Modelling Water Dynamics, Transport Processes and Biogeochemical Reactions in Soil Vadose Zone

Large numbers of numerical models are nowadays available for the description of physical and chemical processes affecting water flow and solute transport in soil vadose zone. This chapter explains basic principles of water flow and solute transport modelling in soil vadose (variably saturated) zone and some of the most important processes present in it. First part deals with water dynamics in the soil, that is, soil water content, pressure head, soil porosity, and water flow. Also, some of the measurement techniques used to estimate water dynamics in soil are explained. Water retention curve and soil hydraulic properties needed for modelling are briefly discussed with the explanation of basic (i.e. most commonly used) hydraulic relationship in soil (van Genuchten equation) and water flow (Richards equation) approaches. Second part includes solute transport description in vadose zone, including processes such as advection, diffusion, dispersion, and adsorption. Basic advection‐dispersion equation is explained and also the implementation of boundary and initial conditions in the numerical model. Preferential flow is shortly discussed with the basic principles behind its occurrence and modelling in the soil vadose zone. One real case one‐dimensional (1D) example of modelling with HYDRUS software is presented in which water flow and nitrate transport is simulated on the lysimeter study. Short overview of the most widely used numerical models for simulating vadose zone processes is also presented, whereas the final part is focused on chemical speciation modelling in relatively homogeneous soil solutions using visual MINTEQ interface

Prostorno mapiranje kemijskih svojstava tla koristeći multivarijatnu geostatistiku. Studija s oraničnih tala u istočnoj Hrvatskoj

The spatial variability of soil chemical properties is affected by factors of soil formation and human activities. Understanding their spatial variability will improve agricultural production, reduce environmental problems (e.g., soil pollution, offsite effects), and achieve sustainable agroecosystems. The main objective was to study the spatial variability of pH, soil organic matter, available phosphorus, and available potassium using univariate and multivariate methods in cropland fields in eastern Croatia. For the study, 169 (0-30 cm) soil samples were collected in a 911 ha study area. The results showed that soils had slightly acidic pH, adequate available phosphorus and potassium values for crop production, and low soil organic matter concentration. The variability was high in available phosphorus and low in pH. Soil pH, soil organic matter, available phosphorus, and potassium nugget/sill ratio was 0.00, 2.79, 18.68, and 22.08, respectively. Auxiliary variables increased the accuracy of the predictions. Soil organic matter levels were below the recommendable, and this is very likely an anthropogenic effect, even though the intrinsic process influences soil organic matter. The heterogeneous distribution of phosphorus and potassium highlighted the necessity of fertilization in some areas. For the sustainability of agroecosystems, adaptable site-specific soil management strategies need to be implemented.Prostorna varijabilnost kemijskih svojstava tla uvjetovana je pedogenetskim čimbenicima i ljudskom aktivnošću. Razumijevanje prostorne varijabilnosti poboljšati će poljoprivrednu proizvodnju, smanjiti okolišne probleme (npr. zagađenje tla, off-site učinci), i postići održivost agroekosustava. Glavni cilj rada je istraživanje prostorne varijabilnosti pH, organske tvari i biljci pristupačnog fosfora i kalija, koristeći univarijatne i multivarijatne metode na oraničnim tlima u istočnoj Hrvatskoj. Za rad je prikupljeno 169 (0-30 cm) uzoraka tla s površine od 911 ha. Rezultati pokazuju da su tla blago kisela, adekvatnog sadržaja biljci pristupačnog fosfora i kalija za biljnu proizvodnju i niskog sadržaja organske tvari tla. Varijabilnost je visoka kod biljci pristupačnog fosfora i niska kod pH tla. pH tla, organska tvar te biljci pristupačan fosfor i kalij imaju nuget/sill omjer 0.00, 2.79, 18.68, i 22.08. Pomoćni podaci povećali su preciznost predikcije. Identificiran je sadržaj organske tvari tla ispod preporučljive razine i to vrlo vjerojatno radi antropogenog utjecaja, iako i pedogenetska svojstva utječu na organsku tvar tla. Heterogena distribucija fosfora i kalija istaknula je nužnost za gnojidbom u nekim područjima. Za održivost agroekosustava potrebno je provesti prilagodljive strategije korištenja i upravljanja tlima na svakoj pojedinoj lokaciji

