Heavy metals in overbank sediments
CADMIUM. This heavy metal occurs in contents higher than the maximum permissible value allows (6.4 mg / kg, (Official Gazette of the RS 2012) in sediments found in the Rudnjačka river basin (Lisinska River - 7.5 mg / kg). The contents higher than target value allows (0.8 mg/kg, (Official Gazette of the RS 2012)) can be found in sediments from Gajovska and Kaznovićka rivers, in Jošanica river basin (maximum value obtained for Samokovka river), Maglašnica, Planska River II, and in Rudnjačka river basin (Rudnica). Somewhat lower contents, but still higher than the target value, were found in Raška river basin (Dramićki Stream), and in the sediments from Ibar I and II and Pavlićka River. The contents below the detection limit of the used method were found in sediments from the Raška river basin (Ljudska River I, II, and II), Raška (I and II), Đurićka, Šaronjska and Deževska River I and II, and Nosoljinska River. The content of Cd in half of the sediment samples was between 0.29 mg/kg and 0.53 mg/kg (Fig.4).
COPPER. This heavy metal occurs in contents extremely higher than the maximum permissible value allows (110 mg/kg, (Official Gazette of the RS 2012)) in Rudnjačka river basin (Lisinska River – 865.50 mg/kg), Raška river basin (Kosurička River and slightly lower content in Ljudska River V), Jošanica river basin (Samokovka), Brvenica river basin (Andrićka River, Vrani Stream and Borićka River, and slightly lower content in Jablanovićka, Kruševićka, and Gradačka rivers). Content higher than the target value (36 mg/kg, (Official Gazette of the RS 2012)), but lower than maximum permissible value was discovered in Raška river basin (Dramićki Stream, Nosoljinska River, Trnavska River, Sebimiljska River, Brezovačka River, Raška III and V, Trnavska River I and III, Izbička River, and Jovska River), Brvenica river basin (Klisurski Stream, Brvenica I, Zarički Stream), Studenica river basin (Raduše I, Brevina), Kaznovićka River, Jošanica river basin (Jošanica III, Planska River I, Gobeljska River, Lužnjanski Stream, Veleštica), Rudnjačka river basin (Rudnica), Gokčanica river basin (Zastupski Stream), Popova River, Planska River II, Maglašnica, Pavlićka River, and Ibar II sediments. The content of Cu in half of the sediment samples was in the range from 28.7 mg / kg to 83.8 mg / kg (Fig. 4).
COBALT. This heavy metal is not included in the regulation that defines the limit of concentrations in sediments in Serbia (Official Gazette of the RS 2012). However, due to its high toxicity, it was included in this paper. The extremely high concentrations were discovered in the Krivačka and Raška (Rečica) river basins. High concentrations were found in the Brezanska River, the Brvenica river basin (Klisurski Stream), Gokčanica river basin (Rudnjačka River, Zastupski Stream, and Dubovski Stream), Popova River, and Pivnica. The content of cobalt in half of the sediment samples was in the range from18 mg/kg to 56 mg/kg (Fig. 4).
CHROMIUM. This heavy metal was found in extremely high concentrations in sediments from Raška river basin (Rečica) and Krivačka River. Contents higher than the maximum permissible value (240 mg/kg, (Official Gazette of the RS 2012)) was present in sediments from Raška river basin (Nosoljinska River, Tušimska River, Trnavska River I and III, Sebimiljska River, and Jovska River), Brvenica river basin (Jablanovićka River, Andrićka River, Vrani Stream, Borovićka River, Kruševićka River, Gradačka River, Klisurski Stream, Brvenica I and II), Jošanica River basin (Planska River I, Gobeljska River, Veleštica, and Samokovka), Studenica river basin (Brevina and Studenica), Gokčanica river basin (Rudnjačka River, Dubovski Stream, Zastupski Stream, and Gokčanica), and in Kaznovićka, Gajovska, Brezanska, and Popova rivers, Planska River II, Maglašnica, Lopatnica, Pivnica, Ibar I and II, and Ribnica. In concentrations between the target value (100 mg / kg, (Official Gazette of the RS 2012)) and maximum permissible value, chromium occurred in sediments from the Raška river basin (Ljudska River I, III, IV, and V, Dramićki Stream, Đurićka River, Šaronjska River, Deževska River I and II, Raška II and V, Kosurička River, Brezovačka River, Trnavska River I, Izbička River), Brvenica river basin (Lučka River and Zarički Stream), Studenica river basin (Raduša I and II), and Jošanica river basin (Gobeljska River). The content of chromium in half of the sediment samples was higher than the target value and it ranged from 111 mg / kg to 675 mg / kg (Fig. 4).
