New pollutants have emerged, such as pesticides and pharmaceuticals. The\u00a0input of\u00a0pharmaceuticals occurs year-round, and the\u00a0prospects for their complete removal in\u00a0wastewater treatment plants remain\u00a0limited.<\/p>\n
With progressing climatic change, the following changes are to be expected: longer periods of higher water temperatures and of low flow values, and a change in precipitation regime leading to higher frequencies of sewerage system overflows. Legislation is not prepared to control it, and we should rely on implementation of the new EU Directive 2024\/3019 (EU). With ongoing climate change, we expect longer periods of elevated water temperatures and low flow values, as well as a higher frequency of sewer overflows due to changes in precipitation patterns. This will significantly increase the impacts on river ecosystems and also reduce the effectiveness of current monitoring systems. Legislation is not prepared to control it, and we should rely on implementation of the new EU Directive 2024\/3019 (EU).<\/p>\n
INTRODUCTION<\/h2>\n
We now have data on water quality in\u00a0Czech rivers spanning more than 50\u00a0years, and we can state that water quality in\u00a0Bohemian and Moravian rivers has improved significantly over the\u00a0past 30 years. Although the\u00a0process had begun earlier, it was driven primarily by the\u00a0\u201cend of\u00a0socialism\u201d, which in\u00a0practice meant the\u00a0extinction closure of\u00a0many polluting companies, as well as the\u00a0adoption of\u00a0an international approach to large river basins (the\u00a0International Commissions for the\u00a0Protection of\u00a0the\u00a0Elbe, Danube, and Oder \u2013 ICPER, ICPDR, ICPO), European support to the\u00a0construction and upgrading of\u00a0wastewater treatment plants, and so on. Another key factor is implementation of\u00a0the\u00a0EU\u00a0Water Framework Directive (2000\/60\/EC), which brought a\u00a0fundamental shift in\u00a0the\u00a0assessment of\u00a0water status: it regards water bodies primarily as a\u00a0heritage to be protected and evaluates rivers and stagnant waters (classified as water bodies) in\u00a0a\u00a0comprehensive manner \u2013 that is, not only in\u00a0terms of\u00a0water quality but also in\u00a0terms of\u00a0habitat quality, e.g.\u00a0as the\u00a0extent to which hydromorphological characteristics deviate from their natural state. Today we can see that around the\u00a0year 2005, water quality in\u00a0rivers improved significantly at the\u00a0vast majority of\u00a0regularly monitored sites and according to standard indicators, and it has remained relatively stable ever since. However, this also means that it is no longer improving significantly. We can therefore ask whether water quality has truly stabilised or whether improvement has merely stagnated, and we may conclude that the\u00a0traditional approach to assessing water quality \u2013 based on the\u00a0notion of\u00a0\u201ccontinuous improvement\u201d \u2013 needs to be reconsidered, with greater attention paid to sources of\u00a0pollution and the\u00a0mechanisms behind anthropogenic changes in\u00a0water quality. Following the\u00a0already mentioned resolution of\u00a0the\u00a0WWTP issue, two \u201cnew aspects\u201d have emerged in\u00a0particular: (1) new pollutants \u2013 some genuinely new, others merely \u201cdiscovered\u201d thanks to advances in\u00a0analytical techniques; and (2) significant changes in\u00a0the\u00a0rainfall-runoff regime, related to climate change. In\u00a0the\u00a0following section, we will focus on the\u00a0Czech section of\u00a0the\u00a0Elbe catchment downstream from its confluence with the\u00a0Vltava, represented by the\u00a0monitoring sites at Ob\u0159\u00edstv\u00ed, Zel\u010d\u00edn, and H\u0159ensko.<\/p>\n
Water quality and how it is assessed<\/h3>\n
Water quality is the\u00a0sum of\u00a0the\u00a0physical, chemical, and biological properties of\u00a0a\u00a0specific water, always assessed against some standard. This standard is either its suitability for use (e.g. drinking, industrial, etc.) or its deviation from natural conditions. The\u00a0natural state is primarily shaped by the\u00a0region\u2019s\u00a0geology and precipitation patterns, while deviations are generally anthropogenic,\u00a0i.e.,\u00a0pollution. Assessing water quality involves a\u00a0series of\u00a0interconnected activities\u00a0\u2013 including sampling and field measurements, laboratory analyses, and subsequent evaluation of\u00a0results \u2013 collectively known as monitoring. The\u00a0outcome of\u00a0this process is a\u00a0set of\u00a0data tables corresponding to each monitored site, stored in\u00a0primary databases. It is only at this point that the\u00a0actual assessment begins, which can be conducted using various approaches.<\/p>\n
The\u00a0next step is to present the\u00a0results, which may be:<\/p>\n
- \n
- general \u2013 the\u00a0processing of\u00a0measured values,<\/li>\n
- \u201climit-based\u201d \u2013 assessed against commonly recognised threshold values,<\/li>\n
- classification into categories (such as quality classes, ecological status categories, etc.).<\/li>\n<\/ul>\n
