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The Taxco mining district is a well-known international producer of silver, jewelry, and precious metal handicrafts. Inappropriate disposal wastes from anthropogenic activities have been deteriorating the hydric resources and threatening the inhabitants’ health, since they use the springwater for human consumption and domestic activities. A multi-tracer approach combining measurements of hydrochemical data, trace elements, and isotopes δ2H, δ18O, 3H, and 87Sr/86Sr ratios was undertaken for 18 springwater samples. δ18O and δ2H indicate that the springwater comes from the rain and had experienced some degree of isotopic fractionation by atmospheric evaporation in some samples at lower altitudes. 3H values on the springwater showed the existence of old and new water. Three groups of springwater were identified according to age: local flow in rhyolites, intermediate flow through red beds to the outcrop point in sandstone and shales, and deep flow in greenschist. The results of this study show the utility of 87Sr/86Sr ratios in identifying the water–rock interactions and springwater flow paths, suggesting that more widespread use of the strontium isotopic fingerprint is warranted.

The San Juan-Taxco River system is situated in the Taxco mining district, which is a well-known international producer of silver, jewelry and precious metal handicrafts. The population and biota in the area have been affected by inappropriate disposal of anthropogenic activities that pollute the hydric resources and threaten their health and sustainability, since the inhabitants use the groundwater and river water for human consumption, domestic water supply and irrigation. This study was conducted to assess the pollution in the river system, human health implications and ecological risk in the aquatic environment (groundwater, surface water and superficial sediment). This evaluation was done on the base of hydrochemical, textural, mineralogical and geochemical analysis supported by calculation of human health risk using chronic daily intake (CDI), hazard quotient (HQ) and hazard index (HI) with environmental and geochemical indices for ecological risk evaluation. The health risk assessment indicated increasing non-health carcinogenic risk to the exposed population to the river water and dug wells (HI > 1), and thus, these resources are not recommended for human consumption, domestic activities and prolonged ingestion. The results demonstrated a high degree of pollution due to toxic elements and geochemical indices. The Pollution Load Index indicated potential risk that will cause harmful biological effects in the riverine environment.

The hydrological system of San Juan-Taxco Rivers in located inside of one of the oldest and major mining district in Mexico. Several communities in the area use the rivers water along its flow for domestic water supply and crop irrigation. Sediment is an essential, integral and dynamic part of river basins, in polluted environments these act as sink of heavy metals and as a source of contaminants on the fluvial system. The management and sustainability of sediment should be assessed and secured to achieve good ecological status of the basins, for this task, approaches as ecological risk identification and geochemical indices are being used.Superficial sediment samples were collected in San Juan-Taxco river system. The results demonstrated that the degree of pollution from thirteen heavy metals and metalloids studied decreases in the following sequence: Cd> Zn > Pb > Cu > As > B > Mn > Ni > Fe > Co > Ba > Al and Cr. Cd made the most dominant contribution. Geochemical indices revealed important external anthropogenic influences in the rivers. The geochemical indices indicated very high enrichment for As, Cu, Pb and Zn, and extremely high for Cd in the three-rivers. The calculation of Pollution Load Index (PLI) showed in Cacalotenago River and in Taxco River are the sites with the highly contaminated sediments. PLI values were very high in all the samples sites due mining tailings erosion, wastewater and agriculture run off. Cd, Zn, Pb, Cu and As were the main potential risk elements that will cause harmful biological effects in the riverine environment.

The urban area of Puebla Valley aquifer is seated in Puebla City and neighbor municipalities. Puebla is the fourth largest city in Mexico, where there are significant industrial zones and a large population. Water needs are almost exclusively met by groundwater, which has brought intense exploitation of groundwater resources and water quality degradation. The present study investigates the hydrogeochemical changes in groundwater, particularly focuses on the chemical changes produced by upwelling mineralized water. These concentrations may represent potential risks to the health of the population. The groundwater presented five types of families Ca-HCO3, Mg-HCO3, Mix-HCO3, HCO3-Ca-SO4 and Ca-SO4. The high concentrations of sulphates, calcium and magnesium are reflected in high TDS and Total Hardness. The samples collected showed detectable concentrations of F−, Fe, Mn, Ba, Sr, Cu, Zn, B and Li. The limitations for its use as drinking water are given by the high values of TDS, sulphates, total hardness and Mn. Geochemical modeling using Geochemist's Workbench (GWB) and PHREEQC software enabled the computation of the saturation index of mineral phases with ions in solution and speciation ions. Groundwater was initially in equilibrium with calcite; however, due to the changes in hydrogeological conditions, gypsum and dolomite are being dissolved until new equilibrium conditions are met. The additional calcium and carbonate in the water causes calcite to become oversaturated and to precipitate. Evidence of dedolomitization reactions and common ion effect is illustrated by concurrent increases in calcium and magnesium concentrations in the groundwater.

