3.2. Element concentrations in sediments samples

[15, 16]. Mass spectrometry with inductively coupled plasma offers the possibility to measure the rare earths with an excellent accuracy, which cannot be achieved by any another method [17, 18]. In this context, systematic observations correlated with the climatic conditions were performed in this work for a prolonged period. Thus, by comparing the data on a sampling site, in different periods, higher concentrations of La, Ce, and Pr were observed in September. Analyzing data obtained in the 3 years of monitoring (2009, 2010, and 2011) for the same sampling month, a constancy of the rare metal concentrations was revealed, except for Sc, which recorded a significant decrease in 2009 (Table 4). Determination of trace amounts of rare earth elements dissolved in water was correlated with their concentration in the soil; concentrations of rare metals can originate from the soils adjacent to waters that once washed by rainfalls reach these waters. Quality of surface water and sediments, in terms of chemical species concentrations of the metals, was discussed based on the results obtained for the

Sampling area/concentration (µg L−<sup>1</sup>

2009 2010 2011 2009 2010 2011 2009 2010 2011 2009 2010 2011

Area 8 Area 7 Area 5 Area 6

Sc 2.686 0.693 0.428 1.493 0.862 0.403 1.680 0.817 0.423 2.515 0.842 0.429 Y 0.033 0.056 0.035 0.028 0.058 0.031 0.017 0.065 0.030 0.065 0.064 0.034 La 0.037 0.036 0.057 0.025 0.047 0.02 0.019 0.037 0.052 0.082 0.038 0.036 Ce 0.073 0.103 0.047 0.029 0.053 0.012 0.038 0.069 0.07 0.142 0.041 0.093 Pr 0.017 0.009 0.018 0.005 0.008 0.005 0.004 0.011 0.014 0.023 0.010 0.01 Nd 0.039 0.056 0.03 0.016 0.032 0.011 0.013 0.039 0.047 0.090 0.045 0.046 Sm 0.013 <0.001 0.005 0.004 0.003 <0.001 0.003 0.007 <0.001 0.020 0.001 <0.001 Eu 0.002 0.001 0.002 0.003 0.002 <0.001 0.004 0.003 <0.001 0.009 0.004 <0.001 Gd 0.009 0.012 0.007 0.005 0.007 0.002 0.003 0.014 0.007 0.018 0.009 0.014 Tb 0.002 0.001 0.002 0.001 0.002 0.003 0.001 0.002 0.002 0.004 0.003 0.002 Dy 0.005 0.010 0.005 0.006 0.010 <0.001 0.002 0.004 0.005 0.018 0.012 0.003 Ho 0.001 0.002 0.001 0.001 0.003 <0.001 0.001 0.003 0.003 0.003 0.002 0.002 Er 0.003 0.004 <0.001 0.002 0.005 <0.001 0.001 0.008 <0.001 0.010 0.007 <0.001 Tm 0.001 0.001 0.001 <0.001 0.002 <0.001 0.001 0.001 0.001 0.002 0.001 0.003 Yb 0.001 0.005 <0.001 0.002 0.003 <0.001 <0.001 0.004 <0.001 0.008 0.004 <0.001 Lu <0.001 <0.001 0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 0.001 <0.001 <0.001 Th 0.022 0.013 0.057 0.028 0.010 0.02 0.020 0.010 0.052 0.027 0.033 0.036

Table 4. Comparative situation of the rare metal concentrations during the monitoring campaign.

)

surface water and sediment analyzed samples taken from locations.

Elements

276 Water Quality

Valuable data regarding the distribution of pollutants in sediment [19–22] were published in recent years. However, there is a limited analysis of the sedimentological characteristics on the pollutant distribution, which can play a key role in distinguishing the different sources, transport processes, and conservation status of specific contaminants in the environment. All the physicochemical and biochemical processes in aquatic systems take place at interfaces water‐atmosphere‐lithosphere, and a particularly important role is assigned to chemical and biochemical reactions at the water‐sediment interface, which adjust the composition of natural waters. Studying the influence of physicochemical factors on the distribution of metals in sediments and water is important when the retention of metals by various types of sediments is assessed, developing thus predictions that may assure data comparison, interpretation, and their extrapolation, as an important contribution to the sustainable management of the investigated area.