In\u00a0the\u00a0first case, we obtain\u00a0data series and statistically processed values (e.g. averages) expressed in\u00a0absolute SI units (such as concentrations in\u00a0mg\/l, substance flux through a\u00a0profile in\u00a0g\/s\u00a0or t\/day). In\u00a0the\u00a0second case, the\u00a0outcome is merely a\u00a0statement that values are \u201cwithin\u00a0the\u00a0limit\u201d, a\u00a0limit we may not even know and which can be changed or \u201cupdated\u201d at any time. In\u00a0the\u00a0third case, we receive only a\u00a0\u201cclass\u201d that represents a\u00a0complex combined assessment of\u00a0multiple factors (and the\u00a0definition of\u00a0the\u00a0class may also be \u201cupdated\u201d over time). All three basic types have their advantages and disadvantages. The\u00a0first case is the\u00a0\u201conly correct\u201d approach because its published results are and will remain\u00a0usable and comparable over long time series and can be further processed. However, it is problematic for simple assessment, as a\u00a0lay user does not know \u201cwhat is correct.\u201d The\u00a0second case provides information in\u00a0the\u00a0context of\u00a0the\u00a0present, because as long as the\u00a0(currently accepted) limit is not exceeded, there is no qualified reason to take any measures. The\u00a0third case \u2013 categorisation into classes \u2013 has a\u00a0long history. Currently, two types are in\u00a0use in\u00a0our country. We have a\u00a0unique national standard, \u010cSN 75 7221 Water Quality\u00a0\u2013 Classification of\u00a0Surface Waters according to selected physical, chemical and biological quality indicators. Waters are then classified into five classes ranging from \u201cUnpolluted\u201d to \u201cHeavily Polluted.\u201d For the\u00a0basic indicators (BOD-5, COD-Cr, N-NH4<\/sub>, N-NO3<\/sub>, Ptotal<\/sub>, and the saprobic index of macrozoobenthos), the class is determined by the most adverse classification among the individual indicators, according to the threshold values in the class table. Additionally, a range of \u201cother\u201d indicators can be used as needed, in accordance with prescribed procedures. At the end of the classification process, the relevant sections of watercourses are marked on a map with the corresponding colour (ranging from light blue to the worst \u2013 red). Based on these, changes in the coloured sections on the map can be compared over two-year periods to assess \u201cimprovement\u201d. For a lay user or for summary information, this is almost perfect; for an objective professional, less so. The first issue lies in setting fixed class limits along a continuum of results, which is, however, a problem inherent to any categorisation. The second issue is more serious: the standard has been updated several times \u2013 namely in 1989, 1998, and 2017. This, of course, always changed the classification of the same river sections without anything actually happening on them \u2013 so, generally, it can lead to misunderstandings or even misinformation: for laypeople, suggesting \u201cthings are improving,\u201d and for some professionals, fostering an undue optimism that \u201cwe are improving because we are treating well.\u201d A different approach to classification is part of the assessment of water body quality for the purposes of the Water Framework Directive. For this, water quality is only one part of the ecological status assessment of water bodies, which are defined as parts of catchments, not just sections of watercourses. The levels of basic physico-chemical indicators and nutrients (nitrogen, phosphorus, etc.) are assessed as factors supporting the biological elements of the ecosystem (which includes macrozoobenthos, phytoplankton, and fish). At the start, there are basic tables of measured data; however, the evaluation focuses on deviation from an established reference condition for individual types of water bodies \u2013 which, among other things, means that water quality is never compared between a spring and the lower course of a river. The philosophy of the Water Framework Directive generally also accounts for shifts in reference conditions. The chemical status of water bodies is assessed separately, based on the presence of priority substances listed in progressively updated annexes. Across Europe, the chemical status remains unsatisfactory even today; by 2021, only 21 % of European water bodies had achieved a good chemical status [17]. This is partly result of advances in analytical methods, as priority substances and various hazardous or risky compounds are gradually being detected in more water bodies, so \u201csimple improvement\u201d cannot yet be expected here. However, water bodies are assessed in six-year cycles as part of the River Basin Management Plans. This differs from regular water quality monitoring, conducted at a basic frequency of 12 times per year by watercourse managers (River Basin Authorities), whose data we use here.<\/p>\n
We will further use only the\u00a0first type of\u00a0data processing \u2013 that is, results from regular monitoring conducted 12 times a\u00a0year, presented as annual averages or annual cycles \u2013 and we will \u201cassess\u201d only changes and their possible causes and correlations. We thank the\u00a0Vltava and Elbe River Basin\u00a0Authorities for the\u00a0data.<\/p>\n
DATA SOURCES AND METHODOLOGICAL APPROACH<\/h2>\n
