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In this paper, the generation of inorganic carbon (mainly HCO3−) in a karst system (soil-limestone system) under karst soil and non-karst soil conditions was investigated using two Zn2+ concentrations and water flow rates. The results showed that (1) the dynamic equilibrium state of the chemical weathering of limestone is altered by Zn2+, which is the primary cause of the change in HCO3− in soil-limestone systems; (2) ion exchange and adsorption are the primary characteristics of Zn2+ depletion under 1 mg/L ZnCl2 settings, whereas Zn2+ under 50 mg/L ZnCl2 conditions created two new solid phases (Zn5(OH)6(CO3)2, ZnCO3) in the soil-limestone system; (3) the dissolution rate of limestone increases with the water flow rate, which facilitates the dissolution process; (4) the notable difference in ion release between non-karst and karst soil conditions could potentially be attributed to variations in the mineral composition, specific surface area, and particle size of the two soil types; (5) the combination of SEM, XPS, FT-IR, and XRD microstructure observation methods reveals that when limestone is exposed to a high flow rate (1.23 mL/min) and a high concentration (50 mg/L) of ZnCl2, it experiences obvious dissolution and surface precipitation phenomena, as well as a significant change in HCO3− content. [ABSTRACT FROM AUTHOR]

The engineering construction of karst city is often affected by karst geological hazards. Guilin City is a typical representative of karst city; therefore, we should consider the influence of karst hazards when analyzing the suitability for engineering construction in planned urban areas of Guilin. In this study, we established a method for evaluating the construction suitability based on the analytic hierarchy process (AHP) on the geographic information system (GIS) platform. Firstly, the landform of planned urban areas in Guilin is mainly composed of peak-cluster depression, peak-forest valley, peak-forest plain, isolated peak plain, karst-ridge valley, karst-hill plain, low mountain with steep hillslope, hill, hill with gentle slope, and undulating hills. The areas intensely developed with karst are mainly located along the banks of the Lijiang River and in the Lingui district. The areas with karst development at a medium level are located in the middle and southwestern parts of Guilin City and on the periphery of the Lijiang River banks. The areas with weak karst development are mainly located at the Yanshan district, Dingjiang town, and southwestern Lingui district. The groundwater types of the study area are mainly composed of carbonate karst water, impure carbonate cave-fissure water, and clastic bedrock fissure water. For the suitability evaluation of engineering construction in planned urban areas of Guilin, the topographic slope, geomorphic unit, bearing capacity of soil foundation, bearing capacity of rock foundation, special soil distribution, soil thickness, soil structure, groundwater depth, surface water system, karst influence, and fault factors are selected as evaluation indexes, all of which have passed the consistency test of judgment matrix. The weight of these eleven evaluation indexes was calculated by AHP. Then, the engineering construction suitability index (P) was computed from multi hierarchy evaluation with AHP. The P values can be classified as P≥5.00, 2.50≤P<5.00, 1.00≤P<2.50, and P<1.00, which may respectively fall into the category of suitable area, relatively suitable area, poorly suitable area, and unsuitable area for engineering construction. The zoning of planned unban areas in Guilin was visualized based on the suitability for engineering construction on the GIS spatial platform. Finally, in terms of the zoning based on suitability for engineering construction, six sites were chosen and were verified that the zoning by AHP method is consistent with that by field engineering drilling surveys. The consistency may indicate the reliability of APH method with GIS platform. Main conclusions can be drawn as follows,(1) The impact indexes of suitability for engineering construction of the study area include topography (slope degree and geomorphic unit), engineering geological conditions (bearing capacity of soil foundation, bearing capacity of rock foundation, special soil distribution, soil thickness and soil structure), hydrological conditions (groundwater depth and surface water system), and unfavorable geological condition (karst influence and fault factors). (2) Planned urban areas in Guilin are generally suitable for engineering construction, because suitable and relatively suitable areas account for 3.1% and 48.3% of the total area respectively, which can meet the land use needs of recent urban development planning and major infrastructure projects. However, the poorly suitable areas account for 11.4%, which are unsuitable for large-scale engineering construction and require necessary engineering treatment in practical construction. Unsuitable areas account for 37.2%, mostly located at medium-sized mountain, peak-cluster, and isolated peak. The site selection of major construction should be avoided in the unsuitable area. (3) If the major construction site is selected in a poorly suitable area, measures should be taken to prevent and control the existing and induced geological disasters and uneven settlement of foundations. The unsuitable area is proposed to be planned as the ecological land, which can serve as the ecological barrier for Guilin. [ABSTRACT FROM AUTHOR]

