Impact of Historical Mining and Metallurgical Technologies on Soil and Sediment Composition Along the Ibar River

Abstract

This study systematically investigates soil and stream sediment along the 165 km Ibar River to examine the origin and transfer of pollutants. The research focuses on the environmental impact of long-term mining and irregular waste management, as well as natural enrichment related to weathering processes. A comprehensive sampling campaign was conducted, collecting 70 samples from 14 locations. At each location, samples of river sediment, floodplain soil (0–5 cm and 20–30 cm depths), and river terrace soil (same depths) were collected. The contents of 21 elements (Ag, Al, As, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, Sr, V, and Zn) were determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). Analysis of Variance (ANOVA) was performed to identify statistically significant differences in element contents between defined zones, sampled materials (river sediments, floodplain soils, and river terrace soils), and sampled soil horizons (topsoil, 0–5 cm, and subsoil, 20–30 cm). Multivariate analysis, including correlation coefficient, cluster analysis, and principal component analysis, revealed two distinct groups of elements with highly significant correlation coefficients (r > 0.7). The first group, comprising Ag, As, Cd, Cu, Mn, and Zn, indicates anthropogenic enrichment, likely resulting from mining and smelting activities in the middle flow of the Ibar River (The Mining and Metallurgical Complex Trepča). The second group, consisting of Cr, Mg, and Ni, suggests enrichment related to the weathering of elements from the ophiolite zone in the lower Ibar River. The study found high enrichment ratios of toxic elements like arsenic, cadmium, lead, and zinc, particularly in stream sediments and floodplains. Notably, arsenic contents exceeded European averages by up to 57 times in stream sediments, posing a significant environmental concern due to its high content.

1. Introduction

The global increase in a series of human interventions along rivers, such as rapid urbanisation, industrialisation, agriculture, mining, energy production, etc., is the main cause of increased sedimentation but has also intensified the accumulation of toxic metals (TMs) and other anthropogenic compounds [1,2,3,4,5,6,7]. When TMs enter the water, they tend to accumulate in bottom sediments, which act as a repository for various pollutants [8]. Changes in environmental conditions can trigger the release of these TMs from the sediments into the water body through processes such as diffusion and desorption, effectively transforming the sediments into a secondary source of contamination [9,10]. Sediments maintain environmental information about the catchment area at the same time and are recognised as carriers and sources of contaminants [11,12], while the floodplain sediments serve as an archive of their historical composition [10,13,14].

Mineral extraction in the river catchment has resulted in toxic metal contamination in sediment, impacting the entire water ecosystem and the surrounding soil [5,15,16,17,18]. The contamination poses significant environmental challenges, affecting both local ecosystems and the quality of water available for various uses. Efforts to address these contamination issues are crucial for improving the overall health of the river and the surrounding communities that rely on its resources. Due to their substantial, persistent, highly toxic nature and their resistance to biodegradation, TMs have been the leading subject in many research and studies globally [3,19,20,21,22,23,24].

Toxic metals and other elements in fluvial systems are washed away from their sites of origin and, based on particle size, can be transported and sorted over several hundred kilometres downstream [13,25]. Consequently, the contents of TMs in sediment serve as indicators of human impact on environmental monitoring programmes within the catchment area [26,27]. The behaviour of these elements depends on the soil’s physicochemical properties, such as pH, organic matter content (OM), soil texture, cation exchange capacity (CEC), and the distribution of the chemicals among the various soil fractions [12,28]. TM contamination causes soil fertility degradation and crop yield reduction but consequently raises significant risks for food safety and human health through biomagnification [21,23,29,30].

The effects of long-term mining and inadequate waste management are evident along the Ibar River catchment, contaminating floodplain agricultural soils [31]. The Trepča lead-zinc smelter has had a significant impact, particularly around Kosovska Mitrovica, causing extensive topsoil contamination [32,33]. Furthermore, toxic metals released from the flotation tailings have degraded the water and sediment quality of the Ibar’s tributaries, the Drenica River [34], and the Gračanica River [35]. The ecological status and water quality at the monitoring station “Raška” suggest the impact of mining and industrial wastewater, as well as leachate from flotation tailings and metallurgical waste dumps [31,32,33,34,35,36]. A particularly significant area of impact is between Raška and Kosovska Mitrovica, where there are nine lead and zinc mines, three flotation plants, two metallurgy facilities, a chemical industry, and a battery factory. Additionally, tailings in Zvečan, Žitkovac, and Leposavić directly contaminate the Ibar River with widespread chemical contamination, constituting a lasting environmental threat [37,38].

The Ibar River is fed by several tributaries, which play an important role in contaminant transport downstream. The tributary Gračanica River flows directly next to Kišnica and Badovci flotation tailings, which contain the byproducts from the flotation process of minerals extracted from the Kišnica, Hajvalija, Badovci, and Artana mines [35]. Another important tributary of the Ibar is the Drenica River, which is primarily polluted by emissions from a nickel refining plant. Furthermore, the Drenica River is also contaminated by urban flows, pollutants from wastewater discharges, and pollutants from agriculture [34]. Historical mining and mining-related activities represent sources of contamination of the Ibar and have a huge impact on the health of living organisms [36]. The Ibar River catchment is reported to be one of the most contaminated areas in the Western Balkans, according to Šajn et al., 2013 [33].

This study aims to achieve several objectives through the use of multivariate factor analysis: (i) to assess the levels and spatial distribution of TMs in the sediments and alluvial soils of the Ibar catchment; (ii) to understand the behaviour of certain specific elements based on their spatial distribution; and (iii) to establish baseline data on the current status of the river, which can be beneficial for other researchers and relevant authorities.

2. Materials and Methods

2.1. Description of Study Area

The Ibar River is 280 km long and belongs to the Black Sea basin (Figure 1). The Ibar has its source under Hajla Mountain in Montenegro, then flows into SW Serbia, moving eastward towards Kosovska Mitrovica in Kosovo and back to Serbia, flowing through a narrow, deeply carved valley before it joins the Zapadna Morava River near Kraljevo [38,39]. The catchment area has a surface of 7945 km², an average flow rate of 32 m³/s, and an annual average amount of water of 1.15 million m³. Flow rates peak during March and April, while the lowest levels typically occur in August and September. The Ibar valley experiences a mainly continental climate, tempered by occasional influences from both Alpine and Mediterranean climates. This results in hot summers with average temperatures around 30 °C and cold winters with an average temperature of about −10 °C [40].

