•Bayerite (Al(OH)3) formed in an unusual setting in wetlands of the Galápagos archipelago.•Abundant bayerite coatings occur along macropores in Al-rich amorphous material.•Bayerite developed by rapid ...crystallisation from interstitial solutions.•Transformation of bayerite to gibbsite is considered to be an ongoing process.
The lower part of a shallow profile on volcanic ash from Isla Santa Cruz of the Galápagos archipelago was found to contain abundant bayerite, a relatively rare Al(OH)3 polymorph, as confirmed by X-ray diffraction and Raman spectroscopy analyses. The bayerite-bearing interval consists of orange-brown colloidal material with high Al and Fe content, and it contains bayerite in the form of pervasive thin coatings along the sides of pores, including planar voids and narrow channels. Associated gibbsite seems to occur as part of the coatings. Bayerite is interpreted to have formed by rapid crystallisation from solutions derived from the Al-rich groundmass. Gibbsite is regarded as the product of an ongoing process of bayerite transformation.
The knowledge of the lithological context is necessary to interpret trace elements concentrations in the soil. Soil magnetic signature (χ) and soil X-ray fluorescence (XRF) are promising approaches ...in the study of the spatial variability of trace elements and the environmental monitoring of soil quality. This research aimed to assess the efficiency of measurements of χ and XRF sensors for spatial characterization of zinc (Zn), manganese (Mn), and copper (Cu) contents in soils of a sandstone-basalt transitional environment, using machine learning modeling. The studied area consisted of the Western Plateau of São Paulo (WPSP), with soils originating from sandstone and basalt. A total of 253 soil samples were collected at a depth of 0.0–0.2 m. The soils were characterized by particle size and chemical analysis: organic matter (OM), cation exchange capacity (CEC), ammonium oxalate-extracted iron (Feo), sodium dithionite-citrate-bicarbonate-extracted iron (Fed), and sulfuric acid-extracted iron (Fet). Hematite (Hm), goethite (Gt), kaolinite (Kt), and gibbsite (Gb) contents were obtained by X-ray diffraction (XRD). Magnetite (Mt) and maghemite (Mh) contents were obtained by soil χ, while trace elements contents were obtained by XRF and predicted by χ. Descriptive analysis, the test of means, and correlation were performed between attributes. Zn, Mn, and Cu contents were predicted using the machine learning algorithm random forest, and the spatial variability was obtained using the ordinary kriging interpolation technique. Landscape dissections influenced iron oxides, which had the highest contents in slightly dissected environments. Trace elements contents were not influenced by landscape dissections, demonstrating that lithological knowledge is necessary to characterize trace elements in soils. The prediction models developed through the machine learning algorithm random forest showed that χ can be used to characterize trace elements. The similar spatial pattern of trace elements obtained by XRF and χ measurements confirm the applicability of these sensors for mapping it under lithological and landscape transition, aiming for sustainable strategic planning of land use and occupation.
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•Parent material determines the spatial distribution of potentially toxic elements in the soil.•Landscape dissection influences maghemite contents in basaltic soils, with higher contents present in slightly dissected environments.•The ferromagnetic minerals magnetite and maghemite have higher correlations than the antiferromagnetic minerals hematite and goethite, with the contents of the element being potentially toxic.•Sensors that provide measurements of X-ray fluorescence and magnetic susceptibility are useful for characterizing potentially toxic elements.
