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The warming climate is rapidly changing the circumpolar region, presenting new opportunities and challenges for agricultural production in South Greenland. The warming climate is projected to increase the frequency of drought periods, but little is known about the soil–water retention (SWR) and the plant available water (PAW) of the agricultural soils in the region. This study aimed to measure the SWR and PAW of Greenlandic agricultural soils and evaluate the effect of organic carbon (OC) and clay (CL) content using pedotransfer functions based on OC and CL. The study included 464 South Greenlandic agricultural soil samples from 20 fields with a wide distribution in clay (0.016–0.184 kg kg−1) and OC contents (0.006–0.254 kg kg−1). Pedotransfer functions were successfully developed for estimating the gravimetric water content (w) at five soil–water potentials (−1500, −100, −30, −10, and −5 kPa) and PAW. The OC content was the primary variable governing the gravimetric water content at each soil–water potential, evidenced by R2 values consistently above 0.80. The effect of OC on the gravimetric water content at −1500 kPa was close to the range reported in the literature, but OC effects were markedly higher between −100 and −5 kPa. Overall, this study highlights a substantial effect of OC on the PAW as a 1% increase in OC increased PAW by more than 4%, which is almost twice the value of a recent meta-study. Our study highlights the potentially dominating effects of organic matter on soil–water balance and availability in high-latitude agriculture.

Soil water repellency (WR) is ubiquitous across Greenlandic cultivated fields, which may constrain agricultural production. Fine-grained glacial rock flour (GRF) is available in the surrounding landscape, which could serve as a soil amendment. We tested whether the application of GRF (rates of 0, 50, 100, 300, and 500 ton ha−1) reduced the WR across two field trials in South Greenland. The field trials, Upernaviarsuk (UP) and South Igaliku (SI), differed in clay (UP: 0.05–0.11 kg kg−1; SI: 0.03–0.05 kg kg−1) and organic carbon (OC) contents (UP: 0.04–0.13 kg kg−1; SI: 0.01–0.03 kg kg−1). We measured WR across gravimetric water contents (W) from oven-dry to the W where WR ceased (WNON) to obtain whole WR-W curves. Most soils became hydrophilic around air-dry conditions at application rates of ≥300 ton ha−1, likely due to increased clay:OC ratios. Application rates of ≥300 ton ha−1 generally reduced the trapezoidal integrated area of the WR-W curve (WRAREA), WNON, and WR after heat treatments at 105°C (WR105) and 60°C (WR60). The WR105 was significantly reduced in both fields at 500 ton ha−1, while WR60 was significantly reduced in UP at application rates of ≥300 ton ha−1. The GRF effects were masked by texture and OC variations. Normalizing WRAREA to the water vapor sorption isotherms (utilizing the Campbell-Shiozawa model) revealed that GRF consistently reduced the normalized WRAREA. The SI field showed the largest reduction in the normalized WRAREA, likely due to its lower OC and clay contents. Thus, GRF could reduce WR across two Greenlandic field trials.

Soil water repellency (SWR) is a common phenomenon across agricultural soils of South Greenland that can negatively affect soil functions. Existing methods to measure SWR as a function of water content (w) are laborious. This study was conducted to compare the potential of visible–near-infrared spectroscopy (vis–NIRS) as an alternative method to pedotransfer functions (PTFs) for predicting four SWR indices in 143 agricultural soils from South Greenland (clay, 0.016–0.172 kg kg–1; organic carbon (OC), 0.009–0.241 kg kg–1). Pedotransfer functions were established by multiple linear regression based on OC, clay, and pH. Partial least squares regression (PLS-R) and interval PLS-R were applied to build vis–NIRS prediction models (vis–NIR range 400–2,500 nm). The area under the SWR–w curve (SWRarea) and the critical soil water content (wnon) were accurately predicted by PTFs (R2 =.90; R2adj =.91) while the SWR after 60 °C pretreatment (SWR60), and the integrative repellency dynamic index (IRDI) were predicted less accurately (R2adj =.36; R2adj =.27). Vis-NIRS models with variable selection performed at a better or close to the same level of accuracy as PTFs (SWRarea, R2 =.88; wnon, R2 =.90; SWR60, R2 =.63; IRDI, R2 =.54). This study demonstrated vis–NIRS as a valuable alternative to PTFs for rapid assessment of SWR and as a tool for SWR mitigation for farmers in South Greenland. The results may well apply to other regions with similar texture and OC ranges, but further testing is required.

Greenlandic fjords contain vast amounts of glacially derived mineral material (glacial rock flour [GRF]), which may be used to amend structureless, low-clay, and water-repellent agricultural soils in South Greenland and elsewhere. In this study, we investigate key physical amendment properties of GRF from 16 different deposits in South Greenland. The clay-sized fraction varied largely (range, 0.11–0.57 kg kg−1), and the particles were mostly angular. The specific surface area (SSA) determined by either ethylene glycol monomethyl ether (EGME, polar liquid) (range, 13.32–88.06 m2 g−1) or water-vapor adsorption (range, 10.62–63.82 m2 g−1) agreed well (r =.90) and were comparable to kaolinitic-clay dominated cultivated soils (KA-soils) with clay content similar to the GRFs. The cation exchange capacities (CECs) (range, 4.25–21.91 cmol kg−1) were similar to or higher than those of the KA-soils. The water content at the permanent wilting point (PWP) for the GRFs were considerably lower than those of the KA-soils. The addition of 5% GRF to a sandy soil from Greenland showed a tendency (although not statistically significant) to increase plant available water (PAW). However, very high GRF addition (10 and 15%) significantly decreased the PAW. The specific surface charge (CEC/SSA) of the GRFs were higher than for comparable KA-soils, suggesting a good soil amendment potential. The results from this study are valuable toward designing sustainable GRF amendment strategies, matching a given cultivated soil with the right amount and type of GRF.

