Resilience and brittleness in the ALERTA RIO system: a field study about the decision-making of forecasters

Natural disasters, particularly those triggered by heavy rainfall, may cause major damage and death. However, if an accurate early warning is issued, the damage can be mitigated. In Latin America and Brazil, characteristics of socioeconomic development often lead to a disorderly growth of cities and, consequently, occupation and irregular construction in risk areas. Therefore, forecasts of heavy rainfall, as well as preventative and mitigatory actions based on meteorological data/alerts, are essential to saving lives and minimizing material loss. An event that would have benefited from such actions is that which occurred in the mountainous region of Rio de Janeiro in January 2011, when over 800 people lost their lives. This work describes the first research initiative on resilience engineering domain in systems to forecast heavy rains in Rio de Janeiro. The results indicate important sources of brittleness in the system that supports the work of meteorologists, mainly related to the technical and organizational framework, and suggests that the main source of resilience in dealing with critical situations is the tacit knowledge of experts.     

Assessing Decomposition Rates of Rhizophora mangle and Laguncularia racemosa Leaves in a Tropical Mangrove

Studies exploring leaf decomposition in mangroves in the Brazilian northeast are scarce. Therefore, in a mangrove of the Cachoeira River estuary at Ilhéus, Bahia, the decomposition of senescent leaves of Rhizophora mangle L. and Laguncularia racemosa Gaertn was studied. The litter-bag method and the Olson exponential model were applied to estimate the decomposition rates. The decay pattern of leaf material of both species was similar to those reported in the literature, with rapid initial weight loss, followed by a deceleration and period of slow weight loss. L. racemosa had the highest decay constants at all the study sites which suggest that their leaves are more easily degraded than those of R. mangle. The constantly submerged site presented the highest decay constants of 0.022 g g^?1 day^?1 for R. mangle and 0.031 g g^?1 day^?1 for L. racemosa. Most (95 %) of the leaf material of the two species was lost in 135 and 98 days, respectively. Benthic macrofauna organisms were recorded in the litter bags from the fifth day after the start of the experiment. Such organisms play a key role in the first phase of decomposition in this mangrove system. The decay constants of the leaf litter were generally higher than those reported in other tropical and subtropical regions. This suggests that differences in the process of decomposition are in response to environmental conditions at each location.     

Salt kinematics and regional tectonics across a Permian gas field: a case study from East Frisia, NW Germany

This study presents a reconstruction of the tectonic history of an Upper Rotliegend tight gas field in Northern Germany. Tectonism of the greater study area was influenced by multiple phases of salt movement, which produced a variety of salt-related structural features such as salt walls, salt diapirs as well as salt glaciers (namakiers). A sequential 2D retro-deformation and stratal backstripping methodology was used to differentiate mechanisms inducing salt movement and to discuss their relation to regional tectonics. The quantitative geometric restoration included sedimentary balancing, decompaction, fault-related deformation, salt movement, thermal subsidence, and isostasy to unravel the post-depositional tectonic overprint of the Rotliegend reservoir rock. The results of this study indicate that reactive salt diapirism started during an Early Triassic interval of thin-skinned extensional tectonics, followed by an active diapirism stage with an overburden salt piercement in the Late Triassic, and finally a period of intensive salt surface extrusion and the formation of salt glaciers (namakiers) in Late Triassic and Jurassic times. Since the Early Cretaceous, salt in the study area has been rising by passive diapirism.     

Water quality and risk assessment of dug wells: a case study for a poor community in the city of São Paulo, Brazil

Sparsely populated areas, or peripheral communities commonly lack access to a public water supply and sewerage systems. The inhabitants of these areas must make use of excavated wells to provide their water needs, and cesspits for domestic wastewater disposal. These on-site sanitation systems can release pathogens and nutrients into shallow groundwater. These poor communities urgently require cheap and efficient techniques for the detection of sanitary conditions, in order to prevent contamination of the water resources supplied by dug wells. The sanitary risk assessment methodology, applied in an irregular settlement south of the city of São Paulo, was based on a questionnaire with yes/no questions (risk factors), which allowed the identification of problems related to the well construction and operation, and the presence of potential contamination sources in its vicinity. These risk factors were compared against nitrate and bacterial analysis using the clustering statistical method, to verify the relationship between contamination and certain aspects surveyed in the questionnaire. Questions that were more related to contaminated wells were those concerning the presence of cover and its integrity; gaps between mouth and cover; the surrounding pavement and presence of ground irregularities; infiltration in the well casing; water-suspended materials; and proximity to contamination sources. Contamination models based on variograms allowed to observe that bacterial contamination presented a strong localized component, which was associated frequently with the way residents handled the wells, whereas nitrate contamination was related more to a regional (spatial) component; that is, the distance between wells and cesspits.     

Non-glacial paleoenvironments and the extent of Weichselian ice sheets on Severnaya Zemlya, Russian High Arctic

The extent of the Barents-Kara Sea ice sheet (northern Europe and Russia) during the Last Glacial Maximum (LGM), in Marine Isotope Stage (MIS) 2 is controversial, especially along the southern and northeastern (Russian High Arctic) margins. We conducted a multi-disciplinary study of various organic and mineral fractions, obtaining chronologies with ¹⁴C and luminescence dating methods on a 10.5 m long core from Changeable Lake (4 km from the Vavilov Ice Cap) on Severnaya Zemlya. The numeric ages indicate that the last glaciation at this site occurred during or prior to MIS 5d-4 (Early Middle Weichselian). Deglaciation was followed by a marine transgression which affected the Changeable Lake basin. After the regression the basin dried up. In late Middle Weichselian time (ca 25–40 ka), reworked marine sediments were deposited in a saline water body. During the Late Weichselian (MIS 2), the basin was not affected by glaciation, and lacustrine sediments were formed which reflect cold and arid climate conditions. During the termination of the Pleistocene and into the Holocene, warmer and wetter climate conditions than before led to a higher sediment input. Thus, our chronology demonstrates that the northeastern margin of the LGM Barents-Kara Sea ice sheet did not reach the Changeable Lake basin. This result supports a modest model of the LGM ice sheet in northern Europe determined from numeric ice sheet modelling and geological investigations.     

