Arsenic distribution, concentration and speciation in groundwater of the Osijek area, eastern Croatia

Groundwater is the main source of drinking water for the population of nearly 200,000 people in eastern Croatia. The largest town in the region is Osijek whose citizens are supplied with drinking water obtained from groundwater from the “Vinogradi” well field. This study investigated and determined As occurrence in groundwater of the Osijek area. Groundwater samples were taken from 18 water wells and 12 piezometers with a depth ranging between 21 and 200 m. Over the 10-a period to 2007, a mean As concentration of 240 μg L⁻¹ was found. There was no statistically significant secular change in concentration over that period, however small but significant seasonal variations were noted, with the highest seasonal As concentrations over the period May 2006-February 2007 being observed in summer. The predominant As species observed was As(III), constituting 85% and 93% of total As in piezometers and water wells, respectively. Higher concentrations of As tended to be found in deeper wells with the mean As concentration in shallow groundwater (<50 m) and deep groundwater (>50 m) being 27 μg L⁻¹, and 205 μg L⁻¹, respectively. Geochemically, the groundwaters show similarities to those in other parts of the Pannonian Basin. Arsenic(tot) is weakly correlated with pH and Fe, negatively correlated with Mn and has no significant correlation with any of EC, COD-Mn or alkalinity.     

DETERMINATION OF TWELVE TRACE ELEMENTS IN TWENTY-SEVEN AND TEN MAJOR ELEMENTS IN TWENTY-THREE GEOCHEMICAL REFERENCE SAMPLES BY X-RAY FLUORESCENCE SPECTROMETRY

This study reports the results of twelve trace elements in twenty-seven International geochemical reference samples (IGRS) (15 from Japan, 7 from South Africa, 4 from France and 1 from U.S.A.). Similarly, ten major elements were also determined in twenty-three GRS (15 from Japan, 5 from South Africa, 2 from France and 1 from U.S.A.). Whenever possible, the results are compared with literature values for these GRS.     

Nanochemo-mechanical signature of organic-rich shales: a coupled indentation–EDX analysis

The organic–inorganic nature of organic-rich source rocks poses several challenges for the development of functional relations that link mechanical properties with geochemical composition. With this focus in mind, we herein propose a method that enables chemo-mechanical characterization of this highly heterogeneous source rock at the micron and submicron length scale through a statistical analysis of a large array of energy-dispersive X-ray spectroscopy (EDX) data coupled with nanoindentation data. The ability to include elemental composition to the indentation probe via EDX is shown to provide a means to identify pure material phases, mixture phases, and interfaces between different phases. Employed over a large array, the statistical clustering of this set of chemo-mechanical data provides access to the properties of the fundamental building blocks of clay-dominated organic-rich source rocks. The versatility of the approach is illustrated through the application to a large number of source rocks of different origin, chemical composition, and organic content. We find that the identified properties exhibit a unique scaling relation between stiffness and hardness. This suggests that organic-rich shale properties can be reduced to their elementary constituents, with several implications for the development of predictive functional relations between chemical composition and mechanical properties of organic-rich source rocks such as the intimate interplay between clay-packing, organic maturity, and mechanical properties of porous clay/organic phase.     

Potential distribution of a montane rodent(Cricetidae,Handleyomys chapmani) through time in Mexico: the importance of occurrence data

Ecological Niche Modeling uses the geographic coordinates of species presence records as the primary input to estimate potential geographic distributions. It is little known whether carrying out rigorous data pre-processing is necessary before building niche models to be transferred to different time period. Here we compared the current, past, and future potential distributions projected by niche models built from two different databases, an openaccess database and a database compiled ad hoc, for Handleyomys chapmani, a rodent closely associated with montane cloud forests in Mexico. The models predicted different spatial patterns of climatic suitability for the three periods examined. Based on our current knowledge of cloud forest species in Mexico, the distributions predicted by the model built from the ad hoc database are more ecologically realistic than those obtained from the open-access database. The models built using the open-access database were particularly inaccurate at the limits of the geographic range, predicting larger, more diffuse distributions for the three periods. We conclude that pre-processing occurrence data is crucial for mountain species, as the number of localities and even minor inaccuracies in the geographic coordinates can translate into very different climatic conditions due to abrupt altitudinal changes. Finally, the predicted shifts in the potential distribution of H. chapmani over time indicate that this species is highly susceptible to climate change.