Textiles made from natural sources, such as cotton and flax, have advantages over those made of synthetic fibers in terms of sustainability. Unlike major synthetic fibers that have a negative impact on the environment due to poor biodegradability, cotton cellulose is a renewable material.Cotton cellulose fibers exhibit various attractive characteristics such as softness and inexpensiveness. Cellulosic textiles can be easily wetted, since the structure contains a large amount of hydrophilic hydroxyl groups, and when water repellency is needed, this is a disadvantage. Currently, paraffin waxes or fluorinated silanes are used to achieve hydrophobicity, but this contradicts the concept of green chemistry since these chemicals are not biodegradable. The use of bio-based materials like forest residues or side-streams from forest product industries might be a good alternative, since this not only decreases the pressure on the environment but can also increase the value of these renewable resources.Betulin is a hydrophobic extractive present in the outer bark of birch trees (Betula verrucosa). Nowadays, the birch bark containing betulin generated in the paper industry is disposed of by incineration as a solid fuel to provide energy, but this application is not highly valuable and this motivates us to see whether betulin can be used as a hydrophobe to prepare waterproof cellulosic textiles. Methods of dip-coating, film compression molding and grafting were performed to build “betulin-cellulosic textile system” to render the textile with hydrophobicity and other functions. The textile impregnated in a solution of betulin-based copolymer exhibited a contact angle of 151°, which indicated that superhydrophobicity can be reached. AATCC water spray test results showed that cellulosic textile coated with betulin-based film had a water repellency of 80, which is the third highest class according to the rating standards. Betulin-grafted textiles were also prepared and showed a static water contact angle of 136°, and an antibacterial property with a bacterial removal of 99%.This thesis proposes that betulin can be used as a green alternative in functional material preparation. By developing betulin, a more value-added application rather than incineration can be achieved. / <p>QC 20190205</p>

An intrinsic link exists between soil moisture and soil nitrogen. Factors that increase or decrease soil moisture can have a profound effect on soil nitrogen cycling, which may have later repercussions in the plant community. Post-fire soil water repellency is one factor that can limit soil moisture acquisition and may indirectly affect nitrogen cycling and weed invasion in woody islands of fertility. Plots centered on burned Juniperus osteosperma trees were either left untreated or treated with a surfactant to ameliorate water repellency. Two years later, soils were excavated from the untreated and treated field plots. In the greenhouse, half of each soil type received a surfactant treatment while the other half was left untreated. Pots were seeded with either Bromus tectorum or Pseudoroegneria spicata. Analysis of field soil prior to the greenhouse trial showed that untreated, repellent soils had inorganic nitrogen levels an order of magnitude higher than wettable, surfactant-treated soils. Greenhouse pots that had received a surfactant treatment in the field and/or greenhouse had similar soil water content, plant density, and above ground biomass, which were, respectively, 55-101%, 31 to 34 -fold, and 16 to 18 -fold greater than pots without a surfactant treatment. No species effects were found. This study indicates that water repellency can reduce wetting and retention of water in the soil while promoting the retention of high levels of inorganic nitrogen. However, the effects of soil water repellency on inorganic nitrogen appeared to have a minimal effect on plant growth compared to the effect of soil water repellency on water availability.

It is widely known that the textile industry is a large polluter and that fast fashion in particular has sustainability issues. Meanwhile, second-hand stores struggle to sell their products in Europe, leading to most clothes either being exported and/or landfilled. This issue is partially driven by costumers not knowing what performance they can expect from second-hand products. In this study, the water repellency of used hardshell jackets will be evaluated with the goal of proving that second-hand products still have enough performance for reuse. This implies that prolonging the lifetime of waterproof jackets is possible, which will reduce CO2 emissions. Various standards are evaluated and a new method, dubbed the stream impact test is defined, trialed and compared to results from the ISO 4920 spray test. In order to estimate the full potential of reusing jackets, the effects of rejuvenating used jackets, by washing the mand using water repellent spray, are also tested. The current standards for aging fabric used by the industry to prove the durability of water repellency will be evaluated using both the ISO 4920 spray test and the new stream impact test. The testing concludes that while the new method has certain issues, it does achieve it’s core objectives and provides a new perspective on the water repellency of new, used and rejuvenated fabrics. It also shows that, on average, rejuvenating jackets has a good effect on the water repellency of jackets and that. During the testing of used jackets with the stream impact method, jackets are found with water repellent properties between those of new fabric and very old fabric. This suggests that there are jackets with a lot of technical performance left that are discarded, which would be ideal for reuse and allowing the clothing industry to become more sustainable.

