Dynamics of mercury content changes in snow in the heating season on the example of the city of Siedlce
Publicado en línea: 29 mar 2019
Páginas: 19 - 24
DOI: https://doi.org/10.2478/oszn-2019-0004
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© 2019 Joanna Jabłońska, Mariusz Kluska, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
According to the report of the European Environment Agency, the air in Poland is one of the most polluted, particularly in the regions of Silesia and Małopolska (Lesser Poland). Despite the increase in expenditures on air protection, air pollution still exceeds the limits and guidelines of the EU and the World Health Organization. The countries of Central and Eastern Europe are among those with the highest number of premature deaths related to poor air quality. In the case of Poland, the number of deaths per year is about 44,000. Poland is followed in this respect by: Kosovo, Bulgaria, Serbia, Macedonia and Hungary
In addition to the various harmful particulates (SPM) and benzo(a)pyrene present in the air, mercury is a very serious pollutant. The amount of mercury emitted into the air as a result of coal pollution is determined by the amount of this fuel burnt. About 80 M tonnes of hard coal is burnt annually in Poland, of which 40 M tonnes are used to produce electric energy, and 60 M tonnes for lignite. These quantities contain more than 20 tonnes of mercury
The production of energy and industry are by far the largest source of emissions of this element, which, together with rain and snow, falls to the Earth’s surface. Despite significant emission limitations caused by technological constraints, legal standards and the implementation of EU recommendations, mercury is common in the environment in all its components and entire trophic chains. It is not biodegradable and creates many toxic compounds, both inorganic and organic ones. It penetrates the human body in significant quantities [Dmuchowski et al. 2018, Kowalski et al. 2007, 2015; Siudek et al. 2016a, Zioła-Frankowska et al. 2017].
Mercury is highly volatile; at a temperature of 20°C, the content of mercury in the air is about 14 mg/m3. The permitted concentration considered safe is 0.05 mg/m3 of air. Mercury and most of its compounds are common and highly toxic pollutants of the environment. It can be methylated by microorganisms into very toxic dimethylmercury when released into the aquatic environment. There is therefore a legitimate necessity to primarily protect air and water from pollution. Protection should start with research [Borzyszkowski, Gworek 2016, Gworek et al. 2017, Kluska et al. 2007, Siudek et al. 2016b]. Mercury is emitted by chimneys at zero oxidation, which is easily released into the atmosphere and can oxidise into Hg(II), and in the ionic form Hg2+. In aqueous solutions, mercury occurs mainly in the form of the Hg2+ ion. Metallic mercury dissolves slightly in water, reaching
a concentration of 0.28 millimole per litre of clean water and slightly less in oceanic water. Therefore, the conducted research covered Hg(II). The objective of the research was to assess the content of mercury in wet precipitation (snow) using isotachophoresis. Electromigration techniques, particularly isotachophoresis and capillary electrophoresis, are alternative to ion chromatography or conventional measurement methods [Kluska 2008a, b; Prukała et al. 2008a, b].
The content of mercury was determined in snow samples collected in the urban area of Siedlce. Melted snow samples of 2 dm3 each were collected in December 2017, and in January and February 2018. The samples were collected from the outskirts of the town of Siedlce, where the houses are heated by their own individual heating systems, using mostly carbon. The exact location of the sampling sites is presented in Figure 1.
Figure 1
A schematic map of points of samples collecting
The analyses of mercury content in the collected snow samples were performed using the isotachophoresis technique. First, a standard mercury solution was prepared in the form of a complex salt of potassium iodomercurate (POCH Gliwice) in deionised water (Merck) with a concentration of 0.1 mg Hg/cm3. Next, a 100-fold diluted working solution was prepared from the standard solution K2[HgI4]. Then, 1 cm3 of standard solution K2[HgI4] was pipetted into a 100 cm3 volumetric flask and topped up to the calibration mark with deionised water and thoroughly stirred. Subsequently, 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 cm3 of working solution K2[HgI4] containing [HgI4]2-ions were measured and added to six 2 cm3 volumetric flasks. The remaining volume of six flasks was topped up with deionised water up to 2 cm3. The standard solutions prepared in this way were successively introduced into the isotachophoresis apparatus and an analytical curve was calculated.
The next stage of the analysis was to transfer the mercury contained in water into the complex K2[HgI4]. To this end, a potassium iodide solution was slowly added to 2 dm3 of water (pH = 6.8) and was thoroughly stirred so that all the mercury contained in the solution was complexed. Initially, the precipitate of mercury (II) iodide was formed, which dissolved in the excess of KI and formed a colourless salt solution as per the following equation: HgI2 + 2 KI = K2[HgI4].
