1 Introduction

The development of many emerging regions depends on urbanization, industry, intensive agriculture, socio-related activities, and extractive processes. The discharge and refuse produced from these procedures diminish and deteriorate the condition of freshwater bodies [1,2,3]. The rapid urbanization and industrialization in the river basin have resulted in heightened pressure on rivers, manifesting as water pollution and degradation of ecological well-being [4,5,6]. The use of water resources is intricately linked to several elements influenced by the nature of the sources, whether natural or human-made, as well as temperature changes. These elements include water quality [7,8,9], degradation processes such as eutrophication and overgrowth, hydrological processes, and severe natural events. In recent years, the presence of dangerous heavy metals and rare earth elements in the environment has garnered significant concern from the public and scientific community.

Researchers worldwide have become increasingly interested in this issue due to the high levels of pollution, toxicity, and nonbiodegradability associated with these substances, which threaten environmental ecosystems [10,11,12,13,14,15]. Pollution caused by heavy metals is widely recognized as a significant and persistent hazard to the aquatic environment. This is due to the chronic nature, stability, toxicity, and tendency of heavy metals to penetrate the food chain and accumulate in living organisms [15,16,17,18]. Rivers serve as crucial ecosystems, providing invaluable resources and sustenance for aquatic life and human communities. However, these water bodies are increasingly threatened by anthropogenic activities, contaminating water resources. In this context, heavy metals and microplastics (MPs) in river systems have emerged as a significant concern due to their potential adverse effects on environmental and human health [19]. In recent decades, the wide use of plastic products has increased worldwide due to their durability, lightweight, low cost, waterproof, and low electrical and thermal conductivity [20,21,22,23]. Each plastic material ever manufactured remains on Earth in the same form or certain other, becoming an ongoing environmental issue [24,25,26,27]. River surface waters maintain biodiversity and provide household, agricultural, and industrial uses, making their health crucial in Poland.

Plastics are a newly recognized pollutant in many aquatic environments [28,29,30,31]. Plastic pollution has been extensively researched in marine ecosystems, but there has been a lack of research on its impact on freshwater environments [32]. However, studies on the prevalence and actions of MPs in freshwater are increasingly important. The significance of freshwater cannot be overstated since it serves as a primary water supply distributed to homes via water treatment processes. Terrestrial environments impact the present condition of MP freshwater. Their surrounding environment immediately affects freshwater bodies near plastic production sites, exhibiting MPs inside the freshwater bodies [33]. The most significant textile manufacturing region in Asia, China, was found to have a concentration of MPs (13.3 items/L), which is more than double the level in the reference location. Due to the manufacturing and commercial operations of the textile industry in the vicinity, significant amounts of MP pollution have been identified in the neighbouring freshwater bodies and sediment [34]. The Taihu Lake in the Taihu Basin has a highly elevated concentration of MPs, ranging from 3.4 to 25.8 pieces per litre. This phenomenon may be linked to the significant contribution of the manufacturing and agricultural sectors, accounting for 14% of China's gross domestic product [35].

The hydrological process is crucial in determining MPs' quantity and spatial distribution due to the many freshwater bodies of diverse sizes and terrains throughout different locations. MPs exhibit an upward trend in concentration as they flow downstream in China's Suzhou and Huangpu rivers. Urban areas and estuaries have elevated levels of microplastic contamination. Conversely, the quantity of MPs in fibres often diminishes as one moves from small urban water bodies to the sea. MPs in the water may have diminished due to a diluting effect throughout their migration. Adjacent contaminants are more likely to impact small urban streams, whereas hydrological processes are more likely to facilitate the transportation of MPs in big rivers [36]. The research on the Netravathi River in India provides evidence that the quantity of MPs is more significant in areas downstream than upstream. This conclusion highlights the influence of urban population expansion and human activities on the prevalence of MPs in the river [37]. Similarly, in the Nakdong River in Korea, the level of MPs rises as it flows downstream, accompanied by a higher percentage of fibres [38].

