil and correlation with pH

lower part of the soil profile correlation was moderate.

pH, in the 5-20 cm layer the correlation was strong (> 0.6) and in the lower part of the soil profile correlation was moderate. Except for samples collected west from the pollution source, distribution of Mn was approximately uniform throughout the soil profile, the concentration ranging between 942.32 mg/kg and 1578.64 mg/kg at 5-20 cm depth, and between 796.68 and 1631.13 mg/kg at 20- 40 cm depth (Figure 13). The surface layer showed a low correlation between the Mn Nickel concentration varied along the profile of soil. Much higher values were observed in the surface layer of soil compared to the values representing the concentration of Ni in the middle of the profile. At the bottom of the profile, the concentrations increased

concentrations and pH, in the 5-20 cm layer the correlation was strong (> 0.6) and in the

slightly (Figure 12). For soil samples collected in the SW direction, the metal concentrations maintained at high value on the entire soil profile compared to other directions. In the W direction, the surface layer showed much higher concentrations of Ni, and in the deeper

2500.00 **Figure 12.** Nickel vertical distribution in soil and correlation with pH 80.00 6.00 7.00 8.00

R² = 0.1357

6.00 7.00 8.00

0.00

500.00

100.00

For soil samples collected in the SW direction, the metal concentrations maintained at high value on the entire soil profile compared to other directions. In the W direction, the surface layer showed much higher concentrations of Ni, and in the deeper layers the value of Ni concentration were still high. The correlation between the Ni concentrations in soil and the pH

The distribution of Co on the soil profile varied from one point to another (Figure 11). In the SW, SE and E directions, the Co concentration in the soil increased slightly in the middle of soil profile and decreased sharply towards the bottom of it. In the W direction, the Co concentration decreased sharply towards the centre of soil profile and continues to decrease to the bottom thereof. In the NE direction, the Co concentration is higher in the lower part of the profile as compared to the upper layers. The correlation between the Co concentrations in soil and pH varied on the soil profile as intensity. In the upper layers, the correlation is positive, but very low (<0.2), while the lower layers showed weak negative

Figure 10. Lead vertical distribution in soil and correlation with pH

Figure 10. Lead vertical distribution in soil and correlation with pH The distribution of Co on the soil profile varied from one point to another (Figure 11). In the SW, SE and E directions, the Co concentration in the soil increased slightly in the middle of soil profile and decreased sharply towards the bottom of it. In the W direction, the Co concentration decreased sharply towards the centre of soil profile and continues to decrease to the bottom thereof. In the NE direction, the Co concentration is higher in the lower part of the profile as compared to the upper layers. The correlation between the Co concentrations in soil and pH varied on the soil profile as intensity. In the upper layers, the correlation is positive, but very low (<0.2), while the lower layers showed weak negative

0-5cm 5-20 cm 20-40 cm

0-5cm 5-20 cm 20-40 cm

6.00 7.00 8.00

6.00 7.00 8.00

Figure 9. Tin vertical distribution in soil and correlation with pH

R² = 0.3508

R² = 0.3508

0-5cm 5-20 cm 20-40 cm

R² = 0.1099

6.00 7.00 8.00

SW

R² = 0.4283

6.00 7.00 8.00

R² = 0.1048

R² = 0.217

6.00 7.00 8.00

R² = 0.1048

6.00 7.00 8.00

6.00 7.00 8.00

W

NE

E

SE

SW

SW

W

W

NE

NE

E

E

SE

SE

SW

W

NE

E

SE

Except for samples collected west from the pollution source, distribution of Mn was approxi‐ mately uniform throughout the soil profile, the concentration ranging between 942.32 mg/kg and 1578.64 mg/kg at 5-20 cm depth, and between 796.68 and 1631.13 mg/kg at 20-40 cm depth (Figure 13). The surface layer showed a low correlation between the Mn concentrations and

Figure 11. Cobalt vertical distribution in soil and correlation with pH Nickel concentration varied along the profile of soil. Much higher values were observed in the surface layer of soil compared to the values representing the concentration of Ni in the middle of the profile. At the bottom of the profile, the concentrations increased slightly (Figure 12). For soil samples collected in the SW direction, the metal concentrations maintained at high value on the entire soil profile compared to other directions. In the W direction, the surface layer showed much higher concentrations of Ni, and in the deeper layers the value of Ni concentration were still high. The correlation between the Ni concentrations in soil and the pH was low, positive and decreased in intensity with the depth

0-5cm 5-20 cm 20-40 cm

6.00 7.00 8.00

R² = 0.2217

was low, positive and decreased in intensity with the depth profile.

