![\"\"](\"https:\/\/www.vtei.cz\/wp-content\/uploads\/2024\/02\/Fiala-obr-1-1.jpg\")
<\/a>\nFig.\u00a01. An example of a\u00a0significant change in phosphorus concentrations in\u00a0the\u00a0longitudinal profile downstream from Nov\u00e9 Straec\u00ed (5,500 inhab.) on\u00a0November\u00a010, 2015, when 95\u00a0% of the\u00a0flow in the\u00a0Straeck stream (5.0 km) consisted of WWTP discharge. Total phosphorus concentration decreased slightly from 7.4\u00a0mg\/l in the\u00a0WWTP outlet to 3.1 mg\/l and 2.3 mg\/l above and below Konopas pond, respectively, which was drained completely at the\u00a0time. In the\u00a0lower part of\u00a0the\u00a0stream, retention was significant and the\u00a0concentration dropped to 0.210 mg\/l at the\u00a0confluence with Lodnice river. Particulate phosphorus (PP) is the\u00a0difference between total and dissolved reactive phosphorus (PO4-P)<\/h6>\n
At the same time, it is true that the cycle of phosphorus in lake and reservoir ecosystems has been studied since the beginning of limnology with regard to the then prevailing sources, i.e. \u201censuring\u201d chronic supply. On the other hand, the impact of phosphorus from occasional, albeit significant episodes without distinction (if it is an episode of erosion or sewer overflow during the rains) is much less studied, or quantification of episodes is much more difficult [9], let alone generalization. In river ecosystems, the dichotomy is similar, but the total\u00a0amount of directly measured data is incomparably smaller. It can therefore be summarized at the\u00a0outset that the\u00a0weakest point of our budget models is currently the\u00a0directly measured retention of phosphorus in streams, and episodic retention has received the\u00a0least attention.<\/p>\n
Since phosphorus (due to the\u00a0absence of a\u00a0gaseous state) is not \u201clost\u201d anywhere in the\u00a0river network, nor does it accumulate in the\u00a0long term (unfortunately, from a\u00a0functional point of view, we separated the\u00a0floodplain meadows from the\u00a0rivers); on the\u00a0other hand, to start with, it is not a\u00a0big mistake if its retention is \u201cannulled\u201d in the\u00a0long run. However, we must not forget this assumption at the\u00a0moment when in the\u00a0model we confront, for example, annual data from operational monitoring with real relationships from the\u00a0basin, or by in-situ measured concentrations. While sampling usually covers the\u00a0proverbial 12 seconds per year and we hope for their problem-free extrapolation to 365 days, in the\u00a0interim there are apparently multiple to orders of magnitude changes in temporal retention [10]. And while in stream models there is usually nothing real to remind us of this error in assumption, in backwaters (where significant phosphorus accumulation from such episodes eventually occurs) it is the\u00a0cyanobacterial blooms that give clear feedback to our theoretical models. After all, the\u00a0results of each model must be properly interpreted, which cannot be done other than through a\u00a0responsible author who knows the\u00a0real environment.<\/p>\n
The above-mentioned state of knowledge of phosphorus retention in aquatic ecosystems is given, among other things, by historically available methods. Methods based on radionuclide tracers are very limited outside the\u00a0laboratory due to health risks. The\u00a0differential measurement of concentrations \u201cat\u00a0the\u00a0beginning\u201d and \u201cat the\u00a0end\u201d of the\u00a0examined part of the\u00a0ecosystem therefore have dominated the\u00a0methods for a\u00a0long time. Only the\u00a0formulation and development of the\u00a0\u201cRiver Continuum Concept \u201c [11] and the\u00a0\u201cNutrient Spiralling concept\u201d [12] derived from it enabled the\u00a0development of new methods based on observing the\u00a0induced response of the\u00a0entire ecosystem. At the\u00a0beginning, radionuclides were still used [13], but before long, more sensitive procedures using non-conservative markers in addition to simple nutrients were developed. Regardless