Bioavailability of biosolids molybdenum to soybean grain

Legumes grown in biosolids-amended soils and then fed to ruminants can represent problematic sources of molybdenum (Mo), but few field data are available to quantify the risk. We used a set of fields amended to high cumulative biosolids Mo loads (>18 kg ha(-1)) over 27 yr to generate additional data. Soybean [Glycine max (L.) Merr.] was grown on 29 fields (pH values>6.8) amended to a wide range of soil Mo loads. Soybean grain harvested from each field was analyzed for Mo and the concentrations regressed against soil Mo loads estimated from actual soil Mo concentrations in the 0- to 15-cm depth. Slopes of such linear regressions represent uptake coefficients (UC values) used by the USEPA to assess risk of biosolids Mo to ruminants fed forage grown on biosolids-amended land. The UC value for all 29 fields was estimated as 1.66, which agrees with the few soybean grain data in the literature. The UC value, however, is well below a conservative UC value of 4, recently recommended for all fresh legume materials fed to cattle. Soybean grain can contain high concentrations of Mo (>10 mg kg(-1)) and have low (<2:1) Cu to Mo ratios, which can exacerbate molybdenosis problems in cattle. However, soybean grain normally constitutes only -10% of dairy cattle diet, and other constituents (e.g., corn grain, stover, mineral supplements) are sufficient, or can be manipulated, to control molybdenosis.     

The consequences of tourism for sustainable water use on a tropical island: Zanzibar, Tanzania

Many developing countries in the tropics have focused on tourism to generate additional income sources and to diversity the economy. Coastlines in particular have been on the forefront of tourist infrastructure development. Here, the presence of a large number of tourists has often had negative consequences for the sustainable use of the available resources, which in turn has had an effect on the integrity of the ecosystems. In this paper, the situation is described for the use of freshwater resources on the east coast of Zanzibar, Tanzania. This region is water poor, relying on freshwater derived from seasonal rains and stored in less efficient aquifers, which consist of freshwater lenses floating on the underlying seawater. Tourism in the area has grown rapidly in recent years and is expected to further increase in the future. This development is expected to put additional pressure on the freshwater resources of the east coast, which show already signs of over-use. The consequences of overexploitation can include the lowering of the groundwater table, land subsidence, deteriorating groundwater quality, and saltwater intrusion. These, in turn, determine the living conditions in coastal areas and the effects will be felt both by the local populations and the tourist industry. An investigation is made into the causes and consequences of water abstraction by the tourist industry. The results show that present levels of withdrawal are not sustainable, and parts of the local populations are already experiencing water deficits on a daily basis. In the future, if the expected increase in tourist numbers occurs, the pressure on the aquifers will correspondingly increase. The results could be that the tourism in the area becomes unsustainable, which could have an adverse effect on the national economy and also on the local population and environment. Therefore, a precautionary water-management approach is suggested.     

Ecological impacts of arable intensification in Europe

Although arable landscapes have a long history, environmental problems have accelerated in recent decades. The effects of these changes are usually externalized, being greater for society as a whole than for the farms on which they operate, and incentives to correct them are therefore largely lacking. Arable landscapes are valued by society beyond the farming community, but increased mechanization and farm size, simplification of crop rotations, and loss of non-crop features, have led to a reduction in landscape diversity. Low intensity arable systems have evolved a characteristic and diverse fauna and flora, but development of high input, simplified arable systems has been associated with a decline in biodiversity. Arable intensification has resulted in loss of non-crop habitats and simplification of plant and animal communities within crops, with consequent disruption to food chains and declines in many farmland species. Abandonment of arable management has also led to the replacement of such wildlife with more common and widespread species. Soils have deteriorated as a result of erosion, compaction, loss of organic matter and contamination with pesticides, and in some areas, heavy metals. Impacts on water are closely related to those on soils as nutrient and pesticide pollution of water results from surface runoff and subsurface flow, often associated with soil particles, which themselves have economic and ecological impacts. Nitrates and some pesticides also enter groundwater following leaching from arable land. Greatest impacts are associated with simplified, high input arable systems. Intensification of arable farming has been associated with pollution of air by pesticides, NO2 and CO2, while the loss of soil organic matter has reduced the system's capacity for carbon sequestration. International trade contributes to global climate change through long distance transport of arable inputs and products. The EU Rural Development Regulation (1257/99) provides an opportunity to implement measures for alleviating ecological impacts of arable management through a combination of cross-compliance and agri-environment schemes. To alleviate the problems described in this paper, such measures should take account of opportunities for public/private partnerships and should integrate social, cultural, economic and ecological objectives for multifunctional land use.     

