Search

The accumulation of six pharmaceuticals of different therapeutic uses has been thoroughly investigated and compared between onion, spinach, and radish plants grown in six soil types. While neutral molecules (e.g., carbamazepine (CAR) and some of its metabolites) were efficiently accumulated and easily translocated to the plant leaves (onion > radish > spinach), the same for ionic (both anionic and cationic) molecules seems to be minor to moderate. The maximum accumulation of CAR crosses 38,000 (onion), 42,000 (radish), and 7000 (spinach) ng g−1 (dry weight) respectively, in which the most majority of them happened within the plant leaves. Among the metabolites, the accumulation of carbamazepine 10,11-epoxide (EPC — a primary CAR metabolite) was approximately 19,000 (onion), 7000 (radish), and 6000 (spinach) ng g−1 (dry weight) respectively. This trend was considerably similar even when all these pharmaceuticals applied together. The accumulation of most other molecules (e.g., citalopram, clindamycin, clindamycin sulfoxide, fexofenadine, irbesartan, and sulfamethoxazole) was restricted to plant roots, except for certain cases (e.g., clindamycin and clindamycin sulfoxide in onion leaves). Our results clearly demonstrated the potential role of this accumulation process on the entrance of pharmaceuticals/metabolites into the food chain, which eventually becomes a threat to associated living biota.

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 (S inf), 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 S inf and RAW, and increase RI) affect soil properties.

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.

Agricultural hillslopes present particular challenges for estimating vadose zone dynamics due to a variety of processes, such as surface runoff, vertical flow, erosion, subsurface preferential flow affected by soil structure and layering, non-linear chemical behaviour, evapotranspiration, etc. To investigate these processes and complexity, the SUPREHILL critical zone observatory (CZO) was started in 2020, at vineyard hillslope site in Croatia. The observatory is extensively equipped for the soil-water regime and agrochemical fluxes monitoring, and includes an extensive sensor network, lysimeters (weighing and passive wick), suction probes, surface and subsurface flow and precipitation collection instruments. The main objective of the SUPREHILL observatory is to quantify subsurface lateral and local scale preferential flow processes. Local-scale nonlinear processes in eroded agricultural hillslope sites have large significance on water and solute behaviour within the critical zone and thus need to be researched in depth using combined methods and various approaches. First results from the sensor and lysimeter network, soil-water regime monitoring, isotope analysis, and agrochemical concentrations in 2021 supported the hypothesis of the observatory, that the subsurface flow plays a relevant part in the hillslope soil-water dynamics. In the wick lysimeter network, although the highest cumulative outflow values were found at the hilltop, the highest individual measurements were found at the footslope. During high-intensity rainfall events, there were differences in weighing lysimeters, possibly related to subsurface lateral flow. Based on the isotope analysis, wick lysimeters exhibit a greater variation of d-excess values than suction probes. Agrochemical fluxes confirmed the sloping effect on their transport in soil and demonstrated the favourability of Cu transport by subsurface flow. Using the comprehensive database presented herein, future analyses of this hypothesis will be carried out in more detail using model-based analyses.

The sorption of organic contaminants in soils and sediment is a crucial factor affecting their mobility in the vadose zone environment. The Freundlich sorption isotherms were evaluated for eleven micropollutants and eight soils. The highest Freundlich sorption coefficients, K

Soil hydraulic conductivities of topsoils were studied at 5 points of the hillslope transects delineated at 4 geomorphologically diverse areas, where the original soil types (Chernozem, Luvisol and two Cambisols) were due to erosion transformed into different soil unites. Hydraulic conductivities of saturated soils and for a pressure head of –2 cm were measured directly in the field using a Guelph permeameter (K s,GP ) and mini disk tension infiltrometer (K h=– 2 ,MDI ), and in the laboratory using a multistep outflow method (K s,MSO , K h= – 2 ,MSO ). While K s,GP ≈ K s,MSO in the Chernozem and Cambisol (sandy loam) regions, and K s,GP < K s,MSO in the Luvisol and Cambisol (loam) regions. The K s values obtained using different methods showed different trends along the hillslope transects. The K h= – 2 values obtained using different methods showed similar trends along the transects in the Chernozem and Luvisol regions. These trends could be explained by the position within the transects (i.e., different stages of erosion/accumulation processes). No relationships were found between the K h=– 2 values in the Cambisol regions. The pressure head at an inflection point of the a soil-water retention curve was the main parameter, which appeared to associate (negative correlation) with K h=– 2 and K s,MSO in the Chernozem and Luvisol regions.

