SANDRA REGINA DAMATTO
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Artigo IPEN-doc 30434 Short-lived natural radionuclides as tracers in hydrogeological studies2024 - SCHUBERT, MICHAEL; LIN, MANG; CLARK, JORDAN F.; KRALIK, MARTIN; DAMATTO, SANDRA; COPIA, LORENZO; TERZER-WASSMUTH, STEFAN; HARJUNG, ASTRIDFundamental approaches to the study of groundwater rely on investigating the spatial and temporal distribution of stable and radioactive isotopes and other anthropogenic compounds in natural waterbodies. The most often used tracers for estimating groundwater flow paths and residence times, groundwater/surface water interaction as well as tracing chemical (contamination) sources include stable isotopes of water (δ 18O and δ 2H), radiocarbon (14C; t1/2 = 5730 a), tritium (3H; t1/2 = 12.43 a) as well as unreactive fluorine-containing gases (e.g., chlorofluorocarbons CCl3F or CFC-11; CCl2F3 or CFC-12; C2Cl3F3 or CFC-113; and SF6). While gas tracers are usually referred to as transient tracers and are appropriate for investigating modern flow systems, the isotopic tracers are often used to investigated paleo or regional flow systems. Stable isotopes of water can also be used to investigate groundwater/surface water interactions. Another, thus far been less frequently used group of groundwater tracers, are cosmo- and geo- genic short-lived radioisotopes. These isotopes are uniquely suited for studying a wide range of groundwater problems that have short time scales including high aquifer vulnerability to quantitative and qualitative impacts and groundwater discharge to surface waters. Here, we discuss and compare the applications of radio‑sulphur (35S; half-life t1/2 = 87 d), radio‑beryllium (7Be; t1/2 = 53 d), radio‑phosphorus (32/33P; combined t1/2 = 33 d), natural tritium (3H; t1/2 = 12.43 a), radon (222Rn; t1/2 = 3.8 d) and short-lived radium (224/223Ra; combined t1/2 = 5.2 d). The paper discusses the principles of the individual tracer methods, focusing on the isotopes' input functions or values, on sampling techniques, and on methods of analyses. Case studies that applied a combined use of the tracers are referred to for readers who wish to learn more about the application of the so far underused cosmo- and geo- genic radioisotopes as aquatic tracers.Artigo IPEN-doc 24324 Biogeochemical diversity, O2-supersaturation and hot moments of GHG emissions from shallow alkaline lakes in the Pantanal of Nhecolândia, Brazil2018 - BARBIERO, LAURENT; SIQUEIRA NETO, MARCOS; BRAZ, ROSANGELA R.; CARMO, JANAINA B. do; REZENDE FILHO, ARY T.; MAZZI, EDMAR; FERNANDES, FERNANDO A.; DAMATTO, SANDRA R.; CAMARGO, PLINIO B. deNhecolândia is a vast sub-region of the Pantanal wetland in Brazil with great diversity in surface water chemistry evolving in a sodic alkaline pathway under the influence of evaporation. In this region, > 15,000 shallow lakes are likely to contribute an enormous quantity of greenhouse gas to the atmosphere, but the diversity of the biogeochemical scenarios and their variability in time and space is a major challenge to estimate the regional contribution. From 4 selected alkaline lakes, we compiled measurements of the physico-chemical characteristics of water and sediments, gas fluxes in floating chambers, and sedimentation rates to illustrate this diversity. Although these lakes have a similar chemical composition, the results confirm a difference between the black-water and green-water alkaline lakes, corresponding to distinct biogeochemical functioning. This difference does not appear to affect lake sedimentation rates, but is reflected in gas emissions. Black-water lakes are CO2 and CH4 sources, with fairly constant emissions throughout the seasons. Annual carbon dioxide and methane emissions approach 0.86 mol m− 2 y− 1 and 0.07 mol m− 2 y− 1, respectively, and no clear trend towards N2O capture or emission was observed. By contrast, green-water lakes are CO2 and N2O sinks but important CH4 sources with fluxes varying significantly throughout the seasons, depending on the magnitude of the phytoplankton bloom. The results highlight important daily and seasonal variations in gas fluxes, and in particular a hot moments for methane emissions, when the O2-supersaturation is reached during the afternoon under extreme bloom and sunny weather conditions, provoking an abrupt O2 purging of the lakes. Taking into account the seasonal variability, annual methane emissions are around 10.2 mol m− 2 y− 1, i.e., much higher than reported in previous studies for alkaline lakes in Nhecolândia. Carbon dioxide and nitrous oxide consumption is estimated about 1.9 mol m− 2 y− 1 and 0.73 mmol m− 2 y− 1, respectively. However, these balances must be better constrained with systematic and targeted measurements throughout the seasons.