Rice is a major exposure route for arsenic in Chakdaha block,Nadia district,West Bengal,India: A probabilistic risk assessment

The importance or otherwise of rice as an exposure pathway for As ingestion by people living in Bengal and other areas impacted by hazardous As-bearing groundwaters is currently a matter of some debate. Here this issue is addressed by determining the overall increased cancer risk due to ingestion of rice in an As-impacted district of West Bengal. Human target cancer health risks have been estimated through the intake of As-bearing rice by using combined field, laboratory and computational methods. Monte Carlo simulations were run following fitting of model probability curves to measured distributions of (i) As concentration in rice and drinking water and (ii) inorganic As content of rice and fitting distributions to published data on (i) ingestion rates and (ii) body weight and point estimates on bioconcentration factors, exposure duration and other input variables. The distribution of As in drinking water was found to be substantially lower than that reported by previous authors for As in tube wells in the same area, indicating that the use of tube well water as a proxy for drinking water is likely to result in human health risks being somewhat overestimated. The calculated median increased lifetime cancer risk due to cooked rice intake was 7.62 × 10⁻⁴, higher than the 10⁻⁴–10⁻⁶ range typically used by the USEPA as a threshold to guide determination of regulatory values and similar to the equivalent risk from water intake. The median total risk from combined rice and water intake was 1.48 × 10⁻³. The contributions to this median risk from drinking water, rice and cooking of rice were found to be 48%, 44% and 8%, respectively. Thus, rice is a major potential source of As exposure in the As-affected study areas in West Bengal and the most important exposure pathway for groups exposed to low or no As in drinking water.     

Radon transfer from groundwater used in showers to indoor air

Estimation of Rn transfer from water to indoor air based on multi-day measurements may underestimate alpha exposure that occurs at short time scales in confined spaces, such as from showering, in houses with high Rn activities in the water supply. In order to examine one such incremental increase in exposure, variations in Rn in water and indoor air in 18 houses with private wells in western North Carolina (USA) were investigated. Radon in well water ranged from 158 to 811 Bq L⁻¹ (median 239 Bq L⁻¹). After 20-min showers in bathrooms with closed doors, peak Rn in air increases (above background) ranged from 71 to 4420 Bq m⁻³ (median 1170 Bq m⁻³). Calculated transfer coefficients at the scale of a 40-min closed bathroom (20-min shower plus 20 min post-shower) are described by a lognormal distribution whose geometric mean exceeds the widely-used ∼10⁻⁴ whole-house transfer coefficient by about one order of magnitude. As short-lived decay products grow from shower-derived Rn, short-term alpha energy exposure occurs in bathrooms in addition to the exposure caused by Rn mixed throughout the volume of the house. Due to the increasing ratio of Rn decay products to Rn, alpha energy exposure is greatest several minutes after the shower is turned off. For a 7.2-min shower with 10 min of additional exposure before opening the door, a geometric mean 5.6% increase in exposure over the ∼10⁻⁴ whole-house transfer coefficient derived from longer measurement periods was estimated. In addition to Rn activity in water, short-term shower exposure to Rn progeny depends on exposure time, ventilation, attachment and deposition, among other variable factors that characterize individual houses and residents.     

Coupled hydrogeological and reactive transport modelling of the Simpevarp area (Sweden)

The Simpevarp area is one of the alternative sites being considered for the deep geological disposal of high level radioactive waste in Sweden. In this paper, a coupled regional groundwater flow and reactive solute transport model of the Simpevarp area is presented that integrates current hydrogeological and hydrochemical data of the area. The model simulates the current hydrochemical pattern of the groundwater system in the area. To that aim, a conceptual hydrochemical model was developed in order to represent the dominant chemical processes. Groundwater flow conditions were reproduced by taking into account fluid-density-dependent groundwater flow and regional hydrogeologic boundary conditions. Reactive solute transport calculations were performed on the basis of the velocity field so obtained. The model was calibrated and sensitivity analyses were carried out in order to investigate the effects of heterogeneities of hydraulic conductivity in the subsurface medium. Results provided by the reactive transport model are in good agreement with much of the measured hydrochemical data. This paper emphasizes the appropriateness of the use of reactive solute transport models when water-rock interaction reactions are involved, and demonstrates what powerful tools they are for the interpretation of hydrogeological and hydrochemical data from site geological repository characterization programs, by providing a qualitative framework for data analysis and testing of conceptual assumptions in a process-oriented approach.     

