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The combination of remote sensing and geophysical techniques is a practical approach for mapping environmental hydrogeological setting and delineating groundwater zones. This paper applies an integrated approach to identify and extract the subsurface structures that act as conduits for the groundwater flow in the highly deformed area of the Adamawa region. Remote sensing data through the lineament’s extraction technique highlights topographic lineaments along which rivers flow in the area. The distribution of these lineaments according to the lineament density map indicates the degree of permeability or porosity of each region and thus the capability in terms of groundwater potential. The filtering of aeromagnetic data enables to produce a structural map showing various geophysical lineaments interpreted as the fault systems of the study area. These faults are the main conduits through which magnetized rocks of granitoid type intruded into the basement and groundwater flows to the subsurface. Local application of the vertical electrical sounding (VES) shows that the study area is highly fractured/faulted and composed of multiple lithologic units including two aquifer layers (clayey sands and fractured schists) with thickness ranging from 5 to 15 m and from 34 to 82 m, respectively. Geoelectric cross-sections reveal that the subsurface structures consist of horsts, followed by a progressive subsidence depicted by the NE-trending faults towards the southern depression and grabens bounded by NW- and NE-trending normal faults. These prominent structures (faults, fractures, and grabens) are considered as the conduits for the groundwater flow into hard rock aquifers of the study area.

With the expansion of reserve cultivated land resources in coastal saline–alkali areas, the problem of soil salinization is becoming more and more prominent. In order to reveal the influence of different soil media and contact modes on soil water movement, a two-domain Hydrus-3D model was established to verify its performance in heterogeneous soil layers, and the characteristics of water, salt, and wet peak transport of surface soil and sandy soil under horizontal contact and inclined contact conditions were analyzed through experiments and simulations. The measured data show that in horizontal contact mode, probe 3 and probe 2 are close to the interface of the two layers of soil, and their maximum values are measured in about 60 min. The time difference between probe 1 and probe 2 is about 15 min. In the inclined contact mode, probe 4 in the topsoil reached 45% in 10 min and remained stable; the peak lag time of probes 3 and 2 was 10 min, and the peak lag time of probes 2 and 1 was 15 min; the water in the surface soil gradually increases and then stabilizes; and the water in the sand soil is similar to the normal curve. The salt characteristics in the surface soil are similar to the normal curve, while the salt characteristics in the sandy soil gradually increase and then stabilize. The simulation results show that the water content in the topsoil is more than 40%, and the maximum water content in the center of the sand is only 36.9%, which is roughly the same as the experimental results. The results showed that the Hydrus-3D model had a good simulation effect on the groundwater salt transport of heterogeneous soil under two contact methods. The RMSE value and E value are close to 0 and 1, respectively, indicating that the simulation has good feasibility and can be applied to the simulation of water and salt transport processes under different contact modes of soil media.

Abstract Background Although a substantial decline of Plasmodium falciparum infection is observed in Africa following implementation of new control strategies, malaria is still considered as the major cause of febrile illness in hospitalized African children. The present study was designed to assess the management of febrile illness and to determine the proportion of children with febrile illness hospitalized for primary diagnosis of malaria who had confirmed complicated malaria after implementation of new malaria control strategies in Libreville, Gabon. Methods Demographic, clinical and biological data from hospitalized children with fever or a history of fever, with a primary diagnosis of clinical malaria, aged less than 18 years old, who benefited from hematological measurements and microscopic malaria diagnosis, were recorded and analyzed during a prospective and observational study conducted in 2008 in the Centre Hospitalier de Libreville. Results A total of 418 febrile children were admitted at hospital as malaria cases. Majority of them (79.4%) were aged below five years. After medical examination, 168 were diagnosed and treated as clinical malaria and, among them, only 56.7% (n = 95) had Plasmodium falciparum positive blood smears. Age above five years, pallor, Blantyre Coma Score ≤2 and thrombocytopenia were predictive of malaria infection. Respiratory tract infections were the first leading cause of hospitalization (41.1%), followed by malaria (22.7%); co-morbidities were frequent (22%). Less than 5% of suspected bacterial infections were confirmed by culture. Global case fatality rate was 2.1% and 1% for malaria. Almost half (46%) of the children who received antimalarial therapy had negative blood smears. Likewise, antibiotics were frequently prescribed without bacteriological confirmation. Conclusions The use of clinical symptoms for the management of children febrile illness is frequent in Gabon. Information, training of health workers and strengthening of diagnosis tools are necessary to improve febrile children care.