The gorge of Ibar is influenced by heavy erosion conditioned by various geomorphological factors (including steep relief and slopes), geological conditions (the presence of highly erodible rocks), and the lack of vegetation on the cliff hillsides [36]. The river flows through important industrial complexes, providing a water supply and facilitating electricity production [41]. Unfortunately, intensive industrial activities and low environmental standards have contributed to the river being classified as one of the most polluted rivers in this part of Europe [36].

2.2. Land Use

The CORINE land cover (CLC) dataset was obtained from the Copernicus Global Land Service (CGLS) [42]. For this study, it was calculated that almost half of the study area, approximately 48% (3875 km²), is covered with forest. A further 11% (834 km²) is characterised by bushy or herbaceous vegetation with scattered trees. Agricultural regions, including heterogeneous and specific agricultural areas, account for 22% (1781 km²) and 9% (716 km²) of the study area, respectively. Notably, wetlands and waterbodies occupy a relatively small area of 19 km², while mineral extraction and processing sites, including secondary mineral deposits, cover around 23 km².

2.3. Geological Settings

The river Ibar flows through important metallogenic units, spread over the Carpatho-Balkanides and adjacent areas, characterised by specific combinations of minerals and types of ore deposits [43,44,45,46]. One of the units is the so-called “Serbo-Macedonian metallogenic province”, characterised by Pb-Zn deposits formed during an activity of Oligocene-Miocene dacitic to andesitic volcanism. The ores found there can also include elements such as Cu, Sb, Au, Ag, As, Tl, Bi, and Fe [47,48]. The Trepča Belt lead-zinc mineralisation, known also as the Kapaonik District [45,49] at northern Kosovo, extends for over 80 km and includes several mines [50]. According to the host rock lithology and mineralisation type, the deposits are subdivided into following groups: (1) skarn to epithermal deposits situated in Triassic shales, intercalated within limestone and marble hosted (Trepča, Ajvalija); (2) epithermal deposits situated in (i) Jurassic medium-grade metamorphic rocks (Crnac, Plakaonica), or listwanite and serpentinite rocks (Crnac, Kišnica, Badovac, Žuta Prlina, Kaluđer), (ii) Senonian limestones and flysch (Belo Brdo, occurrences at Rogozna Mts), or (3) Cenozoic volcanic and volcaniclastics rocks, located predominantly on the Kopaonik [51].

2.4. Lithological Units

The generalised lithological map (according to the geological map SFRJ 1:500,000) [52,53] shows that Palaeozoic metamorphic rocks (including gneisses, leptinolite, biotite schists, sericite-chlorite and epidote-chlorite schists, metasandstone, quartzite, phyllite, marble, calcschist, and metamorphosed quartz conglomerates) are the oldest rocks, covering approximately 12% of the total basin area (Figure 2).

Mesozoic-age rocks, predominantly clastic in the study area (comprising the Diabase–Chert Formation, alevrolite with inclusions of sandstone, limestone, and ophiolitic rocks—ophiolitic mélange, marlstone, claystone, limestone, sandstone, conglomerate, and Volcanogenic-Sedimentary Formation), occupy a substantial portion of the basin. Furthermore, Palaeogene and Neogene-age rocks (sandstone, laminated alevrolite and claystone, lesser conglomerate—flysch, clastic rocks, pelites, and carbonates with pyroclastics) cover nearly 40% of the basin.

Carbonate rocks (limestones and dolomites) of Mesozoic age account for about 10% of the area. Jurassic-age serpentinites and serpentinised peridotites are grouped into a distinct cartographic unit due to their association with Cr-Ni ores, covering approximately 16% of the surface, mainly in the lower reaches of the Ibar River. A notable lithological unit consists of Palaeogene dacite, andesite, and latite with volcanoclastics, as well as Neogene volcanic rocks (quartz latite, dacite, latite, and trachyte). This unit is a significant carrier of polymetallic sulphide ores (Ag, Au, Pb, and Zn) and covers about 15% of the basin area, primarily in the middle river course. The youngest units comprise alluvial sediments and recent river deposits, which are also severely impacted by toxic metal contamination, collectively covering around 9% of the basin area (Figure 2).

2.5. Outcropping Rocks/Outcrops and Mining Activities

Within the area underlain by Jurassic-age serpentinite and serpentinised peridotite, a total of 73 deposits of chromium (Cr) and nickel (Ni) have been identified. In the subsequent significant lithological unit, comprising Palaeogene dacite, andesite, and latite with volcanoclastics, as well as Neogene volcanic rocks (including quartz latite, dacite, latite, and trachyte), 78 occurrences of polymetallic sulphide ores have been documented, primarily hosting silver (Ag), lead (Pb), and zinc (Zn) mineralisation (Figure 3).

2.6. History of Mining and Smelting

The study area is home to the known and important Trepča mining and smelting district, a significant lead-zinc mining region that encompasses the western and southern parts of Mount Kopaonik. Notably, Trepča is one of the largest lead-zinc mines in Europe. The district comprises over 40 mines, with the most prominent being Belo Brdo, Crnac, Žuta Prlina, Koporić, Stari Trg, Novo Brdo, Kišnica, Ajvalija, and Badovac. The Mining and Metallurgical Complex Trepča includes the Pb smelter in Zvečan and the Zn smelter in Kosovska Mitrovica, along with other processing facilities. Between 1931 and 1998, the district’s mineral production totalled 35 million tonnes of ore, yielding 2.2 million tonnes of lead, 1.4 million tonnes of zinc, 4100 tonnes of bismuth, 2600 tonnes of silver, 1700 tonnes of cadmium, and 8.7 tonnes of gold.

As a consequence of mining, processing, and smelting activities, 57 landfills remain, covering a total area of 467 hectares and containing an estimated 104 million tonnes of material [54] (Šajn, 2023). The majority of this material is deposited in flotation tailings at 10 locations, amounting to approximately 64 million tonnes. Significant quantities are also deposited in slag landfills at 8 locations, totalling around 19 million tonnes. Previous research [32,33,39,55] has identified high levels of silver (Ag), arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) in the deposited material. Based on chemical analyses of the material from the secondary mineral deposits [54,56], it has been determined that they contain substantial quantities of various elements, including 1000 tonnes of silver, 320,000 tonnes of arsenic, 57 tonnes of gold, 980 tonnes of cadmium, 36,000 tonnes of copper, 110 tonnes of mercury, 240 tonnes of indium, 450,000 tonnes of lead, 6,400,000 tonnes of sulphur, and 470,000 tonnes of zinc. The deposits are mainly not remediated and scattered throughout the mining area, posing a significant source of contamination.

