Most of the carbonate samples have a basic well-defined pretreatment protocol for 14C-AMS dating, but particularities of specific organisms have to be treated with care. This is the case of stromatolite samples, in which carbonate is formed by biogenesis and also has a porous structure that could contain recent organic material as a contaminant. In this work, we analyzed the differences in the radiocarbon content by using organic matter removals before chemical treatment with HCl: sodium hypochlorite (NaOCl) a 0.7M solution with pH ∼11, and hydrogen peroxide (H2O2) an 8.8M solution with pH ∼5. These treatments were chosen because they are the most used in stromatolite samples for geochemical analysis. To compare the impact of the organic matter removal treatments in stromatolite samples we also processed them as regular carbonate samples for radiocarbon analysis, with no organic matter removal (control samples). X-ray diffraction and X-ray fluorescence have been used to obtain mineral and elemental characterization, respectively. H2O2 could not influence the results of Mg-calcite concentrate samples. The use of NaOCl appears to have been effective in preserving more material than H2O2 independent of the mineralogical composition of the stromatolite layers. The F14C results after HCl etching for Mg-calcite concentrated samples were similar to those without etching suggesting that the HCl etching does not impact the results in this case. The organic matter removal is more important than the etching procedure for stromatolite samples. NaOCl is more indicated to be used as chemical pretreatment for radiocarbon analysis purposes independent of the mineral matrix of samples.

Fossil fuels are of utmost importance to the world we live in today. However, their use can cause major impacts on the environment, especially on water resources. In this regard, algae have been intensively used as a strategy for remediation and monitoring of environmental pollution due to its efficient absorption of contaminants. In this work, samples of seaweed collected in Niterói/RJ—contaminated with kerosene and diesel—were analyzed by radiocarbon (14C) accelerator mass spectrometry (AMS) and by n-alkane quantification with gas chromatography to evaluate bioaccumulation in function of the dosage of contaminants. The biogenic content measured by radiocarbon analysis resulted in 95.6% for algae contaminated with 10 mL of kerosene and 67.6% for algae contaminated with 10 mL of diesel. The maximum intensity of n-C17 n-alkane in algae with 5 mL, 10 mL, and 15 mL of diesel was 768.2, 1878.1, and 5699.2 ng.g-1, respectively. While the maximum concentration of n-C27 in algae with 5 mL, 10 mL and 15 mL of kerosene was 3.3, 35.9, and 150.3 ng.g-1. We concluded that, for both contaminants, their incorporation into algae increases as the contamination dosage increases, making this methodology an effective technique for monitoring and remediation of urban aquatic ecosystems.

The Radiocarbon Laboratory of the Fluminense Federal University was installed in 2009, and its NEC Single Stage Accelerator Mass Spectrometry system has been operational since 2012. As the first 14C-AMS facility in Latin America, the LAC-UFF became a reference center for radiocarbon (14C) dating in Brazil. Over the years we have implemented pretreatment protocols for several kinds of materials, such as cellulose, soil, bone, and biofuels. In the present paper we describe our current protocols for the preparation of these types of samples. Moreover, after 10 years of operation, with the aim of expanding the range of materials we are able to analyze, we report the results of several tests to improve accuracy, precision and background levels. For example, here we discuss how isotopic fractionation during the graphitization and measurement steps has been controlled. Concerning results interpretation, our research group has been using OxCal chronological models to analyze different contexts such as stromatolite growth, tree rings, soil deposition and marine reservoir effect (MRE) determination.

AMS radiocarbon and OSL dating, and profiling were used to directly delimit periods of variscite production at Pico Centeno Mine 2. These results were integrated with analysis of other well-dated periods of variscite production to establish an Iberian-wide chronological framework. Variscite production at Pico Centeno Mine 2 began at ~ 5200 BC, coincident with alpine jade production or Casa Montero Iberian flint production. Variscite was only used occasionally, together with other greenstones, during the 5th and 6th millennia BC. During the 4th millennium BC, variscite use began to increase to its apogee in the first half of 3rd millennium BC when it appeared in nearly every Iberian burial site. This increase in variscite production and use coincided with decline in the popularity of alpine jade. By the end of the 3rd millennium BC, new resources began to be valued such as Asian and African Ivory, Baltic and Sicilian amber, and copper-based metal products. The variscite cycle thus started with the decline of jade in the 5th–4th millennium BC, and ended with the appearance of copper, ivory and extra-peninsular amber by the end of the 3rd millennium BC.