This research measured MPs, heavy metal concentrations, and critical physicochemical properties to evaluate the hazards to the health of Polish fresh river surface water (Nida River). Concentrations of heavy metals, which are hazardous even at trace levels, such as cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), zinc (Zn), and cobalt (Co), were examined. MP analysis was also conducted to determine the extent of MP contamination, which risks human health and aquatic ecosystems via the food chain. pH, conductivity, and turbidity were tested to comprehend the quality of the water. The overall state and potential changes in river water quality due to environmental stressors are shown by physicochemical measurements. A comprehensive picture of Polish fresh river surface water is presented through these investigations, emphasizing potential risks related to MPs, physicochemical parameter changes, and heavy metal contamination. The development of suitable management strategies and policies to safeguard these vital aquatic ecosystems depends on the results of this research.

We hypothesize that freshwater ecosystems experiencing anthropogenic influence will exhibit elevated levels of MP intrusion and heavy metal contamination, with urbanized areas showing higher concentrations due to increased human activities and pollution inputs, thereby serving as reliable indicators of overall river health.

2 Material and methods

2.1 Sampling, sample preparation, and quality assurance/quality control

Water samples were collected from a Nida river in Świętokrzyskie, Poland, in October 2022 (Fig. 1). The Nida is a river that covers 154 kms in length and is located in central Poland. The river is the longest in the Świętokrzyskie Province and is a left tributary to the Vistula river. The Nida's basin covers an area of 3844 square kilometers and includes the Nida Landscape Park, a designated protected area. The Nida River is impacted by direct and indirect pollution sources primarily related to agricultural practices, industrial discharges, municipal wastewater, and urban runoff. The samples were randomly collected in (500 ml) glass bottles. Five samples were collected from different river places and filtered through a Whatman glass microfiber filter (GF/A-1.6 µm–47 mm). During the analysis, plastic materials were avoided for quality control of MPs in the samples; only glass material was used. All the solutions used in the study were pre-filtered through the same type of filters used to analyze samples to remove the contaminants if present [39]. Access to the laboratory was limited. Cotton laboratory attire and nitrile gloves were used to reduce the possibility of contamination. The surfaces where the tests were carried out and all the materials used during the analysis were regularly cleansed with 5% nitric acid and deionized water to eliminate any possible MPs. Dark glass bottles (500 ml) were utilized for sampling to reduce the influence of photo-degradation. Before sampling, the sampling bottles were cleaned with filtered Milli Q DI water and used carefully to avoid contamination. Plastic bottles were not used to reduce the chance of MPs being added to the bottles. A layer of aluminum foil was put between the bottles and screw closures to minimize sample contamination. First, the samples’ turbidity, pH, and conductivity were measured. The water samples were filtered through a Whatman glass microfiber filter for quality, quantitative MPs analysis, and ICP-OES analysis.

Fig. 1
figure 1

Location of the study area (Nida river-Świętokrzyskie)

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2.2 Instrumental analysis

The MPs were physically characterized using a computer-controlled system for automated image analysis, namely a stereoscopic microscope Nikon SMZ800 with a Prior stage and NIS-Elements application. The microscope has a computer system and software for detailed image analysis. This includes the ability to measure and count items automatically and manually. The stereomicroscope has a zoom head that allows for magnification ranging from 20 × to 126×, ensuring enhanced spatial perception of the enlarged picture. A specialized colour CCD digital camera is linked to the microscope. The halogen illuminator has a variable light intensity and high power level. A motorized measuring table enables accurate movement control along the XY or XYZ axes. The control is performed using a control stick or a computer, allowing for effortless scanning of the sample surface with an accuracy of up to 0.1 μm. The plastic particles were enumerated as the total MPs under the stereomicroscope. Under the stereomicroscope, MPs were counted, and their physical characteristics, like colour, type, and size, were also analyzed based on the previous studies [40,41,42] using ImageJ software.