Even Cosmas knew (and wrote at the very beginning of his chronicle [1]) that Bohemia is drained by a single river, called the Elbe. He mentions the Vltava a few lines later and describes how people stopped by it (in what was reportedly a deserted landscape) and named it after their chieftain. Although northern Bohemia is drained by the Nisa and Sm\u011bd\u00e1 into the Oder, we shall remain within the Elbe catchment. It can be divided into three parts: (1) the Vltava catchment, (2) the Elbe catchment upstream of its confluence with the Vltava, and (3) the \u201ccommon section\u201d from the confluence (M\u011bln\u00edk) to the border profile at H\u0159ensko. In this text, we work only with data taken from yearbooks, databases, and the cited literature. For comparison, we have excellent historical data from F. Ullik [2], who published daily measurements of basic water quality parameters in D\u011b\u010d\u00edn for 1877, and from F. Schulz [3], who processed annual measurements taken at monthly intervals upstream and downstream of Prague in 1913. Their analytical methods are reliable, and the data have only been recalculated to match today\u2019s standard for expressing results. In the 1960s, regular monthly monitoring of water quality in Czech (Czechoslovak) rivers gradually began, and the results have been stored by the Czech Hydrometeorological Institute (CHMI). They were first published in printed yearbooks and later, up until 2009, were publicly accessible on the CHMI website; this is described in more detail\u00a0in\u00a0[4]. In\u00a02010, the\u00a0International Commission for the\u00a0Protection of\u00a0the\u00a0Elbe also issued the\u00a0final \u201cValue Tables\u201d\u00a0[5], covering profiles from N\u011bm\u010dice and Zel\u010d\u00edn all the\u00a0way to the\u00a0sea; data from the\u00a0German profiles are still freely available online. More recent data are accessible only upon request and agreement with their providers \u2013 the\u00a0Povod\u00ed Labe\u00a0and Povod\u00ed Vltavy, state enterprises, to whom we would once again\u00a0like to express our thanks for making the\u00a0data available. For the\u00a0key indicators of\u00a0water quality, we now have monthly data (concentrations, discharges, etc.) covering 50 years or more, and we can retrospectively confirm that these are reliable data, verified by European analytical standards and quality management systems. For calculating transport, we used published daily discharge values for the\u00a0dates on which samples were taken; for each year, we therefore have 12 \u201csituations\u201d that serve as the\u00a0basis for calculating annual transport and the\u00a0contributions from individual sub-catchments. The\u00a0analytical methods used throughout the\u00a0entire period are comparable. In\u00a0addition to gradual modernisation \u2013 the\u00a0introduction of\u00a0instrumental laboratory methods \u2013 it is important to note a\u00a0methodological change around 1999 concerning the\u00a0determination of\u00a0ammonia and nitrate nitrogen, phosphorus (total and P-PO\u2084), and chlorophyll. This involved the\u00a0introduction of\u00a0more selective methods and also the\u00a0unification of\u00a0procedures across the\u00a0whole of\u00a0the\u00a0Czech Republic, which was particularly significant for phosphorus and chlorophyll. What is essential is that the\u00a0change did not affect the\u00a0time series of\u00a0nitrogen concentrations, and since then, the\u00a0concentration values for total and phosphate phosphorus as well as chlorophyll have been entirely reliable. Tab.\u00a01<\/em> presents three key monitored profiles representing the\u00a0aforementioned three river sections or catchments. The\u00a0Ob\u0159\u00edstv\u00ed and Zel\u010d\u00edn profiles were introduced in\u00a01993 to replace the\u00a0previously used Na \u0160t\u011bp\u00e1n\u011b and Vep\u0159ek profiles \u2013 this was only a\u00a0slight downstream shift, and the\u00a0time series were seamlessly continued.<\/p>\n
Tab.\u00a01. Monitored profiles and their basins<\/h5>\n
![\"\"](\"data:image\/svg+xml;base64,PHN2ZyB3aWR0aD0iMSIgaGVpZ2h0PSIxIiB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciPjwvc3ZnPg==\")
<\/a>\nChanges in water quality and the controlling factors in the Vltava upstream of the Slapy Reservoir have been thoroughly analysed by the teams of L. Proch\u00e1zkov\u00e1 and J. Kop\u00e1\u010dek [6\u20138]. We have already attempted to process data from the lower section down to the confluence (excluding reservoirs), which is significantly influenced by Prague, and to generalise the trends\u00a0in\u00a0water quality in\u00a0the\u00a0major Czech rivers\u00a0[4, 9, 10]. We now present, for the\u00a0first time, overviews of\u00a0the\u00a0entire temporal development up to 2020.<\/p>\n
For comparing transport and \u201csources\u201d, we used data on discharges from point sources \u2013 WWTPs \u2013 for the\u00a0key indicators of\u00a0water quality. There are several databases available; here, we used publicly accessible data from the\u00a0Public Administration Information System (Informa\u010dn\u00ed system ve\u0159ejn\u00e9 spr\u00e1vy, ISVS) for 2022, focusing on municipal WWTPs serving more than 1,000 inhabitants. In\u00a0summary, this represents approximately 75\u00a0% of\u00a0the\u00a0population calculated according to population registers (as shown in\u00a0Tab.\u00a01<\/em>), or over 90\u00a0% of\u00a0the\u00a0population connected to public sewerage systems and WWTPs.<\/p>\n
The\u00a0Vltava differs significantly from the\u00a0Elbe as a\u00a0river, and not only because upstream of\u00a0their confluence it has twice the\u00a0catchment area despite having the\u00a0same average discharge. The\u00a0Elbe rises in\u00a0higher mountains, flows through flat terrain, and, although it has numerous weirs, it has no major reservoirs. From the\u00a0confluence, it continues all the\u00a0way to the\u00a0sea, passing through a\u00a0short gorge between D\u011b\u010d\u00edn and Pirna. The\u00a0Vltava flows from Lipno Reservoir through a\u00a0deeply incised valley that opens out in\u00a0the\u00a0\u010cesk\u00e9 Bud\u011bjovice Basin\u00a0and broadens slightly near Prague. Number of\u00a0significant hydraulic structures are built on the\u00a0river \u2013 deep reservoirs with long average retention times and probably considerable sedimentation. During dry periods, the\u00a0lower Vltava is supplemented by releases from the\u00a0Orl\u00edk Reservoir, which influences the\u00a0flow regime as far downstream as H\u0159ensko, or rather at the\u00a0D\u011b\u010d\u00edn gauging profile.<\/span><\/p>\n
