In vitro effects of metals on the acid phosphatase from the microalgae Pseudokirchneriella subcapitata.

2008

Initial growth of sunflower in soils with high concentrations of boron and heavy metals.

2008

Assessment of heavy metals in soils of a vineyard region with the use of principal component analysis.

Agricultural management with chemicals may contaminate the soil with heavy metals. The objective of this study was to apply Principal Component Analysis and geoprocessing techniques to identify the origin of the metals Cu, Fe, Mn, Zn, Ni, Pb, Cr and Cd as potential contaminants of agricultural soils. The study was developed in an area of vineyard cultivation in the State of São Paulo, Brazil. Soil samples were collected and GPS located under different uses and coverings. The metal concentrations in the soils were determined using the DTPA method. The Cu and Zn content was considered high in most of the samples, and was larger in the areas cultivated with vineyards that had been under the application of fungicides for several decades. The concentrations of Cu and Zn were correlated. The geoprocessing techniques and the Principal Component Analysis confirmed the enrichment of the soil with Cu and Zn because of the use and management of the vineyards with chemicals in the preceding decades.

Additive Manufacturing by LPBF and WAAM of metals: correlation between production process, microstructure and mechanical properties

In the most recent years, Additive Manufacturing (AM) has drawn the attention of both academic research and industry, as it might deeply change and improve several industrial sectors. From the material point of view, AM results in a peculiar microstructure that strictly depends on the conditions of the additive process and directly affects mechanical properties. The present PhD research project aimed at investigating the process-microstructure-properties relationship of additively manufactured metal components. Two technologies belonging to the AM family were considered: Laser-based Powder Bed Fusion (LPBF) and Wire-and-Arc Additive Manufacturing (WAAM). The experimental activity was carried out on different metals of industrial interest: a CoCrMo biomedical alloy and an AlSi7Mg0.6 alloy processed by LPBF, an AlMg4.5Mn alloy and an AISI 304L austenitic stainless steel processed by WAAM. In case of LPBF, great attention was paid to the influence that feedstock material and process parameters exert on hardness, morphological and microstructural features of the produced samples. The analyses, targeted at minimizing microstructural defects, lead to process optimization. For heat-treatable LPBF alloys, innovative post-process heat treatments, tailored on the peculiar hierarchical microstructure induced by LPBF, were developed and deeply investigated. Main mechanical properties of as-built and heat-treated alloys were assessed and they were well-correlated to the specific LPBF microstructure. Results showed that, if properly optimized, samples exhibit a good trade-off between strength and ductility yet in the as-built condition. However, tailored heat treatments succeeded in improving the overall performance of the LPBF alloys. Characterization of WAAM alloys, instead, evidenced the microstructural and mechanical anisotropy typical of AM metals. Experiments revealed also an outstanding anisotropy in the elastic modulus of the austenitic stainless-steel that, along with other mechanical properties, was explained on the basis of microstructural analyses.

Plutarch's chemistry of stones and metals: conceptions and explanations. With an appendix on the TheSu XML annotation scheme

This dissertation presents a systematic and analytic overview of most of the information related to stones, minerals, and stone masonry which is found in the corpus of Plutarch of Chaeronea, combined with most of the information on metals and metalworking which is connected to the former. This survey is intended as a first step in the reconstruction of the full landscape of ‘chemical’ ideas occurring in Plutarch’s writings; accordingly, the exposition of the relevant passages, the assessment of their possible interpretations, the discussion on their implications, and their contextualization in the ancient traditions have been conducted with a special interest in the ‘mineralogical’ and ‘metallurgic’ themes developed in the frame of natural philosophy and meteorology. Although in this perspective physical etiology could have come to acquire central prominence, non-etiological information on Plutarch’s ideas on the nature and behaviour of stones and metals has been treated as equally relevant to reach a fuller understanding of how Plutarch conceptualized and visualized them in general, in- and outside the frame of philosophical explanation. Such extensive outline of Plutarch’s ideas on stones and metals is a prerequisite for an accurate inquiry into his use of the two in analogies, metaphors, and symbols: to predispose this kind of research was another aim of the present survey, and this aim has contributed to shape it; moreover, a special attention has been paid to the analysis of analogical and figurative speaking due to the nature itself of a large part of Plutarch’s references to stones and metals, which are either metaphorical, presented in close association with metaphors, or framed in analogies. Much of the information used for the present overview has been extracted —always with supporting argumentation— from the implications of such metaphors and analogies.

