Desalination plants generate notable (>1,000 s m3) quantities of hypersaline brine which potentially affect the biological communities in the receiving area. We assessed whether proximity to a brine discharge point located off Gran Canaria (Canary Islands, eastern Atlantic) altered patterns in the abundance and assemblage structure of subtidal, soft-bottom, meiofauna. Samples were collected twice (May 2008 and January 2009) at 0, 15 and 30 m away from the brine discharge point, corresponding to a change in salinity from 45 to 36. Proximity to the brine discharge point affected overall meiofaunal abundances: lowest abundances were observed at 0 m (64.55 ± 39.86 ind 10 cm−2, mean ± SD) than at 15 (210.49 ± 121.01 ind 10 cm−2) and 30 m (361.88 ± 102.64 ind 10 cm−2) away from the brine discharge point. This pattern was particularly notable for the most conspicuous meiofaunal groups: nematodes and copepods, and meiofaunal assemblage structure also differed with varying proximity to the brine discharge point. Although multivariate techniques identified changes in salinity as a relevant driver of patterns in meiofaunal assemblage structure with varying proximity to the brine outfall, a shift in particle size composition between May 2008 and January 2009 also contributed to explain differences in meiofaunal abundances and assemblage structure with varying proximity to the brine discharge point. Hence, meiofauna can be considered a suitable tool to monitor environmental impacts derived from the discharge of hypersaline effluents on subtidal, soft-bottom, assemblages if potential confounding drivers, i.e. here temporal changes in particle size composition, are accounted for to avoid possible confusing interpretations. 相似文献
The present paper provides an overview of cold-water corals protection in the Hatton Bank deep-water fisheries through the implementation of the United Nations General Assembly resolution 61/105. The methodology and scientific evidence used to propose protection of cold-water coral ecosystems in the high seas (∼16,000 km2) are briefly summarised. The role of international agents and importance of interdisciplinary research for making management decisions are furthermore described. Implementation was slow because (i) of scarce initial scientific knowledge, (ii) research on the high seas was difficult and expensive, (iii) there were several international interests at stake, (iv) agreement from a number of agents was needed, and (v) international advisory and decision making processes were quite slow. Some lessons learned are also discussed since these may help to increase protection efficiency of deep-sea vulnerable marine ecosystems in the high seas. 相似文献
Clay-rich deposits are usually considered as hard materials to be eroded by wind. Data from both surface monitoring and field survey at the dry-up bottom of Aiby Lake present that clay-rich lacustrine deposits are easily broken down and eroded away by wind in the seasonal alternation process under the natural arid environment, and are the significant source of air dust. The surface of the clay-rich deposits is broken and softened by the freezing-and-thawing action in winter season and/or by salt and alkali action with precipitation. Impact of wind-input particles and plow of plant branches with wind force drive the clay-rich sediments moving. Wind picks up the clay pebbles and repeats the impaction further-ward onto the dry-up surface. Tremendous fine materials, including soft salts, are contributed to air dust, and transported in long distance.
Interaction of groundwater with As-bearing rocks has been proposed as one of three main sources of arsenic at Zimapán valley,
México. The complexity of the geology and hydrogeology of the valley make it difficult to identify the natural causes of arsenic
poisoning. Samples from the different rock outcrops and water from wells tapping various rock formations were analyzed. The
rocks from mineralized areas contained higher concentrations of arsenic with respect to the same formations in non-mineralized
areas. The arsenic minerals arsenopyrite, scorodite, and tennantite were identified in some rock samples. Higher temperature
and lower Eh values were found for those wells containing more arsenic. The physicochemical characteristics of these naturally
polluted well waters could be produced by arsenopyrite oxidation. The geochemical model PHREEQCI was used to perform the inverse
modeling of two wells located along the same fault. Arsenopyrite oxidation and scorodite dissolution appear to be the geochemical
processes producing the natural pollution according to the model. The release and transport of arsenic mainly occur through
fractures within the cretaceous limestones where the most productive wells are drilled. The presence of arsenic should be
expected also in other formations near mineralized zones in the Zimapán Valley. Field determinations of Eh and T could be
used to detect potentially polluted wells.
Received: 29 April 1999 / Accepted: 18 July 2000 相似文献
A model based on numerical solutions, which allows for solving the dispersion equation under variable recharge and velocity conditions, is developed to simulate solute transport in conduit flow aquifers during flow recession periods. As an example, the evolution of a tracer in the little known karst conduit that links the sinking stream of Oma valley to the Olalde spring is investigated in the karstic region of Santa Eufemia-Ereñozar (Basque Country, Spain). The model, with different hypothetical structures, allows for obtaining series of tracer breakthrough curves, which are fitted to experimental data using an optimization algorithm. These results, although they can be used to simulate the tracer evolution between the two points considered, do not allow for determining the internal structure and spatial disposition of contributions in the aquifer. 相似文献
A semi-numeric method by Herrera, Jiménez and Ruggeri is used to study the evolution of general relativistic spheres in the free streaming radiation approximation when specific contraction schemes are imposed and for particular oscillatory radiation profiles. On one hand, the emerging radiation is studied for oscillating contracting spheres, on the other, the variation of the boundary surface is analyzed when a pulsating profile is provided. We considered three particular equations of state previously studied. It is found that the oscillatory frequency of the surface for the equations of state considered coincide with the frequency of the oscillation for the radiation profile. 相似文献