Trace elements are one of the main sources of pollution of the aquatic chain. Since they tend to be adsorbed in sediment, the study of the adsorption/desorption of heavy metals in sediment and the effect of sediment transport are of particular importance. Sediments from lakes are an excellent witness of the water quality since they preserve important information on the environment and are recognized as a source of contaminants in aquatic systems due to the local physicochemical conditions. It is worth mentioning that the sediments are the best environment for toxic metals due to their high absorption capacity; therefore, sediment plays an important role in storing and releasing metals.

Correlations of climatic factors with the sampling locations were performed in relation to pollution sources. The most important factor in determining the concentration values of chemical species of the pollutant metal proved to be the location of the sampling point relative to the anthropogenic sources of pollution. A correlation was also found between the concentrations values of chemical species of the metal and the climatic factors registered during the monitoring period. As shown in Table 5, the concentration values for the most elements (Cd, Cu, Pb, Hg, and Zn) in sediment samples collected from the study area are within the permissible limits.

Based on the analysis of experimental data, it can be concluded that there is a match between the total concentrations of chemical species of the metals studied in samples of surface water and sediments collected from the same locations. Possible transfers of metal compounds in both directions may occur, from the sediment into the surface water and vice versa.

The levels for most metals in sediment samples collected from the study area generally were within the limits of admissibility, except for As present in quantities that exceeded the mean admitted values (sediments sampled in 2010 from the Areas 2 and 5). The average concentrations of some metals such as As, Pb, Co, U, and Cd were higher in the dry season than in the wet season. This is possible due to the dilution by rainwater influencing the concentration and mobility of heavy metal. In contrast, the mean concentration of Fe in sediment samples taken from the driest month was lower than concentrations in samples collected within the wet


period, probably due to the rainfall. Higher values of metal concentrations were found in sediments taken from lakes versus those sampled from rivers.

Table 5. Metal concentrations in the analyzed sediment samples.

The predominance of metals in the free ionic form and as soluble compounds in water, in an acidic environment, favors both the exchange processes at the water‐sediment interface and the bioabsorbtion processes with direct consequence on the toxicity of these metals. Hence, appears obvious the need to study the distribution of the metals contained in the sludge fractions where the metals are attached in combination with different abilities of participating to the heterogeneous equilibrium sediment‐aqueous phase.

Thus, to study the heterogeneous equilibrium occurring at the water‐sediment interface, the metal concentrations of sediment pore water were determined. The literature presents the calculation mode (Eqs. (1) and (2)) of trace metals distribution in the interstitial sediment‐water interface following the formula:

$$\text{P}\_{\text{sed.}} = (\text{M}\_{\text{s}}/\text{M}\_{\text{t}}) \quad 100 \tag{2}$$

$$\mathbf{P}\_{\text{int.water}} = 100 \mathbf{-P}\_{\text{sech}},\tag{3}$$

where Psed. (%) is the proportion of metal in the sediment, Pint.water (%) is the proportion of the metal in interstitial water, Ms (mg) is the amount of metal in the sediment, Mt (mg) is the total amount of the metal (sediment + interstitial water) in the sample.

Experimental data showed that for the studied metals, the concentrations in pore water samples exceed those in surface water, which suggests that sediment through interstitial water may become a potential source to chemical species mobilization of the metals in water (Table 6). Characterization in terms of rare metal concentrations, comparing water samples with water resulting after settling sediment, revealed that the sediments accumulate rare metals (the concentrations both in water and in sediment are very low, but there is a slight increase in sediment). It was also highlighted that sediment accumulates a larger amount of rare earth metals than soils.


Table 6. Trace element concentration in water/water from sediment, year 2011.

### 3.3. Metal concentrations in soil samples

period, probably due to the rainfall. Higher values of metal concentrations were found in

As/17 mg kg−<sup>1</sup> March 17.33 16.53 14.66 11.23 111.39 12.91 21.75 20.17

Cd/3.5 mg kg−<sup>1</sup> March 0.16 0.11 0.07 0.10 0.12 0.15 1.12 0.96

Cr/90 mg kg−<sup>1</sup> March 11.95 20.55 19.38 21.13 39.02 18.59 20.75 19.12

Cu/200 mg kg−<sup>1</sup> March 11.03 10.62 9.91 10.59 20.08 11.21 11.65 10.15

Pb/90 mg kg−<sup>1</sup> March 40.24 33.56 39.81 25.78 26.15 20.96 21.17 21.76

Hg/0.5 mg kg-1 March <0.001 0.07 0.12 <0.001 0.09 <0.001 <0.001 <0.001

Zn/300 mg kg−<sup>1</sup> March 51.41 44.35 53.09 50.17 42.63 31.59 50.19 30.20

Sampling area/concentration (mg kg-1)