The aim of the study was to describe the impact of the soil water content and sulfamethoxazole, SUL, (antibiotic) concentration in soil on the net CO2 efflux. Soil samples were taken from topsoils of a Haplic Fluvisol and Haplic Chernozem. Soil samples were packed into the steel cylinders. The net CO2 efflux was measured from these soil columns after application of fresh water or SUL solution at different soil water contents. The experiments were carried out in dark at 20°C. The trends in the net CO2 efflux varied for different treatments. While initially high values for water treatment exponentially decreased in time, values for solution treatment increased during the first 250–650 minutes and then decreased. The total net CO2 effluxes measured for 20 hours related to the soil water content followed the second order polynomial functions. The maximal values were measured for the soil water content of 0.15 cm3 cm−3 (Haplic Fluvisol with water or solution, Haplic Chernozem with solution) and 0.11 cm3 cm−3 (Haplic Chernozem with water). The ratios between values measured for solution and water at the same soil water contents exponentially increased with increasing SUL concentration in soils. This proved the increasing stimulative influence of SUL on soil microbial activity.

Colluvisols represent an important part of the soil cover, occupying concave slope elements especially in landscapes with undulating relief. Their development reacts to changes in land use or climate, manifested by intense erosion activity or longer resting periods with predominantly in-situ pedogenesis. In climatically, pedologically and historically different regions, diverse colluvial profiles can be encountered. In this study, we investigated deep colluvial profiles in three agricultural plots in Czechia with different soil cover, climatic and geological conditions in order to identify differences in the depositional pattern and erosion history of the areas. In each of the plots, two profiles (depths ranging from 200 to 400 cm) were opened in the toe-slope and side valley areas. Individual layers were investigated by various methods, including optically stimulated luminescence dating, 137Cs activity, concentration of vertically stable geochemical tracers (organochlorine pesticides, nutrients) or micromorphology and clay mineralogy, allowing the layers to be linked to periods of human activity. In all study areas, a significant difference in the colluvial deposition mechanism was found in the toe-slope and side valley areas. While the positions in the side valleys were mainly composed of older material with a minimum concentration of human-bound substances, the profiles in the toe-slopes are characterized by a significant deposition of recently accumulated material. The most pronounced redistribution of material was recorded in the Chernozem area on loess. In the toe-slope area, maxima of 137Cs, DDT (up to 350 µg/kg) and phosphorus were found at 100-140 cm, indicating the very low age of this layer (from the mid-20th century). The mineralogical and chemical composition of this layer and the layer below (140-220 cm) shows considerable similarities to the substrate material, indicating severe truncation of the source soils and accumulation of ploughed parent material. In contrast, in the side valley, this new material was found only in the topsoil, with approximately 3 m of older, humus-rich material beneath. This area is therefore not an area of recent deposition, but rather of material transport. The original buried Chernozem was found in both cases at a depth of about 300-350 cm. In the Cambisol area, the combination of rill and sheet erosion led to the formation of a highly stratified profile with a large variation in texture or humus content. The maximum of human-bound substances (137Cs, HCB, DDT) was found at a depth of 1 m, underlain by older material with signs of post-depositional pedogenesis (weathering and redox processes). The area of side valley was, as in the previous area, almost unaffected by recent sedimentation. In Luvisol area, the concentration on human-bound substances was generally lower and affected only the upper, humus-rich layer (ca 80 cm) of the Colluvisols, both at the toe-slope and the side valley. Below this layer, the profiles are characterised by relatively pronounced pedogenesis in the sedimentary material (clay coatings visible at the thin sections), indicating slower sedimentation and a longer period of sedimentary quiescence.Study was supported by grant nr. 21-11879S of the Czech science foundation and MEYS CR project nr. CZ.02.1.01/0.0/0.0/16_019/0000845.