The influence of soil water repellency (WR) on vegetation recovery after a fire is poorly understood. This dissertation presents strategies to broaden opportunities for enhanced post-fire rangeland restoration and monitoring of burned piñon and juniper (P-J) woodlands by: 1) mapping the extent and severity of critical and subcritical WR, 2) determining the influence of WR on soil ecohydrologic properties and revegetation success, and 3) evaluating the suitability of a wetting agent composed of alkylpolyglycoside-ethylene oxide/propylene oxide block copolymers as a post-fire restoration tool for ameliorating the effects of soil WR and increasing seedling establishment. Results indicate that: • Post-fire patterns of soil WR were highly correlated to pre-fire P-J woodland canopy structure. Critical soil WR levels occurred under burned tree canopies while sub-critical WR extended out to approximately two times the canopy radius. At sites where critical soil WR was present, infiltration rate, soil moisture, and vegetation cover were significantly less than at non-hydrophobic sites. These parameters were also reduced in soils with subcritical WR relative to non-hydrophobic soils (albeit to a lesser extent). Aerial photography coupled with feature extraction software and geographic information systems (GIS) proved to be an effective tool for mapping P-J cover and density, and for scaling-up field surveys of soil WR to the fire boundary scale. • Soil WR impairs seed germination and seedling establishment by decreasing soil moisture availability by reducing infiltration, decreasing soil moisture storage capacity, and disconnecting soil surface layers from underlying moisture reserves. Consequently, soil WR appears to be acting as a temporal ecological threshold by impairing establishment of desired species within the first few years after a fire. • Wetting agents can significantly improve ecohydrologic properties required for plant growth by overcoming soil WR; thus, increasing the amount and duration of available water for seed germination and seedling establishment. Success of this technology appears to be the result of the wetting agent increasing soil moisture amount and availability by 1) improving soil infiltration and water holding capacity; and 2) allowing seedling roots to connect to underling soil moisture reserves.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2017-02-22T13:08:59Z No. of bitstreams: 1 Cidney Barbosa Bezerra.pdf: 2167272 bytes, checksum: 5f0cef27593c95187e77811cdb520cbb (MD5) / Made available in DSpace on 2017-02-22T13:08:59Z (GMT). No. of bitstreams: 1 Cidney Barbosa Bezerra.pdf: 2167272 bytes, checksum: 5f0cef27593c95187e77811cdb520cbb (MD5) Previous issue date: 2016-08-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The South Agreste Pernambucano has an agricultural and very large land diversification, but the management of the soil used in the production is mostly inadequate, resulting in economic and low productivity losses, allied to it have weather conditions quite different typical of a transitional environment . However the city of Brejão has a special condition with cooler and rainy weather and deeper soils and well structured, with occurrence horizon latosols with the humic something characteristic in this swamp of altitude. So the aim of this study was to investigate the changes in chemical, physical and water attributes of the surface horizon humic an Oxisol subjected to different forms of management in the Swamp region of South Agreste Altitude Pernambuco, and investigate the soil repellency water. The disturbed and undisturbed soil samples were collected in a native forest (MN), pasture 5 years (PA5) and grazing 30 (PA30) in three layers 0 to 10 cm, 10 to 20 cm and 20 to 30 cm and evaluated the chemical, biological, physical and water attributes, as was also done an infiltration test with simple ring. Chemical attributes presented typicality dystrophic yellow latosols, and attributes related to the acidity showing significant results mainly in the surface layer. For biological attributes your changes are more significant in macroaggregates. Have the physical attributes that most change with inadequate management are the bulk density (Ds) and porosity consequently these physical attributes are linked to water retention in the soil and all water dynamics. For the infiltration test it is clear the presence of soil water repellency. / O Agreste Meridional pernambucano possui uma diversificação agropecuária e de solos muito grande, porém o manejo do solo empregado na produção é em sua maioria inadequado, acarretando em perdas econômicas e baixa produtividade, aliadas a isso temos condições climáticas bastante diferentes típicas de um ambiente de transição. No entanto a cidade de Brejão possui uma condição especial, com clima mais frio e chuvoso e solos mais profundos e bem estruturado, com ocorrência de latossolos de horizonte com A húmico algo característico nesse brejo de altitude. Assim o objetivo deste trabalho foi investigar as alterações nos atributos químicos, físicos e hídricos do horizonte superficial A húmico de um Latossolo Amarelo submetido a diferentes formas de manejo na região do Brejo de Altitude do Agreste Meridional pernambucano, e investigar a repelência do solo a água. As amostras deformadas e