Understanding the Oxidative Addition of sigma-Bonds to Group13 Compounds

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Understanding the reactivity of ion-encapsulated fullerenes

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Solos do topo da Serra São José (Minas Gerais) e suas relações com o paleoclima no Sudeste do Brasil Soils of the São José Hills (Minas Gerais State, Brazil) and their relationship with palaeoclimate in Southeastern Brazil

A diversidade de ecossistemas do sudeste do Brasil nem sempre pode ser relacionada com fatores edáficos, geomorfológicos ou hidrológicos. Topos de elevações, onde os solos são caracterizados pela unicidade de material de origem, podem constituir ambiente especial para estudos de gênese de solos e datações de eventos cíclicos relacionados com a dinâmica do clima regional. Depois de um levantamento detalhado de solos no topo da Serra São José (Prados - Minas Gerais), dois perfis de solo (P1 e P2), originados de metarenitos da Formação Tiradentes e caracterizados por deposições sucessivas de camadas arenosas alternadas com camadas arenosas enriquecidas com matéria orgânica, foram estudados, com intuito de encontrar testemunhos de paleoambientes. O pequeno platô localiza-se a 1.350 m acima do nível de mar e 350 m acima do nível topográfico regional dominante. No P1, foram identificadas trinta e três camadas enriquecidas com matéria orgânica, alternadas com camadas de areia. Três camadas no P1 (20-30, 70-80 e 100-110 cm), com conteúdo de C orgânico respectivamente de 0.5, 7 e 1 dag kg-1, apresentam idades radiocarbônicas < 40, 180 &plusmn; 60 e 350 &plusmn; 80 anos AP, respectivamente, e taxas de deposição de 0,177 cm ano-1 entre 110 e 70 cm e de 0,357 cm ano-1 entre 70 e 20 cm de profundidade. No P2, as camadas enriquecidas com matéria orgânica são mais espessas (entre 10 e 130 mm) e apresentam descontinuidades abruptas. Situam-se entre 20-30, 80-90, 110-120 e 170-180 cm de profundidade, têm um conteúdo de C orgânico de 3, 2.5, 21 e 1.5 dag kg-1 e idade radiocarbônica de 3580 &plusmn; 80, 3750 &plusmn; 80, 21210 &plusmn; 180 e 24060 &plusmn; 130 anos AP, respectivamente. Suas taxas de deposição são de 0,352 cm ano-1, entre 20 e 80 cm; de 0,002 cm ano-1, entre 80 e 110 cm, e de 0,021 cm ano-1, entre 110 e 170 cm de profundidade. Nos dois perfis, a relação C/N aumenta com a profundidade e com a idade das camadas. Os teores de Ti e Zr, elementos de baixa mobilidade, são mais elevados nas camadas mais antigas dos perfis, enquanto o Cu e o Pb concentram-se nas camadas mais ricas em matéria orgânica. Um fragmento de planta de 5 cm de diâmetro e 62 cm de comprimento, situado na base de P2, foi datado de 32220 &plusmn; 290 anos AP e relacionado com o início da gênese deste perfil. Os solos do topo da Serra São José são formados a partir de metarenitos da Formação Tiradentes, sem aporte de materiais de outra litologia. A água pluvial é o principal fator que adiciona energia a este ambiente, relacionando os atributos dos solos com o clima. P1 é um solo holocênico (Neossolo Flúvico Psamítico típico), formado a partir de deposições episódicas de areia, alternadas com material enriquecido com matéria orgânica. A formação de P2 (Paleossolo) iniciou-se no Pleistoceno, prolongou-se até o Holoceno e a morfologia de suas camadas enterradas de turfa relaciona-se com a oscilação do espelho d'água de uma lagoa, decorrente de fases mais secas e mais úmidas do clima. As idades radiocarbônicas encontradas estão relacionadas com alternâncias climáticas pleistocênicas e holocênicas em P2 e holocênicas em P1. O perfil P2 está situado em um local propício para realização de estudos palinológicos, com intuito de identificar ecótipos que ocuparam a área a partir do Pleistoceno tardio, relacionando-os com os paleoclimas.<br>The diversity of ecosystems in southeastern Brazil can not always be related to edaphic, geomorphologic, or hydrologic factors. Mountain summits, where soils are characterized by common parent material, offer a special environment for studies of soil genesis and dating of cyclic events related to regional climate dynamics. After a detailed investigation of soils from the São José Hills (Prados - Minas Gerais State, Brazil), two soil profiles (P1 and P2) originated from arenite of the Tiradentes Formation were studied. They are characterized by successive depositions of sandy layers alternated with layers of sand enriched with organic matter. The study site lies 1,350 m above sea level and 350 m above the dominant topographical level of the region. Thirty-three layers with organic matter, alternated with sand layers, were identified in P1. Three layers in P1 (20-30, 70-80, and 100-110 cm depth) with an organic C content of 0,5, 7, and 1 dag kg-1, respectively, present radiocarbon (14C) ages < 40, 180 &plusmn; 60, and 350 &plusmn; 80 years BP, respectively, and deposition rates of 0.177 cm year-1 at depths between 110 and 170 cm and of 0.357 cm year-1 between 70 and 20 cm layer. In P2, the layers enriched with organic matter are thicker (between 10 and 130 mm), with abrupt discontinuity. They lie between 20-30, 80-90 110-120, and 170-180 cm deep, have a C content of 3, 2.5, 21, and 1.5 dag kg-1, and a 14 C age of 3580 &plusmn; 80, 3750 &plusmn; 80, 21210 &plusmn; 180, and 24060 &plusmn; 130 year-1 BP, respectively. Their deposition rates are 0.352 cm year-1 between 20 and 80 cm, 0.002 cm year-1 between 80 and 110 cm and 0.021 cm year-1 at depths between 110 and 170 cm. In both soil profiles, the C/N ratio increases with depth and age. The amount of Ti and Zr, elements of low mobility, are higher in the oldest profile layers, while Cu and Pb are more concentrated in the layers higher in organic matter. A plant fragment (diameter 5 cm, 62 cm long) found at the bottom of P2 dated back to 32220 &plusmn; 290 years BP, and is associated with the beginning of this profile formation. The soils at the summit of São José Hills had its origin in the Tiradentes Formation without contribution of other geologic material. Rain water is the main factor that adds energy to this environmental energy. Therefore, soil formation is related to climate attributes. P1 is a holocenic (Fluvic Entisol) soil, formed by episodic depositions of sand, alternated with sand enriched with organic matter. The formation of P2 (Paleosol) began in the Pleistocene and lasted until the Holocene. The morphology of its buried peat layers is related to oscillations of the water surface of a lake, reflecting drier and more humid climate phases. The assessed radiocarbonic ages are related to Pleistocene and Holocene climate alternations in P2 and holocenic in P1. Profile P2 is an appealing site for palynological studies, where ecotypes that were present in the area beginning in the late Pleistocene can be identified and related to the palaeoclimates