The particle density (ρ s) is a fundamental physical property needed for calculating the soil porosity and phase distributions. While ρ s is often estimated using soil organic matter (SOM) content and particle size distribution, the specific densities of each soil component remain unclear in a subarctic agricultural setting. This study aimed to evaluate the ρ s of soils from Southwest Greenland using a three-compartment model (3CM) based on the mixing ratio of SOM derived from loss-on-ignition, mineral particles –1) and clay content (0.020–0.185 kg kg –1). Despite their high SOM content, the Greenlandic soils exhibited relatively high ρ s (1.936–3.044 Mg m –3), which together with a large SOM/organic carbon ratio of 2.16 indicated a high SOM density of 1.493 Mg m –3. The 3CM fit on all soils indicated FC and CC densities of 3.047 and 2.713 Mg m –3, respectively, while a subset of soils (n = 203) from the same geological setting resulted in FC and CC densities of 2.738 and 2.731 Mg m –3. Prediction accuracy of the 3CM (RMSE = 0.067 Mg m –3) was similar to PTFs (RMSE = 0.068–0.070 Mg m –3) and better than vis–NIR spectroscopic models (RMSE = 0.091 Mg m –3).

Fibre materials are widely used as insulation materials in both clothing and the building industry. The transport of heat and air through fibre insulation materials are accountable for both the energy need for indoor space conditioning and the indoor environment quality inside buildings. A better understanding of the thermodynamics of those materials can enable higher quality products for improved energy efficiency. By using fast gas permeability measurements and more time-consuming guarded hot plate measurements, this study investigates the link between thermal conductivity and gas permeability for Rockwool, Kevlar and polyester fibres, at different compaction levels. Correlations between gas permeability and thermal conductivity at different total volumes of solid are presented. The experimental results show that the gas permeability and thermal conductivity exhibited a change in their evolution trend, due to compaction, in the same zone of the total volume of solid for all materials. The presence of this transition zone enables to establish a link between the measurement of gas permeability and thermal conductivity. This correlation can be employed to perform rapid thermal conductivity assessment of fibrous material, which can be cost-effective for fibre manufacturers or building contractors, but also quality assessment in the textile industry.

Cool road pavements contribute to mitigating urban heat islands. To evaluate the heat balance in paved surfaces and to select appropriate road construction materials that help suppress heat islands, an accurate understanding of heat transport parameters such as thermal conductivity (λ) and heat capacity (HC) is important. Recycled aggregates from construction and demolition waste, including scrap construction materials and industrial by-products, are often used for road construction; however, λ and HC of recycled aggregates especially for roadbeds are not fully understood. This study involved a series of laboratory tests to measure λ and HC of recycled concrete and clay brick aggregates (

Litter decomposition is a critical process in carbon cycling, which can be affected by land use. The relationship between litter decomposition and soil properties under different land uses remains unclear. Litter decomposition can be quantified by the Tea Bag Index (TBI), which includes a decomposition rate k and a stabilization factor S. Our objective was to investigate linkages between TBI and soil physicochemical and gas transport properties and land use. We buried three pairs of tea bags in 20 sites (covering cropland, grassland, heathland, and forest land uses) in a transect from the western to the eastern coast of the Jutland peninsula, Denmark. The tea bags were retrieved after 90 d and TBI was determined. Disturbed and undisturbed (100 cm 3 soil cores) samples were collected from each site. Thereafter, clay content, organic carbon (OC), bulk density (ρ b), pH, electrical conductivity (EC), oxalate-extractable phosphorus (P ox), aluminum (Al ox), and iron (Fe ox) content, soil water content, gas diffusivity (D p/D 0), and air permeability (k a) at −10 kPa were measured. Results showed that grasslands had the highest k and S among four land uses, and agricultural soils (croplands and grasslands) exhibited higher TBI values than seminatural soils (forest and heathland). The prediction of S was better than that of k based on multiple linear regression analysis involving soil physicochemical properties. Clay content and OC were not strong predictors. Including D p/D 0 and k a improved the prediction of S, and finally, the inclusion of land use enhanced the prediction of both k and S. The different trends between two distinct land-use groups can be attributed to pH, P ox, and ρ b.

The rapid warming of the Arctic is changing the conditions for agricultural activity in southwest Greenland markedly, which necessitates studies of the physical properties of the soil resource. Soil water repellency (SWR) is a soil property that changes soil functional behaviour across a soil-specific range in water-content (W). Although SWR occurs worldwide, it has not been studied in sub-arctic pasture and grass fields. Thus, the aim was to examine the prevalence of SWR in South Greenland and to establish pedotransfer functions for SWR on soil properties that are faster to measure than SWR, i.e. soil organic fractions, texture and soil water retention. This study included 145 soil samples from 22 sub-arctic agricultural fields distributed across three areas of South Greenland, with broad distributions in texture (clay: 0.017–0.194 kg kg−1) and organic carbon (OC) (0.009–0.241 kg kg−1) contents. The degree of soil water repellency (SWR) as a function of water content (SWR-W curve) was measured from oven-dry conditions to the water-content at which the soil became hydrophilic (WNON), and total SWR (SWRAREA) was calculated as the integrated trapezoidal area (SWRAREA) of the SWR-W curve. A total of 99% and 98% of the soil samples were water-repellent and extremely water repellent at their maximum SWR, respectively. Among the three soil organic fractions (OC, Loss-on-ignition at 550 °C, and 225 °C (LOI550 and LOI225)), LOI550 was the best predictor of SWRAREA and WNON (both with r2 = 0.93). Multiple linear regressions including clay content increased r2adj to 0.92 and 0.95 with OC and LOI550, respectively. The Campbell-Shiozawa (CS) model was fitted to the soil–water retention curves (pF 3.0–6.9), and the inverse slope (−α−1) of the CS model exhibited a high correlation to both SWRAREA (r2adj of 0.87) and WNON (r2adj of 0.93), thus suggesting that soil water retention governs SWR. Lastly, it was shown that the coefficient of proportionality between OC and both SWRAREA and WNON for these sub-arctic soils coincided with pasture soils from New Zealand.