The long-term effect of using treated wastewater is not clearly defined: some researchers argue that it is better than freshwater for the soil health; others disapprove, claiming that irrigation with ...unconventional water resources causes soil degradation. This study assesses the impact of irrigation with non-traditional water on the chemical and mineralogical properties of a calcareous clayey soil from West Texas. The exponential rise in population and the realities of climate change contribute to the global increase in freshwater scarcity: non-conventional water sources, such as treated wastewater (TWW) and brackish groundwater (BGW), offer potentially attractive alternative water resources for irrigated agriculture. For this research, the differences between TWW and BGW were addressed by collecting and analyzing water samples for salt and nutrient content. Soil samples from three horizons (Ap, A, and B) were obtained from three different fields: Rainfed (RF), BGW irrigated, and TWW irrigated. Soil was analyzed for texture, salinity, sodicity, and carbon content. Clay mineralogy of the three different fields was analyzed using the B-horizons. The outcomes from the analysis showed that the BGW from the Lipan aquifer has higher salinity and is harder compared to TWW. Although the exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and electroconductivity (EC) increased marginally compared to the control soil (RF), the soils were in good health, all the values of interest (SAR < 13, ESP < 15, pH < 8.5, and EC < 4) were low, indicating no sodicity or salinity problems. Smectite, illite, and kaolinite were identified in the three B-horizon samples using bulk X-ray diffraction (XRD). Overall, no major changes were observed in the soil. Thus, TWW and BGW are viable replacements for freshwater irrigation in arid and semi-arid regions.
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•Treated wastewater has a better quality than the brackish groundwater of the local aqufer•Calcareous clayey soil showed no salinity or sodicity problems after long-term (15 years) irrigation with non-freshwater•Clay mineralogy in this soil type is fairly stable and plays a major role in the fertility of the soil•Treated wastewater and brackish groundwater are viable substitutes for freshwater irrigation in semi-arid and arid regions
An understanding of the mineral nutrition of plants is of fundamental importance in both basic and applied plant sciences. The Third Edition of this book retains the aim of the first in presenting ...the principles of mineral nutrition in the light of current advances. This volume retains the structure of the first edition, being divided into two parts: Nutritional Physiology and Soil-Plant Relationships. In Part I, more emphasis has been placed on root-shoot interactions, stress physiology, water relations, and functions of micronutrients. In view of the worldwide increasing interest in plant-soil interactions, Part II has been considerably altered and extended, particularly on the effects of external and interal factors on root growth and chapter 15 on the root-soil interface. The third edition will be invaluable to both advanced students and researchers.
Identifying the bioavailability and release-desorption mechanism of heavy metals (HMs) in soil is critical to understand the release risk of HMs. Simultaneously, the mechanistic investigation of ...affecting the bioavailability of HMs in soil is necessary, such as the grain-size distribution and soil mineralogy. Herein, the bioavailability of HMs (Cu, Cd, Ni, Pb, and Zn) in different area soils near a typical copper-smelter was evaluated by the sequential extraction technique (BCR), diffusive gradients in thin-films (DGT), and DGT-induced fluxes in sediments (DIFS) model. Results showed that the HMs proportion of the residual fraction in all soils was the highest. The average bioavailability concentration (CDGT) of Cu and Cd in industrial soil was the highest, with 45.12 μg· L−1 and 9.06 μg· L−1. The result of DIFS model revealed that the decreased order of the mean value of desorption rate constant (K-1) was Cd > Zn > Ni > Cu > Pb, 5.91 × 10−5, 4.96 × 10−5, 2.89 × 10−5, 9.64 × 10−6, and 8.69 × 10−6, respectively. According to the spatial distribution of release potential (R-value), the release potential of labile-Cu in agricultural soil was the highest, which was mainly attributed to fertilizer application in farmland. Simultaneously, the reduced hydroxyl was also related to the agricultural activities, resulting in the weakened adsorption capacity of HMs by soil. Redundancy analysis (RDA) results showed that the bioavailability of Cd, Ni, and Zn was mainly driven by soil pH, while the bioavailability of Cu and Pb was primarily driven by dissolved organic carbon (DOC). Meanwhile, carbonate minerals had a positive correlation with the bioavailability of Cd, Ni, and Zn, which could promote the release of HMs in mining soil as chemical weathering progresses. In conclusion, this study provides a structured method which can be used as a standard approach for similar scenarios to determine the geochemical fractionation, bioavailability, and release kinetics of heavy metals in soils.
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•The desorption rate of Cd was highest than the other elements in this study.•The decrease of the hydroxyl weakened the adsorption of metals by the soil solid.•PH is the most dominant factor influencing bioavailability of Cd, Ni, and Zn.•Dissolved organic carbon is positively correlated to bioavailability of Cu and Zn.