Modification of copper and cadmium biovailability to faba bean plant (Vicia Faba L.) as affected by soil organic matter and salinity

Određivanje mobilnosti i biopristupačnosti metala u tlu predstavlja osnovu za procjenu rizika od njihovog potencijalnog uključivanja u hranidbeni lanac. Stoga je cilj rada bio definirati mehanizme kojima organska tvar (OT) i salinitet tla rezultiraju promjenama u mobilnosti i biopristupačnosti bakra (Cu) i kadmija (Cd) u tlu. Pretpostavljeno je da će povećanje OT i zaslanjenosti tla utjecati na mobilnost/biopristupačnost Cu i Cd te mikrobiološku dehidrogenaznu aktivnost (DHA) u tlu. Istraživanje je obuhvatilo 2 pokusa koji su provedeni u kontroliranim uvjetima plastenika na Agronomskom fakultetu u Zagrebu, s bobom (Vicia faba L. cv. Aguadulce) kao test kulturom. Eksperimentalni dizajn pokusa bio je split-split-plot u 3 ponavljanja. Glavni faktor bio je sadržaj OT u 2 razine: tlo uzeto iz područja Donje Neretve (OT1) te isto tlo miješano s tresetom u omjeru 4:1 (OT2). Podfaktor bio je NaCl salinitet u 3 razine (0, 50 i 100 mM), a podpodfaktor kontaminacija tla s 250 i 500 mg kg-1 Cu (pokus 1), odnosno 5 i 10 mg kg-1 Cd (pokus 2) i kontrolna (nekontaminirana) varijanta. Rezultati istraživanja ukazuju da je OT jedna od najznačajnijih pedovarijabli koje utječu na mobilnost/biopristupačnost istraživanih metala u tlu. Dodatak OT u varijanti OT2 smanjio je biopristupačnost Cu u tlu procesima sorpcije i kompleksacije s OT (ukupna koncentracija Cu u tlu povećana je za 5 %, dok je koncentracija Cu u mahuni boba smanjena za 14 %). Rezultati upućuju i na smanjenu biopristupačnost Cu u uvjetima NaCl saliniteta i/ili smanjeno primanje Cu u test kulturu iz zaslanjene rizosfere. Dodatak OT u varijanti OT2 i posljedično povećanje koncentracije DOC-a u otopini tla, smanjuje aktivnost slobodnog Cd2+, a time i njegovo primanje u korijen (koncentracija Cd u listu boba smanjena je za 28 %, u mahuni za 40 % te u sjemenu za 20 %). Primjena NaCl nije rezultirala povećanom biopristupačnošću Cd, nego samo njegovom redistribucijom unutar krute faze tla. Kontaminacija tla Cu i Cd nije utjecala na fotosintetske pokazatelje lista boba, upućujući na zaključak da nije utjecala na produktivnost biljaka boba, iako je indeks sadržaja klorofila (CCI) smanjen za 4 % s Cd10 tretmanom. Dodatak OT u varijanti OT2 povećao je za 30-65 %, a NaCl salinitet smanjio za 28-29 % pri NaCl100 tretmanu dehidrogenaznu aktivnost (DHA) u tlu. Kontaminacija tla Cu smanjila je DHA za 50 % pri Cu500 tretmanu. Kontaminacija tla Cd nije utjecala na DHA, ali modeliranje udjela različitih kemijskih oblika Cd u otopini tla primjenom programa Visual MINTEQ i modela NICA-Donnan upućuje na mogućnost da kompleksi Cd i klorida (CdCln2-n) imaju izraženiji inhibitorni učinak na DHA u tlu.The aim of this research was to study the mechanisms by which soil organic matter (SOM) and increased soil salinity affect copper (Cu) and cadmium (Cd) mobility in soil, as well as the importance of afore mentioned mechanisms for their bioavailability in soil. Therefore, to study the Cu and Cd bioavailability in soil, two pot experiments were conducted in a greenhouse at the experimental station Maksimir of the Faculty of Agriculture University of Zagreb (Croatia). In a half of both experiments alluvial soil from cultivated land in a Neretva valley (Croatian Mediterranean region) (OT1) was used, and in the other half the same alluvial soil with added peat to increase SOM content (OT2). The soil (OT1 and OT2) was