Soil aeration is a key parameter for sustainable and productive agriculture. The intensification of agricultural activity in Greenland involves land use (LU) and LU change, affecting the soil–air phase. The combined effects of natural compaction (bulk density, ρ b), texture (texture uniformity index; TUI), and LU on the soil–air phase of subarctic soils are not well known. This study aims to identify and compare the main drivers for air-filled porosity (ε) and soil-structure changes within and across sites in Greenland and Denmark. We analyzed comprehensive data sets of ε, relative gas diffusivity D p/D o), and air-permeability (k a) measured on intact soil samples from South Greenland (pasture) and Denmark (cultivated, urban, and forest). The mechanical robustness of the air phase was evaluated by linear models of ε as a function of ρ b (H-model). The ratio of k a to D p/D o served as a soil-structure index (Ω); the latter significantly correlated to TUI. The Greenlandic pasture soils did not show signs of well-developed soil structure (low Ω-values), whereas low H-values suggested the soils were mechanically robust compared to similar-textured cultivated soils. The soil–air characteristic curve (ε vs. pF) was parameterized, and the moisture control parameter was accurately predicted by TUI and LU (R 2 =.95). Overall, the ρ b was found to control the air-phase functions within a field. However, considering changes in ε-levels across different fields, texture, LU, and other environmental factors became statistically more relevant than ρ b. A modeled response surface for changes in ε with soil conditions may, in perspective, be useful for better-predicting gas transport in soil, both within and across fields.

Water repellency (WR) significantly affects the hydraulic behavior of soils. Although WR often is regarded as a phenomenon with implications for dry soils, it is prevalent at water contents (w) exceeding the wilting point water content. Because the measurement of the WR–w relationship is laborious, alternative more time-efficient methods are desirable to estimate parameters of the WR-w curve. Using 32 high organic carbon (OC) soils from Denmark and South Greenland, we characterized the water vapor sorption isotherms (WSIs), investigated the interrelated effects of OC and clay contents on WSIs and the WR–w relationship, and further evaluated if parameters of the WR-w curve may be derived directly from WSIs. The samples exhibited OC and clay contents ranging from 0.014 to 0.369 kg kg–1 and from 0.02 to 0.16 kg kg–1, respectively. The WSIs measured for relative humidity (RH) values between 3 and 93%, were strongly hysteretic, were OC dependent, and could be accurately characterized with the Guggenheim, Anderson, and de Boer model. Further, the WRarea and wnon parameters, derived from WR measured for several w, were well estimated with linear regressions based on OC content and multiple linear regressions based on OC and clay contents. Estimations for WRarea and wnon based on the WSI parameter wm-a were superior to OC and clay content. Finally, we established mathematical expressions that estimate WRarea or wnon from any air-dry w obtained from either the desorption or adsorption isotherms between 10 and 90% RH.

The hysteretic behaviour of the dry region (2 = 0.92), except for the kaolinite-rich samples (R2 = 0.35). The SOC-rich samples that exhibited illitic clay mineralogy and similar soil texture showed a significant increase in average hysteresis with increasing organic carbon content (R2 = 0.93). For all soil samples combined, the CEC was the strongest indicator for the magnitude of water vapour sorption hysteresis. Highlights: A new index for quantification of soil vapour sorption hysteresis was proposed Large SOC and clay content increased sorption hysteresis For soil samples, dominant clay mineralogy controlled the magnitude of hysteresis Cation exchange capacity was the best predictor of hysteresis for all soil types.

Low-Voltage Mineral Deposition technology (LVMD), widely known as Biorock, has previously been suggested as support for coral reef restoration, as hypothesized high porosity, wide pore-size distribution and connectivity, and good strength properties may facilitate biological functions (for example larvae settlement) and durability. In this technology, very low voltage induces an electrical current that initiates precipitation and accretion of hard minerals (aragonite and calcite) on a metal in seawater. This technology has been discussed mainly for its biological value, while this paper wants to highlight also its engineering value as artificial reef material. Indeed, some of the properties that makes it valuable in one domain are also supporting its use in the other. Because the metal on which the precipitation takes place can be of any shape and size, so can the artificial reef and its mechanical strength characteristics are above the ones of corals and similar to concrete, indicating adequate durability. Coral and boulder reefs suffering from degradation have severe implications on biodiversity, protection from flooding, and cultural value and therefore understanding how to persevere and re-establish these ecosystems is central for sustainable intervention in the marine environment. By comparing chemical-physical characteristics of Coral Porites Exoskeleton (CPE), one typical reef building coral type, LVMD and High-Voltage Mineral Deposition (HVMD), we show that they possess highly similar properties including chemical composition, density, total porosity, pore-size distribution, physical and chemical heterogeneity, total and external surface areas, and comparable mechanical strength.

The ever-increasing global demand for concrete engenders concerning sustainability issues. In addition to the large CO2 emissions induced by the production of cement, the fabrication of concrete requires important mining and excavation for the extraction of specific minerals, sand, and aggregates, which can endanger local ecosystems. Seacrete (also known as “Seament” or “Biorock”) has previously been suggested as a potential alternative to traditional cementitious materials. Seacrete is artificial electrolytically precipitated calcium carbonate around a steel-frame cathode in which electrical current flows and that is submerged in seawater. Previous studies showed that it is ideal for the restoration of coral reefs and marine ecosystems. Furthermore, Seacrete is a very interesting sustainable concrete-like construction material for buildings and other human infrastructures. Indeed, it can be produced nearby all coastlines without any need for mining, extraction or transportation of additional material. In addition, the fabrication of Seacrete can easily be powered by low-intensity or local intermittent renewable energy sources. Previous publications pointed out that the mechanical properties and strength of Seacrete are similar to that of concrete, but no investigation has been conducted on other properties. For the first time, the current experimental study assesses the thermal and moisture properties of Seacrete. This article reports the density, compression strength, puncture resistance, specific heat capacity, thermal diffusivity, thermal conductivity, and water vapour sorption isotherms of two types of Seacrete, namely low-voltage and high-voltage Seacrete. Finally, this study emphasizes that all the aforementioned material properties of Seacrete are similar to that of concrete, confirming that the former can be considered for the construction of certain building elements and infrastructures.