Testing hypotheses about management to enhance habitat for feeding birds in a freshwater wetland

The level of water was manipulated in a freshwater wetland, with the aim of enhancing abundances of benthic animals and, ultimately, improving habitat for feeding birds (Japanese Snipe, Gallinago hardwickii). We tested whether these actions had the predicted and desired effects on benthic animals, by contrasting changes in two managed locations to one control location which was left unmanipulated. The number of taxa and abundances of chironomids decreased strongly and significantly in the manipulated locations, while the abundance of oligochaetes appeared to vary in a seasonal manner. Temporal variability of the structure and composition of assemblages was also increased in manipulated locations. Such effects have previously been suggested to indicate stress in benthic assemblages. Therefore, in contrast to what was predicted, managerial actions made benthic fauna less abundant and thus, less suitable as habitat for feeding birds. Several general lessons can be learned from these results. (1) Effects of managerial actions like these are difficult to predict a priori and can only be reliably evaluated with an experimental framework. (2) Because abundances of animals vary naturally, evaluations of managerial actions must include appropriate spatial replication. (3) Sampling at hierarchical temporal scales is important, because abundances of animals may vary in an unpredictable manner at short temporal scales and because changes in temporal variability may be a symptom of stress. (4) Combined use of uni- and multivariate techniques provides a comprehensive set of tools to assess the effects of restoration and creation of new habitats. Finally, these results emphasise the need for clear predictions about desired outcomes and specific experimental plans about how to test whether the desired results were achieved, before managerial actions are taken. Although this is often very difficult to achieve in real situations, it is necessary for practices of management to evolve on the basis of sound empirical experience.     

Critical remarks on the use of terrestrial moss (Hylocomium splendens and Pleurozium schreberi) for monitoring of airborne pollution

Duplicate samples of the two terrestrial moss species Hylocomium splendens and Pleurozium schreberi, which are widely used to monitor airborne heavy metal pollution, have been collected from eight catchments spread over a 1,500,000 km2 area in northern Europe. These were analysed for a total of 38 elements by inductively coupled plasma-mass spectrometry, inductively coupled plasma-atomic emission spectrometry and cold vapour-atomic absorption spectometry techniques. Results show that the moss species can be combined without interspecies calibration for regional mapping purposes. For the majority of elements the observed within-catchment variation is large--big composite samples over a large area should thus be collected when moss is to be used for monitoring purposes. For the majority of elements the input of dust governs moss chemistry. For a reliable 'contamination' signal over a sizeable area a major source is needed. Some elements show a dependence on climate/vegetation zone. In coastal areas the input of marine aerosols will alter the chemical signal obtained from moss samples.     

Patterns of nitrogenous waste excretion and gill urea transporter mRNA expression in several species of marine fish