spiked with Cu and Cd at two levels: 250 and 500 mg Cu kg-1, and 5 and 10 mg Cd kg-1. The same treatment with NaCl salinity was applied in both experiments: control, 50 and 100 mM NaCl. Faba bean (Vicia faba L. cv. Aguadulce) was used as a test plant. Copper solubility and therefore bioavailability in soil is lowered by sorption and complexation processes with SOM. Visual MINTEQ speciation revealed that the Cu in the soil solution is mostly present as Cu-dissolved organic carbon (DOC) complex. The proportion of other Cu species in the soil solution rise with increasing Cu concentration, but only if SOM level is not increased. Faba bean uptake of Cu increased with raising soil Cu concentration, although plants may have restricted the translocation of Cu, behaving like metal excluder plants. However, application of SOM decreased plant tissue Cu concentration, yet significantly only for faba bean pod. Nevertheless, results suggest that Cu phytoavailability may be affected by the increase in SOM, and that faba bean pod tissue provides a best (shoots) reflection of bioavailable Cu in soil. The possibility of reduced Cu mobility in salinized soils and/or reduced plant uptake of Cu from a saline rhizosphere is also suggested by obtained results. Application of salts either lowered Cu solubility in soil or reduced plant uptake by excessive salts in the rhizosphere. Then again, plant adaptive mechanisms may modify Cu phytoavailability. Results also point to a possible malfunction of faba bean root plasma membrane under Cu toxicity conditions. This study confirms that Cd is highly mobile between different soil fractions, depending on its total concentration and the presence of inorganic (chlorides) and organic (humics) ligands in surrounding media. Cd speciation was greatly affected by all investigated trial factors, i.e. soil Cd contamination enhanced the proportion of the free Cd2+, raised SOM content induced Cdorgano-complexation with DOC, and increased soil salinity promoted the formation of CdCln2n complexes in soil solution, all of which consequently modified the mobility of Cd in soil. Soil Cd contamination led to an increased plant Cd uptake. The addition of SOM caused a decreased Cd availability to plants, possibly because of the redistribution of Cd to a less available organically-bound Cd fraction. However, bean plants have uptaken the highest amount of Cd in a non-saline environment, indicating that, if soil adsorption capacity for Cd has not been exceeded, increased Cd mobility in soil does not have to result in its increased phytoavailability, than only in Cd transfer between soil solid phases. Additionally, leaf photosynthetic parameters were not affected by soil Cu and Cd contamination, except for chlorophyll content index (CCI) which decreased with soil Cd contamination. Results show that raised SOM can increase soil dehydrogenase acitivity (DHA), whilst increased soil salinity decreases DHA. Although soil Cd contamination did not significantly affect DHA at studied metal concentrations, the results suggested that CdCln2-n has a higher inhibitory effect on DHA than other Cd chemical species in soil solution. DHA decreased with soil Cu contamination, and was even reduced in half at the total soil concentration of 500 mg Cu kg-1. Results also suggest similar inhibitory effect of all Cu species in soil solution on DHA, but also the possibility that DHA may affect Cu soil availability by reducing the formation of metal-DOM complexes in the soil solution