RESULTS<\/h2>\n
Development of\u00a0water quality at the\u00a0H\u0159ensko border\u00a0profile<\/h3>\n
The\u00a0development of\u00a0key water quality characteristics at the\u00a0H\u0159ensko profile largely reflects overall trends in\u00a0the\u00a0Czech Basin, both in\u00a0terms of\u00a0pollution from point sources (municipal and industrial) and changes in\u00a0agriculture and land management, meaning pollution from diffuse sources. The\u00a0contribution from point sources can be quantified based on data from pollution producers, although with a\u00a0certain\u00a0degree of\u00a0uncertainty; however, the\u00a0overall uncertainty for diffuse sources is much higher, especially for the\u00a0lower reaches of\u00a0large rivers. Furthermore, diffuse sources \u201crespond\u201d to current weather conditions (precipitation, drought, etc.), whereas when balancing point sources, we have so far been unable to fully address the\u00a0issue of\u00a0sewer system overflows.<\/span><\/p>\n
A\u00a0typical example of\u00a0the\u00a0historical development of\u00a0water quality is the\u00a0monthly variation of\u00a0BOD-5 and COD-Cr values at the\u00a0H\u0159ensko profile from 1961 to 2020, presented in\u00a0Fig.\u00a01<\/span><\/em> (COD measurements only began in\u00a01971). It is clear how organic carbon load in\u00a0the\u00a0watercourse gradually decreased (with a\u00a0turning point around 1995) and has since remained relatively stable. The\u00a0graph shows seasonal fluctuations, and upon closer analysis (Fig.\u00a02<\/span><\/em>), it becomes apparent that the\u00a0seasonal pattern of\u00a0BOD-5 in\u00a0recent years correlates significantly with chlorophyll-a\u00a0concentration, that is, it is controlled by the\u00a0current production of\u00a0phytoplankton. This correlation is even stronger in\u00a0the\u00a0Vltava at the\u00a0Zel\u010d\u00edn profile and lower at the\u00a0Ob\u0159\u00edstv\u00ed profile. Fig.<\/span>\u00a02<\/span><\/em> presents correlations for the\u00a0most recent decade, 2011\u20132020 (n = 120), covering markedly different years. In\u00a0all profiles, phosphorus concentration (Ptotal<\/span><\/sub>) remains in\u00a0surplus throughout the\u00a0year, so the\u00a0varying phytoplankton production (besides the\u00a0seasonal cycle) is probably determined by differences in\u00a0the\u00a0watercourse morphology.<\/span><\/p>\n
<\/a>\n<\/p>\n
Fig. 1. Trends in BOD- and COD values 1961\u20132020<\/h6>\n
<\/a>\n<\/p>\n
Fig. 2. Correlations of BOD-5 values and chlorophyll-a\u00a0concentrations 2011\u20132020<\/h6>\n
Significant changes are observed in\u00a0the\u00a0concentrations of\u00a0ammonia nitrogen (N-NH4<\/span><\/sub>) and nitrate nitrogen (N-NO3<\/span><\/sub>, measured only since 1967). Ammonia nitrogen practically disappeared between 1990 and 1995, and measurable concentrations in\u00a0the\u00a0monitored profiles today occur only sporadically, mainly in\u00a0winter. A\u00a0comparison with the\u00a0Podol\u00ed profile (Vltava above Prague) shows that in\u00a0the\u00a0Ob\u0159\u00edstv\u00ed, H\u0159ensko, and partly Zel\u010d\u00edn profiles, N-NH4<\/span><\/sub> originated from point sources, particularly\u00a0<\/span>municipal but also non-municipal sources on the\u00a0Elbe. The\u00a0theoretical oxygen demand for N-NH4<\/span><\/sub> nitrification was comparable to the\u00a0BOD-5 values at that time. Currently, nitrogen in\u00a0the\u00a0rivers is present almost exclusively as nitrate. WWTPs now mostly discharge nitrogen in\u00a0the\u00a0form of\u00a0nitrate, and wastewater discharge balances indicate that a\u00a0significant source of\u00a0nitrate today is the\u00a0\u201clandscape,\u201d meaning input from diffuse sources. This, however, is a\u00a0general problem because nitrate is stable and can only be removed from watercourses through denitrification, that is, bacterial reduction to atmospheric nitrogen (with a\u00a0certain\u00a0proportion of\u00a0the\u00a0greenhouse gas nitrous oxide). Given today\u2019s\u00a0minimal discharge of\u00a0organic carbon (Fig.\u00a01<\/span><\/em>), oxygen conditions in\u00a0large watercourses remain\u00a0stable, and nitrate flows into the\u00a0ocean, where it positively influences primary production and contributes to global climate change. Nitrate concentrations and their transport by rivers now show significant seasonal variations (generally peaking in\u00a0January\/February), corresponding to runoff from the\u00a0landscape linked to precipitation and flow regimes, as well as biological processes dependent on temperature cycles. This should not reduce the\u00a0obligation of\u00a0WWTPs to remove nitrogen from wastewater; however, the\u00a0era of\u00a0massive N-NH4<\/span> concentrations is behind us. Phosphorus (unlike nitrogen, which can be \u201creturned to the\u00a0atmosphere\u201d) does not disappear once it enters the\u00a0river and is transported to the\u00a0ocean. During the\u00a0growing season, the\u00a0persistent excess of\u00a0phosphorus supports primary production of\u00a0phytoplankton, especially in\u00a0reservoirs and the\u00a0lower reaches of\u00a0rivers.<\/span><\/p>\n
In recent years, chloride concentrations in the Elbe have remained fairly stable, whereas sulphate concentrations have steadily declined, reflecting the abatement of the acid rain period documented for the upper Vltava by Kop\u00e1\u010dek et al. [8], including decreased fertiliser use in the upper Vltava catchment since 1990. The situation in the German section of the Elbe is comparable\u00a0<\/span>today \u2013 published data from the\u00a0Magdeburg profile are similar to those from H\u0159ensko and Schmilka; however, chloride and sulphate levels there are influenced by the\u00a0relatively mineral-rich Saale River.<\/span><\/p>\n