indeformadas do solo foram coletadas em uma área de mata nativa (MN), pasto de 5 anos (PA5) e pasto de 30 anos (PA30), em três camadas 0 a 10 cm, 10 a 20 cm e 20 a 30 cm e foram avaliados os atributos químicos, biológicos, físicos e hídricos, como também foi realizado um teste de infiltração com anel simples. Os atributos químicos apresentaram tipicidade de latossolos amarelo distróficos, e atributos relacionados com a acidez apresentando resultados significativos principalmente na camada superficial. Para os atributos biológicos suas alterações são mais expressivas nos macroagregados. Já os atributos físicos que mais sofreram alterações com o manejo inadequado são a densidade do solo (Ds) e a porosidade, consequentemente esses atributos físicos estão ligados a retenção de água no solo e toda dinâmica hídrica. Pelo teste de infiltração fica claro a presença de repelência do solo a água.

The objectives of this study were to investigate stability related basic wood properties and to determine stability performance of New Zealand grown Douglas-fir and those of radiata pine wood. In this study, nine 60-year old Douglas-fir trees and thirteen 26-year old radiata pine trees were selected from forests in Canterbury region. From these trees, 36 discs of 200 mm thick (13 for Douglas-fir and 23 for radiata pine) and 388 boards with dimensions of 100mm x 50mm x 4.8m (210 fro Douglas-fir and 178 fr radiata pine) were prepared. From the prepared discs, 515 specimens (204 for Douglas-fi and 211 for radiata pine) were prepared for green moisture content (MC) and basic density measurements, The same total number of 515 specimens (205 for Douglas-fir and 210 for radiata pine) were also prepared for shrinkage measurements. From the green MC specimens, green weight, volume and oven-dry weight were measured while for the shrinkage specimens, dimensions and weights were measured at equilibrium for nine humidity conditions. These data were used to analyse basic wood properties and moisture uptake characteristics for both Douglas-fir and radiata pine. Variation of shrinkage within a tree and between trees was also studied for both species. After this, selected specimens (36 for Doulas-fir and 36 for radiata pine) were further tested in water immersion for water repellence examination. The 388 full size boards (100mmx50mmx4.8m) were used for studies on distortion and acoustic properties at a sawmill (Southland Timber Ltd.). Dimensions, weights and acoustic velocity were measured from each board before and after drying. These data were used to analyse distortion and strength characteristics for both Douglas-fir and radiata pine. Comparison of the relative stability of full sized Douglas-fir and radiata pine structural timber was investigated in this study. The results from small sample study confirmed that Douglas-fir is much stronger, has lower longitudinal shrinkage and lower gradient in corewood which can be used to explain the better dimensional stability of Douglas-fir than radiate pine although there is significant variability in the shrinkage for both Douglas-fir and radiate pine. In water immersion tests, Douglas-fir has better water repellency property than radiata pine over 2000 hours period during water immersion. Under the same commercial practice in sawing and kiln drying, it is clearly shown that Douglas-fir timbers were straighter with lower levels of distortion than radiata pine at similar final moisture content. It is also interesting to note that the final moisture content in a range of 13-18% for Douglas-fir did not have significant impact on timber distortion but a negative trend was observed for radiata pine with MC in a range of 9 -14%. Tree heights showed clear influence on twist for radiata pine timbers, but it was not clearly observed from Douglas-fir timbers. Corewood proportion is found to have negative impact on the timber distortion for both Douglas-fir and radiata pine. Douglas-fir timbers showed much higher average acoustic MOE value than radiata pine timbers at similar final moisture content. Because of the various proportion of corewood, the shrinkage varied greatly along the stem height and along the disc radius direction for the two species. This variation caused the difference of distortion between corewood, outerwood and transition wood, but the difference between butt log, middle log and top log is inconsistent. Therefore, it is recommended that the corewood proportion to be a criterion for the timber pre-sorting. Variation of stability performance between trees was also found to be significant for the two species, and methods need to be developed for log sorting as well to reduce the timber distortion degradation. Non-destructive testing method such as acoustic tool may be offered to be a new approach for sorting logs, but it is also necessary to be aware of the significant difference between species. The outcome from this project includes better understanding of Douglas-fir for structural applications. The conclusion can be drawn that Douglas-fir has superior quality for its strength, durability and moisture resistance. Douglas-fir is also claimed to have uniform properties and thus to be more stable compared to radiata pine. Douglas-fir timbers showed much higher acoustic MOE value than radiate pine timbers as similar final moisture content.

