Reducing the environmental impact of coal-washing practice in Australia

All Australian coal for export is washed — that is, the low-grade high-ash material is separated out and disposed of at the washery site. The coarse rejects are generally placed in embankments and the tailings are pumped into settling ponds. These methods of waste disposal can create environmental problems. In addition, they represent a significant energy loss, because about one-third of the waste material is combustible and is thus a potentially valuable source of energy. Laboratory studies at the CSIRO Division of Fossil Fuels at North Ryde, New South Wales, have shown that energy can be successfully recovered from washery wastes by the process of fluidized-bed combustion. A pilot fluidized-bed combustor, with a capacity of 2 tonnes/hour, is undergoing prolonged trial at the Clutha washery near Camden, New South Wales, in a joint project between the Joint Coal Board and CSIRO. The results from the pilot plant tests have provided the basis for a conceptual design and feasibility study for a full-scale tailings treatment plant. This study has indicated that fluidized-bed combustion:

1. offers an environmentally attractive and economically competitive alternative to the disposal of tailings in settling ponds, and
2. can be used to generate large quantities of energy from the wastes, reducing the energy lost in coal washing from around 16% to 6% of the coal mined.

     

Demography of <Emphasis Type="Italic">Nebalia</Emphasis> sp. (Crustacea: Leptostraca) determined by carrion bait trapping in Lobster Bay,Cape d‘Aguilar Marine Reserve,Hong Kong

The feeding ecology of leptostracans is not well-known. In the present study, species of Nebalia (Crustacea: Leptostraca) were captured every month for 1 year from Lobster Bay, Hong Kong, using baited traps. Captured individuals fell into a size range of 0.36–3.64 mm and 0.95–5.52 mm in carapace and total lengths, respectively. They were divided into different reproductive stages based on the morphology of the second pair of antennae and thoracopods. Sexual dimorphism becomes apparent between 0.7–1.5 mm (CL) and 1.4–3.2 mm (TL). Most individuals collected were sexually differentiated, but immature (79.7% of the captured individuals), followed by post-ovigerous (11.4%) and ovigerous (8.9%) females. Sexually undifferentiated juveniles were rare (3.9%). The sex ratio of the immature individuals approached 1:1 with a propensity towards male dominance. Not one mature male was captured. Although females with setose thoracopod endopods, indicating that they were ovigerous, were captured frequently, only two were carrying eggs. The two brooding females had clutch sizes of 11 and 17 eggs. Alternate peaks in relative abundance of ovigerous and post-ovigerous females were identified, the latter following the former. Reproductive activities occurred mainly in April–May and October–December, indicating that two cohorts are recruited. Catches using baited traps could be explained by the reproductive season of Nebalia sp. High catches were usually associated with the months of highest reproductive activity, low catches with peaks in post-ovigerous females. It is therefore concluded that not all individuals at various reproductive stages are attracted to carrion and hence adopt a scavenging feeding mode. Catches of Nebalia sp. in Hong Kong possibly reflect their annual cycle of reproductive activity     

Nitrates and gastric carcinogenesis

Nitrate, acting as a precursor in the formation of carcinogenicN-nitroso compounds, may be implicated in human digestive tract cancers. This study compares nitrate levels in drinking water with subsequent gastric cancer mortality in Kent, south-east England. The data suggest that water nitrate cannot be excluded as an aetiological factor, although other environmental variables must also be considered.     

Soil and plant concentrations of cadmium and zinc in the vicinity of a smelter

Cadmium, zinc and lead concentrations in soils and plants near a smelter at Avonmouth are reported for samples collected in May 1979 and in May 1980. The total metal soil concentrations fall as distance from the smelter increases and decrease rapidly with depth for cadmium and zinc. The concentrations of these two metals are highly correlated at all depths. Near the smelter, where the carbon content and pH values of the soils are lowest, almost all the cadmium, as measured by EDTA extraction, is available. Concentration of metals in plants also decrease with distance from the smelter, with concentrations being lower in samples collected in 1980. This is possibly due to a seasonal variation in biomass, producing a dilution effect. We conclude that uptake of cadmium and that of zinc by grass species have different relationships to the carbon content of the soil.     

Environmental aspects of mineral sand mining in Australia

The operations of the heavy mineral sand mining industry in Australia are reviewed, with particular emphasis on the environmental aspects. Pre-mining environments, state and commonwealth legislative requirements, mining procedures and postmining rehabilitation and land use are described. The extraction of heavy minerals, principally rutile, zircon, ilmenite and monazite, is concentrated on the east coast between the Hawkesbury River in New South Wales and Rockhampton in Queensland; and on the west coast at Capel, south of Perth and at Eneabba, north of Perth. The industry, especially on the east coast, has suffered from conservationist and anti-mining movements during the 1970s because it operates on or near the coastline where the majority of Australians live or seek their recreation. This was less of a problem on the west coast because the deposits were inland. The future of the industry is good as long as a balance can be maintained between the interests of conservationists and the mining companies.     