of the\u00a0chemical nature of the\u00a0substances, however, the\u00a0first wave of new methods consisted of reaching plateau values, steady-state equilibrium, in the\u00a0monitored section, and that for a\u00a0non-negligible long time. Such an experiment provided only one unique value for a\u00a0given section. A\u00a0comparison of the\u00a0results from different locations revealed a\u00a0large range of the\u00a0three determined spiraling metrics: uptake length (SW), areal uptake (U), and uptake velocity (vf). Therefore, a\u00a0methodological refinement followed; during one measurement, the\u00a0plateau concentration was gradually increased in several consecutive steps [14]. From this differentiated series of measurements, the\u00a0parameters of the\u00a0nutrient spiraling were extrapolated towards unaffected conditions with much higher accuracy. However, with such a\u00a0procedure, the\u00a0examined river section was exposed to such a\u00a0high load in total that some authors doubted the\u00a0reliability of the\u00a0data obtained in this way for common ranges of background measurements [15].<\/p>\n
In methodology, the\u00a0latest innovation is thus TASCC method (Tracer Additions for Spiraling Curve Characterization) [16], where the\u00a0response on a\u00a0known section of the\u00a0watercourse is induced only by a\u00a0one-time addition (slug injection) of a\u00a0mixture of enriching nutrients and a\u00a0conservative marker. Unlike the\u00a0previous methods, each sub-sample taken from the\u00a0resulting wave is used to calculate one particular value, i.e. the\u00a0derivation of three spiraling metrics (SW, U\u00a0a\u00a0vf); it does not only take place by interpolating two or three points (corresponding to two or three steady-state concentrations), but by calculating a\u00a0regression line over a\u00a0large set of points. Such a\u00a0procedure not only leads to higher statistical reliability, but mainly to higher factual accuracy of the\u00a0calculated spiraling parameters characterizing nutrient retention (in our case phosphorus retention).<\/p>\n
In their work [16], Covino et al. consistently distinguish three groups of spiraling metrics, or three sub-levels of nutrient uptake (U), which are gradually calculated and derived using the\u00a0given procedure (SW a\u00a0vf): ambient uptake (Uamb) is the\u00a0desired target quantity characterizing the\u00a0river\u2019s\u00a0own spiral in unaffected conditions, towards which all methods should aim; added nutrient uptake (Uadd) is an artificially increased part of the\u00a0uptake caused by the\u00a0experimental addition of nutrients, i.e. an increase in uptake due to the\u00a0induction itself; and finally, total uptake (Utot) is the\u00a0sum of both mentioned sub-components and the\u00a0only value directly obtained by chemical analysis of samples taken. Unlike total uptake, the\u00a0two partial values can only be derived mathematically.<\/p>\n
Like any method, TASCC has its limitations; however, the\u00a0main advantages include health safety (compared to isotopes) and significantly less burden on the\u00a0studied ecosystem (compared to steady-state methods). Most of the\u00a0few works in which it has been used so far [17\u201326] deal with nitrogen retention but show its applicability both on a\u00a0wider range of watercourse sizes and on a\u00a0larger geographical distribution.<\/p>\n
In the\u00a0Czech Republic, TASCC method has not yet been used, despite the\u00a0fact that it offers considerable potential in refining budget models. The\u00a0goal of our study is, therefore, the\u00a0implementation of the\u00a0method and assessment of its suitability for direct measurement of phosphorus retention in watercourses depending on predictable parameters. In the\u00a0ideal case, we hope that the\u00a0method will help us to achieve a\u00a0good ecological status more effectively, or economically suppress the\u00a0manifestations of eutrophication in our degraded water ecosystems through more reliable modelling of processes (i.e. retention in the\u00a0hydrographic network).<\/p>\n
