Ball milling of mackinawite and oxalic acid to fabricate an efficient and stable reductive material for remediation of Cr(Ⅵ)-contaminated soil.

Environmental geochemistry is a major branch of regional geochemistry. In this thesis are presented the environmental geochemical investigation of Campania Plain and Naples and Salerno Gulfs in South Italy, concerning potential toxic elements and organic compounds distribution. Multivariate and univariate analysis are used to illustrate distribution and sources of elements and organic compounds, both on land and in sea sediments for Naples and Salerno Gulfs. Different pollution impact factors and risk assessment factors are estimated for soils and sediments that easily comes to contact with human beings. The results suggest that Naples city territory, and Naples and Pozzuoli Gulfs are characterized by highly incremental lifetime cancer risk. An attempt of applying in situ Raman spectroscopic detection of pollutants started with a series of laboratory experiments. With the help of capillary high pressure optical cell, following results are achieved: 1) methane diffusion coefficients in water under high pressure and wide temperature range, and the relationship of diffusion coefficients with temperature was established; 2) Raman intensity ratio of asymmetric stretching vibration (ν3) and asymmetric bending overtone (2ν2) of methane were numerically described vs temperature, pressure and gas phase density; 3) reactions of goethite and magnetite with sulfide solutions under CH4 and/or CO2 atmospheres were monitored at room temperature. Pyrrhotite and mackinawite were observed in final products. A demanding of innovative approach to detect organic contaminants encourages various researches to improve in-situ techniques. A new substrate embedding silver nanoparticles into siloxane polymer is used as the platform to generate Surface-Enhanced Raman Scattering (SERS). Polymer serves as supporting material of silver nanoparticles as well as a stationary phase. After a short period of extraction, certain partition of organic compounds from aqueous solution accumulates into polymer. When silver nanoparticles is in touch with organic compounds, enhanced Raman scattering is obtained with 104~106 orders of magnitude. Raman scattering is obtained. Because of these two-steps amplification, SERS, which is typical applied strictly at lab condition, could be compromised when applied for field survey. Crystal violet (CV) is chosen to evaluate extraction properties of polymer. Color “transferring” indicates effective extraction of crystal violet into polymer. Intensive Raman bands include SERS effects and resonance scattering of CV. Low concentration of 4-nitrophenol (PNP) and 4-nitroaniline (PNA) in solution (as low as 10-7 M) are dropped onto substrate and generate SERS fingerprint. After subtracting Raman bands of polymer and silver salts, clear evidence indicates availability of macro SERS spectra. Micro SERS testifies compounds penetrating as depth as 200 µm from the surface.

The Serbo-Macedonian Metallogenetic Province, part of the Alpine metallogenic belt, hosts several ore deposits in mainly three geotectonic units: the Vardar Zone, the Serbo-Macedonian massif, and to a lesser extend the Dinarides. This metallogenic province includes the most significant Pb-Zn and Sb deposits in Serbia, as well as smaller Bi, Mo, Cu, Fe, Sn, Au and minor U, Wand Hg deposits, which are genetically related to emplacement of granitoids. The Podrinje Metallogenic District belongs to the Serbo-Macedonian Metallogenetic Province and incorporates several smaller orefields: Cer (Northwest Serbia), Boranja (West Serbia), and Srebrenica (East Bosnia and Herzegovina). Polymetallic deposits in the Boranja orefield are genetically related to the emplacement of the Tertiary Boranja granodiorite complex. The orefield contains a large number of sulfide deposits with Pb-Zn, and Sb with subordinate Cu, As, Bi and Ag. Small magnetite deposits connected to pyrometasomatic (skarn) stage are also significant. Skarns are of calcic type, and were formed along contacts of Triassic limestones and quartz diorites. Ore minerals are similar among the various types of orebodies in the Boranja orefield and consist of sulfides, sulfosalts [Pb-Bi-(Ag)-Te-Cu, Pb-Sb-(As), Sb-Cu-(Ag, Fe, Zn)], tellurides, native metals and alloys, oxides and complex-oxides, and gangue minerals. Minerals of the Boranja orefield were formed in several successive stages, which together correspond to a single regional-scale mineralization event that is genetically related to the subvulcanic-plutonic intrusion of the Neogene-aged magmatic Boranja complex. This can be best demonstrated by the zonal arrangement of several metallic mineral associations [Fe-Cu(Bi) -> Pb(Ag)-Zn -> Sb(As) -> CaF2(Pb-Zn)], with increasing distance from the Boranja granodiorite. Silver occurs as a minor metal principally as Ag-tetrahedrite, with subordinate native silver, Ag-bearing gold and pyrargyrite. Significant quantities of Ag can also be accommodated in galena as it is found to contain varied amounts of Ag, Bi and Sb (0.001-0.936, 0-3.345, and 0.012-0.510 wt%, respectively). The presence of both Ag and Bi in significant amounts in a Pb-rich sulfide system is essential for development of galena [solid solution alpha-(Pb-2, AgSb, AgBi)S-2]. This study demonstrates that silver, the most economic metal in Boranja orefield, is mainly accommodated in the galena structure, with lesser amounts present in the form of visible and/or invisible Pb-Bi-(Ag) sulfosalts.