MERCURY. The maximum concentration for mercury (1.4 mg/kg) was found in the sediments from Maglašnica. In the range above the target value (0.3 mg / kg, (Official Gazette of the RS 2012)) and lower than maximum permissible value (1.6 mg / kg, (Official Gazette of the RS 2012)), it was discovered in the sediments of the Brvenica river basin (Andrićka River, Jablanovićka River, Brvenica I and II, and Zarički Stream), Jarandolski Stream, Gajovska River, Maglašnica, and Kneževićki Stream. The contents below the detection limit of the used method were found in sediments from the Raška river basin (Šaronjska River, Deževska River I and II, Nosoljinska River, Raška II, Kosurička River, Trnavska River, and Izbička River), Brvenica river basin (Klisurski Stream), Studenica river basin (Brevina), Jošanica river basin (Lužnjanski Stream and Veleštica), Rudnjačka river basin (Lisinska River), Gokčanica river basin (Dubovski Stream, Zastupski Stream, and Gokčanica), and in the Krivačka and Popova rivers, Planska River II, Lopatnica, Pivnica, Vrški Stream, Pavlićka River, Kneževićki Stream, Ibar I and II, and Ribnica (Fig. 4).
MANGANESE. This heavy metal was not included in the regulation on limit values for pollutants (Official Gazette of the RS 2012). The literature suggested that the content from 1,500 to 3,000 mg/kg can be toxic (Kabata-Pendias and Pendias 1984). It can be mobilized into the soil from the sediment. These high contents were found in the Raška river basin (Dramićki Stream, Tušminska River, and Jovski Stream), Brvenica river basin (Vrani Stream and Borovića River), Studenica river basin (Brevina), Jošanica river basin (Jošanica II and Lužnjaski Stream), Rudnjačka river basin (Lisinska River) and in Kaznovića River, Krivačka River, Planska River I and II, and Maglašnica. The content of this metal in half of the sediment samples was in the range from 929.90 mg / kg to 1,312.40 mg / kg (Fig. 4).
NICKEL. The samples from Raška river Basin (Raška IV) and Vrški Stream had contents of nickel lower than the target value (35 mg/kg, (Official Gazette of the RS 2012)). Samples obtained from Raška river basin (Ljudska River I, II, and III, Raška I, II, and IV, Kuzmićka River, Sebečevska River, and Trnavska River) and Rudnjačka river basin (Lisinska River) had nickel concentrations in the range between the target values and maximum permissible values (44 mg/kg, (Official Gazette of the RS 2012)). Extreme values for nickel were recorded in sediments from the Brvenica river basin (Klisurski Stream), Pivnica, Raška river basin (Rečica), and Gokčanica river basin (Rudnjačka River). The concentrations of the rest of the samples were higher than the maximum permissible value. The content of nickel in half of the sediment samples was significantly higher than the maximum permissible value and it was in the range from 63.3 mg/kg to 682.6 mg/kg (Fig. 4).
LEAD. The contents higher than maximum permissible value (310 mg / kg, (Official Gazette of the RS 2012)) was found in sediments from Jošanica river basin (Samokovka), Gokčanica (Zastupski Stream and Gokčanica), and in Gajovska and Kaznovićka Rivers. The contents between the target value and maximum permissible value was discovered in sediments from Raška river basin (Kuzmićka River and Deževska River I), Jošanica river basin (Jošanica III and Veleštica), Rudnjačka river basin (Rudnica), and in Krivačka River, Planska River II, Maglašnica, Vrški Stream, Pavlićka River, and Ibar I and II. The rest of the sediment samples had the lead content lower than the target value. The content of lead in half of the samples was lower than the target value and it was in the range from 36.80 mg/kg to 79.00 mg/kg (fig.4).
ZINC. The contents of zinc higher than maximum permissible value (430 mg/kg, (Official Gazette of the RS 2012)) were found in the sediments from Kaznovićka River, Jošanica river basin (Samokovka), Gajovska River, and Maglašnica. The concentration between the target value (140 mg/kg, (Official Gazette of the RS 2012)) and maximum permissible value was discovered in the sediments from Raška river basin (Dramićki Stream, Kuzmićka River, and Kosurička River), Rudnjačka river basin (Rudnica and Lisinska River), Gokčanica river basin (Zastupski Stream and Gokčanica), Planska River II, Lopatnica, Pavlićka River, and Ibar I and II. In other sediment samples the concentrations were lower than the target value. The content of zinc in half of the samples was below the target value and it ranged from 81.5 mg/kg to 127.5 mg/kg (Fig. 4).