Nature in the books of seven metals – Ǧābirian corpus in dialogue with ancient Greek philosophy and Byzantine alchemy –

The Ǧābirian corpus was a receiver of ancient Greek ideas and, at the same time, a source of knowledge for the later Greek-speaking world, in particular for medieval Byzantine alchemy. Both aspects are explored in the dissertation with respect to the notion of nature. After a general introduction to the Corpus and the sciences described in it, particular attention is devoted to a Byzantine anonymous text, The Work of Four Elements, which was probably influenced by the Ǧābirian Books of Seventy. These texts exemplify how, in the theory of the Ǧābirian science, things are constructed from four natures (hot, cold, moist and dry), the balance of which defines what a thing is. By changing the balance of natures, one can transmute any metals into gold that is perfectly proportioned in terms of natures. Ǧābir presents the art of dyeing metals gold in the Books of Seven Metals which, along with chrysopoetic recipes, also include medical recipes and theoretical contents such as the theories of four humours, properties, and talismans. Moreover, Ǧābir postulated a substrate that does not change in itself and continues to exist when natures move in and out of things. Such primary existence is called the fifth nature as an additional principle to the four natures. This key concept for the Ǧābirian theory, which has been underexplored so far, is discussed through the textual and critical analysis of various unedited sources: the Books of Seven Metals and the Book of the Fifth Nature. This study confirms that the fifth nature was probably derived from ancient Greek philosophical concepts such as the Empedoclean particles, the Aristotelian fifth element and the Stoic pneuma. Thus, this research indicates the importance of the Ǧābirian corpus both in the history of alchemy and the history of philosophy.

Green approach to Palladium Cross-Coupling reactions and development of new methodologies based on highly abundant metals

Transition metal catalyzed cross-coupling reactions represent among the most versatile and useful tools in organic synthesis for the carbon-carbon (C-C) bond formation and have a prominent role in both the academic and pharmaceutical segments. Among them, palladium catalyzed cross-coupling reactions are currently the most versatile. In this thesis, the applications, impact and development of green palladium cross-coupling reactions are discussed. Specifically, we discuss the translation of the Twelve Principles of Green Chemistry and their applications in pharmaceutical organometallic chemistry to stimulate the development of cost-effective and sustainable catalytic processes for the synthesis of active pharmaceutical ingredients (API). The Heck-Cassar-Sonogashira (HCS) and the Suzuki-Miyaura (SM) protocols, using HEP/H2O as green mixture and sulfonated phosphine ligands, allowed to recycle and recover the catalyst, always guaranteeing high yields and fast conversion under mild conditions, with aryl iodides, bromides, triflates and chlorides. No catalyst leakage or metal contamination of the final product were observed during the HCS and SM reactions, respecting the very low limits for metal impurities in medicines established by the International Conference of Harmonization Guidelines Q3D (ICH Q3D). In addition, a deep understanding of the reaction mechanism is very important if the final target is to develop efficient protocols that can be applied at industrial level. Experimental and theoretical studies pointed out the presence of two catalytic cycles depending on the counterion, shedding light on the role of base in catalyst reduction and acetylene coordination in the HCS coupling. Finally, the development of a cross-coupling reaction to form aryldifluoronitriles in the presence of copper is discussed, highlighting the importance of inserting fluorine atoms within biological structures and the use of readily available metals such as copper as an alternative to palladium.

Rhodium clusters: investigation of the reactivity towaeds phosphines and selected d- and p-metals

During my PhD we focused on different research projects concerning the synthesis and characterization of new rhodium carbonyl clusters. More specifically, we studied the reactivity between Rh4(CO)12 and different bidentate phosphines, obtaining seven different species: Rh4(CO)10(dppe), Rh4(CO)8(dppe)2, Rh4(CO)10(dppf), {Rh4(CO)10(dpp-hexane)}2, {Rh4(CO)10(t-dppe)}2, Rh2(CO)2(dppf)2 and Rh4(CO)9(μ2-dppe)(μ1-dppeO). The reactivity of [Rh7(CO)16]3- with [AuCl4]- and Au(Et2S)Cl led to the formation of seven bimetallic clusters, of which four new ones, namely [Rh16Au6(CO)36]6-, [Rh10Au(CO)26]3-, [Rh16Au6(CO)36]4-, [Rh16Au6(CO)36]5-, [Rh22Au3(CO)47]5-, [Rh19Au5(CO)40]4- and [Rh20Au7(CO)45]5-. The reactivity of [Rh16Au6(CO)36]6- and [Rh10Au(CO)26]3- was studied as well. The reactivity of [Rh7(CO)16]3- with AgBF4, AgNO3 and with Pt(Et2S)2Cl2 was investigated, yielding only to the already known [Rh6N(CO)15]-, [PtRh5(CO)15]- and [PtRh4(CO)14]2- compounds. [Rh7(CO)16]3- war reacted with SnCl2·2H2O in acetone obtaining [Rh7Sn4Cl10(CO)14]5-, and [Rh12Sn(CO)23Cl2]4- was reacted with H+ obtaining [Rh18Sn3Cl2(CO)44]4-. Reactivity of [Rh7(CO)16]3- with InCl3 resulted in the isolation of [Rh12In(CO)28]3- and [Rh11In3(CO)25Cl2]3-, already known in our research lab, and the new [HRh11In(CO)26]3-. Moreover, a more straightforward synthesis for [Rh6InCl3(CO)15]2- was found, and this also led to the isolation of the [Rh6InCl2(DMF)(CO)15]-. The recover or rhodium as valuable carbonyl compound was also studied, and starting from a mixture of by-products it was possible to obtain the starting material [Rh7(CO)16]3-.