R² = 0.0755

6.00 7.00 8.00

correlation (0.2 - 0.4).

25.00

0.00

5.00

10.00

15.00

**Co concentration (mg/kg)**

20.00

profile.

correlation (0.2 - 0.4).

0.00

0.00

50.00

100.00

150.00

200.00

250.00

300.00

50.00

100.00

150.00

**Pb concentration (mg/kg)**

**Pb concentration (mg/kg)**

200.00

R² = 0.4714

6.00 7.00 8.00

6.00 7.00 8.00

**Figure 10.** Lead vertical distribution in soil and correlation with pH

R² = 0.4714

**Figure 9.** Tin vertical distribution in soil and correlation with pH

250.00

300.00

0.00

20.00

40.00

60.00

**Sn concentration (mg/kg)**

80.00

100.00

120.00

R² = 0.0003

276 Environmental Risk Assessment of Soil Contamination

6.00 7.00 8.00

1000.00 1500.00 2000.00 **Mn concentration (mg/kg)** SW W NE R² = 0.3893 6.00 7.00 8.00 R² = 0.6073 6.00 7.00 8.00 The soils in Zone II showed similar values of Cr concentration on the entire soil profile, observing only a slight increase in the median layer (Figure 14). In the SW and W directions, Cr distribution differed on the soil profile. In the surface layer the concentration had high values, but they decreased with the depth. Only in the surface layer the concentration of Cr in the soil had a strong correlation with pH of soil (> 0.6). 0.00 20.00 40.00 60.00 0-5cm 5-20 cm 20-40 cm E SE 6.00 7.00 8.00

Figure 12. Nickel vertical distribution in soil and correlation with pH

Figure 13. Manganese vertical distribution in soil and correlation with pH

0-5cm 5-20 cm 20-40 cm

concentration of Cr in the soil had a strong correlation with pH of soil (> 0.6).

lower layers had a lower correlation between Mo concentration and pH.

The soils in Zone II showed similar values of Cr concentration on the entire soil profile, observing only a slight increase in the median layer (Figure 14). In the SW and W directions, Cr distribution differed on the soil profile. In the surface layer the concentration had high values, but they decreased with the depth. Only in the surface layer the

E

NE

6.00 7.00 8.00

SE

The Mo concentration varied widely in depth of soil profile (Figure 15). In the SW, NE and SE directions the concentrations decreased significantly in the middle of the profile and remain at the same value at the bottom of it. In the W direction, a higher concentration of Mo (4.94 mg/kg) was found at a depth of 5-20 cm. The best correlation between the Mo concentration in soil and pH was at depth of 5-20 cm, with values > 0.4. The upper and

Figure 12. Nickel vertical distribution in soil and correlation with pH

Figure 13. Manganese vertical distribution in soil and correlation with pH **Figure 13.** Manganese vertical distribution in soil and correlation with pH

The Mo concentration varied widely in depth of soil profile (Figure 15). In the SW, NE and SE directions the concentrations decreased significantly in the middle of the profile and remain at the same value at the bottom of it. In the W direction, a higher concentration of Mo (4.94 mg/kg) was found at a depth of 5-20 cm. The best correlation between the Mo concentration in soil and pH was at depth of 5-20 cm, with values > 0.4. The upper and lower layers had a lower correlation between Mo concentration and pH. The soils in Zone II showed similar values of Cr concentration on the entire soil profile, observing only a slight increase in the median layer (Figure 14). In the SW and W directions, Cr distribution differed on the soil profile. In the surface layer the concentration had high values, but they decreased with the depth. Only in the surface layer the concentration of Cr in the soil had a strong correlation with pH of soil (> 0.6). The Mo concentration varied widely in depth of soil profile (Figure 15). In the SW, NE and SE directions the concentrations decreased significantly in the middle of the profile and remain at the same value at the bottom of it. In the W direction, a higher concentration of Mo

(4.94 mg/kg) was found at a depth of 5-20 cm. The best correlation between the Mo concentration in soil and pH was at depth of 5-20 cm, with values > 0.4. The upper and

lower layers had a lower correlation between Mo concentration and pH.

