Surface Crust Research Articles

Composition of Modern Dust and Holocene Aeolian Sediments in Archaeological Structures of the Southern Levant

Archaeological structures are often filled with sediments and may serve as effective dust traps. The physical parameters and chemical composition of archaeological soils in hilltop ruins, ancient runoff-collecting terraces, and cleanout spoils of cisterns were determined in the Petra region in southern Jordan and the Northern Negev in Israel. Different types of ruins are characterized by certain soil structures, but could not be distinguished with regard to substrate composition. This reflects a predominance of aeolian processes for primary sedimentation, while fluvial processes seem to only re-distribute aeolian material. In the Petra region, the physical and chemical properties of all archaeological soils show a significant local contribution from associated weathered rocks. Compared to modern settled dust, archaeological soils in Southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This seems connected with preferential fixation of silt and clay by surface crusts, and a role of moisture in sedimentation processes as calcareous silt was found to be deposited in greater amounts when associated with precipitation. In contrast, the contribution of rocks is negligible in the Negev due to greater rock hardness and abundant biological crusts that seal surfaces. Archaeological soils in the Negev are chemically similar to current settled dust, which consists of complex mixtures of local and remote sources, including significant portions of recycled material from paleosols. Archaeological soils are archives of Holocene dust sources and aeolian sedimentation processes, with accretion rates exceeding those of Pleistocene hilltop loess in the Negev. Comparison with Pleistocene paleosols suggests that dust sources did not change significantly, but disappearance of snow could have reduced dust accumulation during the Holocene.

Mineralogical and geochemical studies of secondary mineral assemblages related to deterioration of building materials

The study was aimed at mineralogical and geochemical characteristics of secondary phases related to deterioration of historic building materials. The investigations, carried out in the Holy Trinity Basilica in Krakow, Poland, focused on the southern facade of the 17th-century Myszkowskis Chapel, built of the Miocene Pinczow limestone. Lower part of the facade is covered with a cement render, and the exposed foundations are made of Jurassic limestone and Cretaceous sandstone, both of local origin from the Krakow region and neighbouring Carpathians, in the form of irregular blocks bound with a cement mortar. The wall surface exhibits clear signs of damage; from dark grey soiling and scaling to efflorescences. Sampled materials, deteriorated, altered crusts and efflorescences were analysed with optical and scanning electron microscopy, X-ray diffraction, and Raman microspectroscopy methods. The secondary minerals distinguished include abundant gypsum CaSO 4 ·2H 2 O, less common thenardite Na 2 SO 4 (and/or mirabilite Na 2 SO 4 ·10H 2 O), aphthitalite (K, Na) 3 Na(SO 4 ) 2 , darapskite Na 3 (SO 4 )(NO 3 )·H 2 O, ettringite Ca 6 Al 2 (SO 4 ) 3 (OH) 12 ·26H 2 O, monosulphite Ca 4 Al 2 O 6 SO 3 ·11H 2 O, as well as scarce nitre KNO 3 , nitratine NaNO3 and halite NaCl. Gypsum usually forms surface crusts and fills the pores inside some materials. The efflorescences, sampled from the exposed foundations, consisted of thenardite and/or mirabilite, aphthitalite and darapskite, whereas ettringite and monosulphite were connected with cement renders. Traces of nitre, nitratine and halite were detected at various elements of the chapel facade and foundations. The origin of the salts is related to composition and physicochemical properties of the building materials, as well as to anthropogenic factors.

Prediction of soil wind erodibility using a hybrid Genetic algorithm – Artificial neural network method

Understanding and consequent modeling of soil wind erodibility is hampered by the complex nature of the eroding processes and limited empirical data. It is often necessary to resort to robust approaches capable of finding correlated patterns among soil erodibility magnitudes and their drivers. To signify soil erodibility to wind, we used a portable wind tunnel to measure wind erosion rate (g m−2 s−1) at a total of 118 sites in Kerman Province, southeast Iran. At each sampling site, 17 different factors affecting soil erodibility were measured. Gravel coverage, surface crust, very fine and very coarse sands, aggregate stability, and calcium carbonate equivalent (CCE) were introduced as the more important parameters affecting soil erodibility by hybrid Genetic Algorithm-Artificial Neural Network (GA-ANN). A Multi-Layer Perception (MLP) neural network was developed to predict erodibility changes in response to spatial variation of the selected features. The developed MLP-model provided a strong basis for the prediction of soil erodibility, where the coefficient of determination (R2) values of 0.89 and 0.87 were obtained by comparing the measured and predicted wind erosion rates for the training and testing data, respectively. The acceptable levels of the statistical validation criteria were also an indication of the proper performance of the model. Furthermore, the soil erodibility was sensitive respectively to surface crust, very fine sand, and very coarse sand parameters.

