49 research outputs found
A new method to constrain the appearance and disappearance of observed jellyfish galaxy tails
Galaxie
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Assessing inhalation exposure from airborne soil contaminants
A method of estimation of inhalation exposure to airborne soil contaminants is presented. this method is derived from studies of airborne soil particles with radioactive tags. The concentration of contaminants in air (g/m{sup 3}) can be derived from the product of M, the suspended respirable dust mass concentration (g/m{sup 3}), S, the concentration of contaminant in the soil (g/g), and E{sub f}, an enhancement factor. Typical measurement methods and values of M, and E{sub f} are given along with highlights of experiences with this method
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Protocols of radiocontaminant air monitoring for inhalation exposure estimates
Monitoring the plutonium and americium particle emissions from soils contaminated during atmospheric nuclear testing or due to accidental releases is important for several reasons. First, it is important to quantify the extent of potential human exposure from inhalation of alpha-emitting particles, which is the major exposure pathway from transuranic radionuclides. Second, the information provided by resuspension monitoring is the basis of criteria that determine the target soil concentrations for management and cleanup of contaminated soil sites. There are other radioactive aerosols, such as the fission products (cesium and strontium) and neutron-activation products (europium isotopes), which may be resuspended and therefore necessary to monitor as well. This Standard Protocol (SP) provides the method used for radiocontaminant air monitoring by the Health and Ecological Assessment Division (formerly Environmental Sciences Division), Lawrence Livermore National Laboratory, as developed and tested at Nevada Test Site (NTS) and in the Marshall Islands. The objective of this SP is to document the applications and methods of monitoring of all the relevant variables. This protocol deals only with measuring air concentrations of radionuclides and total suspended particulates (TSP, or {open_quotes}dust{close_quotes}). A separate protocol presents the more difficult measurements required to determine transuranic aerosol emission rates, or {open_quotes}resuspension rate{close_quotes}
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Potential effects of geothermal energy conversion on Imperial Valley ecosystems. [Seven workshop presentations]
This workshop on potential effcts of geothermal energy conversion on the ecology of Imperial Valley brought together personnel of Lawrence Livermore Laboratory and many collaborators under the sponsorship of the ERDA Imperial Valley Environmental Project (IVEP). The LLL Integrated Assessment Team identified the electric power potential and its associated effluents, discharges, subsidence, water requirements, land use, and noise. The Working Groups addressed the ecological problems. Water resource management problems include forces on water use, irrigation methods and water use for crops, water production, and water allocation. Agricultural problems are the contamination of edible crops and the reclamation of soil. A strategy is discussed for predevelopment baseline data and for identification of source term tracers. Wildlife resources might be threatened by habitat destruction, powerline impacts, noise and disturbance effects, gas emissions, and secondary impacts such as population pressure. Aquatic ecosystems in both the Salton Sea and fresh waters have potential hazards of salinity and trace metal effects, as well as existing stresses; baseline and bioassay studies are discussed. Problems from air pollution resulting from geothermal resource development might occur, particularly to vegetation and pollinator insects. Conversion of injury data to predicted economic damage isneeded. Finally, Imperial Valley desert ecosystems might be threatened by destruction of habitat and the possible effects on community structure such as those resulting from brine spills
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Plutonium-aerosol emission rates and human pulmonary deposition calculations for Nuclear Site 201, Nevada Test Site
This study determined the plutonium-aerosol fluxes from the soil to quantify (1) the extent of potential human exposure by deep-lung retention of alpha-emitting particles; (2) the source term should there be any significant, long-term, transport of plutonium aerosols; and (3) the resuspension factor and rate so that, for the first time at any nuclear site, one may calculate how long it will take for wind erosion to carry away a significant amount of the contaminated soil. High-volume air samplers and cascade impactors were used to characterize the plutonium aerosols. Meteorological flux-profile methods were used to calculate dust and plutonium aerosol emission rates. A floorless wind tunnel (10-m long) was used to examine resuspension under steady-state, high wind speed. The resuspension factor was two orders of magnitude lower than the other comparable sites at NTS and elsewhere, and the average resuspension rate of 5.3 x 10/sup -8//d was also very low, so that the half-time for resuspension by wind erosion was about 36,000 y
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Fast response light scattering measurements of the characteristics of wind suspended aerosols
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A test of resuspension factor models against Chernobyl data
After the accident at Unit 4 of the Chernobyl nuclear power plant (NPP), stationary air samplers were operated at Chernobyl and Baryshevka, cities which are 16 km and 150 km, respectively, from the NPP. Other air samplers were operated simultaneously, but intermittently, at locations within the 30 km zone at distances of 4-25 km from the NPP. These data were used to check the validity of time dependent models of the resuspension factor K (m{sup -1}). Seven different models were examined, three of which are discussed in the paper. Data from the stationary air samplers were averaged over one day or one month; dam from the intermittent air samplers were averaged over three days in 1986 and over four hours in 1991. The concentrations of eight radionuclides were measured at ten points during the same time period (14-17 September 1986). The calculated resuspension factors range from 6 x 10{sup -9} m{sup -1} to 3 x 10{sup -6} m{sup -1}. Data for the spatial means of K are given for certain time periods in 1986 and 1991; also presented are the calculated values according to the models. The experimental data and the calculated values differ by up to more than one order of magnitude. Also analysed was the temporal change in experimental values of K and these values were compared with model predictions. The annual means of the resuspension factor as determined experimentally and as calculated with the models are presented. The model derived from empirical data measured in Neuherberg after the Chernobyl accident agrees best with the data. The Garland model systematically gives results lower than the experimental values, and the calculated values of K from the Linsley model are consistently conservative. Also considered were the uncertainty of K due to fluctuations in air concentrations and possible biological effects of episodic exposures
Interaction and effects of graded levels of dietary phytic acid on the moulting performance, whole body mineral composition and availability on the freshwater prawn Macrobrachium rosenbergii
The presence of anti-nutritional factors such as phytic acid (PA) in a number of potentially useful plant ingredients has been a major impediment to their use as replacements for fishmeal in aquafeeds. This study builds on an earlier studying investigating the growth performance and nutrient utilisation in the juvenile Malaysian giant river prawn, Macrobrachium rosenbergii exploring the effects and interactions of dietary PA with minerals on growth (somatic tissue). Additionally, the study set out to determine the changes in whole-body mineral composition and also on muscle tissues and the carapace, when different levels of PA were included within the diet. The hypothesis under test was that PA, as a mineral-binding agent by chelating di- and trivalent cations inhibits mineral availability. To explore this, effects of graded levels of PA (i.e. 0.26–control, 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg−1) on the moult frequency and mineral availability in juvenile M. rosenbergii (mean initial carapace length of 6.22 ± 0.52 mm; mean initial weight of 0.20 ± 0.01 g; n = 20 per replicate) fed over a period of 140 days were determined. The levels of PA assessed in this feed trial had no major detrimental effects on moult frequency. Negative effects (p < 0.05) of high PA levels (i.e. 21.45–26.16 g PA kg−1), however, were found on the whole-body phosphorus concentration. An increasing trend, although not significantly so, was recorded for the calcium content in the whole-body and carapace with increasing PA inclusion. Significant changes (p < 0.05) were observed in the levels of zinc, copper, potassium and sodium in the carapace, particularly in the prawns fed the diet containing 11.28 g PA kg−1, which suggests that the specific minerals were either selectively utilised or retained in the carapace. These changes may have a serious impairment hence caution should be exercised to ensure that the anti-nutritive effects of PA are minimised