2.7. Sampling Design

To investigate the state and dynamics of pollutant transfer along the Ibar River, 14 sampling locations were established spanning 165 km, from the confluence of the Ibar and Sitnica rivers to the confluence of the Ibar and West Morava rivers. This represents approximately one location per 12 km of river flow. At each location, samples of stream sediment, floodplain soil at depths of 0–5 cm and 20–30 cm, and river terrace soil at the same depths were collected. The samples were collected during 2011 on the assumption that the stream sediments would reflect recent transport and deposition of pollutants, while the alluvial plains would indicate the place where sediments are trapped and deposited over the years. The river terraces samples were also collected to determine the natural background levels, as it was assumed that these areas had not been impacted by river-transported pollutants (Figure 4). A total of 70 samples were collected. Within the study area, the mid-flow region is situated between sampling locations I-1 and I-7, whereas the lower flow region is between I-8 and I-14.

2.8. Sample Preparation and Chemical Analyses

Soil samples underwent pre-treatment, which included cleaning and drying to a constant mass. As part of the standard sample preparation procedure, the samples were then sieved, milled, and ground to achieve a uniform particle size of 125 µm, ensuring consistency before analytical analysis. The soil and sediment samples were analysed following the international standard ISO 14869-1:2001 [57]. A precisely measured mass of 0.5 g of each sample was placed in Teflon vessels with an accuracy of 0.0001 g. The samples were subjected to acid digestion with 5 mL of concentrated nitric acid, followed by the addition of 5–10 mL of hydrofluoric acid (HF) to facilitate complete digestion of the inorganic components. Once a clear digestion solution had been obtained, 2 mL of perchloric acid (HClO₄) was added to affect the digestion of the organic components. After the vessels had been cooled for 15 min, 2 mL of hydrochloric acid (HCl) was added to dissolve the metal ions. The digests were then quantitatively transferred to 50 mL calibrated flasks. The contents of 20 elements (Ag, Al, As, Ba, Ca, Cd, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, Sr, V, and Zn) were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) using a Varian 715-ES instrument (Model Varian 715 ES, Varian Inc.: Palo Alto, CA, USA). The instrument parameters used were based on those reported by Balabanova et al., 2010 [58].

Quality control was ensured through the analysis of certified reference materials, including soil sample JSAC 0401, rock SARM 3 NIM-L Lujaurite, and rock NCS DC71306 (GBW07114). Recovery rates for the analysed elements were found to range from 98.2% to 100.8%. The standard addition method was also employed, and recovery rates for the analysed elements were determined to range from 90.8% to 109.2%. The results obtained were found to be within the standard deviation of the certified reference materials, thereby confirming the accuracy and reliability of the analytical technique.

3. Data Processing

The Box-Cox transformation is a widely employed data transformation technique in environmental sciences and geosciences [59,60], owing to the frequent occurrence of log-normal distributions [61,62,63] or positive skewness [64] in environmental variables. By applying this transformation, variance stabilisation can be achieved, and non-normal data can be rendered more normal-like, thereby mitigating the effects of similarities between objects and reducing the disparity between extreme values [65]. Consequently, data transformations were performed to normalise the distribution of the dataset.

The basic statistical parameters of the analysed chemical elements were determined for each defined area (

Table 1. Content of chemical elements according to the determined areas and sampling materials.

Area	EU [66,67,68]			Middle River Flow						Lower River Flow
Sampling Material	Stream Sediment	Flood Plains	Topsoil	Stream Sediment		Flood Plains		River Terraces		Stream Sediment		Flood Plains		River Terraces
	X	X	X	XBC	(Min–Max)	XBC	(Min–Max)	XBC	(Min–Max)	XBC	(Min–Max)	XBC	(Min–Max)	XBC	(Min–Max)
Ag (mg/kg)	–	–	0.30	2.6	(1.8–4.0)	2.8	(2.0–5.3)	1.7 1	(1.3–20)	1.3	(1.1–1.8)	1.2	(0.84–1.9)	0.91	(0.54–1.8)
Al (%)	5.2	5.4	5.6	4.6	(3.3–5.5)	3.9	(2.9–5.1)	4.1	(2.4–6.4)	5.3	(3.9–6.5)	5.1	(4.1–6.2)	5.0	(3.8–7.9)
As (mg/kg)	12	10	12	580	(460–700)	250	(140–550)	53	(21–140)	150	(64–240)	73	(47–150)	38	(20–58)
Ba (mg/kg)	420	420	400	320	(280–420)	340	(250–510)	330	(140–760)	290	(210–360)	280	(230–330)	270	(200–420)
Ca (%)	4.2	4.2	2.5	2.9	(2.5–3.7)	1.7	(1.2–2.3)	1.3	(0.2–3.2)	2.8	(1.8–3.6)	2.0	(1.4–2.6)	1.1	(0.26–2.0)
Cd (mg/kg)	0.56	0.53	0.28	13	(8.6–18.2)	8.6	(3.9–23)	1.1 1	(0.65–20)	5.1	(4.0–6.8)	2.8	(1.0–6.9)	1.1	(0.42–1.7)
Cr (mg/kg)	93	93	95	210	(110–310)	200	(99–280)	88	(21–170)	360	(220–560)	370	(190–600)	280	(99–560)
Cu (mg/kg)	25	22	17	81	(54–120)	61	(44–110)	25 1	(18–190)	35	(32–44)	29	(22–56)	23	(16–35)
Fe (mg/kg)	2.5	2.9	2.7	5.2	(4.5–6.3)	4.1	(3.0–5.2)	3.2	(2.3–4.1)	4.6	(4.0–5.4)	4.3	(3.7–5.6)	4.1	(2.8–5.5)
K (%)	1.7	1.7	1.8	1.2	(1.1–1.4)	1.3	(1.1–1.5)	1.5	(1.1–1.9)	1.2	(0.9–1.4)	1.2	(1.0–1.5)	1.2	(0.80–1.7)
Li (mg/kg)	28	30	–	25	(21–30)	25	(21–29)	27	(16–47)	25	(22–39)	25	(22–37)	26	(18–35)
Mg (%)	0.97	1.1	0.71	1.6	(0.9–2.1)	1.7	(0.9–2.5)	0.78	(0.3–1.4)	2.1	(1.7–2.9)	2.4	(1.8–2.9)	1.8	(0.74–2.8)
Mn (mg/kg)	740	870	630	3400	(2300–5900)	1600	(1100–2800)	750	(490–1100)	1300	(1050–1600)	910	(760–1600)	810	(570–1200)
Na (%)	0.79	0.85	0.85	0.84	(0.71–0.96)	0.79	(0.59–0.98)	0.70	(0.33–1.8)	1.1	(0.94–1.3)	1.0	(0.81–1.3)	0.79	(0.61–0.97)
Ni (mg/kg)	35	35	37	200	(100–300)	190	(95–270)	81	(21–160)	310	(150–590)	380	(210–580)	270	(79–640)
P (%)	0.060	0.076	0.066	0.10	(0.077–0.17)	0.061	(0.041–0.081)	0.056	(0.027–0.11)	0.081	(0.052–0.11)	0.054	(0.035–0.083)	0.048	(0.030–0.085)
Pb (mg/kg)	54	39	33	650	(430–1200)	730	(440–1600)	150 1	(110–9300)	190	(150–260)	140	(90–340)	56	(34–97)
Sr (mg/kg)	170	170	130	170	(150–200)	150	(110–210)	130	(26–540)	190	(150–260)	190	(150–240)	110	(57–240)
V (mg/kg)	60	68	68	69	(56–78)	65	(51–88)	71	(54–86)	79	(66–98)	73	(61–100)	81	(68–110)
Zn (mg/kg)	110	120	68	1500	(950–1900)	1100	(690–1700)	120 1	(94–2100)	680	(450–970)	400	(180–950)	110	(73–170)