Soil vadose zone is one of the most complex terrestrial systems due to various processes occurring within its boundaries. The first Croatian critical zone observatory SUPREHILL was established to specify subsurface preferential flow and nonlinear agrochemical transport processes. Combining laboratory and numerical methods with extensive sensor-based equipment will result in a wide range of data allowing us to accurately estimate heterogeneities on a local scale. The presented study includes estimation of soil hydraulic properties (SHP) and water flow experiments under controlled conditions. Undisturbed soil cores (250 cm3) were taken in three repetitions at the top, middle and the bottom of the hillslope to estimate SHP using the HYPROP and WP4C techniques. Undisturbed soil columns were taken at the hilltop, middle, and the bottom of the vineyard hillslope from the row and interrow area. Soil columns are 25 cm high and 16 cm in diameter with soil moisture sensors and tensiometers set inside each column. Each soil column was irrigated three times per day during two-week period. Results obtained using HYPROP showed very similar SHP in the investigated depth which indicates uniform soil structure along the hillslope (top soil layer). HYPROP derived SHP showed very low values of hydraulic conductivity, but the sensors in columns reacted shortly after irrigation which indicates higher hydraulic conductivity. Since soil cores for HYPROP are relatively small compared to the soil columns, the presence of preferential flow is minimal, and some flow pathways present on the larger scale are not accounted for. Therefore, preferential flow will be further identified and quantified using a dye tracer, and experimental results will be shown. For additional preferential flow identification and quantification, later in the research, we will combine CT-scanning of undisturbed soil columns and numerical simulations.

Soil degradation due to water erosion is one of the greatest problems of agricultural soils worldwide. To be able to map the extent of soil degradation and consequently propose actions for soil improvement, an effective approach is needed. Soil organic carbon (SOC) content and its time fluctuations is one of the key features characterizing the given site and occurring processes. It is widely accepted as the main soil quality indicator and therefore can be used for soil degradation assessment. Traditional laboratory techniques (dry combustion, wet oxidization) of soil organic carbon determination are usually labor intensive and time consuming, which means they are not suitable for large sample collections (e.g., large areas or continual monitoring). Therefore, there is a need for fast, reliable, and cost-effective techniques. Our previous study documented that the VIS-NIR reflectance spectroscopy and magnetic susceptibility can be a very efficient tool for SOC mapping with the Chernozem (a loess region of South Moravia, Czech Republic) areas heavily affected by water erosion. Within this area colluvial soils with up to an about 4 m deep humus enriched horizon were developed. Distribution of soil properties within the colluvial soil profiles at several positions were evaluated using standard and novel methods to distinguishing the different sedimentation phases and understanding colluvial soil formation. The same study was also performed in another two locations (Cambisol and Luvisol areas). Results showed that while both methods could be used for estimation of SOC distribution within the soil profiles in the Chernozem area, in the other two areas the VIS-NIR reflectance spectroscopy method was less accurate and magnetic susceptibility was inaccurate because there was no correlation between SOC and content of ferrimagnetic particles. Acknowledgement: Study was supported by the Czech Science Foundation, project "Pedogenesis of colluvial soils: a multidisciplinary approach in modeling the dynamics of development in the soil-landscape environment" (No. 21-11879S) and also by the European Structural and Investment Funds, projects NutRisk (No. CZ.02.1.01/0.0/0.0/16_019/0000845).

Various micropollutants (including pharmaceuticals, UV filters, cosmetics, cleansers, etc.), are increasingly being detected in the environment because of their partial or incomplete removal from wastewater in wastewater treatment plants (WWTPs). These compounds can be taken up by plants if treated wastewater is used for irrigation or if biosolids are used for soil amendment. Previous studies focused on this subject were usually performed under greenhouse conditions. Therefore, the aim of this study was to evaluate a behavior of studied compounds under natural climatic conditions. Experiment was carried out directly in the wastewater treatment plant, where nine raised beds were installed, which contained soils taken from topsoil of two soil types Arenosol (two beds) and Cambisol (seven beds). Either maize or a mixture of different vegetables (lettuce, carrot and onion) was grown in these beds. Of the seven beds with the Cambisol, one of the beds containing either maize or vegetables was irrigated with tap water and other pair of beds (maize or vegetables) was irrigated with treated wastewater (i.e., WWTP effluent). In another pair of beds (maize or vegetables), composted sludge from WWTP Three beds containing both types of biosolids were irrigated with tap water. Only vegetables were grown in the beds with the Arenosol, which were irrigated with either tap water or treated wastewater. Climatic data, irrigation doses, drainage water volumes, soil water contents and plant growth were monitored during the experiment. Selected compounds concentrations were measured in WWTP effluent, both biosolids, drainage water, soils, and plant tissues. Fifty five of 77 analyzed compounds were quantified in WWTP effluent. Main compounds were pharmaceuticals (e.g., telmisartan, gabapentin, diclofenac, carbamazepine, and its metabolites), UV filters (e.g., phenylbenzimidazole sulfonic acid) and compounds used in anticorrosive paints (e.g., 1H-benzotriazole). In the case of both biosolids, the dominant compounds were telmisartan, sertraline, trazodone, citalopram, diclofenac (i.e., pharmaceuticals) and 1H-benzotriazole. Uptake of different compounds by plants depended on a plant and properties of organic molecules, which affected their sorption in soils and mainly their ability to be taken up and translocated in plants. For instance, pharmaceuticals carbamazepine, gabapentin tramadol and venlafaxine were mainly found in lettuce leaves. Acknowledgement: Study was supported by the Ministry of Agriculture of the Czech Republic, project "The fate of selected micropollutants, which occur in treated water and sludge from wastewater treatment plants, in soil" (No. QK21020080) and partly also by the European Structural and Investment Funds, projects NutRisk (No. CZ.02.1.01/0.0/0.0/16_019/0000845).

