Mineralogia e geoquímica de perfis de solo com Terra Preta Arqueológica de Bom Jesus do Tocantins, sudeste da Amazônia

Abstract

A comparação de dados morfológicos, mineralógicos e químicos de solo com horizontes antrópicos -Terra Preta Arqueológica (TPA) com Argissolos adjacentes permitiu identificar os principais processos responsáveis pela formação da TPA em um sítio arqueológico no Município de Bom Jesus do Tocantins, sudeste do Estado do Pará. A similaridade entre os dados dos horizontes subsuperficiais do solo com TPA e solos adjacentes indica que o horizonte antrópico do solo TPA foi provavelmente desenvolvido a partir de um horizonte similar aos Argissolos adjacentes com posterior transformação pedogenética através da introdução de materiais orgânicos e inorgânicos por antigas colonizações humanas, resultando no espessamento do horizonte superficial e em concentrações maiores de CaO e P 2 O 5 (teores totais), Zn (teor traço), P e Zn disponível (teores disponíveis), além de Ca e Mg trocáveis (teores trocáveis) em relação aos Argissolos adjacentes. Além disso, essa intervenção antrópica antiga também provocou modificações no horizonte subsuperficial do Argissolo com TPA, como concentrações altas de P 2 O 5 e principalmente P disponível. O Soil Taxonomy e o Sistema Brasileiro de Classificação de Solos (SiBCS) são adequados para a identificação de solo com horizonte antrópico (p.exe. TPA), uma vez que priorizam nas ordens do solo os principais processos pedogenéticos atuantes na formação do solo, relacionados aos horizontes subsuperficiais, além das transformações pedogenéticas posteriores no horizonte superficial. Contudo, este trabalho recomenda o acréscimo de alguns atributos diagnósticos como quantidade de artefatos cerâmicos e líticos, P 2 O 5 , P e Zn disponíveis, C orgânico, Ca 2+ + Mg 2+ (teores trocáveis), CTC e índice de saturação por bases no horizonte superficial para o agrupamento e distinção dos diversos tipos de solos antrópicos antigos da Amazônia. PALAVRAS-CHAVE: Mineralogia, Pré-história, Região Amazônica, Pedologia. Mineralogy and geochemistry of soil profiles with Archeological Black Earth from Bom Jesus do Tocantins, southeastern Amazon ABSTRACTThe comparison of morphological, mineralogical and chemical data of a soil with anthropic horizons -Archeological Black Earth (ABE) and surrounding Argissolos (Typic Kandiudox or Ultisols) allowed the identification of the main process acting on the ABE formation from the town of Bom Jesus do Tocantins, southeastern Pará State. The similarity between the data in the subsurface horizons of ABE and surrounding soils indicates that the former was likely developed from Argissolos with later pedogenetic transformation by the input of organic and inorganic materials from ancient human settlements, which resulted in thickness of the surface horizon and higher concentrations of CaO and P 2 O 5 (total content), Zn (trace content), available P and Zn (available content), and exchangeable Ca and Mg (exchangeable content) compared to surrounding Argissolos. Furthermore, such anthropic disturbance also resulted in changes in the subsurface horizon of Argissolos with ABE, such as high co...

Forms of soil organic phosphorus at black earth sites in the Eastern Amazon

“…The organic matter content in the ABE was higher at all sites compared to the areas of AD, agreeing with the levels of 46.50 mg dm -3 found by Silva et al (2012), but less than those found by Campos et al (2011) Forms of soil organic phosphorus at black earth sites in the Eastern Amazon…”

“…Silva et al (2012), characterising the BJ 8 site by attribute, observed an increase from 20 mg dm -3 in the A1 horizon to 50 mg dm -3 in the B2 horizon.…”

“…In the Amazon, anthropogenic soils known as Archaeological Black Earth (ABE), display high fertility related to the addition of organic residue and the presence of pyrogenic carbon resulting from biomass pyrolysis at temperatures over 600 °C, whose partial oxidation produces carboxyl groups that contribute to an increase in CEC, with a long-term increase in nutrient levels (FRASER et al, 2011;GLASER;BIRK, 2012;HOLLIDAY;GARTNER, 2007;KERN et al, 2010;SANTOS et al, 2013;SILVA et al, 2012).…”

Terras pretas: Approaches to formation processes in a new paradigm

“…Indeed, terras pretas formed in sandier soils tend to have lower chemical fertility, including lower levels of OC, calcium, magnesium, and phosphorus, as well as lower CEC and base saturation. This has been observed in Araracuara, Colombia (Andrade, 1986), in the Brazilian states of Pará (Silva et al, 2012;Souza, 2007;Kern et al, 2015) and Rondônia (Zimpel Neto, 2009), at the Jiquitaia site in Rio Preto da Eva, Amazonas , as well as in horizons described by Smith (1980) and Kämpf et al (2009). This distinction may hence be associated with local environmental factors and the pedogenic process.…”

“…() have identified sites with A horizons too light to meet archaeological criteria for classification as terra preta , while still presenting abundant archaeological remains and high chemical fertility. Conversely, terras pretas with low chemical fertility also occur at the Caquetá River in Colombia (Andrade, ), in the southeastern region of Pará, and in the states of Amazonas and Rondônia in Brazil (Kern et al., ; Silva et al., ; Zimpel Neto, ). Soil chemical analyses can thus complement field observation of anthropogenic soils.…”