Massimiliano Melchiorre

Geophysical‐petrological model of the crust and upper mantle in the India‐Eurasia collision zone

We present a new crust and upper mantle cross section of the western India-Eurasia collision zone by combining geological, geophysical, and petrological information within a self-consistent thermodynamic framework. We characterize the upper mantle structure down to 410 km depth from the thermal, compositional, and seismological viewpoints along a profile crossing western Himalayan orogen and Tibetan Plateau, Tarim Basin, Tian Shan, and Junggar Basin, ending in the Chinese Altai Range. Our results show that the Moho deepens from the Himalayan foreland basin (~40 km depth) to the Kunlun Shan (~90 km depth), and it shallows to less than 50 km beneath the Tarim Basin. Crustal thickness between the Tian Shan and Altai mountains varies from ~66 km to ~62 km. The depth of the lithosphere-asthenosphere boundary (LAB) increases from 230 km below the Himalayan foreland basin to 295 km below the Kunlun Shan. To NE the LAB shallows to ~230 km below the Tarim Basin and increases again to ~260 km below Tian Shan and Junggar region and to ~280 km below the Altai Range. Lateral variations of the seismic anomalies are compatible with variations in the lithospheric mantle composition retrieved from global petrological data. We also model a preexisting profile in the eastern India-Eurasia collision zone and discuss the along-strike variations of the lithospheric structure. We confirm the presence of a noticeable lithospheric mantle thinning below the Eastern Tibetan Plateau, with the LAB located at 140 km depth, and of mantle compositional differences between the Tibetan Plateau and the northern domains of Qilian Shan, Qaidam Basin, and North China.

Relationship between particle density and soil bulk chemical composition

PurposeAn analytical database containing XRF chemical analyses and real density measurements of unconsolidated sediments of the Padania Plain (Northern Italy) has been used to understand the relationship that exists between the soil particle density (ρs) and their bulk chemical composition.Materials and methodsUsing a linear regression, we built an equation able to link the particle density with the soil elemental composition.Results and discussionPositive correlations were found between ρs and SiO2, MgO, CaO and Na2O and negative correlations with K2O, TiO2, Al2O3, Fe2O3 and LOI, reflecting the presence in the soils of quartz and feldspars/mineral clays respectively.ConclusionsOur equation is very useful because it helps to know the density properties of a soil when it is not possible to measure ρs with a pycnometer. On the other hand, by knowing the ρs, it is possible to have a quite precise knowledge about the chemistry of the studied soils.

Particle density distribution in a fluvial floodplain

The mechanisms that determine the formation of a floodplain are very well known. At the same time, there is an established correspondence between the sedimentary deposits and density of the particles, whose distribution in the plain is until now poorly constrained. In this work we therefore highlight the spatial distribution of the particle density of soils from the Padania Po Plain in relation to the depositional sub-environment where they have been sampled.

On the potential effect of micronized zeolites on seed germination: a prospective study

It is well known that zeolite yields positive effects to seed germination. However, any previous study has so far highlighted how the zeolite interacts with the seeds. The goal of this paper is to assess the effect of zeolite on radish seed germination by means of X-ray spectrometric methods. As starting assumption, we hypothesize that the micronized zeolite mixed with water may try to break the seeds husk and allow the water to enter the seed. X-Ray diffraction and Energy Dispersive X-Ray Spectroscopy coupled with Scanning Electron Microscope were chosen to investigate seeds of radish that were previously treated with or without micronized natural zeolite. The results show that zeolite grains on the surface of the seed cannot penetrate its husk, implying that there is no risk of zeolite accumulation within the tissues of the plant’s embryo. In addition, this study highlights that SEM-EDX is the most effective analytical tool to investigate the interaction between mineral compounds (e.g. zeolite) and organic matrices such as the seeds.

Textural changes and heavy metal distribution in sediments after decontamination treatment by soil washing and attrition scrubber

PurposeThe study was aimed to provide information on the decontamination of sediments polluted with heavy metals by soil washing and attrition scrubber techniques, assessing the efficiency of a prototype machinery for the improvement of sediment quality dredged in the Ravenna Harbor (Italy). An additional purpose was to compare the heavy metal distribution in sediment fractions collected after these treatments.Materials and methodsTextural and geochemical characteristics were determined in bulk sediments and after the treatments of soil washing and attrition scrubbing by a smaller scale prototype. Statistical analyses were carried out to verify the heavy metal correlations at each step of the treatments.Results and discussionTextural features after treatments showed moderate separation of sand and silt/clay fractions after soil washing and an increase of the fine fractions after attrition scrubbing. Bulk sediments polluted by arsenic (As) were decontaminated after treatments. Concerning heavy metals, mercury was concentrated in the sand while aluminum, As, cadmium, chrome, iron, manganese, zinc, and vanadium were concentrated in the silt/clay fraction. Bivariate plots showed a significant correlation of heavy metals with sand percentage after soil washing and attrition scrubbing.ConclusionsThe results suggest that heavy metal concentrations were significantly affected by grain size distribution. Soil washing resulted in the complete decontamination of As in the sediments. The heavy metal concentration was altered in each step of the treatments according to three different trends.

Effects of middle-term land reclamation on nickel soil-water interaction: a case study from reclaimed salt marshes of Po River Delta, Italy

Reclaimed salt marshes are fragile environments where water salinization and accumulation of heavy metals can easily occur. This type of environment constitutes a large part of the Po River Delta (Italy), where intensive agricultural activities take place. Given the higher Ni background of Po River Delta soils and its water-soluble nature, the main aim of this contribution is to understand if reclamation can influence the Ni behavior over time. In this study, we investigated the geochemical features of 40 soils sampled in two different localities from the Po River Delta with different reclamation ages. Samples of salt marsh soils reclaimed in 1964 were taken from Valle del Mezzano while soils reclaimed in 1872 were taken nearby Codigoro town. Batch solubility tests and consecutive determination of Ni in pore-water were compared to bulk physicochemical compositions of soils. Bulk Ni content of the studied soils is naturally high, since these soils originated from Po River sediments derived from the erosion of ultramafic rocks. Moreover, it seems that Ni concentration increases during soil evolution, being probably related to the degradation of serpentine. Instead, the water-soluble Ni measured in the leaching tests is greater in soils recently reclaimed compared to the oldest soils. Soil properties of two soil profiles from a reclaimed wetland area were examined to determine soil evolution over one century. Following reclamation, pedogenic processes of the superficial horizons resulted in organic matter mineralization, pH buffer, and a decrease of Ni water solubility from recently to evolved reclaimed soil.