Induced biological soil crust controls on wind erodibility and dust (PM10) emissions

ABSTRACTInducing biological soil crust (biocrust) development is an appealing approach for dust mitigation in drylands due to the resistance biocrusts can provide against erosion. Using a portable device, we evaluated dust emissions from surfaces either inoculated with biocrust, amended with a plant‐based soil stabilizer, or both at varying wind friction velocities. Four months after application, emissions from all treatments were either indistinguishable from or greater than controls, despite evidence of biocrust establishment. All treatments had greater surface roughness and showed more evidence of entrapment of windblown sediment than controls, factors which may have been partially responsible for elevated emissions. There was a synergistic effect of inoculation and stabilizer addition, resulting in a nearly two‐fold reduction in estimated emissions compared to either treatment alone. Stepwise regression analysis indicated that variables associated with surface crust strength (aggregate stability, penetration resistance) were negatively associated with emissions and variables associated with sediment supply (sand content, loose sediment cover) were positively associated with emissions. With more time to develop, the soil‐trapping activity and surface integrity of biocrust inoculum and soil stabilizer mixtures is expected to increase with the accumulation of surface biomass and enhancement of roughness through freeze–thaw cycles. © 2019 John Wiley & Sons, Ltd.

Analysis of soybean germination, emergence, and prediction of a possible northward establishment of the crop under climate change

Abstract Soybean (Glycine max (L.) Merr.) has the potential to improve sustainability of agricultural production systems. A higher focus on this crop is needed to re-launch its production in the EU. A better understanding of key determinants affecting soybean establishment represents a first step to facilitate its adoption in cropping systems. To this objective, we conducted laboratory and field experiments in order to better characterize seed germination and seedling growth in relation to temperatures, water content, and soil structure. We then used these data to parametrize the SIMPLE crop emergence model and to evaluate its prediction quality, by comparing observed field germination and emergence data with the predicted ones. Finally, we performed a simulation study over the 2020–2100 period, for three sowing dates, from mid-March to mid-April, in the northern climate of France to evaluate whether soybean will successfully establish in the Northern part of the country under future climate change. Experimental results showed that soybean germination was very fast, taking only 17 °C days to reach 50% germination at optimal conditions. The base, optimum and maximum temperatures were determined as 4, 30 and 40 °C, respectively while the base water potential was −0.67 MPa, indicating a high sensitivity to water stress. The SIMPLE model finely predicted germination and emergence courses and their final rates, compared with the observed field data. The simulation study showed average emergence rate ranging from 61 to 78% with little variability among sowing dates and periods, but a high variability between years. Main causes of non-emergence were: i) seedling mortality due to clods or soil surface crust, followed by ii) non-germination, and iii) seedling mortality due to drought. When sown in mid-April, seedling mortality due to drought was higher compared with earlier sowing dates. These results provide a better knowledge of soybean establishment that are encouraging to introduce soybean with early sowings to diversify current cropping systems.

On-Site Water and Wind Erosion Experiments Reveal Relative Impact on Total Soil Erosion

