Abstract
The present study aims affinity between available concentrations of phosphorus, micronutrients (Cu, Zn and Mn) and stable carbon (SC) in archaeological black earth (ABE) from area “Ilha de Terra”/Caxiuanã—Pará. The relevance of this study refers especially to the determination of carbon concentrations (total, oxidable and semi-labile carbon) directly associated with those of pyrogenic carbon, common in ABE, which should add their contributions to the understanding of soil organic matter recalcitrance. Chemical properties such as CEC and base saturation were determined for ABE and subjacent Latossoil. The available concentrations of nutrients were performed from sequential extraction F1 to F5 phases. Phosphorus was obtained by spectrophotometric method and micronutrients by MP-AES. TOC was determined by the combustion method; stable carbon was obtained from thermoxidation method CTO-375. The following results were obtained from ABE: CEC effective = 21 to 28 (cmolc·L-1); base saturation = 58% to 69%; Carbon concentrations (%): TOC = 2.95 to 3.94; SC = 0.25 to 0.88; semi-labile carbon = 1.75 to 3.63; oxidable = 2.11 to 3.65; inorganic carbon 0.01 to 0.38; P2O5 concentrations (mg·kg-1) in the ABE phases F3 (Fe-Mn oxides, F4 (organic ) and F5 (residual)) in the following order: 35 to 65; 200 to 400; 140 to 230. It was concluded that the chemical properties in ABE from Ilha de Terra site fall within the range of fertile and the high concentrations of phosphorus are biogenic origin. Phases F3 and F4 are those considered nutrient stocks from ABE studied area.
Highlights
The present study aims affinity between available concentrations of phosphorus, micronutrients (Cu, Zn and Mn) and stable carbon (SC) in archaeological black earth (ABE) from area “Ilha de Terra”/Caxiuanã—Pará
In the evaluations of the data obtained in TPA in relation to those obtained in Latosol, it appears that they are compatible with those expected, indicating an increase in the values of effective and potential CTC, base saturation (% V), oxidable carbon (Ox.C) and concentration of P2O5, reflecting improvement of conditions favorable to the stability of organic matter in Tpa of the Ilha de Terra site
The study involving the determination of concentrations of available nutrients of phosphorus, copper, manganese and zinc available in ABE from different sequential solid phases P1 to P5, total and stable Carbon and other chemical properties in ABE from the archaeological site Ilha de Terra
Summary
The ABE occurred as dark spots, distributed in several places in the central Amazon. It was identified by, being most well-known in places near the city of Manaus [6], such as: 1) occurrences in the district of Iranduba, collected in seven places under tertiary and quaternary sediments [7]; 2) in occurrences, distributed in different districts as anthropogenic soils over forest and cultivation [8]; 3) occurrences in the district of Manacapuru at two sites, Jiquitaia and Laranjal [9] contrasting environments. In the region of Caxiuanã, located in the western portion of the state of Pará, between Portel and Melgaço districts studies were carried out on the geology, archeology and geochemistry of the region, with several occurrences of ABE being recorded, such as those of the Manduquinha sites, Ponta Alegre, Mina II and Ilha de Terra, these occurrences being recorded under Latosols, correlated with the Alter do Chão Formation [11]
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