On the propagation of error in air pollution measurements

Four methods for estimating the uncertainties in air pollution measurements are outlined. The approaches are: analytical solution-approximation; application of distribution theory; experimentation; and simulation. The advantages and disadvantages of each method are illustrated using data from High-Volume air samplers, the instrument most commonly used for monitoring ambient concentrations of airborne particles.Dr Evans is Assistant Professor of Environmental Science and Mr Kinney is a doctoral candidate in the Department of Environmental Science and Physiology, Harvard School of Public Health. Dr Cooper is at the Manufacturing Research Laboratory, Thomas J. Watson Research Center, IBM, Yorktown Heights, NY.     

POLICIES FOR RESOLVING THE CLIMATE CHANGE AND THE STRATOSPHERIC OZONE DEPLETION ISSUES: ANTAGONISTIC OR RE-ENFORCING?

Unlike the past, anthropogenic activities have begun to have greaterand greater impact on the environment. Policy formulation is no longerconfined to just responding to an existing set of environmentalconditions, but involves taking into account how the decision mightaffect the original set of environmental conditions to which the originalpolicy was formulated as a response.We discuss how certain policies could be developed, using the resultsfrom two integrated scientific models which incorporate parametersreflecting two air issues: (1) climate change, and (2) stratospheric ozonedepletion. Model results suggest very clearly that these two air issuesare not scientifically independent from each other. Following asingle-issue policy would lead to inconsistencies and undesirableconsequences in other related issues. Thus, the policy decision processhas now become complex.One of the sources of this complexity is the uncertainty in the responseof the environmental system to certain policy decisions, complexityarising from the fact that the environmental system is highly nonlinearand evolving. Model results indicate that it is essential for the policyformulation process to be flexible enough to take into account thenonlinear evolutionary nature of the environmental system. A policymust reflect, and be tailored to, the dynamical history and present stateof the system, if it is to be effective in influencing the future evolution of the system.     

Evolution of the magnitude and spatial extent of the weekend ozone effect in California's South Coast Air Basin, 1981-2000

Since the mid-1970s, ozone (O3) levels in portions of California's South Coast Air Basin (SoCAB) on weekends have been as high as or higher than levels on weekdays, even though emissions of O3 precursors are lower on weekends. Analysis of the ambient data indicates that the intensity and spatial extent of the weekend O3 effect are correlated with-day-of-week variations in the extent of O3 inhibition caused by titration with nitric oxide (NO), reaction of hydroxyl radical (OH) with nitrogen dioxide (NO2), and rates of O3 accumulation. Lower NO mixing ratios and higher NO2/oxides of nitrogen (NOx) ratios on weekend mornings allow O3 to begin accumulating approximately an hour earlier on weekends. The weekday/weekend differences in the duration of O3 accumulation remained relatively constant from 1981 to 2000. In contrast, the rate of O3 accumulation decreased by one-third to one-half over the same period; the largest reductions occurred in the central basin on weekdays. Trends in mixing ratios of O3 precursors show a transition to lower volatile organic compound (VOC)/NOx ratios caused by greater reductions in VOC emissions. Reductions in VOC/NOx ratios were greater on weekdays, resulting in higher VOC/NOx ratios on weekends relative to weekdays. Trends in VOC/NOx ratios parallel the downward trend in peak O3 levels, a shift in the location of peak O3 from the central to the eastern portion of the basin, and an increase in the magnitude and spatial extent of the weekend O3 effect.     

BLACK WILLOW CUTTING SURVIVAL IN STREAMBANK PLANTINGS,SOUTHEASTERN UNITED STATES1

Field studies were conducted on black willow (Salix nigra) cuttings planted for riparian zone restoration along Harland Creek, Twentymile Creek, and Little Topashaw Creek in Mississippi, USA. Planted cuttings were 2.5 to 3 m long and had base diameters of 2.5 to 7.5 cm. Streams were unstable, deeply incised sand bed channels with eroding banks 1 to 6 m high. Soil texture, redox potential (Eh), depth to water table, and willow survival were monitored for two to three years after planting. While many factors influence willow cuttings at restoration sites, soil texture and moisture are key to plant success. In these studies, plant survival and growth were best for cuttings planted in soils with less than 40 percent silt‐clay content and a water table 0.5 m to 1.0 m below the soil surface during the growing season. These conditions produced soil Eh greater than approximately 200 mV and were most often observed 1 to 2 m higher than the bank toe. These findings suggest criteria useful for preplanting site evaluations. Additional evidence suggests that preplanting soaking enhances performance of black willow cuttings. Additional factors (channel erosion, herbivory by beaver, and competition from exotics) may control performance over periods longer than two to three years.     

Moisture effects in heat transfer through clothing systems for wildland firefighters.

Wildland firefighters work in unfavourable environments involving both heat and moisture. Moisture in clothing systems worn by wildland firefighters may increase or decrease heat transfer, depending on its source and location in the clothing system, location on the body, timing of application and degree of sorption. In this experiment, 4 outerwear/underwear combinations were exposed to 1 of 5 different conditions varying on amount and location of moisture. The fabric systems were then exposed to either a high-heat-flux flame exposure (83 kW/m(2)) or a low-heat-flux radiant exposure (10 kW/m(2)). Under high-heat-flux flame exposures, external moisture tended to decrease heat transfer through the fabric systems, while internal moisture tended to increase heat transfer. Under low-heat-flux radiant exposures, internal moisture decreased heat transfer through the fabric systems. The nature and extent of such differences was fabric dependent. Implications for test protocol development are discussed.     

FLOODPLAIN MANAGEMENT NEEDS PECULIAR TO ARID CLIMATES1

ABSTRACT: Many practices followed uniformly nationwide in the federal flood control and floodplain management programs are inappropriate or even counter productive in the arid Utah climate. An analysis of the 130-year Utah flood history, the structural and nonstructural flood programs in the state, and local perceptions obtained by field visits and interviews in 35 Utah communities revealed a number of such inefficiencies. Since flood flows dissipate quickly when they emerge from mountain watersheds onto desert lowlands, risks are concentrated near the apex of alluvial fans, include hazard from mud as well as water flow, and are compounded by canal interception of flood waters. Because of variation in the area flooded from one event to the next, floodplain mapping has tended to show risks too high in mapped areas and too low outside. Traditional channelization carries floods downstream past where they would dissipate naturally. The federal government needs to become more active in developing better flood hazard delineation and structural and nonstructural designs for arid areas. State government can help by providing a forum where communities can exchange experiences, reviewing structural designs prepared by local government, and providing local communities with technical expertise for dealing with federal agencies.     

ANALYSIS OF IMPLEMENTATION BARRIERS FOR STATE SCENIC RIVER SYSTEM FORMULATION1

ABSTRACT: Efforts to protect free flowing streams of state significance have met with limited success. Some states established large numbers of “instant” scenic rivers through legislation, then have worked out procedures to add new streams. Other have inadequate current funding and staff to implement the law. The chief barriers to growth of the systems are:

• lack of program staffing and funding and support in some states,
• slowness of the study and planning process,
• landowner uncertainties about the effects on their property and rights, and
• legal complexities.

There are few difficulties experienced in evaluation criteria, but a lack of objective rating systems may cause future problems. The state systems which have grown require careful planning, thorough communications with landowners, flexible land use control programs, and systematic education of community leaders about the values and operation of the program. State systems now protect about four times the river mileage of the federal wild and scenic rivers program. This gap is likely to widen even more, if state programs can achieve their growth potential. No state appears to be yet near to achieving the full purpose of the policy makers who designed and instituted the scenic rivers programs.