METHODS AND LOCATION<\/h2>\n
The Lhotsk stream (second order according to Strahler), originating 8 km east of Beneov, is a right-hand tributary of the Petroupimsk stream, whose\u00a0waters flow through the\u00a0Beneovsk stream near erany into the\u00a0S\u00e1zava river. The\u00a0highest point of the\u00a0catchment (2.6 km2) is Koch\u00e1nov hill (499 m above sea level), while the\u00a0mouth (360 m above sea level) is only 1.46 km away. The\u00a0predominant soil type is modal cambisol on a\u00a0bedrock of heavily weathered granites. The\u00a0catchment (Fig.\u00a02<\/em>) is dominated by arable land (82\u00a0%), with the\u00a0minority occupied by forest (8\u00a0%) and permanent grassland (4\u00a0%). Due to the\u00a0steepness of the\u00a0land, the\u00a0skeletal nature of the\u00a0soils, ploughing, systematic drainage (29\u00a0%), and farming methods, the\u00a0basin is regularly and long-term affected by severe erosion. The\u00a0Lhotsk stream (2.2 km) flows completely outside human settlements; therefore, the\u00a0transported phosphorus (P) comes exclusively from non-point sources, and agricultural land has the\u00a0decisive share of the\u00a0P transfer.<\/p>\n In the\u00a0closing part of the\u00a0basin (GPS 49\u00b0 48\u201913.192\u2019\u2019N; 14\u00b0 45\u201938.902\u2019\u2019E), the\u00a0stream flows through two morphologically different sections, which we used for research. In the\u00a0upper section (hereafter called the\u00a0canal), the\u00a0stream is completely straightened, deepened with a\u00a0bottom paved with solid concrete tiles. Apart from a\u00a0solitary group of willow bushes, the\u00a0steep banks are only covered with herbaceous ruderal vegetation (5\u201315 m), strongly overgrown with reeds at the\u00a0lower end. On the\u00a0other hand, in the\u00a0lower section (hereafter called meanders) the\u00a0stream meanders through an almost natural bed in a\u00a0wider floodplain and is lined on both banks by a\u00a0continuous strip of densely stratified tree and shrub vegetation (10\u201320 m). The\u00a0riverbed is made up of different material, from boulders to coarse sand, depending on the\u00a0prevailing velocities of the\u00a0current. In both morphologically different parts of the\u00a0riverbed, we defined two 200 m long experimental sections, which are separated only by a\u00a0road culvert and about 20 m apart. Although we only used the\u00a0channelized section for the\u00a0initial measurement of P retention using TASCC method, we also monitored the\u00a0same wave of water enriched with tracer mixture on the\u00a0natural section of the\u00a0meanders, albeit only through conductivity electrodes. From the\u00a0measured conductivity curves, we derived the\u00a0advance velocities on both sections. For the\u00a0future comparison of the\u00a0retention of two different types of bed, we therefore assume that the\u00a0two sections do not differ either hydrologically or hydro-chemically, and the\u00a0most significant difference in the\u00a0investigated retention will be due to morphological differences.<\/p>\n Based on the\u00a0long-term monitoring of this site and for future comparison of the\u00a0two sections, it is worth noting that, unlike the\u00a0channelized section, the\u00a0unpaved bed of the\u00a0natural section is intensively reshaped cyclically by abundant episodes of high flows. During longer hydrological calm periods, fine sediments also settle in the\u00a0riverbed, which, if accumulating for a\u00a0longer period of time, form loamy to clayey benches. Due to the\u00a0abundant supply of leaf litter and fallen branches that get caught in meanders and on boulders, a\u00a0characteristic layer of sapropel is formed, gradually covered with a\u00a0fine biofilm, in numerous stream pools on the\u00a0surface of fine sediments. These structures are washed away with flush run-off, together with benthos. In contrast, due to high sun exposure, the\u00a0thin biofilm in the\u00a0upper section is formed by a\u00a0characteristically solid coating of epilithic algae which, in addition to hydrological changes (scouring), is also subject to seasonal dynamics. As a\u00a0result, in the\u00a0meandering part of the\u00a0stream there is usually a\u00a0much larger area of active surfaces where retention can take place (both biological and physico-chemical).