Učinci razine zaslanjenosti vode za navodnjavanje na produktivnost boba (Vicia faba L.)

In Mediterranean region where seawater intrudes porous karst matrix and salinizes soil and water resources, water used for the irrigation of crops is frequently of inadequate quality. Measuring the productivity of horticultural crops under saline conditions helps to determine whether and when to irrigate crops if water is saline, thus balance between crop water and salt stress. A greenhouse pot experiment was set to study the effects of saline irrigation water on faba bean (Vicia faba L.) biomass and yield parameters. NaCl salinity was applied in a nutrient solution as follows: NaCl0 as control (nutrient solution without added NaCl), NaCl50 (control + 50 mM NaCl), and NaCl100 (control + 100 mM NaCl). Five weeks after salinity treatment started, plant height (cm), number of lateral branches per plant, number of pods and seeds per plant, shoot weight (g), pod weight (g) and seed weight (g) were determined. Compared to control, increased irrigation water salinity statistically significantly decreased measured parameters (P<0.01), except for number of branches and pods. Faba bean productivity decreased proportionally to the irrigation water salinity level, suggesting that optimal saline agriculture management strategy can be to allow for the acceptable yield loss in order to avoid plant water stress.Na području Mediterana, gdje dolazi do prodora morske vode kroz porozni krški materijal i zaslanjivanja tala i vodnih resursa, voda koja se koristi za navodnjavanje usjeva često nije odgovarajuće kakvoće. Mjerenje produktivnosti hortikulturnih usjeva u zaslanjenim uvjetima pomaže odrediti može li se navodnjavati zaslanjenom vodom i kada, kako bi se pronašla ravnoteža između vodnog stresa usjeva i stresa soli. Postavljen je pokus u loncima u plasteniku kako bi se istražili učinci zaslanjene vode za navodnjavanje na biomasu i parametre prinosa boba (Vicia faba L.). NaCl sol je primijenjena u hranjivoj otopini kako slijedi: NaCl0 kao kontrola (hranjiva otopina bez dodanog NaCl), NaCl50 (kontrola + 50 mM NaCl), i NaCl100 (kontrola + 100 mM NaCl). Pet tjedana nakon početka tretmana zaslanjenom vodom, izmjerena je visina biljaka (cm), određen broj bočnih izdanaka, mahuna i sjemenki po biljci, masa nadzemnog dijela biljke (g), masa mahune (g) i masa sjemena (g). U usporedbi s kontrolom, povećana zaslanjenost vode za navodnjavanje statistički je značajno smanjila mjerene parametre (P<0.01), osim broja izdanaka i mahuna. Produktivnost boba smanjila se proporcionalno razini zaslanjenosti vode za navodnjavanje, sugerirajući da optimalna strategija poljoprivrednog gospodarenja u zaslanjenim uvjetima može biti dozvoljavanje prihvatljivog gubitka prinosa kako bi se izbjegao vodni stres usjeva

Agricultural Management Strategies for Countering Drought Conditions in Eastern Croatia

The occurrence of drought periods which last for several months is becoming increasingly frequent, even in regions which have not encountered them before. Agricultural production is very sensitive to drought, and in areas where such conditions were rather unexpected, it is also unprepared for limited water management. As an example, in the area of the Biđ-Bosut field located in eastern Croatia, a significant change in the agricultural soil water regime is noticed during a long-term study (2003–2018). From 2003 to 2018, the groundwater level at 4 m below the soil surface showed a decreasing trend of 6–10 cm annually, while this negative trend was even more prominent from 2014 to 2018 (18–71 cm annually). Furthermore, water level in a groundwater aquifer at 15 m below the soil surface showed a decreasing trend of 26–77 cm during 2015–2018. In accordance with the obtained results, this study proposes certain agro-hydrotechnical strategies which can be used in agricultural production to alleviate the effects of drought period. Although these management strategies are primarily described on an eastern continental Croatia example, they can also be applied in all agricultural areas with similar agroecological conditions

Modification of copper and cadmium biovailability to faba bean plant (Vicia Faba L.) as affected by soil organic matter and salinity

