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Article

Microplastic Evaluation in Water and Sediments of a Dam Reservoir–Riverine System in the Eastern Carpathians, Romania

by
Iulian Pojar
1,*,
Oana Dobre
1,
Constantin Lazăr
1,2,
Teodora Baboș
1,
Oana Ristea
3,
Alina Constantin
3 and
Nicoleta Cristoiu
3
1
National Institute for Research and Development on Marine Geology and Geoecology-GeoEcoMar, 024053 Bucharest, Romania
2
Doctoral School of Geology, Faculty of Geology and Geophysics, University of Bucharest, 6, Traian Vuia Street, 020956 Bucharest, Romania
3
National Administration Romanian Waters, Buzău-Ialomița Water Basin Administration, 120208 Buzău, Romania
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(11), 4541; https://doi.org/10.3390/su16114541
Submission received: 5 April 2024 / Revised: 21 May 2024 / Accepted: 23 May 2024 / Published: 27 May 2024
Browse Figures
Versions Notes

Abstract

:
The complex aquatic system of dam reservoirs is known to trap emerging pollutants as microplastics (MPs) in sediments and water column. Considering the knowledge gaps in this type of environment, we investigated the amount and distribution of MPs in the surface water layer, as well as in the surface and deep sediments of the Siriu Reservoir in the Buzău River system, which is located in the southern area of the Eastern Carpathians, Romania. There was a discrepancy between MP abundancy in both water and sediment samples collected near the reservoir (5.3 MPs/m3, 315.5 MPs/kg) and at several kilometers downstream of the dam (1.4 MPs/m3, 132.5 MPs/kg). The chronological accumulation of MPs in the lacustrine sediments was determined by analyzing 5 cm intervals of a 50 cm length core extracted from the reservoir bed. By comparing the concentration of MPs identified in each interval with the solid debit volumes registered in the last decade, we found that flood events could be traced easily due to abundant MP accumulation. Morphologically, the particles were observed mainly as fibers and fragments. Fourier transform infrared spectroscopy (FT-iR) investigations identified most of the MPs as polypropylene (28%), polyethylene (26%), and polyethylene terephthalate (19%).

Graphical Abstract

1. Introduction

Plastic-based polymers have been used in all industries since 1950, and their use has improved almost all products used and consumed by humans. Due to the characteristic features of these synthetic materials, e.g., their low weight, strength, durability, corrosion-resistance, and electrical insulation [1], they have been widely used. However, plastics also have the potential to disintegrate under specific natural conditions into smaller pieces, i.e., microplastics (MPs). These particles are now recognized as one of the most problematic forms of pollution.
The reliance on plastics for a wide range of consumer products, many of which are single-use, has resulted in their constant entry into the aquatic environment [2]. Arthur et al. [1] defined MPs as small plastic beads or fragments that measure between 1 µm and 5 mm. They are currently recognized as one of the most dangerous environmental contaminants.
Over the last decade, there has been significant scientific interest in MP pollution investigations in riverine–lacustrine systems due to the poor ecological status of this type of environment [3,4,5]. Plastic pollution is currently widespread throughout the world and is regarded as one of the most serious issues in the management of aquatic resources and environmental protection [6,7,8]. Several studies have raised concerns about the possible effects of MPs on ecosystems and organisms; however, most of these studies have focused on marine environments [9,10,11,12]. Freshwater ecosystems have also been found to contain large amounts of MPs, raising concerns about the potential dangers to human health and the environment [13,14,15].
Freshwater reservoirs collect high volumes of litter, especially during intense flood periods, whereby litter accumulates in the sediments of adjacent rivers [16] and inside reservoirs on depositional banks, as well as in the surface water layer of the reservoir [17]. Although the fate and behavior of MPs in marine ecosystems has been widely studied, the transport and sedimentation processes of MPs in freshwater bodies is still not fully understood. Several studies have identified high accumulations of MPs in specific depositional areas of freshwater bodies, such as rivers [16,18,19], lakes [17,20], and dam reservoirs [4,21,22,23,24]. Moreover, Horton et al. [25] indicated that in artificial aquatic environments, the accumulation of MPs is more complicated than in completely natural systems due to the complex interaction of natural–artificial factors.
For a better understanding of MP distribution in such artificial aquatic bodies, it is necessary to assess the abundancy of this emerging pollutant, both in reservoirs and adjacent riverine environments. Few studies have addressed the characterization of MPs in dam lakes, and this study followed a similar strategy by analyzing different samples collected upstream of, downstream of, and within the reservoirs.
The overall aims of the present study were to evaluate the pollution degree of MPs in the regional basin of Buzău River, in the proximity of the Siriu Reservoir, as well as to characterize the particle features for preliminary provenance findings and spatio-temporal-related considerations. This represents a unique and innovative investigation of MP pollution in an artificial lake (reservoir)–river system located in the southern part of the Eastern Carpathians, Romania. This is the first study of MPs in the Carpathian dams and one of the few conducted so far in Europe [21,22]. MP concentrations were measured in water and sediment samples, and additionally in sediment cores.