Month Area 1 Area 2 Area 3 Area 4 Area 5 Area 6 Area 7 Area 8

May 35.43 34.69 55.95 19.41 133.79 51.06 76.34 48.22 July 20.15 22.37 55.93 28.28 26.78 26.30 87.48 80.34 September 19.07 25.43 35.78 36.12 172.32 159.34 169.63 34.49

May 0.35 0.32 0.41 0.22 0.16 0.56 1.65 0.13 July 0.10 0.14 0.25 0.15 0.12 0.15 2.97 1.54 September 0.08 0.12 0.15 0.20 0.38 0.36 0.31 0.26

May 31.23 36.74 42.56 82.38 44.24 88.55 72.90 32.28 July 16.40 16.57 16.39 71.97 60.19 21.84 61.04 60.34 September 11.19 32.92 49.64 53.23 102.47 91.17 89.18 35.83

May 25.41 24.16 27.71 47.66 27.81 60.78 66.97 17.93 July 10.29 11.62 14.30 41.52 30.23 17.76 85.25 80.56 September 10.26 17.53 25.38 40.54 54.80 52.78 49.90 16.50

May 39.27 39.77 39.87 13.14 13.78 20.12 22.24 22.60 July 19.56 18.43 17.03 8.41 8.23 19.29 24.28 24.18 September 17.54 17.13 27.44 25.43 23.53 22.93 22.92 26.80

May <0.001 0.28 0.18 0.03 <0.001 <0.001 0.15 0.12 July 0.01 0.01 <0.001 <0.001 <0.001 0.08 0.09 <0.001 September 0.07 0.04 0.17 0.19 0.24 0.20 0.11 0.07

May 81.56 79.43 86.77 80.40 51.30 85.03 167.01 66.27 July 42.71 46.64 57.63 64.72 63.12 54.76 193.75 190.82 September 62.76 64.44 81.60 90.53 103.85 98.82 96.48 134.67

The predominance of metals in the free ionic form and as soluble compounds in water, in an acidic environment, favors both the exchange processes at the water‐sediment interface and the bioabsorbtion processes with direct consequence on the toxicity of these metals. Hence,

Table 5. Metal concentrations in the analyzed sediment samples.

sediments taken from lakes versus those sampled from rivers.

Elements/permissible limits [23]

278 Water Quality

The catchment of Somes River fits in the temperate continental area, the bioclimatic conditions in the area causing a moderately active or slow biological circuit, and a strong acidification of soils. Soil research and its quality assessment closely related to the dynamic use of land offer many possibilities in terms of approach. Chemical characteristics of the soil and organic carbon content, pH, the oxides forms, carbonates, and some physical properties such as clay content may influence the concentration of chemical elements.

This work has also proposed an assessment of heavy metals distribution in soils in the studied areas and an investigation of the extent to which heavy metal content in soil from the areas of waters accumulation may influence their concentration in water. Table 7 highlights the concentrations of toxic elements in soils versus the limit values according to the Romanian laws [24].


NV, normal values; TA, threshold alert; IT, intervention threshold [24].

Table 7. Heavy metal concentrations in soil samples collected in May 2011, in different areas.

Cd in soil ranged from relatively narrow limits (0.19–1.95 mg kg−<sup>1</sup> ), with an overwhelming dominance (>99%) of the contents lower than the alarm threshold. It can be considered as representative for the natural geochemical background of the investigated area. These abundances are consistent with the geological structure, relatively uniform, which is determined by sedimentary rocks, which are known for their low content in Cd. An exceeding of the normal values was observed to Area 4 (Somes Cald Lake), but below the alert threshold.

Mn content is between relatively wide limits (120–1100 mg kg−<sup>1</sup> ), with a similar distribution to that described by the normal distribution law. Therefore, 99.90% of the samples were below the maximum content of normal, and only 0.10% of the samples exceed the normal range, but not the alert threshold. The monitoring carried out on soil during year 2011 revealed an exceeding of normal values in almost all areas, but below the alert threshold.

