The Vistula Lagoon is the second largest, semi-enclosed lagoon in the Baltic Sea (838 km2). Due to its unique natural values, the lagoon was included in the network of Marine Protected Areas in the Baltic Sea (HELCOM 2016) and Natura 2000 sites in the European Union (Special Protection Area PLB290010 under the Birds Directive: Directive 2009/147/EC of the European Parliament and of the Council of 30 November 2009 on the conservation of wild birds; Special Area of Conservation PLH280007 under the Habitats Directive: Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora). At the same time, the Vistula Lagoon is exposed to various pressures, including those related to tourism and fishery, as well as pollution originating from land. A very important issue in terms of the environmental status of this unique basin is a plan to build a new navigable canal through the Vistula Spit, which will connect the lagoon waters with the Gulf of Gdańsk. The aim is to intensify shipping and increase its share in both the economic and tourism sector. Such a project may significantly affect the environmental conditions of the lagoon, e.g. through contamination with hazardous substances like heavy metals. Deepening of the shipping canal involves the necessity of disturbing sediments, which may result in the secondary release of pollutants present in sediments. The project is particularly relevant when considering obligations under EU legislation: the Water Framework Directive (Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy), which is the key directive on water protection and defines the principles of water policy; and the Marine Strategy Framework Directive (Directive 2008/56/EC of the European Parliament and of the Council of 17 June 2008 establishing a framework for Community action in the field of marine environmental policy). The Vistula Lagoon is a transitional water body and as such is subjected to all activities related to the implementation of both directives. It is therefore necessary to conduct research to increase knowledge about the distribution of pollutants in particular elements of the lagoon’s environment, taking into account their potential sources. Such research should be aimed at supporting the decisions regarding management and protection of the Vistula Lagoon.
The research described in this paper was aimed at determining the concentrations of heavy metals in selected species of macrophytes (aquatic plants) that are most typical of the Vistula Lagoon. Macrophytes are among the most sensitive and reliable bioindicators, including contamination levels (Bojanowski 1973; Szefer & Skwarzec 1988; Haroon & Szaniawska 1995; Kruk-Dowgiałło & Pempkowiak 1995; Rainbow 1995; Leal et al. 1997; Ostapczuk et al. 1997; Malea & Haritonidis 2000; Szefer 2002a,b; Sawidis et al. 2003; Burger 2006; Żbikowski et al. 2007; Zalewska & Saniewski 2011; Zalewska 2012a,b; Zalewska & Suplińska 2012; Alquezar et al. 2013; Chakraborty et al. 2014; Zalewska 2015; Farias et al. 2018; Sinaei et al. 2018). This is mainly due to their ability to exchange elements with the surrounding environment. The exchange in macroalgae takes place through their thalli, uptaking elements directly from water, while in vascular plants mostly through their root system. In both cases, concentrations of contaminants in plants reflect levels in their nearest environment (water), which facilitates the interpretation of data, and additionally, the response of plants to changes in the environment is very fast. The most valuable feature is that concentrations of pollutants in plants reflect the condition of the basin.
On the basis of the obtained results, factors of heavy metal concentrations were calculated. They indicate the ability of individual species to accumulate heavy metals, which can be used to assess the environmental status and to predict changes in the environment.
The objective of the present paper was also to describe changes in heavy metal concentrations in the historical aspect, which was accomplished by analyzing changes in heavy metal concentrations in sediment cores in relation to the age of particular sediment layers. The sedimentation rate of bottom sediments in the Vistula Lagoon was also determined.
The results presented in the paper may serve as a basis for predicting the distribution of heavy metals also in other sea areas with similar environmental characteristics as the Vistula Lagoon. The results are also a baseline for potential changes in the environment caused by the canal in the Vistula Spit. This investment may affect directly and indirectly (by increasing pressure) hydrological, physicochemical and biological characteristics, which consequently may affect concentration levels and distribution of heavy metals in the Vistula Lagoon ecosystem.
The Vistula Lagoon is a brackish water ecosystem with salinity ranging from 0.3 near estuaries up to 6.5 near the strait connecting with the Baltic Sea (Fig. 1). The basin is vast and shallow with an average depth of 2.7 m and a maximum depth of 5.2 m. The bottom is morphologically undifferentiated, muddy sediments prevail and cover deeper parts of the lagoon. Sandy shoals stretch along the coast to a maximum depth of 2 m (Chubarenko & Margoński 2008). These are the only areas with macrophytes. The vegetation consists mainly of
The mineral incrustation of Charophyta specimens was not removed. In general, the incrustation can serve as an additional source of contaminants in plants (along with bioaccumulation), but species occurring in saline environments are less encrusted compared to specimens from freshwater (Urbaniak 2010). Therefore, it was assumed that the effect of incrustation on the final results of this study can be neglected.