A number of environmental, agronomic and engineering applications require knowledge of the Atterberg limits (liquid limit, LL; plastic limit, PL) and the plasticity index, PI of soils. The tedious and costly nature of standard experimental methods, as well as challenges with measurement repeatability motivated the development of regressions as well as more sophisticated techniques to estimate the Atterberg limits from other properties such as clay content, cation exchange capacity (CEC), and soil specific surface area. The amount of water adsorbed to particle surfaces at relative humidity (RH) < 95% is intimately linked to these soil properties, which suggests that hygroscopic water content (wh) may be a better predictor of the Atterberg limits. The present study (i) proposes regression models that estimate the LL, PL, and PI from wh at different relative humidity values ranging from 10 to 90% and considering water sorption hysteresis, and (ii) compares the performance of the models to other models that comprise clay, silt and organic carbon contents and CEC. For model development, wh was measured by water adsorption and desorption for 168 soil samples that varied widely in terms of geographic origin, clay mineralogy, and soil organic carbon content. The LL and PL were determined with the drop cone penetrometer and rolling device, respectively. Regression models were developed for both sorption directions for nine RH values between 10 and 90%. For 44 independent soil samples, the models estimated LL, PL and PI accurately (e.g., for desorption wh measured at 90% RH, RMSE and r2 values were 6.43% & 0.89; 3.95% & 0.83 and 6.69% & 0.79, respectively). There was no clear effect of sorption direction on the estimation accuracy. The wh determined at higher RH tended to better estimate the Atterberg limits compared to that measured at lower RH. The wh models were superior in estimating LL and PL compared to models that were based on clay content and organic carbon or CEC. For the PI, the models based on CEC performed slightly better than the wh models. Thus, a single measure of wh can provide reliable estimates of the Atterberg limits and PI.

The reduction of permafrost areas and a prolonged vegetation period, both due to the ongoing climate change, open up new possibilities for agricultural activities in the circumpolar region. Presently, not much is known about the physical and functional properties of subarctic agricultural soils, making it challenging to evaluate soil impacts from increased agricultural activity. This study aims at assessing the mechanical properties of sandy Greenlandic pasture soils regarding a potential future land-use change. The compression curves of 210 undisturbed soil core samples of three pasture fields in South Greenland and, as comparison, four intensively cultivated agricultural fields in Denmark were generated by uniaxial confined compression tests (UCCT). Four soil mechanical properties were determined: the precompression stress ( σ pc ) as a measure of soil strength, the compression index ( C c ) as a measure of compressibility, the swelling index ( C s ) as a measure of resilience to compaction and the rebound ( Δ e ) after a relaxation time of 60 s as a measure of short-time recovery from compaction. The Greenlandic pasture soils exhibited significantly higher σ pc than the Danish cultivated soils despite their significantly lower initial bulk density, ρ b . The C c negatively correlated with ρ b , and the Greenlandic soils showed higher C c values than the Danish soils. The C s showed a reciprocal correlation with ρ b and, partly due to lower ρ b of the Greenlandic soils, higher C s than the Danish soils. The South Greenlandic sandy pasture soils showed compression and rebound characteristics on level with Danish loamy cultivated soils, likely due to a high content of particulate organic matter (non-degraded organic matter, including grass root-mat residues).

The Arctic is warming at twice the global average, which may impact agricultural production in Greenland. Therefore knowledge of the functional properties of Greenlandic soil resources is necessary. The relative soil gas diffusivity [the soil gas diffusion coefficient (Dp)–free-air diffusion coefficient (Do) ratio] is the chief parameter controlling gas transport in soils. Predictions of Dp/Do are needed to estimate root zone aeration and terrestrial greenhouse gas fluxes. We used existing models to analyze the Dp/Do of soils from Greenlandic fields and a pore connectivity index (Cip) to infer their degree of structural development and identify the main parameters controlling Dp/Do. In total, 201 × 3 intact 100-cm3 soil samples were sampled across six fields with clay and organic C contents of 0.016 to 0.089 and 0.016 to 0.105 kg kg−1, respectively. The Dp/Do was measured with the one-chamber nonsteady-state method at soil water potentials between –10 and –1,000 cm H2O. Accurate determination of total porosity (Φ) was ensured by calibrating a particle density model on 129 samples. The soils exhibited a less developed structure and highly tortuous pore networks, resulting in low Dp/Do as a function of air-filled porosity (ε). Density-corrected models with air saturation (ε/Φ) reduced the RMSE. Furthermore, Cip at –1,000 cm H2O soil water potential increased linearly with dry bulk density (ρb), suggesting that ρb is a key controller of Dp/Do, which is important for planning cultivation practices for Southern Greenlandic soils. Lastly, we found that an air saturation >35% is required for adequate soil aeration.

The soil water retention curve (SWRC) at the wet part is important for understanding and modeling the water flow and solute transport in the vadose zone. However, direct measurements of SWRC is often laborious and time consuming processes. The Campbell function is a simple method to fit the measured data. The parameters of the Campbell function have been recently proven that can be predicted using visible-near-infrared spectroscopy. However, predicting the SWRC using image spectral data could be an inexpensive and fast method. In this study, 100-cm3 soil samples from Denmark were included and the soil water content was measured at a soil-water matric potential from pF 1 [log(10)= pF 1] up to pF 3. The anchored Campbell soil-water retention function was selected instead of the original. Specifically, in this function the equation is anchored at the soil-water content at pF 3 (θpF3) instead at the saturated water content. The image spectral data were correlated with the Campbell parameters [θpF3, and the pore size distribution index (Campbell b). The results showed the potential of remote sensing to be used as a fast and alternative method for predicting the SWRC in a large-scale.

The soil specific surface area (SSA) is a fundamental property governing a range of soil processes relevant to engineering, environmental, and agricultural applications. A method for SSA determination based on a combination of visible near-infrared spectroscopy (vis-NIRS) and vapor sorption isotherm measurements was proposed. Two models for water vapor sorption isotherms (WSIs) were used: the Tuller–Or (TO) and the Guggenheim–Anderson–de Boer (GAB) model. They were parameterized with sorption isotherm measurements and applied for SSA estimation for a wide range of soils (N = 270) from 27 countries. The generated vis-NIRS models were compared with models where the SSA was determined with the ethylene glycol monoethyl ether (EGME) method. Different regression techniques were tested and included partial least squares (PLS), support vector machines (SVM), and artificial neural networks (ANN). The effect of dataset subdivision based on EGME values on model performance was also tested. Successful calibration models for SSATO and SSAGAB were generated and were nearly identical to that of SSAEGME. The performance of models was dependent on the range and variation in SSA values. However, the comparison using selected validation samples indicated no significant differences in the estimated SSATO, SSAGAB, and SSAEGME, with an average standardized RMSE (SRMSE = RMSE/range) of 0.07, 0.06 and 0.07, respectively. Small differences among the regression techniques were found, yet SVM performed best. The results of this study indicate that the combination of vis-NIRS with the WSI as a reference technique for vis-NIRS models provides SSA estimations akin to the EGME method.

