SOLIDS DISTRIBUTION IN LAKE CHAPALA,MEXICO1

ABSTRACT: Lake Chapala is the largest natural water body in Mexico and also one of the most important shallow lakes in Latin America. For the past several years it has suffered various environmental problems such as the upstream overuse of water, contamination, and sedimentation. For the past 10 years the lake has had less than 50 percent of its historical water level over the past century. No criteria are reported in the literature that establish a water storage volume that will guarantee water quality conditions necessary for the survival of the lake. After determining the behavior of total solids concentrations in relation to the variations in the lake's depth, we proposed a minimum water column height of 5.0 m, representing a storage volume of about 5,000 Mm³. This volume would result in the recommended water quality standards for total dissolved solids. Calculated distribution maps show that the total solids concentration in the lake has increased since the end of the 1970s. The solids are primarily concentrated in the eastern part of the lake, as a consequence of the high solids discharged from the Lerma River, its main tributary.     

A SIMULATION OF SMOOTH-VARIABLE INTENSITY RAINFALL PATTERNS1

ABSTRACT: Continuous rainfall patterns are currently simulated by approximating them by stair-stepped (piece-wise) patterns. The effects of this approximation on infiltration and runoff processes are not well known. A new technique for simulating smooth-variable intensity rainfall patterns is presented. This technique is based on the fundamental principles of a moving water head in a container. The proposed technique is general and capable of simulating any rainfall pattern. However, as the rainfall pattern gets more complicated, the equipment required for simulation becomes more involved. The proposed technique has been tested experimentally. A close agreement was found between the theoretical and experimental simulations. It is concluded that the proposed technique might be very useful in studying the infiltration and runoff processes under variable intensity rainfall, especially for simple convex patterns.     

MODELING THE PERFORMANCE OF DEEP WASTE STABILIZATION PONDS1

ABSTRACT: The performance characteristics of a deep waste stabilization pond operating in Southeast Spain were studied for one year; the results show a high reduction in organic load and nutrients, as well as disinfection of the effluent, after a retention time that varies as a function of climatic conditions. Mathematical models describing its hydraulic, thermal, and biochemical bahavior are presented and compared with a set of measured data.     

Fetal spina bifida: What we tell the parents

Worldwide, about 150 000 infants are born with spina bifida yearly, making this condition one of the most common fetal central nervous system anomalies compatible with life. Over the last decade, major changes have been introduced in the prenatal diagnosis and management of spina bifida. In this review, we provide a brief summary of the current management of fetal spina bifida and present essential information that should be provided to expecting parents when their fetus has been diagnosed with spina bifida. This information is focused around common parental questions, as encountered in our typical clinical practice, to facilitate knowledge translation.     

In vitro mass multiplication of screw pines (<Emphasis Type="Italic">Pandanus</Emphasis> spp.) - an important costal bio- resource

An efficient in vitro mass multiplication protocol was developed for selected species of screw pine (Pandanus fascicularis Lam., P. furcatus Roxb.). The protocol could be successfully used for large scale production of planting materials leading to cultivation and making bio-fences or green belts in coastal areas, wetlands for protection and preventing soil erosion. This will facilitate the replenishment of the bio resource and also provide good breeding space for various fauna associated with it. For developing the tissue culture protocol, shoot tips and tillers from the mature plants were used as the explants. Surface sterilization with 0.1 % mercuric chloride for 1 min. Yielded good fraction (65 %) of contamination free explants. Explants inoculated in MS solid medium supplemented with 6-benzylaminopurine (BAP, 2.5 mg/l) and indole-3-acetic acid (IAA, 0.5 mg/l), induced 2–3 shoot buds in 5 weeks. These buds either individually or along with the explant portion, sub-cultured to fresh media containing the same hormonal combinations, resulted induction of 5–6 shoot buds in 4 weeks. Repeated subcultures of shoot buds in the same medium produced 8–10 shoot buds in every 4 weeks. Shoot elongation was achieved (~ 3 cm) by transferring the shoot clusters or individual shoots to basal medium, and the elongated shoots were rooted in vitro or ex vitro. Root induction in shoots (87.4 %) was achieved in MS medium supplemented with 0.1 mg/l indole-3-butyric acid (IBA). Rooted shoots were established in paper/polythene cups filled with fine sand, which subsequently recorded 85 % establishment under the shade-net house with proper irrigation. Plants grown in poly-bags were later successfully established in different field conditions and recorded 100 % survival.     

Accumulation and transfer of Hg, As, Se, and other metals in the sediment-vegetation-crab-human food chain in the coastal zone of the northern Brazilian state of Pará (Amazonia)

The high consumption of crabs (Ucides cordatus) stimulated interest in the present study on the northern coast of Brazil, which encompasses a preserved area of mangrove forest. The objective was to describe and quantify the transfer of metals from the muddy sediments to the leaves of the Rhizophora mangle, and thence the crabs and humans. The samples were collected along two transects, while samples of hair were obtained from local habitants. The pH, interstitial salinity, Eh (mV) were measured, the granulometry and mineralogical and multi-element chemical analyses were run, and the organic material determined. The sediments are silty-clayey, composed of quartz, kaolinite, iron oxides, and illite, as well as smaller portions of smectite, pyrite, halite, and high levels of SiO₂ (56.5 %), Al₂O₃ (18.5 %), and Fe₂O₃ (7 %). The elements Zn, Sr, As, and Zr are concentrated in the leaves, while the bioaccumulation of Zn, Se, Sr, and As was recorded in the crabs, of which, Se is the most concentrated in the tissue of the muscles and the hepatopancreas. The concentrations of nutrient and toxic elements were similar in all age groups (hair samples), with only Hg presenting an increasing concentration between infants and adults. The highest rates of transfer were recorded for the elements Zn and Se in the crabs and Hg in leaves and hair. The accumulation of metals in the leaves and crabs reflects the chemical composition of the sediments and low rates of sediment-vegetation-crab transfer, with the exception of Hg, which accumulated in the hair.