INTRODUCTION<\/h2>\n
Polycyclic aromatic hydrocarbons (PAHs) form an important group of substances, most of which show adverse effects on aquatic organisms and humans. Due to their persistence, they have the ability to remain in the aquatic environment for a long time. Directive 2008\/105\/EC of the European Parliament and of the Council [1], as amended by Directive 2013\/39\/EU [2], included selected PAH substances in\u00a0the\u00a0list of priority substances, of which anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene are identified as priority hazardous substances. According to Framework Directive Polycyclic aromatic hydrocarbons are ubiquitous substances found in all components of the environment. They are one of the most common reasons for failure to achieve good chemical and ecological status of surface waters (note: PAHs specified as priority substances are currently subject to chemical status assessment, other PAHs belong to the group of specific pollutants, which are one of the components of the ecological status assessment of surface water bodies). The environmental quality standard expressed as an annual average is the strictest for benzo[a]pyrene (0.17 ng.l-1<\/span>), followed by fluoranthene (6.3 ng.l-1<\/span>) [4].<\/span><\/p>\n This was also the reason for the inclusion of the group of PAH substances in\u00a0the\u00a0TA\u00a0CR project SS01010231 \u201cImpacts of atmospheric deposition on the aquatic environment with consideration of climatic conditions\u201d<\/span>, which was realized from March 2020 to December 2022. The aim of this project was to verify the level of pollution in selected components of the environment, or to investigate the link between them with the impact on surface water quality in order to be able to better quantify this impact in the future, and to propose effective measures for achieving a good chemical status of surface waters in terms of PAH pollution. Two different forest microcatchment sites were chosen: one with significant anthropogenic influence (the upper part of the Such\u00fd stream basin in the cadastre of Byst\u0159ice municipality in the Moravian-Silesian Beskids) and the other in the reference area (the Lesn\u00ed stream in the cadastre of Ko\u0161etice municipality near Ko\u0161etice climatological station).<\/span><\/p>\n Polycyclic aromatic hydrocarbons (PAHs) can be found in all components of the environment. This is due to the fact that the dominant source of pollution is combustion processes, which are of both natural and anthropogenic origin. The most important natural sources of PAHs are volcanic activity, vegetation cover fires, and some\u00a0<\/span>sedimentary rocks. Anthropogenic emissions of PAHs of a non-industrial nature arise from the targeted burning of vegetation, from domestic heating, and smoking. In industry, the dominant sources of pollution are the production of coke, electric and thermal energy, smelters, selected branches of chemical industry (tar processing, catalytic cracking, soot production), and also food industry [5].<\/span><\/p>\n The rate of PAH production depends on the combustion process and the type of\u00a0fuel used. It is highest during incomplete combustion, which happens mostly in local domestic heating. The mechanism of PAH formation involves two processes: pyrolysis and pyrosynthesis. Pyrolysis produces PAH precursors, which recombine at temperatures of 500 to 800 \u00b0C to form relatively stable aromatic hydrocarbons [5]. In\u00a0the case of incomplete combustion, the emissions of primary PAHs contained in the fuel can also occur. The primary emissions of PAHs into the air are predominantly in the gaseous phase, but their condensation and sorption to fine dust particles occurs relatively quickly during the cooling of flue gases. The rate of sorption depends on the molecular weight. According to selected characteristics of physico-chemical properties (Henry\u2019s constant, partition coefficients Kow<\/span>, Koc<\/span>) we can divide PAHs into:<\/span><\/p>\n This division is important because the above-mentioned groups of PAHs behave differently in the environment. We can show the differences, for example, using Henry\u2019s constant, which states the partial pressure of the gas above the solution, expressed in the unit Pa.m3<\/sup>.mol-1<\/sup>. For naphthalene it is 43.00, acenaphthene 12.17, pyrene 0.919, and benzo[k]fluoranthene 0.044 Pa.m3<\/sup>.mol-1<\/sup> [7]. The difference is within several orders of magnitude; the higher the molecular weight, the easier and faster the binding to fine particles.