The organo-mineral coatings of soil aggregates, cracks, and biopores control sorption and macropore-matrix exchange during preferential flow, in particular in the clay-illuvial Bt-horizon of Luvisols. The soil organic matter (SOM) composition has been hypothesized to explain temporal changes in the hydraulic properties of aggregate surfaces. The objective of this research was to find relations between the temporal change in wettability, in terms of droplet infiltration dynamics, and the SOM composition of coated and uncoated aggregate surfaces. We used 20 to 40 mm sized soil aggregates from the Bt2 horizon of a Haplic Luvisol from loess that were (i) coated, (ii) not coated (both intact), and (iii) aggregates from which coatings were removed (cut). The SOM composition of the aggregate surfaces was characterized by infrared spectroscopy in the diffuse reflection mode (DRIFT). A potential wettability index (PWI) was calculated from the ratio of hydrophobic and hydrophilic functional groups in SOM. The water drop penetration times (WDPT) and contact angles (CA) during droplet infiltration experiments were determined on dry and moist aggregate samples of the three types. The decrease in the CA with time was described using the power function (CA(t) = at–b). For dry aggregates, the WDPT values were larger for coated as compared to uncoated regions on the aggregate surfaces, and increased with increasing PWI value (R2 = 0.75). The a parameter was significantly related to the WDPT (R2 = 0.84) and to the PWI (R2 = 0.64). The relations between the b parameter and the WDPT (R2 = 0.61) and the PWI (R2 = 0.53) were also significant. The WDPT values of wet soil aggregates were higher than those of dry aggregates due to high water contents, which limited the droplet infiltration potential. At the wet aggregate surfaces, the WDPT values increased with the PWI of the SOM (R2 = 0.64). In contrast to dry samples, no significant relationships were found between parameters a or b of CA(t) and WDPT or PWI for wet aggregate surfaces. The results suggest that the effect of the SOM composition of coatings on surface wettability decreases with increasing soil moisture. In addition to the dominant impact of SOM, the wettability of aggregate surfaces could be affected by different mineralogical compositions of clay in coatings and interiors of aggregates. Particularly, wettability of coatings could be decreased by illite which was the dominant clay type in coatings. However, the influence of different clay mineral fractions on surface wettability was not due to small number of measurements (2 and 1 samples from coatings and interiors, respectively) quantified.
An application of different mulch materials may lead to changes in soil properties. Our previous study, focused on the impact of various mulches during the 4-year period, showed that the change in some properties can be very rapid (e.g., soil pH), but in other cases such as hydraulic properties, the changes can be gradual. To find out, whether the extension of the mulching period will further affect the studied soil properties, the experiment continued for another 2 years. Differences between values of organic carbon content (Cox), soil physical quality (Sinf), gravitational water (GW) and readily available water (RAW) of soils not covered by any mulch and under various mulches (bark chips; wood chips; wheat straw; Agrotex EKO+ decomposable matting; polypropylene fabric covered bark chips; crushed stone) were much larger than those observed in our previous study. On the other hand, the opposite trend was observed for the water stable aggregates (WSA) index or soil pH. Differences between additionally measured hydraulic conductivities at the pressure head of −2 cm and repellency index (RI) were mostly insignificant. Results indicated that organic mulches can either positively (e.g., increase WSA index and Cox, and decrease GW) or negatively (e.g., decrease Sinf and RAW, and increase RI) affect soil properties.
