Chemical weathering of the volcanic soils of Isla Santa Cruz (Galápagos Islands, Ecuador)

We present a study on weathering of volcanic soils using 43 profiles (131 horizons) sampled in Santa Cruz Island (Galapagos Islands). Several weathering indices, based on chemical composition, are used. Since the geological material is highly homogeneous the intensity of weathering is mostly related to climatic conditions controlled by topography. There is a gradient of increasing weathering from the arid conditions predominant in the coast to elevations of 400-500 m a.s.l. where much more humid conditions prevail

Improving the Understanding of N Transport in a Rural Catchment Under Atlantic Climate Conditions From the Analysis of the Concentration–Discharge Relationship Derived From a High-Frequency Data Set

[Abstract] Understanding processes controlling stream nutrient dynamics over time is crucial for implementing effective management strategies to prevent water quality degradation. In this respect, the study of the nutrient concentration–discharge (C–Q) relationship during individual runoff events can be a valuable tool for extrapolating the hydrochemical processes controlling nutrient fluxes in streams. This study investigated nitrogen concentration dynamics during events by analyzing and interpreting the nitrogen C–Q relationship in a small Atlantic (NW Iberian Peninsula) rural catchment. To this end, nitrate (NO3-N) and total Kjeldahl nitrogen (TKN) concentrations were monitored at a high temporal resolution during 102 runoff events over a 6-year period. For each of the selected runoff events, C–Q response was examined visually for the presence and direction of hysteresis loops and classified into three types of responses, namely clockwise, counterclockwise, and no hysteresis. Changes in concentration (ΔC) and the hysteresis direction (ΔR) were used to quantify nitrogen ( and TKN) patterns during the runoff events. The transport mechanisms varied between compounds. The most frequent hysteretic response for was counterclockwise with enrichment. On the contrary, the main TKN dynamic was enrichment with clockwise hysteresis. Event characteristics, such as rainfall amount, peak discharge (i.e., maximum discharge of the runoff event), and event magnitude relative to the initial baseflow (i.e., the difference between the maximum discharge of the runoff event and the initial baseflow divided by initial baseflow) provided a better explanation for hysteresis direction and magnitude for TKN than antecedent conditions (antecedent precipitation and baseflow at the beginning of the event). For hysteresis, the role of hydrometeorological conditions was more complex. The hysteresis magnitude was related to the magnitude of the event relative to the initial baseflow and the time elapsed since a preceding runoff event. These findings could be used as a reference for the development of N mitigation strategy in the region.This research has been supported by the Spanish Ministry of Education and Science (grant no. REN2003-08143) and Xunta of Galicia (grant nos. PGIDIT05RAG10303PR and 10MDS103031PR)Xunta of Galicia; PGIDIT05RAG10303PRXunta of Galicia; 10MDS103031P

Characteristics principals of soils of Holguín province (Cuba). Use and soils management

[Abstract] In this paper was performed an compilation of the main characteristic and degradation processes of soils Holguín province (Cuba) in order to stablish a proposal management leading to soil preservation. The main soils in the zone are of four types. According to the cuban classification system the major soils are Fersialitics, Vertisoils, Bruns and Ferritic, which are respectively equivalent to the Luvisols, Vertisols, Cambisols and Ferralsols of the FAO system (1998). About 70% of the agricultural soils of the Holguín province are affected by different erosion degree. About 17% of soils are affected by salinity and are associated mainly to the group of Vertisoils, that in the greater part are dedicated to the sugarcane cultivated and at grassland. Together with the erosion and salinity procceses others limiting factors of the soils are the sodicity, contents of gravels and stones, efective deepth, carbonates content and relief

Micromorfological and mineralogical transformations in the weathering process of the Viveiro and Traba Granodiorites

[Resumen] Se realiza el estudio de dos perfiles de meteorizaci6n sobre granodioritas en Galicia (NW de España). El grado de drenaje condiciona la evolución de los feldespatos: en la saprolita de grano más grueso, con grandes fisuras, se transforman en gibbsita, en la de grano más fino este mineral aparece en las primeras etapas pero el producto final es halloysita. Las micas evolucionan en ambos casos hacia vermiculitas hidroxialumínicas.[Abstract] Two weathering profiles developed from granodiorites in Galicia (NW of Spain) are studied. The drainage degree determines the feldspars evolution. In the coarse grain saprolite, with great fissures, feldspars are transformed into gibbsite, while in the finer grain saprolite, the weathering product is halloysite. Micas change gradually to hidroxy-Al-interlayered vermiculite