2. Materials and Methods

2.1. Study Area

The Buzau River–Siriu Reservoir is located in the southern part of the Eastern Carpathians, in a region with approximately 10,000 residents in upstream localities. There is little agriculture in this region, but tourism, which can be a source of pollution, has significantly increased in recent years. The study area is situated in the vicinity of the United Nations’ Educational, Scientific, and Cultural Organization (UNESCO) known as Buzău Land Geopark. The study area of the Buzau River–Siriu Reservoir system (Figure 1) is in a specific sector of the river with high slope dynamics; therefore, extensive consolidation studies have been conducted along the adjacent road due to the high aquatic current velocity. The reservoir is located in a highly fragmented lithological environment that is subjected to intense erosion. Landslides are therefore common in the area, especially around the reservoir [26]. Downstream of the reservoir, the river is characterized by an increase in the water velocity and a decrease in the amount of suspended solid particles. There are also several sites with landslides and floodplains in the downstream region [26,27]. Taking into account these features, sampling was conducted by considering the sediment depositional areas, sediment type, water depth, and current velocity, based on data acquired from the “National Administration Romanian Waters” [28].

2.2. Sampling Strategy

The sampling period coincided with the flood period (November 2022), with the high debits of the Buzău River permitting a representative evaluation of MPs. Six water samples, seven sediment samples, and two sediment cores were collected (Table 1). The sediments were sampled using a standard Ekman-type grab (10/10 cm, with a volume of 0.005 m3 and a width of 5 cm, KC Denmark, Silkeborg, Denmark) for the reservoir bed (from a small boat) or a stainless-steel spatula for riverbanks. The samples were sand or silty clay and were collected from one location upstream of the reservoir, three locations in the reservoir, and three locations downstream of the reservoir (Table 1). Two 50 cm long sediment cores were collected from the same location in the northern area of the reservoir. Two cores with identical lithologies that were representative of the P4 sampling location were taken for sample volume considerations and were extracted with a corer (Hydro-Bios, Altenholz, Germany), using transparent PVC tubes. Several sites were selected for sediment sampling (mud to sand, Table 1) from the superficial layer of the bed (P3, P4, and P5). Water samples were taken using a Neustonic net (200 μm, with a 40 × 70 cm frame and a 260 cm net length, Hydro-Bios, Altenholz, Germany), and were collected from one location upstream of the reservoir, two transects in the reservoir (the net was attached to a motorboat, with a cca. speed of 3.5 km/h), and three locations downstream of the reservoir [29]. Stationary water sampling was performed by submerging half of the frame in the water (for riverine sampling). In the case of lacustrine sampling, the transects were performed by dragging the net using a boat, as we described above. The collection of the samples was conducted according to a methodology established in cooperation with the National Administration Romanian Waters.
For the estimative evaluation of the sedimentation rate in the specific location of the core sampling, we performed calculation based on the last four sediment clogging measurements realized by the National Administration Romanian Waters (Buzău—Ialomița Basin Administration) in 2002, 2006, 2009 and 2015 [28]. Due to the last dredging studies conducted before 2009, we considered using viable sedimentation data from sediment removal studies until 2015, when the last bathymetric measurements were taken. Based on the difference in the bathymetric values reported in adjacent materials of in-house reports [28], we assumed that 3.6 cm is the approximate annual sedimentation rate for the location where the core was collected.