The rate of K.sup.+ leaching from soil minerals such as K-feldspar is believed to be too slow to provide agronomic benefit. Currently, theories and methods available to interpret kinetics of mineral ...processes in soil fail to consider its microfluidic nature. In this study, we measure the leaching rate of K.sup.+ ions from a K-feldspar-bearing rock (syenite) in a microfluidic environment, and demonstrate that at the spatial and temporal scales experienced by crop roots, K.sup.+ is available at a faster rate than that measured with conventional apparatuses. We present a device to investigate kinetics of mineral leaching at an unprecedented simultaneous resolution of space (~10.sup.1 -10.sup.2 mum), time (~10.sup.1 -10.sup.2 min) and fluid volume (~10.sup.0 -10.sup.1 mL). Results obtained from such a device challenge the notion that silicate minerals cannot be used as alternative fertilizers for tropical soils.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•C:N ratios in soils and particle-size fractions were assessed in tropical highlands.•Sand C:N ratios increase with depth, whereas silt and clay C:N vary little.•C:N ratios decrease with increasing ...Ca and Mg contents, CEC, and clay activity.•N-enrichment in clays is likely controlled by mineralogy.•R-NH3+ sorption onto clays can be critical to organic matter stabilization.
Factors affecting soil organic carbon (SOC) retention in the tropics are relatively well known, but this is not the case for N retention and thus C:N ratios, a common proxy for organic matter stability. Recent data suggest that SOC and N concentrations vary with climate, whereas soil C:N ratios depend on particle-size fractions contents. However, such knowledge is still incipient for tropical soils, native vegetations and deeper soil layers, which are critical to understand how land use and climate change affect C and N fluxes. We assessed SOC, N and C:N ratios in bulk soils and sand, silt and clay fractions, and their correlations with other soil properties under native tropical forests in the highlands near Lavras, Brazil. Soil samples were collected to 1-m depth in soils of contrasting texture and mineralogy, formed on quartzite, sericite-schist, gabbro, itabirite, ironstone, meta-limestone, gneiss, and phyllite. Mean SOC and N concentrations were generally high, whereas mean soil C:N ratios varied from 9.5 to 18.7 among parent materials, and only in three soils C:N ratios varied considerably with depth. Enrichment factors (EFs) were generally < 1 in the sand and silt fractions for SOC and especially N. Conversely, EFs for clay were mostly > 1 for SOC and even higher (up to 6.58) for N. Such trend indicates that SOC and N are concentrated in clays, and more importantly, that N sorption is favored compared with SOC, and likely dependent on clay mineralogy. Soil C:N ratios decreased with increasing values of exchangeable bases, due to higher N in the most fertile soils, suggesting that a mechanism of R-NH3+ cationic sorption is likely involved. Our results suggest that soil N is a critical component of the overall stabilization of soil organic matter onto clays of tropical soils, deserving further investigation also under temperate climate and other zones.
The availability of nitrogen (N) is a critical control on the cycling and storage of soil carbon (C). Yet, there are conflicting conceptual models to explain how N availability influences the ...decomposition of organic matter by soil microbial communities. Several lines of evidence suggest that N availability limits decomposition; the earliest stages of leaf litter decay are associated with a net import of N from the soil environment, and both observations and models show that high N organic matter decomposes more rapidly. In direct contrast to these findings, experimental additions of inorganic N to soils broadly show a suppression of microbial activity, which is inconsistent with N limitation of decomposition. Resolving this apparent contradiction is critical to representing nutrient dynamics in predictive ecosystem models under a multitude of global change factors that alter soil N availability. Here, we propose a new conceptual framework, the Carbon, Acidity, and Mineral Protection hypothesis, to understand the effects of N availability on soil C cycling and storage and explore the predictions of this framework with a mathematical model. Our model simulations demonstrate that N addition can have opposing effects on separate soil C pools (particulate and mineral‐protected carbon) because they are differentially affected by microbial biomass growth. Moreover, changes in N availability are frequently linked to shifts in soil pH or osmotic stress, which can independently affect microbial biomass dynamics and mask N stimulation of microbial activity. Thus, the net effect of N addition on soil C is dependent upon interactions among microbial physiology, soil mineralogy, and soil acidity. We believe that our synthesis provides a broadly applicable conceptual framework to understand and predict the effect of changes in soil N availability on ecosystem C cycling under global change.
