Toward real-time three-dimensional mapping of surficial aquifers using a hybrid modeling approach

A hybrid modeling approach is proposed for near real-time three-dimensional (3D) mapping of surficial aquifers. First, airborne frequency-domain electromagnetic (FDEM) measurements are numerically inverted to obtain subsurface resistivities. Second, a machine-learning (ML) algorithm is trained using the FDEM measurements and inverted resistivity profiles, and borehole geophysical and hydrogeologic data. Third, the trained ML algorithm is used together with independent FDEM measurements to map the spatial distribution of the aquifer system. Efficacy of the hybrid approach is demonstrated for mapping a heterogeneous surficial aquifer and confining unit in northwestern Nebraska, USA. For this case, independent performance testing reveals that aquifer mapping is unbiased with a strong correlation (0.94) among numerically inverted and ML-estimated binary (clay-silt or sand-gravel) layer resistivities (5–20 ohm-m or 21–5,000 ohm-m), and an intermediate correlation (0.74) for heterogeneous (clay, silt, sand, gravel) layer resistivities (5–5,000 ohm-m). Reduced correlation for the heterogeneous model is attributed to over-estimating the under-sampled high-resistivity gravels (about 0.5 % of the training data), and when removed the correlation increases (0.87). Independent analysis of the numerically inverted and ML-estimated resistivities finds that the hybrid procedure preserves both univariate and spatial statistics for each layer. Following training, the algorithms can map 3D surficial aquifers as fast as leveled FDEM measurements are presented to the ML network.     

Long‐term demographic and reproductive trends in Ciona intestinalis sp. A

Ciona intestinalis sp. A (Tunicata, Ascidiacea) is a marine invertebrate with a widespread distribution and high invasive potential, yet little is known about its ecology. Here, the macrodynamics of demographic and reproductive trends were first determined using archive data covering 2002–2012. Species abundance in the central Tyrrhenian Sea (Campania, Italy ‐ NW Mediterranean) displayed Poisson distribution across 2002–2008, massive die‐off in 2009/2010 and population recovery in 2011/2012. We defined the seasonal ranges of sea surface temperature in which sampling size, animal size and reproductive status reached their highest values. In 2003/2004, self and non‐self fertilization appeared to follow reverse trends across the year. The long‐term recording run here on Ciona intestinalis sp. A provides novel insights into its population biology and ecology, and represents a valuable tool for sampling management and research planning.     

Weathering processes affecting granitoid profiles of Capo Vaticano (Calabria,southern Italy) based on petrographic,mineralogic and reaction path modelling approaches

This work focuses on developing multidisciplinary research on weathering profiles of granitoid rocks related to the tectonic and landscape evolution of the Capo Vaticano area, Calabria, southern Italy. During the Pleistocene, the Mediterranean climate plays, on the already decomposed plutonic rocks, important processes of alteration, on both the highest and inland areas and the coastal areas of the Calabrian region, such as the studied area. Field observations coupled to chemical, minero‐petrographical features and geochemical modelling are used to characterize the weathering processes affecting the granitoid complex. The granitoid cut slopes show a generally simple weathering profile characterized by a progressive increase in weathering towards the top of the slopes. The completely weathered rocks (class V) and residual soil (class VI) contain a high percentage of altered minerals, microfractures, and voids. The main mineralogical changes are the partial transformation of biotite and the partial destruction of feldspars (mainly plagioclase) that are associated with the neoformation of secondary clay minerals and ferruginous products during the most advanced stage of weathering. These transformations produce a substitution of the original rock fabric. Geochemical modelling showing the precipitation of kaolinite, illite, vermiculite, ferrihydrite and calcite. These secondary solid phases are similar to those found in this natural system. Thus, the final results of the weathering process is a soil‐like material mainly characterized by mostly a sand to gravel grain‐size fractions related to microfabric changes and mineralogical and chemical variations. Copyright © 2014 John Wiley & Sons, Ltd.