Input from the\u00a0Upper Elbe and the\u00a0Vltava<\/h3>\n
For comparison of\u00a0inputs, it is necessary to convert concentrations and discharges into transport, which can be quantified in\u00a0units of\u00a0[g\/s] or\u00a0[tons\/yr]. Calculating the\u00a0value of\u00a0concentration and daily discharge yields 12 \u201csituations\u201d per year at regular intervals, which can be used to compute the\u00a0annual total transport. It must be emphasised, however, that a\u00a0substantial portion of\u00a0the\u00a0calculated variation in\u00a0transport is attributable to fluctuations in\u00a0discharge. Fig.\u00a05<\/span><\/em> presents annual transport values in\u00a0tonnes\/year for 2011\u20132020. Total transport at the\u00a0confluence of\u00a0the\u00a0Elbe and the\u00a0Vltava has been added to the\u00a0data from the\u00a0gauging profiles. Given the\u00a0size of\u00a0the\u00a0river, there is no relatively large pollution source between the\u00a0confluence and the\u00a0H\u0159ensko profile (in\u00a0terms of\u00a0the\u00a0ratio of\u00a0discharged wastewater volume to river flow), and the\u00a0difference between the\u00a0summed values reflects the\u00a0effects of\u00a0biological processes along the\u00a0stretch from the\u00a0confluence to H\u0159ensko: the\u00a0gradual nitrification of\u00a0ammonia nitrogen to nitrate, and a\u00a0decline in\u00a0residual BOD with an annual cycle corresponding to phytoplankton production. Temporal changes also show the\u00a0impact of\u00a0the\u00a02013 flood, which significantly increased transport (except at the\u00a0Ob\u0159\u00edstv\u00ed profile, as its catchment was not affected). For most of\u00a0the\u00a0monitored conservative indicators, the\u00a0input from the\u00a0Vltava at the\u00a0confluence is generally slightly higher than from the\u00a0Elbe; however, simple comparisons are problematic, as the\u00a0Vltava regularly has higher summer flows due to releases from Orl\u00edk Reservoir. As seen in\u00a0Figs. 1<\/span><\/em>, 3<\/span><\/em>, and 4<\/span><\/em>, the\u00a0past decade also shows a\u00a0decline in\u00a0total phosphorus and sulphate loads; chloride input has remained fairly constant.<\/span><\/p>\n
<\/a>\n<\/p>\n
<\/p>\n
Fig. 3. Trends in ammonia and nitrate nitrogen concentrations 1961\u20132020<\/h6>\n
<\/a>\n<\/p>\n
Fig. 4. Trends in chloride and sulphate concentrations 1961\u20132020<\/h6>\n
<\/a>\n<\/a>\n<\/p>\n
<\/h6>\n
<\/h6>\n
<\/h6>\n
<\/h6>\n
<\/a><\/h6>\n<\/a><\/h6>\n<\/a>\nFig. 5. Transport\u00a0[tons\/yr] through H\u0159ensko, Ob\u0159\u00edstv\u00ed and Zel\u010d\u00edn profiles 2011\u20132020; OBR+ZEL means the sum of entries at the Vltava\/Elbe confluence<\/h6>\n
A\u00a0civilisational issue \u2013 pharmaceuticals<\/h3>\n
In the previous two chapters, we have shown that pollution in the Czech part of the Elbe catchment is entering a stationary phase, with only the remaining persistent and still unresolved issue of nitrate and phosphorus \u2013 in other words, eutrophication. However, this applies only to the \u201cstandard indicators\u201d; with progress and greater comfort come new pollutants of all kinds. Some are genuinely \u201cnew\u201d, while others are \u201cold\u201d substances that we are now identifying thanks to new analytical methods and a broader interest in environmental quality. One important group consists of pesticides used in agriculture; another is the so-called PPCPs \u2013 \u201cpharmaceuticals and personal care products\u201d \u2013 such as <\/span>dietary supplements, cosmetics, and similar substances. Pesticides enter water bodies from diffuse sources, while pharmaceuticals and PPCPs reach aquatic ecosystems exclusively after use, via sewer systems and municipal WWTPs \u2013 that is, from point sources. These are organic compounds that can be identified as individual chemicals or narrow groups, and are subject to various environmental protection standards, including requirements to determine their environmental toxicity. With pharmaceuticals in\u00a0particular, the\u00a0challenge lies in\u00a0the\u00a0fact that different types of\u00a0toxicity only manifest at concentrations significantly higher than those typically found in\u00a0nature, specifically in\u00a0rivers. These \u201cresidual\u201d concentrations do not act as toxic substances but as biologically active compounds that influence the\u00a0behaviour of\u00a0aquatic communities in\u00a0general, for example, their reproductive cycles or responses to predators. Moreover, these substances act jointly and cumulatively and also pose a\u00a0significant risk to water use. Pharmaceuticals cannot be banned, and their consumption is generally increasing worldwide. According to public reports (State Institute for Drug Control, S\u00daKL), the\u00a0average resident of\u00a0the\u00a0Czech Republic (and Europe) now consumes roughly 650 DDDs (Defined Daily Doses) of\u00a0pharmaceuticals per year; moreover, these reports do not include dermatological applications, such as the\u00a0relatively toxic diclofenac. Fifteen years ago, the\u00a0figure was only around 500 DDDs\u00a0[4], although reporting practices may also have changed. For the\u00a0most commonly used pharmaceuticals, transport via the\u00a0Vltava through Prague and to H\u0159ensko for 2017\u20132020 (n = 48) is presented in\u00a0Fig.\u00a06<\/span><\/em>, adapted from publication\u00a0[11]. Tab.