An Air Quality Data Analysis System for Interrelating Effects,Standards, and Needed Source Reductions: Part 6. Calculating Concentration Reductions Needed to Achieve the New National Ozone Standard

The new ozone National Ambient Air Quality Standard specifies that the expected number of days per calendar year that the 1 hour average ozone concentration can exceed 0.12 ppm must be equal to or less than 1. This paper describes a method to calculate design frequency, design concentration, and the percentage concentration reduction necessary to achieve this standard. The design frequency is once per year (1/365) if daily maximum hour ozone concentrations are available at a particular site for an equal number of days in summer (April through September) and winter (October through March). An equation is used to adjust design frequency as a function of the number of summer and winter samples available. The design concentration (the ambient concentration measured at the design frequency) needs to be reduced to 0.12 ppm. Graphical and digital methods for determining the design concentration are presented. Percentage concentration reductions needed to achieve the standard are calculated for each site which has ozone concentration data available in the National Aerometric Data Bank for at least half of the days in one summer of years 1975 through 1977. The degree of reduction calculated for the site with the highest concentrations in each county is indicated by shading on a map of the United States.     

Hazardous air pollutant emissions from gas-fired combustion sources: emissions and the effects of design and fuel type

Air emissions from gas-fired combustion devices such as boilers, process heaters, gas turbines and stationary reciprocating engines contain hazardous air pollutants (HAPs) subjected to consideration under the federal clean air act (CAA). This work presents a recently completed major research project to develop an understanding of HAP emissions from gas-fired boilers and process heaters and new HAP emission factors based on field emission tests of gas-fired external combustion devices used in the petroleum industry. The effect of combustion system design and operating parameters on HAP emissions determined by both field and research tests are discussed. Data from field tests of gas-fired petroleum industry boilers and heaters generally show very low emission levels of organic HAPs. A comparison of the emission data for boilers and process heaters, including units with and without various forms of NOx emission controls, showed no significant difference in organic HAP emission characteristics due to process or burner design. This conclusion is also supported by the results of research tests with different burner designs. Based on field tests of units fired with natural gas and various petroleum industry process gases and research tests in which gas composition was intentionally varied, organic HAP emissions were not determined to be significantly affected by the gas composition. Research data indicate that elevated organic HAP emission levels are found only under extreme operating conditions (starved air or high excess air combustion) associated with poor combustion.     

Are soil mite assemblages structured by the identity of native and invasive alien grasses?

Associations between plants and animals in aboveground communities are often predictable and specific. This has been exploited for the purposes of estimating the diversity of animal species based on the diversity of plant species. The introduction of invasive alien plants into an ecosystem can result in dramatic changes in both the native plant and animal assemblages. Few data exist at the species level to determine whether belowground animal assemblages share the same degree of association to plants. The hypotheses that soil mites (Acari) form assemblages specifically associated with different native grass species in an unmanipulated natural ecosystem and that invasive alien grasses will impact soil mite assemblage composition in this setting were tested. Soil mites sampled beneath five native and two invasive alien species of grasses at the Konza Prairie Biological Station, Kansas, USA, were similarly abundant, species rich, diverse, and taxonomically distinct. No mite species had affinities for a specific grass species. There was no evidence from analysis of similarity, canonical correspondence analysis, or a nonparametric assemblage analysis that the assemblage composition of soil mites was specific to grass species. Results suggest that soil mite assemblages were more related to characteristics of the plant assemblage as a whole or prevailing soil conditions. The most recent invasive alien grass did not support a successionally younger mite fauna, based on the ratio of mesostigmatid to oribatid mites, and neither of the two invasive grasses influenced mite assemblage structure, possibly because they had not yet substantially altered the soil environment. Our results suggest that extrapolations of soil mite diversity based on assumptions of plant specificity would be invalid.     

Identifying primary stressors impacting macroinvertebrates in the Salinas River (California, USA): relative effects of pesticides and suspended particles

Laboratory dose-response experiments with organophosphate and pyrethroid pesticides, and dose-response experiments with increasing particle loads were used to determine which of these stressors were likely responsible for the toxicity and macroinvertebrate impacts previously observed in the Salinas River. Experiments were conducted with the amphipod Hyalella azteca, the baetid mayfly Procloeon sp., and the midge Chironomus dilutus (Shobanov, formerly Chironomus tentans). The results indicate the primary stressor impacting H. azteca was pesticides, including chlorpyrifos and permethrin. The mayfly Procloeon sp. was sensitive to chlorpyrifos and permethrin within the range of concentrations of these pesticides measured in the river. Chironomus dilutus were sensitive to chlorpyrifos within the ranges of concentrations measured in the river. None of the species tested were affected by turbidity as high as 1000 NTUs. The current study shows that pesticides are more important acute stressors of macroinvertebrates than suspended sediments in the Salinas River.     