<\/p>\n For the\u00a0initial measurement of phosphorus retention according to TASCC method [16], we added a\u00a0mixture of a\u00a0conservative component (NaCl), which serves as a\u00a0marker easily detectable by a\u00a0conductivity electrode, and a\u00a0non-conservative component (NH4H2PO4), whose retention is the\u00a0subject of research, to the\u00a0channelized section of the\u00a0Lhotsk stream. According to the\u00a0method, we chose the\u00a0amount of added phosphorus so that the\u00a0maximum concentration at the\u00a0end of the\u00a0measured section reached the\u00a0recommended \u201csaturation\u201d level. The\u00a0saturation concentration is formally derived from enzymatic kinetics according to Michaelis-Menten, and therefore corresponds to the\u00a0concentration at which the\u00a0given reaction rate reaches its maximum. However, during the\u00a0practical calculation of spiraling metrics in an anthropogenically unaffected and slightly affected watercourse, it is indicated that the\u00a0dynamic concentration must be increased two to five times, at most ten times above the\u00a0background concentration level [16, 19, 26]. To calculate it, it was necessary to measure the\u00a0background value of the\u00a0P concentration, determined as the\u00a0concentration of dissolved orthophosphates (PO4-P), and the\u00a0flow rate (Q), but also the\u00a0arrival time, i.e. the\u00a0hydromorphological character of the\u00a0watercourse. Since the\u00a0last two characteristics essentially determine the\u00a0course of the\u00a0\u201cflattening\u201d of the\u00a0concentration curve and depend mainly on the\u00a0relative volume of the\u00a0so-called dead zones (almost stagnant water in deep pools and hyporheal), which can be difficult to determine without prior measurement, we initially only roughly estimated both parameters.<\/p>\n In the\u00a0autumn (October 21, 2021) we carried out an experimental measurement of phosphorus retention using TASCC method in the\u00a0Lhotsk stream. In the\u00a0200 m long section, marked \u201ccanal\u201d, water flowed only over the\u00a0surface of the\u00a0concrete tiles (average width of the\u00a0surface 74.8 cm); therefore, phosphorus retention was almost entirely caused by sorption to this minimal area and, to a\u00a0limited extent, also by uptake of nutrients by a\u00a0small amount of attached organisms. The\u00a0only deviation from the\u00a0uniform shape of the\u00a0riverbed was one larger and two smaller bank scours with a\u00a0total length of about 15 m, where the\u00a0riverbed left the\u00a0canal.<\/p>\n We placed three conductivity probes (HACH HQ 40d or WTW Multi 3320) on the\u00a0measured section of the\u00a0stream, enabling automatic data storage. The\u00a0first was below the\u00a0point of thorough mixing (0 m), the\u00a0second in the\u00a0middle of the\u00a0section (100 m), and the\u00a0third in the\u00a0section closing profile (200 m). Using online conductivity measurements on the\u00a0closing profile, we took a\u00a0sequence of samples (wide-mouthed HDPE sample containers 0.5\u00a0l) covering the\u00a0ascending and descending part of the\u00a0conductivity wave, or the\u00a0passage of changing concentrations and ratios of monitored nutrients and tracer. We arbitrarily changed the\u00a0time interval between individual samples according to the\u00a0rate of the\u00a0changing conductivity; as a\u00a0result, it ranged from 5 minutes to 30 seconds. We stopped sampling after the\u00a0induced conductance had stabilized to the\u00a0background value.