Figure 14. Chromium vertical distribution in soil and correlation with pH

R² = 0.4282

6.00 7.00 8.00

SW

R² = 0.1598

6.00 7.00 8.00

W

NE

E

SE

Figure 15. Molybdenum vertical distribution in soil and correlation with pH The statistical analysis indicated that the heavy metal concentration in soil is negatively correlated with the depth, as the metal concentration decreased with the increasing of depth (Table 5). The correlation was statistically significant at level lower than 5%. Heavy metal concentration in soil was positively correlated with the pH of soil, with low to moderate intensity, except the Mn concentration which showed a very low negative

0-5cm 5-20 cm 20-40 cm

Table 5. Pearson coefficient of correlation between heavy metal concentrations in soil and depth and pH of soil  **Cu Zn Sn Pb Co Ni Mn Cr Mo Depth** -0.2454 a -0.3469 <sup>a</sup> -0.5965 <sup>a</sup> -0.2588 <sup>a</sup> -0.2907 <sup>a</sup> -0.3879 <sup>a</sup> -0.2639 <sup>c</sup> -0.3277 a -0.3469 c **pH** 0.3796a 0.4171 <sup>a</sup> 0.1554 <sup>b</sup> 0.5066 <sup>a</sup> 0.5675 <sup>c</sup> 0.3991 <sup>a</sup> -0.0995 <sup>c</sup> 0.5007<sup>a</sup> 0.0932<sup>a</sup>

The vertical mobility index (VMI) represents the relative explanation of heavy metal concentration between two underlying layer of soil: between 0-5 cm and 5-20 cm; between 5-20 cm and 20-40 cm (Figure 16). The metal mobility between layers was statistically significant at 95% confidence level. VMI will indicate a very weak mobility of metal at values lower than 20%, weak mobility of metal at values between 20 and 40%, moderate mobility of

25.00 R² = 0.1599 **Figure 14.** Chromium vertical distribution in soil and correlation with pH

6.00 7.00 8.00

concentration.

0.00

5.00

10.00

15.00

**Mo concentration (mg/kg)**

20.00

350.00

ª - p < 0.05; b



*5.4 Vertical mobility index of heavy metals in soil* 

Assessment of Historical Heavy Metal Pollution of Land in the Proximity of Industrial Area of Targoviste, Romania http://dx.doi.org/10.5772/58304 279

Figure 15. Molybdenum vertical distribution in soil and correlation with pH **Figure 15.** Molybdenum vertical distribution in soil and correlation with pH

The Mo concentration varied widely in depth of soil profile (Figure 15). In the SW, NE and SE directions the concentrations decreased significantly in the middle of the profile and remain at the same value at the bottom of it. In the W direction, a higher concentration of Mo (4.94 mg/kg) was found at a depth of 5-20 cm. The best correlation between the Mo concentration in soil and pH was at depth of 5-20 cm, with values > 0.4. The upper and lower layers had a

concentration of Cr in the soil had a strong correlation with pH of soil (> 0.6).

lower layers had a lower correlation between Mo concentration and pH.

The soils in Zone II showed similar values of Cr concentration on the entire soil profile, observing only a slight increase in the median layer (Figure 14). In the SW and W directions, Cr distribution differed on the soil profile. In the surface layer the concentration had high values, but they decreased with the depth. Only in the surface layer the

The Mo concentration varied widely in depth of soil profile (Figure 15). In the SW, NE and SE directions the concentrations decreased significantly in the middle of the profile and remain at the same value at the bottom of it. In the W direction, a higher concentration of Mo (4.94 mg/kg) was found at a depth of 5-20 cm. The best correlation between the Mo concentration in soil and pH was at depth of 5-20 cm, with values > 0.4. The upper and

Figure 13. Manganese vertical distribution in soil and correlation with pH

0-5cm 5-20 cm 20-40 cm

R² = 0.6073

6.00 7.00 8.00

Figure 14. Chromium vertical distribution in soil and correlation with pH

R² = 0.4282

6.00 7.00 8.00

0-5cm 5-20 cm 20-40 cm

Figure 14. Chromium vertical distribution in soil and correlation with pH

0-5cm 5-20 cm 20-40 cm

R² = 0.1202

R² = 0.1202

6.00 7.00 8.00

6.00 7.00 8.00

R² = 0.1557

R² = 0.1557

6.00 7.00 8.00

6.00 7.00 8.00

R² = 0.3893

6.00 7.00 8.00

R² = 0.1598

6.00 7.00 8.00

SW

W

SW

SW

W

NE

E

SE

W

NE

NE

E

E

SE

SE

SW

W

NE

E

SE

Figure 15. Molybdenum vertical distribution in soil and correlation with pH The statistical analysis indicated that the heavy metal concentration in soil is negatively correlated with the depth, as the metal concentration decreased with the increasing of depth (Table 5). The correlation was statistically significant at level lower than 5%. Heavy metal concentration in soil was positively correlated with the pH of soil, with low to moderate intensity, except the Mn concentration which showed a very low negative

