Frequency of dry and wet spells in san salvador

Summary A study of the daily rainfall in San Salvador (El Salvador) has been made over a thirty year period 1918–47 in order to determine the dry and wet spells. It has been found that the extreme dry spells on the Pacific Coast of Central America last longer than in other climates, examined byHuttary. The occurrence of a dry spell in San Salvador lasting over half a year is being minutely examined, and the cause of its origin traced to orographic effects during northerly winds.

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Resumen Se estudiaron las observaciones diaras de la precipitación en San Salvador (El Salvador), realizadas en los aňos 1918–47. Resulta que en la costa Pacifica Centroamericana los períodos secos duran más que los períodos más largos en los climas estudiados porHuttary. Un período seco que duró más de medio aňo en San Salvador se analiza detenidamente, se supone que éste se habría originado en influencias orográficas efectivos cuando hay viento del norte.

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Dr.Heinz Dieterichs, Jefe meteorólogo en el Servicio Meteorológico Nacional de El Salvador,San Salvador (El Salvador, Central America).     

Organic compounds in the early atmosphere formed abiotically from atomic carbon

The recent discovery that atomic carbon occurs plentiful in olivines from mantle-derived rocks opens new aspects for the chemical evolution of the early atmosphere and the origin of life. It has been shown conclusively that atomic carbon which is dissolved in the model oxide MgO is capable of reacting in an O₂-free atmosphere with the lattice oxygen to give CO₂ and with the lattice hydrogen, derived from OH^–, to give a profuse variety of hydrocarbons.The diffusional processes and low temperature gas/solid interface reactions involved in these processes are expected to introduce, purely abiotically, isotope fractionation resulting in a¹³C enrichment of the CO₂ fraction and in a¹³C depletion of the hydrocarbon fraction which may be confused with the¹²C/¹³C isotope fractionation along biological pathways.Atomic carbon dissolved in olivines and in basalts shows a similar behaviour and yields similar quantities as C in MgO: 1–2 mg/g CO₂ and 25–100g/g hydrocarbons degassing between 400 and 1000 °C. On a geological scale this means that each cubic kilometer of basaltic magma degassing in an O₂-free atmosphere has the capacity of sending off about 3–6·10⁹ kg (2·10⁹ m³) of CO₂ and about 1–3·10⁸ kg (2·10⁸ m³) of hydrocarbons. The presence of water modifies the composition to give, among others, alcohols and organic acids.On the basis of these results we are led to the conclusion that the early atmosphere of the earth may have contained a very high concentration of abiotically formed organic compounds of great chemical complexity.

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Zusammenfassung Die Entdeckung des atomar gelösten Kohlenstoffs in Olivinen aus Mantelgesteinen führt zu neuen Vorstellungen über die Zusammensetzung der Uratmosphäre und Entwicklungsbedingungen des Lebens. Atomarer Kohlenstoff im MgO ist in der Lage, in einer O₂-freien Atmosphäre mit dem Gittersauerstoff zu CO₂ zu reagieren und mit dem aus OH^– stammenden Gitterwasserstoff eine große Vielfalt von organischen Verbindungen zu bilden.Diffusionsprozesse und Gas-Festkörper-Austauschreaktionen, die an diesen Reaktionen beteiligt sind, führen nach ersten Untersuchungen zu einer¹³C-Anreicherung im CO₂ und einer¹³C-Abreicherung bei den Kohlenwasserstoffen. Diese¹²C/¹³C-Fraktionierung ist gleichsinnig mit der biologischen¹²C/¹³C-Fraktionierung.Atomarer Kohlenstoff in Olivinen und Basalten zeigt ein sehr ähnliches Reaktionsverhalten wie im MgO und führt zu ähnlichen Reaktionsprodukten: 1–2 mg/g CO₂ und 25–100g/g Kohlenwasserstoffe zwischen 400–1000 °C. Übertragen auf geologische Verhältnisse bedeutet dies, daß jeder km³ eines entgasenden basaltischen Magmas 3–6·10⁹ kg (2·10⁹ m³) CO₂ und 1–3·10⁸ kg (2·10⁸ m³) abwüschen Kohlenwasserstoff abgeben kann. Die Anwesenheit von Wasser führt zur Bildung von Alkoholen und organischen Säuren. Diese Ergebnisse deuten darauf hin, daß die Uratmosphäre und die Ursuppe viel reicher waren als bisher angenommen an komplexen organischen Verbindungen, die rein thermisch entstanden sind.