\u00a02<\/span><\/em> is important, as it presents theoretical consumption figures within the catchments of the gauging profiles, calculated based on total pharmaceutical consumption in the Czech Republic and the population of the respective sub-catchments. Seasonal variations in transport can be demonstrated only in certain cases (e.g. medicines for upper respiratory tract infections). The scope of this article does not allow for an analysis of pharmacological studies on excretion rates of the monitored pharmaceuticals by users themselves. Therefore, based on the transport data, only the percentage of pharmaceutical consumption that ends up in rivers was calculated. The highest percentage is observed for Allopurinol\/Oxypurinol, followed by the psychopharmaceuticals Carbamazepine, Gabapentin, Tramadol, and the antibiotic Trimethoprim. As shown in Fig.\u00a06<\/span><\/em>, resistant pharmaceuticals are already entering Prague (as a\u00a0major source area from the\u00a0Vltava catchment) even after passing through the\u00a0Orl\u00edk and Slapy reservoirs, which together have an average retention time of\u00a0over 100 days. Both the\u00a0graph and the\u00a0table refer to the\u00a0\u201cparent compounds,\u201d not to pharmaceutical metabolites, whether excreted directly by patients, transformed in\u00a0WWTPs, or further transformed in\u00a0the\u00a0watercourse itself. Some metabolites are known and monitored (e.g. ibuprofen metabolites); however, in\u00a0most cases such analyses are rare for various reasons.<\/span><\/p>\n
<\/p>\n
<\/a>\nFig. 6. Transport of pharmaceuticals through profile Hrensko; sequence on the X-axis corresponds to that in Tab. 2<\/em><\/h6>\n
Tab.\u00a02. Transport and consumption of pharmaceuticals in the whole basin<\/h5>\n
<\/a>\nFurther analysis can be conducted using WHO data on the\u00a0excretion of\u00a0consumed pharmaceuticals, although this inevitably increases the\u00a0degree of\u00a0uncertainty and speculation. For example, Metformin\u00a0and Gabapentin\u00a0are reported to be excreted 100\u00a0% as the\u00a0parent compound, as is the\u00a0active metabolite Oxypurinol for Allopurinol. A\u00a0fundamental problem remains that effective technological processes for the\u00a0removal of\u00a0all pharmaceuticals in\u00a0WWTPs are not yet available. Although the\u00a0increasingly implemented advanced treatment of\u00a0drinking water sourced from surface waters offers protection to consumers, this does not address the\u00a0core issue at its source. Once again, we must rely on the\u00a0new Directive 2024\/3019\u00a0[12], which aims to gradually tackle this problem. The\u00a0further fate of\u00a0pharmaceuticals along the\u00a0stretch from H\u0159ensko to the\u00a0sea can only be speculated upon, based on the\u00a0limited data available from the\u00a0FGG Elbe servers\u00a0[18]. Currently, only data from the\u00a0year 2023 are available for comparison. In\u00a0general, concentrations correspond to those observed in\u00a0the\u00a0Czech Republic; however, the\u00a0difference is that on the\u00a0315 km-long section from Schmilka (the\u00a0border) to Magdeburg, there are no relatively large sources (the\u00a0ratio of\u00a0WWTP output to river flow is low). Metformin\u00a0concentrations decrease along this stretch, while concentrations of\u00a0Carbamazepine, on the\u00a0other hand, increase. Pharmaceutical consumption and the\u00a0level of\u00a0WWTP treatment are certainly comparable.<\/span><\/p>\n
DISCUSSION<\/h2>\n
In\u00a0the\u00a0previous chapter, based on the\u00a0results we demonstrated that pollution in\u00a0the\u00a0lower reaches of\u00a0the\u00a0Czech sections of\u00a0the\u00a0Elbe and Vltava rivers continues to decrease; however, the\u00a0problems of\u00a0eutrophication persist, and new pollutants are emerging. This implies further development in\u00a0water quality monitoring, both in\u00a0terms of\u00a0analyses and in\u00a0the\u00a0evaluation of\u00a0their results. Besides the\u00a0search for and monitoring of\u00a0additional pollutants, it is essential to improve the\u00a0sensitivity of\u00a0methods for detecting \u201cstandard\u201d pollutants, because they have not disappeared; rather, their concentrations have fallen below the\u00a0detection limits of\u00a0current methods. This is especially critical for pharmaceuticals, but it also applies, for example, to mercury and ammonia nitrogen. <\/span><\/p>\n
An analysis of\u00a0these issues and general guidelines for addressing them (including ways to establish limits) are provided, for instance, in\u00a0the\u00a0European standard \u010cSN\u00a0ISO\u00a0EN\u00a05667-20\u00a0[13]; nevertheless, the\u00a0issue of\u00a0overall assessment remains, as described in\u00a0the\u00a0introduction to this article.<\/span><\/p>\n
There are two types of\u00a0pollution sources, which differ significantly both in\u00a0the\u00a0nature of\u00a0the\u00a0substances they produce and in\u00a0their characteristics. Diffuse sources are fundamentally dependent on the\u00a0annual cycle (including agricultural activities) and precipitation. Point sources represent a\u00a0steady (or predictable) input in\u00a0terms of\u00a0the\u00a0content and \u201cproduction\u201d of\u00a0substances; however, they typically discharge treated wastewater into variable rivers or recipients. The\u00a0amount of\u00a0pollution in\u00a0watercourses further depends on in\u00a0situ<\/span> transformation processes, which are influenced by temperature as well as flow (dilution and longitudinal transport). The\u00a0temperature cycle fundamentally influences the\u00a0transformations of\u00a0nitrogen (nitrification, possibly denitrification and losses to the\u00a0atmosphere), organic carbon (BOD-5 and COD), and phytoplankton production (chlorophyll-a\u00a0concentration), since phosphorus, as a\u00a0key component of\u00a0eutrophication, is generally in\u00a0surplus in\u00a0large rivers. In\u00a0contrast, conservative constituents