0-5cm 5-20 cm 20-40 cm

Table 5. Pearson coefficient of correlation between heavy metal concentrations in soil and depth and pH of soil  **Cu Zn Sn Pb Co Ni Mn Cr Mo Depth** -0.2454 a -0.3469 <sup>a</sup> -0.5965 <sup>a</sup> -0.2588 <sup>a</sup> -0.2907 <sup>a</sup> -0.3879 <sup>a</sup> -0.2639 <sup>c</sup> -0.3277 a -0.3469 c **pH** 0.3796a 0.4171 <sup>a</sup> 0.1554 <sup>b</sup> 0.5066 <sup>a</sup> 0.5675 <sup>c</sup> 0.3991 <sup>a</sup> -0.0995 <sup>c</sup> 0.5007<sup>a</sup> 0.0932<sup>a</sup>

The vertical mobility index (VMI) represents the relative explanation of heavy metal concentration between two underlying layer of soil: between 0-5 cm and 5-20 cm; between 5-20 cm and 20-40 cm (Figure 16). The metal mobility between layers was statistically significant at 95% confidence level. VMI will indicate a very weak mobility of metal at values lower than 20%, weak mobility of metal at values between 20 and 40%, moderate mobility of

concentration.

0.00

5.00

10.00

15.00

**Mo concentration (mg/kg)**

20.00

25.00

0.00

50.00

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00

100.00 150.00 200.00 250.00 300.00 350.00

0.00

500.00

1000.00

1500.00

**Mn concentration (mg/kg)**

2000.00

2500.00

278 Environmental Risk Assessment of Soil Contamination

**Cr concentration (mg/kg)**

**Cr concentration (mg/kg)**

ª - p < 0.05; b



*5.4 Vertical mobility index of heavy metals in soil* 

lower correlation between Mo concentration and pH.

R² = 0.1357

6.00 7.00 8.00

**Figure 13.** Manganese vertical distribution in soil and correlation with pH

R² = 0.7064

R² = 0.7064

6.00 7.00 8.00

6.00 7.00 8.00

R² = 0.1599

**Figure 14.** Chromium vertical distribution in soil and correlation with pH

6.00 7.00 8.00

The statistical analysis indicated that the heavy metal concentration in soil is negatively correlated with the depth, as the metal concentration decreased with the increasing of depth (Table 5). The correlation was statistically significant at level lower than 5%. Heavy metal concentration in soil was positively correlated with the pH of soil, with low to moderate intensity, except the Mn concentration which showed a very low negative concentration. The statistical analysis indicated that the heavy metal concentration in soil is negatively correlated with the depth, as the metal concentration decreased with the increasing of depth (Table 5). The correlation was statistically significant at level lower than 5%. Heavy metal concentration in soil was positively correlated with the pH of soil, with low to moderate intensity, except the Mn concentration which showed a very low negative concentration.


Table 5. Pearson coefficient of correlation between heavy metal concentrations in soil and depth and pH

*5.4 Vertical mobility index of heavy metals in soil*  The vertical mobility index (VMI) represents the relative explanation of heavy metal **Table 5** Pearson coefficient of correlation between heavy metal concentrations in soil and depth and pH of soil

#### concentration between two underlying layer of soil: between 0-5 cm and 5-20 cm; between 5-20 cm and 20-40 cm (Figure 16). The metal mobility between layers was statistically **5.4. Vertical mobility index of heavy metals in soil**

significant at 95% confidence level. VMI will indicate a very weak mobility of metal at values lower than 20%, weak mobility of metal at values between 20 and 40%, moderate mobility of metal at values between 40 and 60%, strong mobility at values between 60 and 80%, and very strong mobility at values higher than 80%. Distribution of Cu in the soil profile was given by the very strong correlation of the concentration of this element in the three layers of soil profile. High values of vertical mobility index were observed between the concentrations of Cu in the two underlying layers, which demonstrated the very high mobility of Cu in the soil, mobility influenced also by the pH. Values of correlation between concentrations at different depths indicated weak Zn mobility The vertical mobility index (VMI) represents the relative explanation of heavy metal concen‐ tration between two underlying layer of soil: between 0-5 cm and 5-20 cm; between 5-20 cm and 20-40 cm (Figure 16). The metal mobility between layers was statistically significant at 95% confidence level. VMI will indicate a very weak mobility of metal at values lower than 20%, weak mobility of metal at values between 20 and 40%, moderate mobility of metal at values between 40 and 60%, strong mobility at values between 60 and 80%, and very strong mobility at values higher than 80%.