<\/p>\n Samples for the analysis of nutrients and chlorides (PO4-P, NH4-N, Cl-) and for basic chemical analysis (carried out within 24 hours in the accredited TGM WRI laboratory) were cooled with ice during transport. From the measured values,\u00a0i.e. changes in the\u00a0ratio of phosphorus and chloride loss, or biologically active nutrient to conservative tracer, all three spiraling metrics were calculated in several mathematical steps (see equations 8\u201310 in Covino et al. 2010) according to TASCC method [16]. According to \u201cNutrient Spiralling Concept\u201d [13], these are uptake length (SW) [m], areal uptake (U) [g.m-2.s-1], and uptake velocity (vf)\u00a0[m.s\u20131].<\/p>\n The uptake length (SW) is a\u00a0basic parameter indicating the\u00a0theoretical distance for which the\u00a0average nutrient atom is transported by the\u00a0watercourse between two points of the\u00a0bottom from the\u00a0output (or release from the\u00a0bottom) to its uptake (or binding to the\u00a0bottom). Since the\u00a0SW is strongly influenced by the\u00a0flow rate and velocity, or the\u00a0water depth in the\u00a0stream, outside of the\u00a0retention process itself, it is appropriate (especially for the\u00a0purpose of comparing different watercourses with each other or for comparing individual measurements carried out in the\u00a0same watercourse, but under different hydrological conditions) to introduce a\u00a0normalized quantity that converts these differences into a\u00a0unit dimension. These quantities are areal uptake (U) and uptake velocity (vf). While the\u00a0areal uptake (U) indicates the\u00a0total amount of nutrient received per unit time per unit area of a\u00a0riverbed, the\u00a0uptake velocity (vf) corrects the\u00a0uptake length to flow velocity and water depth (for details, see equations 8.6\u20138.10; interpretation and graphic manual in the\u00a0methodological instructions [12]), thereby enabling mutual comparability of locations and periods of P retention measurement.<\/p>\n To calculate individual parameters of the\u00a0spiral, we also measured the\u00a0morphology of the\u00a0flooded part of the\u00a0canal (Fig.\u00a03<\/em>), i.e. the\u00a0surface width (cross section every 10 m) and depth (every 10 cm on the\u00a0given cross section) and calculated the\u00a0wetted perimeter. All three parameters of the\u00a0spiral, the\u00a0so-called metric triad (see [12]) are mutually mathematically convertible quantities, and are thus in fact closely linked with each other. We derived the\u00a0flow rate (the only quantity that unambiguously and reliably compares morphology of the\u00a0channelized and natural stream section under current hydrological conditions) from the\u00a0arrival time, i.e. from the\u00a0interval between the\u00a0maximum conductivity on the\u00a0first (0 m) and the\u00a0last profile (200 m). The\u00a0flow rate (Q) was measured by the\u00a0direct method on the\u00a0gauging weir according to Cipoletti, ex post installed in the\u00a0culvert, i.e. between the\u00a0two sections. We consider the\u00a0differences on the\u00a0upper and lower edges of the\u00a0examined section to be marginal. We measured Q only after the\u00a0wave had passed, so that the\u00a0hydraulic shock caused by the\u00a0installation of the\u00a0weir would not change the\u00a0retention \u201ccapacities\u201d, i.e. the\u00a0mechanical rearrangement of leaves, branches, and sediments.<\/p>\n To measure the spiraling metrics, we used a mixture of NaCl solutions (conductivity = 25.0 mS\/cm, 4 l) and NH4H2PO4 (PO4-P = 152 mg\/l, 4 l). We poured the entire volume of the tracer solutions within five seconds onto a gravel chute just above the measured section to ensure thorough mixing while not stirring the sediment. We determined the loading according to the concentrations of NH4-N and PO4-P in the reference sample (0.019 and 0.024 mg\/l) and the flow rate (2.4 l\/s) determined the day before. Just before measurement, we took three control samples, namely at the beginning and end of the straightened section and at the end of the meander section. For the calculations of spiraling metrics, a sample from the upper edge of the experimental section (0.010 and\u00a00.041 mg\/l) was used as the\u00a0background value of NH4-N and PO4-P; this is because the\u00a0middle sample was contaminated by disturbed creatures moving in the\u00a0riverbed. The\u00a0phosphorus concentration of the\u00a0sample taken in the\u00a0third, lowest profile differed from the\u00a0first by up to 5\u00a0%. From the\u00a0values found during the\u00a0wave passage (Fig.