RESUMO
This paper contrasts applications of both the contingent valuation (CV) and contingent ranking (CR) methods as applied to a common issue, the valuation of improvements to the water quality of an urban river (the River Tame, running through the city of Birmingham, UK). Building upon earlier experimental work, the CV design used ensures that respondents are fully aware of all impending valuation tasks prior to undertaking any one of those tasks. Such an approach is directly comparable to the CR design for which full awareness of all options is a pre-requisite. Findings indicate that the CV responses exhibit strong internal consistency with expected relationships observed between values and theoretically expected parameters. External comparisons show that CR valuations are substantially larger than those elicited through CV (with protest votes excluded), and that the response rate for the CR survey is significantly higher than that for the CV survey.
Assuntos
Água Doce , Água/normas , RiosRESUMO
A modified large-volume sampler was demonstrated to be an efficient device for the collection of mono-disperse aerosols of rhodamine B and poly-disperse aerosols of bacterial cells. Absolute efficiency for collection of rhodamine B varied from 100% with 5-mum particles to about 70% with 0.5-mum particles. The sampler concentrated the particles from 950 liters of air into a flow of between 1 and 2 ml of collecting fluid per min. Spores of Bacillus subtilis var. niger were collected at an efficiency of about 82% compared to the collection in the standard AGI-30 sampler. In the most desirable collecting fluids tested, aerosolized cells of Serratia marcescens, Escherichia coli, and Aerobacter aerogenes were collected at comparative efficiencies of approximately 90, 80, and 90%, respectively. The modified sampler has practical application in the study of aerosol transmission of respiratory pathogens.