Cooling history of nested plutons from the Variscan Tichka plutonic complex (Morocco)

International Journal of Earth Sciences - Four imbricated mafic to felsic plutons of Variscan age from Morocco have been investigated for their cooling history and geochemical interactions with...     

Environmental fragility framework for water supply systems: a case study in the Paulista Macro Metropolis area (SE Brazil)

Water resources availability is increasingly constrained, considering the quality and quantity available for use. There is an urgent need of recovering this availability, focusing on the planning and management process of water supply systems. One of the main threats to water resources is related to erosion effects, namely widespread pollution load and the silting of watercourses and reservoirs useful life reduction. The objective of this study was to evaluate water supply systems environmental fragility within the Paulista Macro Metropolis area and to use the results to develop environmental zone classes to orient territorial planning. The study was conducted in seven superficial water supply systems of the aforementioned region. Environmental fragility evaluation was focused on four environmental variables that represent natural vulnerability to erosion, and 2015 land cover map to delineate human influence on erosive processes. Results indicate that Tietê River water supply systems, namely Piracicaba, Capivari and Jundiaí (PCJ) and Itupararanga systems, can be considered the most fragile water supply systems in the study area. The environmental fragility map was used to derive the environmental zoning map, including conservation and priority areas, suitable regions for agriculture expansion, and areas with high needs for restoration efforts. In addition, environmental fragility framework herein can be viewed as a model with high replication potential for regional planning and management in that land cover can be manipulated to minimize environment natural vulnerability, guiding territorial occupation toward a more sustainable landscape design, which subsidizes water resources multiple uses.     

Flow‐Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations

This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow‐through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream‐aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow‐through streams.     

Determinants of sediment properties and organic matter in beach and dune environments based on boosted regression trees

Grain size properties and the variation of organic matter in coastal beach and dune environments are assumed to be controlled by the intensity of aeolian processes, time and the sediment source. However, assumptions are based on relatively limited empirical studies. In this study, we examined which environmental variables are the main predictors of multiple topsoil properties. To achieve this, we analysed an extensive dataset systematically collected across all beach zones and a large geographical area at the Finnish Baltic Sea coast characterized by post‐glacial land uplift. We included a comprehensive set of predictors in the analysis and applied boosted regression trees, a modern modelling technique particularly suited for analysis without prior assumptions of the data model. The results suggest that mean grain size and sorting are mainly determined by northing and fetch. Northing, disturbance and fetch predicted the variation of soil organic matter while litter cover was strongly related to disturbance. Based on the analyses, we were able to identify the main drivers of multiple topsoil properties on land uplift beaches. Parent material is suggested to determine sediment textural properties, which largely masks the effects of transient processes. Mean grain size and sorting are highly interdependent: grains become finer and sorting improves with increasing shore exposure. The intensity of momentary geomorphic processes controls the accumulation of litter whereas the slower accumulation of organic matter in the soil is influenced also by the static exposure setting. Skewness and kurtosis of the grain size distribution are mainly influenced by unmeasured processes, potentially relating to the geomorphological origin of the sediment. Copyright © 2014 John Wiley & Sons, Ltd.