Study is focused on the numerical modeling of fly-ash transport in three sands, which was experimentally studied in the laboratory. Sands were packed in glass cylinders with diameter of 5.52 cm and height of 18 cm. Sands were also packed in plastic cylinders with diameter of 30 cm and height of 40 cm. The fly-ash and pulse infiltrations were applied on the top of all cylinders. Visually observed and gravimetrically evaluated fly-ash migration in small cylinders corresponded to fly-ash mobility in large columns detected using the SM400 Kappameter. The HYDRUS-1D code was used to simulate observed fly-ash transport. Parameters of soil hydraulic functions were either obtained using the Tempe cells and the RETC program or estimated using numerical inversion of transient water flow data measured in both types of columns using HYDRUS-1D. Parameters characterizing colloid transport in sands were then estimated from the final fly-ash distribution in sandy columns using attachment/detachment concept in HYDRUS-1D. Fly-ash mobility increased with increasing sand particle sizes, e.g. pore sizes. Particle sizes and pore water velocity influenced the attachment coefficient, which was calculated assuming filtration theory. The same longitudinal dispersivity, sticking efficiency and detachment coefficient sufficiently characterized fly-ash behavior in all sands. and Studie je zaměřena na numerické modelování transportu úletového popílku ve třech píscích, který byl experimentálně studován v laboratoři. Písky byly nahutněny ve skleněných válcích o průměru 5,52 cm a výšce 18 cm. Písky byly také nahutněny v plastových válcích o průměru 30 cm a výšce 40 cm. Na povrchu válců byly aplikovány jednorázové infiltrace vody s popílkem. Migrace úletového popílku pozorovaná vizuálně a zjištěná gravimetricky v malých válcích odpovídala mobilitě úletového popílku detekované Kappametrem SM400 ve velkých válcích. Pozorovaný transport úletového popílku byl simulován programem HYDRUS-1D. Parametry hydraulických funkcí byly získány buď pomocí Tempských cel a programu RETC nebo odhadovány numerickou inverzí transientních data měřených na obou typech válců programem HYDRUS-1D. Parametry charakterizující transport koloidů v píscích byly potom odhadovány z konečné distribuce úletového popílku v písčitých sloupcích užitím konceptu attachment/detachment (připojení/odpojení) v programu HYDRUS-1D. Mobilita úletového popílku se zvyšovala se zvyšující se velikostí písčitých zrn, tj. s velikostí pórů. Velikost zrn a pórová rychlost ovlivnila depoziční (attachment) koeficient, který byl počítán na základě filtrační teorie. Stejné hodnoty podélné disperze, efektivity blokování (sticking efficiency) a mobilizačního (detachement) koeficientu charakterizovaly chování úletového popílku ve všech píscích.
Knowledge of the distribution of plant roots in a soil profile (i.e. root density) is needed when simulating root water uptake from soil. Therefore, this study focused on evaluating barley and wheat root densities in a sand-vermiculite substrate. Barley and wheat were planted in a flat laboratory box under greenhouse conditions. The box was always divided into two parts, where a single plant row and rows cross section (respectively) was simulated. Roots were excavated at the end of the experiment and root densities were assessed using root zone image processing and by weighing. For this purpose, the entire area (width of 40 and height of 50 cm) of each scenario was divided into 80 segments (area of 5x5 cm). Root density in each segment was expressed as a root percentage of the entire root cluster. Vertical root distributions (i.e. root density with respect to depth) were also calculated as a sum of root densities in each 5 cm layer. Resulting vertical root densities, measured evaporation from the water table (used as the potential root water uptake), and the Feddes stress response function model were used for simulating substrate water regime and actual root water uptake for all scenarios using HYDRUS-1D. All scenarios were also simulated using HYDRUS-2D. One scenario (areal root density of barley sown in a single row, obtained using image analysis) is presented in this paper (because most scenarios showed root water uptakes similar to results of 1D scenarios). The application of two root detecting techniques resulted in noticeably different root density distributions. Differences were mainly attributed to the fact that fine roots of high density (located mostly at the deeper part of the box) had lower weights in comparison to the weight of few large roots (at the box top). Thus, at the deeper part, higher root density (with respect to the entire root zone) was obtained using the image analysis in comparison to that from the gravimetric analysis. Conversely, lower root density was obtained using the image analysis at the upper part in comparison to that from the gravimetric analysis. On the other hand, fine roots overlapped each other and therefore were not visible in the image, which resulted in lower root density values from image analysis. Root water uptakes simulated with HYDRUS-1D using diverse root densities obtained for each cereal declined differently from the potential root water uptake values depending on water scarcity at depths of higher root density. and Usually, an earlier downtrend associated with gradual root water uptake decreases and vice versa. Similar root water uptakes were simulated for the presented scenario using the HYDRUS1D and HYDRUS-2D models. The impact of the horizontal root density distribution on root water uptake was, in this case, less important than the impact of the vertical root distribution resulting from different techniques and sowing scenarios.