The relief is formed by the conjunction of processes that can be influenced to a greater or lesser extent by the morphostructure or morphosculpture, both of which act in the formation of the landscape. This work aims to, through the analysis of relief formation, provide subsidies for the studies of the run-off and the groundwater in an area of carbonate rocks in the north of Minas Gerais. The geomorphological landscape of this area is strongly influenced by morphostructural factors. Such influence is observed in the rectilinear drainage pattern of some rivers, in the presence of structural valleys, in abrupt changes in the direction of drainage net, and in scarps aligned in the same direction of joints and faults present in the area. Such structural influence is quite clear in the southern and central portions of the study area, being less significant in the northern portion, which has a much higher concentration of sinkholes than what was observed in the other areas. Considering a systemic perspective of the processes and dynamics that act on the surface and underground, this work presents these results of the formation of the geomorphological landscape so that such analysis helps in understanding the dynamics of groundwater in this area, as well as the relationship between surface waters and underground.

In this paper, the generation of inorganic carbon (mainly HCO3−) in a karst system (soil-limestone system) under karst soil and non-karst soil conditions was investigated using two Zn2+ concentrations and water flow rates. The results showed that (1) the dynamic equilibrium state of the chemical weathering of limestone is altered by Zn2+, which is the primary cause of the change in HCO3− in soil-limestone systems; (2) ion exchange and adsorption are the primary characteristics of Zn2+ depletion under 1 mg/L ZnCl2 settings, whereas Zn2+ under 50 mg/L ZnCl2 conditions created two new solid phases (Zn5(OH)6(CO3)2, ZnCO3) in the soil-limestone system; (3) the dissolution rate of limestone increases with the water flow rate, which facilitates the dissolution process; (4) the notable difference in ion release between non-karst and karst soil conditions could potentially be attributed to variations in the mineral composition, specific surface area, and particle size of the two soil types; (5) the combination of SEM, XPS, FT-IR, and XRD microstructure observation methods reveals that when limestone is exposed to a high flow rate (1.23 mL/min) and a high concentration (50 mg/L) of ZnCl2, it experiences obvious dissolution and surface precipitation phenomena, as well as a significant change in HCO3− content.

A systematic assessment of the variations in the ecological risk of PAHs and the key emission sources controlling the variations is of great importance to human health and aquatic organisms. PAH concentrations, composition, source, and ecological risk in soils and water in two different periods (2010–2011 and 2019) of three typical epikarst springs in Southwest China were investigated. Results showed that PAH concentrations in soil and water have an overall downward trend (a reduction of 57 % and 93 %, respectively) in the past 10 years, which is consistent with the downward trend in the relative contribution rate of raw coal production (a 66 % reduction). In terms of composition, the proportion of low-ring PAHs decreased, medium-ring and high-ring PAHs increased in the soil profile. The proportion of low-ring PAHs did not change obviously, the proportion of medium-ring PAHs increased, and the proportion of high-ring PAHs decreased in epikarst springs. The source of PAHs changed remarkably over time, the relative contribution of coal combustion to PAHs decreased from 38 % to 20 %, and the vehicle contribution of PAHs increased from 31 % to 44 % in soils. The relative contribution rate of unburned oil and coke oven and biomass combustion change is less. Furthermore, the ecological risk of PAHs in the soils was reduced from moderate risk 2 to moderate risk 1, the risk in epikarst spring was reduced from high risk to moderate risk 2 after 10 years. This study demonstrates that substituting petroleum and coal with green energies can reduce PAH concentrations and risk.

