Horizontal transport,mixing and retention in a large,shallow estuary: Río de la Plata

We use field data and a high-resolution three-dimensional (3D) hydrodynamic numerical model to investigate the horizontal transport and dispersion characteristics in the upper reaches of the shallow Río de la Plata estuary, located between the Argentinean and Uruguayan coasts, with the objective of relating the mixing characteristics to the likelihood of algal bloom formation. The 3D hydrodynamic model was validated with an extensive field experiment including both, synoptic profiling and in situ data, and then used to quantify the geographic variability of the local residence time and rate of dispersion. We show that during a high inflow regime, the aquatic environment near the Uruguayan coast, stretching almost to the middle of the estuary, had short residence time and horizontal dispersion coefficient of around 77 \(\mathrm {m}^{2}\,\mathrm {s}^{-1}\) , compared to the conditions along the Argentinean coastal regime where the residence time was much longer and the dispersion coefficient (40 \(\mathrm {m}^{2}\,\mathrm {s}^{-1}\) ) much smaller, making the Argentinian coastal margin more susceptible for algae blooms.     

Humic substances. Part II†: Photophysical,photochemical and free radical characteristics

The effects of mercury (HgCl₂) on cell population, chlorophyll a concentration and rates of photosynthesis and excretion were investigated in the phytoplanktonic species Dunaliella minuta in laboratory cultures. Mercury, above 25ppb inhibited both cell population and chlorophyll a concentration approximately to the same extent, whereas the photosynthetic rate was inhibited to a significantly lesser degree. Although, the total photosynthetic rate of the tested organism was reduced, above a threshold concentration, the photosynthetic activity was not reduced under these conditions, but it was in fact significantly greater than that in the control culture. This may suggest that in D. minuta the inhibitory effect of mercury is primarily on cell division rather than cellular photosynthesis, which is enhanced by the fact mercury caused a significant increase of the mean cell volume. Mercury, also, decreased the growth rate and final cell yield. The excretory rate was markedly increased at concentrations ≥ 250 ppb of mercury, but at lower concentrations it tended to depend more on the physiological state of cells than on mercury concentration. In the different cultures, the photosynthetic activity showed variations which occurred without major changes in the chlorophyll a content per cell, which remained almost constant and independent of variations in cell size and growth conditions.     

Analysis,accumulation and central effects of trihalomethanes. I. bromoform†

The paper presents the results obtained in a study on the effects of organic micropollutants on the central nervous system of the rat, used herein as a suitable model for neurotoxicologic work. Bromoform, a member of the trihalomethane (THM) family, was the pollutant selected since it becomes a characteristic marker in the Barcelona potable water supply.

Analytical data on the GC‐ECD separation of THMs from other volatile halocarbons is presented. A mixed packed column 10% SE‐30/PEG 20M (94:6) at 70°C provides an adequate separation. The distribution of bromoform in rat plasma and tissues showed an accumulation in brain, kidney and fat, increasing in this order and a rapid elimination after 30 min. The effect on the central aminergic metabolism is studied by HPLC. The increased metabolic activity detected could be attributed either to an increased nervous activity, stimulating the metabolism of serotonin, or to its greater degradation.     

生态住宅的水环境规划:I. 水循环

生态住宅已成为住宅建设的发展趋势和潮流,水环境是生态住宅小区的重要组成部分。文章以中信保利达美景度假区为实例,根据度假区建筑总体规划方案,结合当地自然条件和水环境现状,探讨生态住宅小区的水环境规划,全面统一规划住宅小区内各种水系统,提出小区水环境总体规划方案,充分发挥各系统的功能,使其相互衔接、协调与补充。重点对项目所在区域开发前后的水量平衡,水库的水位变化及其安全性,极端气候条件下的库区水量变化及其因应对策,高尔夫球道的用水方案以及项目开发后的水循环模型做了深入探讨,旨在为生态住宅的水环境建设提供范例。     

南岳森林土壤的研究-Ⅲ.土壤颗粒组成

本文介绍了南岳森林土壤颗粒组成状况及其与环境间的关系,以及土壤的颗粒组成状况对其理化性质的影响。研究表明,南岳土壤质地主要为粉壤土、面砂土和壤粘土等。土壤质地的差异主要受植被类型、植物生长状况、放牧严重与否的影响,其次是受坡度和气候条件的影响。土壤颗粒组成状况显著地影响土壤的速效磷、速效钾、浸水容重、吸湿率、烧失率、pH值等,对土壤紧实度、有机质、碱解氮也有一定的影响。     

Batterienrecycling: Möglichkeiten zur Erhöhung der Rücklaufquote

Separate collection and exploitation of used batteries facilates the recycling and eventual waste management of such heavy metals as mercury and cadmium. It is thereby possible to regain raw materials like zinc, manganese and iron for the raw material cycle. Although the collection and recycling of used batteries in Switzerland is financed by a prepaid disposal fee, their returning rate of almost 60% is too low for several reasons. A questionnaire survey carried out on 2000 households revealed the following frequenthy: People collecting paper, glass, aluminium, compost and tinplate, are more separate used batteries from ordinary garbage. The number of collecting points is supposed to be sufficient, but not all of them are sufficiently marked. The prepaid disposal fee (VEG) should become obligatory so that it would be possible to compensate the collecting points. It is not obvious from the results of the survey if the introduction of a deposit of batteries would raise the retourning rate. As far as advertising is concerned, only the “battery bag” sent to every household by the BESO seemed to influence the collecting behaviour in a positive way, poster advertising had only little effect. Appeals in newspapers, radio and television did not show any changement of the collecting behaviour. However, information and knowledge about batteries and their recycling do have a positive influence in the collecting behaviour of the consumers in this specific case.