A coupled study of sulphide mineralogy and chalcophile/ siderophile elements geochemistry (i.e., S, Se, Cu, As, V, Cd, Co, Zn, platinum-group elements and Au) has been undertaken in abyssal peridotites from the MARK area. The 28 samples analysed were mostly collected by submarine along the southern wall of the Kane transform fault. Compared to the peridotites drilled in the same area, our samples show a wide range of modal compositions (lherzolites, cpx-poor lherzolites and harzburgites) and of bulk-rock chemistry (1.5 1.85; SmN/YbN up to 1.4, N= chondrite normalized). Lherzolites and cpx-poor lherzolites show coarsergrained isolated cpx crystals in addition to the smaller cpx forming cpx+opx±sp clusters. These coarse-grained cpx are ascribed to in-situ precipitation of clinopyroxene from partial melts (Seyler et al., in prep.). Sulphides of indisputable magmatic origin have been observed in all of the peridotites. In spite of sea-water alteration and serpentinization, the number of magmatic sulphide grains positively correlates with fertility in the residual samples, decreasing from 1.2-3.7 grains/cm2 in the lherzolites to less than 0.5 grain/cm2 in the most refractory harzburgites. These latter still contain residual sulphides which provides further hypothesis of immiscible sulphide persisting in the mantle source of MORB-melts. Magmatic sulphides are closely associated with the small clusters-forming cpx crystals, being either enclosed or forming discrete grains adjacent to this silicate. In the weathered samples, magmatic sulphides are totally replaced by hydrous iron hydroxides (limonites) whereas the samples free from weathered products preserved sulfide assemblages typical of the reducing conditions generated by low T-serpentinization (i.e. Fe-rich pentlandite + magnetite ± mackinawite ± digenite ± troilite ± awaruite). Nevertheless, the peridotites refertilized by exotic MORB-type magmas display systematic sulphide enrichments (up to 5 grain/cm2) with respect to the sulphide vs. fertility correlation documented in the residual samples. Sulphides preferentially occur along or within the grain boundaries of the coarse-grained cpx. Similar sulphide enrichments have been observed in a few residual cpx-poor lherzolites devoid of melt/rock reaction evidence; however sulphides are disseminated within the serpentinized matrix at distance from the cpx. Clearly, several sulphide precipitation mechanisms operated in the oceanic mantle sampled by the Kane transform fault. The contents of moderately chalcophile elements (Cu, Zn, V, Co, Cd) and chalcogenides (S, Se, As) have been variably upgraded by sea-floor alterations. Weathered samples are systematically enriched compared to typical mantle compositions (up to 265 ppb Se; 200-400 ppm S with 2 occasional peaks at 2,000 ppm; up to 60 ppm As; up to 120 ppm Cu). None of the moderately chalcophiles positively correlates with the number of sulphide grains per polished thin sections and correlations with fertility indices are poor. By contrast, positive correlations such as Cu vs. Se, As vs. Se; Cu vs. As; Cd vs. Se and Zn vs. Cu suggest that these elements were contaminated by fluids from hydrothermal vents. However, apart from the weathered samples, S, Se as well as numerous moderately chalcophiles still show concentration ranges plotting on mantle melting trends. Some lherzolites display sub-chondritic S/Se ratios (~2,800) and Se and S contents that fit the range of oceanic mantle compositions recomputed from