Soil washing for volume reduction of radioactively contaminated soils

The Office of Radiation and Indoor Air of the U.S. Environmental Protection Agency has demonstrated a soil washing plant for the treatment of radioactively contaminated soils from two Superfund sites in New Jersey. The plant employs unit operations that are widely used in the processing of minerals and coal. These operations were examined and tested to determine how they would apply to volume reduction of these contaminated soils. In this context, they are considered to be innovative candidates for remediation of other sites with large volumes of soil contaminated with low-level radioactivity. Laboratory testing of soil characteristics and behavior in unit processes is used to assess the applicability of volume reduction/chemical extraction (VORCE) technology to specific sites.     

Northeastward reverse migration of birds over Nova Scotia,Canada, in autumn

Summary During 4 seasons of study, small numbers of birds flew overland to the NNE-E, counter to the main SW migration, intermittently throughout the autumn (31 July – 16 November). Radars also detected overwater reverse migration (RM) from New England to Nova Scotia and from Nova Scotia toward Newfoundland. RM occurred at all hours of the day and night, especially when few birds were migrating SW. Most but not all cases of RM occurred with following SW winds. RM was more common with cloud and/or poor visibility than in fair weather, but was not restricted to cloudy occasions. Mean tracks were correlated with wind direction, but were not consistently downwind. Tracks tended to be closer to downwind in early than in late autumn, and on clear than on overcast nights. Dispersion in tracks was not discernibly related to weather variables, time of day or night, or magnetic disturbance. Eleven hypotheses concerning the reasons for reverse migration in autumn are evaluated; cases of RM recorded in this study are attributable to at least three of these hypotheses (late summer dispersal, hurricanes, dawn reorientation toward coast) and possibly to several others.     

International competitive displacement from environmental control The quantitative gains from methodological refinement

This paper demonstrates empirically the gain from adopting more general equilibrium approaches in projecting the effects on domestic output and international trade of environmental controls. The suggested models include a partial equilibrium case where all industries are treated independently, an intermediate case incorporating effects in supplying industries, and general equilibrium formulations based on alternative macroeconomic conditions. U. S. data is used to evaluate these models. Under both pollutor pays and subsidy financing schemes, moving from the simplest case to the intermediate model results in quite different industry projections. Including macroeconomic factors appears particularly important in the classical setting.     

Sampling Benthic Macroinvertebrates in a Large Flood-Plain River: Considerations of Study Design, Sample Size, and Cost

Estimation of benthic macroinvertebrate populations over large spatial scales is difficult due to the high variability in abundance and the cost of sample processing and taxonomic analysis. To determine a cost-effective, statistically powerful sample design, we conducted an exploratory study of the spatial variation of benthic macroinvertebrates in a 37 km reach of the Upper Mississippi River. We sampled benthos at 36 sites within each of two strata, contiguous backwater and channel border. Three standard ponar (525 cm²) grab samples were obtained at each site ('Original Design'). Analysis of variance and sampling cost of strata-wide estimates for abundance of Oligochaeta, Chironomidae, and total invertebrates showed that only one ponar sample per site ('Reduced Design') yielded essentially the same abundance estimates as the Original Design, while reducing the overall cost by 63%. A posteriori statistical power analysis ( = 0.05, = 0.20) on the Reduced Design estimated that at least 18 sites per stratum were needed to detect differences in mean abundance between contiguous backwater and channel border areas for Oligochaeta, Chironomidae, and total invertebrates. Statistical power was nearly identical for the three taxonomic groups. The abundances of several taxa of concern (e.g., Hexagenia mayflies and Musculium fingernail clams) were too spatially variable to estimate power with our method. Resampling simulations indicated that to achieve adequate sampling precision for Oligochaeta, at least 36 sample sites per stratum would be required, whereas a sampling precision of 0.2 would not be attained with any sample size for Hexagenia in channel border areas, or Chironomidae and Musculium in both strata given the variance structure of the original samples. Community-wide diversity indices (Brillouin and 1-Simpsons) increased as sample area per site increased. The backwater area had higher diversity than the channel border area. The number of sampling sites required to sample benthic macroinvertebrates during our sampling period depended on the study objective and ranged from 18 to more than 40 sites per stratum. No single sampling regime would efficiently and adequately sample all components of the macroinvertebrate community.     

Radio tagging reveals the roles of corpulence,experience and social information in ant decision making

Ant colonies are factories within fortresses (Oster and Wilson 1978). They run on resources foraged from an outside world fraught with danger. On what basis do individual ants decide to leave the safety of the nest? We investigated the relative roles of social information (returning nestmates), individual experience and physiology (lipid stores/corpulence) in predicting which ants leave the nest and when. We monitored Temnothorax albipennis workers individually using passive radio-frequency identification technology, a novel procedure as applied to ants. This method allowed the matching of individual corpulence measurements to activity patterns of large numbers of individuals over several days. Social information and physiology are both good predictors of when an ant leaves the nest. Positive feedback from social information causes bouts of activity at the colony level. When certain social information is removed from the system by preventing ants returning, physiology best predicts which ants leave the nest and when. Individual experience is strongly related to physiology. A small number of lean individuals are responsible for most external trips. An individual’s nutrient status could be a useful cue in division of labour, especially when public information from other ants is unavailable.     