Određivanje mobilnosti i biopristupačnosti metala u tlu predstavlja osnovu za procjenu rizika od njihovog potencijalnog uključivanja u hranidbeni lanac. Stoga je cilj rada bio definirati mehanizme kojima organska tvar (OT) i salinitet tla rezultiraju promjenama u mobilnosti i biopristupačnosti bakra (Cu) i kadmija (Cd) u tlu. Pretpostavljeno je da će povećanje OT i zaslanjenosti tla utjecati na mobilnost/biopristupačnost Cu i Cd te mikrobiološku dehidrogenaznu aktivnost (DHA) u tlu. Istraživanje je obuhvatilo 2 pokusa koji su provedeni u kontroliranim uvjetima plastenika na Agronomskom fakultetu u Zagrebu, s bobom (Vicia faba L. cv. Aguadulce) kao test kulturom. Eksperimentalni dizajn pokusa bio je split-split-plot u 3 ponavljanja. Glavni faktor bio je sadržaj OT u 2 razine: tlo uzeto iz područja Donje Neretve (OT1) te isto tlo miješano s tresetom u omjeru 4:1 (OT2). Podfaktor bio je NaCl salinitet u 3 razine (0, 50 i 100 mM), a podpodfaktor kontaminacija tla s 250 i 500 mg kg-1 Cu (pokus 1), odnosno 5 i 10 mg kg-1 Cd (pokus 2) i kontrolna (nekontaminirana) varijanta. Rezultati istraživanja ukazuju da je OT jedna od najznačajnijih pedovarijabli koje utječu na mobilnost/biopristupačnost istraživanih metala u tlu. Dodatak OT u varijanti OT2 smanjio je biopristupačnost Cu u tlu procesima sorpcije i kompleksacije s OT (ukupna koncentracija Cu u tlu povećana je za 5 %, dok je koncentracija Cu u mahuni boba smanjena za 14 %). Rezultati upućuju i na smanjenu biopristupačnost Cu u uvjetima NaCl saliniteta i/ili smanjeno primanje Cu u test kulturu iz zaslanjene rizosfere. Dodatak OT u varijanti OT2 i posljedično povećanje koncentracije DOC-a u otopini tla, smanjuje aktivnost slobodnog Cd2+, a time i njegovo primanje u korijen (koncentracija Cd u listu boba smanjena je za 28 %, u mahuni za 40 % te u sjemenu za 20 %). Primjena NaCl nije rezultirala povećanom biopristupačnošću Cd, nego samo njegovom redistribucijom unutar krute faze tla. Kontaminacija tla Cu i Cd nije utjecala na fotosintetske pokazatelje lista boba, upućujući na zaključak da nije utjecala na produktivnost biljaka boba, iako je indeks sadržaja klorofila (CCI) smanjen za 4 % s Cd10 tretmanom. Dodatak OT u varijanti OT2 povećao je za 30-65 %, a NaCl salinitet smanjio za 28-29 % pri NaCl100 tretmanu dehidrogenaznu aktivnost (DHA) u tlu. Kontaminacija tla Cu smanjila je DHA za 50 % pri Cu500 tretmanu. Kontaminacija tla Cd nije utjecala na DHA, ali modeliranje udjela različitih kemijskih oblika Cd u otopini tla primjenom programa Visual MINTEQ i modela NICA-Donnan upućuje na mogućnost da kompleksi Cd i klorida (CdCln2-n) imaju izraženiji inhibitorni učinak na DHA u tlu.The aim of this research was to study the mechanisms by which soil organic matter (SOM) and increased soil salinity affect copper (Cu) and cadmium (Cd) mobility in soil, as well as the importance of afore mentioned mechanisms for their bioavailability in soil. Therefore, to study the Cu and Cd bioavailability in soil, two pot experiments were conducted in a greenhouse at the experimental station Maksimir of the Faculty of Agriculture University of Zagreb (Croatia). In a half of both experiments alluvial soil from cultivated land in a Neretva valley (Croatian Mediterranean region) (OT1) was used, and in the other half the same alluvial soil with added peat to increase SOM content (OT2). The soil (OT1 and OT2) was spiked with Cu and Cd at two levels: 250 and 500 mg Cu kg-1, and 5 and 10 mg Cd kg-1. The same treatment with NaCl salinity was applied in both experiments: control, 50 and 100 mM NaCl. Faba bean (Vicia faba L. cv. Aguadulce) was used as a test plant. Copper solubility and therefore bioavailability in soil is lowered by sorption and complexation processes with SOM. Visual MINTEQ speciation revealed that the Cu in the soil solution is mostly present as Cu-dissolved organic carbon (DOC) complex. The proportion of other Cu species in the soil solution rise with increasing Cu concentration, but only if SOM level is not increased. Faba bean uptake of Cu increased with raising soil Cu concentration, although plants may have restricted the translocation of Cu, behaving like metal excluder plants. However, application of SOM decreased plant tissue Cu concentration, yet significantly only for faba bean pod. Nevertheless, results suggest that Cu phytoavailability may be affected by the increase in SOM, and that faba bean pod tissue provides a best (shoots) reflection of bioavailable Cu in soil. The possibility of reduced Cu mobility in salinized soils and/or reduced plant uptake of Cu from a saline rhizosphere is also suggested by obtained results. Application of salts either lowered Cu solubility in soil or reduced plant uptake by excessive salts in the rhizosphere. Then again, plant adaptive mechanisms may modify Cu phytoavailability. Results also point to a possible malfunction of faba bean root plasma membrane under Cu toxicity conditions. This study confirms that Cd is highly mobile between different soil fractions, depending on its total concentration and the presence of inorganic (chlorides) and organic (humics) ligands in surrounding media. Cd speciation was greatly affected by all investigated trial factors, i.e. soil Cd contamination enhanced the proportion of the free Cd2+, raised SOM content induced Cdorgano-complexation with DOC, and increased soil salinity promoted the formation of CdCln2n complexes in soil solution, all of which consequently modified the mobility of Cd in soil. Soil Cd contamination led to an increased plant Cd uptake. The addition of SOM caused a decreased Cd availability to plants, possibly because of the redistribution of Cd to a less available organically-bound Cd fraction. However, bean plants have uptaken the highest amount of Cd in a non-saline environment, indicating that, if soil adsorption capacity for Cd has not been exceeded, increased Cd mobility in soil does not have to result in its increased phytoavailability, than only in Cd transfer between soil solid phases. Additionally, leaf photosynthetic parameters were not affected by soil Cu and Cd contamination, except for chlorophyll content index (CCI) which decreased with soil Cd contamination. Results show that raised SOM can increase soil dehydrogenase acitivity (DHA), whilst increased soil salinity decreases DHA. Although soil Cd contamination did not significantly affect DHA at studied metal concentrations, the results suggested that CdCln2-n has a higher inhibitory effect on DHA than other Cd chemical species in soil solution. DHA decreased with soil Cu contamination, and was even reduced in half at the total soil concentration of 500 mg Cu kg-1. Results also suggest similar inhibitory effect of all Cu species in soil solution on DHA, but also the possibility that DHA may affect Cu soil availability by reducing the formation of metal-DOM complexes in the soil solution