primitive MORBs (~200 ppm S; ~80 ppb Se). Gold contents (0.8-5 ppb) are almost systematically higher than mantle abundances, probably because of contaminations from hydrothermal vents. This element poorly correlates with indicators of melt depletion or magmatic sulphide precipitation. On the contrary, platinum-group elements were mostly insensitive to hydrothermal alterations, whether serpentinization or sea-floor weathering. Weathered and unweathered peridotites display PGE concentration ranges typical of mantle rocks (2-4 ppb Os, 2-4 ppb Ir; 4-8 ppb Ru; 0.7-1.4 ppb Rh; 3-9 ppb Pt; 0.2-8 ppb Pd). These concentration range are not affected by the alteration of magmatic sulphides into iron hydroxides. Strongly serpentinized harzburgites are the poorest in PGEs, perhaps because of the well-known diluting effect of serpentinization on trace elements. CI-chondrites normalized PGE patterns are similar to those reported for on-land unserpentinized mantle rocks, ranging from nearly flat to slightly fractionated. Compatible PGEs (Os, Ir, Ru and Rh) were not affected by partial melting or melt/rock reactions as their concentration ranges are uncorrelated with petrogenetic indicators of these processes. Os/Ir ratio is within the range of chondrites (0.9-1.2) whereas Ru/Ir and Rh/Ir are slightly higher than chondritic (1.7-2.3 and 0.3-0.4, respectively). Our sample provide further evidence that compatible PGEs are not extracted from the mantle as long as residual sulphides survive in partial melting residues. Pt Pd systematics are more variable. The most refractory harzburgites preserve negatively-trending chondrite normalized PGE patterns (0.7<PtN/IrN<1.1; 0.3<PdN/IrN<0.5). Even in S-saturated conditions, the most incompatible PGEs are more readily extracted than compatible PGEs from the oceanic mantle; however, Pt was less systematically fractionated than Pd. The lherzolites and cpx-poor lherzolites show Pt/Ir and Pd/Ir varying in a rather complex way, especially the cpx-poor lherzolites that show the largest scatter of PdN/IrN (0.2-2.2). The samples refertilized by exotic MORB-type melts have been enriched in all the PGE by sulphide precipitation. However, their PGE patterns are typical of residual mantle rocks (i.e. lower-than-chondritic PdN/IrN (0.2-1). Where sulphides precipitated during in-situ fractional crystallization of partial melts, the samples show suprachondritic PdN/IrN (1.6-2.0) and PtN/IrN (1-1.2). Their PGE patterns is complementary to those of the refractory harzburgites and their PGE contents do not correlate with sulphide modal abundance or in-situ precipitated coarse cpx crystals. As documented in other abyssal peridotites (Hess Deep (Leg 895), Kane fracture zone (Leg 920), .i.e. Rehkamper et al., 1998), PGE systematics of abyssal peridotites are not fully explained by considering these rocks as simple mantle melting residues. Complex melt/rock reaction processes and coupled sulphide precipitation are to be considered to explain the large scatter of Pd/Ir and Pt/Ir. Preliminary in situ LA-ICPMS data on sulphides suggest the same variability between each sulphide grain. However, segregation of immiscible sulphide liquids does not necessarily yield supra-chondritic Pd/Ir and Pt/Ir ratios. Incomplete sulphide-silicate equilibration as well as mechanical transport of sulphides by silicate melts have to be taken into account to interpret these ratios.

On the conversion of mackinawite to greigite

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