Chromium is considered as one of the most harmful metals for human health. In aquatic environment, it is presented as Cr3+ ion as well as anionic species and CrO4 <sup>4</sup><sup>−</sup> si Cr2O7 2 , these two forms being produced by human activities. The values determined for Cr and Ni in the soils of the studied areas fluctuate in the range between 12.1 and 86.0 mg kg−<sup>1</sup> (for Cr) and 17.0–70.0 mg kg−<sup>1</sup> (for Ni), with exceedings of normal values without reaching the alert threshold.

many possibilities in terms of approach. Chemical characteristics of the soil and organic carbon content, pH, the oxides forms, carbonates, and some physical properties such as clay content

This work has also proposed an assessment of heavy metals distribution in soils in the studied areas and an investigation of the extent to which heavy metal content in soil from the areas of waters accumulation may influence their concentration in water. Table 7 highlights the concentrations of toxic elements in soils versus the limit values according to the Romanian

Area 1 37.46 33.59 99.23 0.45 43.91 37.05 249.73 Area 2 16.70 31.76 62.43 0.19 24.23 28.55 264.95 Area 3 11.14 22.81 44.37 0.12 14.95 23.81 151.71 Area 4 52.92 75.30 382.66 1.95 38.75 52.93 1027.20 Area 5 37.85 23.52 65.18 0.25 45.94 55.39 534.97 Area 6 58.72 26.50 85.57 0.97 53.84 63.55 807.63 Area 7 42.77 17.31 102.40 0.89 57.18 33.87 513.54 Area 8 71.07 22.59 77.05 0.22 19.57 30.26 207.05 NV 20 20 100 1 20 30 900 TA 100 50 300 3 75 100 1500 IT 200 100 600 5 150 300 2500

Metal concentrations (mg kg−<sup>1</sup>

Cu Pb Zn Cd Ni Cr Mn

)

may influence the concentration of chemical elements.

Cd in soil ranged from relatively narrow limits (0.19–1.95 mg kg−<sup>1</sup>

Table 7. Heavy metal concentrations in soil samples collected in May 2011, in different areas.

NV, normal values; TA, threshold alert; IT, intervention threshold [24].

Mn content is between relatively wide limits (120–1100 mg kg−<sup>1</sup>

values was observed to Area 4 (Somes Cald Lake), but below the alert threshold.

exceeding of normal values in almost all areas, but below the alert threshold.

environment, it is presented as Cr3+ ion as well as anionic species and CrO4

dominance (>99%) of the contents lower than the alarm threshold. It can be considered as representative for the natural geochemical background of the investigated area. These abundances are consistent with the geological structure, relatively uniform, which is determined by sedimentary rocks, which are known for their low content in Cd. An exceeding of the normal

that described by the normal distribution law. Therefore, 99.90% of the samples were below the maximum content of normal, and only 0.10% of the samples exceed the normal range, but not the alert threshold. The monitoring carried out on soil during year 2011 revealed an

Chromium is considered as one of the most harmful metals for human health. In aquatic

), with an overwhelming

), with a similar distribution to

<sup>4</sup><sup>−</sup> si Cr2O7

2 , these

laws [24].

280 Water Quality

Area

Pb ranges from relatively low limits of 20–80.4 mg kg−<sup>1</sup> . Most samples showed an exceeding of lead concentrations than normal, except for samples collected from Somes Cald Lake where values above the alert threshold were reported. This clearly reflects the effects of human intervention in this area.

Zn content determined in 2011 on the analyzed soils varies widely (26–146 mg kg−<sup>1</sup> ) with a significant dominance (>95%) of the contents, not exceeding normal values for soils. In the Area 4 (Somes Cald Lake), Zn anomalies are spatially overlapping, largely over the Pb, suggesting the same originating polluting sources.

Comparing the content of heavy metals in soil and water samples to each sampling point, it can assert that there is a correlation only in certain areas (e.g., Al, Zn, Ti, and Pb for Area 1), where the concentrations of metals in water samples may result from soil washing during rainfall. Here are the results obtained for soil samples collected in different months (Table 8 ): in March, the highest concentrations recorded for Pb (Areas 1, 2, 3, 5), Cu, Co, Cr (Area 2), Zn (Areas 2, 7, 8), and Mn (Areas 1, 5); in May, for Zn (Area 4), Ni (Area 7); in July, for As (Areas 2, 3, 4, 5, 7), Cu (Areas 4, 7, 8), Pb, Cr, Mn, and Co (Area 7), Zn (Area 4); and in September, for As (Areas 1, 6, 8), Cu, Ni, Cr, Zn (Areas 1, 3, 5, 6), Co (Areas 6, 7), and Mn (Areas 2, 3, 4).

Following the values obtained for samples of soil taken from the same area, in different years, a growing trend 2009–2011 in the concentrations of Pb, As, Ni, Zn, Co, and Cu, was observed (Table 9).
