Stability of a Coal Waste Artificial Reef

The feasibility of using U.K. coal-fired power station waste materials for artificial reef production is being examined. in June, 1989, an experimental artificial reef was constructed in Poole Bay, off the central south coast of the U.K., using three different mixtures of pulverised fuel ash (PFA), flue gas desulphurisation (FGD) gypsum and slurry, stabilized with cement and formed into blocks. Fifty tonnes of 40 × 20 × 20 cm blocks were formed into eight conical reef units replicating three different PFA/gypsum mixtures and one concrete control. the reef structure is 10m below chart datum on a flat sandy sea-bed.

Combustion of coal concentrates the heavy metal content in the resultant ash. the purpose of stabilization of the ash as blocks is twofold: to immobilize heavy metals (or other components) and to provide hard substratum for the attachment of organisms. to examine the effectiveness of this stabilization and hence the environmental compatibility of the block materials, heavy metal (Cd, Cr, Cu, Pb, Mn, Ni, Zn) content of the blocks has been monitored routinely over two years, to determine leaching rates. Sectional profiles indicate partial replacement of calcium content by magnesium. Associated with this there has also been some redistribution of heavy metals. Only in the case of cadmium has there been a detectable loss from the surface of blocks. Chromium and manganese concentrations appear to have increased. the metal content of the reef epibiota (including ascidians, Ascidia mentula; hydroids, Halecium spp.; bryozoans, Bugula spp. and red algae) growing on the ash blocks has been compared to that of epibiota attached to the concrete controls and surrounding sea-bed. to date no evidence of excess bioaccumulation of metals has been detected.

The physical integrity of the ash reef blocks has been maintained. There is evidence that the blocks are increasing in compressive strength.

An indication of the fishery enhancement potential of the experimental structure is given by the presence of eight commercially fished species (crustaceans and molluscs) including lobsters (Homarus gammarus).     

Water and sustainable development

In this paper, it is proposed that water resources should be managed as an integral part of a nation's social and economic development. Water resources managers should broaden their scope of work to include an integrated management approach. Instead of the traditional 'supply oriented approach' in which they act in response to ever-increasing demands for water from different sectors of the economy, water resources management agencies should play a more active role in guiding and stimulating socioeconomic development through more efficient water use. Demand management should be an important tool which should go beyond the improvement of technical efficiencies. Most important is to develop economic and institutional approaches that accept charging for the full costs of the utilization and management of water resources. Implementation of such an approach will require more sectoral integration than is currently the case and will have considerable implications for organizations, staffing, institutional arrangements and corresponding capacity building.     

Importance of eating habits and sample size in the estimation of environmental mercury contamination using biological indicators

The importance of eating habits and the number of fish sampled in the estimation of mercury environmental contamination through biological indicators was studied. The species used were one with piscivorous habits (Anguilla anguilla) and another with omnivorous habits (Ciprinus carpio). From one original sample for each species, randomized samples were generated using the subroutine GGSRS from the mathematics library IMSL, and later the statistical significance of Pearson's correlation coefficient for the relationship between fish weight and mercury concentrations in muscle was obtained for each random sample. The results show that the use of omnivorous species such as Ciprinus carpio as a biological indicator of contamination enables us to carry out estimations with a greater degree of confidence than when piscivorous species such as Anguilla anguilla are used.     

Mikrobielle Sanierung von 2,4,6-Trinitrotoluol (TNT) kontaminierten Böden

Within the limits of a feasability study abouton-site bioremediation methods for TNT-contaminated soils, composting was chosen as a very promising and cheap method. This method was critically compared with those described in the literature and was primarily rated under ecotoxicological aspects. The investigated location is the former munition plant «Tanne» in the aerea of Clausthal-Zellerfeld in Lower Saxony, Germany. To estimate the autochtonic microflora, we assessed the number of aerobic heterotrophic bacteria and determined their respiration activity in soils. In addition, we isolated bacteria and examined their capacity to metabolize TNTin vitro. Both the amount of autochtonic microrganisms (4.7×10⁸ to 1.2×10¹⁰ colony forming units (cfu)/kg dryweight) as well as their respiration activity did not correlate with the concentrations of nitrotoluenes in the soils. With high contaminated soil (20 g TNT/kg dry weight) we carried out a small compost in the range of 10 liters. During 28 days of composting TNT-concentration decrease over 90% and only minor amounts of monoaminodinitrotoluenes were generated. However, an acidic pretreatment of the compost material at the end of the reaction showed that TNT could be partially resolved under these extreme conditions and that an ecotoxicological risk may still exist. Possible changes in the realization of the composting process in order to make sure that the contaminants are savely bound to the humin matrix are discussed.     

The gill symbiont of the hydrothermal vent mussel Bathymodiolus thermophilus is a psychrophilic,chemoautotrophic, sulfur bacterium

Certain hydrothermal vent invertebrates, e.g. Riftia pachyptila and Calyptogena magnifica, are clearly established as harboring dense populations of chemoautotrophic sulfur bacteria in specialized tissues. By contrast, the physiological characteristics of the abundant intracellular gill symbiont of the vent mussel Bathymodiolus thermophilus have been questioned. The low activities of enzymes diagnostic for CO₂ fixation (Calvin cycle) and for sulfur-driven energy generation, as measured by other investigators, have been attributed to bacterial contamination of the gill surface. Based on research at the Galápagos Rift hydrothermal vents in 1988 and subsequent laboratory experiments, the current study confirms that the B. thermophilus symbiont is a psychrophile for which thiosulfate and sulfide stimulate CO₂ fixation. It strongly indicates that the symbiont is a chemoautotroph by establishing the following: (1) Sulfide and thiosulfate can stimulate CO₂ fixation by partially purified symbionts by up to 43-fold and 120-fold, respectively; (2) the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of the symbiont is sufficient to account for its sulfide- or thiosulfate-stimulated CO₂ incorporation; (3) the symbiont's molar growth yield on thiosulfate, as judged by CO₂ incorporation, is indistinguishable from that of free-living chemoautotrophs. Due to the high protein-degrading activity of B. thermophilus gill lysate, it is also suggested that host lysis of symbionts plays a more important role in the nutrition of the vent mussel than in R. pachyptila or C. magnifica, for which no comparable protein-degrading activity was found.     