For the purpose of heavy metal determination, three parallel cores of about 40 cm length were collected; each of them was divided into 2 cm slices to a depth of 10 cm, and at greater depths, 2 cm slices were selected at every 5 cm of the core length. Eventually, the three parallel cores were divided into the following samples: 0–2 cm, 2–4 cm, 4–6 cm, 6–8 cm, 8–10 cm, 15–17 cm, 22–24 cm, 29–31 cm and 36–38 cm. The selection of sediment layers and the number of samples sufficient to assess heavy metal distribution in the sediment core was based on the experience gained from the Baltic Sea monitoring. Wet sediment samples were preserved by deep-freezing on board the vessel and then freeze-dried, homogenized and stored for further analysis in the laboratory. Analyzes of metals in sediments were carried out as part of the State Environmental Monitoring coordinated by the Chief Inspectorate for Environmental Protection financed from the National Fund for Environmental Protection and Water Management.
Three additional parallel sediment cores were collected at the sampling location to determine the age of the sediment. The cores were divided into 2 cm wide slices to a depth of 50 cm. The corresponding slices/layers from the three parallel cores were integrated to produce a single analytical sample. These samples were initially deep-frozen on board the ship and freeze-dried and homogenized in the laboratory prior to analysis.
On the basis of the obtained results, the concentration factors of heavy metals were calculated. They indicate the ability of individual macrophyte species to accumulate heavy metals, which can be used to assess the environmental status and to predict changes in the environment.
The content of mercury in the sediments was determined using cold vapor atomic absorption spectrometry in an AMA 254 mercury analyzer. A sample (ca. 100 mg) was placed in a combustion chamber of the analyzer, where it was dried and burned in an oxygen flame at 600ºC. The released mercury was collected in a gold amalgam catalyst. After the sample decomposition was completed, the temperature was stabilized at 120ºC and the content of mercury was measured with a detection limit of 0.05 ng.
The accuracy and precision of measurements were controlled using a certified reference material (Table 1), analyzed parallel to sediment samples.
Results of the analysis of the certified reference materials
Cd | Pb | Zn | Cu | Ni | Cr | Mn | Hg | ||
---|---|---|---|---|---|---|---|---|---|
mg kg−1 d.w. | |||||||||
BCR-414 |
Certified | 0.383 ± 0.014 | 3.97 ± 0.19 | 111.6 ± 2.5 | 29.5 ± 1.3 | 18.8 ± 0.8 | 23.8 ± 1.2 | 299 ± 13 | - |
Measured | 0.37 | 3.84 | 109.59 | 28.9 | 19.2 | 22.6 | 287 | - | |
RSD | 0.098 | 0.029 | 0.035 | 0.009 | 0.113 | 0.087 | 0.017 | 0.098 | |
LOD | 0.0015 | 0.03 | 0.012 | 0.012 | 0.015 | 0.02 | 0.01 | 0.0015 | |
LOQ | 0.005 | 0.10 | 0.035 | 0.035 | 0.045 | 0.06 | 0.03 | 0.005 | |
MESS-4 |
Certified | 0.28 ± 0.04 | 21.5 ± 1.2 | 147 ± 6 | 32.9 ± 1.8 | - | - | - | 0.08 ± 0.06 |
Measured | 0.26 | 20.1 | 143 | 31.8 | - | - | 0.08 | ||
RSD | 0.056 | 0.022 | 0.012 | 0.037 | 0.006 | ||||
LOD | 0.0015 | 0.07 | 0.007 | 0.012 | 0.001 | ||||
LOQ | 0.005 | 0.20 | 0.020 | 0.035 | 0.003 |
210Pb identified in sediment samples originates from two sources. A certain fraction is the result of radium (226Ra) radioactive decay and this is called supported 210Pb (210Pbsupp). Its activity along the vertical sediment profile practically does not change. The other source of 210Pb deposited in marine sediments is atmospheric fallout. The activity of 210Pb unsupported or excess (210Pbex), originating from atmospheric deposition, decreases with the sediment depth. This activity constitutes the basis for determining sediment accumulation rates: the mass accumulation rate (MAR) and the linear accumulation rate (LAR) and for determining the age of particular sediment layers. The 210Pbex activity concentration is determined from the total activity of this isotope (210Pbtot) in the analyzed layer by subtracting the activity of one of the products of 226Ra decay, e.g. 214Bi or 214Pb. In the present study, sedimentation rates and sediment age along the vertical profiles were determined using two models: the Constant Rate of Supply (RSC) model and the Constant Flux Constant Sedimentation Rate (CF:CS) model (Appleby & Olfield 1992; Appleby 1997; Boer et al. 2006; Diaz-Asencio et al. 2009; Szmytkiewicz & Zalewska 2014).