2.3. Sample Preparation and Analytical Methods

The extraction of MPs required drying at 60 °C and sieving through 5 mm for bulk sediment samples. After gravitational separation in a saline supernatant with a density of 1.6 g/cm3 (HCO2K, 95%), most of the solid fraction was eliminated. Both water samples and the suspension extracted from sediment samples were digested in a mixture of hydrogen peroxide and potassium hydroxide (H2O2, 35% + KOH, 10M), in a volume ratio with the sample of 1:1:1 [30,31] for organic matter removal. This was mixed for 5–7 days [32,33]. After complete digestion, the samples were neutralized using formic acid (HCOOH, 95%), reaching a neutral pH (6–8). Sample filtration was performed using a vacuum pump and a Bruckner system to extract the MPs on fiberglass membranes (4.7 cm, with a pore size of 1.2 µm).

2.4. Microscopic Evaluation

The optical investigation of plastic particles was performed using a stereomicroscope (EZ4W, Leica, Wetzlar, Germany), at a magnification of 50×. The quantitative analysis of MPs referred to particles of different morphologies and colors [34]. In accordance with the MP dimensions established by Arthur et al. [1], the particles that were counted ranged between 200 µm and 5 mm. The particles were categorized into two classes: (i) particles smaller than 1 mm and (ii) particles larger than 1 mm. The MP amount was calculated as particles per cubic meter (MPs/m3) for water samples and particles per kilogram of sediment (MPs/kg).

2.5. Fourier Transform Infrared Spectroscopy (FT-iR)

The qualitative investigation of 12 fiberglass membranes was conducted at the Polytechnic University of Bucharest, the Faculty of Applied Chemistry and Material Sciences, the Department of Science and Engineering of Oxide Materials and Nanomaterials. Two scans per 2 cm from each membrane were scanned using a micro-spectroscope FT-iR (Nicolet iN10 MX, Thermo Fisher Scientific, Waltham, MA, USA). The FT-iR measurements were performed using multiple sequences of wavenumbers between 4000 and 370 cm−1, with eight co-added scans and a spectral resolution of 8 cm−1. The resulting spectra were compared with the Thermo Fisher Scientific database (Omnic Picta software, version 1.3) for polymer identification (Figure 2).

2.6. Quality Assurance and Storage

Sample storage and conservation was required during the field work to prevent the contamination of samples. Therefore, we used aluminium containers for sediment and glass jars for water samples. Although the sediment cores were kept in PVC tubes, we evaluated the contamination risk for this polymer after the qualitative investigations, in which several transparent and white PCV particles were identified.
During sample preparation, we prevented sample contamination from airborne particles and from other sources by cleaning the working space with ethanol, wearing cotton laboratory coats, and using glass and stainless-steel utensils. To control the contamination rate, in each series of filters, we included one blank sample, in which the same amount of reagent was added, and the blank was filtered in the same way as the samples. After the blank samples were visually inspected, corrections were applied to each analyzed sample.

3. Results and Discussion

In total, 4960 particles were observed from all 23 samples of water (six), sediment (seven), and sediment core intervals of 5 cm (ten). Following the normalization calculation performed after the spectroscopy measurements were taken, 4445 plastic particles were identified (89.62%). The dominant morphologies of MPs were observed as fibers (77.6%), while the other types were represented by fragments (12.1%), foils (8.7%), and spherules (1.6%) (Figure 3).
Black particles were the most common (>50%), followed by blue/green (17%), white/transparent (15.2%), red (12%), and yellow (5.3%). Particles smaller than 1 mm represented almost 65% of the total observed MPs, among which black MPs represented more than 1/3 (34.4%) of all identified particles (Figure 3).