A review of the world's soil museums and exhibitions

The soil science community needs to communicate about soils and the use of soil information to various audiences, especially to the general public and public authorities. In this global review article, we synthesis information pertaining to museums solely dedicated to soils or which contain a permanent exhibition on soils. We identified 38 soil museums specifically dedicated to soils, 34 permanent soil exhibitions, and 32 collections about soils that are accessible by appointment. We evaluate the growth of the number of museums since the early 1900s, their geographical distribution, their contents, and their attendance. The number of museums has been continuously growing since the early 1900s. A noticeable increase was observed from 2015 to 2019. Europe (in a geographical sense), Eastern and South-East Asia have the highest concentration of soil museums and permanent exhibitions related to soils. Most of the museums' attendance ranged from 1000 to 10,000 visitors per year. Russia has the largest number of soil monoliths exhibited across the world's museums, whereas the ISRIC-World Soil Museum has the richest and the most diverse collection of soil monoliths. Museums, collections, and exhibitions of soil play an important role in educating the population about this finite natural resource that maintains life on the planet, and for this reason, they must be increasingly supported, extended, and protected

A Review of the World’s Soil Museums and Exhibitions

The soil science community needs to communicate about soils and the use of soil information to various audiences, especially to the general public and public authorities. In this global review article, we synthesis information pertaining to museums solely dedicated to soils or which contain a permanent exhibition on soils. We identified 38 soil museums specifically dedicated to soils, 34 permanent soil exhibitions, and 32 collections about soils that are accessible by appointment. We evaluate the growth of the number of museums since the early 1900s, their geographical distribution, their contents, and their attendance. The number of museums has been continuously growing since the early 1900s. A noticeable increase was observed from 2015 to 2019. Europe (in a geographical sense), Eastern and South-East Asia have the highest concentration of soil museums and permanent exhibitions related to soils. Most of the museums’ attendance ranged from 1000 to 10,000 visitors per year. Russia has the largest number of soil monoliths exhibited across the world’s museums, whereas the ISRIC-World Soil Museum has the richest and the most diverse collection of soil monoliths. Museums, collections, and exhibitions of soil play an important role in educating the population about this finite natural resource that maintains life on the planet, and for this reason, they must be increasingly supported, extended, and protecte