In recent years, research has identified some bio-based, porous building materials as good or excellent regulators of moisture in buildings. The ability of a material to absorb, release and store moisture is described by vapour sorption isotherms. It is necessary input to simulations of indoor environmental parameters in regards to human comfort, and nowadays it can be determined by a number of laboratory experiments, each of which characterized by specific specimen size, equilibration time and methodology. The purpose of this study is to experimentally derive isotherms for three bio-based, porous building materials by a standardized testing method, using saturated salt solutions. Furthermore, results from the standard method are compared to values of moisture content for the same materials, obtained by air-drying at different relative humidity. This is done with the aim to compare the findings from the two methods with respect to time and repeatability of the results. Derived isotherms are further used as direct input in the building simulation software BSim, which is capable of predicting indoor environment parameters by solving coupled, transient heat and moisture transport equations using finite volume method discretization. Indoor air relative humidity and moisture content distribution in the construction are compared for the experimented materials and conventional building materials. Results show better agreement between isotherms obtained by standard method and air-drying for low density materials. Simulation results suggest that bio-based, highly porous building materials are comparable to conventional building materials in respect to air relative humidity variations, compared to conventional building materials.

The particle-size curve (PSC) defines the continuous size distribution of mineral particles

Rainfall simulators can enhance our understanding of the hydrologic processes affecting the total runoff to urban drainage systems. This knowledge can be used to improve urban drainage designs. In this study, a rainfall simulator is developed to simulate rainfall on urban green surfaces. The rainfall simulator is controlled by a microcomputer programmed to replicate the temporal variations in rainfall intensity of both historical and synthetic rainfall events with constant rainfall intensity on an area of 1 m². The performance of the rainfall simulator is tested under laboratory conditions with regard to spatial uniformity of the rainfall, the kinetic energy of the raindrops, and the ability to replicate historical and synthetic rainfall events with temporally varying intensity. The rainfall simulator is applied in the field to evaluate its functionality under field conditions and the influence of wind on simulated rainfall. Finally, a field study is carried out on the relationship between runoff, soil volumetric water content, and surface slope. Performance and field tests show that the simulated rainfall has a uniform spatial distribution, whereas the kinetic energy of the raindrops is slightly higher than that of other comparable rainfall simulators. The rainfall simulator performs best in low wind speed conditions. The simulator performs well in replicating historical and synthetic rainfall events by matching both intensity variations and accumulated rainfall depth. The field study shows good correlation between rainfall, runoff, infiltration, soil water content, and surface slope.

International audience; Groundwater is essential for the Earth biosphere but is often contaminated by harmful chemical compounds due to both anthropogenic and natural causes. A key factor controlling the fate of harmful chemicals in groundwater is the reduction/oxidation (redox) conditions. The formation factors for the groundwater redox conditions are insufficiently understood. In this study, long-term groundwater quality beneath one of the world megacities was monitored and evaluated. We measured and compared hydrogeochemical conditions including groundwater quality (35 chemical parameters) and redox conditions of five aquifers in the Arakawa Lowland and Musashino Upland, southern Kanto Plain of the Tokyo Metropolitan area, Japan. Monitoring results suggested the following: The main origin of groundwater is precipitation in both the Lowland and Upland areas. The three aquifers in the Arakawa Lowland are likely fully separated, with one unconfined and two confined aquifers under iron reducing and methanogenic conditions, respectively. Oppositely, in the Musashino Upland, the water masses in the two aquifers are likely partly connected, under aerobic conditions, and undergoing the same groundwater recharge and flow processes under similar hydrogeological conditions. The different groundwater redox conditions observed are likely caused by the very different groundwater residence times for the Arakawa Lowland and Musashino Upland.

Standard measurement methods for soil clay content, including the hydrometer and pipette methods, are laborious and difficult to repeat. This has motivated the application of proxy methods such as estimation of clay content from soil water vapor sorption isotherms. Previous studies have revealed that vapor sorption-based clay estimates are inaccurate for soils dominated by swelling or highly weathered non-swelling clays such as kaolinite. In this study, we evaluate an existing vapor sorption-based clay estimation model for soils dominated by either illite (IL), smectite (SM), or kaolinite (KA) clay minerals, and propose modifications to account for high SM and KA contents. Compared to the pipette method, the clay content obtained from the existing water sorption model at 50% relative humidity (RH) was accurate for the IL samples, but significantly overestimated (RMSE = 23.7%; ME = 19.7%) or underestimated (RMSE = 28.8%; ME = −17.0%) clay content for SM and KA rich soils, respectively. The proposed modification involves correcting the estimated clay content with a “slope factor”, S for RH values ranging from 30 to 90% for both adsorption and desorption. For SM samples, S averaged 0.76 and 0.72 for adsorption and desorption, respectively, and for KA samples, S ranged from 2.26 to 1.19 and followed a polynomial relationship with RH. Comparison of the estimated clay content from the modified models showed markedly improved estimation of the measured clay content (for RH of 90%, RMSE = 8.0%; ME = 2.6% for SM samples and RMSE = 9.6%; ME = −5.7% for KA samples).