Many prior studies of nitrogenous waste excretion in marine fish have examined excretion patterns for short time periods, and with relatively coarse sampling schemes (e.g., an initial and a final sample point). Recent studies of a ureotelic marine fish (the gulf toadfish, Opsanus beta) have demonstrated that urea excretion in this species occurs in brief but massive bursts, lasting from 0.5 to 3 h, and often only once per day. The present study sought to determine if prior sampling protocols may have underestimated the amount of urea being excreted by marine fish. A survey of 16 marine species (the teleosts: Myoxocephalus octodecemspinosus, Scophthalamus aquosa, Cyclopterus lumpus, Lophius americanus, Aprodon cortezianus, Cymatogaster aggregatus, Parophrys vetulis, Microstomus pacificus, Hippoglossoides elassodon, Bathyagonus nigripinnus, Ophiodon elongatus, Hemilepidatus spinosus, Icelinus terrius; the elasmobranch: Raja rhina; and the hagfish: Eptatretus stoutii) was undertaken for ammonia-N and urea-N excretion using a long sampling period (48 h) and hourly sample collection. Apart from the obvious exception of an elasmobranch, ammonia excretion was confirmed to be predominant in marine fish, with urea excretion constituting between 1.4 and 23.8% of the total of ammonia plus urea excreted. Notably, no pulses of urea excretion were detected. Despite the relatively low level of urea excretion, expression of urea transporter-like mRNA (detected using the toadfish urea transporter, tUT, cDNA as a probe) was discovered in gills of many of the species surveyed for nitrogen excretion patterns, although no signal was detected in the hagfish. These results suggest that urea excretion takes place through a specific transport pathway. Finally, more detailed analysis of nitrogen excretion in one of the surveyed species, the plainfin midshipman (Porichthys notatus) demonstrates that "total" nitrogen excretion estimated by summing ammonia and urea excretion underestimates true total nitrogen excretion by 37-51%.     

Radionuclide fluxes at a plant manufacturing dicalcium phosphate for domestic animals

We have studied a phosphate rock plant which produces dicalcium phosphate (DCP), used as a source of calcium and phosphorus for domestic animals. A by-product in the manufacturing process is calcium chloride which is used in the oil industry, the food industry and as road-salt. The objectives of our study were to describe the fluxes of radionuclides from the 238U decay series and to estimate the radiation doses to workers at the plant. The radionuclides in the phosphate rock were found to be in secular radioactive equilibrium with 238U, with an average activity concentration of 837 Bq kg-1. Separation and concentration processes were observed at different stages in the plant. Most of the 226Ra was found in the calcium chloride, while the major part of the 238U, about 950 Bq kg-1, was found in the dicalcium phosphate. The annual occupational effective dose to the workers was found to be below the 1 mSv limit recommended by ICRP (1991a) for the public. This study has shown a good example of an important non-nuclear industry with a high input of natural radionuclides with several conceivable pathways to man.     

Improvements in modeling sagebrush concentrations of radioiodine released from the Hanford site

The Hanford Environmental Dose Reconstruction Project estimated the radiation dose to individuals from historical emissions of radioactive materials from the Hanford Site in Washington State. Project validation studies using predicted activity concentrations of 131I on sagebrush (Artemisia tridentata) showed a systematic underestimation against historical data during cold weather months, indicating a need for sagebrush model improvement. A deposition model for semi-volatile organic materials presented by Komp and McLachlen (Environ. Sci. Tech. 31 (1997) 886-890) is adapted here for gaseous iodine onto sagebrush. The deposition model includes a temperature-dependent term based on an integrated van't Hoff equation. Calibration data for the model are obtained from a release of 131I in 1963. Modeling results for releases in 1946 show a good match between historical data and predicted results using the new model. The new model shows improvement over interception-fraction type models, but requires plant-type-specific calibration data.     

Airborne surveys of Swiss nuclear facility sites

Annually since 1989, biannually since 1994, the environs (approximately 50 km2) of the Swiss nuclear facilities are surveyed (by helicopters) flying the same survey lines. The equipment and the data processing software used for these surveys were built and developed at the Institute of Geophysics, ETH Zurich. For mapping of man-made radiation at or around nuclear facility sites a pixel representation and the MMGC (man-made gross count) ratio is used. So far no artificial radioactivity that could not be explained by the Chernobyl event (1986) or by earlier nuclear weapon tests was detected outside the fenced sites of the nuclear facilities.