Hyperaccumulators for potentially toxic elements: A scientometric analysis

Phytoremediation is an effective and low-cost method for the remediation of soil contaminated by potentially toxic elements (metals and metalloids) with hyperaccumulating plants. This study analyzed hyperaccumulator publications using data from the Web of Science Core Collection (WoSCC) (1992–2020). We explored the research status on this topic by creating a series of scientific maps using VOSviewer, HistCite Pro, and CiteSpace. The results showed that the total number of publications in this field shows an upward trend. Dr. Xiaoe Yang is the most productive researcher on hyperaccumulators and has the broadest international collaboration network. The Chinese Academy of Sciences (China), Zhejiang University (China), and the University of Florida (USA) are the top three most productive institutions in the field. China, the USA, and India are the top three most productive countries. The most widely used journals were the International Journal of Phytoremediation, Environmental Science and Pollution Research, and Chemosphere. Co-occurrence and citation analysis were used to identify the most influential publications in this field. In addition, possible knowledge gaps and perspectives for future studies are also presented

Estimation of precipitation fraction in the soil water of the Hillslope Vineyard using stable isotopes of water

This paper presents research related to the estimation of the precipitation fraction in the soil water of a sloped vineyard at the SUPREHILL Critical Zone Observatory (CZO) in Zagreb, Croatia. Numerous investigations have shown that exploration of hillslope soils can be very challenging due to the existence of heterogeneity and different soil properties, as well as due to anthropogenically induced processes, which can affect precipitation infiltration and soil water flow. Within this research, physicochemical soil properties, soil water content (SWC), and isotopic composition of soil water and precipitation

Effect of fire induced water repellency on soil hydraulic properties and water flow