Different land uses significantly affect the soil water and temperature regimes. Very different modifications of the soil surface are found especially in the urban environment, where different materials, which are used in gardening and civil engineering, are used to cover soil surface. Alternations of these regimes due to modifications of soil covers may lead to changes in soil properties. Therefore, the goal of this study was to find out how soil properties, particularly soil structure and soil hydraulic properties changed during our experiment, which has been mainly focused on the monitoring of soil water and thermal regimes under five different surface covers (bare soil, bark chips, concrete, mown grass, and unmown grass). The surface of a Haplic Chernozem (which was originally coverd by grass) was modified in the autumn 2012. Since then, climatic conditions are monitored, and soil water contents and temperatures are measured at the depths of 10, 20, 30, 40, 60, and 80 cm. In the summer 2020, after removal of the surface over, intact soil samples were taken, on which the hydraulic properties were measured using the multistep outflow method. Another set of the undisturbed soil samples was used to study soil structure using the X-Ray computer tomography. In addition, these samples were next used to prepare thin soil slides for micromorphological analyses. Along with soil sampling, the measurement of some characteristics took place directly in the field. The mini disk tension infiltrometer with a disk radius of 2.22 cm was used to measure unsaturated hydraulic conductivities for pressure head of –2 cm. The net CO2 and net H2O efflux were measured using the LCi-SD portable photosynthesis system with a Soil Respiration Chamber. The CT and micromorphological analyzes showed that while the soil under the bare surface showed small aggregates and small interaggregate pores, the soil under the grass cover was formed by large aggregates with large pores formed by roots and organisms living in soils. Soil structure under concrete or bark chips was compact with thin fractures and few pores created by organisms living in soils. However, porosity under bark chips was larger than that under concrete likely due to better conditions, i.e., larger amount of the organic matter content due to the decomposition of organic mulch. Measured soil properties reflected character of soil structure.Acknowledgement: Study was supported by the European Structural and Investment Funds, projects NutRisk (No. CZ.02.1.01/0.0/0.0/16_019/0000845).

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).

The objective of this study was to elucidate the influence of long-term ecological farming on selected soil properties by comparing results obtained in the field with continuous conventional farming (CT) and those obtained in the field where the original CT was converted into ecological farming system with no-till practice (NT) twelve years earlier. Soil water retention curves were obtained for 100 cm3 undisturbed soil samples using a pressure plate apparatus. Hydraulic conductivity and the repellency index were assessed directly in the field using a mini disk infiltrometer. The examined soil properties showed that NT mostly had a positive influence on the soil quality. The soil water retention capacity represented by the saturated soil water content of 0.32 and 0.40 cm3 cm−3 and the reciprocal of the air-entry pressure head of 0.0227 and 0.0187 cm for CT and NT, respectively, was higher in the NT field than in the CT field. The soil physical quality, represented by the slope of the soil water retention curve at the inflection point of 0.033 (CT) and 0.047 (NT), was better under NT than CT. The hydraulic conductivity at the pressure head of –2 cm was higher in the NT field (0.97 cm hr.−1) than in the CT field (0.17 cm hr.−1). On the other hand, ecological farming increased water repellency (repellency index of 6.73 and 18.91 for CT and NT, respectively).