The Economic Consequences of Alien Plant Invasions: Examples of Impacts and Approaches to Sustainable Management in South Africa

The invasion of natural ecosystems by alien plants is a serious environmental problem that threatens the sustainable use of benefits derived from such ecosytems. Most past studies in this field have focussed on the history, ecology and management of invasive alien species, and little work has been done on the economic aspects and consequences of invasions. This paper reviews what is known of the economic consequences of alien plant invasions in South Africa. These economic arguments have been used to successfully launch the largest environmental management programme in Africa.Ten million hectares of South Africa has been invaded by 180 alien species, but their impacts are not fully understood, although they are undoubtedly significant. The indications are that the total costs of these impacts are substantial. Selected studies show that invasions have reduced the value of fynbos ecosystems by over US$ 11.75 billion; that the total cost of invasion would be about US$ 3.2 billion on the Agulhas Plain alone; that the net present cost of invasion by black wattles amounts to US$ 1.4 billion; that invasions by red water fern have cost US$ 58 million; and that the cost to clear the alien plant invasions in South Africa is around US$ 1.2 billion. These few examples indicate that the economic consequences of invasions are huge.One of the unique aspects of invasive plant control programmes in South Africa has been the ability to leverage further benefits (mainly through employment) for the expensive control programmes from the government's poverty relief budget. This has made it possible to allocate substantial funding to a programme that would otherwise have struggled to obtain significant support. Biological control of invasive species also offers considerable benefits, but is often the subject of debate. We believe that, at least in the case of many invasive alien plant species in South Africa, biological control offers one of the best, and most cost-effective, interventions for addressing the problem.     

Population structure and growth of Donax trunculus (Bivalvia: Donacidae) in the western Mediterranean

A comparison of shell growth in Donax trunculus (collected between 1988 and 1990 of Cullera, Spain) has been carried out using an analysis of cohort progression in monthly length frequency distributions, hyaline surface shell growth rings and internal microgrowth bands. In the Mediterranean there are two periods of recruitment of D. trunculus, one in the summer (July to September) and the other in winter (December to February). Clams recruited to the population in winter display a clear cessation in shell growth during the following summer which may possibly be correlated with spawning, whereas individuals of the summer recruited cohort show no growth cessation the following summer and continue to deposit shell during this period. The normally opaque shell of D.trunculus reveals the presence of translucent hyaline growth rings when the shells are backlit by a strong light source, and these have been shown to be laid down in the shell during summer months. Formation of a hyaline ring is accompanied by a narrowing of the microgrowth patterns present in shell sections. Both the hyaline rings and the length frequency distributions have been used to determine the age and growth rate of D. trunculus.     

Ecological genetics of the barnacle,<Emphasis Type="Italic"> Hexaminius foliorum</Emphasis>, within mangrove forests near Sydney,Australia

Spatial and temporal distribution of allozyme variation at three loci in a cohort of the barnacle, Hexaminius foliorum, living on leaves of Avicennia marina was studied from recruitment to adulthood at three geographical scales. Analysis of populations shortly after recruitment showed that there were significant divergences in allele frequencies at the coarsest geographical scale studied (between estuaries, 50 km apart, Wright's F statistic=0.016) and at the finest geographic scale (between sites, 50–100 m apart, Wright's F statistic=0.018). There was, however, no significant genetic divergence at an intermediate scale (between bays, 3–4 km apart, Wright's F statistic=0.002). The genetic differences between populations decreased over time due to the selection against the null homozygotes originally present at high frequency at two loci. There was sufficient mortality (ranging from 35.5 to 80%) between seasons to account for the deaths needed for the observed changes in allele frequencies. Differences in the genetic structure between estuaries may be the result of isolation and limited mixing of cyprid larvae among estuaries. Differences in the genetic structure between sites may be due to pre- and post-settlement mortality acting on H. foliorum.Communicated by G.F. Humphrey, Sydney     

Petroleum hydrocarbons and polycyclic aromatic hydrocarbons in the surficial sediments of Xiamen Harbour and Yuan Dan Lake, China

Surficial sediments were sampled from nine stations in Xiamen Harbour and two stations in Yuan Dan Lake during April 2002. Sediment samples were extracted by organic solvents, separated by silica gel column chromatography and analyzed by gas chromatography-mass selective detector (GC-MSD). Selected ion monitoring was at M/Z=57 for petroleum hydrocarbons (PHCs) and individual M/Zs for each of the 15 typical polycyclic aromatic hydrocarbons (PAHs) and nine alkylated PAHs. The results showed that concentrations of PHCs and total PAHs in the sediments of Yuan Dan Lake were 1397 microg g(-1) (dry weight, dw) and 1377 ng g(-1) (dw), respectively. The ranges for PHCs and total PAHs in the sediments from Xiamen Harbour were 133-943 microg g(-1) (dw) and 98-309 ng g(-1) (dw), respectively. Shipping activities, industrial wastewater discharges, fuel oil spillage from ships and vehicles were the main sources of PHCs and PAHs in the Harbour. In addition, the widespread use of coal for industrial processes and domestic consumption accounted for the second largest source of PAHs in the sediments, while atmospheric transport and deposition of PAHs are also important.