Isotope tracing of submarine groundwater discharge offshore Ubatuba, Brazil: results of the IAEA–UNESCO SGD project

Results of groundwater and seawater analyses for radioactive (³H, ²²²Rn, ²²³Ra, ²²⁴Ra, ²²⁶Ra, and ²²⁸Ra) and stable (D and ¹⁸O) isotopes are presented together with in situ spatial mapping and time series ²²²Rn measurements in seawater, direct seepage measurements using manual and automated seepage meters, pore water investigations using different tracers and piezometric techniques, and geoelectric surveys probing the coast. This study represents first time that such a new complex arsenal of radioactive and non-radioactive tracer techniques and geophysical methods have been used for simultaneous submarine groundwater discharge (SGD) investigations. Large fluctuations of SGD fluxes were observed at sites situated only a few meters apart (from 0 cm d⁻¹ to 360 cm d⁻¹; the unit represents cm³/cm²/day), as well as during a few hours (from 0 cm d⁻¹ to 110 cm d⁻¹), strongly depending on the tidal fluctuations. The average SGD flux estimated from continuous ²²²Rn measurements is 17 ± 10 cm d⁻¹. Integrated coastal SGD flux estimated for the Ubatuba coast using radium isotopes is about 7 × 10³ m³ d⁻¹ per km of the coast. The isotopic composition (δD and δ¹⁸O) of submarine waters was characterised by significant variability and heavy isotope enrichment, indicating that the contribution of groundwater in submarine waters varied from a small percentage to 20%. However, this contribution with increasing offshore distance became negligible. Automated seepage meters and time series measurements of ²²²Rn activity concentration showed a negative correlation between the SGD rates and tidal stage. This is likely caused by sea level changes as tidal effects induce variations of hydraulic gradients. The geoelectric probing and piezometric measurements contributed to better understanding of the spatial distribution of different water masses present along the coast. The radium isotope data showed scattered distributions with offshore distance, which imply that seawater in a complex coast with many small bays and islands was influenced by local currents and groundwater/seawater mixing. This has also been confirmed by a relatively short residence time of 1–2 weeks for water within 25 km offshore, as obtained by short-lived radium isotopes. The irregular distribution of SGD seen at Ubatuba is a characteristic of fractured rock aquifers, fed by coastal groundwater and recirculated seawater with small admixtures of groundwater, which is of potential environmental concern and has implications on the management of freshwater resources in the region.     

Geochemical characteristics of surficial sediments in a tropical estuary, south-west India

Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones.     

A special adaptation to planktonic life in larvae of the Cassoidea (=Tonnoidea) (Gastropoda)

Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily.     

To stay or to go: voluntary survivor turnover following an organizational downsizing

This paper examines the relationship between survivor reactions to a downsizing and retention subsequent to a downsizing. We hypothesize that survivors who experience the downsizing as distributively, procedurally, and interactionally just and who see top management as trustworthy will feel more attached to the organization because each reduces the threat inherent in downsizing. In addition, we hypothesize that survivors who feel empowered will also feel more attached to the organization because they feel better able to cope with the downsizing. We further hypothesize that those survivors who feel more attached to the organization following the downsizing will be more likely to remain with the organization in the coming year. The theoretical model is tested on a sample of aerospace employees who survived an organizational downsizing. The trustworthiness of management, distributive justice, procedural justice, and three dimensions of empowerment are found to facilitate more organizational attachment. Higher levels of attachment are found, in turn, to facilitate less voluntary turnover in the year following the downsizing. Copyright © 2002 John Wiley & Sons, Ltd.     

Utility of stormwater monitoring.

Stormwater runoff is now a major contributor to the pollution of coastal waters in the United States. Public agencies are responding by requiring stormwater monitoring to satisfy the National Pollutant Discharge Elimination System stormwater permit. However, studies to understand the utility of the current programs or to improve their usefulness have not yet been performed. In this paper, we evaluate the land-use-based program, the industrial stormwater permit program, and beach water-quality monitoring in the County of Los Angeles, California, to determine if the results will be helpful to planners and regulators in abating stormwater pollution. The utility of the program has been assessed based on the programs' ability to accurately estimate the emissions for different classes of land use. The land-use program appears successful, while the industrial monitoring program does not. Beach water-quality monitoring suffers from a lack of real-time monitoring techniques. We also provide suggested improvements, such as sampling method and time, and parameter selection.