3.1. Surface Water Layer

Although particle abundance inside the reservoir was reduced (P6 and P7: 0.6–1.1 MPs/m3), the MP concentrations upstream and downstream the reservoir (P1 and P2) were found considerably higher (4.5 and 6 MPs/m3, respectively, Figure 4). Further downstream of the dam, lower MP concentrations were determined (P8 and P9: 1.1–1.65 MPs/m3), causing the average amount to decrease to 3 MPs/m3.
Several MP abundance discordances were found between the lacustrine (Siriu Dam) and riverine (Buzău River) samples. Inside the reservoir dam, samples were taken along transects running in the SW-to-NE and W-to-E directions (P6 and P7). We identified various degrees of pollution, which likely mirrored the natural features of the area, such as wind direction and aquatic currents. Heavy-density MPs (i.e., fragments and spherules) were more abundant in these transects and in the immediate location downstream of the dam (P2) than in the other samples; hence, we assumed the presence of dynamic vectors that lifted these particles to the water surface.
For the MPs collected from the Buzău River, a higher amount was observed downstream of the dam. Although most of the particles were found as fibers in riverine samples, similar concentrations of each morphology were also observed in the dam reservoir. Because fibers were more prevalent in the water column than the other morphologies [35,36], their sources could be scattered throughout the local area or even further away due to aerial transport.
The southernmost water samples (P8 and P9) had the lowest MP concentrations, with a significant percentage of fibers and foils. The presence of these morphologies was indicative of the household sources in the adjacent localities, as well as contamination from the dam reservoir slopes, where large amounts of all types of Macrolitter were observed during the fieldwork. To consider the correlation between the MPs’ abundance–distribution and geomorphological/aquatic dynamics, the accumulation results of the bathymetric study in the Siriu Reservoir (2015) were taken into consideration.

3.2. Surface Sediments

The average MP concentration in the sedimentary superficial layer of the Buzău River and Siriu Dam was 268 MPs/kg. Contrary to the values identified in water samples, the greatest amount was found in the upstream samples (Figure 4), especially in the northern (P3, 445 MPs/kg) and central areas (P5, 357 MPs/kg). The MP concentration was lower in the sediments of the Buzău River downstream of the dam, ranging between 190 MPs/kg (P2) and 110 MPs/kg (P9).
The MP concentrations identified in the sediments collected upstream and downstream of the reservoir differed quantitatively from the water samples. In the sediments located upstream of the reservoir, we found 120 MPs/kg more than in the sample collected downstream (P1, 311 MPs/kg; P2, 190 MPs/kg). Therefore, the Siriu Dam could be considered an MP trap, as reported previously in other dam lake systems [4,21,22,23]. In addition, in the northernmost depositional area of the dam (P3), we found an anomalous abundance of foils, which were the dominant MPs. They were probably an autochthonous source of plastic, with household-derived litter contributing to the high concentrations in this area.
The sediments collected downstream of the dam had an abundance of foils and fibers. The total number of MPs identified in the riverine environment was lower than in the reservoir due to higher aquatic velocities. Regional sources (e.g., localities and roads) likely supplied the MPs, resulting in low-to-medium levels of pollution, although it must be considered that sampling took place over a period of one year with high precipitation, which likely increased the overall MP concentrations.

3.3. Sediment Core

Sedimentary MPs identified in ten 5 cm intervals (C1—top to C10—bottom) were deposited in the last decade, according to the depositional rate, which was calculated from sedimentological data provided by the National Administration Romanian Waters between 2001 and 2019, [28], located in the northern area of the reservoir. The given sedimentary rate was also verified according to data from the in-house reports of the National Administration Romanian Waters (Buzău—Ialomița Basin Administration) [28].
We assumed that each depositional interval of 5 cm tested for MP abundance was deposited over a period of 1.38 years. The average MP concentration from the core was 470 MPs/kg, but this varied with sediment depth (Figure 5). The maximum value was observed at the bottom of the core (C10, 670 MPs/kg), with two other peaks of 601 and 661 MPs/kg in C3 (a core interval of 10–15 cm) and C7 (a core interval of 30–35 cm), respectively.
The distribution of MPs fluctuated with the solid debit of the Buzău River in various time intervals (Figure 5). For example, the peaks representing a high abundance of MPs were associated with significant flood events between 2009 and 2019, which modified the debit of solid particles (data received from the National Administration Romanian Waters). According to the correlation between the annual average quantity of solid debits from the Buzău River and the MP amount of each interval, we observed that MP occurrence in the dam generally reflected the sediment mass in the waterflow: (i) the minor peak of the solid debit registered in 2010 was mirrored in the C7 interval with a high concentration of 600 MPs/kg and (ii) the increased trend of sediments in the Buzău River between 2013 and 2016 was followed by a tendency for high MP concentrations from 293 MPs/kg identified in the C5 interval to 661 MPs/kg in the C3 interval.
We found large MP concentrations in the C3 and C4 sedimentological intervals, with high percentages of spherules and fragments. The presence of these high-density particles suggested an increased current velocity, which could be correlated with flooding events. Significantly high debits of the Buzău River, and consequently solid debit, were registered in March 2018 (over 200 m3/s), which corresponded with the C2 interval. Furthermore, the lack of precipitation, especially in the spring and autumn 2013–2016 seasons, was strongly correlated with the low MP concentrations in the C4–C5 intervals.

