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•Struvite crystallization can take place even using high total solids digestate.•Seawater bittern can be used as alternative source Mg2+ source.•Struvite can be a substitute of ...chemical fertilizers in agronomic test.•Seawater bittern can improve downstream transferability of struvite precipitation.
Phosphorus recovery from digestate is considered a challenge because the possible discharge can lead to eutrophication. This study focuses on phosphorus recovery as struvite from the liquid fraction of swine manure digestate at a high total solids concentration, by using a lab-scale crystallizer operated in continuous mode (7 L·d−1). A by-product of salt production (seawater bittern, SWB) was assessed as Mg source for the formation of struvite instead of a chemical dosage (MgCl2) within a circular economy approach. Different Mg/P (1.8:1; 2:1; 3:1) ratios and different TS contents (TS 3.5 and 4.5 %) were studied. The maximum P recovery of 85 % and N recovery of 52 % was obtained at 4.5 % of TS and Mg/P ratio of 2:1, corresponding to an overall P and N recovery on the raw digestate of 70 % and 46 %, respectively. The presence of struvite was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM-EDS). Dried samples were then used as fertilizer in agronomic pot tests using Brassica rapa chinensis. Struvite obtained, showed comparable fertilizing properties in comparison with conventional fertilizers in terms of P (Mineral 5.6 ± 0.4; Poultry 5.7 ± 0.2; Struvite 5.9 ± 0.1 g kg−1), N and total biomass content such as chlorophylls ratio. The growth tests confirmed the possible use of struvite recovered as competitive alternative to conventional chemical phosphate fertilizers. The results showed that it can be possible to promote sustainable P recovery from high solids digestates by the combination of crystallizer reactor and Mg-salt byproducts.
Denudation processes affecting mountain slopes may vary according to different factors (e.g., lithology and structural setting of bedrock, climate, relief features), which may be very diverse at the ...local scale. Gully complex systems, characterised by morphological features similar to those developing in other climate contexts (i.e., pseudo-badlands) are also becoming common at higher altitudes and latitudes. The selected study cases of Gran Gorgia (Susa Valley) and Saint Nicolas (Aosta Valley), in the Western Italian Alps, are sites of geomorphological interest as they are specifically relevant for their scientific features. The aims of this work are (i) reconstructing the morphometric evolution of gully systems and vegetation colonisation time by means of multitemporal spatial analysis on surface morphological changes under water erosion; (ii) reconstructing in detail, through dendrogeomorphological analysis, the progressive spatial surface denudation and changes in erosion rates, by analysing trees and exposed roots and using different indicators (i.e., compression wood, traumatic resin ducts); (iii) obtaining data on successive aggradation/degradation episodes along slopes surrounding such hotspots through geopedological investigations; and (iv) identifying which control factors exert a predominant role on denudation patterns in such contexts. Multidisciplinary analyses regarding the study sites allowed for detailing of erosional history of the studied slopes detecting the prevailing drivers of their evolution. According to the results and considering the common climate and bedrock conditions, the structural background seems to have more influence on slope evolution at the Saint Nicolas site, while superficial geomorphic processes seem to be more relevant at the Gran Gorgia site. Because the sites have already been recognised as part of geoheritage by local authorities, the data obtained in the present research on their genesis, evolution, and local drivers affecting the rates of denudation (i.e., scientific relevance of the site) suggests that description of the sites for dissemination purposes should include links to the entire slope history.
•Multidisciplinary analyses allowed detailing erosional history of studied slopes.•Specific indicators of geomorphic disturbance were individuated for the study sites.•Weakly developed soils and buried surfaces testify diverse geomorphic contexts.•Erosion rates in study sites are higher than in analogous geomorphological contexts.•The local drivers of denudation were identified as both structural and geomorphic features.