The relative impact of water and wind on total erosion was investigated by means of an experimental-empirical study. Wind erosion and water erosion were measured at five different sites: (1) Mediterranean fallow, (2) Mediterranean orchard, (3) wheat field, (4) vineyard and (5) sand substrate. Mean erosion rates ranged from 1.55 to 618 g·m−2·h−1 for wind and from 0.09 to 133.90 g·m−2·h−1 for rain eroded material over all tested sites. Percentages (%) of eroded sediment for wind and rain, respectively, were found to be 2:98 on Mediterranean fallow, 11:89 on Mediterranean orchard, 3:97 on wheat field, 98:2 on vineyard and 99:1 on sand substrate. For the special case of soil surface crust destroyed by goat trampling, the measured values emphasize a strong potential impact of herding on total soil erosion. All sites produced erosion by wind and rain, and relations show that both erosive forces may have an impact on total soil erosion depending on site characteristics. The results indicate a strong need to focus on both wind and water erosion particularly concerning soils and substrates in vulnerable environments. Measured rates show a general potential erosion depending on recent developments of land use and climate change and may raise awareness of scientist, farmers and decision makers about potential impact of both erosive forces. Knowledge about exact relationship is key for an adapted land use management, which has great potential to mitigate degradation processes related to climate change.

The spatial distribution of soluble salts in the surface soil of the Atacama Desert and their relationship to hyperaridity

Abstract We systematically investigated the spatial distribution of sulfates, chlorides, and nitrates in Atacama Desert soils in order to identify their relationship to long-term aridity gradients and to secondary redistribution and phase transformation. Thin surface crusts, powdery surface material and subsurface concretions from up to 40 cm depth were sampled along several latitudinal transects between 19.5–25°S and 68.5–70.5°W. The samples were characterized by total soil chemical analysis (ICP-OES and spectrophotometric analysis) complemented by XRD and thermogravimetric analysis to determine contents of chloride, nitrate, and major elements along with gypsum and anhydrite abundance in Atacama Desert soils. Our results demonstrate that the spatial distribution of gypsum, anhydrite, halite, and nitrates in Atacama Desert soils is indeed linked to aridity gradients, but also sources, and secondary dissolution processes. Nitrates and chlorides are best preserved between 19 and 22°S, which thus may constitute the long-term hyperarid core of the Atacama Desert. Remobilization within the soil is ubiquitous south of 22°S, but generally also occurs on the debris fans prograding from the Precordillera into the Central Depression. A near-constant concentration ratio of Na/Cl = 0.83 – very similar to the sea water ratio – throughout the desert and concentration maxima within the reaches of coastal fog penetration below the altitude of 1200 m reveals that sea spray is the primary source of halite in Atacama Desert soils. Calcium sulfates dominate Atacama Desert soils. Deposition is primarily as gypsum, but anhydrite is abundant in the northern Central Depression between 19 and 22°S. The apparent association of anhydrite with high concentrations of nitrate and chloride may point to a formation by dissolution and secondary reprecipitation from salt-concentrated fluids. The predominance of anhydrite in the Central Depression suggest geomorphology and water availability as additional factors remaining to be determined.

Development of an optical technique for characterizing presence of soil surface crusts

The expansion of the agricultural frontier and recurrent disturbances caused by intensive tillage practices are factors of exposure and degradation of the physical, chemical and biological properties of soil. When the soil is uncovered, the rain causes changes in its surface structure enabling the development of crusts. Surface crusting is a major detrimental issue to agriculture, as it damages the soil structure, reducing the water infiltration, thus modifying soil roughness and porosity, which increases run-off and erosion. Therefore, the monitoring and control of the occurrence of crusts must be continuous; however, the traditional techniques used to do that demand contact and destruction of the observed soil surface as well as time. This opens room for optical techniques that are potential tools in soil surface analysis in a fast, contactless and non-destructive way. Driven by this motivation, the present study developed a non-destructive, robust, low-cost, portable optical method for characterizing soil surface crusting. Images of samples with and without crusts in the laboratory as well as in the field were illuminated and recorded, with identification of parameters that could be related to presence or absence of surface crusts. The results confirmed the feasibility of using an optical technique as a contactless and non-destructive method for differentiating surface crusts in the field that can be also embedded in portable and low-cost apparatus.