Heavy Metals distribution in drainage canals sediments of the Ravenna province

This work, in collaboration with the Romagna Reclamation Consortium, has the aim of studying the heavy metals concentration distribution in the drainage canals of the Ravenna coastal basins, Italy. Particular attention was given to the area of the V Fosso Ghiaia and VI Bevanella basins, where water and sediment samples were collected in the field and integrated with existing databases. The hydrological regime is controlled and managed by the Consortium, which has divided the territory into several mechanical drainage basins. XRF was performed on 21 sediment samples and pH, EC, T°, Fe2+ and Fetot were measured on 15 water samples by probes and spectrophotometer, respectively. Heavy metals concentrations exceeding legal limits of the D.LGS n ° 152/2006 were found for As, Co, Cr, Pb and Zn. These results were then integrated with canal sediment analyses provided by the Consortium to perform a Principal Component Analysis. PCA results show that the main variable affecting heavy metals distribution is the use of fertilizers, followed by distance from sea, and altimetry, which are directly linked to salinity. Heavy metals concentrations increase with increasing use of fertilizers, which are mainly due to the widespread agricultural practices and industrial land use in the area. High heavy metals concentrations are also found in the canals interested by higher salinity (especially Pinetale Ramazzotti). In fact, the area is affected by salinization caused by a water table below sea level and upward seepage of salty oxygen-poor saline water from the bottom of the aquifer. According to the literature, iron and manganese oxides were found to be an important factor in controlling the heavy metals distribution.

Changes In The Bacterial Community Of Soil From A Neutral Mine Drainage Channel.

Mine drainage is an important environmental disturbance that affects the chemical and biological components in natural resources. However, little is known about the effects of neutral mine drainage on the soil bacteria community. Here, a high-throughput 16S rDNA pyrosequencing approach was used to evaluate differences in composition, structure, and diversity of bacteria communities in samples from a neutral drainage channel, and soil next to the channel, at the Sossego copper mine in Brazil. Advanced statistical analyses were used to explore the relationships between the biological and chemical data. The results showed that the neutral mine drainage caused changes in the composition and structure of the microbial community, but not in its diversity. The Deinococcus/Thermus phylum, especially the Meiothermus genus, was in large part responsible for the differences between the communities, and was positively associated with the presence of copper and other heavy metals in the environmental samples. Other important parameters that influenced the bacterial diversity and composition were the elements potassium, sodium, nickel, and zinc, as well as pH. The findings contribute to the understanding of bacterial diversity in soils impacted by neutral mine drainage, and demonstrate that heavy metals play an important role in shaping the microbial population in mine environments.

Geochemistry Of Acid Mine Drainage From A Coal Mining Area And Processes Controlling Metal Attenuation In Stream Waters, Southern Brazil.

Acid drainage influence on the water and sediment quality was investigated in a coal mining area (southern Brazil). Mine drainage showed pH between 3.2 and 4.6 and elevated concentrations of sulfate, As and metals, of which, Fe, Mn and Zn exceeded the limits for the emission of effluents stated in the Brazilian legislation. Arsenic also exceeded the limit, but only slightly. Groundwater monitoring wells from active mines and tailings piles showed pH interval and chemical concentrations similar to those of mine drainage. However, the river and ground water samples of municipal public water supplies revealed a pH range from 7.2 to 7.5 and low chemical concentrations, although Cd concentration slightly exceeded the limit adopted by Brazilian legislation for groundwater. In general, surface waters showed large pH range (6 to 10.8), and changes caused by acid drainage in the chemical composition of these waters were not very significant. Locally, acid drainage seemed to have dissolved carbonate rocks present in the local stratigraphic sequence, attenuating the dispersion of metals and As. Stream sediments presented anomalies of these elements, which were strongly dependent on the proximity of tailings piles and abandoned mines. We found that precipitation processes in sediments and the dilution of dissolved phases were responsible for the attenuation of the concentrations of the metals and As in the acid drainage and river water mixing zone. In general, a larger influence of mining activities on the chemical composition of the surface waters and sediments was observed when enrichment factors in relation to regional background levels were used.