X—Mean, X_BC—Mean (after Box-Cox transformation), Min—Minimum, Max—Maximum, ¹—without I-1 and I-2 (river terraces), explanation in text.

). A matrix of correlation coefficients was constructed to clarify the strength of the relationships between individual elements (

Table 2. Analyses of variances (ANOVA)—F-values and p-values.

	Area			Material			Depth
	(F)	(p)		(F)	(p)		(F)	(p)
Ag	87.74	0.00	*	3.21	0.05	*	0.04	0.84
Al	20.75	0.00	*	0.99	0.38		0.28	0.60
As	56.80	0.00	*	76.69	0.00	*	0.50	0.48
Ba	7.78	0.01	*	0.09	0.91		0.00	0.96
Ca	0.18	0.67		29.18	0.00	*	0.05	0.82
Cd	30.94	0.00	*	29.66	0.00	*	0.26	0.61
Cr	54.15	0.00	*	10.19	0.00	*	0.09	0.77
Cu	44.53	0.00	*	11.85	0.00	*	0.00	0.96
Fe	3.21	0.05	*	19.23	0.00	*	4.01	0.05	*
K	7.97	0.01	*	1.60	0.21		0.14	0.71
Li	0.01	0.91		0.79	0.46		1.08	0.30
Mg	40.91	0.00	*	13.57	0.00	*	0.01	0.93
Mn	17.86	0.00	*	41.94	0.00	*	0.03	0.87
Na	9.98	0.00	*	5.89	0.00	*	1.20	0.28
Ni	44.18	0.00	*	8.90	0.00	*	0.03	0.86
P	5.45	0.02	*	9.24	0.00	*	15.31	0.00	*
Pb	96.30	0.00	*	16.46	0.00	*	0.00	0.99
Sr	0.25	0.62		5.51	0.01	*	0.00	0.95
V	14.87	0.00	*	4.61	0.01	*	5.59	0.02	*
Zn	34.27	0.00	*	37.26	0.00	*	0.00	0.96

*—statistically significant values (p = 0.05).

). Additionally, correlation coefficients were calculated between the contents of the same elements at different soil depths (0–5 cm and 20–30 cm) (Appendix A), as well as between sample terraces (stream sediments, floodplain soils, and river terrace soils) (Appendix B and Appendix C). Furthermore, the relationships between element contents and river distance were examined (Appendix D).

Analysis of variance (ANOVA) was performed to assess the variation between the defined areas, sampled materials (river sediments, floodplain soils, and river terrace soils), and sampled soil horizons (topsoil, 0–5 cm, and subsoil, 20–30 cm) (Table 2). One-way ANOVA was also utilised to assess the significance of differences in element contents between soil horizons (Appendix A), between sediments and floodplain soils (Appendix B), and between floodplain and river terrace soils (Appendix C).

The relationships between chemical elements and defined geochemical groups were identified. To ensure robust criteria, only 11 chemical elements showing the highest correlation coefficients in multivariate analyses were considered (

Table 3. Correlation matrices of analysed elements.

Ag	1.00
Al	−0.28	1.00
As	0.55	−0.03	1.00
Ba	0.47	−0.08	0.40	1.00
Ca	0.19	0.42	0.59	0.16	1.00
Cd	0.75	−0.15	0.85	0.47	0.47	1.00
Cr	−0.43	0.33	−0.10	−0.53	0.15	−0.19	1.00
Cu	0.74	−0.15	0.73	0.48	0.43	0.85	−0.21	1.00
Fe	−0.08	0.51	0.40	−0.17	0.51	0.20	0.49	0.23	1.00
K	0.30	−0.13	0.04	0.66	−0.08	0.13	−0.68	0.20	−0.48	1.00
Li	−0.34	0.26	−0.27	−0.15	−0.11	−0.41	−0.10	−0.35	0.06	0.30	1.00
Mg	−0.39	0.47	−0.03	−0.43	0.29	−0.14	0.90	−0.22	0.54	−0.61	−0.02	1.00
Mn	0.32	0.15	0.81	0.26	0.60	0.61	0.09	0.54	0.70	−0.12	−0.05	0.16	1.00
Na	0.10	0.04	0.19	0.41	0.29	0.38	−0.06	0.21	−0.11	0.31	−0.33	0.06	0.03	1.00
Ni	−0.34	0.30	−0.08	−0.53	0.11	−0.16	0.94	−0.15	0.50	−0.67	−0.07	0.92	0.10	−0.11	1.00
P	0.34	0.15	0.61	0.36	0.69	0.53	−0.19	0.56	0.22	0.15	−0.13	−0.07	0.58	0.18	−0.19	1.00
Pb	0.90	−0.24	0.72	0.57	0.28	0.87	−0.39	0.85	0.01	0.31	−0.35	−0.35	0.48	0.21	−0.32	0.46	1.00
Sr	0.37	0.25	0.44	0.61	0.54	0.57	−0.10	0.46	0.08	0.29	−0.39	0.09	0.26	0.69	−0.13	0.45	0.49	1.00
V	−0.53	0.51	−0.38	−0.30	−0.01	−0.50	0.24	−0.43	0.33	−0.05	0.46	0.25	−0.19	−0.12	0.18	−0.22	−0.57	−0.27	1.00
Zn	0.67	−0.05	0.89	0.49	0.55	0.91	−0.14	0.82	0.27	0.14	−0.38	−0.07	0.67	0.39	−0.13	0.59	0.83	0.63	−0.43	1.00
	Ag	Al	As	Ba	Ca	Cd	Cr	Cu	Fe	K	Li	Mg	Mn	Na	Ni	P	Pb	Sr	V	Zn