The Middle-Upper Proterozoic and Lower Paleozoic carbonate aquifers in northern China are continuously deposited with large thicknesses and wide distribution areas. Karst groundwater plays an critical role in national economic construction due to the rich water resources stored in karst aquifers. It is a national strategic water resource in China. Based on the author's investigation and research experience on karst water in northern China, this work provides a preliminary summary of the research progress and shortcomings in the aspects of karst groundwater systems and hydrogeological conditions, evolution trends and causes of environmental problems, utilization and protection of karst groundwater, ecological restoration and technical methods of investigation and research. This paper sends a congratulation to the 70th anniversary of the establishment of China University of Geosciences and the 40th anniversary of the establishment of the Bulletin of Geological Science and Technology.It also provides a reference for hydrogeological colleagues of karst groundwater research in northern China.

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The presence of karst cavities near the tunnels has a great impact on the behavior and deformation of the tunnels, making it necessary to study the impact of these cavities before starting the tunnel operation. A finite difference software (FLAC3D) was used to study the modeling of tunnels adjacent to karst caves and examine the effect of location, size, distance, shape, and arrangement of caves on displacements, bending moment, and axial force of the tunnel lining. In this study, an attempt has been made to investigate the effect of these karst cavities on the tunnel by approximate modeling of karst cavities around Shiraz-Bushehr railway tunnel. The results show that by increasing the dimensions of the karst cave, the axial force (N) increases when the cave is located below, top, and at the side of the tunnel, respectively. Moreover, when the cave is located below, top, or at the side of the tunnel, the bending moment decreases and increases, respectively. As the distance of the cave increases in the below of the tunnel span, the displacement of the tunnel ceiling increases, while the bending moment and axial force increase and decrease, respectively, depending on the size of the cave. With changing the location of the cave at a certain distance from the span toward the end of the tunnel, the displacement of the tunnel ceiling, bending moment, and axial force of the tunnel lining would decrease. [ABSTRACT FROM AUTHOR]

Grazing is the simplest and most cost-effective way of grassland utilization in the world, and it also has a significant impact on the grassland soil environment. Artificial grassland is an important basis for the development of animal husbandry and an important means to solve the contradiction between grass and livestock. This study analyzed the characteristics of the karst artificial grassland environment, and systematically reviewed the effects of grazing on soil physical and chemical properties, as well as the effects of microorganisms, forage functional traits, and forage quality. We believe that moderate grazing is an effective means of sustainable utilization of the soil environment. At the same time, it is inferred that grazing in the tropical and subtropical karst areas of southern China has a greater impact on grassland species composition, and according to the current situation, the key scientific issues that need to be paid attention to in the study of current grassland grazing and other utilization methods are discussed. [ABSTRACT FROM AUTHOR]

The karst environment is characterized by low soil water content, periodic water deficiency, and poor nutrient availability, which provides an ideal natural laboratory for studying the adaptive evolution of its inhabitants. However, how species adapt to such a special karst environment remains poorly understood. Here, transcriptome sequences of two Urophysa species (Urophysa rockii and Urophysa henryi), which are Chinese endemics with karst-specific distribution, and allied species in Semiaquilegia and Aquilegia (living in non-karst habitat) were collected. Single-copy genes (SCGs) were extracted to perform the phylogenetic analysis using concatenation and coalescent methods. Positively selected genes (PSGs) and clusters of paralogous genes (Mul_genes) were detected and subsequently used to conduct gene function annotation. We filtered 2,271 SCGs and the coalescent analysis revealed that 1,930 SCGs shared the same tree topology, which was consistent with the topology detected from the concatenated tree. Total of 335 PSGs and 243 Mul_genes were detected, and many were enriched in stress and stimulus resistance, transmembrane transport, cellular ion homeostasis, calcium ion transport, calcium signaling regulation, and water retention. Both molecular and morphological evidences indicated that Urophysa species evolved complex strategies for adapting to hostile karst environments. Our findings will contribute to a new understanding of genetic and phenotypic adaptive mechanisms of karst adaptation in plants.