The samples' turbidity, pH, and conductivity were also assessed using automated equipment. The Hach turbidity meter (2100P ISO turbidimeter) was used to measure turbidity, the Elmetron PH meter (CPC-505) was used to test pH, and the Elmetron conductivity meter (CC-551) was used to measure conductivity. The concentrations of potentially hazardous elements (Cd, Cu, Cr, Ni, Pb, Zn, and Co) in the water samples were analyzed using a Perkin Elmer Optima 8000 ICP-OES instrument (PerkinElmer, Waltham, MA, USA). This device is very effective for analyzing elements. It provides exceptional sensitivity, the ability to explore several elements simultaneously, low limits of detection, and precise quantitative measurements for a wide variety of elements.

The scanning electron microscopy (SEM) technique was used to analyze the micro and nanostructure of the MPs that were gathered on the Whatman glass microfibre filter. The experimental setup included using a Quanta FEG 250 microscope acquired from the FEI Company (Hillsboro, OR, USA), which was equipped with a Large Field Detector (LFD), Backscattered electron detector (BSED), and an energy-dispersive X-ray microanalyzer (EDS). Before being subjected to microscopic examination, the filters were allowed to dry adequately at ambient room conditions without further sputtering to avoid any alteration to their composition. The experiment was conducted under vacuum conditions with a pressure of 30 Pa. An electron beam with an energy of 5 kV was used, along with a working distance ranging from 9.2 to 10.3 mm. Image capture was accomplished using a magnification range of 4000 × to 16000×, using the LFD and BSED detectors. Elemental analysis was carried out using the EDS detector.

2.3 Health risk assessment

The process of evaluating the health risks associated with exposure to a chemical agent involves four distinct stages: identifying the potential hazards, assessing the level of exposure, evaluating the relationship between the dosage and the response, and characterizing the overall risk. The foundation of the exposure evaluation is to ascertain the amount of dosage ingested. The health risk assessment was calculated based on previous studies on drinking water [43, 44]. The Chronic Daily Intake (CDI, mg/kg × day) was calculated using Eq. 1:

$$\text{CDI}=\text{C}\frac{\text{CR}\times \text{EF}\times \text{ED}}{\text{BW}\times \text{AT}}$$
(1)

where: C is the average concentration of metals at exposure, mg/L; CR is contact rate, L/day; EF is exposure frequency, days per year; ED is exposure duration, years; BW is body weight, kg; AT is period over which exposure is averaged, days. In Table 1, the values of parameters for CDI calculation are reported. Non-carcinogenic health risk assessment is based on the Hazard Quotient (HQ), calculated using Eq. 2.

$$\text{HQ}=\frac{\text{CDI}(\text{non carcinogenic})}{\text{RFD}}$$
(2)

where RFD is the Reference Dose Factor [mg/kg/day], the Hazard Index (HI) is the HQ sum calculated when several metalloids are studied; the critical value for HQ and HI is 1. The individual excess lifetime cancer risk (IELCR) is calculated for carcinogenic substances using Eq. 3.

$$\text{IELCR}=\text{CDI}\left(\text{carcinogenic}\right)\times \text{SF}$$
(3)

where SF is the Slope Factor (mg/kg/day), total IELCR is calculated when several carcinogenic metalloids are studied. The critical value for IELCR and total IELCR is 10−6.

Table 1 The values of parameters for exposure assessment calculation
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2.4 Visualizing data

In this study, all statistical analyses, such as average, standard deviation, data analysis, human health risk assessment, and graph plotting, were done using Excel, Origin, and SPSS software.