).

This study utilised a multivariate approach, combining cluster analysis, principal component analysis (PCA), and R-mode factor analysis (FA), to investigate correlations among chemical elements and identify underlying factors or sources [69,70,71]. Before analysis, the raw data were standardised to a zero mean and unit standard deviation to ensure comparability and eliminate scale effects [69,72,73].

The complementary cluster analysis classified samples based on their multielement signatures, providing additional insight into geochemical trends related to the River Ibar and its sources (Figure 5). This multistep approach effectively detected element associations and linked them to potential sources, whether geogenic, anthropogenic, or mixed [70,71,74,75]. PCA was initially employed to examine the dataset’s structure and determine the total explained variance [76,77,78]. This step informed the subsequent factor analysis, which was performed using the linear product–moment correlation coefficient. Orthogonal rotation via the varimax method was applied to refine the factor structures (

Table 4. PCA (Factor) analyses.

	F1	F2	Comm
Cd	0.95	−0.07	90.1
Zn	0.95	0.01	89.6
As	0.92	0.11	85.6
Cu	0.90	−0.10	81.5
Pb	0.89	−0.31	89.5
Ag	0.77	−0.39	74.2
Mn	0.75	0.34	68.7
Cr	−0.18	0.93	88.9
Ni	−0.13	0.92	86.7
Mg	−0.12	0.94	89.3
Fe	0.35	0.73	65.3
Prp.Totl	50.7	31.9	82.7
EigenVal	5.69	3.40
Expl.Var	5.58	3.51

, Figure 6).

Content enrichment ratios are calculated to assess the extent of sample contamination. The ratio is determined by measuring a toxic metal’s content relative to a background level or reference element, such as aluminium or iron. This approach enables the identification and quantification of anthropogenic or other non-natural influences on metal contents, thereby highlighting the degree of enrichment attributable to human activities (

Table 5. Content ratios according to determined areas and sampling materials.

Area	Upper River Flow vs. Eu Average			Lower River Flow vs. EU Average			Upper vs. Lower River Flow
Sampling Material	Stream Sediment	Flood Plains	River Terraces	Stream Sediment	Flood Plains	River Terraces	Stream Sediment	Flood Plains	River Terraces
Ag 1,2	8.6	9.0	5.6	4.4	4.1	3.0	1.9	2.2	1.9
Al	0.9	0.7	0.7	1.0	1.0	0.9	0.9	0.8	0.8
As	57.1	20.1	4.6	14.5	6.0	3.2	3.9	3.4	1.4
Ba	0.8	0.8	0.8	0.7	0.7	0.7	1.1	1.2	1.2
Ca	0.7	0.4	0.5	0.7	0.5	0.4	1.0	0.8	1.1
Cd 1	24.3	15.3	3.8	9.7	4.9	3.7	2.5	3.1	1.0
Cr	2.3	2.1	0.9	3.9	4.0	2.9	0.6	0.5	0.3
Cu 1	3.7	2.4	1.5	1.6	1.2	1.3	2.3	2.1	1.1
Fe	1.8	1.7	1.2	1.6	1.7	1.5	1.1	1.0	0.8
K	0.7	0.8	0.9	0.7	0.7	0.7	1.0	1.1	1.2
Li	0.8	0.9	–	0.8	0.9	–	1.0	1.0	1.0
Mg	1.5	1.7	1.1	2.0	2.4	2.6	0.7	0.7	0.4
Mn	4.0	2.2	1.2	1.6	1.2	1.3	2.5	1.8	0.9
Na	1.0	1.0	0.8	1.3	1.3	0.9	0.8	0.8	0.9
Ni	5.8	5.5	2.2	8.8	11.0	7.2	0.7	0.5	0.3
P	1.4	1.0	0.8	1.1	0.9	0.7	1.3	1.1	1.1
Pb 1	16.8	13.5	4.6	4.9	2.7	1.7	3.5	5.1	2.6
Sr	1.0	0.9	1.0	1.1	1.2	0.8	0.9	0.8	1.2
V	1.0	1.1	1.0	1.2	1.2	1.2	0.9	0.9	0.9
Zn 1	12.3	10.5	1.8	5.7	3.8	1.6	2.2	2.8	1.1

¹ without I-1 and I-2 (river terraces), explanation in text; ²—the average value for topsoil was taken [66,67,68].

).

Data visualisation was performed using a combination of software packages, including Statistica 14 (StatSoft, Inc., Tuls, OK, USA) [79], QGIS 3.28 [80], and Surfer 25 (Golden Software, Inc., Golden, CO, USA) [81].

4. Results and Discussion

4.1. Element Contents Across Defined Zones and Sampled Materials

The mean values and ranges of the analysed elements are presented in Table 1 according to the defined zones (middle stream/lower stream) and sampled materials (stream sediment, floodplain, and river terraces). Analysis of Variance (ANOVA) was performed to determine statistically significant differences in element contents between the defined zones, sampled materials (river sediments, floodplain soils, and river terrace soils), and sampled soil horizons (topsoil, 0–5 cm, and subsoil, 20–30 cm) (Table 4).