Rainfall-runoff-generating mechanisms in urban green areas are scarcely understood, and limited knowledge and data on rainfall-runoff processes are available. Therefore, a large-scale experimental field station was established to investigate the inherent hydrological processes of a grass-covered 4,300 m2 urban catchment consisting of sandy loam soil. A facility to collect surface runoff from the area was designed. Runoff, soil moisture properties, and rainfall were measured simultaneously by a flow meter, in-ground soil sensors, and rain gauges, respectively. Measured soil volumetric water content was above 0.34 m3 H2O m−3 soil during fall and winter and ranging between 0.13 and 0.34 m3 H2O m−3 soil during late spring and summer. Measured runoff recorded from September 2016 until July 2018 strongly indicates that subsurface throughflow was the dominant runoff type. There was good correlation between the dynamics of soil water content and runoff. Accumulated rainfall and runoff was linearly correlated for soil volumetric water contents above 0.34 m3 H2O m−3 soil. The relationship between runoff and rainfall shows a runoff coefficient of 0.18 for the 4,300 m2 area.

Organic matter can render soil hydrophobic and cause soil water repellency (SWR) which has large implications for agriculture. Consequences such as fingered flow, uneven wetting patterns, and increased overland flow reduce irrigation efficiency and plant nutrient availability. The phenomenon of SWR is a transient soil property depending, inter alia, on soil water content (w). Soil can exhibit SWR from oven-dry w until the critical w where it again becomes fully wettable (wNON). The total SWR can be obtained from the nonlinear SWR-w relationship as the integrated trapezoidal area under the SWR-w curve (SWRAREA). We analyzed 78 soil samples, representing five dominant soil orders in the South Island of New Zealand. The soils had a large range in clay (0.000–0.520 kg kg−1) and organic carbon (OC) content (0.021–0.217 kg kg−1). The degree of SWR was measured on soils at air-dry conditions (SWRAD) and after heat-pretreatment at 60 (SWR60) and 105°C (SWR105). Further, SWR was measured in small w increments above air-dry w until wNON was reached. The SWR-w curves were either unimodal or bimodal, or no SWR occurred. SWRAREA ranged from 0.16 to 26.82 mN m−1 kg kg−1. Among the five soil orders tested, the Podzols exhibited the highest severity in SWR, whereas the Semiarid soils were the least hydrophobic soils. In conclusion, OC was the main factor for controlling the severity of SWR. Though, pH also had minor effects on SWR. Further, an upper limit critical water content was derived from the simple relationship between the wNON and OC, which could be applied to improve irrigation practices of pastoral soils. However, there is a need for further testing on different soils and land uses.

The average particle density (r d ) is a fundamental soil property, used for calculating the total porosity. Traditional r d measurement by pycnometer method is tedious and time-consuming. In this study, visible–near-infrared (vis–NIR) spectroscopy and a simple two-compartment linear and curvilinear pedotransfer function only requiring knowledge of soil organic matter content (OM) were tested and compared as alternative, indirect, rapid, and cost-effective methods. Soil r d was measured by water pycnometer on 179 soils representing a wide range of OM (0.002–0.767 kg kg -1 ), whereas soil spectra were measured on air-dry samples by vis–NIR spectroscopy. The r d models were developed using partial least squares regression with leave-one-out-cross-validation using vis–NIR spectral data, and a simple two-compartment pedotransfer function, r d = A(OM) + B(1 − OM) using the OM content. Predictive abilities of these two methods were tested using three different datasets: (i) minerals soils (OM < 0.1 kg kg -1 ), (ii) organic soils (OM > 0.1 kg kg -1 ), and (iii) all soils. Calibrating the two-compartment pedotransfer function for the entire dataset gave expected values for the individual particle densities of OM (A = 1.244 g cm -3 ) and mineral particles (B = 2.615 g cm -3 ). The vis–NIR spectroscopy model successfully predicted soil r d for the entire dataset (R 2 = 0.87, RMSECV = 0.10 g cm -3 ), with a poorer performance than the two-compartment linear model (R 2 = 0.96, RMSE = 0.06 g cm -3 ). using only the mineral soils data did not suffice to obtain realistic and accurate vis–NIR spectroscopy (R 2 = 0.62, RMSECV = 0.02 g cm -3 ) or OM based (R 2 = 0.80, RMSE = 0.02 g cm -3 ) models for r d , illustrating the importance of the wide range of OM content considered in the present study.

The severity of soil water repellency (SWR) varies nonlinearly with water content (w), and it is extremely laborious to obtain complete SWR-w curves, which are needed to predict the occurrence of SWR. In this study, we combined a three-parameter moisture-dependent SWR (MD-SWR) model with visible near-infrared spectroscopy (vis-NIRS) as a fast and novel method to estimate the SWR-w curve. The method was applied to a data set of SWR-w curves determined for 71 soil samples (organic carbon [OC] content: 0.021–0.147 kg kg-1, clay: 0.000–0.520 kg kg-1). The degree of SWR was measured on air-dried soil samples (SWRAD) and on soil samples with increasing water contents until the water content at which the soils became wettable (wNON) was reached. The three-parameter MD-SWR model was fitted to the measured SWR-w curves between the water content at air-dry conditions (wAD) and wNON. The total SWR was then calculated as the trapezoidal integrated area underneath the SWR-w curves (SWRAREA). Air-dried soil samples were scanned with a vis-NIR spectrometer. Each of the three MD-SWR model parameters was correlated to vis-NIRS spectra using partial least squares regression. The SWRAREA was predicted using two approaches. For Approach I, the SWRAREA calculated from the MD-SWR model was predicted with a single vis-NIRS model. Approach II utilized predicted MD-SWR model parameter values to obtain vis-NIRS-predicted SWR-w curves between wAD and wNON, and the SWRAREA was calculated from these curves. Results show that vis-NIRS can predict the shape of the SWR-w curves as well as the SWRAREA (R2 = 0.58 and 0.56 for Approach I and II, respectively) across a highly variable dataset from a single vis-NIRS scanning and one SWR measurement at air-dried conditions.