3 Result and discussion

3.1 Microplastic characterization

The Nida River exhibited the existence of diverse colored MPs (white, red, green, blue, etc.) in various physical states (fibers, fragments, pellets, foams, etc.) (Fig. 2). The variations were seen in the number of MPs among five sample locations, with values ranging from 215 to 280 MPs/L. The mean number of MPs observed was 245 ± 21 per liter. The MPs had sizes of 2245, 4556, 2176, 2304, and 2974 µm, with an average size of 2852 ± 899 µm. Terrestrial sources impact the present condition of MPs in freshwater. Freshwater bodies located in regions where plastics are manufactured are affected by the surrounding environment, showing the presence of MPs in the water [33]. Several studies have highlighted MPs in regions frequented for tourism and fishing [45,46,47]. Tourists discard single-use plastics, including water bottles, carry bags, straws, plastic sheets, and packaging, which collect in water bodies and degrade over time due to weathering and temperature changes. Fishermen discard fishing nets, which can affect aquatic species [48]. Despite their diverse distribution, MPs have been identified in all stages of freshwater environments, including fish, biota, sediments, surface water, and drinking water [49]. Studies show MPs are more prevalent in urban areas than non-urban regions but have also been found in distant places like alpine lakes [50,51,52]. MP abundance in water ranges from 0 to millions of pieces per cubic meter, depending on parameters including sampling techniques, sampling scale, sampling size, site selection, and human activity [53].

Fig. 2
figure 2

Examples of several MPs detected from the Nida River

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MP dispersion is influenced by environmental variables, mainly anthropogenic and hydrodynamic causes [37]. Deng et al. found an abundance of MPs ranging from 2.1 to 71.0 per liter in water containing all polymers in China textile city, Shaoxing City, China [34]. MPs found in nine Patagonia, Argentina lakes were primarily sourced from urban areas, textiles, and fishing [54]. Mao et al. found the presence of around 3.12 to 11.25 particles per liter in Wuliangsuhai Lake, Bayannaoer City, and Inner Mongolia [55]. Numerous studies in Europe, the USA, and Korea have confirmed the presence of MPs in freshwater systems in varying forms depending upon the location, with an abundance of zero to a few thousand particles per cubic meter. Studies carried out in freshwater systems in China have confirmed the presence of MPs in almost every investigated system, confirming every type of polymer with an abundance of zero to millions of particles per cubic meter [48]. The plastic buildup in aquatic environments may break down into nano-scale plastic particles, posing a significant danger to many creatures [56]. Plastic either decomposes, releasing harmful chemicals used during manufacture, or absorbs these chemicals on its surfaces, causing damage to the environment [57,58,59,60].

3.2 Elemental analysis

The SEM examination of water samples indicates the existence of various MPs. The morphological characterization of these MPs exhibited degradation patterns (Fig. 3). The EDX examination indicates the existence of many elements, such as C, N, O, Na, Mg, Al, Si, P, etc. C, O, Na, Al, Si, and K concentrations were higher, whereas S, Cl, T, and Fe concentrations were lower (Table 2). The distribution and composition of elements in MPs differed across the samples, with no prevailing presence or dominance of any specific component or portion. The discrepancy might be due to distinguishing individual MPs and their compositions or from contaminants on their surface. Silicate minerals on MPs include mostly Al, Si, Na, and Mg. The presence of these elements is probably a result of silicates being adsorbed onto the surface of the MPs. Al, Ca, Si, and Mg mainly originate from natural sources such as soil or dust. In contrast, Cu and Zn are primarily a result of human activity, such as burning fossil fuels and vehicle abrasion [61,62,63], which can also adhere to the surface of MPs. The elements Na, Mg, K, Al, Si, Ca, Cl, and O stick to the surface of the MPs, and silicate minerals such as clays may cause their presence [64, 65]. Zn is a prominent urban element thought to have originated mostly from human activities, including transportation and industrial processes [66, 67]. Fe is often used as an addition in plastic materials to attain certain qualities, such as imparting color to the plastic [68]. A broad range of elements (Ti, Si, Zn, Al, and Fe) have been employed in paintings as pigments, binders, or additions to generate a wide range of colors, textures, and functionalities [69,70,71,72]. These additives may be released into the environment due to weathering since they are not chemically bound to the polymeric matrix [56, 73]. Minerals like gypsum contain S naturally [74], and these gypsums are used in construction.