\u00a04<\/em>), it is clear that during the\u00a0experiment there was an optimal increase in concentrations by the\u00a0required two to five times stated in the\u00a0literature [16, 19, 26].<\/p>\n <\/p>\n At the\u00a0current flow rate (2.3\u00a0l\/s) and at a\u00a0logging interval of 10\u201330 s, a\u00a0flow velocity of 5.76 m\/min (0.096 m\/s) was measured. The\u00a0resulting very fast wave passage (35 min from pouring, or from the\u00a0wave passage through the\u00a00 m profile to the\u00a0collection of the\u00a0last sample on the\u00a0200 m profile), we captured a\u00a0total of 20 samples with the\u00a0shortest interval of 30 s\u00a0around maximum conductivity (Fig.\u00a04<\/em>). By synchronous measurement of conductivity in the lower section marked \u201cmeanders\u201d, we found a significantly lower flow velocity (3.60 m\/min)\u00a0given by the\u00a0natural character of the\u00a0riverbed and proving the\u00a0preliminarily decisive influence of the\u00a0watercourse hydromorphological status (Fig.\u00a03<\/em>) on the\u00a0retention of P in the\u00a0stream; this is because differences in the\u00a0slope of the\u00a0riverbed are minimal.<\/p>\n By integrating the\u00a0concentration curve using the\u00a0trapezoidal method, we found that the\u00a0wave passage in the\u00a0straightened section (200 m) resulted in retention of 353 mg of added phosphorus (38.8\u00a0%) and only 3.0\u00a0% of added chlorides. Subsequently, the\u00a0total areal uptake is U\u00a0= 0.714 [mg\/m2.s], whereby at the\u00a0geometric mean of the\u00a0background-corrected concentration (0.114 mg\/l) we obtain the\u00a0total uptake velocity vf = 0.376 [mm\/min]. Using the\u00a0original methodology [16], by extrapolation for ambient condition we obtain the\u00a0following spiraling metrics values: SW amb = 70.8 [m]; Uamb = 0.000000178 [mg\/m2.s] and vf amb = 0.00936 [mm\/min], which are very low and practically zero for the\u00a0last two quantities.<\/p>\n If we consider the\u00a0coefficients of variance of the\u00a0three calculated spiraling metrics (R2 for SW = 0.92, for U\u00a0= 0.97, and for vf = 0.13), it is also clear that the\u00a0dependence of total absorption rate on concentration is insignificant while, in contrast, it is very high for the\u00a0uptake length and the\u00a0total areal uptake (Fig.\u00a05<\/em>). Although we did not observe any changes in flowing water during measurement (neither turbidity nor a\u00a0change in the\u00a0level), we were convinced by a\u00a0random error of the\u00a0extreme sensitivity of the\u00a0correlation of partial uptake lengths (SW) to the\u00a0phosphorus concentration, or to small inaccuracies caused by sampling. When a\u00a0sub-sample was taken at 4:01 p.m., fine sediment was probably stirred up because the\u00a0measured concentrations deviate significantly from the\u00a0otherwise smooth course. By subsequently omitting this outlier, the\u00a0correlation coefficient improved dramatically (from the\u00a0original value of\u00a0R2\u00a0=\u00a00.73\u00a0to\u00a0R2\u00a0= 0.92).<\/p>\n <\/p>\n A\u00a0comparison with other works also shows that the\u00a0most robust value\u00a0\u2013 uptake length\u00a0\u2013 is at the\u00a0lower limit of observations at lightly polluted locations [26]; in other words, it is very short. Since the\u00a0uptake length value (SW) is strongly dependent on the\u00a0actual flow (or current velocity and depth), the\u00a0normalized values of areal uptake (U) and total uptake velocity (vf) are used to compare the\u00a0sites. However, the\u00a0authors (who, as in our case, were faced with their atypical courses or values) make the\u00a0fundamental assumption to explain the\u00a0discrepancies, that the\u00a0whole theory behind the\u00a0calculation of the\u00a0spiraling metrics is valid only in the\u00a0range of conditions under saturation [25, 27], i.e. the\u00a0addition of nutrients must significantly induce its uptake. In our case, this