Phyllosilicate crystallinity in soils and weathering products from granitic rocks of Galicia

[Resumen] Se ha determinado la cristalinidad de micas y filosilicatos 1: 1 dioctaédricos de los limos y arcillas de 20 perfiles edáficos desarrollados sobre rocas graníticas. Se observa una estrecha relación entre el valor del índice de cristalinidad de los filosilicatos 2: 1, el tipo de mica predominante en el material de partida y el grado de desarrollo de los suelos; la menor cristalinidad aparece asociada a suelos formados a partir de materiales en los que la biotita es la única mica presente o la predominante. Los estudios de D. R. X., A. T. D. e 1. R. coinciden en señalar el predominio de filosicitatos 1: 1 de muy débil organización interna, comprobándose por microscopía electrónica que son fundamentalmente de tipo halloysítico[Abstract] Micas and dioctaedric 1: 1 phyllosilicate crystallinity of loam and clay fractions of twenty soil profiles developed from granite rocks have been determined. There are a clear relation among the cystallinity index of 2: 1 phyllosilicate, the prevailing type of mica in the soil-parent material and the soil evolution degree. Cystallinity is the lowest when soils are formed from granitic material when the most abundant mica is the biotite. XRD, DTA and RI studies indicate the predominance of very low ordered 1: 1 phyllosilicates, electron microscopy shows that they are mainly halloysitic anes

Granite paleoweathering: A case-study under the tertiary deposit of Xinzo de Limia

[Resumen] Se estudia una paleoalteración desarrollada sobre granito y situada bajo un espesor de 120 m. de sedimentos en la cuenca terciaria de Xinzo de Limia (Ourense). El cambio minera16gico más significativo es la transformaci6n de las plagioclasas en caolinita. Se detectan también pequeñas proporciones de esmectitas. El estudio geoquímico revela una clara lixiviaci6n de bases, como lo pone de manifiesto la disminución de todos los índices de alteración (Indices de Parker, Reiche y pH de abrasi6n). El proceso de meteorización dominante es la monosialitización, con una cierta tendencia bisialítica en las primeras fases de la alteración.[Abstract] A granite paleoweathering located under 120 m of tertiary sediments at Xinzo de Limia (Galicia, NW Spain) is studied. The transformation ofplagioclase in kaolinite is the most important mineralogical change ocurred during the process. Minor proportions of smectite- are detected too. The geochemistry study reveales an evident lixiviation of bases, so the different weathering rates decrease as the process progresses (Parker and Reiche indexes and abrasion-pH). The dominant process of weathering is the monosialitization (PEDRO, 1979) although the first phases show a bisialitic trend

Estimation of the mechanical properties of the eye through the study of its vibrational modes

Measuring the eye's mechanical properties in vivo and with minimally invasive techniques can be the key for individualized solutions to a number of eye pathologies. The development of such techniques largely relies on a computational modelling of the eyeball and, it optimally requires the synergic interplay between experimentation and numerical simulation. In Astrophysics and Geophysics the remote measurement of structural properties of the systems of their realm is performed on the basis of (helio-)seismic techniques. As a biomechanical system, the eyeball possesses normal vibrational modes encompassing rich information about its structure and mechanical properties. However, the integral analysis of the eyeball vibrational modes has not been performed yet. Here we develop a new finite difference method to compute both the spheroidal and, specially, the toroidal eigenfrequencies of the human eye. Using this numerical model, we show that the vibrational eigenfrequencies of the human eye fall in the interval 100 Hz - 10 MHz. We find that compressible vibrational modes may release a trace on high frequency changes of the intraocular pressure, while incompressible normal modes could be registered analyzing the scattering pattern that the motions of the vitreous humour leave on the retina. Existing contact lenses with embebed devices operating at high sampling frequency could be used to register the microfluctuations of the eyeball shape we obtain. We advance that an inverse problem to obtain the mechanical properties of a given eye (e.g., Young's modulus, Poisson ratio) measuring its normal frequencies is doable. These measurements can be done using non-invasive techniques, opening very interesting perspectives to estimate the mechanical properties of eyes in vivo. Future research might relate various ocular pathologies with anomalies in measured vibrational frequencies of the eye.Comment: Published in PLoS ONE as Open Access Research Article. 17 pages, 5 color figure