such as chloride and sulphate remain\u00a0unchanged in\u00a0the\u00a0watercourse. When calculating transport (concentration \u00d7 flow), it generally holds that concentrations are relatively conservative components, and the\u00a0main\u00a0cause of\u00a0variability is fluctuation of\u00a0flow values. Regarding the\u00a0development of\u00a0concentrations of\u00a0\u201cstandard water quality indicators\u201d: ammonia nitrogen concentrations have decreased since their peak around 1985 to levels reported in\u00a0the\u00a0Elbe by Ullik in\u00a01887, and also \u201cbelow Prague\u201d in\u00a01913\u00a0[2, 3]. However, current concentrations remain\u00a0stable at around 4\u00a0mg\/l of\u00a0nitrate nitrogen, which was a\u00a0relatively unknown anion in\u00a0their time. Currently, we must acknowledge the\u00a0\u201cnitrogen paradox\u201d\u00a0[14], which essentially states that the\u00a0cleaner a\u00a0(large) river is, the\u00a0higher its nitrate nitrogen concentrations tend to be. Given the\u00a0significant contribution from diffuse sources, the\u00a0possibility of\u00a0reduction is nowhere near. As opposed to phosphorus in\u00a0inland waters, nitrogen is the\u00a0key problem for the\u00a0sea, and the\u00a0risk of\u00a0ocean eutrophication is already manifesting in\u00a0coastal seas\u00a0[15]. We also currently observe significantly higher concentrations of\u00a0chloride and sulphate, as well as phosphorus, although the\u00a0issue of\u00a0eutrophication in\u00a0the\u00a0entire river network is only about 50 years old.<\/span><\/p>\n
Phosphorus, as opposed to carbon and nitrogen, cannot leave the\u00a0river and return to the\u00a0atmosphere, and is gradually transported downstream to the\u00a0sea. Its transport can therefore be compared with the\u00a0balance of\u00a0inputs into the\u00a0catchment. Several reports of\u00a0annual performance by municipal WWTPs are available, with the\u00a0most comprehensive and accessible being the\u00a0ISVS. According to ISVS (2022), annual phosphorus discharges from WWTPs within\u00a0the\u00a0H\u0159ensko profile catchment ranged between 450 and 540 tonnes per year in\u00a02018, 2020, and 2022. Transport through the\u00a0H\u0159ensko profile showed considerably greater variability (due to differences in\u00a0flow), ranging from 580 to 1,070 tonnes per year. Phosphorus removal efficiency in\u00a0WWTPs was approximately 87\u00a0%, which, among other things, is the\u00a0efficiency required by the\u00a0new UWWTD directive\u00a0[12] only<\/span> by 2039. Overall, the\u00a0proportion of\u00a0phosphorus transport through the\u00a0H\u0159ensko profile in\u00a0individual years corresponds to 50\u201377\u00a0% of\u00a0the\u00a0discharge reported by municipal WWTPs in\u00a0the\u00a0catchment. Only WWTPs serving more than 1,000 population equivalents were included in\u00a0the\u00a0calculation. However, from the\u00a0perspective of\u00a0the\u00a0overall phosphorus balance, the\u00a0reported WWTP discharges represent a\u00a0significant underestimate, as they do not account for combined sewer overflows. Assuming that just 10\u00a0% of\u00a0untreated wastewater enters recipients through overflows during the\u00a0year, and given the\u00a0current phosphorus removal efficiency of\u00a085\u00a0%, the\u00a0total load from WWTPs and sewer overflows would already exceed the\u00a0reported discharges by more than 50\u00a0%. Combined sewer overflows are currently the\u00a0subject of\u00a0intensive research, so the\u00a0estimates presented here will surely be refined in\u00a0the\u00a0near future. However, discharge data are only available for total phosphorus, not for phosphate phosphorus, which strongly correlates with chlorophyll-a\u00a0concentration \u2013 the\u00a0key indicator of\u00a0phytoplankton biomass. The\u00a0debate on how low phosphorus concentrations must be (and must be kept) continues and is likely to continue for some time. Nevertheless, the\u00a0balance suggests that undesirable phytoplankton production can indeed be limited by significantly reducing phosphorus discharges from municipal sources. This reduction must involve not only improved removal technologies at WWTPs but also better functioning of\u00a0sewer systems. This aligns with the\u00a0gradually introduced requirements of\u00a0the\u00a0new European Urban Wastewater Treatment Directive (2024\/3019 EU)\u00a0[12].<\/span><\/p>\n
As already mentioned, technically feasible methods for the\u00a0systematic removal of\u00a0pharmaceuticals (and other PPCPs) in\u00a0municipal WWTPs are not yet available. Pharmaceuticals are a\u00a0group of\u00a0highly diverse organic compounds that, apart from nonspecific pollution, do not constitute a\u00a0significant substrate (i.e. carbon source) for microbial communities in\u00a0WWTPs, and therefore do not trigger the\u00a0selection of\u00a0specific metabolic pathways. Their degradation thus proceeds primarily through cometabolism with the\u00a0standard sewage load, mediated by rather nonspecific bacterial oxidases, and occurs gradually, often producing unknown intermediate products or metabolites. Therefore, progress in\u00a0this area is expected to be slow and must begin\u00a0with support for systematic monitoring of\u00a0pharmaceuticals in\u00a0WWTPs and watercourses.<\/span><\/p>\n
CONCLUSION<\/h2>\n
We have analysed archival data on water quality in\u00a0the\u00a0lower reaches of\u00a0the\u00a0Czech sections of\u00a0the\u00a0Elbe and Vltava rivers \u2013 border profile H\u0159ensko and profiles Ob\u0159\u00edstv\u00ed and Zel\u010d\u00edn at the\u00a0confluence of\u00a0the\u00a0Elbe and Vltava.<\/span><\/p>\n
Water quality in\u00a0the\u00a0lower Elbe has improved significantly and has remained stable since 1995\u20132020.<\/span><\/p>\n