would mean (providing that we want to avoid the\u00a0application of extreme doses) that the\u00a0background values are too high in themselves. Such a\u00a0claim, however, logically contradicts the\u00a0detected short SW. Therefore, in our opinion, another explanation is also possible, namely that the\u00a0limited surface of the\u00a0artificially channelized stream no longer has any additional capacity for P retention, and therefore the\u00a0induction is not accompanied by the\u00a0expected increase in retention. The\u00a0last speculative cause of atypical values may be the\u00a0apparent discrepancy in the\u00a0ratio between phosphorus and chlorides in the\u00a0so-called tailing of the\u00a0concentration wave (Fig.\u00a04 below), when the\u00a0ratio P : Cl at the\u00a0times of the\u00a0last two samples (16:10 and 16:20) significantly increases. This increase apparently corresponds to a\u00a0much slower stabilization of phosphorus concentration compared to the\u00a0rapid return of chloride concentrations to background values. We call this possibility speculative because we have not yet gained enough experience with TASCC method to consider it reliably adopted.<\/p>\n Measurement of P retention by TASCC method only simulates conditions of balanced and low flow, which in our case is a\u00a0range of up to about 10\u00a0l\/s. Therefore, its results do not say anything about mutual relations at high flow rates or extreme loads. During torrents, one can theoretically consider a\u00a0negligible proportion of the\u00a0adhesion of erosion particles in the\u00a0biofilm. However, this will be very limited by the\u00a0spatially thin biofilm because the\u00a0section is not saturated with nutrients from municipal pollution, and also by the\u00a0short duration of the\u00a0peaks. Moreover, scouring of the\u00a0biofilm rather than its growth is likely to occur during these short episodes. A\u00a0much higher retention capacity can be assumed in the\u00a0lower, natural section of the\u00a0Lhotsk stream. Not only longer contact time between flowing water and the\u00a0bed, but mainly the\u00a0more developed hyporheal will probably multiply the\u00a0resulting retention. We therefore believe that only further measurements comparing both sections and carried out in different seasons will provide a\u00a0more comprehensive picture of the\u00a0of the\u00a0spiralling metrics, i.e. the\u00a0phosphorus retention in an exclusively agricultural stream.<\/p>\n We consider made-up ground of the\u00a0applied dose to be a\u00a0critical feature of the\u00a0not very widespread TASCC method; without prior measurement it is difficult to estimate the\u00a0desired saturation concentration. On the\u00a0other hand, even a\u00a0simple inorganic salt in a\u00a0small amount is pollution, and this results in the\u00a0size and number limit of the\u00a0measured flows. In any case, compared to methods using radionuclides, TASCC method is completely safe and, unlike methods using concentration plateaus, the\u00a0total consumption of chemical substances is fractional (although it is definitely not negligible if the\u00a0method is eventually expanded). Simplicity, safety, and environment friendliness are therefore the\u00a0main advantages of this method. Only after resolving the\u00a0ambiguities of the\u00a0increase in the\u00a0made-up ground can we proceed to comparison of sections in different hydromorphological conditions, and it will be possible to definitively expand its wider application in the\u00a0conditions of the\u00a0Czech Republic. We\u00a0believe that TASCC method will bring a\u00a0more precise and, above all, directly measured characterization of phosphorus retention in streams for the\u00a0entire country, starting with average conditions, or balanced flows. Retention values determined in this way can significantly refine our budget models and therefore increase their credibility when discussing corrective measures.