on the soil profile to depth of 20 cm and a very strong mobility between 20 and 40 cm. Distribution of Cu in the soil profile was given by the very strong correlation of the concen‐ tration of this element in the three layers of soil profile. High values of vertical mobility index were observed between the concentrations of Cu in the two underlying layers, which demon‐ very strong mobility at values higher than 80%.

strated the very high mobility of Cu in the soil, mobility influenced also by the pH. Values of correlation between concentrations at different depths indicated weak Zn mobility on the soil profile to depth of 20 cm and a very strong mobility between 20 and 40 cm. Distribution of Cu in the soil profile was given by the very strong correlation of the concentration of this element in the three layers of soil profile. High values of vertical mobility index were observed between the concentrations of Cu in the two underlying layers, which demonstrated the very high mobility of Cu in the soil, mobility influenced also by the pH. Values of correlation between concentrations at different depths indicated weak Zn mobility

on the soil profile to depth of 20 cm and a very strong mobility between 20 and 40 cm.

Figure 16. Vertical mobility index (VMI) of heavy metals between the layers of the soil profile, statistically significant at 95% confidence level The mobility index of Sn was different depending on the depth. In the surface layer, **Figure 16.** Vertical mobility index (VMI) of heavy metals between the layers of the soil profile, statistically significant at 95% confidence level

this metal had a weak mobility; the correlation between the two layers (0-5cm and 5-20 cm) was very low. At greater depths, Sn mobility index was higher, indicated by the strong correlation of the concentrations at depths greater than 20 cm. Correlation of Pb concentration between layer of 0-5 cm and the other two layers was very low (<0.3). A strong correlation exists only between 5-20 cm and 20-40 cm depth which indicate a very strong mobility of Pb. The correlation between the concentrations of Co in the soil profile indicated a strong mobility of metal between the surface layer and underlying layers. The correlation between the Ni concentrations of different depths of soil profile is very strong, indicating a very strong mobility of Ni in soil which increased with depth. The correlation between the concentrations of Mn in different depths of the soil profile is very strong, which indicated that a significant increase in the concentration of Mn in the upper layer will lead to an increase of Mn concentration also in the depth due to very strong The mobility index of Sn was different depending on the depth. In the surface layer, this metal had a weak mobility; the correlation between the two layers (0-5cm and 5-20 cm) was very low. At greater depths, Sn mobility index was higher, indicated by the strong correlation of the concentrations at depths greater than 20 cm. Correlation of Pb concentration between layer of 0-5 cm and the other two layers was very low (<0.3). A strong correlation exists only between 5-20 cm and 20-40 cm depth which indicate a very strong mobility of Pb. The correlation between the concentrations of Co in the soil profile indicated a strong mobility of metal between the surface layer and underlying layers. The correlation between the Ni concentra‐ tions of different depths of soil profile is very strong, indicating a very strong mobility of Ni in soil which increased with depth.

mobility of this metal. The correlation between the concentrations of Cr in different depths of soil profile indicated a weak mobility of Cr between the surface layer and the middle layer of soil profile and a very strong mobility in the lower part of the soil profile. Correlations between the Mo concentrations were different on the soil profile: very weak in its upper layer and strong in the lower layers of soil profile. **6. Discussion**  Because of the metallurgical activities carried out in the vicinity of Targoviste, which produced in time significant amounts of particulate matter with a high content of Pb, Cr, Cu, Mn, Ni and Zn, the quality of agricultural soils is negatively influenced by the concentrations of heavy metals, which represent a risk of toxicity to humans. In order to evaluate the degree The correlation between the concentrations of Mn in different depths of the soil profile is very strong, which indicated that a significant increase in the concentration of Mn in the upper layer will lead to an increase of Mn concentration also in the depth due to very strong mobility of this metal. The correlation between the concentrations of Cr in different depths of soil profile indicated a weak mobility of Cr between the surface layer and the middle layer of soil profile and a very strong mobility in the lower part of the soil profile. Correlations between the Mo concentrations were different on the soil profile: very weak in its upper layer and strong in the lower layers of soil profile.