<\/span><\/p>\n When burning coal, mainly phenanthrene (over 50 %), anthracene, and fluoranthene to a lesser extent, and a small amount of benzo[a]pyrene (0.5 to 2.4 %) are produced [6]. Combustion products are also PAH derivatives, mainly nitroaromatics.<\/span><\/p>\n In the atmosphere, mainly low molecular weight PAHs are broken down by sunlight. High molecular weight PAHs are sorbed to particles of different sizes. The smaller the\u00a0particles, the longer the degradation time is needed to break down the PAH (up to several weeks), and the longer the PAHs remain in the atmosphere. From the atmosphere, PAHs are introduced into other components of the environment by dry and wet deposition. Due to their longer lifetime, high-molecular-weight PAHs are transported from the source over long distances, depending on climatic conditions and the time of\u00a0year. In winter, the concentration of PAH in the air is significantly higher than in summer. This is due to higher emissions from combustion processes combined with lower efficiency of photodegradation processes in the cold part of the year.<\/span><\/p>\n From the atmosphere, PAHs reach vegetation and the earth\u2019s surface through dry and wet deposition. On agricultural soils, PAHs penetrate into deeper soil layers due to ploughing, while in other cases they remain in surface layers. Low molecular weight PAHs partially volatilize back into the atmosphere or are decomposed by photochemical processes. Biodegradation by microorganisms is also present, which is the predominant factor in the decomposition of primary PAHs. The rate of degradation depends on the soil type and organic carbon content. S. Thiele-Bruhn studied the kinetics of PAH degradation in soils contaminated by industrial activity (gas industry, coke plants) [8]. Fine soil with a particle size below 2 mm from 11 sites with a predominance of loamy-sandy soils was placed in Mitscherlich containers and fertilized with equal amounts of\u00a0phosphorus and potassium in order to stimulate microbial processes. The experiment took place for 168 weeks in natural conditions. The result was the determination of\u00a0the degradation rate constant \u201ck\u201d and the decrease of individual PAHs expressed as\u00a0DT50<\/span> (disappearance time). In the case of naphthalene and acenaphthene, the median DT50<\/span> was units of weeks (6.1 and 9.5, respectively), for anthracene and phenanthrene tens of weeks (70\u00a0and 92, respectively), for other high molecular weight PAHs it was over 100\u00a0weeks with a maximum of 522 weeks for benzo[k]fluoranthene. Thus, high molecular weight PAHs remain in the soil for a long time.<\/span><\/p>\n Particularly low molecular weight PAHs with 2 to 3 aromatic nuclei, which make up to 80 % of total PAHs, pass into the vegetation from the soil and the atmosphere through the root system and leaves. The relatively high concentration of naphthalene in\u00a0crops is due to its higher solubility in water [9]. High molecular weight PAHs are sorbed on the surface of vegetation. PAHs reach surface waters through erosional washes from soils, vegetation, and from the paved surfaces of roads and urban agglomerations. This\u00a0type of transfer in terrestrial systems dominates over bulk deposition. High molecular weight PAHs preferentially bind to fine particles of undissolved substances in water, and sediment in suitable places depending on the nature of\u00a0the\u00a0flow. In well-oxygenated streams, the process of PAH degradation is faster, both in the water column and in river sediment. The rate of microbial revival of the aquatic environment also plays a\u00a0positive role in the process of their degradation. The present dissolved organic matter (DOM) accelerates the photodegradation of low molecular weight PAHs by facilitating the formation of reactive intermediates and, conversely, inhibits the photodegradation of high molecular weight PAHs (e.g., benzo[a]pyrene) by binding their molecules [10]. <\/span><\/p>\n In surface waters, PAHs are a long-term cause of failure to achieve good chemical status. In the last evaluated three-year period from 2016 to 2018, a total of 54.7 % of surface water bodies failed or were not classified in the fluoranthene indicator and 99.3\u00a0% in the benzo[a]pyrene indicator [11]. The latter indicator is also problematic from the point of view of the difficulty of achieving a sufficiently low limit of determination by laboratory techniques in relation to the value of the environmental quality standard (EQS) expressed as an annual average.