An operational multiscale system for hazards prediction, mapping, and response

By definition, a crisis is a situation that requires assistance to be managed. Hence, response to a crisis involves the merging of local and non-local emergency response personnel. In this situation, it is critical that each participant: (1) know the roles and responsibilities of each of the other participants; (2) know the capabilities of each of the participants; and (3) have a common basis for action. For many types of natural disasters, this entails having a common operational picture of the unfolding events, including detailed information on the weather, both current and forecasted, that may impact on either the emergency itself or on response activities. The Consequences Assessment Tool Set (CATS) is a comprehensive package of hazard prediction models and casualty and damage assessment tools that provides a linkage between a modeled or observed effect and the attendant consequences for populations, infrastructure, and resources, and, hence, provides the common operational picture for emergency response. The Operational Multiscale Environment model with Grid Adaptivity (OMEGA) is an atmospheric simulation system that links the latest methods in computational fluid dynamics and high-resolution gridding technologies with numerical weather prediction to provide specific weather analysis and forecast capability that can be merged into the geographic information system framework of CATS. This paper documents the problem of emergency response as an end-to-end system and presents the integrated CATS–OMEGA system as a prototype of such a system that has been used successfully in a number of different situations.     

Flood hazard delineation combining geomorphological and hydrological methods: an example in the Northern Iberian Peninsula

Flood mapping requires the combination and integration of geomorphological and hydrological-hydraulic methods; however, despite this, there is very little scientific literature that compares and validates both methods. Two types of analysis are addressed in the present article. On the one hand, maps of flood plains have been elaborated using geomorphological evidence and historical flood data in the mountainous area of northwestern Spain, covering an area of more then 232 km² of floodplains. On the other hand, a hydrometeorological model has been developed (Clark semidistributed unit hydrograph) in the Sarria River basin (155 km², NW Spain). This basin is not gauged, hence the model was subjected to a goodness-of-fit test of its parameter (curve number) by means of Monte Carlo simulation. The peak flows obtained by means of the hydrological model were used for hydraulic modeling (one-phase, one-dimensional and steady flow) in a 4 km² urban stretch of the river bed. The delineation of surface areas affected by floods since 1918, as well as those analyzed subsequent to the geomorphological study, reveals a high degree of reliability in the delineation of the flooded areas with frequent recurrence intervals (<50 years). If we compare these flooded surface areas with the estimate obtained by the hydrological-hydraulic method we can see that the latter method overestimates the extent of the surface water by 144% for very frequent recurrence intervals (>10 years) and underestimates it as the recurrence interval increases, by up to 80% less floodplain for exceptional events (>500 years). Finally, a management map is put forth combining the most reliable results available by integrating both methods. Originally presented at the Sixth International Conference on Geomorphology.     

Reducing hazard vulnerability through local government engagement and action

The concept of a natural hazard is a human construct. It is the interaction with human communities and settlements that defines a natural phenomenon as a natural hazard. Thus the end point of hazard mitigation and hazard vulnerability assessment must involve an attempt to reduce, or mitigate, the impact of the natural hazard on human communities. The responsibility to mitigate hazard impact falls primarily upon governments and closely connected non-government and private institutional agencies. In particular, it is most often local government that takes the responsibility for safeguarding its own communities, infrastructure and people. Hazard vulnerability of specific local communities is best assessed by the local government or council, which then faces the responsibility to translate that assessment into community education and infrastructural safeguards for hazard mitigation. This paper illustrates the process of local government engagement in hazard mitigation in Australia, through the Natural Disaster Risk Management Studies, as a first step towards natural disaster reduction.     