The karst environment is characterized by low soil water content, periodic water deficiency, and poor nutrient availability, which provides an ideal natural laboratory for studying the adaptive evolution of its inhabitants. However, how species adapt to such a special karst environment remains poorly understood. Here, transcriptome sequences of two Urophysa species (Urophysa rockii and Urophysa henryi), which are Chinese endemics with karst-specific distribution, and allied species in Semiaquilegia and Aquilegia (living in non-karst habitat) were collected. Single-copy genes (SCGs) were extracted to perform the phylogenetic analysis using concatenation and coalescent methods. Positively selected genes (PSGs) and clusters of paralogous genes (Mul_genes) were detected and subsequently used to conduct gene function annotation. We filtered 2,271 SCGs and the coalescent analysis revealed that 1,930 SCGs shared the same tree topology, which was consistent with the topology detected from the concatenated tree. Total of 335 PSGs and 243 Mul_genes were detected, and many were enriched in stress and stimulus resistance, transmembrane transport, cellular ion homeostasis, calcium ion transport, calcium signaling regulation, and water retention. Both molecular and morphological evidences indicated that Urophysa species evolved complex strategies for adapting to hostile karst environments. Our findings will contribute to a new understanding of genetic and phenotypic adaptive mechanisms of karst adaptation in plants. [ABSTRACT FROM AUTHOR]

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Research of human settlements on the karst area of East Sarajevo starts with a brief overview of the City's characteristic traits and the influence of relief on the distribution of the population. The karst terrain was mapped using GIS tools, after which the percentage of the population and its concentration on the karst area of the East Sarajevo was determined. Karst areas have a low population density caused by difficult living conditions due to the vertical and horizontal dissection of relief, lack of mineral resources, geodynamic disasters, water shortages, specific climate conditions, degraded land, and vegetation. The consequences are the fragmentation of property, migration and aging of the population, lack of labor, weakening of the economy, etc. The research focus is to determine the degree of the anthropogenic impact on the karst environment and to apply the suitable methodology in the determination of the settlements categories according to the degree of karst environment vulnerability.

Research of human settlements on the karst area of East Sarajevo starts with a brief overview of the City's characteristic traits and the influence of relief on the distribution of the population. The karst terrain was mapped using GIS tools, after which the percentage of the population and its concentration on the karst area of the East Sarajevo was determined. Karst areas have a low population density caused by difficult living conditions due to the vertical and horizontal dissection of relief, lack of mineral resources, geodynamic disasters, water shortages, specific climate conditions, degraded land, and vegetation. The consequences are the fragmentation of property, migration and aging of the population, lack of labor, weakening of the economy, etc. The research focus is to determine the degree of the anthropogenic impact on the karst environment and to apply the suitable methodology in the determination of the settlements categories according to the degree of karst environment vulnerability. [ABSTRACT FROM AUTHOR]

A systematic assessment of the variations in the ecological risk of PAHs and the key emission sources controlling the variations is of great importance to human health and aquatic organisms. PAH concentrations, composition, source, and ecological risk in soils and water in two different periods (2010–2011 and 2019) of three typical epikarst springs in Southwest China were investigated. Results showed that PAH concentrations in soil and water have an overall downward trend (a reduction of 57 % and 93 %, respectively) in the past 10 years, which is consistent with the downward trend in the relative contribution rate of raw coal production (a 66 % reduction). In terms of composition, the proportion of low-ring PAHs decreased, medium-ring and high-ring PAHs increased in the soil profile. The proportion of low-ring PAHs did not change obviously, the proportion of medium-ring PAHs increased, and the proportion of high-ring PAHs decreased in epikarst springs. The source of PAHs changed remarkably over time, the relative contribution of coal combustion to PAHs decreased from 38 % to 20 %, and the vehicle contribution of PAHs increased from 31 % to 44 % in soils. The relative contribution rate of unburned oil and coke oven and biomass combustion change is less. Furthermore, the ecological risk of PAHs in the soils was reduced from moderate risk 2 to moderate risk 1, the risk in epikarst spring was reduced from high risk to moderate risk 2 after 10 years. This study demonstrates that substituting petroleum and coal with green energies can reduce PAH concentrations and risk. • A decrease in PAH concentrations and risk in epikarst catchments over the last decade. • The decrease in PAH concentrations in groundwater is more sensitive than soil. • Analysis revealed that PAHs in soils were mainly derived from coal, biomass, and vehicles. • Substituting petroleum and coal with green energies decreased PAH concentrations and risk. [ABSTRACT FROM AUTHOR]

