•Continuous Terra Rossa soil monitoring provided data for a thermodynamic model.•Dissolution and precipitation of calcite in the soil was modelled at daily resolution.•The model suggests pedogenic ...carbonates being dissolved and precipitated seasonally.•Calcite nodules showing precipitation and dissolution events support the simulations.•Simulations suggest a variable threshold for inhibition of calcite precipitation in soils.
Red Mediterranean Soils developed over carbonate rocks can precipitate pedogenic carbonates at the base of their profiles, forming an evolutionary stage of calcretes. We studied a 0.6 m deep soil profile in Dalmatia (Croatia) where the lowest section of the soil is a calcic horizon formed by diffuse calcite particles and small nodules. These nodules record different events of dissolution and precipitation. Using a 3-month period of soil environmental monitoring, where soil temperature, soil water content, soil bulk electrical conductivity and soil air CO2 were measured, we implemented a thermodynamic model for dissolution and precipitation of calcite in the soil. The simulation shows a stage dominated by calcite dissolution during spring and early summer followed by a stage dominated by calcite precipitation. Soil air CO2 is the main control of the calcite reactions, with concentration of solutes also being of some importance during the stage of calcite precipitation. Soil water content and temperature, both affect soil air CO2. Precipitation events also have high-frequency impact on soil air CO2, but the response is complex. The model enables soil water solutions to be supersaturated in relation to calcite without precipitation of that mineral. Simulated soil water reached variable values of supersaturation in relation to calcite before its precipitation was triggered, suggesting that there is no fixed threshold value for the precipitation of calcite in a particular soil. During the 3-month simulated period, 83% of the calcite dissolved was reprecipitated as pedogenic carbonate. Most of the initially dissolved calcite, was expected to be diffuse pedogenic carbonate particles, although nodules and bedrock at the base of the soil should also have contributed to the solutes dissolved. Therefore, karst landscapes where soils have pedogenic carbonates are expected to record less denudation rates than those regions without calcretes.
This work, aside from being a classical discussion on the processes of rubefaction and illuviation, is an attempt to cross the abundant literature on red Mediterranean soils (RMSs) written by ...pedologists, and also by paleopedologists and geologists, with the climatic frame established by paleoclimatologists for the Quaternary. Such an approach leads us to consider that the development of the RMSs was discontinuous, occurring during periods of environmental stability, i.e. interglacials, characterized by a humid climate (precipitations exceeding evapotranspiration) with dry and hot summers. The impact of glacial intervals on the RMS covers is presently only partially documented. Aeolian processes during atmospheric instability episodes played a dominant role; however, hydric erosion and resedimentation cannot be ignored. Severe wind storms have reworked the RMS covers locally, but long distance dusts were also incorporated into the soils. Outbursts are proposed to explain the disruption observed in pre-Holocene red B horizons. Calcite from aeolian dusts was dissolved in surface horizons and recrystallized in deeper horizons in the form of discrete features and calcrete. During the more humid phases of these intervals, RMS became waterlogged in presently humid areas of the Mediterranean basin. The impact of frost on the RMS covers has been exaggerated. Precise correlations between the climatic fluctuations identified by paleoclimatologists and features and facies in the soil covers generated during the glacial intervals are almost impossible to establish.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Geoarchaeological survey on the island of Gozo combined with test excavations and new chronometric dating of two Neolithic temple sites at Santa Verna and Ġgantija on the Xagħra plateau have revealed ...well-preserved buried soils which tell a new story of soil development and change for the early-mid-Holocene period. Micromorphological analysis has suggested that the earlier Neolithic climax soil type was a thick, well-developed, humic and clay-enriched argillic brown Mediterranean soil. With human intervention on the Xagħra Upper Coralline Limestone plateau from at least the early 4th millennium BCE, the trajectory of soil development quickly changed. Radical soil change was marked by the removal of scrub woodland, then consequent poorer organic status and soil thinning, and rubefication and calcification, no doubt exacerbated by Neolithic agricultural activities and a more general longer-term aridification trend. The beginnings of this transitional brown to red Mediterranean soil change process has been observed at Santa Verna temple by the early 4th millennium BCE, and appears to be much further advanced by the time of the latter use of Ġgantija temple in the early-mid-3rd millennium BCE. There is also evidence of attempts at amending these deteriorating soils during this period and into the 2nd millennium BCE, a practice which probably underpinned the viability of later Neolithic agricultural society in the Maltese Islands. The changes observed ultimately resulted in the creation of the thin, xeric, red Mediterranean soils on the Coralline Limestone mesa plateaux which are typical of much of Gozo and Malta today.