Bacterial Diversity Assessment In Soil Of An Active Brazilian Copper Mine Using High-throughput Sequencing Of 16s Rdna Amplicons.

Mining activities pose severe environmental risks worldwide, generating extreme pH conditions and high concentrations of heavy metals, which can have major impacts on the survival of organisms. In this work, pyrosequencing of the V3 region of the 16S rDNA was used to analyze the bacterial communities in soil samples from a Brazilian copper mine. For the analysis, soil samples were collected from the slopes (geotechnical structures) and the surrounding drainage of the Sossego mine (comprising the Sossego and Sequeirinho deposits). The results revealed complex bacterial diversity, and there was no influence of deposit geographic location on the composition of the communities. However, the environment type played an important role in bacterial community divergence; the composition and frequency of OTUs in the slope samples were different from those of the surrounding drainage samples, and Acidobacteria, Chloroflexi, Firmicutes, and Gammaproteobacteria were responsible for the observed difference. Chemical analysis indicated that both types of sample presented a high metal content, while the amounts of organic matter and water were higher in the surrounding drainage samples. Non-metric multidimensional scaling (N-MDS) analysis identified organic matter and water as important distinguishing factors between the bacterial communities from the two types of mine environment. Although habitat-specific OTUs were found in both environments, they were more abundant in the surrounding drainage samples (around 50 %), and contributed to the higher bacterial diversity found in this habitat. The slope samples were dominated by a smaller number of phyla, especially Firmicutes. The bacterial communities from the slope and surrounding drainage samples were different in structure and composition, and the organic matter and water present in these environments contributed to the observed differences.

Bile And Liver Metallothionein Behavior In Copper-exposed Fish.

The present study analyzed metallothionein (MT) excretion from liver to bile in Nile Tilapia (Oreochromis niloticus) exposed to sub-lethal copper concentrations (2mgL(-1)) in a laboratory setting. MTs in liver and bile were quantified by spectrophotometry after thermal incubation and MT metal-binding profiles were characterized by size exclusion high performance liquid chromatography coupled to ICP-MS (SEC-HPLC-ICP-MS). Results show that liver MT is present in approximately 250-fold higher concentrations than bile MT in non-exposed fish. Differences between the MT profiles from the control and exposed group were observed for both matrices, indicating differential metal-binding behavior when comparing liver and bile MT. This is novel data regarding intra-organ MT comparisons, since differences between organs are usually present only with regard to quantification, not metal-binding behavior. Bile MT showed statistically significant differences between the control and exposed group, while the same did not occur with liver MT. This indicates that MTs synthesized in the liver accumulate more slowly than MTs excreted from liver to bile, since the same fish presented significantly higher MT levels in liver when compared to bile. We postulate that bile, although excreted in the intestine and partially reabsorbed by the same returning to the liver, may also release MT-bound metals more rapidly and efficiently, which may indicate an efficient detoxification route. Thus, we propose that the analysis of bile MTs to observe recent metal exposure may be more adequate than the analysis of liver MTs, since organism responses to metals are more quickly observed in bile, although further studies are necessary.

A Comparison Between Characterization And Biological Properties Of Brazilian Fresh And Aged Propolis.

As propolis is a highly valued bee product, we aimed to verify the quality of aged propolis, investigating their phenolic and flavonoid composition, levels of toxic metals, radical scavenging and antimicrobial activities. Samples of fresh and aged propolis of six different beekeepers, from the same geographical location, were investigated in terms of their phenolic and flavonoid composition and levels of Pb, Cd, and Cr, as well as radical scavenging and antimicrobial activities. The two groups of propolis had similar qualitative composition by HPLC-PDA and ESI(-)-MS. Fresh propolis and aged propolis show no differences when average values of extraction yield, flavonoids, EC50, or MIC were compared and both types of propolis showed good antimicrobial activity at low concentrations. Only levels of phenolic compounds were higher in fresh propolis. The propolis samples considered in this study, aged or fresh, had similar qualitative composition, although they were collected in different periods. Samples only differed in their levels of total phenolic content. Moreover, aged propolis conserves significant radical scavenging and antimicrobial properties. We suggest that aged propolis should not be discarded but explored for alternative applications.