3.4. Polymer Types

A total of 4960 particles were visually counted, of which 193, sized between 0.1 and 2 mm, were further analyzed through 30 FT-iR scans, and 173 particles were identified as plastics (89.63%). The results were obtained by analyzing 1–2 areas of each fiberglass membrane containing MP concentrates (Figure 6). The results confirmed the predominance of polypropylene (PP, 28%), polyethylene (PE, 26%), and polyethylene terephthalate (PET, 19%).
Less than 10% of the total MPs were identified as polymethylmethacrylate (PMAA), polystyrene (PS), polyvinyl chloride (PVC), and other elastomeric polymers. Most of the studied particles were foils (46%) and fragments (41%), which were identified as PP (40%), PE (39%), and PET (18%). The fibers and spherules were mainly identified as PE (35%), PP (24%), PMMA (20%), and PS (11%).

3.5. Provenance and Sources

Due to the predominant similarities observed between particles from the same classes (morphology, color, and polymeric type), it is plausible to assume that the amount of generating sources is limited [37]. As mentioned before, agricultural and touristic activities in the drainage area are reduced [26], therefore specific products from these industries were insignificant in comparison with weathered particles from household litter and car tires. The origin of each morphological type of particles identified on the overall study area (P1–P9) is estimated to be represented by the main same sources. It is reasonable to assess textile waste from the local communities as main source of the fibers [35]. Little discordances of other MP classes across the study area were observed at the distribution level of specific morphotypes and their displayed occurrence hotspots (Figure 4): (i) the main upstream distribution of flakes identified in sediments from the P3 sample and, subsequently, the P1, P4, and P5 samples can be related to the proximity of the high traffic roadway that crosses the local mountain area; (ii) the distinct accumulation of fragments observed in the downstream water sample (P2) adjacent to the dam gates indicates a high velocity of the stream and the presence of surface currents that concentrate 3-dimensional MPs at the surface water (Figure 4).

3.6. Implications

By comparing the quantitative examination to past studies of MPs in artificial lacustrine–riverine systems (Table 2), this study found an average concentration of 268 MPs/kg of sediment, and a similar concentration was also found by He et al. [23], Shen et al. [24], and Di and Wang [38]. Thus, the distribution patterns around different reservoirs from several regions [4,21,22,23,24] are the highest in dam reservoirs and see a strong decrease in abundance downstream. Considered as hotspots, the artificial lakes clearly function as traps for plastic particles, as other studies have suggested that amounts could reach up to 103 particles/kg [22,23], and, in general, concentrations up to three times higher than from downstream locations [4,23].
Regarding the MP amounts identified in water samples collected for this study, the low number of particles could be compared with natural riverine and lacustrine environments [10,16,18,31], rather than other findings in artificial reservoir–riverine systems (5500 MPs/m3; 14.5 MPs/m2) [4,21].
The impact on the environment, especially to living species present in both reservoir and fluvial environments, cannot be estimated in this study case due to the small amount of litter that enters the system and impacts the ingestion rate of the fauna. However, current findings may be seen as preliminary data for future studies in the area, especially in the hydrodynamic context of MP distribution [40,41] in a river–reservoir system [21]. Moreover, available data regarding the degree of historical MP pollution from sedimentological core evaluations are scarce. Therefore, a monitoring evaluation of MPs in water and sediments in reservoir systems is needed in order to improve our understanding of the geomorphological impacts of the transport and accumulation of particles, considering that the evolution of river–reservoir systems is rapidly changing [23].