In temperate regions, eolian deposits of different natures are often pedogenically-altered and mixed with underlying sediments. The research reported in this paper identifies for the first time the ...presence of eolian deposits in soils of central Tuscany and investigates the characteristics and origin. Five relict, polycyclic paleosol profiles were studied. P1 was situated in a natural dust trap, a doline on top of an isolated limestone hill; P2 and P3 were both situated on a limestone plateau, and P4 and P5 on a mid- and foot slope on schist. The profiles were sampled for routine analyses, iron forms, heavy minerals, major and trace elements, and pollen, spores and non-pollen palynomorphs. Undisturbed samples were taken for micromorphological and SEM analyses. Nine soil horizons were sampled for OSL dating. Eolian deposits were dominant or abundant in the first layers of P1, P2 and P3. OSL age determinations of soil horizons deriving from eolian parent material were middle Holocene. Chemical and heavy mineral analyses indicated different possible sources, including bare slopes, alluvial fans and wide channels, coming from the nearby streams that drain the Middle Tuscany ridge and the Mounts of Chianti; marginal contribution of volcanic ashes was only found in P1.
The research demonstrated that wind soil erosion accompanied water erosion and colluvial deposition during the middle Holocene in the Elsa River basin. Pollen spectra, in particular, indicated that soil degradation occurred in an environment showing signs of incipient desertification, resulting from an increase of aridity in a land already strongly influenced by humans. Although central Italy is currently considered to be only marginally affected by wind soil erosion, a climate change, which would imply increased arid conditions, could trigger a new cycle of slope denudation, wind erosion and loess deposition.
In high-altitude environments, most of the debris-free glacier forelands are increasingly widening and the bare surfaces left by retreating glaciers offer the opportunity to investigate the evolution ...of soil through time. The main aim of this study is to discuss the applicability of a chronosequence approach in a deglaciated area, by considering the role of different soil forming factors. A study case has been selected (Alpe Veglia, Lepontine Alps), where field and laboratory characterizations were performed along a transect of 12 soil profiles from the proglacial area of the Aurona Glacier to the Alpe Veglia hollow, crossing different age glacial deposits. The results of soil physical and chemical analyses underline a time-trend of soil properties. On the other hand, even if the soil properties variability along the transect can be mainly explained according to the soil chronosequence approach, the data seem to highlight how the various soil forming factors (e.g. parent material, relief, vegetation) influence soil features, partly masking the effect of the time factor inducing a divergence from a traditional chronosequence. In particular, the morphology of the surrounding reliefs, depending on bedrock lithologies and structures, and the geomorphic dynamics seem to affect soil formation and evolution.
Load-carrying capacities of flying animals have important effects on their reproductive success, because it is expected that better performing individuals will benefit during activities such as ...foraging and nest building. Individually marking Sceliphron mud dauber wasp females and collecting their mud balls at three field sites, we investigated whether wasps maximize mud ball lifting and we evaluated whether the characteristics of soil affect wasp-mud ball size relationships. Sceliphron destillatorium, larger than Sceliphron spirifex, collected on average heavier and larger mud balls, and individual female body mass was positively correlated with the mass and volume of carried mud balls. Rarely mud balls reached a weight close to the theoretical maximum. On the other hand, the volume of mud balls roughly coincided on average with the theoretical maximum. A simple theoretical model showed that loss of balance during loaded flights is in part responsible for the failure to maximize the mass lifted, reducing the load-carrying capacity with a per cent value that is independent of the wasp's size. Soil characteristics also seem to affect the lifting dynamics of wasps: similar-size females carried significantly lighter mud balls in denser-soil sites. Our results showed that the volume is the strongest factor limiting mud ball carrying. The effect of such limitations, moreover, may change depending on the physical properties of the material used for nest construction.