In the case of alkaline reaction of the solution, yellow turbidity or yellow precipitate may occur, which is indicative of the presence of ammonium ions. The resulting precipitate must be separated by decantation and the solution obtained after the concentration must be analysed by isotachophoresis. If the surface water, groundwater or other solutions containing heavy metals are analysed, certain difficulties may arise as some of them may precipitate in reaction with iodides or form amalgams with mercury. In the acid environment, on the other hand, iodide ions reduce nitrite (III) ions to nitrogen oxides, and oxidise themselves to free iodine, which stains the solution reddish brown. In the case of the presented study, the above mentioned problems did not occur.
Reagents of increased purity (so-called pure for analysis reagents or analytical reagent grade) were used. Leading electrolyte LE-1 for a preseparational column, prepared from equal volumes of the following solutions: NaCl solution (POCh Gliwice, 8 ∙ 10-3 mole/dm3), 1,3 – bis[tris(hydroxyethyl)methylamino]propane solution (Aldrich, 3 ∙ 10-3 mole/dm3), β-alanine solution (Aldrich, 1.5 ∙10-3 mole/dm3) and hydroxyethylcellulose solution (Aldrich, 0.1%). Leading electrolyte LE-2 for an analytic column, prepared from equal volumes of the following solutions: NaCl solution (2 ∙ 10-3 mole/dm3),
Figure 2
Structure of a compound used in terminating electrolyte: 4,4’-bis{1-(N-perhydroazepiniomethyl)[spirobi(1-sila-2,5-dioxacyclopentane-3-on)]ate}
Analyses were carried out by means of a capillary electrophoresis analysator EA 202M produced by Villa Labeco s.r.o. in Spisska Nova Ves equipped in: preseparation column (diameter 0.8 mm, length 90 mm), analytic column (diameter 0.3 mm, length 160 mm) and conductometric detector for every columns with a measurement range between 30 kΩ and 20 MΩ.
The samples (volume 0.03 cm3) were inserted by a feeding valve to the separation system. Data reported by the detectors were collected and transformed in a personal computer equipped in specialized program ITPPro 32 (Kascomp, Bratislava, Slovakia).
The isotachophoretic method of mercury determination in water solution was subjected to validation according to generally accepted principles. Presented method was examined by determination such parameters as: recovery, precision, limit of identification and linearity [Konieczka et al. 2004].
The snow samples were collected in four places on the outskirts of Siedlce, where the largest complexes of detached houses are located (Figure. 1). Almost every house is supplied with gaseous fuel for heating. Despite this, however, many of them are mainly heated by bituminous coal, wood and sometimes various types of waste. The combustion of coal and waste emits a lot of pollutants into the atmosphere; hence, rainwater and snow may contain miscellaneous chemicals and heavy metals (including mercury), which have a very negative impact on the environment. Pollutants emitted by chimneys can spread over different distances and fall to the ground with precipitation, leading to soil degradation. Runoff and precipitation waters as well as snow have been analysed many times, but the content of mercury was usually negligible [Kowalski et al. 2007].
The most commonly used methods for the determination of mercury in aqueous solutions include: flameless atomic absorption spectrophotometry combined with the cold vapour method (CV-AAS), the extraction-colorimetric method and the indirect dithizone method using copper carbamate. Depending on the applied method, however, mercury can also be determined by isotachophoresis. Due to formal reasons, the present study was limited to the determination of mercury by isotachophoresis only. Research on water from precipitation, including snow, is very important for many reasons. Firstly, the rainwater becomes the surface water, which is then used for industrial, household and other purposes. Therefore, this type of research has been carried out and presented in this paper. The obtained results are presented in Tables 1 and 2.
Characteristic of elaborated analytical method
| Parameter | Unit | In conversion to Hg |
|---|---|---|
| Precision1 | % | 4.7 |
| Recovery2 | % | 93 ± 4 |
| Linearity3 | μg/dm3 | 0.15–10.0 |
| Limit of detection4 | μg/dm3 | 0.03 |
| Limit of quantification5 | μg/dm3 | 0.10 |
1 – n = 5, the samples were analysed twice
2 – the sample was enriched with 1.5 cm3 of a solution containing 1 mg/cm3 [HgI4]2-, n = 5
3 – correlation coefficient above 0.9987
4 – calculated from the limit of identification and coefficients of the calibration curve
5– LOQ = 3 x LOD
Average mercury content [μg/dm3] in the tested snow samples (n = 5)
| Sampling point marked on the map | December Min–Max (average) | SD, % | January Min–Max (average) | SD, % | February Min–Max (average) | SD, % |
|---|---|---|---|---|---|---|
| 1 (housing development Topolowa) | 0.27–0.35 (0.32) | 3.8 | 0.22–0.29 (0.25) | 2.9 | 0.26–0.36 (0.32) | 4.5 |
| 2 (housing development Nowe Siedlce) | 0.23–0.28 (0.26) | 1.9 | 0.20–0.28 (0.25) | 3.2 | 0.22–0.35 (0.34) | 4.7 |
| 3 (housing development Żwirowa) | 0.30–0.39 (0.35) | 3.3 | 0.33–0.38 (0.36) | 1.9 | 0.29–0.38 (0.34) | 3.4 |
| 4 (housing development Nad Zalewem) | 0.25–0.33 (0.28) | 3.4 | 0.21–0.32 (0.27) | 4.3 | 0.23–0.33 (0.28) | 4.0 |
SD – standard deviation
Using the prepared standard solutions, the analytical method applied in the research has been described. The obtained characteristics along with data used for qualitative and quantitative analysis are presented in Table
1. When analysing the obtained data, it is easy to observe that the applied method provides high precision of up to 5%, a wide range of linearity (0.15–10.0 μg/dm3) and can be used for routine determinations. The detection limit of the applied method is 0.03 μg/dm3 and the quantification (determination) limit is 0.10 μg/dm3.