ARSENIC. The extremely high concentrations of arsenic were discovered in the sediments from Gajovska River, Rudnjačka river basin (Samokovka), Kaznovićka River, Maglašnica, Pavlićka River, Gokčanica river basin (Dubovski Stream and Zastupski Stream), and Planska River II. The contents of As between target value (29 mg/kg, (Official Gazette of the RS 2012)) and maximum permissible value (42 mg / kg, (Official Gazette of the RS 2012)) was found in sediments from the Raška river basin (Dramićki Stream, Deževska River I, and Jarandolski Stream), Jošanica river basin (Jošanica III and Planska River I), Rudnjačka river basin (Rudnica), and Gokčanica river basin (Zastupski Stream and Gokčanica). In other sediments the content of arsenic was lower than the target value. The content of arsenic in half of the sediment samples ranged from 15.3 mg/kg to 38.4 mg/kg (Fig.4).
Cadmium and mercury were below detection limit of the used method; cadmium in the overbank sediments from Ljudska River I, II, III, and IV, Raška I, Đurićka River, Šaronjska River, Deževska River I and II, Nosoljinska River, and Pivnica; and mercury in the sediments from Ibar and Ribnica, Šaronjska River, Deževska River I and II, Nosoljinska River, Raška River, Kosurička River, Klisurički Stream, Trnovska River, Brevina, Izbička River, Lužnjanski Stream, Veleštica, Lisinska River, Dubovski Stream, Zastupski Stream, Gokčanica, Krivačka River, Popova River, Planska River, Lopatnica, Pivnica, Vrški Stream, and Pavlićka River.
Factor analysis
Based on the obtained level of significance and visual review of the histogram for all 10 elements, it was determined that the assumption of normality of distribution could not accepted.
Based on the obtained level of significance and visual review of histogram, the Ln variables for transformation values showed that the assumption of the normality of distribution could not be accepted for any of the tested heavy metals.
Table 5 shows the values of Spearman’s rank correlation for the analyzed heavy metals.
EXPLORATORY factor analysis on Ln transformation values by the extraction method determined that the examined heavy metals in overbank sediments were grouped around two synthetic factors and that they defined 63.91% of the variance.
Based on the filling factor estimation matrix, it was determined that Cd, Zn, As, Pb, and Cu were concentrated around the first synthetic factor, and Ni, Cr, and Co around the second factor.
CONFIRMATORY factor analysis confirmed that 68.96% of the variance could be explained by factor 1, and 95.16% by factor 2.
FACTOR 1. Table 6 shows the significance of correlation between the elements (Cd, Zn, As, Pb, and Cu) concentrated around FACTOR 1.
Moderate positive correlation numerical values of Spearman’s rank correlation coefficient were obtained for Cd/Zn 0.635, Cd/-As 0.607, Cd/Pb 0.566, Zn/As 0.637, Zn/Pb 0.690, and As/Pb 0.655. Weak positive correlations were obtained for Zn/Cu 0.212, As/Cu 0.149, Pb/Cu 0.049, and Cd/Cu 0.093 (Table 5).
Table 7 shows the surface distribution of element concentrations grouped around factor 1.
FACTOR 2. Table 8 shows the significance of correlation between the elements (Ni, Cr, and Co) concentrated around FACTOR 2.
The obtained numerical values of Spearman’s rank correlation coefficient were in the excellent correlation range; Ni/Cr 0.952, Ni/Co 0.946, Co/Cr 0.910 (Table 5).
Table 9 shows the surface distribution of element concentrations grouped around factor 2.
The quality of water in the Ibar River has improved from Raška to Kraljevo. Increased concentrations of heavy metals in the sediments of other watercourses have occurred due to the geological and pedological stratum underneath them.
Factor analysis identified two synthetic factors around which the analyzed heavy metals were grouped and further formed geochemical associations. Factor 1 explained 68.96% of the variance. Cd-Zn-As-Pb-Cu were concentrated around factor 1. The increased content of these elements occurred in northern and northeastern tributaries of Ibar. Extremely high contents were found in watercourses where occurrence and deposits of these heavy metals were already confirmed. The contents of Cd, As, and Cu were extremely high in the Rudnjačka river basin. The contents of Zn and Pb were high in the Jošanica river basin. The Gokčanica river basin had high contents of As and Pb, and Gajovska and Kaznovićka rivers had Zn, As, and Pb. The concentrations of Zn and As were increased in the Maglašnica river basin, and As content was increased in Pavlićka and Planska River II. The increased concentrations of Cu were only found in the Raška and Brvenica river basins.
Factor 2 was substantive and it defined 95.16% of the variance. Ni-Cr-Co were grouped around factor 2. The high concentrations of these elements were present in almost all analyzed sediments, they were only slightly less present in southwestern tributaries of Ibar. This geochemical association was typical for this geological environment, i.e. ophiolites.
The analysis determined that heavy metals were grouped around these two factors based on similar geochemical behavior and that they actually represented geochemical associations. These geochemical associations were directly dependent on the environment lithology in which watercourses (or smaller basins) were formed and, to a lesser extent, on the immediate sampling environment. This was mostly minimized by the anthropogenic factor as a condition for the formation of these geochemical associations.