Stratospheric ozone depletion: a key driver of recent precipitation trends in South Eastern South America

On a hemispheric scale, it is now well established that stratospheric ozone depletion has been the principal driver of externally forced atmospheric circulation changes south of the Equator in the last decades of the 20th Century. The impact of ozone depletion has been felt over the entire hemisphere, as reflected in the poleward drift of the midlatitude jet, the southward expansion of the summertime Hadley cell and accompanying precipitation trends deep into the subtropics. On a regional scale, however, surface impacts directly attributable to ozone depletion have yet to be identified. In this paper we focus on South Eastern South America (SESA), a region that has exhibited one of the largest wetting trends during the 20th Century. We study the impact of ozone depletion on SESA precipitation using output from 6 different climate models, spanning a wide range of complexity. In all cases we contrast pairs of model integrations with and without ozone depletion, but with all other forcings identically specified. This allows for unambiguous attribution of the computed precipitation trends. All 6 climate models consistently reveal that stratospheric ozone depletion results in a significant wetting of SESA over the period 1960–1999. Taken as a whole, these model results strongly suggest that the impact of ozone depletion on SESA precipitation has been as large as, and quite possibly larger than, the one caused by increasing greenhouse gases over the same period.     

The definition of potential infiltration areas in Guaratinguetá watershed, Paraíba do Sul Basin, Southeastern Brazil: an integrated approach using physical and land-use elements

This work describes the methodological approach used for mapping the potential infiltration areas of the Guaratinguetá watershed (160?km²), situated in Southeastern Brazil. The method is considered a qualitative approach, which takes into account thematic maps (geology, pedology, geomorphology, and land use/land cover) and the precipitation spatial distribution. A group of experts in Earth Sciences and Geotechnical Engineering has applied an infiltration potential scale factor that ranges from 5 (highest influence) to 1 (lowest influence). The final infiltration map was produced using several ArcGIS^? tools. The results showed that the most suitable (very high) infiltration areas represent only around 7% of the watershed area, which are associated with smooth and gentle hills, fluvial Tertiary sediments and yellow oxisols. However, growing impacts caused by land farming and urban developments require urgent planning for this region. Areas with high to moderate capacity of infiltration represent around 56% of the watershed and are found in the domain of igneous-metamorphic rocks associated with steep hill-slopes and relatively well-preserved forest fragments. This region requires a land-use strategy, such as reforestation programs, in order to increase the infiltration capacity of the watershed.     

Carbon Budget and Molecular Structure of Natural Organic Matter in Bank Infiltrated Groundwater

Managed aquifer recharge (MAR) provides means to remove natural organic matter (NOM) from surface waters. Recent studies have explored the degree of NOM removal in groundwater. In this study, we further elaborate the NOM removal at a lakeside natural bank infiltration site that functions as a surrogate for MAR. Our objective was to quantify the carbon budget in the aquifer based on concentration measurements of dissolved (in)organic carbon, and the molecular changes in NOM using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). According to the carbon budget, only 25% of the dissolved carbon entering the aquifer was organic, and it predominantly originated from lake water. Of the inorganic majority, on average 40% was produced in the vadose zone above the groundwater table, 31% in the lake bank, 22% in the aquifer as a result of degrading organic matter of lake water, and 7% in the lake. Seasonal concentration variations suggested that the lake bank was the main carbon source in the summer, increasing the carbon concentration of infiltrating lake water, that is, 3.0 mg/L to 7.9 mg/L. FT-ICR MS results showed 4960 to 5330 individual compounds in lake and groundwater. NOM removal in the aquifer was selective: the relative abundance of oxygen-containing species decreased from 75 to 31%, while the relative abundance of sulfur-containing species increased from 15 to 57%. The average molecular weights of both species remained unchanged. The study highlighted the role of lake bank processes and sulfur-containing species in groundwater quality.     

Verification of mid-ocean ballast water exchange using naturally occurring coastal tracers

We examined methods for verifying whether or not ships have performed mid-ocean ballast water exchange (BWE) on four commercial vessels operating in the Pacific and Atlantic Oceans. During BWE, a ship replaces the coastal water in its ballast tanks with water drawn from the open ocean, which is considered to harbor fewer organisms capable of establishing in coastal environments. We measured concentrations of several naturally occurring chemical tracers (salinity, six trace elements, colored dissolved organic matter fluorescence and radium isotopes) along ocean transects and in ballast tanks subjected to varying degrees of BWE (0-99%). Many coastal tracers showed significant concentration changes due to BWE, and our ability to detect differences between exchanged and unexchanged ballast tanks was greatest under multivariate analysis. An expanded dataset, which includes additional geographic regions, is now needed to test the generality of our results.     

Pb isotope signatures of sediments from Guanabara Bay, SE Brazil: Evidence for multiple anthropogenic sources

Sediments from Guanabara Bay and two rivers were analyzed for Pb isotope composition. The results define linear groups interpreted as different sources of Pb. The samples from Iriri and Surui rivers present different Pb compositions probably resulting from two active pollutants which are transported in the waters to the Guanabara Bay, where they are mixed. The ²⁰⁶Pb/²⁰⁷Pb values of 1.151 and 1.091 presented here are in the range of Brazilian galena ore signature.     

Petrographic criteria for fluid mobility of graphitic carbon in terrestrial and extraterrestrial samples

Graphitic carbon is a widespread precipitate in terrestrial and extraterrestrial samples. However it has a range of possible origins, which can be difficult to distinguish, including the in situ alteration of organic matter, thermal alteration of hydrocarbons, and precipitation from C–O–H fluids. Petrographic characteristics help to understand the origin of the graphite, including relationships with rock fabric, paragenetic sequences and evidence for fluid mobility. Characterization of a range of terrestrial samples will allow better interpretation of the petrography of carbon in extraterrestrial samples. In particular, improved petrographic data from carbonaceous chondrites and ureilite meteorites should help to distinguish the origin of carbon in their parent bodies.     

