PARTIAL AREA RESPONSE ON SMALL SEMIARID WATERSHEDS1

ABSTRACT: Significant errors in estimating surface runoff and erosion rates are possible if a watershed is assumed to contribute runoff uniformly over the entire area, when actually only a portion of the entire area may be contributing. Generation of overland flow on portions of small semiarid watersheds was analyzed by three methods: an average loss rate procedure, a lumped-linear model, and a distributed-nonlinear model. These methods suggested that, on the average, 45, 60, and 50% of the drainage area was contributing runoff at the watershed outlet. Infiltrometer data support the partial area concept and indicate that the low infiltration zones are the runoff source areas as simulated with the distributed-nonlinear model.     

Marketable permits for the prevention of environmental deterioration

This paper develops a modified system of marketable emission permits that promises both savings in abatement costs to sources and improved environmental quality relative to an initial command-and-control (CAC) outcome. Using a model of TSP emissions for the Baltimore Air Quality Control Region (AQCR), a series of simulation exercises indicates that such a permit system could generate large cost savings while inducing significant reductions in TSP concentrations as compared to the existing CAC regime in Baltimore.     

Windsor, Ontario exposure assessment study: design and methods validation of personal, indoor, and outdoor air pollution monitoring

The Windsor, Ontario Exposure Assessment Study evaluated the contribution of ambient air pollutants to personal and indoor exposures of adults and asthmatic children living in Windsor, Ontario, Canada. In addition, the role of personal, indoor, and outdoor air pollution exposures upon asthmatic children's respiratory health was assessed. Several active and passive sampling methods were applied, or adapted, for personal, indoor, and outdoor residential monitoring of nitrogen dioxide, volatile organic compounds, particulate matter (PM; PM < or = 2.5 microm [PM2.5] and < or = 10 microm [PM10] in aerodynamic diameter), elemental carbon, ultrafine particles, ozone, air exchange rates, allergens in settled dust, and particulate-associated metals. Participants completed five consecutive days of monitoring during the winter and summer of 2005 and 2006. During 2006, in addition to undertaking the air pollution measurements, asthmatic children completed respiratory health measurements (including peak flow meter tests and exhaled breath condensate) and tracked respiratory symptoms in a diary. Extensive quality assurance and quality control steps were implemented, including the collocation of instruments at the National Air Pollution Surveillance site operated by Environment Canada and at the Michigan Department of Environmental Quality site in Allen Park, Detroit, MI. During field sampling, duplicate and blank samples were also completed and these data are reported. In total, 50 adults and 51 asthmatic children were recruited to participate, resulting in 922 participant days of data. When comparing the methods used in the study with standard reference methods, field blanks were low and bias was acceptable, with most methods being within 20% of reference methods. Duplicates were typically within less than 10% of each other, indicating that study results can be used with confidence. This paper covers study design, recruitment, methodology, time activity diary, surveys, and quality assurance and control results for the different methods used.     

Estimated hourly personal exposures to ambient and nonambient particulate matter among sensitive populations in Seattle, Washington

Epidemiological studies of particulate matter (PM) routinely use concentrations measured with stationary outdoor monitors as surrogates for personal exposure. Despite the frequently reported poor correlations between ambient concentrations and total personal exposure, the epidemiologic associations between ambient concentrations and health effects depend on the correlation between ambient concentrations and personal exposure to ambient-generated PM. This paper separates personal PM exposure into ambient and nonambient components and estimates the outdoor contribution to personal PM exposures with continuous light scattering data collected from 38 subjects in Seattle, WA. Across all subjects, the average exposure encountered indoors at home was lower than in all other microenvironments. Cooking and being at school were associated with elevated levels of exposure. Previously published estimates of particle infiltration (Finf) were combined with time-location data to estimate an ambient contribution fraction (alpha, mean = 0.66+/-0.21) for each subject. The mean alpha was significantly lower for subjects monitored during the heating season (0.55+/-0.16) than for those monitored during the nonheating season (0.80+/-0.17). Our modeled alpha estimates agreed well with those estimated with the sulfur-tracer method (slope = 1.08; R2 = 0.67). We modeled exposure to ambient and nonambient PM with both continuous light scattering and 24-hr gravimetric data and found good agreement between the two methods. On average, ambient particles accounted for 48% of total personal exposure (range = 21-80%). The personal activity exposure was highly influenced by time spent away from monitored microenvironments. The median hourly longitudinal correlation between central site concentrations and personal exposures was 0.30. Although both alpha and the nonambient sources influence the personal-central relationship, the latter seems to dominate. Thus, total personal exposure may be poorly predicted by stationary outdoor monitors, particularly among persons whose PM exposure is dominated by nonambient exposures, for example, those living in tightly sealed homes, those who cook, and children.     