Understanding self-evaluations of effectiveness by forestry advisory committee members: a case of Ontario's Local Citizens Committee members

Researchers have devised many criteria that could assist with the development of an effective public participation process. Few studies, however, have linked these criteria to the effectiveness of decision-making resulting from these processes. We assess whether several criteria postulated by others for designing an effective decision-making process are associated with evaluations of the effectiveness of decision-making by advisory group members from a forest management planning process in Ontario, Canada. Data were collected by written questionnaires from 197 advisory group members in 2001. Four criteria were linked to the effectiveness evaluations including process control (influence), trust in decision-makers, information credibility, and process efficiency. The criterion of knowledge along with contextual variables related to experience, economic dependence on forestry, and geographical residence were not associated with evaluations of effectiveness.     

Short-term variation and long-term changes in the oceanographic environment and zooplankton community in the vicinity of a sub-Antarctic archipelago

 Mesozooplankton community structure in the vicinity of the Prince Edward Islands (PEIs) was investigated during six surveys conducted in late austral summer (April/May) from 1996 to 1999. Zooplankton samples were collected by oblique tows using a Bongo net fitted with 300-μm mesh. Surface temperature, average temperature and chlorophyll a were measured in conjunction with each net tow. The positions of the Sub-Antarctic Front (SAF) and the Antarctic Polar Front (APF), in relation to the islands, were determined by CTD and/or XBT transects to the west of the islands (upstream). Both fronts were characterized by a high degree of latitudinal variation. Changes in position of the fronts occurred rapidly, the SAF moving up to ∼120 km in a 2-week period. Consequently, the oceanographic environment in the vicinity of the PEIs was subject to a high degree of intra- and inter-survey variation. The positions of the SAF and APF appeared to have a significant impact on phytoplankton biomass in the vicinity of the PEIs, possibly through the alteration of local oceanographic flow dynamics. Water retention over the island shelf in 1996, associated with location of the SAF far to the north of the PEIs, corresponded to enhanced chlorophyll-a concentrations (∼1.54 mg m⁻³). Conversely, when the fronts were close to the islands, as in 1997 and 1999, higher current velocity limited water retention and chlorophyll-a concentrations in the inter-island region were relatively low (∼0.4 mg m⁻³). Cluster analyses showed that, in many instances, there was greater similarity among zooplankton communities from different surveys than among communities within surveys, indicating that short-term variability exceeded inter-annual variability. The population structure of the copepod Calanus simillimus indicated that there was inter-annual variation in the timing of the biological season. Differences in the population structure of species, and consequently their contribution to abundance and biomass, may therefore have been an important contributor to inter-annual variation in community structure. Evidence is provided of a long-term southward shift in the position of the SAF. It is postulated that this may affect the PEIs by increasing the proportion of allochthonous energy input, because the PEIs now lie in the path of the front, altering the tropho-dynamics of the island ecosystem. Lower mesozooplankton biomass associated with warmer sub-Antarctic water may have important negative consequences for higher trophic levels that depend on mesozooplankton for food. Received: 10 June 2000 / Accepted: 22 September 2000     

Differential Individual Particle Analysis (DIPA): applications in particulate matter characterization

Operator-controlled and computer-controlled scanning electron microscopy (CCSEM) are used extensively to characterize particulate matter in environmental media. Analysis in a scanning electron microscope (SEM) coupled with chemical extraction is a potentially powerful tool that is capable of determining how various sample components are associated at the individual particle level. This involves initial characterization in a SEM, after which the material is exposed to a liquid or gas phase reaction for a specified time, and once exposure is concluded, the particles are reanalyzed in the SEM. This particle analysis by difference, or differential individual particle analysis (DIPA), possesses considerable potential for describing the behavior of environmental particles under changing chemical conditions. Here we describe DIPA applications with illustrative examples drawn from the analysis of particulate matter modified by reactions in a fluid environment. In situ DIPA permits the same particles to be analyzed in the SEM before and after modification. Repeated exposure to the same, or different modifying conditions, provides information on the time dependence of specific reactions. Significant numbers of particles can be analyzed using CCSEM, and the same particles can be analyzed after the reaction by accurate sample relocation in the SEM. Ex situ DIPA, which involves a bulk sample modification, uses CCSEM to characterize significant numbers of particles pre- and postreaction. The CCSEM approach is extremely efficient; recent developments in silicon drift detectors have increased the speed of characteristic X-rays detection, and very large numbers of particles can be analyzed in a short period of time.     