No statistically significant differences were observed between the sampled soil horizons of floodplains and river terraces, except for Fe, P, and V, which showed relatively low F values (Table 2). A further ANOVA, considering only the differences between soil horizons, revealed a statistical difference only for P (Appendix A). Statistically significant differences were found among the sampled materials (stream sediment, floodplain soils, and river terrace soils) for most of the analysed elements, except Al, Ba, K, and Li. Notably, As, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Pb, and Zn show high F values (>10) (Table 2, Appendix B and Appendix C).

Significant differences were found between stream sediments and floodplain soils for Ca, P, Mn, Fe, and As, with Ca, P, and Mn demonstrating F > 10. Between floodplain soils and river terrace soils, differences were found for most of the analysed elements, including Ag, Cr, Sr, Ni, Fe, Cu, V, Mg, Ca, Pb, Mn, Cd, Zn, and As, with Mg, Ca, Pb, Mn, Cd, Zn, and As showing F > 10.

At the level of differences between defined areas (middle stream/lower stream), statistically significant differences were found for most of the analysed elements, except Ca, Li, and Sr (Table 2). Notably, Pb, Ag, As, Cr, Cu, Ni, Mg, Zn, and Cd show F values higher than 20. The largest differences in element contents were found between the defined areas, particularly for pollutant elements (Ag, As, Cd, Cu, Pb, and Zn) and naturally enriched elements (Cr, Mg, and Ni). Similarly, the largest differences were found between floodplains and river terraces, especially for those elements. In contrast, the differences between stream sediments and floodplains were relatively low and rarely statistically significant, as were the differences between soil depths statistically insignificant compared to the other factors, indicating that pre-industrial levels were not reached, even at a depth of 20–30 cm.

4.2. Relationships Between Contents of the Same Elements by Sample Material and River Distance

Correlation analyses were performed to examine the relationships between contents of the same elements in different sample materials and at varying distances along the river. High correlation coefficients (r > 0.7) were found between contents of the same elements in different soil horizons (Appendix D). Slightly lower but still significant correlation coefficients were observed for Al, Ba, and V. The analysis of correlation coefficients between stream sediments and floodplains revealed significant relationships for most of the analysed elements, except Ca, Fe, Al, and Sr, which did not show statistically significant correlations (r < 0.6).

As expected, no statistically significant correlations were found between river distance and most of the analysed elements, except Ag and Pb (Appendix D). The correlation coefficients between river distance and element contents in individual sample materials (stream sediment, floodplains, and river terraces) showed that Ag, As, Cd, Cu, Mn, and Zn showed highly significant negative correlations in stream sediments and floodplains. In contrast, Cr, Mg, and Ni showed highly significant positive correlations. In river terraces, highly significant negative correlations were observed for Ag and Pb, whereas Cr and Ni showed highly significant positive correlations (Appendix D).

The correlation analysis revealed similar patterns to the ANOVA results. High correlation coefficients were found between soil horizons of floodplains and river terraces, as well as between stream sediments and floodplains, indicating a relationship between these sample materials. The lack of correlations between river terraces and floodplains suggests that the contents of elements in river terraces may reflect pre-industrial background levels. This is supported by the fact that naturally enriched elements, such as Cr and Ni, still showed significant correlations.

The analysis suggests that the contents of anthropogenically introduced elements (Ag, As, Cd, Cu, Pb, and Zn) decrease linearly with distance from the source of pollution, while the contents of naturally enriched elements (Cr, Mg, and Ni) increase linearly, consistent with the frequency of occurrence of ophiolitic rocks (serpentinite and serpentinised peridotite) in the lower course of the Ibar River and the presence of Cr and Ni enriched background rocks.

4.3. Relationships Between Elements (Geochemical Groups)

The correlation matrix for all analysed samples reveals two distinct groups of elements with highly significant correlation coefficients (r > 0.7). The first group, comprising Ag, As, Cd, Cu, Mn, and Zn, is indicative of anthropogenic enrichment, likely resulting from mining and smelting activities in the middle flow of the Ibar River (The Mining and Metallurgical Complex Trepča). The second group, consisting of Cr, Mg, and Ni, suggests enrichment related to the weathering of elements from the ophiolite zone in the lower Ibar River (Table 3).

Multivariate analyses support this grouping. Cluster analysis and Principal Component Analysis (PCA) with factor analysis both identify similar groupings, with the former highlighting two strongly correlated groups at the 20% level (Figure 5). The PCA results show slight variations in the distribution of Fe and Mn, as evident in the F1 vs. F2 diagram (Table 4, Figure 6). The distribution of these elements shows the same patterns. Ag, As, Cd, Cu, Pb, and Zn contents are elevated in areas impacted by mining, processing, and smelting activities, whereas Cr, Mg, and Ni contents are naturally enriched in areas with ore deposits in the ophiolite zone of the lower Ibar River (Figure 6). The distributions of these chemical elements will be described in detail below (Figure 7 and Figure 8).

4.4. Anthropogenically Induced Element Contents

The analysis revealed extremely high contents of Ag, As, Cd, Cu, Pb, and Zn in the middle part of the studied area, particularly in river sediment and floodplain soil (Table 1 and Figure 2, Figure 4, and Figure 7).

4.4.1. Silver (Ag)

The average silver (Ag) content in stream sediment is 2.6 mg/kg, comparable to that in floodplains (2.8 mg/kg). In contrast, the river terrace exhibits a slightly lower average content of 2.5 mg/kg, although sampling points I-1 and I-2 display anomalously high Ag contents (Table 1, Figure 7). Due to the documented extreme contamination in the wider area [33], these values were excluded from the background assessment to prevent result skewing, yielding an adjusted average of 1.7 mg/kg. A similar methodology was applied to cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) Notably, Ag contents in the lower reach of the Ibar River are approximately half those observed in the middle flow, with average contents of 1.3 mg/kg in stream sediment, 1.2 mg/kg in floodplains, and 0.91 mg/kg on river terraces (Table 1, Figure 7).

4.4.2. Arsenic (As)

The average arsenic (As) content in stream sediment is 580 mg/kg, more than double that recorded in floodplains (250 mg/kg), whereas the river terrace exhibits substantially lower As contents (53 mg/kg). Unlike silver (Ag), As contents at sampling points I-1 and I-2 did not show anomalous values. In the lower Ibar stream, the average As content in stream sediment is 150 mg/kg, exceeding twice the average content in the adjacent floodplain (73 mg/kg). Notably, the average As content on the river terraces is significantly lower, at 38 mg/kg, and is the only value that does not exceed critical thresholds according to the New Dutch list (#). Consistent with the trend observed for silver (Ag), all listed As values are approximately two-fold lower in the lower reach compared to the middle flow (Table 1, Figure 7). The elevated As contents pose a considerable concern, representing the most significant issue.