Disaggregated intertemporal models with an exhaustible resource and technical advance

We compare results of four organizations of an economy that is dependent upon an irreplenishable resource but may develop a new technology that releases that dependence. We find a decentralized competitive organization can replicate the behavior of a centrally planned economy, given an appropriate distribution of initial wealth. This holds whether the R&D is done by the government or by the natural resource sector, so long as borrowing from other sectors is possible. Further, the economy's behavior is independent of whether the resource sector is monopolistic or competitive if and only if the production function is Cobb-Douglas.     

The role of distance,familiarity, and time of day in Carolina wrens responses to conspecific songs

Summary We tested two predictions of the ranging hypothesis (Morton 1982) which suggests that: (1) For distance estimation of singing intruders from them, birds compare degraded songs they hear to undegraded songs in their memory. (2) The strength of response of birds to songs depends on how well they can range the songs as coming from inside or outside the territory.In accordance with first prediction we found that, Carolina wrens discriminate significantly between songs played from outside to those played inside their territories only if they are familliar with the song type played (Fig. 1). In accordance with the second prediction, on the average, the birds in our study responded stronger to unfamiliar than to familiar songs when these were played from outside the territory, but stronger to familiar than to unfamiliar songs when played inside it (Fig. 2). We concluded that this was because they could range the familiar songs with greater certainty.The variance in the data was, in part, due to changes in the birds' responses during the day. We report for the first time, an increase in the strength of territorial defense of birds later in the morning, accompanied by a decrease in singing in response to song playback. We suggest that these changes reflect an increase in energy gain and worse acoustic conditions later in the day.     

Anaerobic biodegradation of alkylbenzenes and trichloroethylene in aquifer sediment down gradient of a sanitary landfill

The objective of this investigation was to evaluate the anaerobic biodegradability of benzene, toluene, ethylbenzene, ortho-, meta- and para-xylene (BTEX) and trichloroethylene (TCE) in aquifer sediment down gradient of an unlined landfill. The major organic contaminants identified in the shallow unconfined aquifer are cis-dichloroethylene (c-DCE) and toluene. The biodegradative potential of the contaminated aquifer was measured in three sets of microcosms constructed using anaerobic aquifer sediment from three boreholes down gradient of the landfill. The degradability of BTEX and TCE was examined under ambient and amended conditions. TCE was degraded in microcosms with aquifer material from all three boreholes. Toluene biodegradation was inconsistent, exhibiting biodegradation with no lag in one set of microcosms but more limited biodegradation in two additional sets of microcosms. TCE exhibited an inhibitory effect on toluene degradation at one location. The addition of calcium carbonate stimulated TCE biodegradation which was not further stimulated by nutrient addition. TCE was converted to ethylene, a harmless byproduct, in all tests. Benzene, ethylbenzene and xylene isomers were recalcitrant in both ambient and amendment experiments. Biodegradation occurred under methanogenic conditions as methane was produced in all experiments. Bromoethane sulfonic acid (BES), a methanogenic inhibitor, inhibited methane and ethylene production and TCE biodegradation. The results indicate the potential for intrinsic bioremediation of TCE and toluene down gradient of the Wilder's Grove, North Carolina, landfill. The low concentrations of TCE in monitoring wells was consistent with its biodegradation in laboratory microcosms.     

Prenatal diagnosis of turner syndrome using cells cultured from cystic hygromas in two pregnancies with normal maternal serum alpha-fetoprotein

In two cases of prenatally detected cystic hygroma with oligohydraminos, successful cytogenetic diagnosis of Turner syndrome was achieved using cells obtained from direct aspiration of the cystic hygroma. Exceptionally high levels of alpha-fetoprotein were found in the cystic hygroma fluid, as might be expected. However, the maternal serum alpha-fetoprotein levels were within normal limits. Elevated alpha-fetoprotein levels in ‘amniotic fluid’ noted previously in the literature may have resulted because of inadvertent tapping of the cystic hygroma. It is clear from our cases that maternal serum levels of alpha-fetoprotein will not necessarily be elevated and will not serve as a screening mechanism for cystic hygromas.     

Correlation between phenotypic expression of de novo marker chromosomes and genomic organization using replicational banding

It has been suggested that actively expressed genes are primarily located in early replicating bands. This hypothesis is supported by cytogenetic and pregnancy outcome data from four consecutive cases of prenatally detected de novo marker chromosomes. Two fetuses with major anomalies had large early replicating bands, while the marker in a third phenotypically normal fetus was late replicating. In the fourth case, a ring marker chromosome had only a small early replicating region. Pregnancy termination was elected. While no structural malformations were apparent, potential intellectual function in this case remains unresolved. An understanding of the relationship between genomic organization and chromosome banding is critical in counseling for prenatally detected de novo marker chromosomes. Replicational banding is particularly helpful in recognizing genes that may be actively expressed and result in developmental abnormality.