Sinkholes in hypogene versus epigene karst systems, illustrated with the hypogene gypsum karst of the Sant Miquel de Campmajor Valley, NE Spain

The Garrotxa-Banyoles artesian aquifer system in NE Spain includes zones with epigene and hypogene evaporite karst and sinkhole development. The sinkhole fields related to hypogene evaporite dissolution are associated with the discharge zones of the aquifer, where groundwater from a confined limestone rises traversing an overlying gypsum formation capped by thick marls. This work analyses the sinkhole field developed in the Sant Miquel de Campmajor Valley (SMCV), a discharge area of the aquifer, where a cartographic inventory including 94 sinkholes has been produced. Sinkholes in this hypogene gypsum karst are mainly large caprock-collapse sinkholes rooted in deep-seated cavities generated by interstratal hypogene karstification, as corroborated by an electrical resistivity imaging (ERI) survey. They show a non-clustered distribution within the sinkhole field and the variations in size and density across the area are mainly controlled by the thickness of the marl caprock. The magnitude and frequency relationships of the sinkholes can be modelled with a high goodness of fit with a log-normal function, like in other regions of the world. However, in this deep-seated hypogene system the depressions show much larger dimensions. Potential differences between the sinkholes developed in hypogene and epigene karst environments are discussed, including their distribution with respect to the groundwater flow system, their spatial patterns and dimensions

Еволюція рослинного світу в природному і культигенному середовищі

У ході засідань Міжнародної наукової конференції “Еволюція рослинного світу в природному і культигенному середовищі”, присвяченої 200-річчю від Дня народження Чарльза Дарвіна, обговорено актуальні питання еволюційної теорії, ботаніки, фізіології рослин, інтродукції, генетики й селекції, екології, збереження і примноження глобального та локального біорізноманіття, лісових культур і фітомеліорації та інших біологічних наук.В ходе заседаний Международной научной конференции “Эволюция растительного мира в естественной и культигенной среде”, посвященной 200-летию со дня рождения Чарльза Дарвина, обсуждены актуальные вопросы эволюционной теории, ботаники, физиологии растений, интродукции, генетики и селекции, экологии, сохранения и приумножения глобального и локального биоразнообразия, лесных культур и фитомелиорации и других биологических наук.During meetings of the International scientific conference “Evolution of the natural and cultivated plants” to devoted a 200-year from the day of birth of Charles Darwin topical problems of the evolutional theory are discussed, including botany, physiology of plants, introduction of plants, genetics and breeding of plants, ecology, preventing the loss of global and loca biodiversity, arboriculture, forest-growing and other biological sciences

Hydrogeochemical characterization of an evaporite karst area affected by sinkholes (Ebro Valley, NE Spain)

The main processes controlling the hydrochemistry of an alluvium-covered evaporite karst area with high sinkhole risk (Ebro Valley, NE Spain) are examined by means of multivariate analyses (Principal Component Analysis and Hierarchical Cluster Analysis), ion correlations and geochemical speciation-solubility calculations. The hydrogeochemistry of the studied system seems to be governed by the interaction between the groundwater from the salt-bearing evaporitic karst aquifer and from the overlying Ebro River alluvial aquifer. The observed hydrochemical features in the alluvial-karst aquifer system are mainly determined by the relative contribution of gypsum/anhydrite and halite dissolution, showing a wide spectrum from relatively fresh recharge waters (mainly irrigation waters) to highly evolved groundwater from the evaporitic aquifer. The variability of these contributions is especially evident at sinkhole ponds which, in some cases, seem to be associated with discharge areas of the karst aquifer in the valley bottom alluvium. Calculated saturation indexes suggest that, in contrast to gypsum, the amounts of halite in the sampled portions of evaporitic aquifer are not large enough to attain equilibrium, which is consistent with the predominance of gypsum/anhydrite reported for these materials. Furthermore, the observed Na:Cl and Ca:SO4 correlations and stoichiometries suggest that other possible processes, such as glauberite dissolution or Na/Ca-exchange, generally play a minor role (compared to halite and gypsum dissolution) in this system. Another important process in the system is the dissolution of carbonate minerals (dolomite and, possibly, calcite) fostered by the input of CO2(g), which is probably produced by pedogenic processes. Dolomite dissolution seems to be particularly relevant in the evaporitic materials probably due to dedolomitisation triggered by gypsum/anhydrite dissolution

Ground water and climate change

As the world’s largest distributed store of fresh water, ground water plays a central part in sustaining ecosystems and enabling human adaptation to climate variability and change. The strategic importance of ground water for global water and food security will probably intensify under climate change as more frequent and intense climate extremes (droughts and floods) increase variability in precipitation, soil moisture and surface water. Here we critically review recent research assessing the impacts of climate on ground water through natural and human-induced processes as well as through groundwater-driven feedbacks on the climate system. Furthermore, we examine the possible opportunities and challenges of using and sustaining groundwater resources in climate adaptation strategies, and highlight the lack of groundwater observations, which, at present, limits our understanding of the dynamic relationship between ground water and climate