A Wireless Sensor Network (WSN)–Based Water Quality Monitoring for the Characterization of Fishing Grounds Near the Mining Areas of Tubay, Agusan Del Norte, Philippines

Water quality has an impact on the fishing and aquaculture industry of a community. Tubay Bay is one of the main sources of coastal products of nearby cities like Butuan and Cabadbaran and also serves as the navigation routes of hauling ships of mining companies. Of the Water Quality Index (WQI), the Environmental Management Bureau (EMB) water quality data shows that the pH levels exceeded the limit. This paper presents the initial outputs in the development of a low-cost wireless sensor network (WSN) system using open-source hardware platforms to monitor the pH of the water bodies at Tubay, Agusan del Norte, Philippines. The proposed system is devised to be highly scalable in terms of the type of sensors, the number of sensor nodes, and the technology applied for each node. This is well suited for a wider coverage of monitoring the WQIs of Tubay Bay. Results of this study showed a good transmission performance of real-time water quality data in any areas where GSM signal is present. The established platform and database of this study could provide valuable information that could support or contradict claims by the local government units (LGUs) on the effects of mining activities to the agro-fishing activities in the area and provide insights on which water quality parameters or water condition that are highly correlated to pH must be closely monitored. This demonstrates the use of WSN in establishing a low cost but effective monitoring tool that can be replicated in other areas that need extensive monitoring

Weathering in granite and lamprophyre contact

[Resumen] Se realiza el estudio microestructural, mineralógico y geoquímico del proceso de meteorización en una zona de contacto granito-lamprófido. En la roca granítica se observa gibbsita, en los medios muy lixiviados, y filosilicatos 1: 1 en los menos drenados. En ellamprófido los productos son filosilicatos 1: 1, integrados vermiculíticos y oxi-hidróxidos de hierro; la abundancia de estos óxidos permite la conservación de la estructura original hasta etapas muy avanzadas dé la meteorización. El proceso global es de tipo monosialítico (fermonosialítico en las rocas básicas) con una tendencia inicial alitizante en las rocas graníticas. El pH de abrasión constituye un buen índice del grado de meteorización de estas rocas.[Abstract] In this paper is developed a microstructural, mineralogical and geochemical study of the weathering process in a contact between a granitic rock and a lamprophyre. In the granitic rack the main weathering products are gibbsite, under strongly leaching conditions, and 1: 1 phyllosilicates when the drainage is lesser. In the lamprophyre the products are 1: 1 phyllosilicates, vermiculitic integrades and iron oxides; the abundance of this oxides permit the conservation of rock structure till advanced stages of weathering. The overall process is moniosiallitic (fermonosiallitic in the basic rock), although an allitic tendency can be appreciated during the initial stages of the granitic rock weathering. The abrasion pH is good index to asses the weathering degree of these rocks

Abrasion pH use as an index ofweathering and pedogenesis degree in granitic soils of A Coruña (Spain).

[Resumen] En este trabajo se determina el pH de abrasión de las fracciones arenosas de un conjunto de perfiles de alteración y suelos desarrollados sobre rocas graníticas de la provincia de A Coruña (Galicia, NW de España). Se observa que tanto estos valores como el del pH de ·abrasión de la muestra total, sin materia orgánica, constituyen un buen índice del grado de evolución del material, presentando la ventaja, sobre otros índices, de su fácil y rápida determinación, por lo que parece un dato a tener en cuenta especialmente en los estudios a gran escala de cartografía y usos potenciales del suelo.[Abstract] In this paper were studied the abrasion pH in samples of several soils and veathering profiles developped on granitic rocks in A Coruña (Galicia, NW Spain). The abrasion pH values of sands and of the whole sample (organic matter free) are a good index to assess the evolution degree of the materials. This index is an esay and no time consuming test; so its use can be considered in large scale cartographic works and in studies on potential soil fertility