Pharmaceutical and illicit drug residues in sewage sludge may present important risks following direct application to agricultural soils, potentially resulting in uptake by plants. Leaching/desorption tests were performed on different types of stabilized sewage sludge originating from multiple treatment technologies in the Slovak Republic. Acid rain and base-rich condition of soil with different pH conditions were simulated to model the effect of widely varying pH (pH 2, 4, 7, 9, and 12) on the leaching/desorption of pharmaceuticals and illicit drugs. Twenty-nine of 93 target analytes were found above the limit of quantification in sludge or associated leachates. Total desorbed amounts of pharmaceuticals and illicit drugs ranged from 810 to 4000 µg/kg, and 110 to 3600 µg/kg of the dry mass of anaerobic and aerobic sludge, respectively. Desorbed fractions were calculated as these values are normalized to initial sludge concentration and, therefore, were more suitable for qualitative description of the behavior of individual compounds. Using principal component analysis, qualitative analysis of the desorbed fraction confirmed the differences among sludge types, pharmaceuticals, and desorption pH. Desorbed fractions could not be related to the octanol/water distribution coefficient. Desorbed fractions also did not reflect the expected ionization of studied molecules unless converted into their relative values. Generally, the lowest mobility was observed within the environmentally relevant pH range of 4-9, and high pH generally resulted in high desorption, especially in anaerobically stabilized sludges.

Food contamination is a major worldwide risk for human health. Dynamic plant uptake of pollutants from contaminated environments is the preferred pathway into the human and animal food chain. Mechanistic models represent a fundamental tool for risk assessment and the development of mitigation strategies. However, difficulty in obtaining comprehensive observations in the soil-plant continuum hinders their calibration, undermining their generalizability and raising doubts about their widespread applicability. To address these issues, a Bayesian probabilistic framework is used, for the first time, to calibrate and assess the predictive uncertainty of a mechanistic soil-plant model against comprehensive observations from an experiment on the translocation of carbamazepine in green pea plants. Results demonstrate that the model can reproduce the dynamics of water flow and solute reactive transport in the soil-plant domain accurately and with limited uncertainty. The role of different physicochemical processes in bioaccumulation of carbamazepine in fruits is investigated through Global Sensitivity Analysis, which shows how soil hydraulic properties and soil solute sorption regulate transpiration streams and bioavailability of carbamazepine. Overall, the analysis demonstrates the usefulness of mechanistic models and proposes a comprehensive numerical framework for their assessment and use.

The appearance and distribution of soil pores have a significant influence on water flow and solute transport in the soil vadose zone and are easily affected by tillage, trafficking, crop rotation, and various management practices in arable areas. Pore geometry in the soil is highly variable, especially in agricultural soils due to various management. Such heterogeneity can have a considerable influence on water and solute transport within the soil vadose zone. The aim of this study was to assess preferential flow pathways in agricultural soil. To quantify structure, undisturbed soil columns were taken on which outflow experiments using water and Brilliant Blue tracer were applied. Soil hydraulic parameters (SHP) were estimated on undisturbed soil cores (250 cm3) using the simplified evaporation method and the HYPROP automatized system. HYDRUS-1D numerical modeling was performed using single and dual-permeability models. In the latter, the Richards equation is applied separately to two overlapping pore regions – the macropore and matrix domains. A dual-permeability model is used because the extensive macropore network was revealed and due to its ability to differentiate flows in soil macropore and matrix regions. The use of the dual-permeability model resulted in a faster response of outflow to irrigation and higher outflow rate peaks. Dye distribution was uneven because of enhanced dye penetration along biopores and in regions with a higher fraction of larger interaggregate pores formed in the root zone. Simplified single porosity model could not reproduce deeper staining patterns (e.g., below 15 cm depth). Modeling of the transport of Brilliant Blue dye revealed the necessity of using dual-region transport models to capture non-equilibrium flow patterns in agricultural soils with complex pore systems.

Soil pollution from emerging contaminants poses a significant threat to water resources management and food production. The development of numerical models to describe the reactive transport of chemicals in both soil and plant is of paramount importance to elaborate mitigation strategies. To this aim, in the present study, a multiscale biophysical model is developed to predict the fate of ionizable compound in the soil-plant continuum. The modeling framework connects a multi-organelles model to describe processes at the cell level with a semi-mechanistic soil-plant model, which includes the widely used Richards-based solver, HYDRUS. A Bayesian probabilistic framework is used to calibrate and assess the capability of the model in reproducing the observations from an experiment on the translocation of five pharmaceuticals in green pea plants. Results show satisfactory fitting performance and limited predictive uncertainty. The subsequent validation with the cell model indicates that the estimated soil-plant parameters preserve a physically realistic meaning, and their calibrated values are comparable with the existing literature values, thus confirming the overall reliability of the analysis. Model results further suggest that pH conditions in both soil and xylem play a crucial role in the uptake and translocation of ionizable compounds.