The aim of this study was to assess the impact of different vegetation on the distribution of rainfall (due to throughfall and stemflow), water regime, and Al and SO4 2- leaching from forest soils. The water flow and Al and SO4 2- transport were modeled using HYDRUS-1D. The study was performed at two elevation transects on the Paličník and Smědava Mountain in Jizera mountains. Podzols and Cambisols were prevailing soil units in this area. It was shown that the effect of the precipitation redistribution on water regime was considerable in the beech forest, while it was almost negligible in the spruce forest. Redistribution of precipitation under trees caused runoff (in one case), increased water discharge through the soil profile bottom, reduction of water storage in the soil, and thus reduction of root water uptake. Simulated Al leaching from the soil profile was determined mainly by the initial Al content in the soil profile bottom. Leaching of SO4 2- was mainly determined by its initial content in the soil and to a lesser extent by redistributed precipitation and SO4 2- deposition.
The goal of this study was to evaluate the effect of products from a municipal wastewater treatment plant on the H2O and CO2 effluxes from two soils. The net H2O and CO2 effluxes were measured at the surface of nine beds with two different soils (Cambisol and Arenosol) and two crops (maize or vegetables). Soils in some beds were amended with stabilized sewage sludge (bed with Cambisol and maize) or composted sewage sludge (two beds with Cambisol and both crops) or were irrigated with treated wastewater (two beds with Cambisol and both crops, and one bed with Arenosol and vegetable). Remaining beds were irrigated with tap water (two beds with Cambisol and both crops, and one bed with Arenosol and vegetable). While stabilized and composted sewage sludge positively affected the CO2 emission, the effect of treated wastewater was not confirmed. Different treatments had negligible effect on the water efflux, which was mainly affected by the plant canopy that influence the temperature of the soil surface. Statistical analyses showed that trends of the CO2 efflux with respect to various scenarios measured on different days changed during the season. No significant correlations were found between the average H2O and CO2 effluxes and measured soil properties.
Treated water from wastewater treatment plants that is increasingly used for irrigation may contain pharmaceuticals and, thus, contaminate soils. Therefore, this study focused on the impact of soil conditions on the root uptake of selected pharmaceuticals and their transformation in a chosen soil–plant system. Green pea plants were planted in 3 soils. Plants were initially irrigated with tap water. Next, they were irrigated for 20 days with a solution of either atenolol (ATE), sulfamethoxazole (SUL), carbamazepine (CAR), or all of these three compounds. The concentrations of pharmaceuticals and their metabolites [atenolol acid (AAC), N1-acetyl sulfamethoxazole (N1AS), N4-acetyl sulfamethoxazole (N4AS), carbamazepine 10,11-epoxide (EPC), 10,11-dihydrocarbamazepine (DHC), trans-10,11- dihydro-10,11-dihydroxy carbamazepine (RTC), and oxcarbazepine (OXC)] in soils and plant tissues were evaluated after harvest. The study confirmed high (CAR), moderate (ATE, AAC, SUL), and minor (N4AC) root uptake of the studied compounds by the green pea plants, nonrestricted transfer of the CAR species into the different plant tissues, and a very high efficiency in metabolizing CAR in the stems and leaves. The results showed neither a synergic nor competitive influence of the application of all compounds in the solution on their uptake by plants. The statistical analysis proved the negative relationships between the CAR sorption coefficients and the concentrations of CAR, EPC, and OXC in the roots (R = –0.916, –0.932, and –0.925, respectively) and stems (R = –0.837, –0.844, and –0.847, respectively).