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Résumé La découverte du carbone atomique dans les olivines du manteau entraîne de nouvelles idées sur la composition de l'atmosphère originelle et sur les conditions du développement de la vie. Comme l'est le cas pour le MgO, le carbone atomique dans les olivines est capable de réagir, dans une atmosphère exempte de O₂, avec l'oxygène du réseau cristallin en formant du CO₂, et avec l'hydrogène provenant des groupements OH^– du réseau, pour former une grande variété de composés organiques.Les processus de diffusion et d'échange gas-solide liés à ces réactions provoquent, d'après les premiers résultats, un enrichissement en¹³C dans le CO₂ et un appauvrissement en¹³C dans les hydrocarbures formés. Ceci ressemble au fractionnement dû à des réactions biologiques.Le comportement du carbone atomique et sa réactivité se retrouvent dans les basaltes et les olivines. La gamme des produits de réaction et leur quantité ressemble à celle du MgO: 1–2 mg/g CO₂ et 25–100g/g composés organiques. A l'échelle géologique ceci implique que chaque km³ de magma basaltique dégazé en contact avec une atmosphère exempte d'oxygène pouvait émettre 3–6·10⁹ kg, soit 2·10⁹ m³ de CO₂ et 1–3·10⁸ kg, soit 2·10⁸ m³ d'hydrocarbures abiotiques. La présence d'eau entraîne la formation d'alcools et d'acides organiques.La conclusion tirée de ce travail indique que l'atmosphère originelle et la»soupe primordiale» étaient plus riches qu'on ne l'a admis jusqu'à présent en composés organiques dûs à des processus purement thermiques, et donc abiotiques.

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. MgO , COg, -, , . , , — — ¹³ ₂ . ¹²/¹³ , . , , - : 1–2 / O₂ 25–100 / , 400–1000 . , 3–6·109 (2·10^{9 3}) ₂ 1– 3·10⁸ (2·10^{8 3}) . . , , , , .

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Presented in part at the meeting Precambrian Problems, Copenhagen, March 1981.     

Book reviews

Boundary-Layer Meteorology -     

Water quality deterioration at a karst spring (Gallusquelle,Germany) due to combined sewer overflow: evidence of bacterial and micro-pollutant contamination

The concurrent use of karst aquifers as drinking water resources and receptors of combined sewer overflow lacking appropriate pre-treatment may cause conflicts between drinking water supply and storm water management. A storm water tank (SWT) for combined wastewater is identified as the source of sporadic contamination of a karst spring (Gallusquelle, “Schwäbische Alb”, SW Germany) used for public water supply. Spring water quality was examined by routine and event sampling and by evaluating physicochemical and microbiological parameters. The total number of microbial colonies growing at 20°C and the number of Escherichia coli colonies rose to values up to four orders of magnitude higher than background, 2–5 days after overflow of the SWT. High concentrations of chloride, sodium, and total organic carbon (TOC) and high values of turbidity coincide with this increase. However, high bacterial contamination is also observed while turbidity and TOC are low. Several wastewater-related organic micro-pollutants such as chlorinated and non-chlorinated organophosphates were detected in the SWT and, depending on their K_ow values and their biodegradability, in lower concentrations at the spring.     

Shallow groundwater temperature response to climate change and urbanization

Groundwater temperatures, especially in shallow (quaternary) aquifers respond to ground surface temperatures which in turn depend on climate and land use. Groundwater temperatures, therefore, are modified by climate change and urban development. In northern temperate climate regions seasonal temperature cycles penetrate the ground to depths on the order of 10–15 m. In this paper, we develop and apply analytic heat transfer relationships for 1-D unsteady effective diffusion of heat through an unsaturated zone into a flowing aquifer a short distance below the ground surface. We estimate how changes in land use (urban development) and climate change may affect shallow groundwater temperatures. We consider both long-term trends and seasonal cycles in surface temperature changes. Our analysis indicates that a fully urbanized downtown area at the latitude of Minneapolis/St. Paul is likely to have a groundwater temperature that is nearly 3 °C warmer than an undeveloped agricultural area at the same geographic location. Pavements are the main cause of this change. Data collected by the Minnesota Pollution Control Agency (MPCA) in the St. Cloud, MN area confirm that land use influences groundwater temperatures. Ground surface temperatures are also projected to rise in response to global warming. In the extreme case of a doubling of atmospheric carbon dioxide (2 × CO₂ climate scenario), groundwater temperatures in the Minneapolis/St. Paul metropolitan area could therefore rise by up to 4 °C. Compounding a land use change from “undeveloped” to “fully urbanized” and a 2 × CO₂ climate scenario, groundwater temperatures are projected to rise by about 5 °C at the latitude of Minneapolis/St. Paul.