An adequate hydrological description of water flow in permeable pavement systems relies heavily on the knowledge of the unsaturated hydraulic properties of the construction materials. Although several modeling tools and many laboratory methods already exist in the literature to determine the hydraulic properties of soils, the importance of an accurate materials hydraulic description of the permeable pavement system, is increasingly recognized in the fields of urban hydrology. Thus, the aim of this study is to propose techniques/procedures on how to interpret water flow through the construction system using the HYDRUS model. The overall analysis includes experimental and mathematical procedures for model calibration and validation to assess the suitability of the HYDRUS-2D model to interpret the hydraulic behaviour of a lab-scale permeable pavement system. The system consists of three porous materials: a wear layer of porous concrete blocks, a bedding layers of fine gravel, and a sub-base layer of coarse gravel. The water regime in this system, i.e. outflow at the bottom and water contents in the middle of the bedding layer, was monitored during ten irrigation events of various durations and intensities. The hydraulic properties of porous concrete blocks and fine gravel described by the van Genuchten functions were measured using the clay tank and the multistep outflow experiments, respectively. Coarse gravel properties were set at literature values. In addition, some of the parameters (Ks of the concrete blocks layer, and α, n and Ks of the bedding layer) were optimized with the HYDRUS-2D model from water fluxes and soil water contents measured during irrigation events. The measured and modeled hydrographs were compared using the Nash-Sutcliffe efficiency (NSE) index (varied between 0.95 and 0.99) while the coefficient of determination R2 was used to assess the measured water content versus the modelled water content in the bedding layer ( R 2 = 0.81 ÷ 0.87 ) . The parameters were validated using the remaining sets of measurements resulting in NSE values greater than 0.90 ( 0.91 ÷ 0.99 ) and R2 between 0.63 and 0.91. Results have confirmed the applicability of HYDRUS-2D to describe correctly the hydraulic behaviour of the lab-scale system.

As soil oxidizable carbon (C ox ) has several different absorptions in the visible– and near infrared (vis–NIR) region due to its complex composition, multivariate calibration techniques such as multiple linear regression (MLR), partial least squares regression (PLSR), support vector machines (SVM) or random forest (RF) can be advantageously used to obtain a good prediction. Besides that, the content of C ox is often affected by the character of the terrain, mainly due to prevailing water regime with associated transport and sedimentation processes. Therefore, the question arises; if predictive models calibrated by combining vis–NIR diffuse reflectance spectroscopy (vis–NIR DRS, 350–2500 nm) and the digital elevation model (DEM) derivatives will provide a more accurate estimate of C ox . Focused on a sloping arable land (100 ha) affected by distinct water erosion, we tested for this purpose two conceptually different predictive approaches that differ in the nature of the spectroscopic predictor variables. In Approach A that relied on absorption feature (AF) parameters, the inclusion of DEM derivatives resulted in improved C ox prediction using all the tested calibration techniques, i.e. MLR, RF, PLSR and SVM. The MLR prediction that was the most accurate among all others improved from R 2 cv = 0.81 (vis–NIR DRS dataset) or 0.50 (DEM derivatives dataset) to 0.84 (combination of both). For that prediction especially AF centered at 500, 700, 900, 1800, 1900, 2200 and 2400 nm, as well as elevation, LS factor and plan curvature were important. In contrast, in the Approach B that relied on reflectance (RF and PLSR) or normalized reflectance (SVM) values at each wavelength, no positive effect of inclusion of DEM derivatives was observed.