Origin and timing of past hillslope activity in the hyper-arid core of the Atacama Desert – The formation of fine sediment lobes along the Chuculay Fault System, Northern Chile

Abstract Hillslopes represent areas of predominant denudation and constitute the transition and trajectory to floodplains; they play a crucial role in understanding the long-term landscape evolution of desert environments. However, although hillslope processes are known to be very slow or even stagnant in (hyper-) arid environments, process mechanisms under the virtual absence of water are poorly understood, and process rates are essentially unknown. Based on irrigation experiments, different monitoring techniques including drone-based high-resolution digital elevation models, geomorphological, stratigraphical, geochronological (OSL), sedimentological and geochemical investigations, as well as μCT scans of sediment cores, this contribution presents detailed insights into the chronostratigraphy of tongue-shaped, 50 m-long and 30 m-wide fine sediment lobes located along a 10–30° steep thrust-related slope east of the Salar Grande (Atacama, Chile). Irrigation experiments were performed to gain insights into precipitation thresholds for surface runoff and hillslope dynamics. Although artificial rainfall intensities were ~46 mm/h, infiltration was 100%, and the experiments did not initiate surface runoff or (detectable) slope material displacements. In addition, a distinct stratigraphic pattern with buried paleo-surfaces and paleo-biological surface crusts suggests increased hillslope activity during the late Pleistocene, potentially driven by changes of (fog-induced) humidity, salt-related shrink and swell processes, or paleo-seismic activity. While a variety of geo-bio-archives document periods of increased precipitation in the Andean parts of the Atacama Desert throughout the Quaternary, evidence for contemporaneous paleoclimatic changes from areas disconnected to Andean precipitation fluctuations (i.e., the Coastal Cordillera) is scarce. In this regard, the investigated landforms potentially represent one of only few sediment records recording paleoclimatic changes in the central desert, independent from Andean rainfall.

Using Biowastes to Establish Native Plants and Ecosystems in New Zealand

Biowastes can enhance the establishment of New Zealand (NZ) native vegetation, particularly on degraded land, where biological or physicochemical deficiencies limit plant growth. We identified critical success factors influencing selection and use of biowastes for a) growing native plants and b) rehabilitating native ecosystems. These were: weed competition; resilience (especially to drought and storms); ecosystem succession; and soil microbiome responses to elevated Nitrogen, Phosphorus, Organic Matter (OM) and contaminants (including Trace Elements). These factors determine the selection, timing and methods of biowaste application, selection of plant species and target ecosystems, and post-application management of receiving sites. Commonly planted native NZ species benefit from biowastes application where soils have depleted OM or sites with surface crusting, erosion, or high exposure to wind and temperature fluctuations. Commonly planted native species display luxury uptake of macro-nutrients, even on soils that are low-fertility under agricultural standards. Therefore, the growth responses to additional nutrients may be small. In contrast, most exotic weeds outcompete NZ species in high fertility soils. Therefore, biowaste application should not result in excessive nutrient availability. This can be achieved by using blends that contain a high-carbon biowaste, such as wood-waste, which immobilizes some macronutrients in the short term. We recommend long-term research using mixed-species field trials to identify biowastes and application methods that together support development of resilient native ecosystems. In particular, research should determine the role of biowastes on the beneficial mycorrhizae and native soil fauna. Application methods that enhance heterogeneity may help retain and/or build responsive microbiomes while conserving ‘native’ microbiomes to deliver sustainable, rehabilitated native ecosystems.

Mud volcano growth by radial expansion: Examples from onshore Azerbaijan

Abstract We investigated the mode of growth of flat-topped mud volcanoes, through the study of three active edifices onshore Azerbaijan: they are the Bozdag-Guzdek, the Ayazakhtarma and the Akhtarma-Pashaly mud volcanoes. The three edifices are up to 80 m high and 3 km wide, and have eruptions with recurrent times from a few months to a few years. Surface changes during and between eruptions were documented by a combination of mapping from satellite pictures, repeated direct observation over five years and structural analysis. In addition, resistivity profiles and microgravity measurements were used to decipher their subsurface geometries. We interpret the flat-topped character of the mud volcanoes as the result of rapid “isostatic” readjustment of a brittle surface crust,