Copyright of Revista Ingeniare is the property of Universidad Libre Seccional Barranquilla and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Karst environment become an alternative tourist destination as well as to boost local revenues. In karst environments in Grobogan District, Central Java Province, formed Urang Cave, with an interesting endokarst phenomenon. This study aims to do zoning district Urang Cave as tourist sites. The research method is using contour maps as a base map of Urang Cave karst environment geomorphological mapping. Geomorphological data processing is using ArcView GIS 3.3 program. Land use map refers to RBI, scale 1:25.000. Geomorphological analysis refers to the Ministry of Energy and Mineral Resources No. 1456.K/20/MEM/2000, and petrography. Each development zone is analyzed its geophysical environmental element, then set scoring and value summation. For comprehensive environmental element analysis, chemical analysis of rocks, and water-soil chemistry. In reference to Minister of Energy Mineral Resource decrees No. 1456/K/20/MEM/2000, Urang Cave zoning defined into 3 (three) zone, as follow: the Protected Zone, Cultivation Zone 1, and Cultivation Zone 2. Protected Zone, consists of Urang Cave tunnel/hallway with a unique spheleothem in it. This zone as a cave tracking site tourism, potential to produce karst water as a decent drinking water while maintaining hardness. Cultivation Zone 1 is spreading about 200 m in distance from outer appearance of spring around the cave hallway. In this zone mining of cave sediments may be done in the inactive form caves, without changing the state of the existing major exokarst morphology. Cultivation Zone 2, an outer zone, located farthest from the tunnel/hallway Urang Cave. Utilization of this zone as a limestone mining quarry, although only on a small scale.

This study investigated CO2 degassing and related carbon isotope fractionation effects in the Wiesent River that drains a catchment in the karst terrain of the Franconian Alb, Southern Germany. The river was investigated by physico-chemical and stable isotope analyses of water and dissolved inorganic carbon during all seasons along 65-km long downstream transects between source and mouth. Calculated pCO2 values at the source were 21 400 ± 2400 µatm. The pCO2 rapidly decreased in the river water and dropped to an average of 1240 ± 330 µatm near the mouth. About 90% of this decrease occurred within the first 6 km of the river. The river was supersaturated with respect to CO2 over its entire course and must have acted as a continuous year-round CO2 source to the atmosphere. The average CO2 flux from the karst river was estimated with 450 mmol m−2 day−1 with higher fluxes up to 5680 mmol m−2 day−1 at the source. At the source, δ13CDIC values showed no seasonal variations with an average of −14.2 ± 0.2‰. This indicated that groundwater retained high pCO2 mainly from soil CO2. The contribution of soil CO2 to dissolved inorganic carbon was estimated at 65% to 72%. The downstream CO2 loss caused a positive shift in δ13CDIC values of 2‰ between source and mouth because of the preferential loss of the 12C isotope during degassing. Considering the findings of this study and the fact that carbonate lithology covers a significant part of the earth's surface, CO2 evasion from karst regions might contribute notably to the annual carbon dioxide release from global freshwater systems. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Migration and concentration of heavy metals in infiltration waters within unsaturated and saturated zones of a carbonate massif result from their mobility as well as anthropopression. The purpose of this project, carried out in 1995-2005, was to observe changes in the chemical composition of infiltration waters, especially Sr, Ba, Fe, Mn, and Zn concentration in precipitations, in soils and in caves within an unsaturated zone and a saturated zone situated in a carbonate massif. Field research was conducted in the Prądnik River's drainage basin and at the Zakrzówek horst in Kraków. The chemical and mineralogical composition of limestone samples from 11 different quarries and natural exposures in the Kraków Upland were studied. The mineralogical research was conducted using the Roentgen diffraction method. The concentration of Sr, Ba, Fe, Mn and Zn in 700 samples from precipitation, caves and saturated zone waters was analysed. The determinations were made using mainly the ICP-AES Plasma 40 and ICP-MS Elan method. To assess the quality aspects of the migration of heavy metals, the results of the geochemical modelling were accounted for using the PHREEQC software. The hydrochemical research has shown distinct variability of concentrations of the analysed minor elements in different forms of precipitation (the highest concentrations being observed in sleet and the lowest in pure snowfall). In rainwater as well as in waters of the unsaturated and saturated zones, quantities of the five chemical elements appeared in the following decreasing order: Fe>Zn>Mn>Sr>Ba and Sr>Ba>Fe>Zn>Mn. The chemical composition of infiltration waters in the carbonate massif changes vertically. The fundamental trends in the waters of this area include an increase of Sr and Ba concentrations, a decrease of the concentration of Zn, and static concentrations of Fe and Mn. [ABSTRACT FROM AUTHOR]

