Implications of chloride-enhanced cadmium uptake in saline agriculture: modeling cadmium uptake by maize and tobacco

Chloride salinity has been strongly related to enhanced cadmium (Cd) uptake by plants due to increased solubility in the soil solution, even in agricultural soil with very low levels of cadmium. This finding is relevant because the cadmium content of food crops is an important concern for human health. Therefore, the aim of this study was to predict and discuss the chlorine-enhanced uptake of cadmium by two common crops: maize and tobacco under ??non-saline?? (1?mM) and ??very strongly saline?? (200?mM) scenarios using a modified ??biotic ligand model?? and datasets from a set of soil and hydroponic experiments. Results indicated that predicted cadmium uptake rates (expressed as cadmium in plant ??mol?m^?2 root) by maize and tobacco plants were consistently higher (54 and 15%, respectively) assuming conditions of ??very strong salinity?? soil compared to the simulated ??non-saline?? soil. In the light of the results of the present research, valuable information is given on modeled cadmium phytoavailability as an indication of the potential risk due to increased cadmium uptake by crops under saline conditions, especially as the enhancement of cadmium uptake in the presence of Cl^? salinity may be a general trend that occurs in many edible crops. The biotic ligand model parameterization applied in the present study attempted to simulate conditions commonly found in natural cadmium and salt-affected soils. However, caution is needed to extrapolate results obtained from these models to real soil conditions.     

Palynology suggests hydrocarbon mobilization in Ordovician of Kasba Tadla Basin,Morocco

Palynological analysis of twelve wells shows that the metamorphic gradient of the pre-Mesozoic in the Kasba Tadla Basin of Morocco increases rapidly northwest-, southeast-, and eastward, from the center of the Basin. In the center, the Ordovician may still be releasing mobile hydrocarbons.

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Zusammenfassung Eine palynologische Untersuchung von zwölf Bohrungen zeigt, daß der thermale Gradient sich im Premesozoikum des Kasba-Tadla-Beckens in Marokko vom Zentrum des Beckens aus nach Nordwesten, Südosten und Osten schnell vergrößert. Es ist sehr wohl möglich, daß das Ordovizium des Beckenzentrums noch flüssige und gasförmige Kohlenwasserstoffverbindungen abgibt.

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Résumé L'analyse palynologique de 12 sondages montre que le gradient métamorphique du pré-Mésozoïque dans le Basin du Kasba Tadla, au Maroc, augmente à partir du centre du Bassin vers le nordouest, le sudest et vers l'est. Il est possible que l'Ordovicien de la partie centrale du Bassin produise encore des hydrocarbures liquides et gaseux.

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12 , Kasba Tadla -, - . , .

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The authors gratefully acknowledge support of this project through Grant GF-32510-X from the National Science Foundation, Washington, D.C., U.S.A.     

Pravčice Rock Arch (Bohemian Switzerland National Park, Czech Republic) deterioration due to natural and anthropogenic weathering

The dominant factors affecting the development of weathering forms on the Prav?ice Rock Arch (PRA) (Bohemian Switzerland National Park, Czech Republic) are discussed, based on the in situ monitoring of weathering forms, as well as on laboratory studies of materials taken from this site. The in situ monitoring shows the progressive development of distinct weathering forms (delamination of case-hardened rock surfaces, cyclic efflorescence, and granular disintegration of exposed weakly cemented rock mass) in specific portions of the PRA, whose location is controlled by lithology, jointing/local hydrodynamics, and exposure to climatic factors. From the analysis of efflorescence, the dominance of sulphates is evident; particularly of gypsum and alums. However, the synergistic effects of the several salt species (that also include minor nitrates and chlorides) upon the mechanical disintegration of sandstone can be expected.     

A geologic study of the Juan del Grijalva landslide,the most important mass movement during the last century in Mexico

On November 4th 2007, along the Grijalva River in the state of Chiapas, Mexico, has occurred one of the largest landslides ever known. This landslide, known as Juan del Grijalva, destroyed the town of the same name, killing 20 people, and moved 55 million cubic meters of rock and debris down slope to completely block the Grijalva River. In order to understand the characteristics and factors that triggered the Juan del Grijalva landslide, geologic studies were conducted at the site. The results indicate that the landslide was composed of a lithologic sequence of thin-bedded shales and thin to medium-thick-bedded sandstones. This was faulted into several blocks dipping in the same sense as the mass movement. The main triggering factor was the increment of the pore pressure into the lithologic unit due to water saturation after 5 days of heavy rain before the incident. According to records from the last century, the Juan del Grijalva mass movement represents one of the largest mass movements recorded all over the world. The risk conditions of the area after the landslide lead to the rapid construction of an artificial channel to drain the accumulating mass of water upstream and therefore prevent a future catastrophic inundation down stream.     

Environmental risk evaluation of the use of mine spoils and treated sewage sludge in the ecological restoration of limestone quarries

The ecologic restoration criteria in areas degraded from extraction activities require making use of their mine spoils. These materials do not meet fertility conditions to guarantee restoration success and therefore, need the incorporation of organic amendments to obtain efficient substratum. Reducing the deficiencies in the organic material and restoration material nutrients with the contribution of treated sewage sludge is proposed in this work. This experiment was based on a controlled study using columns. The work was conducted with two mine spoils, both very rich in calcium carbonate. The first mineral, of poor quality, came from the formation of aggregates of crushed limestone (Z). The other residual material examined originated in limestone extraction, formed by the levels of interspersed non-limestone materials and the remains of stripped soils (D). Two treatments were undertaken (30,000 and 90,000 kg/ha of sewage sludge), in addition to a control treatment. The water contribution was carried out with a device that simulated either short-duration rain or a flooding irrigation system in order to cover the surface and then percolate through the soil. The collection of leached water took place 24 h after the applications. Different parameters of the leached water were determined, including pH, electrical conductivity, nitrate anions, ammonium, phosphates, sulphates and chlorides. The values obtained for each irrigation application are discussed, and the nitrate values obtained were very elevated.     