The obtained average results of the analysed snow samples are presented in Table 2. Various unsustainable human activities lead to environmental degradation. Such activities lead to, among others, the presence of mercury in meteoric water (derived from precipitation) (Table 2). The protection of waters against contamination is not a one-off activity and is very important in the economic life of each country [Michalski 2005a,b; Zahir et al. 2005, Biniak et al. 2010; Kluska et al. 2014]. Both ground and surface water are protected. They need to be managed rationally, to prevent pollution, disturbance of the natural balance and changes, which make them unsuitable for people, plants and animals. The protection of water usually consists of reduction, avoidance and elimination of contamination. Contaminants permanently harmful to the environment [Act 20 July 2018], which undoubtedly also include mercury, are particularly important.
In accordance with the Regulation of the Minister of the Environment of 07 December 2017 on the requirements to be met by surface water used as drinking water, the permitted mercury content is 10 μg/dm3. The results obtained for snow samples are significantly below this value (Table 2). The highest average content of mercury was found in samples collected in the Żwirowa housing development, regardless of the sampling date. Samples collected in December showed an average content of 0.35 μg/dm3, in January – 0.36 μg/dm3, and in February – 0.34 μg/dm3. On the other hand, the lowest values of 0.25 μg/dm3 were determined in samples collected in January in the Topolowa and Nowe Siedlce housing developments. Very similar values (0.27–0.28 μg/dm3), regardless of the sampling month, were obtained in the Nad Zalewem housing development. All results obtained by isotachophoresis showed low values of the standard deviation below 5%.
The prevention of water degradation should be comprehensive and cover all domains of human activity. The process of preventing degradation is very expensive; therefore, it is best to prevent it through prohibitions according to water resources law. An example is the law prohibiting the introduction of waste [Act 20 July 2017] and sewage into water [Regulation of the Ministry of the Environment of 24 July 2006], discharge of snow removed from polluted areas, collection of sewage, chemicals and other materials that may lead to water contamination [Act 20 July 2018].
Water is the most important compound affecting a quality of a human life. Therefore, prevention as well as protection by the law is necessary. The most important acts concerning aspects of the protection of water in Poland are: Act of Parliament from 13th of April 2018 concerning protection and shaping of an environment [Act of Parliament 13.04.2018], Act of Parliament from 20th of July 2018 concerning changing of the act – Water Law [Act of Parliament 20.07.2018], Act of Parliament from 20th of July 2018 concerning Inspection of Environment Protection [Act of Parliament 20.07.2018].
Rain and snow play a particularly important role in the circulation of mercury. Mercury gets into the water from precipitation, surface and groundwater runoff. This chemical element occurs in waters in large dispersion. The air quality is affected by, among others, individual heating systems, transport and CHP plants. The lowest average mercury content of 0.25 μg/dm3 was determined in January in snow samples collected in the residential districts of Nowe Siedlce and Topolowa (Table 2). On the other hand, the highest average content of mercury of 0.36 μg/dm3 was determined in January in the Żwirowa housing development (Table 2). For the first class of surface water quality, the permitted mercury content is 10 μg/dm3. When comparing the obtained data from particular housing developments, it appears that they do not exceed the permissible values. The highest contamination with mercury occurs in the Żwirowa housing development, regardless of the sampling date. The lowest contamination with mercury was determined for samples collected in the Nowe Siedlce and Nad Zalewem housing developments. Other authors obtained slightly lower results [Ferrari et al. 2002, Kirk et al. 2006, Siudek 2016c, Steffen et al. 2014, Wang et al. 2004].
It was showed that concentrations of atmospherically deposited Hg were highly variable in snow cover. The research was conducted in Poznań (Poland), Canada and China.
The presence of mercury in snow samples found during the presented study indicates a significant contribution of pollutants emitted to the atmosphere. Coal heating systems still dominate in the districts of single-family detached housing in the town of Siedlce. The conducted research indicates a negative impact of human activity. In all the snow samples collected for the analysis, mercury was found to be present in the range from 0.20 μg/dm3 in January in the Nowe Siedlce housing development to 0.39 μg/dm3 in December in the Żwirowa housing development.