To study the effects of low nutrition on photosynthetic capacity and accumulation of total nitrogen (N) and phosphorus (P) in three climber plant species, Pharbitis nil (Linn.) Choisy, Lonicera japonica Thunb. and Parthenocissus tricuspidata (Sieb.et Zucc.) Planch, all climber plants were exposed to low nutrition at 6 levels (Hoagland solution as control, 1/2, 1/4, 1/8, 1/16 and 1/32-strength Hoagland solution) for 30 days. Photosynthetic capacity was determined by measuring leaf chlorophyll fluorescence, chlorophyll content, carbonic anhydrases activity and growth. Accumulation of total N and P was studied by measuring N and P content in plant tissues. Low nutrition decreased the photosynthetic capacity of P. nil, while L. japonica maintained high photosynthetic capacity under low nutrition. Photosynthetic apparatus of P. tricuspidata suffered no damage when exposed to low nutrition. L. japonica and P. tricuspidata had better adaptability to low nutrition than P. nil. With a faster growth rate, P. nil consumed more nutrition (N and P), and its growth was mainly affected by P deficiency under low nutrition. Although L. japonica suffered damage from N and P deficiency simultaneously, but the nutrient deficiency was not serious except for 1/32-strength Hoagland solution. P. tricuspidata grew slowly, so its requirement of N and P were the least, even if it was mainly affected by the P deficiency, it could still grow well under low nutrition. With the consideration of fertilizing N and P fertilizers in karst areas which were with lower N and P contents, plant species, N/P ratio threshold and low nutrition level should be taken into account synchronously. This study could provide a general consideration for the planning and developing low nutrition resistant plants and fertilizing the three climber plant species in the low nutrition environment. [ABSTRACT FROM AUTHOR]