<\/span><\/p>\n The ubiquity of PAHs in the environment, the failure to achieve good water quality, and the danger to human health are the reasons why it is necessary to pay attention to these substances. The International Agency for Research on Cancer (IARC) has classified 60 polycyclic aromatic hydrocarbons into groups according to their potential carcinogenic effects to humans. Of the 15 PAHs monitored as part of\u00a0the\u00a0ATMDEP project, benzo[a]pyrene belongs to group 1 \u2013 \u201cproven carcinogen\u201d. Group 2A \u2013 \u201cprobably carcinogenic to humans\u201d includes dibenzo[a,h]anthracene. Group 2B \u2013 \u201csuspected human carcinogen\u201d includes benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, indeno[1,2,3-c,d]pyrene. Group 3 \u2013 \u201cunclassifiable\u201d includes acenaphthene, anthracene, benzo[g,h,i]perylene, fluoranthene, fluorene, phenanthrene and pyrene. Benzo[a]pyrene is currently the only PAH representative in Group 1. In the human body, it metabolizes to PaP-7,8-diol 9,10-epoxide, which can damage DNA. For Group 3, there is still insufficient evidence of their carcinogenic effects [12]. It has to be noted that PAHs act in the mixture. Therefore, a number of\u00a0authors have developed toxic equivalent factors (TEFs) for individual PAHs, which are related to the toxicity of benzo[a]pyrene (BAP = 1). Nisbet and LaGoy did so in 1992\u00a0[13]. They applied a higher TEF than for BAP in the case of DBA (TEF = 5). In\u00a0the\u00a0case of\u00a0the other four PAHs (BAA, BBF, BKF, INP), TEF = 0.1. For ANT, BGP, and CHRY they applied TEF = 0.01. For other PAHs, the TEF is equal to 0.001. (The abbreviations used to denote PAHs are listed in Tab. 2<\/span><\/em>.) Multiplying the concentration of each determined PAH by this factor and adding them up gives the equivalent concentration with respect to the toxic potential of benzo[a]pyrene.<\/span><\/p>\n In the project, PAHs were investigated and evaluated which cause a failure to achieve good water status and, at the same time, which are expected to be transmitted through the air even at great distances from the sources of pollution.<\/p>\n In order to compare the presence of polycyclic aromatic hydrocarbons in individual components of the environment, samples of the following matrices were selected at\u00a0the two sites:<\/p>\n * For the analytical determination of polycyclic aromatic hydrocarbons in atmospheric deposition, it was necessary to obtain a sufficient volume of samples. At\u00a0the\u00a0Ko\u0161etice site, there were three cases of insufficient amount of sample for analytical determination due to the low monthly rainfall total; therefore, in these cases, the rainfall samples were taken after a two-month exposure.<\/p>\n In aqueous samples, PAHs were analysed on an Agilent 1260 Infinity II liquid chromatograph with fluorescence detection. A Pinnacle II PAH 4 \u00b5m column, 150 x 4.6\u00a0mm (Restek), and a mobile phase with the composition A: methanol, B: water + 5 % methanol were used for separation. Sediments were lyophilized and sieved through a\u00a02\u00a0mm sieve prior to extraction.<\/span><\/p>\n Polycyclic aromatic hydrocarbons in moss and humus samples were analysed on a Bruker EVOQ GC-TQ gas chromatograph by MS\/MS. Red-stemmed feathermoss samples were collected in the autumn of 2020 and 2021 at three sites in the upper parts of the Such\u00fd stream basin and in the vicinity of the Lesn\u00ed stream in bulk (unaffected by throughfall deposition) in aluminium bags. After being transported to the laboratory in a cooling box, the moss samples were stored in a freezer and, after thawing, manually cleaned of unwanted\u00a0 impurities. For PAH determination, the upper green parts of the moss were torn off. The moss was then homogenized in a vibrating mill using liquid nitrogen and dried by lyophilization. PAHs were extracted with n-hexane. After evaporation, the extract was purified by gel permeation chromatography. Bio-Beads SX-3 styrenedivinylbenzene polymer gel was used. Humus samples were simultaneously collected in aluminium bags from the visually undisturbed Oh\u00a0horizon at three sites in each micro-catchment and transported and stored like the moss samples. After drying by lyophilization, they were sieved to a size of\u00a00.25\u00a0mm. PAHs were extracted with dichloromethane with the addition of Al2<\/span><\/sub>O3<\/span><\/sub> and diatomaceous earth. PAH extractions from both moss and humus samples were performed at\u00a0elevated temperature and pressure with a Dionex ASE 350 extractor.