In order to verify the results of age determination by the 210Pb method, it is necessary to apply an additional tag whose concentration changes in the marine environment can be easily documented in relation to specific events. In the case of the Baltic Sea, the most obvious tag is the totally anthropogenic isotope of cesium – 137Cs. When verifying the age determination method based on 137Cs, it is assumed that the described historical events (e.g. testing of nuclear weapons performed since 1945 with maximum deposition recorded in 1963 and the accident at the Chernobyl power plant, Ukraine, in 1986) should be well marked as an increase in the curve of isotope changes along the sediment core. At the same time, the results have to be interpreted with caution, taking into account the complexity and the large number of processes affecting the final result – the presentation of 137Cs distribution in the sediment vertical profile. Therefore, the isotope could be useful for verifying sediment chronology when post-depositional processes are not affecting this radionuclide (Diaz-Asencio et al. 2009).
Green algae
Concentrations of heavy metals and 137Cs in macroalgae and vascular plants at the sampling locations in the Vistula Lagoon in 2011
Species | Sampling location |
Cd | Pb | Zn | Cu | Ni | Cr | Mn | 137Cs | |
---|---|---|---|---|---|---|---|---|---|---|
mg kg−1 d.w. | Bq kg−1 d.w. | |||||||||
9 (1) | value | 0.93 | 5.5 | 645.4 | 8.0 | 9.6 | 0.08 | 2706 | < 6.0 | |
10 (5) | mean mean value based on the number of samples given in brackets |
0.84 | 4.2 | 430.1 | 5.0 | 4.7 | 0.18 | 3605 | 3.0 ± 1.4 | |
min. | 0.41 | 2.9 | 327.3 | 3.5 | 4.2 | 0.11 | 2208 | |||
max | 1.24 | 5.2 | 651.8 | 8.2 | 5.5 | 0.28 | 5485 | |||
12 (5) | mean mean value based on the number of samples given in brackets |
0.67 | 3.2 | 307.7 | 6.7 | 3.2 | 0.60 | 1553 | 6.4 ± 3.5 | |
min. | 0.30 | 1.4 | 107.3 | 1.7 | 0.1 | 0.12 | 996.8 | |||
max | 1.23 | 5.7 | 653.0 | 12.0 | 8.9 | 1.08 | 2182 | |||
13 (4) | mean mean value based on the number of samples given in brackets |
0.42 | 4.6 | 242.3 | 6.4 | 3.2 | 0.86 | 10315 | 5.3 ± 2.1 | |
min. | 0.35 | 2.4 | 186.2 | 5.9 | 1.0 | 0.72 | 5063 | |||
max | 0.53 | 6.6 | 293.2 | 7.0 | 5.5 | 0.99 | 12840 | |||
12 (1) | value | 0.65 | 1.8 | 390.5 | 3.2 | 0.41 | 0.51 | 383.4 | < 3.0 | |
6 (1) | value | 0.38 | 1.2 | 175.4 | 4.9 | 1.4 | 0.93 | 673.4 | < 5.2 | |
10 (2) | mean mean value based on the number of samples given in brackets |
0.20 | 1.0 | 187.8 | 3.7 | 1.0 | 0.70 | 784.6 | < 2.1 | |
min. | 0.12 | 0.69 | 108.2 | 2.9 | 0.15 | 0.65 | 782.8 | |||