The dynamics and distribution of the carbonate system and the processes that regulate it over the Yucatan Shelf (YS), a region of karst geology and high productivity that is influenced by submarine groundwater discharges (SGDs) and upwelling, were explored with data from two oceanographic cruises. The first oceanographic cruise was conducted in November 2015 during the Nortes season, a period of intense northerly wind activity, and a second cruise was conducted during the rainy season in August/September 2016. Notable biogeochemical differences were present between them. At the surface, Caribbean Surface Water (CSW) predominated over the shelf in both periods. During the Nortes cruise, a surface nearshore-offshore gradient showed high dissolved inorganic carbon (DIC; ∼2470 μmol kg−1) and total alkalinity (TA; ∼2460 μmol kg−1) values near the coast and average pH Total and pCO 2 values of 7.42 ± 0.10 and 2206 ± 546 μatm, respectively. These geochemical characteristics were attributed to the influence of SGDs, punctuated by relatively low δ13C DIC values between −4.18‰ and −2.49‰, which reflects an important oxidation of organic carbon and the dissolution of carbonate minerals. The presence of upwelled water on the eastern side of the YS showed average DIC and pH Total values of 2260 ± 15 μmol kg−1 and 7.69 ± 0.08, respectively, which were lower than coastal values. During the rainy cruise, the advection of CSW by the Yucatan Current was traced by its thermohaline properties. However, the surface water carbonate system was relatively homogeneous, with average DIC, TA, pH Total , and pCO 2 values of 2047 ± 16 μmol kg−1, 2388 ± 11 μmol kg−1, 8.02 ± 0.02, and 440 ± 27 μatm, respectively. Lastly, the δ13C DIC values during this cruise ranged from −1.21‰ to 1.25‰, which suggests that the carbonate system is mainly regulated by organic matter production and respiration. • The carbonate system (CS) of the Yucatan Shelf remains inadequately characterized. • CS variation depends on water mass advection and submarine groundwater discharge. • The CS is influenced by seasonality. • Organic matter respiration and CaCO 3 dissolution influenced the CS in Nortes season. • Caribbean Surface Water and high evaporation influenced the CS in the rainy season. [ABSTRACT FROM AUTHOR]

An evaluation of the quality status of the pristine karst, tufa depositing aquatic environment of the Plitvice Lakes National Park based on the analysis of heavy (ecotoxic) metals was examined for the first time. Analyses of trace metals in water, sediment and fish ( Salmo trutta, Oncorhynchus mykiss, Squalius cephalus) samples were conducted either by stripping voltammetry (Zn, Cd, Pb and Cu) or cold vapour atomic absorption spectrometry (Hg). The concentration of dissolved trace metals in water was very low revealing a pristine aquatic environment (averages were, in ng/L: 258 (Zn), 10.9 (Cd), 11.7 (Pb), 115 (Cu) and 1.22 (Hg)). Slightly enhanced concentrations of Cd (up to 50 ng/L) and Zn (up to 900 ng/L) were found in two main water springs and are considered as of natural origin. Observed downstream decrease in concentration of Cd, Zn and Cu in both water and sediments is a consequence of the self-purification process governed by the formation and settling of authigenic calcite. Anthropogenic pressure was spotted only in the Kozjak Lake: Hg concentrations in sediments were found to be up to four times higher than the baseline value, while at two locations, Pb concentrations exceeded even a probable effect concentration. The increase of Hg and Pb was not reflected on their levels in the fish tissues; however, significant correlations were found between Cd level in fish tissues (liver and muscle) and in the water/sediment compartments, while only partial correlations were estimated for Zn and Cu. A high discrepancy between values of potentially bioavailable metal fraction estimated by different modelling programs/models raised the question about the usefulness of these data as a parameter in understanding/relating the metal uptake and their levels in aquatic organism. The aquatic environment of the Plitvice Lakes National Park is characterized, in general, as a clean ecosystem. [ABSTRACT FROM AUTHOR]

Abstract: The extinction of late Quaternary megafauna in South America has been extensively debated in past decades. The majority of the hypotheses explaining this phenomenon argue that the extinction was the result of human activities, environmental changes, or even synergism between the two. Although still limited, a good chronological framework is imperative to discuss the plausibility of the available hypotheses. Here we present six new direct AMS 14C radiocarbon dates from the state of São Paulo (Brazil) to further characterize the chronological distribution of extinct fauna in this part of South America. The new dates make evident that ground sloths, toxodonts, and saber-toothed cats lived in the region around the Pleistocene/Holocene transition, and, in agreement with previous studies, also suggest an early Holocene survival for the ground sloth Catonyx cuvieri. Taken together with local paleoclimatic and archaeological data, the new dates do not support hunting or indirect human activities as a major cause for megafauna extinction. Although more data are required, parsimony suggests that climatic changes played a major role in this extinction event. [Copyright &y& Elsevier]

