The interpretation of body trace metal concentrations in neogastropods from Hong Kong.

Three species of neogastropods, i.e., Thais clavigera, Thais luteostoma and Morula musiva, were collected from 12 sites in the coastal waters of Hong Kong, including clean and known metal-enriched ones. Accordingly, body trace metal concentrations varied greatly. Copper and zinc body concentrations compared poorly with those of accepted biomonitors and presumed metal contamination profiles. Much is known about the feeding ecology of neogastropods on local shores and where direct observational data were not available, their diets could, nevertheless, be estimated reliably. Accumulated metal concentrations can be interpreted with regard to dietary history. T. luteostoma, for example, had body copper concentrations of 51.8 microg g(-1) on an exposed shore and a diet of mainly barnacles. In contrast, on a sheltered shore (but only some 250 m distant) where the diet consisted mainly of oysters, body copper concentrations were approximately 15 times greater at 833 microg g(-1). Similar results were obtained for T. clavigera. The results of this analysis suggest that neogastropods can play a significant role in trace metal trophic transfer studies, especially as their representatives are intertidally and subtidally ubiquitous and can be spatially separated into tropical specialists and temperate generalists.     

Isotope characterization of lead in galena from ore deposits of the Aysén Region, southern Chile

Lead isotope analyses of galena from five ore deposits and six prospects in the Aysén region of southern Chile are reported. Most of the deposits are either low sulfidation epithermal gold–silver veins or skarn and manto deposits; the majority are either suspected to be, or dated as, Late Jurassic to mid-Cretaceous. Galena lead isotope data for most of the deposits from southern Chile cluster near the “orogene” within a “plumbotectonic” model framework. Average values (²⁰⁶Pb/²⁰⁴Pb=18.53, ²⁰⁷Pb/²⁰⁴Pb=15.63, and ²⁰⁸Pb/²⁰⁴Pb=38.50) are near Jurassic to Cretaceous model ages on the “orogene” curve of Zartman and Doe (1981) and the second-stage curve of Stacey and Kramers (1975) on a ²⁰⁶Pb/²⁰⁴Pb versus ²⁰⁷Pb/²⁰⁴Pb plot. These model ages are compatible with absolute ages as currently known. The elongate trends in the general cluster indicate mainly an orogenic model fit, suggesting variable mixing of lead from different sources, mainly model upper crust and lesser model mantle and lower crust reservoirs. Galena lead associated with one deposit (El Faldeo) is relatively radiogenic, and lies near a Jurassic age on the “upper crustal” curve of Zartman and Doe (1981), which is compatible with the Ar/Ar age of the deposit. Galena lead isotope clusters define three main groups of deposits. These three groups appear to be related to three mineralizing events, dated by K–Ar and Ar/Ar, in the Late Jurassic (group 3), and in the Early and mid-Cretaceous (groups 1 and 2 respectively). Averages for group 1, the northern group including El Toqui and Katerfeld, are ²⁰⁶Pb/²⁰⁴Pb=18.51, ²⁰⁷Pb/²⁰⁴Pb=15.62, ²⁰⁸Pb/²⁰⁴Pb=38.48. Averages for group 2, the southern group with Fachinal and Mina Silva, are ²⁰⁶Pb/²⁰⁴Pb = 18.56, ²⁰⁷Pb/²⁰⁴Pb=15.63, ²⁰⁸Pb/²⁰⁴Pb=38.52. Averages for group 3, the southernmost group with the El Faldeo, Lago Chacabuco and Lago Cochrane prospects, are ²⁰⁶Pb/²⁰⁴Pb=18.83, ²⁰⁷Pb/²⁰⁴Pb=15.65, ²⁰⁸Pb/²⁰⁴Pb=38.63. The Cretaceous deposits (groups 1 and 2) contain orogene-type lead that becomes increasingly radiogenic southward. Lead from the Late Jurassic deposits (group 3) appears to reflect mixing of orogene lead with highly radiogenic lead. The observed linear array of lead in group 3 probably reflects mixing of orogene lead with highly radiogenic lead, which was likely extracted by selective leaching of mineralizing hydrothermal solutions from the metamorphic basement. Received: 10 July 1999 / Accepted: 15 July 2000     

Urban renewal in East African port cities: Mombasa's Old Town waterfront

The urban waterfront redevelopment diaspora, formerly confined to advanced countries, is starting to impact upon coastal settlements in former colonial territories. In diverse contexts ranging from postcolonialism and globalization to cultural revival and tourism development, developing countries are seeking to revive their historic port cities. This paper reports on the experience of Mombasa, Kenya, where waterfront redevelopment is a problematic element in the conservation of the historic urban core, and relates local issues to wider policies, relevant literature and experience elsewhere.     

Deformation and metamorphism of Devonian rocks in the outer Solund area, western Norway: implications for models of Devonian deformation

Many modern accounts of the Devonian rocks of western Norway, which emphasise the extensional processes by which the basins were formed, tend to ignore or gloss over the deformation and metamorphism which these rocks have suffered during contractional deformation. The present account describes extensive ductile folding, penetrative cleavage formation and low-grade regional metamorphism developed in the Devonian strata of the outer Solund region. Although the deformation in this area is more intense than in other Devonian basins, it belongs to the same movement plan. It will also be shown that the Devonian rocks of the Scandinavian Caledonides apparently share a common tectonothermal development. This regional contractional event, conceptually, may relate either to a Mid-Late Devonian arc-continent collision, or to a transpressional strain regime.     