Distribution of diatoms in the surficial sediments of the Mangyung-Dongjin tidal flat,west coast of Korea (Eastern Yellow Sea)

The relationship between the distribution of benthic diatoms and sediment characteristics of the Mangyung-Dongjin tidal flat on the west coast of Korea was investigated during June and July 1988. Diatoms were collected from the upper 5 mm of sediments at 60 sites along eight transect lines running perpendicular to the shore line. Of the 371 taxa encountered in the study area, 88% were pennate diatoms. Genera represented by the greatest number of species were Navicula, Nitzschia, Amphora, Cocconeis, Fragilaria and Achnanthes. The most abundant species were Paralia sulcata, Navicula sp. #1, N. arenaria and Cymatosira belgica; all were broadly distributed across the tidal flats. The 60 sites could be assigned to eight clusters with respect to similarity in species composition. Discriminant analysis showed that separation cluster was primarily related to the mean grain size of the sediment. The species could not be separated into groups based on similarities in occurrence; a high degree of spatial overlap was observed. The preferences of the more abundant species for grain size were, therefore, analysed by plotting numerical abundance against mean grain size. There were at least four patterns: species groups could be associated with finegrained sediments, those of intermediate size and coarser sediments and the last group showed no discernible pattern.     

Processes involved in uptake and release of nitrogen dioxide from soil and building stones into the atmosphere

Atmospheric NO₂ was taken up by samples of various soils and building stones. The NO₂ uptake rate constants were highest in soil samples taken during the summer months. However, the NO₂ uptake rate constants of the soils and building stones were not significantly correlated with any of the following variables: moisture, pH, ammonium, nitrite, or nitrate. NO₂ uptake by soil and stone was not abolished by autoclaving indicating a chemical uptake process. NO₂ uptake by acidic and air-dry soils and stones resulted in nearly stoichiometric reduction of NO₂ to NO. This reduction was enhanced by the addition of ferrous iron and was further enhanced by incubation under 1 ppmv SO₂. The results suggest that NO₂ reduction may be coupled to oxidation of ferrous to ferric iron which may be reduced again by atmospheric SO₂ thus regenerating the ferrous iron content of the soil or stone. Conversion of NO₂ to NO was not observed in neutral or/and moist soils and stones. NO₂ was also taken up by purified and sterilized quartz sand moistend with water. This uptake was enhanced by addition of humic material but not by addition of bacteria which both had been extracted from genuine soil. Under most conditions, only uptake but no release of NO₂ was observed. However, NO₂ was released in air-dry soils that were heated to 45–65°C, or in ammonium-fertilized soil or stone that was drying up at room temperature. Under the latter conditions mimicking field practice, the NO₂ release reached rates that were similar to the NO release rates.     

Sublittoral epifaunal communities at Signy Island,Antarctica. I. The ice-foot zone

Photographs were taken every 0.5 m along three transects of 5.5 m length on shallow rock faces at Signy Island, Antarctica, during the austral summer of 1991/1992. The percentage cover of substratum ranged from 0 to 100% and the colonising communities included representatives of ten phyla. The zone from mean low-water neap level to 1.5 m depth was mostly devoid of organisms as a result of the seasonal formation of the encrusting ice foot. Coralline and macroalgae dominated from 2 to 3 m, and animal groups from 3.5 to 5.5 m. Bryozoans, and to a lesser extent sponges, were the most abundant animal phyla. Within the bryozoans a succession of colonisation of different species was observed, the most abundant two of which occupied >80% of substratum in places. Substratum type seemed to be the main factor influencing community development in the shallow sublittoral at Signy Island, although ice impact prevents community development in the top 1.5 m and limits it over the rest of the transect down to 5.5 m. Depth and profile of substratum also influenced communities within this depth range (particularly taxonomic composition).     

ARSENIC CONSUMPTION AND HEALTH RISK PERCEPTIONS IN A RURAL WESTERN U.S. AREA1

ABSTRACT: Churchill County, Nevada, has approximately 23,000 residents, among whom an estimated 13,500 relied on private wells for water supply in 2002. This study examined exposure to arsenic in water supplies among residents with private domestic wells and factors related to householder choice to consume tap water. It compared opinions and concerns about water quality with consumption habits and observed concentrations from tap water samples. The results from 351 households indicated that a majority (75 percent) of respondents consumed tap water and that a minority (38 percent) applied treatment. Approximately 66 percent of those who consumed tap water were exposed to concentrations of arsenic that exceeded 10 ppb. Water consumption was related to application of treatment. Among 98 respondents who were not at all concerned about the health effects of aqueous arsenic, 59 (60 percent) reported consuming tap water with concentrations of arsenic exceeding 10 ppb. Conversely, among 86 respondents who were highly concerned about arsenic, 33 (37 percent) consumed tap water with concentrations of arsenic exceeding 10 ppb. Results from a national sampling effort showed that 620 of 5,304 private wells sampled (11.7 percent) had arsenic concentrations above 10 ppb. The paradox of awareness of arsenic in water supplies coupled with consumption of aqueous arsenic in concentrations greater than 10 ppb may be common in other parts of the nation. Enhanced educational efforts, especially related to tap water sampling and explanations of efficacy of available treatment, may be useful means of reducing exposure through private water supplies.