Summary: A system approach, daily precipitation-streamflow model was developed for both the base and the surface flow components, of large-scale karst basins. Long-term streamflow data were separated to baseflow and surface flow using the “recursive digital filter” method, which provides time series for model calibration. The HYdrological Model for Karst Environment (HYMKE) includes attributes to large-scale preferential flow that recharge the groundwater and solve the problem of uncorrelated baseflow and surface flow in a karst environment. HYMKE was applied simultaneously to the three major tributaries of the Upper Catchment of the Jordan River, which originate in the karstic region of the Hermon Mountain (Northern Israel). It was verified by comparing the calculated surface flow and baseflow with the daily time series of the baseflow separation procedure, and demonstrated good agreement of both the surface (r 2 >0.6) and baseflow (r 2 >0.77) components of each stream. [Copyright &y& Elsevier]

Guizhou Province is one of the least developed areas with the largest number of counties in poverty and the widest coverage of karst landscape in China. The vulnerability of its karst eco-environment seriously threatens the survival of local residents and the development of local economy. Rapid population growth results in higher demand of various resources, which leads to more intensive development activities. For example, the blindfolded development on steep slopes has caused rock desertification of local rare soil in this karst area. It has induced a vicious circle in the poverty→population growth→ecosystem degradation and so on. About 3.13 × 106 people belong to the absolute impoverished population in Guizhou Province and most of them are living in rock-desertification areas. The essential reasons for destitution are the atrocious eco-environment and the huge population stress. Degradation of mountain ecosystems in southwestern China has continued at unprecedented speed and scale in recent decades. It is necessary to control population growth strictly and prevent further expansion of rock-desertification in order to develop local economy and better living conditions for local people. The only way to ensure a sustainable, stable and harmonious development of human, nature and economy is to restore a good condition of eco-environment and resolve the conflicts between human and land use. [ABSTRACT FROM AUTHOR]

Integrated geophysical investigations of karst structures were carried out in Liguria and Piedmont (NW Italy); this paper refers to the S. Pietro dei Monti doline, in the karst area of Mt. Carmo (Savona). The techniques used in the integrated study were magnetics, electromagnetics and seismic refraction. The target was to identify, without drilling, the nature of the doline, for example if it is of dissolution or collapse type. A preliminary susceptibility sampling of the outcrop and topsoil and the diffuse fractures with a probable water seepage suggested magnetics and VLF electromagnetics. Such methods applied in an area with an extremely low cultural noise allowed modelling of the buried structure of the doline.

• HCO 3 − use mechanism shifted in Ottelia guanyangensis from up- to downstream. • Carbonic anhydrase and anion exchange mediated HCO 3 − use in Vallisneria denseserrulata. • pH-polarity leaves found in O. guanyangensis but not in V. denseserrulata. • Carbon source and HCO 3 − use mode determined δ13C in these two macrophytes. Macrophytes live in extremely different carbon environments compared to terrestrial plants. In response to bicarbonate dominated inorganic carbon in natural aquatic systems, the ability for HCO 3 − use has been developed in many macrophytes to alleviate a limitation by CO 2 in aquatic systems. In the present study, all present macrophytes in a karst stream were investigated, and we found that seven of nine species were able to use HCO 3 − and two species at the source of the karst stream were restricted to CO 2 use. Two different inhibitors were used to determine the HCO 3 − use mechanisms in Ottelia guanyangensis and Vallisneria denseserrulata , the only species coexisting from up- to down-stream. External carbonic anhydrase (CAext) mediated HCO 3 − use was present in O. guanyangensis up-stream, and then O. guanyangensis shifted to a combined mechanism of CAext and anion exchange (AE) mediated HCO 3 − use down-stream. In these two species, high HCO 3 − concentration induced the ability to use HCO 3 −, but high CO 2 concentration inhibited this ability. From up-stream to down-stream, the decreasing CO 2 induced increasing proportion of HCO 3 − use that led to changes in the δ13C in O. guanyangensis. However, a constant CAext and AE mediated HCO 3 − use caused a relatively stable δ13C in V. denseserrulata from river source to 330 m and then increased the proportion of HCO 3 − use at the stream outlet associated with the change in δ13C. [ABSTRACT FROM AUTHOR]