One of the outstanding activities in the water resources management in recent years is the consideration of the environment as a major player within the watershed. To move from theory to practice in this topic, it is necessary to establish a diagnosis in terms of water volume. In other words, to associate each condition that sustains the environment, mainly the inflow of water into the basin. This work shows the case of the zone known as Soconusco in the cost of Chiapas state, in south Mexico, where there are four main rivers: Cintalapa, Despoblado, Vado Ancho and Huixtla. Those rivers drain most of the running off in the basin, first to the biosphere reserve (BR) La Encrucijada and then to the Pacific Ocean, interacting with the lagoon system there. A groundwater balance was done, estimating the volume that the aquifer Acapetahua discharges into the sea. Subsequently, the draining volume was estimated by precipitation and the result was checked with the hydrometric record. In the dry season period the difference between the last two values provides the volume of water that comes from the underground source. Its annual average value is acceptably close (20 % difference) to the volume of natural drainage obtained from the groundwater balance. Therefore, it was assumed that the minimum value drains into La Encrucijada BR (average per year) with the available information.

The intensive groundwater extraction in Mexico over the years has caused adverse effects, included groundwater level decline, subsidence, and groundwater quality modifications. This study aimed at determining the hydrochemical changes produced by intensive groundwater extraction in Mexico divided into three sectors—north, central, and south of the country. The groundwater quality deterioration due its intensive extraction can be caused by many processes such as, upwelling geothermal or/and mineralized water from deeper aquifers in response to lowering of the potentiometric surface, due to heavy pumping that favors the induction of the flow-through of faults, geological fractures, or deeper wells with a higher concentration of some elements (Fluor, Arsenic, Sodium, Potassium, Nitrates, Sulfates, Chlorides, Vanadium and Boron). Also, the intensive groundwater use favors the infiltration of organic pollutants from the sewerage and percolation of rainwater, resulting in the rapid transport of groundwater and contaminants throughout the aquifer.

Groundwater is the most important source for water supply in the urban zone of Puebla. Economic and industrial growth has caused a high demand for water. Intense extraction of groundwater has led to a significant decline in groundwater levels and degradation of quality. This study aimed to define the groundwater quality with the assessment of the hydrochemical changes produced by intensive water exploitation in the urban area of Puebla City. A general decline in the groundwater level has been found over the years, at a rate of as much as 1–2 m/y. Two ground fissures were identified in the same location as the drawdown cone. An evolution in the chemical composition and a change in the water-type classification were observed over the years. The increase of sulfates, calcium, and magnesium concentrations in the upper aquifer has been caused by upwelling mineralized water from the deep aquifer, where the hydraulic gradient of the groundwater table levels favors the induction of the flow-through of the fault and geological fracture and mixes with water from the upper aquifer. Concentrations above the limits recommended by the criteria established for Mexican law of trace elements and heavy metals were detected for the first time, and their origin can be attributed to natural and anthropogenic sources.

The Cuatrocienegas area is useful for the investigation of the effect of groundwater extraction in the Chihuahuan freshwater xeric ecoregion. It has been investigated at this time using a selection of geochemical indicators (major, minor and trace elements) and δ34S data, to characterize the origin of groundwater, the main geochemical processes and the mineral/groundwater interactions controlling the baseline geochemistry. The area is composed of limestones of Mesozoic age, with a composite thickness of about 500 m, overlaid by basin fill (poorly consolidated young sediments). Substantial water extraction and modification of natural discharges from the area along the last century have produced a detrimental impact on ecosystem structure and function. Water–rock interactions, mixing and evaporative processes dominate the baseline groundwater quality. Natural recharge is HCO3–Ca type in equilibrium with calcite, low salinity (TDS