Evaporation and land surface energy budget at the Salar de Atacama, Northern Chile

Playa systems are driven by evaporation processes, yet the mechanisms by which evaporation occurs through playa salt crusts are still poorly understood. In this study we examine playa evaporation as it relates to land surface energy fluxes, salt crust characteristics, groundwater and climate at the Salar de Atacama, a 3000 km² playa in northern Chile containing a uniquely broad range of salt crust types. Land surface energy budget measurements were taken at eight representative sites on this playa during winter (August 2001) and summer (January 2002) seasons. Measured values of net all-wave radiation were highest at vegetated and rough halite crust sites and lowest over smooth, highly reflective salt crusts. Over most of the Salar de Atacama, net radiation was dissipated by means of soil and sensible heat fluxes. Dry salt crusts tended to heat and cool very quickly, whereas soil heating and cooling occurred more gradually at wetter vegetated sites. Sensible heating was strongly linked to wind patterns, with highest sensible heat fluxes occurring on summer days with strong afternoon winds. Very little energy available at the land surface was used to evaporate water. Eddy covariance measurements could only constrain evaporation rates to within 0.1 mm d⁻¹, and some measured evaporation rates were less than this margin of uncertainty. Evaporation rates ranged from 0.1 to 1.1 mm d⁻¹ in smooth salt crusts around the margin of the salar and from 0.4 to 2.8 mm d⁻¹ in vegetated areas. No evaporation was detected from the rugged halite salt crust that covers the interior of the salar, though the depth to groundwater is less than 1 m in this area. These crusts therefore represent a previously unrecorded end member condition in which the salt crusts form a practically impermeable barrier to evaporation.     

Nontronit vom Hohen Hagen und Chloropal vom Meenser Steinberg bei Göttingen

Zusammenfassung Von dem in der tertiären Sandunterlage des Hohen-Hagen-Basaltes ausgeschiedenen Nontronitmineral wurde eine chemische Analyse angefertigt und daraus die Strukturformel (Fe³⁺ _1,80Al_0,13Mg_0,10)_2,03[(OH)₂| Al_0,30Si_3,70O₁₀]^–0,31 aufgestellt, die einem Nontronit mit 90% Fe-Endglied entspricht. Die Bildung des Nontronitvorkommens erfolgte unter Mitwirkung des durch den Basaltaufstieg erhitzten und die übergeflossene Lava am Entweichen gehinderten Grundwassers der Sande. Der Stoffbestand entstammt dem Mobilisat der Basaltzersetzung. Die Ausfällung wurde durch E_h und p_H der sich mischenden Lösungen gesteuert. Die Transportbedingungen der Ionen und das Verhalten einiger Spurenelemente werden diskutiert. — Die chemische Analyse des Chloropals vom Meenser Steinberg ergibt für diesen einen Anteil von rund 1/4 Nontronit und 3/4 Opal-Cristobalit.

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Summary A chemical analysis was made of a nontronite mineral found in the tertiary sands below the basalt of the Hoher Hagen. Basing on this analysis, the structural formula is: (Fe³⁺ _1,80Al_0,13Mg_0,10)_2,03[(OH)₂| Al_0,30Si_3,70O₁₀]^–0,31. Thus, the mineral consists of 90% Fe-Nontronite. The formation of the nontronite was caused by the action of the ground water in the sands, which was heated by the basaltic magma and kept from escaping by the overflown lava. The chemical components were derived from the basalts through decomposition. The precipitation was caused by the differences in E_h and p_H of the solutions which were mixed during this process. The conditions for the transport of the ions and for the distribution of the trace elements are discussed. — From the chemical analysis of the Chloropale from the location Meenser Steinberg a mineralogical composition of 1/4 nontronite and 3/4 opale-cristobalite is calculated.

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Der Nontronit ist ... wohl ein Montmorillonit mit fast vollständigem Ersatz von Al³⁺ durch Fe³⁺ ... Als Zersetzungsprodukt eisenhaltiger Silikate weit verbreitet, ebenso wie der grüne Chloropal, der ein Gemenge von Nontronit mit Opalkieselsäure darstellt.Felix Machatschki, Spezielle Mineralogie auf geochemischer Grundlage (1953).

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Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.     

Microzonation of Lisbon: 1-D Theoretical Approach

—?The geology of Lisbon is very diversified, with a predominance of cretaceous rocks (basalt and limestone) in the western zone, while east and south it is covered by progressively thicker Tertiary deposits with diverse lithologies (sands, clays, silts, sandstones and limestones) and different geotechnical properties. Lisbon also contains several narrow long valleys, filled with thin alluvial deposits. A set of new geological profiles was drawn, along the east–west direction, 500 meters spaced. These profiles were based on the existing geological maps and complemented with new information collected from recent geotechnical boreholes. Theoretical modeling, using the Thomson–Haskell 1-D approach, was performed for 314 geological columns chosen from these profiles according to a regular grid 500 meters long. The physical parameters were obtained from specialized literature, seismic experiments and laboratory tests. The results are presented as contour maps for the peak frequencies and for the corresponding amplification factors. These results are compared with the microzonation map obtained by microtremor analysis and with the damage distribution observed in past earthquakes.     

Entries and omissions: using solicited diaries in geographical research

This paper explores the use of personal solicited diaries as a qualitative research tool within social geography. Diaries were used with women from South Africa who recorded their experiences of violence over a period of one month. The paper analyses diaries in terms of their longitudinal benefits, their socially constituted nature, their use in conjunction with interviews and finally their potential for empowerment. The paper concludes with a discussion of the limitations of the diary as a methodological tool.