4.4.3. Cadmium (Cd)

The average cadmium (Cd) content in stream sediment is 13 mg/kg, considerably higher than that recorded in floodplains (8.6 mg/kg). Similar to silver (Ag), the highest Cd contents were observed at sampling points I-1 and I-2, and the average Cd content on river terraces was estimated using the same methodology. The estimated average content (1.1 mg/kg) is approximately 8-fold lower than that in floodplains and nearly 12-fold lower than that in stream sediment (Table 1, Figure 7).

In the lower flow of the Ibar River, the average Cd content in stream sediment is 5.1 mg/kg, almost twice that recorded in floodplains (2.8 mg/kg). Notably, both values are 2.5 to 3 times lower than the corresponding contents in the middle flow. In contrast, the average Cd content on river terraces (1.1 mg/kg) is comparable to that observed in the middle flow (Table 1, Figure 7).

4.4.4. Copper (Cu)

The average copper (Cu) content in stream sediment is 81 mg/kg, exceeding that recorded in floodplains (61 mg/kg). Similar to silver (Ag), the highest Cu contents were observed at sampling points I-1 and I-2, and the average Cu content on river terraces was estimated using the same methodology. The estimated average content (25 mg/kg) is more than 2-fold lower than that in floodplains and nearly 3-fold lower than that in stream sediment.

In the lower reach of the Ibar River, the average Cu content in stream sediment is 35 mg/kg, higher than the average content recorded in floodplains (23 mg/kg). Notably, both values are 2 to 3 times lower than the corresponding contents in the middle flow. The average Cu content on river terraces (23 mg/kg) is comparable to that observed in the middle flow. Although the distribution of Cu exhibits an anthropogenic pattern, the absolute values are substantially lower than those recorded for Ag, As, Cd, Pb, and Zn (Table 1, Figure 7).

4.4.5. Lead (Pb)

The average lead (Pb) content in stream sediment is 560 mg/kg, lower than that recorded in floodplains (730 mg/kg). Similar to silver (Ag), the highest Pb contents were observed at sampling points I-1 and I-2, and the average Pb content on river terraces was estimated using the same methodology. The estimated average content (150 mg/kg) is approximately 5-fold lower than that in floodplains and stream sediment.

In the lower Ibar River, the average Pb content in stream sediment is 190 mg/kg, exceeding the average Pb content in floodplains (140 mg/kg). Notably, the average Pb content on river terraces is 3 to 4 times lower than that in floodplains and stream sediment. Furthermore, all average Pb contents in the lower reach are 3 to 5 times lower than those observed in the middle flow (Table 1, Figure 7).

4.4.6. Zinc (Zn)

The average zinc (Zn) content in stream sediment is 1500 mg/kg, exceeding that recorded in floodplains (1100 mg/kg). Similar to silver (Ag), the highest Zn contents were observed at sampling points I-1 and I-2, and the average Zn content on river terraces was estimated using the same methodology. The estimated average content (120 mg/kg) is more than eight-fold lower than that in floodplains and over 12-fold lower than that in stream sediment.

In the lower reach of the Ibar River, the average Zn content in stream sediment is 680 mg/kg, exceeding the average content recorded in floodplains (400 mg/kg). Notably, both values are 2 to 3 times lower than the corresponding contents in the middle reach. The average Zn content on river terraces (110 mg/kg) is comparable to that observed in the middle flow (Table 1, Figure 7).

4.5. Natural Enrichment of Elements

The following group comprises trace elements chromium (Cr), magnesium (Mg), and nickel (Ni), which showed natural enrichment in the lower river flow due to geogenic factors or the presence of numerous ore deposits associated with serpentinite and serpentinised peridotites of Jurassic age (Table 1 and Figure 2, Figure 4, and Figure 8).

4.5.1. Chromium (Cr)

In the middle flow of the river, the average chromium (Cr) content in stream sediment is 210 mg/kg, comparable to the average content in floodplains (200 mg/kg). Notably, the average Cr content on river terraces is approximately 3-fold lower (88 mg/kg) than that observed in the aforementioned sample types.

In the lower Ibar River, the average Cr content in stream sediment is 360 mg/kg, similar to the average content recorded in floodplains (370 mg/kg). The average Cr content on river terraces is slightly lower, at 280 mg/kg. Comparison of the two river flows reveals that average Cr contents in stream sediments and floodplains are approximately 2-fold higher in the lower flow than in the middle flow, while the difference is more pronounced on river terraces, with a greater than 2-fold increase (Table 1, Figure 8).

4.5.2. Nickel (Ni)

In the middle river flow, the average nickel (Ni) content in stream sediments is 200 mg/kg, comparable to the average content in floodplains (190 mg/kg). Notably, the average Ni content on river terraces is approximately 2-fold lower (81 mg/kg) than that observed in the aforementioned sample types.

In the lower Ibar River, the average Ni content in stream sediments is 310 mg/kg, slightly lower than the average Ni content recorded in floodplains (380 mg/kg). The average Ni content on river terraces is even lower, at 270 mg/kg. Comparison of the two river flows reveals that the average Ni content in stream sediments is marginally higher in the lower flow than in the middle flow. More pronounced differences are observed in floodplains and river terraces, where the average Ni contents are two-fold or more than three-fold higher (Table 1, Figure 8).

4.5.3. Magnesium (Mg)

Similar trends to those observed for Ni and Cr were observed for magnesium (Mg). In the middle river flow, the average Mg content in stream sediments was 1.6%, comparable to the average content in floodplains (1.7%). Notably, the average Mg content on river terraces was approximately two-fold lower (0.78%) than that observed in the aforementioned sample types.

In the lower Ibar River, the average Mg content in stream sediments was 2.1%, slightly lower than the average content recorded in floodplains (2.4%). The average Mg content on river terraces was marginally lower, at 1.8%. Comparison of the two river flows revealed that the differences in average Mg contents were less pronounced than those observed for chromium (Cr). In the lower flow, average Mg contents in stream sediments and floodplains were moderately higher, whereas on river terraces, the average content was more than 2-fold higher (Table 1).