The soil-water retention curve (SWRC) at the dry end, also known as soil water vapor sorption isotherms, is essential for the modeling of water vapor transport, microbial activity, and biological processes such as plant water uptake in the vadose zone. Measurement of detailed soil water vapor sorption isotherms (WSIs) can be time consuming. Therefore, we propose rapid, inexpensive methodologies (visible-near-infrared spectroscopy [vis-NIRS] and a pedotransfer function [PTF]) to predict the Campbell-Shiozawa (CS) model parameters to obtain the WSIs. Water vapor sorption isotherms were measured on 144 soil samples with a vapor sorption analyzer. The CS semi-logarithmic-linear function anchored at a soil-water matric potential of -106 cm H2O (log|-106| = pF 6) was fitted to the measured data because it accurately characterizes the WSIs. Thereafter, a vis- NIRS calibration model and a PTF, based on clay and organic C contents, were developed and used to predict the two reference CS model parameters (a and W6). Both parameters were predicted with a reasonable degree of accuracy using vis-NIRS and the PTF (for α, RMSE values of 0.0041 and 0.0025, and for W6, RMSE values of 0.0042 and 0.0034 for vis-NIRS and the PTF, respectively). Based on the predicted a and W6 values, the predicted WSIs compared closely with the measured isotherms for individual soil samples from each field. At the field scale, the vis-NIRS model performed marginally better than the PTF. Thus, it is evident that the use of vis-NIRS or PTFs provides a relatively inexpensive approach to predicting soil water sorption isotherms.

Glyphosate [N-(phosphonomethyl) glycine] is the active ingredient in Roundup, which is the most used herbicide around the world. It is a non-selective herbicide with carboxyl, amino, and phosphonate functional groups, and it has a strong affinity to the soil mineral fraction. Sorption plays a major role for the fate and transport of glyphosate in the environment. The sorption coefficient (Kd) of glyphosate, and hence its mobility, varies greatly among different soil types. Determining Kd is laborious and requires the use of wet chemistry. In this study, we aimed to estimate Kd using basic soil properties, and visible near-infrared spectroscopy (vis–NIRS). The latter method is fast, requires no chemicals, and several soil properties can be estimated from the same spectrum. The data set included 68 topsoil samples collected across the South Island of New Zealand, with clay and organic carbon (OC) contents ranging from 0.001 to 0.520 kg kg−1 and 0.021 to 0.217 kg kg−1, respectively. The Kd was determined with batch equilibration sorption experiments and ranged from 13 to 3810 L kg−1. The visible near-infrared spectra were obtained from 400 to 2500 nm. Multiple linear regression was used to correlate Kd to oxalate extractable aluminium and phosphorous and pH, which resulted in an R2 of 0.89 and an RMSE of 259.59 L kg−1. Further, interval partial least squares regression with ten-fold cross-validation was used to predict Kd by vis–NIRS, and an R2 of 0.93 and an RMSECV of 207.58 L kg−1 were obtained. Thus, these results show that both basic soil properties and vis–NIRS can predict the variation in Kd across these samples with high accuracy and hence, that glyphosate sorption to a soil can be determined with vis–NIRS.

Estimation of soil hydraulic parameters is essential when generating a hydrogeological model for simulating water flow dynamics in an agricultural field. However, estimation of the input parameters through direct measurements is time consuming and costly, and the spatial variability presents an uncertainty. Therefore, we proposed a rapid and inexpensive concept (integration of visible-near-infrared spectroscopy [vis-NIR] and a pedotransfer function [PTF]) to estimate hydraulic properties considering catchment scale. An existing vis-NIR-predicted Campbell retention function was used for estimating the Campbell b parameter and the water content at -1000 cm H 2 O soil-water matric potential (log|-1000| = pF 3). A PTF was developed for predicting the saturated hydraulic conductivities using the vis-NIR-predicted Campbell b and the effective porosity, defined as the difference in volumetric water contents at pF 0.3 and 3. The concept was evaluated by developing a hydrogeological model in HYDRUS-2D software for simulating the tile drainage discharge from a clayey agricultural subcatchment in Denmark, using as input hydraulic parameters the output from the suggested approach. The suggested approach simulated the main attributes of the flow hydrograph with a reasonable degree of accuracy (R2 and RMSE values of 0.86 and 1.25 L s -1 , respectively). A sensitivity analysis was performed to determine the response of the model to changes in values of predicted parameters when predicting the drainage discharge, and it showed that small variations (

Knowledge of the cation exchange capacity (CEC) for soils or other porous media is very important for civil engineering and agricultural applications. However, the standard laboratory methods to measure CEC are costly and laborious. The aim of this research was to develop a visible–near-infrared spectroscopy (Vis–NIRS, 400–2500 nm) calibration model to predict CEC based on multivariate analysis and to compare the predictive ability of Vis–NIRS with that of a pedotransfer function (PTF). For this purpose, reference CEC was measured by the ammonium acetate method for 235 soil samples, collected from 21 countries. Diffuse spectral reflectance data were also collected by using a NIRSTM DS2500 spectrometer. The model was constructed on a calibration subset (80%) and evaluated with a validation subset (20%) using partial least squares regression. The Vis–NIRS calibration model was sufficiently robust based on the cross-validation results [R2 = 0.79, RMSE of cross-validation values of 7.9 cmolc kg−1 and bias = −0.14]. The independent validation of the Vis–NIRS model showed good prediction accuracy, regardless of sample origin (RMSE of prediction value of 5.0 cmolc kg−1 and ratio of performance to interquartile distance value of 4.5). Moreover, the Vis–NIRS prediction performance was superior to that of the PTF, which was influenced by the sample origin (RMSE values of 11.5 cmolc kg−1). The better prediction of CEC by the Vis–NIRS calibration model suggests that it is due to the co-variation of CEC with clay (type and content) and organic C content.

The hysteretic behaviour of the dry region of the soil water characteristic, which is of essence for accurate characterization and modelling of bio-physicochemical soil processes under dry conditions, is well documented. However, knowledge about how to best quantify water vapour sorption hysteresis and about the effects of soil properties on hysteresis is limited. To overcome this knowledge gap, we proposed an index (average hysteresis) for quantifying sorption hysteresis and evaluated its applicability based on measured sorption isotherms of four source clay minerals and 155 soil samples. Furthermore, the effects of clay mineralogy, clay content, soil organic carbon, and cation exchange capacity (CEC) on the magnitude of sorption hysteresis were investigated. For the clay minerals, kaolinite did not exhibit hysteretic behaviour, illite, and Ca-smectite showed some hysteresis, while Na-smectite was strongly hysteretic. For the soil samples, the average hysteresis increased with increasing clay content for the different clay mineral groups, and with increasing organic carbon content (R2 = 0.93) for similarly textured soil samples. The average hysteresis, corrected for clay content, was strongly affected by the dominant clay mineralogy. Regardless of the dominant clay mineralogy, clay content or organic matter content, the CEC was a good predictor of the average hysteresis for all the soil samples.