Fig. 3
figure 3

SEM characterization of microplastics

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Table 2 EDX analysis of microplastics
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3.3 Heavy metal concentration

The heavy metal concentration of Nida River water shows variations among their concentrations (Table 3). Zn had the highest average concentration, 96.86 ± 40.25 μg/L in all samples, followed by Pb 37.6 ± 31.9 μg/L. Various studies have investigated the levels of heavy metals in rivers in Poland [75, 76]. Heavy Metals analysis of bottom sediments of Warta River, Poland Cd 0.03–14.5 mg.kg−1, Cr 0.78–193 mg.kg−1, Cu 0.4–116 mg.kg−1, Ni 0.56–36.7 mg.kg−1, Pb 1–144 mg.kg−1 and Zn 0.50–519 mg.kg−1 [75] was higher than the concentrations of heavy metals seen in Nida river. In another study [76] in Poland, the heavy [75,76,77] metal concentration of river water Cr, Ni, Cu, Zn, Cd, and Pb were higher than heavy metals in the Nida River studied in this study. The overall average concentration values for Cd, Cu, Cr, Ni, Pb, and Co were below the limit values set by WHO [78], US EPA [79], and Polish regulations [80] for drinking water. This indicates that the examined water is not directly suitable for human consumption. Anthropogenic and natural pollution are the primary causes of pollution in a water environment. Most previous studies suggest that heavy metal contamination is mainly connected with anthropogenic sources [75,76,77]. Cheng et al. reported that Pb contamination was mainly from natural background and anthropogenic sources, with 45% and 55% contribution rates, respectively [77]. Setia et al. emphasized that non-point sources, such as agricultural runoff from metropolitan areas and soil erosion, significantly affect heavy metal pollution and should not be disregarded because of their intricate nature and challenging analysis [81]. An examination of 47 rivers in Poland indicates that the primary causes of point pollution are industrial and urban [76]. Setia et al. proposed that the release of chemical waste from industrial zones is a primary cause of pollution in aquatic ecosystems [81]. High levels of heavy metals may be detrimental to human health, ecosystems, and the environment. They may build up in living creatures, causing a range of health issues. It is crucial to monitor and manage the levels of heavy metals in the environment to safeguard human health and ecosystems. It often includes frequent testing, regulatory actions, and pollution management methods to reduce exposure and avoid contamination.

Table 3 The concentration of heavy metals in the Nida River
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3.4 Turbidity, pH, and conductivity

Water samples' turbidity, pH, and conductivity were analyzed (Table 4). The average turbidity, pH, and conductivity were 46 ± 23, 7 ± 0.33, and 1338 ± 40. Water samples' turbidity, pH, and conductivity were cross-checked with the EPA [79], WHO [78], and Polish drinking water guidelines [80]. In most cases, the parameters did not follow these standards. Turbidity may result from poor water quality, and elevated turbidity levels may lead to the staining of materials, fixtures, and fabrics exposed during washing. Turbidity reduces the drinkability of water. Although most particles generating turbidity are not directly hazardous, they may indicate the presence of dangerous chemical and microbiological contaminants. Consequently, many people consider turbid water unsafe to drink. Regulating the pH of water entering the distribution system is essential to minimize corrosion of water mains and pipes in home water systems. Alkalinity and calcium control affect water stability and its propensity to damage pipes and appliances. Insufficient attempts to decrease corrosion may result in the contamination of drinking water and adverse effects on its taste and appearance. Extreme conductivity levels may suggest problems like pollution, salinity, or the need for water purification. The turbidity of the Nida River was higher than Bludzia (0.5–6 NTU) and Goldapa River (1–10 NTU) [82]. According to many authors [83, 84], water turbidity can be caused by many substances, including soil and rock particles. The pH of the Nida River was mostly acidic, while Bludzia and Goldapa River's pH was basic [82]. According to Szczykowska and Siemieniuk [84], most natural waters have a pH of 6.5–8.