The Lockheed Fire burned 31 km2 (7,660 acres) of the Scotts Creek watershed in August 2009. 4.5 km2 (1,100 acres) of California Polytechnic State University’s educational and research facility at Swanton Pacific Ranch. The burned region presented an opportunity for studying the hydrologic response of burned soils in the Santa Cruz Mountains where there is insufficient post-fire studies regarding fire-effects on watershed processes such as infiltration and near-surface runoff. Soil infiltration and soil water repellency were evaluated with rainfall simulations, Mini-disk Infiltrometer (MDI) and water drop penetration time tests (WDPT) at sites represented by variations in burn severity, soils, and vegetation types throughout the Scotts Creek watershed each year for 5 years following the burn. Mixed-effects modeling was utilized on the 3 datasets to evaluate if changes could be detected in infiltration rates and water repellency following the fire. Rainfall simulations and WDPT tests showed that the fire did not have a statistically-significant impact on infiltration rates or soil water repellency, whereas the MDI tests detected a statistically-significant impact on post-fire infiltration. While the MDI results showed that fire had a significant impact on the hydrologic response over time, questions arose regarding challenges associated with sampling suggesting the method may not be pursued on steep slopes with high surface rock fragments or in the presence of large soil macropores. It is recognized that additional understanding would be gained from having multiple replications at each site every year and tests could be conducted on a subwatershed scale to account for the naturally occurring variability of larger watersheds.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Soil hydrophobicity can be conceptually defined as soil repellency to water and is associated with the covering of soil particles by hydrophobic organic substances which interact with mineral particles and pores in a complex way, making soil wetting difficult. The objectives of this study were to: (i) determine the biochemical composition of vegetation, physical and chemical properties of soil organic matter fractions and their relationships to the occurrence and degree of soil hydrophobicity; (ii) analyze the effects of hydrophobic compounds at different intensities on sorptivity and water retention curve; (iii) measure and monitor the effects of variation of soil temperature and water content on the variability of the degree of soil hydrophobicity during a drying cycle. Soil samples were collected from different soil classes in the Rio Grande do Sul and Santa Catarina States, southern Brazil. From the 0-5, 5-10 and 10-15 cm soil layers, undisturbed samples (in blocks) were collected for the determination of sorptivity while preserved samples were collected using core samplers (volume of 47 cm³) for the evaluation of water retention curve, soil bulk density, total porosity, macroporosity and microporosity. From these layers, deformed samples were also collected for soil chemical and physical characterization. However, part of the samples used for the determination of water retention curves were previously subjected to sequential chemical extraction with acetone and a solution of isopropanol:ammonia to remove hydrophobic compounds. Soil carbon analysis consisted of determination of total organic carbon, physical (> 53μm and <53μm), and chemical (fulvic and humic acids and humin) fractions. Water and ethanol sorptivity was determined using tension micro-infiltrometer. Hydrophobicity was evaluated by comparing water and ethanol sorptivity values and soil-water contact angle was calculated from the hydrophobicity index. The effect of temperature was measured using PVC cylinder (785 cm³) constructed with disturbed samples from different soils, wetted and dried under different temperatures (20, 45 and 70 °C) and the hydrophobicity was determined using the water droplet penetration time method. Hydrophobicity had an intimate relationship with soil