COMPONENTS OF THE FLINT MADE INDUSTRY OF THE CUCUTENI-TRYPILLIAN COMMUNITY: EXTRACTION AND DISTRIBUTION OF FLINT

Having quite a massive and diverse source of raw materials tribes of Cucuteni-Trypillian community begin its active exploitation and utilization already from the early stages of their existence and continue throughout all their following history. Flint industry of Cucuteni-Trypillian community centers around two main scenarios: extraction — processing — distribution and / or extraction — distribution — processing of flint materials.
 There were a few completely different ways of flint extraction. First one (opened) was the simplest, did not require special skills and hard labor, being a simple collection of stones directly on the surface of the ground or in basseting areas (such as screes). Second one (closed) was the most complicated, requiring special tools, skills, hard labor and correspondingly more complicated organization of the community. This way implies flint extraction deep in its deposits that are often invisible from the surface crust. But it proved its value: flint miners obtained excellent high-quality materials for further processing, providing mineral wealth not only for their own communities, but also for close and remote related as well as non-Trypillian communities.
 We distinguished «close» and «remote» radiuses of obtained flint materials distribution. First term describes self-sustainment of separate communities with raw materials and products of its’ processing that were necessary for functioning of these collectives. Second term refers to directed massive production (extraction, processing) not only for internal needs, but mainly for exportation of obtained raw materials or finished wares, made of these materials.
 Also a question was raised regarding massive supply of regions that had no qualitative mineral wealth (Bug and Dnipro regions, area in — between Bug and Dnipro rivers) with flint from the proximate microregion in the Velyka Vys’ basin in contradiction to widespread belief about a more remote «donator» — Volhyn’ territory.
 Presence in Cucuteni-Trypillian community of flint-mining shafts, functioning of which required special skills and hard labor, specialized flint-processing workshops, transportation of raw materials and products of cleavage to remote territories became a basis for defining in this community a collective occupation, associated with flint mining and processing. Consequently, questions connected with this occupation, taking into account its’ versatility, complexity and scale should be among the basic ones in the complex study of trypillian economics.

Optimal feature selection for prediction of wind erosion threshold friction velocity using a modified evolution algorithm

Threshold friction velocity (u⁎t) is a very important parameter, which represents wind erosion potential. Because of the difficulty of measuring u⁎t, it would be advantageous if u⁎t could be estimated indirectly from its effecting factors that can be easily measured. The main purpose of this research was to quantify relationships between u⁎t and various topsoil features using inexpensive approaches. To prepare a reliable dataset, we used a portable wind tunnel for measuring u⁎t at a total of 118 observation points in Kerman province, southeast Iran. We developed a non-dominated sorting genetic algorithm II (NSGA-II), specifically designed to operate with artificial neural network (ANN) to select the most determinant properties that influence u⁎t. A permutation of nine input features including surface crust (SC), gravel coverage (GC), very fine sand (VFS), fine sand (FS), very coarse sand (VCS), electrical conductivity (EC), sodium adsorption ratio (SAR), calcium carbonate equivalent (CCE), and mean weight diameter (MWD), was introduced as explanatory variables. We also examined the potential power of using a Multi-Layer Perception (MLP) neural network for prediction of u⁎t changes in response to spatial variation of the selected features. The results of constructed MLP model revealed the ability of the model for u⁎t prediction and showed that the coefficient of determination (R2) values were 0.91 and 0.89 for training and testing data, respectively. Furthermore, acceptable level of the statistical validation criteria verified reliable performance of the MLP model. This research provided a powerful basis for prediction of u⁎t from topsoil features and surface roughness in arid and semi-arid areas of Iran; however, its generic framework could be used to other arid and semi-arid regions with similar challenges.

Image based quantitative comparisons indicate heightened megabenthos diversity and abundance at a site of weak hydrocarbon seepage in the southwestern Barents Sea.