Biaxial test simulations using a packing of polygonal particles

The mechanical response of cohesionless granular materials under monotonic loading is studied by performing molecular dynamic simulations. The diversity of shapes of soil grains is modelled by using randomly generated convex polygons as granular particles. Results of the biaxial test obtained for dense and loose media show that samples achieve the same void ratio at large strains independent of their initial density state. This limit state resembles the so‐called critical state of soil mechanics, except for some stress fluctuations, which remain for large deformations. These fluctuations are studied at the micro‐mechanical level, by following the evolution of the co‐ordination number, force chains and the fraction of the sliding contacts of the sample. Copyright © 2007 John Wiley & Sons, Ltd.     

Web-GIS tool for the management of rural land markets

Land abandonment and stagnation of rural markets in the last few years have become one of the main concerns of rural administrations. The use of Web and GIS (Geographic Information System) technologies can help to mitigate the effects of these problems. This paper pro-poses a novel Web-GIS tool with spatial capabilities for the dynamization of rural land markets by encouraging the transfer of land from owners to farmers through the leasing of plots. The system, based on open source software, offers information about the properties, their environment and their owners. It uses standards for handling the geographic information and for communicating with external data sources. This system was used as the basis for the development of SITEGAL, the tool for the management of the Land Bank of Galicia (www.bantegal.com/sitegal). SITEGAL has been operational since 2007 obtaining benefits for both administration and users (farmers and land owners), and promoting the e-Government.     

Chemical Dynamics and Evaluation of Biogeochemical Processes in Alpine River Kamniška Bistrica, North Slovenia

Biogeochemical processes were investigated in alpine river—Kamni?ka Bistrica River (North Slovenia), which represents an ideal natural laboratory for studying anthropogenic impacts in catchments with high weathering capacity. The Kamni?ka Bistrica River water chemistry is dominated by HCO₃ ^?, Ca²⁺ and Mg²⁺, and Ca²⁺/Mg²⁺ molar ratios indicate that calcite weathering is the major source of solutes to the river system. The Kamni?ka Bistrica River and its tributaries are oversaturated with respect to calcite and dolomite. pCO₂ concentrations were on average up to 25 times over atmospheric values. δ¹³C_DIC values ranged from ?12.7 to ?2.7 ‰, controlled by biogeochemical processes in the catchment and within the stream; carbonate dissolution is the most important biogeochemical process affecting carbon isotopes in the upstream portions of the catchment, while carbonate dissolution and organic matter degradation control carbon isotope signatures downstream. Contributions of DIC from various biogeochemical processes were determined using steady state equations for different sampling seasons at the mouth of the Kamni?ka Bistrica River; results indicate that: (1) 1.9–2.2 % of DIC came from exchange with atmospheric CO₂, (2) 0–27.5 % of DIC came from degradation of organic matter, (3) 25.4–41.5 % of DIC came from dissolution of carbonates and (4) 33–85 % of DIC came from tributaries. δ¹⁵N values of nitrate ranged from ?5.2 ‰ at the headwater spring to 9.8 ‰ in the lower reaches. Higher δ¹⁵N values in the lower reaches of the river suggest anthropogenic pollution from agricultural activity. Based on seasonal and longitudinal changes of chemical and isotopic indicators of carbon and nitrogen in Kamni?ka Bistrica River, it can be concluded that seasonal changes are observed (higher concentrations are detected at low discharge conditions) and it turns from pristine alpine river to anthropogenic influenced river in central flow.     

Paleoecology and radiocarbon dating of the Pleistocene megafauna of the Brazilian Intertropical Region

During the Pleistocene a fauna composed of large (biomass > 44 kg) and giant mammals (biomass > 1000 kg) that are usually associated with open environments lived in the Brazilian Intertropical Region. We present here new information concerning the paleoecology and chronology of some species of this megafauna. Carbon isotope analyses were performed for a better understanding of the paleoecology of the species Eremotherium laurillardi (Lund, 1842), Notiomastodon platensis (Ameghino, 1888) and Toxodon platensis (Owen, 1849). The δ¹³C data allow attributing a generalist diet to these species, which varied according to the kind of habitat in which they lived. In more open habitats all species were grazers; in mixed habitats E. laurillardi and T. platensis were mixed feeders, and N. platensis was grazer; and in more closed habitats all species were mixed feeders.     

Characteristics of tropical cyclones making landfall on the Pacific coast of Mexico: 1970-2010

This study evaluates impacts from tropical cyclone (TC) landfalls on populated areas located along the Pacific Ocean coast of Mexico. The period of interest is from 1970 through 2010 and an international disaster database is used to identify the impact from the landfalling TCs. More than 30 landfall events occurred during the period; we examined the top 25 TCs based on rainfall accumulation, as well as the top 10 TC-related disasters based on the affected population. Each event resulted in affected population from 20 000 to more than 800 000. Strong winds and heavy rainfall, during periods of one to three days, are associated with property damage and loss of lives. Our results indicate that excessive rainfall accumulations and daily rates, over highly populated areas, are important elements associated with the occurrence of disasters. Six of the top 10 TC-related disasters occurred during El Niño and three during neutral conditions; however, looking at the top 25 events, 10 occurred during El Niño and 10 during neutral conditions. Three case studies that occurred during El Niño events (Liza in 1976, Pauline in 1997, and Lane in 2006) are documented in more detail as they affected areas with different population densities in the southern and northwestern coasts of Mexico.