Modern anthropogenic drought in Central Brazil unprecedented during last 700 years.

A better understanding of the relative roles of internal climate variability and external contributions, from both natural (solar, volcanic) and anthropogenic greenhouse gas forcing, is important to better project future hydrologic changes. Changes in the evaporative demand play a central role in this context, particularly in tropical areas characterized by high precipitation seasonality, such as the tropical savannah and semi-desertic biomes. Here we present a set of geochemical proxies in speleothems from a well-ventilated cave located in central-eastern Brazil which shows that the evaporative demand is no longer being met by precipitation, leading to a hydrological deficit. A marked change in the hydrologic balance in central-eastern Brazil, caused by a severe warming trend, can be identified, starting in the 1970s. Our findings show that the current aridity has no analog over the last 720 years. A detection and attribution study indicates that this trend is mostly driven by anthropogenic forcing and cannot be explained by natural factors alone. These results reinforce the premise of a severe long-term drought in the subtropics of eastern South America that will likely be further exacerbated in the future given its apparent connection to increased greenhouse gas emissions.

Measurement of sulfur in environmental samples using the interference standard method with an O2 -pressurized reaction cell and a single-quadrupole inductively coupled plasma mass spectrometer.

RATIONALE: Precise and accurate analysis of trace sulfur in environmental samples is essential to understand its biogeochemical cycle. Yet it remains a challenging analytical task for single-quadrupole inductively coupled plasma mass spectrometry (ICP-MS) instrumentation because of the presence of significant isobaric interferences. METHODS: We evaluated the effect that different instrumental parameters have on the formation of SO+ species, and show that, under our instrumental configuration, it is not possible to fully remove all spectral interferences. Consequently, our instrumental optimization is focused on minimizing their contribution while obtaining the best possible sensitivity. We assessed the performance of the interference standard (IFS) method, where the signal corresponding to the SO+ ions formed in the ICP is normalized to that of 36 Ar+ . RESULTS: We found that, by pressurizing the cell with O2 , there is a significant improvement in sensitivity and detection limits, associated with a more effective production and focalization of SO+ ions. Moreover, by applying the systematics of the IFS with pure O2 injected into the cell (IFS-O2 ) we observed a significant improvement in accuracy and detection limits, making this the method of choice for the quantification of trace sulfur in environmental samples by ICP-MS. CONCLUSIONS: The method described here represents an effective and affordable alternative for the accurate and precise determination of sulfur using single-quadrupole ICP-MS in environmental samples, with LODs and LOQs comparable with those obtained with more expensive instrumentation.

Inter-hemispheric synchroneity of Holocene precipitation anomalies controlled by Earth's latitudinal insolation gradients.

Atmospheric circulation is a fundamental component of Earth's climate system, transporting energy poleward to partially offset the latitudinal imbalance in insolation. Changes in the latitudinal distribution of insolation thus force variations in atmospheric circulation, in turn altering regional hydroclimates. Here we demonstrate that regional hydroclimates controlled by the Northern Hemisphere mid-latitude storm tracks and the African and South American Monsoons changed synchronously during the last 10 kyrs. We argue that these regional hydroclimate variations are connected and reflect the adjustment of the atmospheric poleward energy transport to the evolving differential heating of the Northern and Southern Hemispheres. These results indicate that changes in latitudinal insolation gradients and associated variations in latitudinal temperature gradients exert important control on atmospheric circulation and regional hydroclimates. Since the current episode of global warming strongly affects latitudinal temperature gradients through Arctic amplification, our results can inform projections of likely inter-hemispheric precipitation changes in the future.

Pharmacokinetics and hematotoxicity of a novel copper-based anticancer agent: casiopeina III-Ea, after a single intravenous dose in rats.

Casiopeina III-Ea is a mixed chelate copper (II) complex that has shown cytotoxic and antitumor activity in vitro and in vivo. The aim of this study was to investigate the pharmacokinetics of total copper derived from casiopeina III-Ea administered by intravenous bolus injection to Wistar rats. Other objective was to evaluate the hematotoxicity produced by this compound in those animals. Wistar rats received a single intravenous dose of 4 mg/kg of casiopeina III-Ea. Blood samples were taken and pharmacokinetics evaluated. Furthermore, erythrocyte copper levels were determined to identify a potential target and Zn levels were analyzed to determine a possible change. For the evaluation of hematotoxicity, both blood and urine samples were collected for hematological and biochemical analyses; moreover, Fe determination was performed. Blood copper and zinc levels, red blood cell copper levels as well as copper, zinc, and iron amounts excreted into urine were analyzed by ICP-MS. The blood concentration-time profile of copper derived from casiopeina III-Ea was fitted to a two-compartment model with a zero-order input. Cumulative amounts of Cu, Zn, and Fe excreted into rat urine after administration of casiopeina III-Ea were different with respect to control. Hematological and biochemical data indicated a hemolytic toxicity. Pharmacokinetic analysis of total copper derived from casiopeina III-Ea provided a general knowledge about distribution and elimination process of this compound. Additionally, the systemic exposure of the copper derived from casiopeina III-Ea accounts for the hematotoxicity of this complex at test dose.

Orbital pacing and ocean circulation-induced collapses of the Mesoamerican monsoon over the past 22,000 y.

The dominant controls on global paleomonsoon strength include summer insolation driven by precession cycles, ocean circulation through its influence on atmospheric circulation, and sea-surface temperatures. However, few records from the summer North American Monsoon system are available to test for a synchronous response with other global monsoons to shared forcings. In particular, the monsoon response to widespread atmospheric reorganizations associated with disruptions of the Atlantic Meridional Overturning Circulation (AMOC) during the deglacial period remains unconstrained. Here, we present a high-resolution and radiometrically dated monsoon rainfall reconstruction over the past 22,000 y from speleothems of tropical southwestern Mexico. The data document an active Last Glacial Maximum (18-24 cal ka B.P.) monsoon with similar δ(18)O values to the modern, and that the monsoon collapsed during periods of weakened AMOC during Heinrich stadial 1 (ca. 17 ka) and the Younger Dryas (12.9-11.5 ka). The Holocene was marked by a trend to a weaker monsoon that was paced by orbital insolation. We conclude that the Mesoamerican monsoon responded in concert with other global monsoon regions, and that monsoon strength was driven by variations in the strength and latitudinal position of the Intertropical Convergence Zone, which was forced by AMOC variations in the North Atlantic Ocean. The surprising observation of an active Last Glacial Maximum monsoon is attributed to an active but shallow AMOC and proximity to the Intertropical Convergence Zone. The emergence of agriculture in southwestern Mexico was likely only possible after monsoon strengthening in the Early Holocene at ca. 11 ka.