•Buried soils at two Neolithic sites on Gozo tell a new story of soil development.•Micromorphological analysis shows these soils are well-developed argillic brown soils.•Human activities and xerification led to rapid degradation and calcification.•There is evidence of amending these deteriorating soils in the mid-3rd M BCE.
Using SEM-supported microsurface and analytical methods we studied quartz and rare feldspar grains of the sand fraction >250 μm from three soil profiles in Jordan. The soils including a Lithosol are ...of different maturity and diagenetic alteration of their bed rocks, which are sandstone, limestone, and basalt. The profiles had been investigated during projects on the environmental history of the region, whereas the quartz grain surface analysis (QGSA) that has been applied for the first time to Jordan soils is an essential part of a supplementary study that was initiated when findings of unusual mineral components in a red basalt soil raised questions of their source and the history of this soil.
The major transport processes and environments that were reconstructed for the sandstone Regosol and the Red Mediterranean Soil (RMS) on Early Tertiary limestone are documented by successions and types of grain-morphological features that apparently reflect varying water dynamics partly alternating with aeolian motion – a result, which matches with the known sedimentary history of their bedrocks and supports the reliability of the quartz grain surface analysis (QGSA). The microtexture pattern for the exotic quartz grain community in the basalt soil on an Early Quaternary basaltic rock showed a high similarity to those of the limestone samples. Part of the quartz grains from the basalt soil turned out to be chert as is present in the RMS profile and was an essential indication for the source of quartz. A sufficient explanation for the presence of quartz is that the outcropping, weathered Eocene Umm Rijam Chert Limestone Formation, among them chert nodules, was reworked and transported to the top of the weathering basalt. While a feldspar grain from the sandstone Regosol shows a conformable pattern to the quartz grains, plagioclase single grains from the red basalt soil, in contrast, are primary mineral components of the source rock. These preserved plagioclases exhibit only minor features of chemical weathering corresponding to the young, non-diagenetic bedrock. The size of the grains and situation of the basalt cap in the landscape, as well as preliminary dating suggest a period of heavy storms in Jordan at some time during the Pleistocene.
•Comparative study of soils on different bedrocks in Jordan;•SEM-supported methods applied for the first time to this region;•Chert fragments as reference for in-situ formation and source indicator;•Quartz grains and chert fragments indicating palaeoenvironmental relationships002E
Monazite ((Ce, La, Nd, Th) PO
4
) is a rare and strategic mineral that occurs naturally as an accessory and minor mineral in diverse igneous and metamorphic rocks. This mineral does not frequently ...form mineable ore deposits and it has different typologies, including those formed by endogenous processes (generally “yellow monazite” mineralizations) and those formed by exogenous processes (“gray monazite” mineralizations). The mineral is an important ore of Rare Earth Elements (REEs), which have been identified by the European Union as critical raw materials. Monazite can be considered a weathering-resistant mineral, and the mobility of the REE and associated elements is low. The study reported here concerns a mineralogical and geochemical assessment of the occurrence and risks associated with the presence of concentrations of monazite in a typical, well-developed, and representative red Mediterranean soil, in order to establish the associated risk with their future mining. The results confirmed that monazite ore is particularly poor in radioactive elements, and it is concentrated in the most surficial soil horizons. The chemical mobility of REEs present in the soil, as assessed by selective extraction with ammonium acetate in acidic media, follows the order Y > Dy > U > Tb > Gd > Eu > Sm > La > Th > Ce. The mobility of REEs contained in monazite proved to be higher than that of the REE compounds in the upper horizons of the soil profile suggesting the immobilization in other REE-containing minerals, while light REEs show lower mobility rates than heavy REEs, due to an immobilization of LREE by sorption with iron oxy-hydroxides. Further studies are required in order to obtain better speciation data for REEs in soils aimed to identify soluble and insoluble compounds.
The aim of this study was to analyze and classify the soils of the municipality of Alcubillas (La Mancha, Central Spain) and establish their suitability for vine cultivation. Alcubillas is a ...traditional location dedicated to vineyards and the production of wine. The pedological fingerprint of this location is the iconic red Mediterranean soil, and a plausible process for the soil formation is discussed. Considering the nature of the soils and the extent and types of natural limitations, as defined by the eight classes of land capability established by the US Soil Conservation Service, the majority of the soils in Alcubillas are suitable for vineyards (i.e., classes 1, 2 and 3) while moderately suitable sites only occupy a small area. The marginally suitable land class is located around a single hill, which occupies only a few hectares of terrain. Given that soil is a major factor in terroir expression, the findings reported here highlight the importance of soil suitability in determining vine performance in vine-growing zones with a Mediterranean environment.
