Julia Pacheco Avila

Groundwater Quality: Analysis of Its Temporal and Spatial Variability in a Karst Aquifer

This study develops an approach based on hierarchical cluster analysis for investigating the spatial and temporal variation of water quality governing processes. The water quality data used in this study were collected in the karst aquifer of Yucatan, Mexico, the only source of drinking water for a population of nearly two million people. Hierarchical cluster analysis was applied to the quality data of all the sampling periods lumped together. This was motivated by the observation that, if water quality does not vary significantly in time, two samples from the same sampling site will belong to the same cluster. The resulting distribution maps of clusters and box-plots of the major chemical components reveal the spatial and temporal variability of groundwater quality. Principal component analysis was used to verify the results of cluster analysis and to derive the variables that explained most of the variation of the groundwater quality data. Results of this work increase the knowledge about how precipitation and human contamination impact groundwater quality in Yucatan. Spatial variability of groundwater quality in the study area is caused by: a) seawater intrusion and groundwater rich in sulfates at the west and in the coast, b) water rock interactions and the average annual precipitation at the middle and east zones respectively, and c) human contamination present in two localized zones. Changes in the amount and distribution of precipitation cause temporal variation by diluting groundwater in the aquifer. This approach allows to analyze the variation of groundwater quality controlling processes efficiently and simultaneously.

Análisis del ciclo del nitrógeno en el medio ambiente con relación al agua subterránea y su efecto en los seres vivos

In this article is shown the development of simulation programs for studying the techniques of noise filter in NMR (Nuclear Magnetic Resonance) signals, known as FID (Free induction decay). This signals are generated by exciting resonant nucleus with radio frequency pulses in an exterior magnetic field, presenting a complex exponential wave with gaussian noise. The computed programs may generate FID arameters signals definable by the user, add gaussian oise with a SNR determined.The signals with a low SNR may be treated by the traditional method of accumulations. Another considered alternative is the noise suppression through wavelets. This innovated technique promises to be quick and efficient. The created programs areused for the study and further development of these techniques, making more easy the results evaluation through the MonteCarlo method. The calculus is easier in different cases of the relation signal to noise residual in dB, establishing the difference signal without noise and with noise,also for the filtered method using accumulations so WT and WPT. From these programs and the associated methodology the investigations of better filtration variables for noise suppression in the FID signals is easier.

Fuentes principales de nitrógeno de nitratos en aguas subterráneas

En este articulo se muestra commo usar el modem del computador para enviar archivos por la linea telefonica pero sin interrumpir la conversacion.

Environmental Study on Cadmium in Groundwater in Yucatan

The geology of Yucatan is karstic, with many caves and sinkholes, deciduous vegetation, and a slight topographical slope in the landscape. The only water source consists of a fragile system of aquifers which consist of a freshwater layer floating over saline water. This freshwater layer is very susceptible to human disturbances. Since this is the sole water source in the state of Yucatan, it is important to know it and to monitor its quality.