The soils of the Amazon Region are usually highly weathered and not very fertile. However, in this same region are archeological soils called Amazonian Dark Earth, that have high concentrations of mineral nutrients and stable organic matter. Recently, Certini and Scalenghe proposed that the Anthropocene would have started in 2000 years BP, based on the use of anthropic soils such as Anthropocene Golden Spikes, especially the Amazonian Dark Earth. This study aims to compare the characteristics of Amazonian Dark Earth and Acrisols typical of Central Amazonia and to evaluate the role of these archaeological soils in issues related to the Anthropocene. Although all soils have been recognized as dystrophic, the Amazonian Dark Earth reflect their more complex pedogenesis, in which natural and anthropic processes act together, unlike the Acrisols. In the Anthropocene, Amazonian Dark Earth can be considered as excellent environmental markers indicating the onset and long-term extension of pre-Colombian human activities in the Amazon Region, but lack the stratigraphic characteristics necessary to be considered as adequate Golden Anthropocene Spikes.

Archaeological soils know as Amazonian Dark Earth (ADE) were proposed to be eligible as golden spikes from the beginning of the Anthropocene 2000 years BP (before presente). This hypothesis was highly contested by the international scientific community that pointed out as ADE do not have the necessary geological preservation conditions to serve as golden spikes. One of the main allegations is how ADE is found in natural ecosystems, which are susceptible to natural or anthropic erosion, which would prevent an adequate stratigraphic preservation. Therefore, the objective of this study was to evaluate the stability characteristics of ADE soil aggregates over different fallow periods and to determine if the ADE have a stratigraphic preservation capacity that makes them resistant to rain and mechanical erosion. It was observed that the fallow time did not significantly influence the stability of aggregates of the two evaluated areas and it was observed also that the organic matter of the soil (SOM) did not play a strong role as a cementing agent of the particles due to the oxidic and kaolinite character of these areas. Consequently, a susceptibility to rainfall and anthropic erosion of the ADE was verified, making them unusable as golden spikes from the beginning of the Anthropocene.

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Against of the growing world demand for food and the possibility of recovering some nutrients, this work focused on the evaluation of the use of Bioclastic Granules (BG) from the algae Lithothamnium calcareum as sorbent material for the removal/recovery of phosphorus from aqueous solutions. The main variables that affect the sorption process, such as pH, initial concentration of phosphate and GB, as well as the contact time were evaluated. The effect of pH was very significant, obtaining the best results of PO4 removal at pH 5. In the coarser granulometric fractions (+106 -150 and +210 -300 µm) the best removals were observed (around 75%). Regarding the initial PO4 concentration in the solutions, the highest removal (in the range of 74 to 78%) was observed in the lowest concentrations (5 to 70 mg L-1) and the best uptake (10 to 14 mg g-1) at higher concentrations (200 to 420 mg L-1). The PO4 sorption data fitted the Freundlich model well, with kF of 1.35 L mg-1 and n of 2.43. Using the Langmuir model, a qmax of 14.35 mg g-1 was obtained. Regarding the sorption data over time, a better fit to the pseudo-first order kinetic model was observed, obtaining a calculated qeq of 6.56 mg g-1 and a k1 of 0.0073 min-1. The incorporation of PO4 ions in the GB structure was confirmed through the characterization results before and after the sorption experiments using X-ray fluorescence (FRX) and scanning electron microscopy (SEM) techniques.

Nitrification and denitrification are the processes that give rise to the emissions of nitrous oxide (N2O) from the soil to the atmosphere, both processes being dependent on the availability of oxygen, but in opposite redox conditions. These reactions are affected by soil characteristics such as aeration, temperature, humidity, soil reaction, fertilizers, available organic matter, among others. The objective of this work was to evaluate the N2O emissions in a Brachiaria humidicola pasture, distributed in a toposequence in Seropédica, RJ. The area has variation of soil class and drainage influenced by topography. The experiment was conducted in the Milk Cattle Sector of the Federal Rural University of Rio de Janeiro (UFRRJ). The evaluated treatments were pasture planted under a Red-Yellow Argisol and pasture planted under the Gleissolo soil. The experimental design was in randomized blocks, with four replications and two treatments. The N2O emissions were evaluated using static chambers. Physical fractionation, aggregate weighted mean diameter (AMD) and water saturated pore space (EPSA) were also determined to understand the mechanisms related to N2O emission. The highest N2O fluxes were observed on the third and eighth day of sampling in the Red-Yellow Argisol (41 μg N-N2O m-² h-1). The accumulated emission of N2O during the monitoring period in the Red-Yellow Argisol (43.3 g N-N2O ha-1 day-1) was statistically significant in relation to Gleissolo (2.4 g N-N2O ha-1 day-1). The Gleissolo showed lower soil C input, measured by the free light fraction mass (FLL), and lower AMD. It concluded that, the Red-Yellow Argisol has an eighteen times greater potential to emit N2O than Gleissolo. Soil water content, FLL and percentage of stable aggregates in the Red-Yellow Argisol are factors that may be regulating the N loss pathways by nitrification.