On dispersion above a forest-Measurements and methods.

UNLABELLED: Data collected over a mixed conifer/deciduous forest at the U.S. Department of Energy's Savannah River Site in South Carolina using sonic anemometry reveal that on-site and real-time measurements of the velocity component standard deviations, σv and σw, are preferred for dispersion modeling. Such data are now easily accessible, from the outputs of cost-effective and rugged sonic anemometers. The data streams from these devices allow improvements to conventional methodologies for dispersion modeling. In particular, extrapolation of basic input data from a nearby location to the site of the actual release can be facilitated. In this regard reliance on the velocity statistics σv and σw appears to be preferred to the conventional σθ and σϕ. In the forest situations addressed here, the uncertainties introduced by extrapolating initializing properties (u, θ, σθ, and σϕ, or alternatively, σv and σw) from some location of actual measurement to some nearby location where an actual release occurs are similar to those associated with the spread of the plume itself and must be considered in any prediction of the likelihood of downwind concentration (exposure) exceeding some critical value, i.e., a regulatory standard. Consideration of plume expansion factors related to meander will not necessarily cause predicted downwind maxima within a particular plume to be decreased; however, the probability of exposure to this maximum value at any particular location will be reduced. Three-component sonic anemometers are affordable and reliable, and are now becoming a standard for meteorological monitoring programs subject to regulatory oversight. The time has come for regulatory agencies and the applied dispersion community to replace the traditional discrete sets of dispersion coefficients based on Pasquill stability by the direct input of measured turbulence data. IMPLICATIONS: The continued endorsement of legacy Pasquill-Gifford stability schemes is presently under discussion among professional groups and regulatory agencies. The present paper is an attempt to introduce some rationality, for the case of a forested environment.

The effects of water treatment residues on soil respiration and microbial community structure.

Land disposal of water treatment residue (WTR), a by-product of potable water production, is increasingly being considered a viable alternative to land filling. It is crucial, inter alia, that soil quality is not affected adversely. Six different WTRs obtained from South African water treatment facilities were added to Hutton and Westleigh topsoils at rates of 0, 5, 15 and 25% (m/m) to determine their impacts on soil basal respiration. In general, respiration increased with rate of addition of WTR. The Umgeni, Rand, Midvaal and Faure2 WTRs had the greatest effect on respiration. Increases in respiration became less marked with time. The Hutton topsoil was mixed with the WTRs (at 15% m/m) and, following incubation, the bacterial community structure was examined by denaturing gradient gel electrophoresis. Changes in community structure were detected after 5 d and were attributed to physico-chemical changes arising from WTR amendment. However, dominant bands associated with the Hutton soil were retained and microbial diversity was not adversely affected. The findings of this investigation suggest that WTRs can be applied to the Hutton soil at a rate of at least 15% (300 Mg ha(-1)) without having a detrimental effect on microbial indicators of soil quality.

Colonization of Bacillus spp. on seeds and in plant rhizoplane.

Seed coating, dipping and Scanning Electron Microscopy (SEM) were employed to study bacterial and fungal colonization of the seeds and rhizoplane of maize (Zea mays L.) during the early stages of growth. Isolation of Bacillus spp. entailed screening soil bacteria with potential growth stimulation and plant pathogen suppressive abilities isolated from the rhizospheres and rhizoplanes of vegetable crops. The bacterial colonization of the spermosphere was 90%. When the coated seeds were fully germinated, bacteria moved to the emerging radicle. Virtually no bacteria occurred on the root tip both for the treated and untreated. However, colonization was 20% in the basal portion of the roots close to the seed-root junction. SEM observations showed that the bacterial cells were arranged linearly and laterally on the growing root axis. This phenomenon was more noticeable in the seedlings dipped in the bacterial culture on the 3rd day after germination. The results indicate that attachment to the seed coat and the rhizoplane by the plant growth-promoting rhizobacterium (PGPR) is an important factor in the successful colonization of the rhizoplane. The significance of the work is to ascertain that the inoculated Bacillus spp. adhered to and established in the rhizoplane of maize. It can therefore be used as a PGPR and as a biocontrol agent.

Remote interpretation of chest roentgenograms.

A series of 98 chest films was interpreted by two physicians on the basis of monitor display of the transmitted television signal representing the roentgenographic image. The transmission path was 14 miles long, and included one active repeater station. Receiver operating characteristic curves were drawn to compare interpretations rendered on television view of the image with classic, direct view interpretations of the same films. Performance in these two viewing modes was found to be quite similar. When films containing only hazy densities lacking internal structure or sharp margins, were removed from the sample, interpretation of the remaining films was essentially identical via the two modes. Since hazy densities are visible on retrospective examination, interpretation of roentgenograms at a distance via television appears to be a feasible route for delivery of radiologic services.