The Valley of Puebla aquifer (VPA), at the central region of Mexico, is subject to intensive exploitation to satisfy the urban and industrial demand in the region. As a result of this increased exploitation, a number of state and federal agencies in charge of water management are concerned about the problems associated with the aquifer (decline of groundwater table, deterioration in water quality, poor well productivity and increased pumping and water treatment costs). This study presents a groundwater management model that combines “MODFLOW” simulation with optimization tools “MODRSP”. This simulation–optimization model for groundwater evaluates a complex range of management options to identify the strategies that best fit the objectives for allocating resources in the VPA. Four hypothetical scenarios were defined to analyze the response of the hydrogeological system for future pumping schemes. Based on the simulation of flow with the MODFLOW program, promising results for the implementation of the optimization of water quantity were found in scenarios 3 and 4. However, upon comparison and analysis of the feasibility of recovery of the piezometric level (considering the policy of gradual reductions of pumping), scenario 4 was selected for optimization purposes. The response functions of scenario 4 were then obtained and optimized, establishing an extraction rate of 204.92 millions of m3/year (Mm3/year). The reduction in groundwater extraction will be possible by substituting the volume removed by 35 wells (that should be discontinued) by the same volume of water from another source.

The spatial and temporal variation of water quality in the urban area of the Puebla Valley aquifer was evaluated using historical and present data obtained during this investigation. The current study assessed water quality based on the Water Quality Index developed by the Canadian Council of Ministers of the Environment (CCME-WQI), which provides a mathematical framework to evaluate the quality of water in combination with a set of conditions representing quality criteria, or limits. This index is flexible regarding the type and number of variables used by the evaluation given that the variables of interest are selected according to the characteristics and objectives of development, conservation and compliance with regulations. The CCME-WQI was calculated using several variables that assess the main use of the wells in the urban area that is public supply, according to criteria for human use and consumption established by Mexican law and international standards proposed by the World Health Organization. The assessment of the index shows a gradual deterioration in the quality of the aquifer over time, as the amount of wells with excellent quality have decreased and those with lower index values (poor quality) have increased throughout the urban area of the Puebla Valley aquifer. The parameters affecting groundwater quality are: total dissolved solids, sulfate, calcium, magnesium and total hardness.

"Con objeto de conocer la evolución de los procesos sedimentarios en la parte baja del río Verde, Oaxaca, se realizaron mediciones en dos núcleos de sedimentos. El fechado y determinación de la tasa de sedimentación, se realizó utilizando los isótopos radioactivos Plomo-210 y Cesio-137, que sirven como indicadores de períodos de deposición de los últimos 100 años. La velocidad de sedimentación en el Río Verde obtenida por medio del isótopo Pb -210 es 0.69 a 0.89 cm/año. Por otro lado, la velocidad de sedimentación en la zona de estudio mediante el isótopo Cs-137 es del orden de 0.61 cm/año y 0.87 cm/año. El método de Cesio-137 proporciona marcadores distintivos de eventos, mientras que el método de Plomo-210 proporciona pendientes de concentración, que al aplicarse de manera conjunta proporcionan una validación de ambos métodos. En este estudio, los dos métodos coinciden en los valores de sedimentación para la zona del Río Verde. Los resultados de este trabajo permiten conocer la dinámica de los procesos de transporte de sedimentos en la zona, información que resulta útil para la planeación de obras hidráulicas y estimación de los impactos ambientales, así como la implementación de las medidas de mitigación correspondientes."

SYNOPTIC ABSTRACTIn insurance practice, premiums are fixed according to well-known established principles, and depend on some parameters of the total claims distribution. This practice assumes that the claims process is known and does not change with time. In this paper, principles of dynamic programming are applied to obtain adaptive premium control policies under very relaxed assumptions on the distribution of the total amount of claims. A Markov control model is proposed to describe the corresponding risk process. Simulation of several different types of Markov processes shows that the proposed Markov control model works well.

A test for randomness based on a statistic related to the complexity of finite sequences is presented. Simulation of binary sequences under different stochastic models provides estimates of the power of the test. The results show that the test is sensitive to a variety of alternatives to randomness and suggest that the proposed test statistic is a reasonable measure of the stochastic complexity of a finite sequence of discrete random variables.

The distribution of primates has been diminishing during the last decades because of fragmentation and disappearance of habitat (Estrada and Coates-Estrada, 1994). As a consequence, the geographic distribution is no longer continuous and is comprised of areas relatively inaccessible to people. Fragmented habitat is where some primates manifest a great behavioral elasticity as an adaptive response to changes in their environment (Chivers, 1991; Garcia-Orduna, 1996; Rodriguez-Luna, 2000). The renewed interest for the study of primates under different environmental conditions is attributed to a change in perspectives of theory and methodology for research. Chivers (1986) suggested that, as a complement to the study of the survival of primates in disturbed habitat, work must be developed in different-sized fragments of tropical forest.