Water infiltration into the root zone, its retention in soil and drainage from the soil profile, are highly sensitive to the presence, degree and persistence of soil water repellency (SWR). Prolonged drought periods and wildfires can increase SWR substantially, thus    the aim of this study was to determine the effect of forest fire-induced water repellency    on soil hydraulic properties, infiltration and water flow in unsaturated soil (vadose) zone. Infiltration experiments with water and ethanol were conducted on forest sites, selected according to their exposure to fire: heavily burned (A), burned (B) and non-affected as the control site (C). Infiltration data were used as an input for inverse determination of soil hydraulic parameters required for computer model calibration (HYDRUS 2D/3D). Then, a one-year climatic scenario for 2016 with measured meteorological data was simulated using HYDRUS-1D software. Data showed that in the case of soil exposure to high temperatures (forest fires), a relatively large increase of SWR is observed. Compared to the control plot, a considerably greater difference between the hydraulic conductivity, Ks, values for water and ethanol was found at both fire affected plots. This suggested positive relationship between soil water repellency and reduced water infiltration. Numerical simulation of the intensive (extreme) rainfall event clearly showed that SWR affects soil water balance by reducing the infiltration and increasing the surface runoff

KORIŠTENJE STABILNIH IZOTOPA VODE (Δ2H I Δ18O) ZA PROUČAVANJE PODRIJETLA VODE U TLU PADINSKOGA VINOGRADA: PRVI REZULTATI

The diversity of processes taking place in hillslope agro-ecosystems makes the estimation of vadose zone dynamics rather challenging. This paper presents the first insight into the research of volumetric water content, granulometric composition, meteorological data, precipitation and soil-water isotopic composition conducted within the SUPREHILL project at its vadose zone observatory. The main goals of this research are related to the evaluation of soil-water origin at the hillslope vineyard, but also to the estimation of depths until which precipitation infiltrates and where the occurrence of preferential flow is possible. For that purpose, hydrometeorological data, granulometric composition and stable isotopesof hydrogen (δ2H) and oxygen (δ18O) from precipitation and sampled soil water have been used. The results indicate the existence of a different isotopic signature in soil water, which suggests different infiltration patterns in the investigated area. Also, the results point out that surface runoff, subsurface runoff, and most of the passive wick lysimeters respond to precipitation, while the response of suction probes located at deeper depth is not that evident. This corresponds to the results related to the variation of water content at different depths. All the results indicate the possible existence of a low permeable layer at an approximate depth of 60 cm. Furthermore, preferential flow, if it exists, can be expected from the shallowest depths of the vineyard to a maximum depth of 80 cm. It is expected that an established long-term monitoring network at the SUPREHILL Observatory will give a more precise definition of soil-water behaviour and the existence of preferential flow.Raznolikost procesa koji se odvijaju unutar vadozne zone pri padinskim agroekosustavima čini procjenu dinamike vode izazovnom. Ovaj rad predstavlja prvi uvid u rezultate volumetrijskoga sadržaja vode, granulometrijskoga sastava tla, meteoroloških podataka te izotopni sastav oborina i vode u tlu istraživanih u sklopu projekta SUPREHILL, to jest njegova opservatorija. Glavni ciljevi ovoga rada vezani su za procjenu podrijetla vode u tlu padinskoga vinograda, ali i za procjenu dubine do koje se oborine infiltriraju te gdje je moguća pojava preferencijalnoga toka. Za navedenu svrhu korišteni su hidrometeorološki podatci, granulometrijski sastav tla te stabilni izotopi vodika (δ2H) i kisika (δ18O) iz oborina te iz uzorkovane vode iz tla. Rezultati upućuju na postojanje različitoga izotopnog potpisa u vodi u tlu, što sugerira različite obrasce infiltracije na istraživanome području. Također, rezultati pokazuju da sustavi za površinsko i podzemno otjecanje te većina pasivnih lizimetara reagiraju na oborine, dok odaziv usisnih sondi instaliranih na većim dubinama nije očit. Navedeno odgovara rezultatima koji se odnose na varijaciju sadržaja vode u tlu na različitim dubinama. Svi rezultati upućuju na mogućnost postojanja slabije propusnoga sloja na približno 60 cm dubine. Nadalje, preferencijalni tok vode, ako postoji, prema ovim saznanjima može se očekivati do dubine od 80 cm. Očekuje se da će dugoročno praćenje podataka putem uspostavljene senzorske mreže u SUPREHILL opservatoriju preciznije definirati ponašanje vode u tlu i postojanje preferencijalnoga toka vode