This paper aims to develop a new approach to interpret soil organic matter (SOM) dynamics from Rock-Eval pyrolysis. Rock-Eval standard parameters (TpS2, HI, OI) are limited when applied to SOM, as ...they were defined for tracking the origin of sedimentary organic matter (i.e. terrestrial vs aquatic and lacustrine vs marine). This study proposes new Rock Eval based indices, projected on a new diagram plotting >1300 samples, including litter and soil horizons, pure compounds and organic material. These new parameters reflect the thermal stability of SOM rather than its bulk chemistry. Their calculations are based on the contribution of four different areas (A1 to A4) integrated below the S2 pyrogram (amounts of released hydrocarbon compounds during the pyrolysis step). Results demonstrate that the relative values of A1 to A4 parameters can be used to survey the evolution of SOM during pedogenesis. These Rock-Eval parameters revealed a consistent thermal differentiation of SOM with depth, from thermally labile biogenic SOM in soil organic horizons to thermally stable mineral-associated SOM compounds in organo-mineral and mineral soil horizons, indicating a pedogenetic stabilization of SOM. Finally, newly defined I- and R-indices integrate the respective parts of A1 to A4 parameters into SOM dynamics, the I-index emphasizing the degree of transformation of the immature organic fraction (related to SOM stabilization), the R-index highlighting the contribution of the most refractory fraction or persistent SOM (related to pedogenic and inherited contributions). Analyses of a wide range of soils and reference samples (cellulose, lignin, humic substances, lignite, charcoal, coal, etc.) allow end-members as well as particular trends (humic, spodic, inherited) to be drawn. Specific examples are provided in order to illustrate some applications and uses for this new Rock-Eval based I/R diagram, from the study of grain size fractions to the evolution of SOM in soil chronosequences.
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•A novel Rock Eval pyrolysis diagram to interpret soil organic matter dynamics•The diagram is based on more than 1400 samples of litter, soil horizons, and pure compounds.•The new I-index refers to the degree of decomposition of immature SOM fractions.•The new R-index highlights the contribution of SOM refractory/persistent fractions.•Particular stabilization trends (humic, spodic, inherited) are emphasized in the IR diagram.
•Different soil units testify the succession of slope stability/instability phases.•Deciphering the complexity of soil polygenesis in high detail.•Rock-Eval® analysis enlighten the relationship ...between paleosols and organic matter.•Environmental conditions reconstruction based on soils and paleosols analysis.
Complex sequences of paleosols are often formed by the interaction between pedogenesis and geomorphological evolution. Their study, particularly in mountain areas, is useful to reconstruct past environmental conditions as well as climate shifts, and to gather information on the morphodynamical processes affecting the landscape through time.
Since the combined role that all different factors can play in the soil formation and evolution through time and space influences the formation and evolution of those complex paleosol sequences, a multidisciplinary study was conducted at the NW slope of Mt. Cusna (Northern Apennines, Italy). This work aims to reconstruct and to evaluate how the interactions between the geomorphological context, the Holocene climate variations, and the modification of the vegetation cover and composition influence the soil development of this area.
A combination of routine soil analyses (i.e., grain-size distributions, total organic carbon, total nitrogen, pH, and Fe/Al extractions), soil micromorphology and the Rock-Eval® pyrolysis allowed to characterize and to correlate the different soil units constituting a toposequence of six soil profiles.
The presence of different pedological units that can be correlated along the slope underlines the occurrence of separate events of pedogenesis, spatio-temporally linked to recognizable stability phases at slope scale. These phases of biostasy, characterized by vegetation cover and soil development, alternate to phases of rhexistasy, characterized mainly by slope instability (i.e., aggradation/degradation).
In detail, in the Mt. Cusna toposequence three different soil units, linked to three different stability phases, have been identified: the earliest stability phase, characterized by the presence of well-developed Luvisols, the subsequent stability phase typified by less expressed Luvisols, and the ongoing stability phase with Leptosols. This latter pedogenetic phase, in some cases, is superimposed to the previous one, so affecting the exhumed paleosols.
In this light, the Mt. Cusna toposequence characterization allowed to enlighten the complexity of soil polygenesis in higher detail than the previous studies, not only reconstructing the past environmental conditions but also inferring the succession of phases of slope stability and phases characterized by erosion and deposition processes.
Two chronosequences of deep red soils, located in Southern Fezzan, are described micromorphologically. The oldest member is probably Late Tertiary in age and has lateritoid characteristics. The ...intermediate member, of Middle Pleistocene age, displays moderate rubification and much illuvial clay. The most recent member, of Early Holocene age, has weak rubification and very little illuvial clay. The chronosequences of paleosols can be explained by pedogenesis in a humid pedoclimate on stable surfaces during the Quaternary.
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