As there is no single (or combination of) signal pre-processing method that works best with all data sets, choosing the most feasible one is a key aspect in soil diffuse reflectance spectroscopy in the visible– and near infrared region (400–2500 nm). The commonly used pre-processing methods include tools for spectra smoothing and/or noise reduction (e.g. Savitzky-Golay (SG) filtering or discrete wavelet transformation (DWT)), light scatter correction (multiplicative scatter correction (MSC), standard normal variate (SNV)), baseline normalization techniques to cope with vertical offset and/or slope effects (e.g. continuum removal (CR), first and second order derivative (FD and SD)), as well as other transformations (e.g. logarithmic-log(1/R)). All of these tools are aimed at eliminating or reducing unwanted side effects (artifacts) in the spectra and at enhancing the recognition of relevant information. For soil organic carbon content estimation using partial least square regression calibration technique, smoothing with SG filter and (or in combination with) CR usually ensures a reliable estimation. However, the common CR may suffer from a few shortcomings. An approximation is applied to connect the pivot points of the spectrum in order to derive a continuum, but more problematically, the CR procedure does not recognize the true essence of the vertical shift at the very beginning of the spectra (the CR value always equals one at that point). Therefore, we decided to modify the procedure in the way that the reflectance values at respective wavelengths were divided not by the continuum, but by the maximal reflectance value of the particular spectrum. This correction by the maximum reflectance (CMR) pre-processing was tested in comparison with eight other above mentioned methods at four different study sites that differ in the prevailing soil units. As a result, on site 1 (Haplic Chernozem), we achieved a significantly improved prediction accuracy using the CMR (R2cv = 0.845) compared to raw (but smoothed) soil spectra (0.815). On site 2 (Rendzic Leptosol), the most accurate prediction was achieved equally with CMR, MSC, SNV, log(1/R), DWT and raw spectra (R2cv from 0.560 to 0.592), and on site 3 (Haplic Cambisol) equally with MSC and CMR (both R2cv = 0.767), as only these two were significantly different from the raw spectra. On site 4 (Haplic Luvisol), the only one significantly more accurate prediction compared to raw spectra was achieved with FD (R2cv = 0.611), while for the rest of the methods, except SD, there was no difference if either raw spectra or other transformations were used (R2cv from 0.499 to 0.591). Finally, using the whole data set the differences between pre-processing methods were even less pronounced, when there was no significant difference between raw spectra and other methods (except SD which was significantly worse), although all the predictions were more accurate in general (R2cv from 0.811 to 0.831).

Soil pollution from neutral and ionizable compounds poses a significant threat to water resources management and food production. The development of numerical models to describe their reactive transport in the soil-plant domain is of paramount importance to elaborate mitigation strategies. However, most existing models simplify the description of physicochemical processes in soil and plants, mass transfer processes between soil and plants and in plants, and transformation in plants. To fill this scientific gap, we first coupled the widely used hydrological model, HYDRUS, with a multi-compartment dynamic plant uptake model, which accounts for differentiated multiple metabolization pathways in plant’s tissues. The model, which is able to simulate the reactive transport of neutral compounds, has been successfully validated against experimental data, and integrated in the Graphical User Interface of the HYDRUS software suite. To further extend its domain of applicability, we have recently adapted its theoretical framework to simulate the translocation of ionizable compounds. The new modeling framework connects a biophysical multi-organelles model to describe processes at the cell level with a semi-mechanistic soil-plant model, and accounts for dissociation processes and electrical interactions with cell biomembranes. Validation against experimental data showed encouraging results and opens new perspectives for its use for predictive and explanatory purposes. ReferencesŠimůnek, J., G. Brunetti, and R. Kodešová, Modeling the translocation and transformation of chemicals in the soil-plant continuum: A dynamic plant uptake module for the HYDRUS model, AGU Annual Meeting, ID 810092, New Orleans, Louisiana, December 13-17, 2021.

In structured soils, earthworm burrows, root channels, shrinkage cracks, and interaggregate spaces form complex macropore networks. Depending on the type and morphological properties, each macropore surface type is coated with specific organo-mineral compounds, differently affecting sorption and mass exchange during preferential flow and turnover processes. For a quantitative, macropore type–specific analysis using X-ray computed tomography (XRCT) with subsequent three-dimensional (3D) image analysis, a discrimination of biopores from cracks and interaggregate spaces is necessary. We developed a method that allows separating biopores from other larger macropores in 3D images from XRCT of intact soil cores. An image-processing workflow using the MAVI (Modular Algorithms for Volume Images) software framework ToolIP (Tool for Image Processing) was created to handle XRCT 3D images. Masking steps enabled to retain the surface roughness in the resulting two images of separated biopores and cracks. As a key point, the sizes of the structuring elements used in the spherical opening and dilation were objectively determined. For this purpose, maximum differences in the pore shapes between the 3D images of cylindrical biopores vs. more flat cracks and unregularly interaggregate spaces were focused. At the given resolution of 231-μm voxel edge length, an optimum size of 2.5 voxels was found for both processing steps. The voxel-based approach is applicable to XRCT 3D images of different spatial resolution and appears useful for the quantification of physicochemical surface properties of different macropore types for soil volumes, enabling a more precise description of preferential flow and transport.