Review of Lagrangian stochastic models for trajectories in the turbulent atmosphere

We review the theoretical basis for, and the advantages of, random flight models for the trajectories of tracer particles in turbulence. We then survey their application to calculate dispersion in the principal types of atmospheric turbulence (stratified, vertically-inhomogeneous, Gaussian or non-Gaussian turbulence in the surface layer and above), and show that they are especially suitable for some problems (e.g., quantifying ground emissions).     

Effects of stormwater nutrient discharges on eutrophication processes in nearshore waters of the Florida keys

Rainfall events cause episodic discharges of groundwaters contaminated with septic tank effluent into nearshore waters of the Florida keys, enhancing eutrophication in sensitive coral reef communities. Our study characterized the effects of stormwater discharges by continuously (30-min intervals) measuring salinity, temperature, tidal stage, and dissolved oxygen (DO) along an offshore eutrophication gradient prior to and following heavy rainfall at the beginning of the 1992 rainy season. The gradient included stations at a developed canal system (PP) on Big Pine Key, a seagrass meadow in a tidal channel (PC), a nearshore patch reef (PR), a bank reef at Looe Key National Marine Sanctuary (LK), and a blue water station (BW) approximately 9 km off of Big PIne Key. Water samples were collected at weekly intervals during this period to determine concentrations of total nitrogen (TN), ammonium (NH₄ ⁺), nitrate plus nitrite NO₃ ^? plus NO₂ ^?), total phosphorus (TP), total dissolved phosphorus (TDP), soluble reactive phosphorus (SRP), and chlorophyll a (chl a). Decreased salinity immediately followed the first major rainfall at Big Pine Key, which was followed by anoxia (DO <0.1 mg I^?1), high concentrations of NH₄ ⁺ (≈24 μM), TDP (≈1.5 μM), and chl a (≈20 μg I^?1). Maximum concentration of TDP (≈0.30 μM) also followed the initial rainfall at the PC, PR, and LK stations. In contrast, NH₄ ⁺ (≈4.0 μM) and chl a (0.45 μg I^?1) lagged the rain event by 1–3 wk, depending on distance from shore. The highest and most variable concentrations of NH₄ ⁺, TDP, and chl a occurred at PP, and all nutrient parameters correlated positively with rainfall. DO at all stations was positively correlated with tide and salinity and the lowest values occurred during low tide and low salinity (high rainfall) periods. Hypoxia (DO <2.5 mg I^?1) was observed at all stations follwing the stormwater discharges, including the offshore bank reef station LK. Our study demonstrated that high frequency (daily) sampling is necessary to track the effects of episodic rainfall events on water quality and that such effects can be detected at considerable distances (12 km) from shore. The low levels of DO and high levels of nutrients and chl a in coastal waters of the Florida Keys demand that special precautions be exercised in the treatment and discharge of wastewaters and land-based runoff in order to preserve sensitive coral reef communities.     

Catchment evaporation and potential evaporation further development of a climatologic relationship

When evaporation from the surfaces of a region is limited by the availability of moisture the resultant changes in the temperature and humidity of the overpassing air are reflected in the potential evaporation. Such interactions have provided the basis for the progressive development of a model in which the regional evaporation, a product of climatic, soil moisture and vegetative processes, is estimated from its effects on potential evaporation or on representative climatological observations. Further improvements are presented and the results are tested with previously published hydrologic and climatologic data from twenty river catchments in Canada and Ireland. These catchments have a range in annual runoff of approximately zero to one meter and a range of snow cover duration from almost zero to six months. Comparison of model predictions with precipitation less runoff estimates for five year periods provides reasonable evidence for the validity of the model with a maximum deviation of 44 mm yr⁻¹, or 9%, and a standard error of estimate of 26 mm yr⁻¹. Seasonal comparisons permit insights into the variability of catchment storage and the effects of climate and topograpy on regional evaporation.     

Adjusting to Policy Expectations in Climate Change Modeling

This paper surveys and interprets the attitudes of scientists to the use of flux adjustments in climate projections with coupled Atmosphere Ocean General Circulation Models. The survey is based largely on the responses of 19 climate modellers to several questions and a discussion document circulated in 1995. We interpret the responses in terms of the following factors: the implicit assumptions which scientists hold about how the environmental policy process deals with scientific uncertainty over human-related global warming; the different scientific styles that exist in climate research; and the influence of organisations, institutions, and policy upon research agendas. We find evidence that scientists' perceptions of the policy process do play a role in shaping their scientific practices. In particular, many of our respondents expressed a preference for keeping discussion of the issue of flux adjustments within the climate modeling community, apparently fearing that climate contrarians would exploit the issue in the public domain. While this may be true, we point to the risk that such an approach may backfire. We also identify assumptions and cultural commitments lying at a deeper level which play at least as important a role as perceptions of the policy process in shaping scientific practices. This leads us to identify two groups of scientists, pragmatists and purists, who have different implicit standards for model adequacy, and correspondingly are or are not willing to use flux adjustments.