Petrographical and geochemical evidences for paragenetic sequence interpretation of diagenesis in mixed siliciclastic–carbonate sediments: Mozduran Formation (Upper Jurassic), south of Agh-Darband, NE Iran

The Upper Jurassic Mozduran Formation with a thickness of 420 m at the type locality is the most important gas-bearing reservoir in NE Iran. It is mainly composed of limestone, dolostone with shale and gypsum interbeds that grade into coarser siliciclastics in the easternmost part of the basin. Eight stratigraphic sections were studied in detail in south of the Agh-Darband area. These analyses suggest that four carbonate facies associations and three siliciclastic lithofacies were deposited in shallow marine to shoreline environments, respectively. Cementation, compaction, dissolution, micritization, neomorphism, hematitization, dolomitization and fracturing are diagenetic processes that affected these sediments.Stable isotope variations of δ18O and δ13C in carbonate rocks show two different trends. High depletion of δ18O and low variation of δ13C probably reflect increasing temperatures during burial diagenesis, while the higher depletion in carbon isotope values with low variations in oxygen isotopes are related to fresh water flushing during meteoric diagenesis. Negative values of carbon isotopes may have also resulted from organic matter alteration during penetration of meteoric water. Fe and Mn enrichment with depletion of δ18O also supports the contention that alteration associated with higher depletion in carbon isotope values with low variations in oxygen isotopes took place during meteoric diagenesis. The presence of bright luminescence indicates redox conditions during precipitation of calcite cement

Microbial and Chemical Characterization of Underwater Fresh Water Springs in the Dead Sea

Due to its extreme salinity and high Mg concentration the Dead Sea is characterized by a very low density of cells most of which are Archaea. We discovered several underwater fresh to brackish water springs in the Dead Sea harboring dense microbial communities. We provide the first characterization of these communities, discuss their possible origin, hydrochemical environment, energetic resources and the putative biogeochemical pathways they are mediating. Pyrosequencing of the 16S rRNA gene and community fingerprinting methods showed that the spring community originates from the Dead Sea sediments and not from the aquifer. Furthermore, it suggested that there is a dense Archaeal community in the shoreline pore water of the lake. Sequences of bacterial sulfate reducers, nitrifiers iron oxidizers and iron reducers were identified as well. Analysis of white and green biofilms suggested that sulfide oxidation through chemolitotrophy and phototrophy is highly significant. Hyperspectral analysis showed a tight association between abundant green sulfur bacteria and cyanobacteria in the green biofilms. Together, our findings show that the Dead Sea floor harbors diverse microbial communities, part of which is not known from other hypersaline environments. Analysis of the water’s chemistry shows evidence of microbial activity along the path and suggests that the springs supply nitrogen, phosphorus and organic matter to the microbial communities in the Dead Sea. The underwater springs are a newly recognized water source for the Dead Sea. Their input of microorganisms and nutrients needs to be considered in the assessment of possible impact of dilution events of the lake surface waters, such as those that will occur in the future due to the intended establishment of the Red Sea−Dead Sea water conduit

Contamination of groundwater under cultivated fields in an arid environment, central Arava Valley, Israel

The purpose of this study is to obtain a better understanding of groundwater contamination processes in an arid environment (precipitation of 50 mm/year) due to cultivation. Additional aims were to study the fate of N, K, and other ions along the whole hydrological system including the soil and vadose zone, and to compare groundwater in its natural state with contaminated groundwater (through the drilling of several wells). A combination of physical, chemical, and isotopic analyses was used to describe the hydrogeological system and the recharge trends of water and salts to the aquifers. The results indicate that intensive irrigation and fertilization substantially affected the quantity and quality of groundwater recharge. Low irrigation efficiency of about 50% contributes approximately 3.5–4 million m3/year to the hydrological system, which corresponds to 0.65 m per year of recharge in the irrigated area, by far the most significant recharge mechanism. Two main contamination processes were identified, both linked to human activity: (1) salinization due to circulation of dissolved salts in the irrigation water itself, mainly chloride, sulfate, sodium and calcium, and (2) direct input of nitrate and potassium mainly from fertilizers. The nitrate concentrations in a local shallow groundwater lens range between 100 and 300 mg/l and in the upper sub-aquifer are over 50 mg/l. A major source of nitrate is fertilizer N in the excess irrigation water. The isotopic compositions of δ15N–NO3 (range of 4.9–14.8‰) imply also possible contributions from nearby sewage ponds and/or manure. Other evidence of contamination of the local groundwater lens includes high concentrations of K (20–120 mg/l) and total organic carbon (about 10 mg/l)