Extensive agricultural use of land coupled with intensive water erosion at geomorphologically diverse areas with uniform soil substrate and originally similar soils can lead to high diversity in soil types and, correspondingly, to a high spatial and temporal variability of soil properties (including soil hydraulic properties). Therefore, this study aimed to propose a procedure to characterize the variability of soil hydraulic properties of topsoils and the soil–water regime. Soil hydraulic properties were measured after sowing and harvesting at 5 sampling points of 1 elevation transect at 5 experimental areas with diverse soil types. The reference soil hydraulic properties and 3 scaling factors (related to the pressure head, αh, water content, αθ, and hydraulic conductivity, αK) were used to characterize the spatial and temporal variability of soil hydraulic properties. The best correspondence between scaled soil hydraulic curves was observed for the Chernozem area, followed by the two Haplic Cambisols areas, Leptosol area and Luvisol area. In general, matching of the scaled curves increased with a decreasing variability of n values (i.e., increasing similarity of a soil pore space geometry) and increasing average n values (e.g., for pronounced S-shape soil water retention curves). The sampling day significantly affected αh, αK, and αθ in the Chernozem area; αh and αK in the Cambisol (developed on shale) area; and αh and αθ in the Leptosol area. While values for the Chernozem area indicated an improvement in soil hydrological conditions during the vegetation period, the values for the Luvisol, Leptosol, and Cambisol (developed on shale) areas indicated aggravation. No considerable changes were observed for the Cambisol (developed on granodiorite and shale) areas. The sampling position significantly affected αθ in both the Cambisol areas. At some locations (e.g., Chernozem area), the spatial variability reflected different erosion-accumulation processes within the transect. To illustrate a practical application of the scaling factors at such locations, the scaling factors obtained for the Chernozem area were linearly interpolated within the surface layer of the theoretical vertical two-layer soil transect, and HYDRUS-2D program was used to simulate water flow in the surface 50 cm layer. The results showed a more gradual wetting front after sowing than after harvesting.

A long-term application of various mulch materials may lead to changes in certain soil properties, which mostly remain unreviewed. Therefore, our study focused on the mulch effect on a larger group of Haplic Fluvisol properties. The experiment was performed on 27 perennial patches covered by eight different mulch materials (bark chips, wood chips, wheat straw, cardboard, paper foil, decomposable matting, nonwoven fabric covered by bark chips, and crushed basalt) and control patches without any mulch during the 4 year period. The highest daily ranges of soil temperature were found in control patches without mulch, lower temperature ranges below foils mulches, and the lowest below organic mulches. Mulches preserved water storage in soil mainly during spring before vegetation integration and after perennials’ cutting. Organic carbon content (Cox), aggregate stability, and pH mostly did not show any trends over time, except for Cox and aggregate stability from patches with bark or wood chips and wheat straw. In these cases, decomposed organic matter significantly increased both properties. On the other hand, the soil hydraulic properties (mostly due to no-till practice) considerably changed in all patches. The saturated and residual water contents, saturated hydraulic conductivity, and reciprocal of the air-entry pressure head increased. Correspondingly, the bulk density decreased. Soil water retention curves from the patches with bark or wood chips were more gradual than those from other patches, which indicates higher water retention capacity for lower pressure heads. However, the physical quality of soils under organic mulches expressed by the slope at the retention curve inflection point was lower than that for other scenarios. Readily available water under organic mulches was also lower than that for other setups. This suggests that organic mulches have largest impacts on soil conditions, which can be either favourable or adverse.

The appearance and distribution of soil pores have a significant influence on water flow and solute transport in the soil vadose zone. The pore system is highly variable in arable soils where crop rotation, tillage, trafficking, soil amendments, and various management practices are commonly implemented. The aim of this study was to assess the porous system and preferential flow pathways in a vineyard soil using undisturbed soil columns, and by combining laboratory and numerical methods with dye staining and X-ray imaging. It was hypothesized that the integration of various methods could reveal more information about soil structure, and flow and transport behavior of structured arable soil. Soil water retention and hydraulic conductivity curves were obtained using the evaporation method, while water flow was assessed using intermittent leaching experiments. Water flow and the transport of Brilliant Blue were simulated using HYDRUS-1D. A single-porosity model of soil hydraulic properties provided a good description of data collected during the evaporation experiments. Data collected during leaching experiments did not provide enough experimental evidence for the occurrence of nonequilibrium flow patterns and the differentiation between the single- and dual-permeability models of soil hydraulic properties. However, dye staining and X-ray imaging revealed a complex pore-architecture network with large vertical and horizontal biopores. The staining patterns (Brilliant Blue FCF) within the vertical column sections documented the extent of preferential flow. The study showed that the bi-modal character of pore structure could often be hidden when a limited number or non-adequate methods are applied for its quantification from water flow behavior. The impact of preferential pathways on dye transport can be investigated with observations and simulations. A combination of various methods enabled us to adequately assess vineyard soil structure and fine-tune the description and extent of preferential water flow.