Soil Fe oxides occur in almost all soils and reflect different environmental conditions by the high variability of their mineralogy and concentration. Quantitatively determining this important ...pedogenic indicator enables diffuse reflectance spectroscopy (DRS) based on material-specific absorption characteristics. This paper presents a methodology that directly links free Fe oxide content (Fed, citrate-dithionite extractable Fe) with the diagnostic Fe absorption band near 900 nm (Fe-NIR). In addition, we investigated the influence of soil texture on the spectral characteristics and prediction accuracy. We showed that the Fe absorption bands of clay-dominated soil samples were, in general, deeper than sand-dominated samples with comparable Fed content. Based on the Fe-NIR absorption depth, we created two texture-dependent Fed prediction models, retrieving the best Fed estimates for the sand calibrated model (R2v = 0.87, rel. MSEv = 13.9%). Due to the high texture variability in sand, silt, and clay fractions of the clay-silt dominated samples, the clay-silt calibrated model produced good predictions (R2v = 0.70, rel. RMSEv = 19.0%). The soil texture appeared to have no significant influence on model stability but did affect the prediction accuracy. Constant Fed contents were over- and underestimated when applying the texture-dependent models to other texture groups. The texture-independent model was stable and performed well (R2v = 0.76, rel. RMSEv = 18.1%). These results are highly relevant to the subsequent spatial assessment of free Fe oxide content as an indicator for soil development from hyperspectral remote sensing data.
The aim of this work was to map Red Mediterranean soils, for which no previous mapping approach exists, using optical multispectral satellite remote sensing data. This case study explores the use of ...SPOT XS images over the viticultural Southern Rhone Valley, France, to map exposed vineyard soils. Field spectral measurements were used to distinguish Red Mediterranean soil surfaces during Spring 1999. A supervised maximum likelihood classification was applied to sparsely vegetated and unvegetated surfaces of two spring images from 1995 and 1997, drawing on the field training set and available soil data. Similar global spatial segmentation was obtained despite different soil surface states on these dates. Classification performances were higher than 84% in both images. Mean classification accuracies of Red Mediterranean soils at seven reference surfaces were 60% in 1995 and 70% in 1997. This suggests that the direct use of optical remote sensing data at medium resolution can be useful for mapping bare Red Mediterranean soils.
Application of alkaline fly ash to acid soils is related to beneficial effects, such as increase of pH to a desired level and nutrient supply to plants, and to possible adverse effects, such as ...enrichment of soils with substances toxic to plants and animals (e.g. B, Mo, Se) and increase of salinity to undesirable levels. Therefore, use of alkaline fly ash as a beneficial amendment of acid soils needs to be evaluated with respect to phytotoxic and environmental impacts. Samples of alkaline fly ash, from two different sources, were added to two Red Mediterranean acid soils at rates equal to 5, 20 and 50 g kg
−1 soil, and changes, relative to the untreated soil, of soil pH, salinity, B and P levels were measured. Ryegrass (
Lolium perenne L.) was grown in pots containing fly ash–soil mixtures for 300 days, and dry biomass yield and cumulative plant uptake of B and P were calculated. Soil application of fly ash at these rates increased the pH, up to about 8, and the electrical conductivity of the saturation extract, up to about 2.5 dS m
−1, in both soils. Available soil P (0.5 M NaHCO
3 extractable) was unaffected by fly ash application. Water soluble B remained less than 1 mg litre
−1 in the saturation extract, and hot water extractable B was less than 1 mg kg
−1 soil. Dry biomass yield of ryegrass and cumulative plant uptake of B and P increased significantly with fly ash application. Therefore, fly ashes with low B and salt content can be used as liming agents in acid soils at rates not exceeding the 40 Mg/ha. Potential environmental impacts must also considered.
The various iron fractions were quantified by selective dissolution (Fe
d
, Fe
o
, Fe
t
) in four Red Mediterranean soils, developed on metarhyolite and metadolerite. They were similar in all ...profiles. A strong trend of iron removal from the surface horizon and of its subsequent illuvial translocation to the argillic horizons was observed. In all profiles, Fe
o
was not related to the organic matter content indicating the Mediterranean xeric soil environment. The Fe
o
/Fe
d
ratio and the percentage of crystalline iron oxides (Fe
d
-Fe
o
) suggested that the pedoenvironment in which the profiles P1, P2 were formed, allowed the high crystallization of iron oxides. As indicated by the Fe
d
/Fe
t
values, the weathering process was more intense in the metarhyolite-developed soils. In contrast, the metadolerite-developed soils present conditions of poorly crystallized iron oxides and a lower degree of development.
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