<\/span><\/p>\n For <\/span>the<\/span> project, model forest micro-catchments were selected that met the\u00a0following criteria:<\/span><\/p>\n The following micro-catchments were selected as pilot areas on the basis of\u00a0the\u00a0above-mentioned criteria:<\/span><\/p>\n In October 2020, monitoring of atmospheric precipitation in monthly campaigns was started at both sites (Tab. 1<\/span><\/em>). In the case of insufficient rainfall, a\u00a0two-month rainfall sample was used (sample volume required was 2,000 ml). Rain gauges were installed at the sites to capture bulk precipitation, and in the forest stand to capture throughfall precipitation. For the collection of precipitation for PAH determination, a rain gauge was made for a stainless steel container with a collection area of 52.4 cm2<\/span><\/sup> (Fig. 4<\/span><\/em>). The upper part of the rain gauges was equipped with a stainless steel bowl with holes so that the fall of\u00a0coarse solid particles and insects did not get into the collected precipitation sample. A conifer (spruce in both cases) was chosen for the throughfall exposure, because precipitation was also collected in winter. The amount of precipitation recorded in individual campaigns was measured and compared with data on the total precipitation for the same period from the nearest climatological station of\u00a0the\u00a0Czech Hydrometeorological Institute (CHMI). At the same time, spot sampling of surface water from a nearby watercourse was carried out during the precipitation sampling. The average monthly flow for the Such\u00fd stream was derived according to the flows at the nearest CHMI gauging station from the\u00a0ratio of the areas of the given sub-basins. The average monthly flow of\u00a0the\u00a0Lesn\u00ed stream was taken from regular measurements carried out by CHMI.<\/span><\/p>\n On the basis of field data, i.e., the amount of precipitation and the detected concentrations of monitored parameters of 15 PAHs in precipitation, an estimate of the total deposition for a given experimental basin was calculated according to the following formula:<\/span><\/p>\n \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 Where:\u00a0\u00a0\u00a0\u00a0 RS\u00a0\u00a0 is \u00a0\u00a0 the annual precipitation in a given basin<\/p>\n Sx\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0amount of precipitation in a given month converted to the basin area<\/p>\n Cx\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 concentration of the pollutant in the throughfall sample of a given month<\/p>\n The results of PAH concentrations in throughfall deposition were used in\u00a0the\u00a0calculation, which is considered the best possible estimate of total atmospheric deposition and is used in particular for determining the input of substances when balancing the circulation of substances in small basins [15].<\/p>\n The estimate of the annual substance ratio of watercourses for a given pollutant was calculated on the basis of the derived flow rate and the detected concentrations according to the following formula:<\/p>\n Where:\u00a0\u00a0\u00a0\u00a0 LOD\u00a0 \u00a0is\u00a0\u00a0\u00a0 riverine load<\/p>\n Qx\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 average flow rate in the campaign<\/p>\n Cx\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 concentration of the substance in the spot sample<\/p>\n D\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 period<\/p>\n Values of concentration below the detection limit were not included.<\/p>\n Note: The usual procedure of using half the limit of determination was not chosen because the results of the two procedures show large differences.<\/p>\n In the following tables and graphs, the abbreviations listed in Tab. 2<\/span><\/em> are used for individual PAH compounds.