Mineralogy and geochemistry of El Dorado epithermal gold deposit, El Sauce district, central-northern Chile

Summary The El Dorado Au-Cu deposit is located in an extensive intra-caldera zone of hydrothermal alteration affecting Upper Cretaceous andesites of the Los Elquinos Formation at La Serena (≈ 29°47′S Lat., 70°43′W Long., Chile). Quartz-sulfide veins of economic potential are hosted by N25W and N20E fault structures associated with quartz-illite alteration (+supergene kaolinite). The main ore minerals in the deposit are pyrite, chalcopyrite ± fahlore (As/(As + Sb): 0.06−0.98), with electrum, sphalerite, galena, bournonite-seligmanite (As/(As + Sb): 0.21−0.31), marcasite, pyrrhotite being accessory phases. Electrum, with an Ag content between 32 and 37 at.%, occurs interstitial to pyrite aggregates or along pyrite fractures. Pyrite commonly exhibits chemical zonation with some zones up to 1.96 at.% As. Electron probe microanalyses of pyrite indicate that As-rich zones do not exhibit detectable Au values. Fluid inclusion microthermometry shows homogenization temperatures between 130 and 352 °C and salinities between 1.6 and 6.9 wt.% NaCl eq. Isotope data for quartz, ankerite and phyllosilicates and estimated temperatures show that δ¹⁸O and δD for the hydrothermal fluids were between 3 and 10‰ and between −95 and −75‰, respectively. These results suggest the mineralizing fluids were a mixture of meteoric and magmatic waters. An epithermal intermediate-sulfidation model is proposed for the formation of the El Dorado deposit. Author’s present address: J. Carrillo-Rosúa, Dpto. de Didáctica de las Ciencias Experimentales, Universidad de Granada, Campus de Cartuja, 18071, Granada, Spain     

Methodology of hydrogeological characterization of deep carbonate aquifers as potential reservoirs of groundwater. Case of study: the Jurassic aquifer of <Emphasis Type="Italic">El Maestrazgo</Emphasis> (Castellón,Spain)

A methodology for the characterization of deep carbonate aquifers has been developed and applied to El Maestrazgo Jurassic aquifer in Castellón, Spain. Characterization of these aquifer formations, located at more than 300 m deep, consisted of a previous phase of compilation, analysis and synthesis of the existing information about the area, followed by a coordinated combination of different speciality studies: geology, stratigraphy, structural analysis, hydrogeology, hydrochemistry, geophysics and remote sensing. Geological studies included geological mapping, definition of stratigraphical units and facies and structural analysis. The aim of the hydrogeology study was to define aquifer formations, recharge area, aquifer points inventory and groundwater flow directions for the establishment of piezometric and water quality observation nets. Special techniques were applied, like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium isotopes. Hydrochemical techniques, including majority elements characterization and stable isotopes (¹⁸O, ²H and ³H) determination, allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system. Geophysics was useful in determining the aquifer geometry, the features of the basement and the petrophysical characteristics of the geological formations. Preliminary results show an important tectonic complexity and the possibilities for groundwater uses in the area of study.     

Field Measurement of Suction, Water Content, and Water Permeability

This paper presents a review of techniques for field measurement of suction, water content, and water hydraulic conductivity (permeability). Main problems in the use of field tensiometers are addressed and hints on how to improve tensiometer performance are given. Advantages and limitations of instruments for indirect measurement of suction including electrical conductivity sensors, thermal conductivity sensors, dielectric permittivity sensors, filter paper, and psychrometer are discussed. Techniques for water content measurement based on dielectric methods are then presented. These include time and amplitude domain reflectometry and capacitance. Finally, a brief overview of methods for measurement of water permeability in the field is presented.