Ammonia nitrogen, after peaking in\u00a0the\u00a01980s, has almost disappeared; however, it has been replaced by persistently high concentrations of\u00a0nitrate nitrogen, which is transported downstream to the\u00a0ocean. The\u00a0nitrogen balance in\u00a0river systems is complicated by exchanges with the\u00a0atmosphere, particularly through denitrification processes that produce nitrous oxide. At present, a\u00a0substantial proportion of\u00a0nitrate nitrogen originates from diffuse sources.<\/span><\/p>\n
Phosphorus (determined as Ptotal<\/span>) remains in\u00a0excess in\u00a0the\u00a0rivers, with municipal WWTPs representing a\u00a0major source; total phosphorus loads discharged within\u00a0the\u00a0catchment correspond to well over 50\u00a0% of\u00a0transport measured at the\u00a0gauging profiles. Eutrophication remains generally high, and the\u00a0elevated primary production of\u00a0phytoplankton in\u00a0reservoirs and lower river reaches is influenced mainly by seasonal dynamics and the\u00a0hydromorphology of\u00a0the\u00a0watercourses. As opposed to the\u00a0past, the\u00a0annual cycle of\u00a0BOD-5 values at the\u00a0monitored profiles is now significantly influenced by phytoplankton production. New pollutants such as pesticides and pharmaceuticals have also emerged. The\u00a0input of\u00a0pharmaceuticals occurs year-round, and the\u00a0prospects for their complete removal at wastewater treatment plants remain\u00a0limited.<\/span><\/p>\n
It is necessary to take into account the\u00a0impact of\u00a0climate change on watercourses. In\u00a0general, it leads to an increase in\u00a0maximum summer water temperatures (resulting in\u00a0higher respiratory activity and lower oxygen solubility), prolonged drought periods (with very low flows), and intense torrential rainfall events (which typically trigger sewer overflows). Current regulations governing wastewater discharges do not yet adequately reflect these conditions. Requirements for monitoring sewer overflows and for considering the\u00a0\u201crecipient characteristics\u201d \u2013 specifically, the\u00a0proportion of\u00a0discharged wastewater in\u00a0the\u00a0river flow at the\u00a0discharge point (monitored over five years) \u2013 are only now being introduced in\u00a0the\u00a0newly adopted UWWTD\u00a0[12]. In\u00a0the\u00a0Czech Republic, there are nearly 1,000\u00a0municipal WWTPs (according to ISVS) serving more than 1,000 inhabitants, and at least 60 of\u00a0them discharge more than 50\u00a0% of\u00a0the\u00a0recipient\u2019s\u00a0flow during dry weather conditions\u00a0[16]. The\u00a0working database (WWTP performance vs. flows at discharge points) is still being refined. <\/span><\/p>\n
\u00a0<\/span>Since 2000, Czech legislation has failed to even meet the\u00a0letter of\u00a0Section 36 of\u00a0the\u00a0Water Act, which concerns the\u00a0minimum residual flow and its determination. This provision underpins the\u00a0requirements for the\u00a0\u201cenvironmental flow\u201d included in\u00a0the\u00a0UWWTD and other European documents. If progress in\u00a0pharmaceutical degradation is slow due to real technical challenges, could legislative progress be even slower?<\/span><\/p>\n
Acknowledgements<\/h3>\n
Preparation of\u00a0the\u00a0text was possible thanks to projects supported by the\u00a0Technology Agency of\u00a0the\u00a0Czech Republic, no. SS02030018 \u201cCentre for Landscape and Biodiversity, WP C3 (DivLand)\u201d and no. SS02030008 \u201cCentre for Environmental Research, WP 2A\u201d (CEVOOH). The\u00a0possibility to calculate pharmaceutical transport, which has already been published in\u00a0outline\u00a0[14], is the\u00a0result of\u00a0collaboration with colleagues from the\u00a0state enterprises Povod\u00ed Vltavy and Povod\u00ed Labe.<\/span><\/span><\/em><\/p>\n
The\u00a0Czech version of\u00a0this article was peer-reviewed, the\u00a0English version was translated from the\u00a0Czech original by Environmental Translation Ltd.<\/p>\n","protected":false},"excerpt":{"rendered":"
The paper presents an analysis of water quality data from the downstream part of the Czech Elbe and the Vltava for the period 1961\u20132020 and compares it with archive data (reference period 1880\u20131913). The transport of nitrogen and total phosphorus within the catchment was compared with the output from wastewater treatment plants (WWTPs). <\/p>\n","protected":false},"author":8,"featured_media":36027,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[86,93],"tags":[1062,1189,3895,1182,1106,453,3894],"coauthors":[329],"class_list":["post-36269","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-hydraulics-hydrology-and-hydrogeology","category-two-articles","tag-elbe","tag-eutrophication","tag-health","tag-nitrogen","tag-pharmaceuticals","tag-phosphorus","tag-wastewater-treatment-plants"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/36269","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/comments?post=36269"}],"version-history":[{"count":6,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/36269\/revisions"}],"predecessor-version":[{"id":36278,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/36269\/revisions\/36278"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media\/36027"}],"wp:attachment":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media?parent=36269"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/categories?post=36269"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/tags?post=36269"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/coauthors?post=36269"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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