BackgroundHigh primary productivity in the midst of high toxicity defines hydrocarbon seeps; this feature usually results in significantly higher biomass, but in lower diversity communities at seeps rather than in the surrounding non-seep benthos. Qualitative estimates indicate that this dichotomy does not necessarily hold true in high latitude regions with respect to megafauna. Instead, high latitude seeps appear to function as local hotspots of both megafaunal diversity and abundance, although quantitative studies do not exist. In this study, we tested this hypothesis quantitatively by comparing georeferenced seafloor mosaics of a seep in the southwestern Barents Sea with the adjacent non-seep seafloor.MethodsSeafloor images of the Svanefjell seep site and the adjacent non seep-influenced background seabed in the southwestern Barents Sea were used to construct georeferenced mosaics. All megafauna were enumerated and mapped on these mosaics and comparisons of the communities at the seep site and the non-seep background site were compared. Sediment push cores were taken in order to assess the sediment geochemical environment.ResultsTaxonomic richness and abundance were both considerably higher at the seep site than the non-seep location. However, taxa were fewer at the seep site compared to other seeps in the Barents Sea or the Arctic, which is likely due to the Svanefjell seep site exhibiting relatively low seepage rates (and correspondingly less chemosynthesis based primary production). Crusts of seep carbonates account for the higher diversity of the seep site compared to the background site, since most animals were either colonizing crust surfaces or using them for shelter or coverage. Our results indicate that seeps in northern latitudes can enhance local benthic diversity and this effect can take place even with weak seepage. Since crusts of seep carbonates account for most of the aggregating effect of sites experiencing moderate/weak seepage such as the study site, this means that the ability of seep sites to attract benthic species extends well beyond the life cycle of the seep itself, which has important implications for the larger marine ecosystem and its management policies.

Biocementation technology for construction of artificial oasis in sandy desert

Artificial oasis could be supported by the trapping and retaining rainfall water by impermeable layer of artificial material. In case of average annual rainfall in Arabian or Pakistani Deserts of 100 mm the watershed area must be at least 1000 ha to ensure rainfall water supply for consumption and irrigation in the artificial oasis of 100 ha area. Minimum cost for the sealing of 1000 ha of the sand slopes with 1 mm geosynthetic liner is about 112 mln Saudi Arabian Riyal, which could be not acceptable price for 100 ha of artificial oasis land. However, this cost could be diminished to 17 mln Saudi Arabian Riyal if to coat watershed slopes with 1 mm of biocemented sand crust using a low viscosity solution of biocement. Conventional cementation is cheaper but it cannot be used to make 1 mm sand crust because of a high viscosity of the cement suspension. The novel biotechnological method is based on the formation of the sand surface crust for water collection and transportation on the surrounding slopes. Most environmentally friendly biotechnology for this biocementation is aerobic biooxidation of cheap calcium formate or calcium acetate. Biocementation of the sand crust could be used to make a low-cost artificial desert oasis fed by rainfall.

How Comets Work

Abstract Two major questions regarding comets have been up to now far from any solution. (i) How is it possible that water-ice sublimation from the nucleus surface does not lead to an insulating crust, stopping every gas and dust ejection within a few days? (ii) How is it possible that the gas flow crossing the refractory surface crust ejects dust particles bonded by tensile strengths larger than tens of Pa when the perihelion gas pressure at the nucleus-coma interface is less than one Pa? We have developed a simple but rigorous analytical model, assuming that the cometary nucleus consists of agglomerates of ice and dust (“clusters”). As soon as the clusters become exposed to sunlight, gas diffusion from their inside leads to their dehydration. We find that (i) the gas diffusing from the interior to the surface of a sunlit cluster has a steep density gradient at the cluster surface, which blasts the cluster into particles of sizes larger than or equal to those actually observed by Rosetta dust instruments; (ii) the heat-conduction and diffusion timescales are much shorter than the dehydration timescale, ensuring that the described process prevents any dumping of the nucleus activity driven by water-ice sublimation from 4 au inbound to 4 au outbound; and (iii) the clusters are in fact cm-sized pebbles, so that a cometary nucleus made of pebbles is confirmed to be the only one consistent with cometary gas and dust activity, a process unexplained until now.

Selamento superficial e formação de crosta em solos representativos do Estado da Paraíba