4. Conclusions

MPs suspended in the surface water layer of a lacustrine–riverine environment were identified with an average concentration of 3 MPs/m3. The highest concentration was observed in the Buzău River, upstream of the Siriu Reservoir, while the minimum concentration was observed in the southern area of the dam. Sedimentary MPs had an average concentration of 268 MPs/kg, with the highest amount recorded in the northern part of the reservoir and further upstream. Thus, the MP concentration in both water and sediment samples indicated hotspots of accumulation in (1) the area in which the river entered the reservoir and (2) downstream of the dam.
Spectrometry results achieved by scanning areas of fiberglass membranes revealed the predominance of PP (28%), PE (26%), and PET (19%). Less than 10% of the total MPs were identified as PMMA, PS, and PVC.
Most MPs were fibers or flakes, and the dominant polymers identified were PP, PE, and PET, which were typically present as black particles. Therefore, we assumed that MPs were located in the proximity of the sampling points. The amount of MPs originating from vehicle tires and textile products suggested low-to-medium levels of pollution from households and local roads, taking into account the high aquatic deposits of the Buzău River.

Author Contributions

I.P.: conceptualization, methodology, writing—original draft, investigation, data curation, formal analysis, visualization, supervision, and writing—reviewing and editing. O.D. and T.B.: methodology and formal analysis. C.L.: writing—original draft, data curation, visualization, and writing—reviewing and editing. O.R., A.C. and N.C.: methodology, formal analysis, and visualization. All authors have read and agreed to the published version of the manuscript.

Funding

Financial support was provided by the Research Project of Excellence AMBIACVA, No. 23PFE/30.12.2021 and by the CORE Programme Project PN 23 30 01 02 of the Romanian Ministry of Research. This project was also funded with support from the European Commission through the Black Sea Basin Programme 2014–2020.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Acknowledgments

The authors would like to acknowledge Contracts 846c and 847c, which ran alongside the main project and was termed “Protect-Streams-4-Sea” BSB 963. This publication reflects the views of the authors only, and the Commission cannot be held responsible for any use which may be made of the information contained therein. This research was made possible through the support of the Romanian Ministry of Research, under the CORE Programme project PN 23 30 01 02, and the Research Project of Excellence AMBIACVA, No. 23PFE.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