<\/span><\/p>\n For information, the PAH results in precipitation and in surface water are compared with the limits of good surface water status according to Government Regulation No. 401\/2015 Coll. [4]. These limits are environmental quality standards (EQS) expressed as an annual average value of AA-EQS and as the highest permissible concentration of MAC-EQS. Tab. 3<\/span><\/em> shows the result of the evaluation of surface water bodies where good chemical or ecological status was not achieved in\u00a0terms of individual PAH indicators. The evaluation was carried out in 2016\u20132018 for\u00a0the\u00a0third river basin management plans. From the total of 1,118 surface water bodies, PAHs were measured in 53 to 65 % of them. The number of insufficient water bodies indicates the importance of these substances in terms of determining measures to achieve good surface water status.<\/span><\/p>\n Tab. 4<\/span><\/span><\/em> and 5<\/span><\/em> show the results of PAH measurements in surface water and precipitation (bulk and throughfall) at Byst\u0159ice and Ko\u0161etice. Values that are higher than the values of environmental quality standards for good surface water status are marked in red. The measurement results in individual sampling campaigns are compared with the MAC-EQS value, the calculated average annual value is compared with the AA-EQS value. The results are shown in Fig. 5\u201310<\/span><\/em>. They show a high load of PAHs in precipitation at the Byst\u0159ice site.<\/span><\/p>\n In Fig. 7, 8, 10<\/span><\/em>, and 11<\/span><\/em>, the trend in PAH pollution in winter and summer precipitation can be observed. The increase in concentrations in the winter period is most probably influenced by the local heating stations and meteorological conditions (temperature inversion?<\/span>) during the colder part of the year. Of\u00a0the\u00a0individual PAH compounds, concentrations prevail in atmospheric precipitation in the\u00a0Such\u00fd stream \u2013 Byst\u0159ice in the following order: fluoranthene, pyrene, bezo[a]anthracene, phenanthrene, chrysene, and benzo[b]fluoranthene, and in\u00a0the\u00a0Lesn\u00ed stream\u00a0\u2013 Ko\u0161etice in the following order: fluoranthene, phenanthrene, pyrene, benzo[a]anthracene, chrysene and benzo[b]fluoranthene.<\/span><\/p>\n
\n2000\/60\/EC establishing the framework for Community action in the field of water policy [3], Article 16 (Strategy against pollution of water) there is a need to reduce discharges, emissions, and leaks of these substances in a targeted manner; in the case of priority dangerous substances it is even a matter of stopping or gradual elimination of input into the environment. The requirements of the above Directives were implemented in Czech Government Radulation No. 401\/2015 Coll. [4].<\/span><\/p>\nPOLYCYCLIC AROMATIC HYDROCARBONS IN\u00a0THE\u00a0ENVIRONMENT<\/h2>\n
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METHODOLOGY<\/h2>\n
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Fig. 1. Location of the selected pilot sites<\/h6>\n
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<\/a>\nFig. 2. Such\u00fd stream site, Byst\u0159ice (Source: HEIS TGM WRI)<\/h6>\n
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Fig. 3. Lesn\u00ed stream site, Ko\u0161etice (Source: HEIS TGM WRI)<\/h6>\n
Tab. 1. Monthly precipitation amount and flows in sampling campaigns at the Byst\u0159ice and Ko\u0161etice sites<\/span><\/h5>\n
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Fig. 4. Rain gauge for precipitation capture for PAH analysis<\/h6>\n
<\/a>\nFig. 5. Rain gauges for capturing bulk and throughfall precipitations at the Byst\u0159ice site (5th November 2020)<\/h6>\n
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Fig. 6. Rain gauge for capturing bulk precipitation at the Ko\u0161etice site (8th February 2021)<\/h6>\n
<\/a><\/p>\n<\/a>\nRESULTS<\/h2>\n
Tab. 2. Abbreviations used to designate individual PAH compounds<\/span><\/h5>\n
<\/a>\nTab. 3. Assessment of surface water body status 2016\u20132018 in PAH parameters for the third planning cycle<\/span><\/h5>\n
<\/a>\nTab. 4. Results of measurements of individual PAHs in surface water and precipitation, Byst\u0159ice site<\/span><\/h5>\n
<\/a>\nTab. 5. Results of measurements of individual PAHs in surface water and precipitation, Ko\u0161etice site<\/span><\/h5>\n
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Fig. 7. Such\u00fd stream, Byst\u0159ice \u2013 PAHs concentration in precipitation: BULK<\/h6>\n
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Fig. 8. Such\u00fd stream, Byst\u0159ice \u2013 PAHs concentration in precipitation: THROUGHFALL<\/h6>\n
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