max | 0.28 | 1.3 | 267.5 | 4.4 | 1.8 | 0.75 | 786.5 | |||
12 (2) | mean mean value based on the number of samples given in brackets |
0.20 | 0.56 | 136.2 | 4.2 | 1.7 | 0.89 | 1255 | < 5.5 | |
min. | 0.16 | 0.09 | 67.8 | 3.1 | 1.2 | 0.56 | 634.7 | |||
max | 0.24 | 1.02 | 204.6 | 5.3 | 2.3 | 1.22 | 1874 | |||
13 (1) | value | 0.39 | 1.7 | 177.4 | 4.3 | 2.3 | 0.85 | 3950 | < 5.2 | |
17 (1) | value | 0.25 | 3.5 | 130.4 | 5.4 | 5.5 | 1.13 | 10035 | 7.3 ± 1.6 | |
10 (6) | mean mean value based on the number of samples given in brackets |
0.25 | 0.58 | 195.6 | 2.7 | 3.3 | 0.75 | 1697 | 0.9 ± 0.5 | |
min. | 0.22 | 0.20 | 157.3 | 1.2 | 0.81 | 0.36 | 965.6 | |||
max | 0.28 | 1.3 | 242.1 | 8.7 | 14.4 | 2.34 | 2709 | |||
12 (1) | value | 0.13 | 0.28 | 58.5 | 1.3 | 0.76 | 0.30 | 694.9 | < 0.7 | |
6 (1) | value | 0.39 | 1.1 | 61.5 | 4.7 | 1.7 | 1.45 | 919.5 | < 2.0 | |
12 (1) | value | 0.10 | 0.72 | 52.2 | 1.2 | 0.69 | 0.39 | 463.7 | < 2.0 | |
17 (2) | mean mean value based on the number of samples given in brackets |
0.39 | 5.0 | 179.2 | 8.3 | 4.1 | 2.79 | 8543 | 7.9 ± 3.5 | |
min. | 0.26 | 4.7 | 116.1 | 7.2 | 2.6 | 2.39 | 8259 | |||
max | 0.52 | 5.4 | 242.2 | 9.4 | 5.5 | 3.19 | 8828 | |||
12 (1) | value | 0.63 | 1.8 | 391.8 | 6.3 | 1.1 | 2.22 | 772.3 | < 7 | |
10 (1) | value | 0.05 | 1.9 | 28.6 | 5.0 | 6.8 | 1.79 | 738.4 | 4.9 ± 0.6 |
The Kruskal–Wallis test showed statistically significant differences between the locations only in the case of
When comparing the average concentrations of heavy metals (calculated on the basis of all data for a particular taxon; Table 2, Fig. 3), one should consider the way the elements are exchanged with the environment, which is one of the key factors affecting the bioaccumulation. In the case of macroalgae, which in the Vistula Lagoon were represented by green algae
Concentrations of Cd, Pb, Cu and Ni in
The ranges of heavy metal concentrations in macrophytes collected in the Vistula Lagoon in 2011 (Cd: 0.1–1.2 mg kg−1 d.w.; Pb: 0.1–5.7 mg kg−1 d.w.; Zn: 29–653 mg kg−1 d.w.; Cu: 1.2–12.0 mg kg−1 d.w.; Ni: 0.1–14.4 mg kg−1 d.w.; Cr: 0.1–3.2 mg kg−1 d.w.) are comparable to the concentration ranges of the same metals determined in the vegetation from the Puck Lagoon in 1989 and 1990 (Cd: 0.4–8.0 mg kg−1 d.w.; Pb: 0.2–7.5 mg kg−1 d.w.; Zn: 170–910 mg kg−1 d.w.; Cu: 5.5–14.0 mg kg−1 d.w.; Ni: 1.3–11.0 mg kg−1 d.w.; Cr: 0.7–6.7 mg kg−1 d.w.; Mn: 100–1400 mg kg−1 d.w.; Kruk-Dowgiałło & Pempkowiak 1995). The exception is Mn: 380–10035 mg kg−1 d.w., the concentration of which in the Puck Lagoon remained in the range of 100–1400 mg kg−1 d.w.