The effects of regional angling effort, angler behavior, and harvesting efficiency on landscape patterns of overfishing

We used a coupled social-ecological model to study the landscape-scale patterns emerging from a mobile population of anglers exploiting a spatially structured walleye (Sander vitreus) fishery. We systematically examined how variations in angler behaviors (i.e., relative importance of walleye catch rate in guiding fishing site choices), harvesting efficiency (as implied by varying degrees of inverse density-dependent catchability of walleye), and angler population size affected the depletion of walleye stocks across 157 lakes located near Thunder Bay (Ontario, Canada). Walleye production biology was calibrated using lake-specific morphometric and edaphic features, and angler fishing site choices were modeled using an empirically grounded multi-attribute utility function. We found support for the hypothesis of sequential collapses of walleye stocks across the landscape in inverse proportionality of travel cost from the urban residence of anglers. This pattern was less pronounced when the regional angler population was low, density-dependent catchability was absent or low, and angler choices of lakes in the landscape were strongly determined by catch rather than non-catch-related attributes. Thus, our study revealed a systematic pattern of high catch importance reducing overfishing potential at low and aggravating overfishing potential at high angler population sizes. The analyses also suggested that density-dependent catchability might have more serious consequences for regional overfishing states than variations in angler behavior. We found little support for the hypotheses of systematic overexploitation of the most productive walleye stocks and homogenized catch-related qualities among lakes sharing similar access costs to anglers. Therefore, one should not expect anglers to systematically exploit the most productive fisheries or to equalize catch rates among lakes through their mobility and other behaviors. This study underscores that understanding landscape overfishing dynamics involves a careful appreciation of angler population size and how it interacts with the attributes that drive angler behaviors and depensatory mechanisms such as inverse density-dependent catchability. Only when all of these ingredients are considered and understood can one derive reasonably predictable patterns of overfishing in the landscape. These patterns range from self-regulating systems with low levels of regional fishing pressure to sequential collapse of walleye fisheries from the origin of angling effort.     

Transport of Sewage Sludge From the 106-Mile Site - Results From an October Survey

Abstract

Approximately 8 million tons of sewage sludge were disposed of annually at the 106-Mile Deepwater Municipal Sludge Dump Site (106-Mile Site) between 1987 and 1990. Beginning in 1988 and continuing to the present, the focus of monitoring at the 106-Mile Site moved towards improved understanding of the fate of the sludge. A survey conducted in October 1989 was designed to (1) detect the presence of any sludge particles that settle rapidly following disposal, (2) determine if sludge could be detected in the surface waters at locations away from the immediate disposal site, and (3) determine if water quality was degraded, by assessing whether the Environmental Protection Agency's marine water quality criteria were being exceeded.

The survey showed that the sludge does have a rapidly settling component composed of organic floc. mineral grains, and other heavy, gritlike particles, all of which are relatively large. These particles may settle at rates of between 8 and 180 m h^?1 and may reach the sea floor within 1 to 13 days following disposal. Even though a rapidly settling component is present in the sludge, a significant fraction of the sludge was detectable in the form of intact sludge plumes in the upper 35 m of the water column at least 15 km from the Site. in addition, unique tracers of sludge such as xylem tracheids and Clostridium perfringens plus elevated total suspended solids and trace metals concentrations, were found at locations up to 40 km from the Site. the presence of these tracers correspond with in situ transmissometry data suggesting that a fraction of the sludge was remaining in the near-surface waters above the seasonal pycnocline. Concentrations of metals were below EPA chronic marine water quality criteria, which indicates that the water quality downstream of the Site was not impaired. the detection of sludge downstream of the 106-Mile Site is consistent with the southwestward movement of the surface water mass during the survey, as recorded by satellite-tracked surface drifters and current vectors derived from a current meter moored at 100-m depth immediately west of the Site. Near-surface transport was generally towards the southwest at a speed of approximately 22 cm s^?1?.