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Figure 1. The study area of the Buzău River–Siriu Reservoir and the sampling locations (red dots). Study area (yellow dot) reported to the Eastern Europe map. Image source and background data: www.OpenStreetmap.org (accessed on 22 April 2023).
Figure 1. The study area of the Buzău River–Siriu Reservoir and the sampling locations (red dots). Study area (yellow dot) reported to the Eastern Europe map. Image source and background data: www.OpenStreetmap.org (accessed on 22 April 2023).
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Figure 2. The main FT-iR spectra (Omnic Picta software, version 1.3) used for polymeric identification of particles measured with FT-iR (Nicolet iN10 MX, Thermo Fisher Scientific) on 2 cm2 areas of several membranes.
Figure 2. The main FT-iR spectra (Omnic Picta software, version 1.3) used for polymeric identification of particles measured with FT-iR (Nicolet iN10 MX, Thermo Fisher Scientific) on 2 cm2 areas of several membranes.
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Figure 3. Morphological and color characterization of MPs identified in water and sediment samples (including core sediment intervals).
Figure 3. Morphological and color characterization of MPs identified in water and sediment samples (including core sediment intervals).
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Figure 4. Map of the study area, showing MP abundance, distribution, and morphological characterization from the surface water layer and sediment samples. Image source and background data: Google Earth Pro (accessed on 8 February 2023).
Figure 4. Map of the study area, showing MP abundance, distribution, and morphological characterization from the surface water layer and sediment samples. Image source and background data: Google Earth Pro (accessed on 8 February 2023).
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Figure 5. Microplastic abundance (orange line) in each sedimentological interval of the core (5 cm per interval, with a total length of 50 cm) vs. annual average solid debit (blue line, data received from the National Administration Romanian Waters) in the Buzău River at Nehoiu (2009–2019).
Figure 5. Microplastic abundance (orange line) in each sedimentological interval of the core (5 cm per interval, with a total length of 50 cm) vs. annual average solid debit (blue line, data received from the National Administration Romanian Waters) in the Buzău River at Nehoiu (2009–2019).
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Figure 6. Optical images and FT-iR spectrometry scans of membrane filters. Microphotographs (1–6) were taken with a stereomicroscope on the precise location marked with a red cross on the adjacent FT-iR scans (a–f) of 2 cm2 each.
Figure 6. Optical images and FT-iR spectrometry scans of membrane filters. Microphotographs (1–6) were taken with a stereomicroscope on the precise location marked with a red cross on the adjacent FT-iR scans (a–f) of 2 cm2 each.
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Table 1. Sampling details and GPS localization of water and sediment samples. Used abbreviations: s—sediment; c—sediment core; a—water; T—transect.
Table 1. Sampling details and GPS localization of water and sediment samples. Used abbreviations: s—sediment; c—sediment core; a—water; T—transect.
Sample TypeSampleSampling Date (d.m.y) & Time (h:m)Depth (m)GPS CoordonatesSediment Lithology/Filtered Water Volume (m3)
LongitudeLatitude
Surface sedimentP1s17.11.2021; 14:050.1026°11′52.6″45°31′53.1″sand
P2s17.11.2021; 15:400.1026°15′23.7″45°29′15.6″sand
P3s18.11.2021; 9:551.5026°11′59.22″45°31′38.94″siltic sand
P4s18.11.2021; 10:042.0026°12′0.72″45°31′29.52″siltic mud
P5s18.11.2021; 11:252.5026°13′30.96″45°30′48.58″mud
P8s19.11.2021; 9:270.3026°19′1.52″45°24′26.85″sand
P9s19.11.2021; 10:400.5026°22′15.41″45°18′14.82″sand
CoreP4c18.11.2021; 10:102.0026°12′0.72″45°31′29.52″siltic mud
Surface water layerP1a17.11.2021; 14:050.1026°11′52.6″45°31′53.1″131.6
P2a17.11.2021; 15:400.1026°15′23.7″45°29′15.6″136.36
P6T18.11.2021; 12:50>5.0026°14′55.93″–26°14′45.13″45°29′54.82″–45°29′44.02″403.2
P7T18.11.2021; 13:10>5.0026°14′54.55″–26°14′25.31″45°29′54.27″–45°29′51.44″417.76
P8a19.11.2021; 9:270.3026°19′1.52″45°24′26.85″579.6
P9a19.11.2021; 10:400.5026°22′15.41″45°18′14.82″281.4
Table 2. Comparison of MP concentrations in different dam reservoir sediments.
Table 2. Comparison of MP concentrations in different dam reservoir sediments.
Abundance in SedimentsLocationEnvironmentRefs.
items/Kg
268Siriu Reservoir—Buzău River, RomaniaRiver and Reservoir system This study
324.5  ±  187.6Shaying River Basin, ChinaBasin level with damsShen et al., 2023 [24]
310–2620Wujiang river basin, ChinaCascade dams systemHe et al., 2022 [23]
~104Villerest reservoir, Loire R., FranceRiver and Reservoir system Dhivert et al., 2022 [22]
1835Danjiangkou Reservoir, ChinaLacustrineLin et al., 2021 [39]
89.02 ± 20.96Fall Creek & Six Mile Creek, USARiver and Reservoir systemsWatkins et al., 2019 [21]
25-300Three Gorges Reservoir, ChinaRiver and Reservoir systemsDi & Wang, 2018 [38]
items/km2
3407–13,617Three Gorges Dam, Yangtze River basin, ChinaRiver and Reservoir systemsZhang et al., 2015 [4]
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Pojar, I.; Dobre, O.; Lazăr, C.; Baboș, T.; Ristea, O.; Constantin, A.; Cristoiu, N. Microplastic Evaluation in Water and Sediments of a Dam Reservoir–Riverine System in the Eastern Carpathians, Romania. Sustainability 2024, 16, 4541. https://doi.org/10.3390/su16114541

AMA Style

Pojar I, Dobre O, Lazăr C, Baboș T, Ristea O, Constantin A, Cristoiu N. Microplastic Evaluation in Water and Sediments of a Dam Reservoir–Riverine System in the Eastern Carpathians, Romania. Sustainability. 2024; 16(11):4541. https://doi.org/10.3390/su16114541

Chicago/Turabian Style

Pojar, Iulian, Oana Dobre, Constantin Lazăr, Teodora Baboș, Oana Ristea, Alina Constantin, and Nicoleta Cristoiu. 2024. "Microplastic Evaluation in Water and Sediments of a Dam Reservoir–Riverine System in the Eastern Carpathians, Romania" Sustainability 16, no. 11: 4541. https://doi.org/10.3390/su16114541

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