Table 4 Parameters of Nida River
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3.5 Health risk assessment

The determination of heavy metals’ non-carcinogenic and carcinogenic effects was done using the HQ and ELCR Table 5 summarises the estimated HQ of trace elements for two age groups (children and adults) that consume the drinking water of the Nida River Table 5 shows that all HQ values of the heavy metals were less than one for adults and children. Consequently, evaluating the human health risk associated with all detected trace elements revealed that the HQ values exhibit a satisfactory degree of non-carcinogenic adverse health risk [85, 86]. Table 5 also shows that HI values for adults and children age groups were less than one and were in the order of Cu 0.0171426 > Cr 1.4693E−06 > Ni 8.39612E−10 > Zn 7.19657E−12 for adults and Cu 0.0400002 > Cr 8.00008E−06 > Ni 1.06668E−08 > Zn 2.13338E−10 for children respectively. Based on the non-carcinogenic risk, these HI values of less than one show that the water of the Nida River is safe for human ingestion. Overall, the study's findings showed no appreciable non-carcinogenic risk for the heavy metals examined; nevertheless, regular monitoring is still required since unexpected contamination may occur. Table 5 represents the estimated ELCR values of carcinogenic heavy metals. For carcinogenic substances, the acceptable threshold is 10−6. In most water treatment samples, the carcinogenic value exceeds the threshold value. The range of carcinogenic risk levels could be characterized in detail based on the level range: the very low (< 10–6), low (10–6–10–5), medium (10–5–10−4), high (10–4–10–3), and very high (> − 10–3) [87,88,89]. An elevated cancer risk value beyond the permissible limit suggests a potential increase in the occurrence of cancer cases in the study region as a result of metal exposure via water consumption by both adults and children [4].

Table 5 Non-carcinogenic and carcinogenic risk of trace metals in Nida River
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4 Conclusion

Although there has been much study on MPs and heavy metals in saltwater, knowledge about MPs and heavy metals in freshwater is scarce. Research on the prevalence and actions of MPs and heavy metals in freshwater is increasing. Freshwater is crucial since it is the source of treated water delivered to homes. The Nida River showed a variety of colorful MPs in different physical forms, such as fibers, fragments, pellets, and foams. Variations in the number of MPs were observed across five sample sites, with values ranging from 215 to 280 MPs/L. The average number of MPs recorded was 245 ± 21 per litre. The MPs measured 2245, 4556, 2176, 2304, and 2974 µm, with an average size of 2852 ± 899 µm. Current status of MPs in freshwater affected by terrestrial inputs. Freshwater bodies in areas where plastics are produced are impacted by the nearby environment, indicating the presence of MPs in the water. The SEM morphological analysis of these MPs showed deterioration patterns. The EDX analysis reveals the presence of many elements, including C, O, Na, Mg, Al, Si, P, etc. C, O, Na, Al, Si, and K concentrations were elevated. In contrast, S, Cl, T, and Fe concentrations were lower.

Variations in heavy metal concentrations are seen in the Nida River water. Zn had the greatest average content of 96.86 ± 40.25 in all samples, followed by 37.6 ± 31.9. The mean turbidity, pH, and conductivity values were 46 ± 23, 7 ± 0.33, and 1338 ± 40, respectively. Water samples' turbidity, pH, and conductivity were compared with the standards of the EPA, WHO, and Polish drinking water recommendations. Generally, the criteria did not adhere to these norms. HQ values for heavy metals were below one for both adults and children. The Nida River water is safe for human consumption since the HI values are less than one, indicating a non-carcinogenic risk. The research found no significant non-carcinogenic danger from the heavy metals analyzed. However, continuous monitoring is necessary since unforeseen contamination might still occur. To conserve water resources effectively, it is crucial to identify technologies that can provide precise information on the condition of whole river courses rather than just specific places. This study has important and wide-ranging implications for the scientific community. Investigating heavy metal and MP pollution in freshwater ecosystems contributes to our knowledge of human influences on rivers. This information guides conservation efforts and provides insights into the condition of freshwater habitats, which in turn informs environmental health evaluations.