Principles and issues in radiological ecological risk assessment

This paper provides a bridge between the fields of ecological risk assessment (ERA) and radioecology by presenting key biota dose assessment issues identified in the US Department of Energy's Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota in a manner consistent with the US Environmental Protection Agency's framework for ERA. Current radiological ERA methods and data are intended for use in protecting natural populations of biota, rather than individual members of a population. Potentially susceptible receptors include vertebrates and terrestrial plants. One must ensure that all media, radionuclides (including short-lived radioactive decay products), types of radiations (i.e., alpha particles, electrons, and photons), and pathways (i.e., internal and external contamination) are combined in each exposure scenario. The relative biological effectiveness of alpha particles with respect to deterministic effects must also be considered. Expected safe levels of exposure are available for the protection of natural populations of aquatic biota (10 mGy d(-1)) and terrestrial plants (10 mGy d(-1)) and animals (1 mGy d(-1)) and are appropriate for use in all radiological ERA tiers, provided that appropriate exposure assumptions are used. Caution must be exercised (and a thorough justification provided) if more restrictive limits are selected, to ensure that the supporting data are of high quality, reproducible, and clearly relevant to the protection of natural populations.     

MICRO-RELIEF SURFACE DEPRESSION STORAGE: ANALYSIS OF MODELS TO DESCRIBE THE DEPTH-STORAGE FUNCTION1

ABSTRACT: Micro-relief surface depression storage is one of the components of the rainfall-runoff process. The quantification of surface depression storage values and a depth-storage model to describe the storage was the subject of this study. Point measurement data were collected on 258 surfaces of 5 soils and three artificial surfaces. Five methods of computing storage, 15 depth-storage models, two depth increments, and six grid spacings were investigated. The 1-inch grid computational method, 0.1-inch depth increment, and 1-inch grid spacings were recommended. The surface depression storage function is best described by the model S = aD^b, which relates surface depression storage as a function of depth with two equation parameters. Equations for describing the surface depression storage model parameters have been developed.     

PROCEDURES FOR THE EVALUATION OF ENGINEERING ALTERNATIVES1

ABSTRACT: This paper describes a method of analyzing the nonquantifiable parameters which should be considered in the evaluation of engineering alternatives. The nonquantifiable parameters can include environmental impact, feasibility of implementation, and performance. The method considers rating all the alternatives on the basis of a set of criteria which reflect these parameters. A procedure is discussed for obtaining review and guidance in the evaluation of engineering alternatives from the local elected officials or governing bodies and for obtaining the views and desires of the local communities. This is achieved through the formation of project review committees and an evaluation procedure which allows for the technical rating of alternatives by the engineer and the weighing of the evaluation criteria by the political and social groups. With the growing environmental concern and the high cost of engineering projects, the involvement of the public during the evaluation of engineering projects is becoming increasingly important to the final success of the project.     

Montane Meadows as Indicators of Environmental Change

We used a time series of satellite multispectral imagery for mapping and monitoring six classes of montane meadows arrayed along a moisture gradient (from hydric to mesic to xeric). We hypothesized that mesic meadows would support the highest species diversity of plants, birds, and butterflies because they are more moderate environments. We also hypothesized that mesic meadows would exhibit the greatest seasonal and interannual variability in spectral response across years. Field sampling in each of the meadow types was conducted for plants, birds, and butterflies in 1997 and 1998. Mesic meadows supported the highest plant species diversity, but there was no significant difference in bird or butterfly species diversity among meadow types. These data show that it may be easier to detect significant differences in more species rich taxa (e.g., plants) than taxa that are represented by fewer species (e.g., butterflies and birds). Mesic meadows also showed the greatest seasonal and interannual variability in spectral response. Given the rich biodiversity of mesic montane meadows and their sensitivity to variations in temperature and moisture, they may be important to monitor in the context of environmental change     

Evolution of tolerance to PCBs and susceptibility to a bacterial pathogen (Vibrio harveyi) in Atlantic killifish (Fundulus heteroclitus) from New Bedford (MA, USA) harbor

A population of the non-migratory estuarine fish Fundulus heteroclitus (Atlantic killifish) resident to New Bedford (NB), Massachusetts, USA, an urban harbor highly contaminated with polychlorinated biphenyls (PCBs), demonstrates recently evolved tolerance to some aspects of PCB toxicity. PCB toxicology, ecological theory, and some precedence supported expectations of increased susceptibility to pathogens in NB killifish. However, laboratory bacterial challenges of the marine pathogen Vibrio harveyi to wild fish throughout the reproductive season and to their mature laboratory-raised progeny demonstrated comparable survival by NB and reference killifish, and improved survival by NB males. These results are inconsistent with hypothesized trade-offs of adaptation, and suggest that evolved tolerance in NB killifish may include mechanisms that minimize the immunosuppressive effects of PCBs. Compensatory strategies of populations persisting in highly contaminated environments provide a unique perspective for understanding the long-term ecological effects of toxic chemicals.     

Reassessment of the Ocean-To-Atmosphere Flux of Carbon Monoxide

Carbon monoxide (CO) in the surface sea waters is produced predominantly by photochemical processes, oxidized by micro-organisms and outgassed to the atmosphere. to assess carbon monoxide flux from the oceans to the atmosphere, the photochemical production and microbial oxidation of carbon monoxide in the oceanic mixed-layer was investigated during several oeanographic cruises and in the laboratory. the photoproduction rate of carbon monoxide was found to be well correlated to the concentration of dissolved organic carbon (DOC) in coastal and open ocean surface waters. Taking a global average carbon monoxide production rate of 10 ± 2 nmole litre^-1 (mg DOC hr)^-1 in the surface open ocean water, and 25 ± 7 nmole litre^-1 (mg DOC hr)^-1 in coastal sea water, at cloud-free summer solar noon, the photochemical production of carbon monoxide in the global oceans is estimated to be at a rate of 1200 ± 200 Tg CO y^-1. the microbial carbon monoxide turnover time in the mixed-layer was observed to range from hours in a coastal estuary to 16 days in the Pacific along 1057deg; W in dark incubations. Natural sunlight can largely inhibit the microbial consumption of carbon monoxide in surface water. On a global scale, microbial consumption is responsible for the loss of less than 10% of photochemical produced carbon monoxide in the surface ocean. Field measurements have shown that the net transport of carbon monoxide from the euphotic zone to the underlying deeper ocean water is limited and that the overall life time in surface sea waters is less than 3-4 hours. When combined, these field measurements with the photoproduction and microbial consumption rates obtained, we estimate the oceanic flux to the atmosphere is about 1000 ± 200 Tg CO y^-1, which represents the largest single source of atmospheric carbon monoxide.