Abstract: Most of the World’s germanium (Ge) is mined from Ge-rich lignite, where it is commonly associated with elevated arsenic (As), tungsten (W) and beryllium (Be) contents. Over the past decade, new evidence showing that World-class Ge deposits result from the interaction of hydrothermal fluids with organic matter in coal seams has emerged. Yet, the chemical state of Ge and associated metals in lignite remains poorly understood. We used Mega-pixel Synchrotron X-ray Fluorescence (MSXRF), X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) to characterize the oxidation states and chemical bonding environment of Ge, As, and W in two world-class Mesozoic Ge-in-lignite deposits (Lincang, Yunnan, southwestern China; Wulantuga, Inner Mongolia, northeastern China); in lignite-bearing uranium (U) ores from the Beverley deposit (South Australia) hosted in Eocene sandstones; and in lignite and preserved wood in late Oligocene-Miocene fluviatile sediments (Gore, Southland, New Zealand). The aim was to improve our understanding of the enrichment mechanism of Ge in lignite and better evaluate the environmental mobility of Ge and some of the associated metals (specifically As and W) in lignite ores. In all samples, chemical maps show that Ge is distributed homogeneously (down to 2μm) within the organic matter. XANES and EXAFS data show that Ge exists in the tetravalent oxidation state and in a distorted octahedral coordination with O, consistent with complexing of Ge by organic ligands. In some pyrite-bearing samples, a minor fraction of Ge is also present as Ge(IV) in association with pyrite. In contrast, As displays a more complex speciation pattern, sometimes even in a single sample, including As(III), As(V), and As(−I/+II) in solid solution in sulfides. Arsenic in sulfides occurs in anionic and cationic forms, i.e., it shows both the common substitution for S22− and the substitution for Fe recently discovered in some hydrothermal pyrites. Tungsten was present as W(VI) in distorted octahedral (3+3) coordination. The EXAFS data confirm the absence or minor contribution of individual W-rich minerals such as scheelite or ferberite to W mass balance in the studied samples. These data show that Ge, W, and probably some As are scavenged via formation of insoluble, oxygen-bridged metal organic complexes in lignite. Destruction of the organic ligands responsible for fixing Ge and W (As) in these lignites is required for liberating the metals, e.g. from waste materials. Geochemical modelling suggests that Ge, W, Be and As all can be extracted from granitic rocks by dilute, low temperature hydrothermal fluids. Germanium is transported mainly as the tetrahedral Ge(OH)4(aq) complex, but fixed as an octahedral oxy-bridged organic complex. The same situation is valid for W, which is transported at the tetrahedral tungstate ion, but most likely scavenged via formation of a 6-coordinated metal-organic species. The Ge-Be-W±As association in Ge-rich coals reflects the source of the metals as well as related scavenging mechanisms.

Abstract: Nature-based solutions (NbS) are increasingly recognized as effective environmental-management measures to address societal challenges such as climate change, water and food security, and disaster risk reduction, thus contributing to human well-being and protecting biodiversity. In addition to being particularly susceptible to these challenges, mountain areas are prone to multihazard conditions, due to their steep topography and particular climatic conditions. NbS can contribute greatly to the sustainable development of mountain ecosystems. This chapter presents examples of NbS in mountain areas around the globe that demonstrate how this approach contributes to achieving sustainable development.

Abstract: Paleohydrological data from the African tropics and subtropics, including lake, groundwater and speleothem records, are reviewed to show how environments and climates from both hemispheres are inter-related. Although orbitally induced changes in the monsoon strength account for a large part of long-term climatic changes in tropical Africa, the Late Pleistocene–Holocene hydrological fluctuations rather appear to have been a series of abrupt events that reflect complex interactions between orbital forcing, atmosphere, ocean and land surface conditions. During the Last Glacial Maximum (23–18ka BP), most records indicate that generally dry conditions have prevailed in both hemispheres, associated with lower tropical land- and sea-surface temperatures. This agrees with simulations using coupled ocean–atmosphere models, which predict cooling and reduced summer precipitation in tropical Africa; the global hydrological cycle was weaker than today when the extent of large polar ice-sheets and sea-ice was a prominent forcing factor of the Earth’s climate. Glacial-interglacial climatic changes started early: a first wetting/warming phase at ca. 17–16ka BP took place during a period of rapid temperature increase in Antarctica. Next, two drastic arid-humid transitions in equatorial and northern Africa occurred around 15–14.5ka BP and 11.5–11ka BP. Both are thought to match the major Greenland warming events, in concert with the switching of the oceanic thermohaline circulation to modern mode. However, part of the climatic signal after 15 ka BP also seems related to the Antarctica climate. During the Holocene, Africa has also experienced rapid hydrological fluctuations of dramatic magnitude compared to the climatic changes at high latitudes. In particular, major dry spells occurred around 8.4–8ka and 4.2–4ka BP in the northern monsoon domain. Comparison with other parts of the world indicates that these events have a worldwide distribution but different regional expressions. In the absence of large polar ice sheets, changes in the continental hydrological cycles in the tropics may have a significant impact on the global climate system. Climate information gathered here allows to identify geographical and methodological gaps, and raise some scientific questions that remain to be solved to better understand how the tropics respond to changes in major climate-forcing factors, and how they influence climate globally.

Abstract: Population increase, climate change and soil impermeability are factors causing floods in large urban centres. Such places also always have water shortage problems. This research aims to evaluate the influence of rainwater harvesting in residential buildings on stormwater in a basin located in southern Brazil (Rio Cachoeira Basin). Urbanised and non-urbanised areas, soil types, curve numbers and time of concentration of each sub-basin were taken into account. Through the HEC-HMS programme, it was possible to calculate hydrographs for the base scenario (when there is no rainwater harvesting). Then, rainwater tanks for the residential buildings were sized using the computer programme Netuno. In the second scenario, there is rainwater harvesting in all residential buildings. Thus, the hydrographs for the second scenario were also calculated. The peak flow reduction potentials for the sub-basins ranged from 2.7% to 14.3%. The highest percentage (14.3%) did not occur in the sub-basin with the most extensive roof area; such highest peak flow reduction occurred in Bom Retiro sub-basin. In Bom Retiro sub-basin, there are more houses than multi-storey residential buildings. Even when considering the full potential of rainwater harvesting for roof areas of all existing buildings in the Rio Cachoeira Basin, the average potential reduction in peak flow was 7.2%. The conclusion is that rainwater tanks in residential buildings have little influence on stormwater runoff, and the stormwater runoff will be less affected when the area of the hydrographic basin is larger. Thus, the reduction in peak flows is insignificant when considering the flooding in the region.

Abstract: Previous research on lacustrine stromatolites from Etosha Pan in Namibia obtained ages on carbonate close to or beyond the limits of radiocarbon dating. These ages suggested that the basin was likely not subject to extensive flooding during the last ca. 40ka. This study shows that AMS radiocarbon ages for the carbonate of a stromatolite from Poacher’s Point are 15–21ka older than ages for organic material in the stromatolite structure. Calibrated ages range from 30 to 40ka for carbonate and 3–19ka for the organic residue. The new ages, together with petrographic and isotopic data for the stromatolite, have provided important new information on past flooding of Etosha Pan including evidence of prolonged lacustrine conditions during the Holocene Climatic Optimum.