organic carbon content, mainly organic compounds accumulated in physical fractions <53 μm and chemical fraction humin, indicating that hydrophobic compounds are highly recalcitrant and are strongly associated with silt and clay fractions, forming stable organo-mineral complexes, and at the same time, covering all or part of surfaces of mineral particles or aggregates. The existence of these hydrophobic compounds caused changes in sorptivity and soil-water contact angle, directly affecting capillary and soil water retention curve, and reduced the volume of water retained at lower potentials. The heating of the soil at temperatures at or below 45 °C did not alter the intensity of hydrophobicity but there were changes when soil temperature exceeded 70 °C or when the soil moisture was drastically reduced. / A hidrofobicidade do solo pode ser conceitualmente definida como a repelência do solo à água e está associada ao recobrimento das partículas do solo por substâncias orgânicas hidrofóbicas, que interagem de forma complexa com os poros e partículas minerais, dificultando o molhamento do solo. Os objetivos deste trabalho foram: (i) determinar a composição bioquímica da vegetação, das frações físicas e químicas da matéria orgânica e suas relações com a ocorrência e grau de hidrofobicidade; (ii) analisar os efeitos dos compostos hidrofóbicos em diferentes intensidades na sortividade e na curva de retenção de água; (iii) avaliar e monitorar os efeitos da variação da temperatura e do conteúdo de água na variação do grau de hidrofobicidade do solo ao longo de um ciclo de secagem. Foram coletadas amostras de solo de diferentes classes de solos existentes no Estado do Rio Grande do Sul e Santa Catarina. Nas camadas de 0 5, 5 10 e 10 15 cm foram coletadas amostras indeformadas (blocos), para a avaliação da sortividade e amostras com estrutura preservada, com cilindros metálicos (47 cm³), para a determinação da curva de retenção de água, densidade do solo, porosidade total, macroporosidade e microporosidade. Nessas camadas também foram coletadas amostras deformadas para a caracterização química e física dos solos. No entanto, parte das amostras utilizadas na determinação da curva de retenção de água foram previamente submetidas a uma extração química sequencial com acetona e uma solução de isopropanol:amônia para remoção dos compostos hidrofóbicos. A análise do carbono constou da determinação do carbono orgânico total e da determinação das frações físicas (>53μm e <53μm) e químicas (Ácidos Fúlvicos, Ácidos Húmicos e Humina). A sortividade da água e do etanol foram determinadas com um micro-infiltrômetro de tensão. A hidrofobicidade foi avaliada comparando valores de sortividade da água e do etanol. O ângulo de contato água-solo foi calculado a partir do índice de hidrofobicidade. O efeito da temperatura foi mensurado em cilindros de PVC (785 cm³) construídos com amostras desagregadas dos diferentes solos. As amostras foram umedecidas e secas sob diferentes temperaturas (20, 45 e 70°C), sendo a hidrofobicidade determinada simultaneamente pelo método do tempo de penetração da gota de água. A hidrofobicidade apresentou uma íntima relação com o teor de carbono orgânico do solo, principalmente com os compostos orgânicos acumulados na fração física <53 μm e na fração química da Humina, indicando que os compostos hidrofóbicos provavelmente apresentam elevada recalcitrância e estão fortemente associados às frações silte e argila, formando complexos organo-minerais estáveis, ao mesmo tempo em que recobrem total ou parcialmente a superfície de agregados ou partículas minerais. A existência desses compostos hidrófobos causa alterações na sortividade e no ângulo de contato água-solo, afetando diretamente a capilaridade e a curva de retenção do solo, reduzindo o volume de água retido nos menores potenciais. O aquecimento do solo à temperaturas inferiores a 45 °C não causa modificações na intensidade da hidrofobicidade, que é alterada somente quando a temperatura do solo excede a 70 °C ou quando a umidade do solo é acintosamente reduzida.