Based on the concentrations of heavy metals in water of the Vistula Lagoon (data from the State Environmental Monitoring in Poland in 2012, 2014 and 2016), the concentration ratios (
Concentration ratios for heavy metals in macrophytes studied in the Vistula lagoon in 2011
Concentration Ratio ( |
Cd | Pb | Zn | Cu | Ni | Cr | Hg |
---|---|---|---|---|---|---|---|
2.7 × 104 | 8.2 × 103 | 6.0 × 104 | 1.9 × 103 | 1.4 × 103 | 1.0 × 103 | - | |
2.6 × 104 | 3.6 × 103 | 6.6 × 104 | 9.9 × 102 | 1.4 × 102 | 1.0 × 103 | - | |
1.0 × 104 | 2.7 × 103 | 2.7 × 104 | 1.4 × 103 | 6.9 × 102 | 1.7 × 103 | - | |
9.2 × 103 | 1.1 × 103 | 3.0 × 104 | 7.9 × 102 | 9.8 × 102 | 1.4 × 103 | - | |
9.7 × 103 | 1.8 × 103 | 9.6 × 103 | 9.2 × 102 | 4.0 × 102 | 1.8 × 103 | - | |
1.6 × 104 | 1.0 × 104 | 3.0 × 104 | 2.6 × 103 | 1.4 × 103 | 5.6 × 103 | - | |
2.5 × 104 | 3.5 × 103 | 6.6 × 104 | 2.0 × 103 | 3.6 × 102 | 4.4 × 103 | - | |
2.0 × 103 | 3.8 × 103 | 4.8 × 103 | 1.6 × 103 | 2.3 × 103 | 3.6 × 103 | - | |
Concentration in water data from the State Environmental Monitoring in Poland in 2012, 2014 and 2016 |
2.5 × 10-5 | 5.0 × 10-4 | 5.9 × 10-3 | 3.2 × 10-3 | 3.0 × 10-3 | 5.0 × 10-4 | 3.1 × 10-6 |
Distribution Coefficient |
2.12 × 104 | 2.46 × 104 | 1.60 × 104 | 5.25 × 103 | - | - | 3.87 × 104 |
As in the case of aquatic vegetation, the elements are accumulated directly from water through thalli or the root system, values of concentration ratios express the bioaccumulation ability of selected species. In the case of Cd and Zn in most of the studied species, the CR values were at the level of 104; only for
The content of cesium 137Cs in the vegetation was relatively low, often not exceeding the detection limit of the applied method (Table 2). The 137Cs activity in
Based on changes in 210Pbex activity concentrations along the depth profile in bottom sediments (Fig. 4), a linear sedimentation rate was determined at 3.3 mm y−1 applying the CF:CS model. This value is slightly higher than that observed in the Gulf of Gdańsk (1.8 mm y−1; Zalewska et al. 2015) and may be related to the difference in the weight of matter suspended in the waters of both basins. Such a linear sedimentation rate was reflected in the mass accumulation rate (0.074 g cm−2 y−1), which was also higher than that observed in the Gulf of Gdańsk (0.032 g cm−2 y−1; Zalewska et al. 2015).
The determination of the age of sediment layers, verified by 137Cs distribution analysis in the vertical profile (Fig. 4), made it possible to trace changes in metal concentrations in the historical aspect. The deepest layer at a depth of 30 cm was formed around 1920. The concentrations of metals in this layer were as follows: Cd – 0.44 mg kg−1 d.w., Pb – 19.9 mg kg−1 d.w., Hg – 0.08 mg kg−1 d.w., Zn – 103 mg kg−1 d.w. and Cu – 27.4 mg kg−1 d.w. (Fig. 5). Metal concentrations were normalized to 5% Al content in order to avoid discrepancies resulting from differences in the composition of sediments. The content of Al in the layers of sediments ranged from 4.29% to 5.33%, with slightly higher concentrations characteristic for the deepest layers. Concentrations of Cd and Hg increased from 1923 to 1968 by 24% and 19%, respectively. Subsequently, a significant increase was observed until the maximum concentrations were reached in 1988 for Cd (0.75 mg kg−1 d.w.) and in 2000 for Hg (0.14 mg kg−1 d.w.). In the following years, the Cd concentration declined to 0.61 mg kg−1 d.w. in 2011, while the Hg concentration was relatively stable. A slightly different pattern was found in the content of Pb, Cu and Zn, which remained practically unchangeable in the period of 1923–1968. After 1968, the content of Zn insignificantly increased to the maximum value of 120 mg kg−1 d.w. in 1988, while in the following years the concentration was at a similar level. In the case of Cu, a decline in its concentration was observed until 2000. Later on, the Cu content reached a fairly stable value of ca. 19 mg kg−1 d.w. A well-marked drop in Pb concentrations occurred after 1987 and was related to the introduction of unleaded petrol in Poland in 1986. In 2011, the concentration of lead was 14.2 mg kg−1 d.w.