4.6. Distributions Representing the Background

Based on the distribution patterns, aluminium (Al) and vanadium (V) were identified as elements that do not show significant enrichments across different areas or sample types, or these differences are minor and inconsequential. The distributions of these elements represent the actual background, unaffected by natural enrichments or anthropogenic influences (Table 1, Figure 9).

4.6.1. Aluminium (Al)

In the middle river flow, the average aluminium (Al) content in stream sediment is 4.6%, slightly higher than the average content in floodplains (3.9%) or on river terraces (4.1%). In the lower Ibar River flow, the average Al content in stream sediment is 5.3%, similar to the average content recorded in floodplains (5.1%) or on river terraces (5.0%). Comparison of the two river flows reveals that average Al contents in all sample types are marginally higher in the lower flow than in the middle flow (Table 1, Figure 9).

4.6.2. Vanadium (V)

In the middle river flow, the average vanadium (V) content in stream sediment is 69 mg/kg, comparable to the average contents recorded in floodplains (65 mg/kg) or on river terraces (71 mg/kg). In the lower Ibar River flow, the average V content in stream sediment is 79 mg/kg, similar to the average Al content recorded in floodplains (73 mg/kg) or on river terraces (81 mg/kg). Notably, average V contents in all sample types are noticeably higher in the lower river flow than in the middle flow (Table 1, Figure 9).

4.7. Enrichment (Content) Ratios

Enrichment ratios relative to European averages (Table 5) were calculated for the same materials and between defined areas (Table 1). As anticipated, extremely high enrichment ratios (contamination factors) were observed in the middle part of the study area for silver (Ag), arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn), particularly in stream sediments and floodplain soils (Table 5). In stream sediments, the enrichment ratios were found to follow the order of As (57.1), Cd (24.3), Pb (16.8), Zn (12.3), Ag (8.6), and Cu (3.7). The value of As indicates that the average As content in stream sediments in the middle river flow exceeds the European average by 57 times. On floodplains, a similar order was observed, although the values were slightly lower or comparable: As (24), Cd (16), Pb (19), Zn (9.3), Ag (9.0), and Cu (2.8). On river terraces, less pronounced enrichment relationships were observed, following the order Ag (5.6), As (4.6), Pb (4.6), Cd (3.8), Zn (1.8), and Cu (1.5).

Given the established extreme contamination in the wider area covering sample points I-1 and I-2 [33], these analytical values were excluded from the processing, as they would have interfered with the background assessment. The same procedure was applied to Cd, Cu, Pb, and Zn (Table 5). In the lower river flow, significantly lower enrichments of the listed elements were observed in all sample media, in the following order: stream sediments: As (14.5), Cd (9.7), Zn (5.7), Pb (4.9), Ag (4.4), and Cu (1.6); floodplains: As (6.0), Cd (4.9), Ag (4.1), Zn (3.8), Pb (2.7), and Cu (1.2); and river terraces: Cd (3.7), As (3.2), Ag (3.0), Pb (1.7), Zn (1.6), and Cu (1.3).

When the enrichment ratios were compared between the middle and lower river flow, it was found that the enrichments in stream sediments followed the order of As (3.9), Pb (3.5), Cd (2.5), Cu (2.3), Zn (2.2), and Ag (1.9). On floodplains, similar enrichments were observed, with some deviations, following the order Pb (5.1), As (3.4), Cd (3.1), Zn (2.8), Ag (2.2), and Cu (2.1). The middle river flow is characterised by numerous outcrops of polymetallic sulphide ores, enriched in Ag, As, Pb, and Zn, associated with Neogene volcanic rocks (quartz-latite, dacite, latite, and trachyte). Therefore, the calculated averages (Table 1) and enrichment ratios (Table 5) on river terraces are considered to represent the actual local background with natural enrichment of these elements.

The findings suggest that As poses the biggest problem due to its high content and enrichment, particularly in stream sediments, which far exceeds the contents found in floodplains, indicating recent transfer and potential future increases in content and enrichment on floodplains. Cd follows, with significant exceedances in stream sediments compared to floodplains. Pb and Zn show similar contents in stream sediments and floodplains, although Pb stands out due to its high enrichments and load. Cu displays an anthropogenic pattern, but its contents and enrichment ratios are relatively low, posing no additional environmental burden.

5. Conclusions

Overall, the study provides valuable insights into the extent and distribution of toxic element contamination in the Ibar River, which can be attributed to long-term mining and mineral processing activities, as well as inadequate waste management practices within the river’s catchment area.

The Ibar River study reveals significant anthropogenic enrichment of various toxic elements, including silver (Ag), arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). These elements show distinct distribution patterns, with elevated contents primarily found in the middle part of the studied area, particularly in river sediments and floodplain soils.

Significant differences were observed in element contents between defined areas and sampled materials. Pollutant elements like Ag, As, Cd, Cu, Pb, and Zn exhibit pronounced differences between areas and between floodplains and river terraces, indicating widespread contamination. Correlation analysis shows strong relationships between element contents in different materials and along the river’s course. Anthropogenic elements decrease with distance from the contamination source, while naturally enriched elements increase due to ophiolitic rocks in the lower river course. Multivariate analysis identifies two distinct element groups: one linked to anthropogenic enrichment from mining and smelting (Ag, As, Cd, Cu, Mn, and Zn), and the other associated with natural enrichment from ophiolite rock weathering (Cr, Mg, and Ni). The study highlights extreme contamination in the middle river flow, particularly for Ag, As, Cd, Cu, Pb, and Zn, with As exceeding European averages by 57 times in stream sediments. As, Cd, Pb, and Zn pose significant environmental concerns, emphasising the need for continuous monitoring.

Arsenic stands out as the most critical concern, with average contents in stream sediments flowing 580 mg/kg, more than double those in floodplains (250 mg/kg) and substantially higher than in river terraces (53 mg/kg). Silver, cadmium, copper, lead, and zinc also display elevated contents, albeit to varying degrees. Stream sediments and floodplains tend to have higher contents of these elements compared to river terraces. For instance, lead contents in floodplains flow 730 mg/kg, whereas river terraces have an estimated average content of 150 mg/kg. A notable trend is a decrease in contents downstream, with values in the lower flow generally 2–3 times lower than those in the middle flow. River terraces show significantly lower contents, estimated to represent local background levels with natural enrichment.