<\/p>\n This article was written with the\u00a0financial support of the\u00a0Technological Agency of\u00a0the\u00a0Czech Republic project SS02030027 \u201cWater systems and water management in the\u00a0Czech Republic under conditions of climate change\u201d. We would like to thank Ing. Ondej Taufer for valuable advice in the\u00a0interpretation of the\u00a0results of chemical analyses and processing of the\u00a0mathematical apparatus. We also thank the\u00a0staff of our laboratories led by Ing. Lenka Smetanov\u00e1 for their personal commitment, as\u00a0well as two anonymous reviewers who made a\u00a0significant contribution to the\u00a0quality and clarity of the\u00a0article with their critical comments.<\/em><\/p>\n The Czech version of this article was peer-reviewed, the English version was translated from\u00a0the Czech original by Environmental Translation Ltd.<\/p>\n","protected":false},"excerpt":{"rendered":" Eutrophication of watercourses and reservoirs, specifically the enormous phosphorus load on water, has been the biggest problem for water management in the Czech Republic for several decades. Budget models are effective support for rational solution; apart from resources, they must include the river network characterization, i.e. the retention of phosphorus in streams. A direct method for measuring phosphorus retention in watercourses under well-defined conditions, i.e. a method providing generalizable retention parameters, is fundamentally lacking and it could significantly increase the accuracy of the current models. It seems that TASCC method (Tracer Additions for Spiraling Curve Characterization) has such potential. In this article, we describe its first application in the Czech Republic, namely in the experimental basin of the Lhotsk stream (Beneov district). <\/p>\n","protected":false},"author":8,"featured_media":27783,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[87,93],"tags":[3412,453,3410,3411,3381],"coauthors":[410,597],"class_list":["post-27927","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-hydrochemistry-radioecology-microbiology","category-two-articles","tag-headwaters","tag-phosphorus","tag-pollution-budget-models","tag-retention-measurement","tag-tascc"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/27927","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=27927"}],"version-history":[{"count":13,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/27927\/revisions"}],"predecessor-version":[{"id":32924,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/posts\/27927\/revisions\/32924"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media\/27783"}],"wp:attachment":[{"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/media?parent=27927"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/categories?post=27927"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/tags?post=27927"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/www.vtei.cz\/en\/wp-json\/wp\/v2\/coauthors?post=27927"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/a>\nFig.\u00a02. Map of Lhotsk stream showing both studied sections (200 m), where phosphorus retention was also measured by TASCC method (upper straightened section \u201ccanal\u201d), or only arrival time and morphology of the\u00a0riverbed (lower natural section \u201cmeanders\u201d)<\/h6>\n
<\/a>\n<\/a><\/h6>\nFig. 3. Morphological differences of riverbed in the channelized (upper panel) and natural (lower panel) stretch of the Lhotsk stream; the horizontal profile of the water depth and width was measured every 10 m from the beginning (0 m) to the end (200 m) of the studied section, more often in the case of significant changes<\/h6>\n
RESULTS AND DISCUSSION<\/h2>\n
<\/a><\/a><\/a>\nFig. 4. Concentration of substances and conductivity on the closing profile of the straightened section (200 m) recorded in the passing wave (pouring of the mixture at 15:20) and compared to background values (KTK001)<\/h6>\n
<\/a><\/a><\/a><\/h6>\nFig. 5. Dynamic uptake length (SW -add), total areal uptake (Utot), and total uptake velocity (vf-tot) of phosphorus values obtained by TASCC method in the channelized stretch of Lhotsk stream<\/h6>\n
CONCLUSIONS<\/h2>\n
Acknowledgements<\/h3>\n