Probing sediment burial age, provenance and geomorphic processes in dryland dunes and lake shorelines using portable luminescence data

Luminescence signals from portable optically-stimulated luminescence readers (POSL or port-OSL) can provide expedient insights into sample relative age, and under certain conditions can be simplistically calibrated against existing luminescence chronologies to provide first-order estimates of burial age. This is most straightforward in simple sedimentary systems where samples share a common provenance and geomorphic process history. The spatially extensive southern African dune and palaeolake shoreline luminescence database, for which hundreds of non-light exposed bulk sediments are available, offers a valuable test case to examine the conditions under which POSL-bulk sediment calibration approaches are feasible. To do this we combine measurements of inherent luminescence sensitivity of bulk sediment (BSS) with analysis of sedimentary composition (petrology and presence of calcium carbonate) and texture. We show that BSS, along with POSL IRSL:BSL ratios and petrological data, account for region-to-region variations, whilst internal variability (scatter) within the lake shorelines dataset relates to variations in BSS and sediment texture. At the scale of southern African subcontinent drylands, we see that provenance and geomorphological process history influence sample mineralogical composition and POSL signal characteristic, including BSS

Distribuição e incerteza da acidez de um latossolo vermelho-amarelo húmico sob cultivo de café Distribution and uncertainty of acidity of an oxisol under coffee cultivation

Com o desenvolvimento da agricultura, a utilização de novas alternativas na avaliação das propriedades que influenciam o rendimento das plantas tornou-se indispensável para melhor manejar o sistema agrícola. O objetivo deste trabalho foi utilizar uma ponderação por meio da modelagem fuzzy para estudar, com base em atributos químicos do solo, a propagação de incertezas da acidez de um Latossolo Vermelho-Amarelo húmico cultivado com café arábica. As amostragens de solo foram realizadas na profundidade de 0-20 cm, em uma malha totalizando 50 pontos. Os atributos avaliados foram: pH em H2O, acidez trocável (Al3+), acidez potencial (H + Al) e saturação por Al (m). Os dados foram analisados pela estatística descritiva e pela geoestatística. Utilizou-se um sistema de classificação fuzzy e os atributos descritos para inferir sobre a acidez do solo. A lógica fuzzy, pelo algoritmo utilizado, teve um bom desempenho na caracterização e no mapeamento das incertezas da acidez do solo em questão.<br>With the development of agriculture, the use of new tools for the evaluation of the properties related to plant yields have become essential to improve the management of agricultural systems. The purpose of this study was to use a fuzzy model to investigate, based on soil chemical properties, the propagation of uncertainty of the acidity of a humic Red-Yellow Latosol (Oxisol) under Arabic coffee plantation. The soil was sampled at a depth of 0 - 0.2 m, in a grid, totaling 50 sampling points. The following attributes were determined: pH in H2O, exchangeable acidity (Al3+), potential acidity (H + Al) and Al saturation (m). The data were analyzed by descriptive statistics and geostatistics. A fuzzy classification system was used based on the attributes described to infer on the soil acidity. Fuzzy logic, with the algorithm used, was efficient to characterize and map the uncertainties of acidity of the soil under study