The formation of seal and surface crust in the soil has direct consequences for the development of the crops and environmental quality, altering the soil structure, reducing the availability of water to the plants and favoring the erosion. The objective of this study was to evaluate the changes caused by successive rainfall events on the soil surface. Four soils were evaluated: Ferralsol; Acrisol; Leptsol; Luvisol. The selection criterion was based on pedogenetic development. The experiment was conducted under simulated rainfall, in experimental plots with a useful area of 0,3481 m², uncovered soil and slope of 0.10 mm-1. The tests were performed with mean precipitation intensity of 85 mm h-1 for 75 min, applied in three consecutive events at 7 day intervals, to determine the effects of surface sealing during rainfall and crust formation after the soil drying period. The hydraulic flow variables, the soil losses (PSi), soil disaggregation rate in interrill (Di) and the interrill erodibility factor (Ki) were evaluated. The formation of sealing and surface crusts were observed with increase of the flow velocity and liquid discharge, and the decrease of water sheet height, as well as in the changes in PSi, Di and Ki, being in the first event of simulated rainfall the greater contribution to formation of superficial crusting. TX showed the most stable after the successive events of simulated rainfall, even though the surface roughness was modified, did not present significant changes in the soil losses, disaggregation rate and soil interill erodibility. Keywords: Interill erosion, semiarid, sediment concentration, surface roughness, hydraulic flow variables.

Electrical resistance and mold distribution on beef surface as indicators of dry aging

AbstractThe objective of this study was to investigate the electrical resistance and mold distribution on a dry‐aged beef surface (crust) and to explore the use of these information as an indicator of dry aging. In total, 18 strip loins (longissimus lumborum) were dry aged for 35 days. During aging period, electrical resistance and mold distribution on the crust, pH, shear force, and sensory properties (appearance, flavor, tenderness, juiciness, and overall acceptance) of the edible portion of meat were assessed. Electrical resistance (R2 = .91, −.72, and .69, respectively) and mold distribution (R2 = .81, −.73, and .65, respectively) of the surface were strongly correlated to pH, shear force, and tenderness of dry‐aged beef (p < .05). Moreover, mold distribution had significant correlation to flavor (R2 = .48), among sensory properties. In conclusion, the electrical resistance and mold distribution on beef surface indicate the degree of dry aging, especially in tenderness and flavor..Practical applicationsThe manufacture parameters of dry aging have been varied with different meat producers, resulting in different final qualities of dry‐aged beef products. In this study, we suggested the use of indicators for determination of level of dry‐aging in beef including electrical resistance and mold distribution. It can help unexperienced small meat producers to guarantee the suitable degree of doneness of dry‐aged beef, especially in flavor and tenderness.

Multiphase reactivity of polycyclic aromatic hydrocarbons is driven by phase separation and diffusion limitations

Benzo[a]pyrene (BaP), a key polycyclic aromatic hydrocarbon (PAH) often associated with soot particles coated by organic compounds, is a known carcinogen and mutagen. When mixed with organics, the kinetics and mechanisms of chemical transformations of BaP by ozone in indoor and outdoor environments are still not fully elucidated. Using direct analysis in real-time mass spectrometry (DART-MS), kinetics studies of the ozonolysis of BaP in thin films exhibited fast initial loss of BaP followed by a slower decay at long exposure times. Kinetic multilayer modeling demonstrates that the slow decay of BaP over long times can be simulated if there is slow diffusion of BaP from the film interior to the surface, resolving long-standing unresolved observations of incomplete PAH decay upon prolonged ozone exposure. Phase separation drives the slow diffusion time scales in multicomponent systems. Specifically, thermodynamic modeling predicts that BaP phase separates from secondary organic aerosol material so that the BaP-rich layer at the surface shields the inner BaP from ozone. Also, BaP is miscible with organic oils such as squalane, linoleic acid, and cooking oil, but its oxidation products are virtually immiscible, resulting in the formation of a viscous surface crust that hinders diffusion of BaP from the film interior to the surface. These findings imply that phase separation and slow diffusion significantly prolong the chemical lifetime of PAHs, affecting long-range transport of PAHs in the atmosphere and their fates in indoor environments.

Ferrovolcanism: Iron Volcanism on Metallic Asteroids.

Metallic asteroids, the exposed cores of disrupted planetesimals, are expected to have been exposed while still molten. Some would have cooled from the outside in, crystallizing a surface crust which would then grow inward. Because the growing crust is expected to be more dense than the underlying melt, this melt will tend to migrate toward the surface whenever it is able. Compressional stresses produced in the crust while it cools will be relieved locally by thrust faulting, which will also provide potential conduits for melt to reach the surface. We predict iron volcanism to have occurred on metallic asteroids as they cooled and discuss the implications of this process for both the evolution and the modern appearance of these bodies.