Removal of Copper,Nickel and Zinc Ions from Aqueous Solution by Chitosan‐8‐Hydroxyquinoline Beads

In this work, 8‐hydroxyquinoline is used as the active sites in cross‐linked chitosan beads with epichlorohydrin (CT‐8HQ). The CT‐8HQ material was shaped in bead form and used for heavy metal removal from aqueous solution. The study was carried out at pH 5.0 with both batch and column methods and the maximum adsorption capacity of metal ions by the CT‐8HQ was attained in 4 h in the batch experiment. The adsorption capacity order was: Cu²⁺ > Ni²⁺ > Zn²⁺ for both mono‐ and multi‐component systems with batch conditions. From breakthrough curves with column conditions, the adsorption capacity followed the order Cu²⁺ > Zn²⁺ > Ni²⁺ for both mono‐ and multi‐component systems. The CT‐8HQ beads maintained good metal adsorption capacity for all five cycles with absorbent restoration achieved with the use of 1.0 mol L^–1 HCl solution, with 90% regeneration.     

Energetics of radiation damage in natural zircon (ZrSiO4)

Transposed temperature drop calorimetry at 1000 °C was performed on natural zircons (ZrSiO₄) from Sri Lanka that were partially to completely metamict due to α-decay event damage (0.06 to 11.7×10¹⁵ α-decay events/mg). The enthalpy of annealing at room temperature (ΔH_anneal) varies sigmoidally as a function of radiation dose. ΔH_anneal reaches a saturation plateau at radiation doses greater than 5×10¹⁵ α-decay events/mg. The annealing of several samples to a crystalline structure with broadened diffraction peaks does not significantly affect the enthalpy of annealing. The large magnitude of the enthalpy of annealing plateau, ?59±3 kJ/mol, suggests that the damage to the structure is pervasive on the scale of Angstroms, consistent with the loss of mid-range order characteristic of a glass. The energetics are consistent with, but do not require, chemical heterogeneity caused by micro-domains of amorphous SiO₂-rich and ZrO₂-rich regions in the metamict state.     

Evolution of fluids associated with metasedimentary sequences from Chaves (North Portugal)

In order to identify and characterise fluids associated with metamorphic rocks from the Chaves region (North Portugal), fluid inclusions were studied in quartz veinlets, concordant with the main foliation, in graphitic-rich and nongraphitic-rich lithologies from areas with distinct metamorphic grade. The study indicates multiple fluid circulation events with a variety of compositions, broadly within the C–H–O–N–salt system. Primary fluid inclusions in quartz contain low salinity aqueous–carbonic, H₂O–CH₄–N₂–NaCl fluids that were trapped near the peak of regional metamorphism, which occurred during or immediately after D2. The calculated P–T conditions for the western area of Chaves (CW) is P=300–350 MPa and T500 °C, and for the eastern area (CE), P=200–250 MPa and T=400–450 °C. A first generation of secondary fluid inclusions is restricted to discrete cracks at the grain boundaries of quartz and consists of low salinity aqueous–carbonic, H₂O–CO₂–CH₄–N₂–NaCl fluids. P–T conditions from the fluid inclusions indicate that they were trapped during a thermal event, probably related with the emplacement of the two-mica granites.

A second generation of secondary inclusions occurs in intergranular fractures and is characterised by two types of aqueous inclusions. One type is a low salinity, H₂O–NaCl fluid and the second consists of a high salinity, H₂O–NaCl–CaCl₂ fluid. These fluid inclusions are not related to the metamorphic process and have been trapped after D3 at relatively low P (hydrostatic)–T conditions (P<100 MPa and T<300 °C).

Both the early H₂O–CH₄–N₂–NaCl fluids in quartz from the graphitic-rich lithologies and the later H₂O–CO₂–CH₄–N₂–NaCl carbonic fluid in quartz from graphitic-rich and nongraphitic-rich lithologies seem to have a common origin and evolution. They have low salinity, probably resulting from connate waters that were diluted by the water released from mineral dehydration during metamorphism. Their main component is water, but the early H₂O–CH₄–N₂–NaCl fluids are enriched in CH₄ due to interaction with the C-rich host rocks.

From the early H₂O–CH₄–N₂–NaCl to the later aqueous–carbonic H₂O–CO₂–CH₄–N₂–NaCl fluids, there is an enrichment in CO₂ that is more significant for the fluids associated with nongraphitic-rich lithologies.

The aqueous–carbonic fluids, enriched in H₂O and CH₄, are primarily associated with graphitic-rich lithologies. However, the aqueous–carbonic CO₂-rich fluids were found in both graphitic and nongraphitic-rich units from both the CW and CE studied areas, which are of medium and low metamorphic grade, respectively.     

Jarosite stability on Mars

Jarosite, a potassium (sodium) iron sulphate hydrated mineral, has recently been identified on the martian surface by the Opportunity rover. Using recent thermochemical data [Drouet and Navrotsky, 2003, Geochim. Cosmochim. Acta 67, 2063-2076; Forray et al., 2005, Geochim. Cosmochim. Acta, in press], we calculate the equilibrium decomposition curve of jarosite and show that it is thermodynamically stable under most present martian pressures and temperatures. Its stability makes jarosite potentially useful to retain textural, chemical, and isotopic evidence of past history, including possible biological activity, on Mars.