Skaljackor är ett praktiskt plagg för att reglera komforten för användaren. Detta gör de genom att skaltyger kan hålla vind och väta ute samtidigt som de är genomsläppliga för vattenånga. Det är känt att funktionaliteten i skaltyger försämras med tiden men det finns fortfarande en osäkerhet om hur olika åldringsfaktorer påverkar den. Det arbete som denna rapport redovisar har utsatt fem olika tyger för mekanisk nötning och UV-exponering för att ta reda på dess påverkan på skaltygets funktionalitet. Arbetet har gjorts i syfte att öka kompetensen om hur skaltyger åldras för att kunna utveckla mer hållbara skaljackor i framtiden. Åldringen via mekanisk nötning genomfördes med 30 000 cykler tyg mot tyg i en Martindale M235 Abrasion tester. Åldring med UV-ljus genomfördes under 250h enligt ISO 105-B04:1994 i väderkammare. Därefter testades de åldrade tygerna i vattentäthet, vattenavvisning, andningsförmåga och luftgenomsläpplighet. Testerna utvärderades på icke åldrat tyg samt åldrat tyg. Resultatet visar att både UV och mekanisk nötning har en tydlig påverkan på skaltygernas funktionalitet. Det krävs dock vidare forskning för att undersöka åldringsgrad och hur de påverkar varandra. / Shell jackets are a practical garment for regulating user comfort. This is due to the fabric that keep wind and water out while still allowing moisture vapor to permeate. It is known that the functionality of the fabrics deterioate over time, but there is still an uncertainty about the impact of various aging factors. The work presented in this report subjected five different shell fabrics to abrasion and UV exposure to determine their impact on the functionality. This was done with the aim of increasing knowledge about the aging of shell fabrics in order to develop more sustainable shell jackets in the future. Aging was performed through 30 000 cycles of fabric-to-fabric abrasion using a Martindale M235 Abrasion tester, and for 250h of UV-exposure in a weather chamber according to ISO 105-B04:1994. Subsequently the aged fabrics were tested for water penetration resistance, water repellency, breathability and air permeability. The tests were evaluated on new fabrics and aged fabrics. The results indicate that both UV and abrasion have an impact on the funtionality of shell fabrics. However,further research is required to investigate the degree of aging and how they mutually affect each other. / <p>Betygsdatum 2023-06-07</p>

Dynamic soil water repellency is an important soil phenomenon in the vadose zone as it is now recognised that most soils in the world are likely to express some degree of reduced wettability and/or long term hydrophobicity. Fractional wettability and contact angles are, however, rarely discussed or quantified for natural systems. This is particularly the case in the presence of dynamic contact angles. Soil water repellency remains a persistent impediment and challenge to accurate conceptual and numerical models of flow and storage in the vadose zone. This dissertation addresses the opportunity and pressing need for contributions that develop better quantifiable definitions, descriptions, and understanding of soil water repellency. Using materials collected from post wildfire sites, this work employs water and ethanol to identify, isolate, and quantify contact angle dynamics and fractional wettability effects during infiltration. Varied concentrations of water and ethanol solutions were applied to soils and observed through X-ray microtomography, tension infiltration experiments, and moisture content measurements in the laboratory and field. Several analyses from lab and field investigations showed that applications of ethanol and specifically, water-ethanol aqueous solutions provide unique additional insights into proportions of media that remain non-wettable and how those proportions affect overall hydrologic processes, which are not readily observable through water infiltrations alone. Observations include the wetting up of microporous structures, reduced storage, and changes in unsaturated hydraulic conductivities. Challenges which develop as a consequence of variable fluid properties including changes to operational pore assemblages, slow down of wetting fronts, and non-uniqueness relative to infiltration responses are addressed. Important insights and contributions were developed through this approach and water-ethanol mixtures are valuable tools for developing greater quantification and mechanistic data to better inform our models and understanding of dynamic soil water repellency. / Dissertation / Doctor of Philosophy (PhD) / Quantifying fluid behaviours in soils is important for a host of environmental, social, and economic reasons. Over the last 25+ years, one soil phenomenon has garnered increased attention because it interferes with our ability to carry out this work. Soils that are or become water repellent develop all over the world and where hydrophobic or non-wetting substances can enter soil and remain in pore spaces or as coatings on particles. To assist in the tracking and management of its complex effects on water storage and infiltration, the goals of this work were to develop fundamental insights into the manifestation and effects of this variable soil property on key hydrologic properties and processes. This work tests a new conceptual model for understanding these systems through both field and laboratory work and using a number of different technologies. These include X-ray microtomography (μXCT), tension infiltrometry, and more regularly applied techniques which are sensitive to changes in repellency. The works shows how combining fractional wettability and contact angle dynamics generates a stereoscopic conceptual framework which facilitates increased capacity for quantifying and understanding of soil systems expressing dynamic soil water repellency.