Mass transport in soil occurs through the soil pore network, which is highly influenced by pore structural parameters such as pore-size distribution, porosity, pore tortuosity, and coordination number. In this study, we visualised the networks of meso- and macro-pores (typical pore radius r ≥ 10 μm) using microfocus X-ray computed tomography (MFXCT) and evaluated pore structural parameters of two loamy soils from Japan and New Zealand packed at different degrees of compaction. The effect of compaction on pore structural parameters and relationships between pore structural parameters and measured mass transport parameters were examined. Results showed a clear influence of compaction on pore structural parameters, with the MFXCT-derived mean pore radii and pore tortuosities decreasing and the mean pore coordination number increasing with increasing dry bulk density. Especially, pores with r > 80 µm became finer or were not well formed due to compaction. The MFXCT-derived pore structural parameters were not well correlated with the equivalent pore radii from measured water retention curves. However, volumetric surface areas and pore-network connectivity-tortuosity factors derived from MFXCT allowed a fair prediction of several important mass transport parameters such as saturated hydraulic conductivities, soil-gas diffusion coefficients, and soil-air permeabilities. Further studies are needed to link micro-pores with radii smaller than the X-ray CT resolution to meso- and macro-pores visualised by X-ray CT to improve the prediction of mass transport parameters in soil.

A transient flow experiment using automated drip infiltrometers (ADIs) was performed on soil columns (about 6 dm3) large enough to incorporate macropore flow effects. We investigated to what extent the estimated soil hydraulic parameters obtained from inverse modeling of these experiments are reliable. A machine learning based pedotransfer function (PTF) for prediction of water content at −1, −10, and −158 m pressure head was developed. Sensitivity analysis of the van Genuchten parameters (residual and saturated water content qr and qs, fitting parameters α, n, and l, and saturated hydraulic conductivity Ks) in soils of sandy, silty, and clayey textures showed that the temporal variation of pressure heads in ADI scenarios was not sensitive to qr and qs. The other parameters were accurately estimated from numerically synthesized data. The uniqueness of the estimated parameters did not change when a bias, representing experimental error, was added to the data set. In actual columns, using the temporal and spatial pressure head data from the ADIs and the water contents in the drier range predicted by the developed PTF resulted in a precise estimation of the van Genuchten parameters. Not including the PTF water contents resulted in non-uniquely estimated van Genuchten parameters.

The soil water retention curve (SWRC) is the most fundamental soil hydraulic function required for modelling soil–plant–atmospheric water flow and transport processes. The SWRC is intimately linked to the distribution of the size of pores, the composition of the solid phase and the soil specific surface area. Detailed measurement of the SWRC is impractical in many cases because of the excessively long equilibration times inherent to most standard methods, especially for fine textured soil. Consequently, it is more efficient to predict the SWRC based on easy-to-measure basic soil properties. In this research we evaluated a new two-stage approach developed recently to predict the SWRC based on measurements for disturbed repacked soil samples. Our study involved undisturbed structured soil and took into account the effects of bulk density, organic matter content and particle-size distribution. Independently measured SWRCs for 171 undisturbed soil samples with organic matter contents that ranged from 3 to 14% were used for model validation. The results indicate that consideration of the silt and organic matter fractions, in addition to the clay fraction, improved predictions for the dry-end SWRC. The dry-end results revealed that the smallest matric potential at hypothetical ‘zero-water-content’ varies between −45 000 and −125 000 m (pF 6.65–7.1) even for soils with similar clay mineralogy. The sensitivity analysis of the two-stage approach indicated that predicted SWRC results are more sensitive to bulk density than to organic matter content or soil texture. For the soils studied, the two-stage approach showed reasonable agreement with measured data, with a root mean square error of 0.04 cm3 cm−3 for the matric potential range from pF 1 to pF 6.6. Highlights Is a new approach to modelling the soil water retention (SWR) curve applicable to structured soil? The model accurately predicts the full SWR curve with an RMSE of 0.04 cm3 cm−3. Prediction accuracy of the wet part of the SWR curve was sensitive to variation in bulk density. The pF at zero water content, which affects the prediction of dry SWR, ranged from 6.65 to 7.10.

Solute transport through the soil matrix is non-uniform and greatly affected by soil texture, soil structure, and macropore networks. Attempts have been made in previous studies to use infiltration experiments to identify the degree of preferential flow, but these attempts have often been based on small datasets or data collected from literature with differing initial and boundary conditions. This study examined the relationship between tracer breakthrough characteristics, soil hydraulic properties, and basic soil properties. From six agricultural fields in Denmark, 193 intact surface soil columns 20 cm in height and 20 cm in diameter were collected. The soils exhibited a wide range in texture, with clay and organic carbon (OC) contents ranging from 0.03 to 0.41 and 0.01 to 0.08 kg kg − 1 , respectively. All experiments were carried out under the same initial and boundary conditions using tritium as a conservative tracer. The breakthrough characteristics ranged from being near normally distributed to gradually skewed to the right along with an increase in the content of the mineral fines (particles ≤ 50 μm). The results showed that the mineral fines content was strongly correlated to functional soil structure and the derived tracer breakthrough curves (BTCs), whereas the OC content appeared less important for the shape of the BTC. Organic carbon was believed to support the stability of the soil structure rather than the actual formation of macropores causing preferential flow. The arrival times of 5% and up to 50% of the tracer mass were found to be strongly correlated with volumetric fines content. Predicted tracer concentration breakthrough points as a function of time up to 50% of applied tracer mass could be well fitted to an analytical solution to the classical advection-dispersion equation. Both cumulative tracer mass and concentration as a function of time were well predicted from the simple inputs of bulk density, clay and silt contents, and applied tracer mass. The new concept seems promising as a platform towards more accurate proxy functions for dissolved contaminant transport in intact soil.