Taking into account the age of particular sediment layers, the content of heavy metals in the layer dated at 1994 was compared with concentrations of metals in the surface layer of sediments collected in 1995 in the Vistula Lagoon (Szefer et al. 1999). For the purpose of comparison, data from the location nearest to the location under study were selected. Concentrations of Cd, Zn and Cu were similar. Their content was as follows: Cd – 0.70 mg kg−1 d.w. (this study) and 0.69 mg kg−1 d.w. (Szefer et al. 1999), Zn – 112 mg kg−1 d.w. and 114 mg kg−1 d.w., Cu – 21.2 mg kg−1 d.w. and 20.6 mg kg−1 d.w. A significant difference was found in the concentration of lead – 19.9 mg kg−1 d.w. in the sediment layer dated at 1994, while 30.2 mg kg−1 d.w. according to Szefer et al. (1999). Very similar values were recorded in another study conducted by Glasby et al. (1998) in the Vistula Lagoon. They showed that metal concentrations were as follows: Cd – 0.9 mg kg−1 d.w., Pb – 33 mg kg−1 d.w., Zn – 111 mg kg−1 d.w. and Cu – 23 mg kg−1 d.w.
Based on the values of metal concentrations in the sediments and waters of the Vistula Lagoon, distribution coefficients
The Vistula Lagoon, a basin very sensitive to human pressure, is one of the transitional water bodies in the Polish sector of the Baltic Sea, whose environmental status is assessed in accordance with the recommendations of the Water Framework Directive and the Marine Strategy Framework Directive.
The environmental status of the Vistula Lagoon was assessed based on the obtained data on heavy metal concentrations in macrophytes and bottom sediments. The concentrations were referred to the threshold values defining the borderline between good and inadequate status, which basically means that concentrations of heavy metals below the specified value should not negatively affect the functioning of the ecosystem.
Taking into account the average concentrations of Cd (0.4 mg kg−1 d.w.), Pb (2.6 mg kg−1 d.w.) and Ni (3.2 mg kg−1 d.w.) calculated for all the studied macrophyte taxa and environmental quality standards (EQS) determined for plants (Pb – 26 mg kg−1 d.w., Cd –33 mg kg−1 d.w., Ni – 32 mg kg−1 d.w.; Zalewska & Danowska 2017), the environmental status of the Vistula Lagoon was assessed as good. In order to assess the status based on heavy metal levels in sediments, the most recent data were used, i.e. concentrations detected in the first sediment layer: Cd – 0.53 mg kg−1 d.w., Pb – 12.3 mg kg−1 d.w., Hg – 0.12 mg kg−1 d.w., Zn – 94.2 mg kg−1 d.w. Comparison of these data with the threshold values, determined through geochronological analyses carried out in the Gulf of Gdańsk (Cd – 0.3 mg kg−1 d.w., Pb – 30 mg kg−1 d.w., Hg – 0.05 mg kg−1 d.w., Zn – 110 mg kg−1 d.w.; Zalewska et al. 2015), revealed that only Pb and Zn indicated good environmental status of the sediments, while Hg and Cd indicated that the environmental status of the Vistula Lagoon is bad.
The study showed no significant differences in the concentrations of heavy metals and 137Cs between the taxa of macrophytes in the Vistula Lagoon. The concentrations of heavy metals in the macrophyte taxa varied in the following ranges: Cd – 0.1–0.7 mg kg−1 d.w., Pb – 0.5–5.0 mg kg−1 d.w.; Zn – 29–390 mg kg−1 d.w.; Cu – 2.5–8.3 mg kg−1 d.w.; Ni – 0.4–6.8 mg kg−1 d.w.; Cr – 0.5–2.8 mg kg−1 d.w.; Mn – 380–8500 mg kg−1 d.w. The lowest activity concentration of 137Cs was below the determination limit of 0.7 Bq kg−1 d.w. and the highest one reached 7.9 Bq kg−1 d.w.
No effect of rivers flowing into the Vistula Lagoon on the concentrations of heavy metals in the area was observed.
The linear sedimentation rate in the Vistula Lagoon was 3.3 mm y−1.
Since the 1990s, a decline or stable state of heavy metal concentrations in bottom sediments has been observed, reflecting changes in the environment of the Vistula Lagoon.
The environmental status of the Vistula Lagoon can be considered good in terms of heavy metal contamination, except for Hg and Cd, whose concentrations in the sediments slightly exceed the threshold value.
Concentration ratios (CR) calculated for macrophytes and distribution coefficients (
The results presented in the paper can serve as a baseline for assessing changes in the environmental status of the Vistula Lagoon, which may occur as a result of building a new navigable canal through the Vistula Spit.