Understanding nitrogen limitation of decomposition has direct consequences for understanding and forecasting soil and ecosystem carbon storage potential. Observational evidence suggests that nitrogen can limit microbial decomposition, but many nitrogen fertilization experiments directly contradict this conclusion. Here, we resolve this apparent contradiction by synthesizing covarying effects of nitrogen on microbial element limitation and soil acidity, and use a mathematical model to demonstrate how the net outcome for soil carbon storage depends on interactions between microbial physiology, acidity, and soil mineralogy.
This study comprehensively investigated the potential roles of soil mineralogy identified by the automated mineral liberation analysers (MLA) in the prediction of geochemical behavior of toxic metals ...in the smelter polluted soils. The results from modal mineralogy revealed that the non-reactive silicate phases such as quartz (42.05%) and biotite (40.43%) were the major mineralogical phases. The element deportment showed that fayalite, lead oxide, apatite, galena and wollastonite were identified as the dominant As, Cd, Pb and Zn bearing minerals. Furthermore, MLA analysis also confirmed that Pb was most concentrated in the smaller particles of lead oxide, which significantly enhanced Pb release in reaction with the chemical extractant during chemical kinetic tests. The results from pH-dependent leaching tests indicated that the leaching concentrations of As, Pb and Zn increased at low and high pH values, but were lowest at the neutral pH range. In addition, the results from the kinetic study demonstrated that the second order model provided the best description for the release patterns of the main metal contaminants in the bioavailability and bioaccessibility tests. The integrated geochemical analysis demonstrated that among these studied elements, As showed a typical geochemical pattern, which was predominantly controlled by 90.09% of fayalite. The above study results would have significant implications for soil remediation and risk management of smelter contaminated sites.
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•An automated mineralogy system (MLA) was employed to the smelter polluted soils.•A variety of As, Pb and Zn hosting mineral phases were identified by MLA analysis.•98.61% of As, 22.23% of Pb and 83.57% of Zn were bound to the silicate minerals.•The silicate minerals played key roles in the geochemical stability of toxic elements.•Soil mineralogy provided an insight into the geochemical patterns of toxic metals.
Centella asiatica is an herbal plant with many health benefits due to the content of asiaticoside compounds. Factors affecting asiaticoside content are altitude, soil texture, and soil nutrient ...status. This research aimed to identify the effect of zeolite, Psub.2 Osub.5 fertilizer, and soil media from different altitudes on C. asiatica. The research was conducted in a greenhouse from August 2017–June 2018. The experimental design was a factorial, completely randomized design with three factors and four replications. The first factor was soil media that originated from 100, 450, and 900 m above sea level (asl), the second factor was the dose of Psub.2 Osub.5 fertilizer (0, 27, 54, and 81 kg hasup.−1 ), and the third was the dose of zeolite (0, 3, and 6 t hasup.−1 ). The results showed that applying zeolite minerals at all altitudes increased nutrient availability and soil cation exchange capacity (CEC) by up to 70%. The novelty of this study is that the soil from an altitude of 900 m asl, with a Psub.2 Osub.5 fertilizer dose of 54 kg hasup.−1 , has a loamy sand soil texture and produces the highest asiaticoside content (3.61%) and the largest plant dry weight (19.24 g). These results did not significantly differ from those obtained from the soil 450 m asl with a sandy loam soil texture (the most suitable soil texture for C. asiatica), that is 3.37% asiaticoside and 19.87 g plant dry weight. This study concluded that C. asiatica could develop in loamy sand soil by giving it 54 kg hasup.−1 Psub.2 Osub.5 fertilizer.
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![The Effect of P[sub.2]O[sub...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/2071-1050/small "The Effect of P[sub.2]O[sub.5] Fertilizer, Zeolite, and Volcanic Soil Media from Different Altitudes on the Soil Mineral, Growth, Yield, and Asiaticoside Content of ICentella asiatica/I L")