In vitro genotoxicity of exhaust emissions of diesel and gasoline engine vehicles operated on a unified driving cycle

Acetone extracts of engine exhaust particulate matter (PM) and of vapor-phase semi-volatile organic compounds (SVOCs) collected from a set of 1998-2000 model year normal emitter diesel engine automobile or light trucks and from a set of 1982-1996 normal emitter gasoline engine automobiles or light trucks operated on the California Unified Driving Cycle at 22 [degree]C were assayed for in vitro genotoxic activities. Gasoline and diesel PM were comparably positive mutagens for Salmonella typhimurium strains YG1024 and YG1029 on a mass of PM extract basis with diesel higher on a mileage basis; gasoline SVOC was more active than diesel on an extracted-mass basis, with diesel SVOC more active on a mileage basis. For chromosomal damage indicated by micronucleus induction in Chinese hamster lung fibroblasts (V79 cells), diesel PM expressed about one-tenth that of gasoline PM on a mass of extract basis, but was comparably active on a mileage basis; diesel SVOC was inactive. For DNA damage in V79 cells indicated by the single cell gel electrophoresis (SCGE) assay, gasoline PM was positive while diesel PM was active at the higher doses; gasoline SVOC was active with toxicity preventing measurement at high doses, while diesel SVOC was inactive at all but the highest dose.     

New paradigms for hazardous waste engineering

Today's hazardous waste engineering practice is based on the premise that the current technologies for conducting hazardous waste remediation are sufficient to solve most problems. The premise is false: Except for simple sites, the current practice cannot deliver answers with the required accuracy and precision. This article describes the huge uncertainties present in complex hazardous waste remediation efforts. It also discusses the “observational” method, which originated in the geotechnical engineering field, as a means of coping with these uncertainties during site characterization and remediation. The article includes case-study examples illustrating the use of the observational method at hazardous waste sites.     

Evaluation of maternal serum dimeric inhibin a as a first-trimester marker of down's syndrome

While second-trimester prenatal screening programmes for Down's syndrome have become established in prenatal care, it would be advantageous to be able to offer screening in earlier preganancy. To this end, we have evaluated a new potential maternal serum marker, dimeric inhibin A, as a possible first-trimester marker. Dimeric inhibin A was measured in propsectively collected maternal serum from 23 cases of Down's syndrome and matched chromosomally normal controls, at 11–13 weeks' gestation. Levels of this protein were significantly elevated in the Down's pregnancies compared with the control pregnancies. The median multiple of the normal median (MOM) for the Down's samples was 2.46 (95 per cent confidence interval: 2.11–3.26, P<0.0001 vs. controls). These results suggest that dimeric inhibin A is a useful discriminator of Down's-affected pregnancies from normal pregnancies in the first trimester and that sensitive screening in combination with maternal age and other possible markers may be practicable in the first trimester.     

The use of effluent fees to regulate public sector sources of pollution An application of the niskanen model

The economics literature on environmental policy makes a compelling case for the use of effluent fees to control polluting activities. This analysis, however, proceeds from the assumption of profit maximizing behavior by polluters. Since (non-profit-maximizing) public agencies are a major source of environmental damage, this paper investigates the likely response of bureaucrats to effluent fees in terms of some extended versions of the Niskanen model of bureaucratic behavior. We find that, at least for a range of plausible cases, such fees can induce significant reduction in polluting activities. The results are sufficiently encouraging to make the extension of fees to public agencies worthy of serious consideration.     

Examining the relationship between metal exposure (Cd and Hg), subcellular accumulation,and physiology of juvenile Crassostrea virginica

Environmental Science and Pollution Research - To assess the toxicity and accumulation (total and subcellular partitioning) of cadmium (Cd) and mercury (Hg), juvenile eastern oysters, Crassostrea...