Ozone Control Strategies Based on the Ratio of Volatile Organic Compounds to Nitrogen Oxides

The 1990 Clean Air Act Amendments require states with O₃ nonattainment areas to adopt regulations to enforce reasonable available control technologies (RACT) for NO_X stationary sources by November 1992. However, if the states can demonstrate that such measures will have an adverse effect on air quality, NO_X requirements may be waived. To assist the states in making this decision, the U.S. EPA is attempting to develop guidelines for the states to use in deciding whether NO_X reductions will have a positive or negative impact on O3 air quality. Although NO_X is a precursor of O₃, at low VOC/NO_X ratios, the reduction of NO_X can result in increased peak O₃. EPA is examining existing information on VOC/NO_X ratios to develop “rules of thumb” to guide the states in their decision-making process. An examination of 6 a.m. to 9 a.m. VOC/NO_X ratios at a number of sites in the eastern U.S. indicates that the ratio is highly variable from day-to-day and there is no apparent relationship between ratios measured at different sites within the same area. In addition, statistical analysis failed to identify significant relationships between the 6 a.m. to 9 a.m. VOC/NO_X ratio and the maximum 1-hr. O₃ within a given area. Since we know from smog chamber and modeling studies that such a relationship exists, this further invalidates the assumption that a ratio measured at a single site is representative of the ratio for the entire region. Based on this Information, we conclude that having the 6 a.m. to 9 a.m. ambient VOC/NO_X ratio for a given area is insufficient information, by itself, to decide whether a VOC-alone, a NO_x-alone, or a combined VOC-NO_X reduction strategy is a viable or optimum O₃-reduction strategy.     

Characterization of Municipal Solid Waste Incineration Residues From Facilities with Different Air Pollution Control Systems

Abstract

Municipal Solid Waste incinerator residues produced in two types of facilities were exhaustively characterized: granulometry, mineralogy, chemical composition, leaching behavior, and elemental distribution as a function of particle size. Air Pollution Control (APC) residues coming from a semi-dry scrubber have shown higher solubility than fly ashes originating in an Electrostatic Precipitator (ESP), as well as higher contents in volatile metals (Cd, Hg). Different metal speciation and distribution as a function of particle size have been found in fly ashes (ESP residues) and APC residues. In APC residues, heavy metals (with the exception of Hg) show a parabolic distribution with maxima in the smallest and largest particles, following the same profile as soluble salts. Metal distribution for APC residues exhibits that metals generally are not associated with silicate aluminate matrix. Results show the effect of adding lime to APC residues in metal speciation and distribution.     

Feasibility of Applying a Stable Isotopic Tracer for Direct Determination of Dry Particulate Deposition to Soybean Plants

ABSTRACT

A stable rare-earth isotopic tracer was used to measure the deposition of KNO₃ particles on soybean leaves by direct measurement of the tracer on the plant surfaces by thermal-ionization mass spectrometry. Submicrometer particles, made from a solution containing 3 |mg mL^-1 neodymium isotope (¹⁴⁸Nd, 87.9%) and 1,000 mg mL^-1 KNO₃, were dispersed with a two-fluid nozzle and released upwind of a soybean field. Total suspended- and size-fractionated-aerosol particles were collected on an open-face filter and in a micro-orifice impactor, respectively, at a distance of 40 m from the release point. Soybean leaves exposed to the plume were collected at distances ranging from 25 to 100 m. As little as 5.5 pg of the tracer (i.e., excess ¹⁴⁸Nd) was detected in soybean leaves at signal-to-noise ratios ranging from 7,500 to 240,000, in the presence of 200 to 2,700 pg of naturally occurring Nd. The dry-particle deposition velocity, determined from the ratio of the aerial concentration and directly deposited aerosol (geometric mass mean diameter, 0.20 mm) flux, and its corresponding analytical uncertainty were 0.30 cm sec^-1 and 2.5%, respectively.     

A Method of Predicting Point and Path- Averaged Ambient Air VOC Concentrations,Using Meteorological Data

A method of predicting point and path-averaged ambient air VOC concentrations is described. This method was developed for the case of a plume generated from a single point source, and is based on the relationship between wind directional frequency and concentration. One-minute means of wind direction and wind speed were used as inputs to a Gaussian dispersion model to develop this relationship.

Both FTIR spectrometry and a whole-air sampling method were used to monitor VOC plumes during simulated field tests. One test set was also conducted using only whole-air samplers deployed in a closely-spaced network, thus providing an evaluation of the prediction technique free of any bias that might exist between the two analytical methods.

Correlations between observed point concentrations and wind directional frequencies were significant at the 0.05 level in most cases. Predicted path-integrated concentrations, based on observed point concentrations and meteorological data, were strongly correlated with observed values. Predicted point concentrations, based on observed path-integrated concentrations and meteorological data, accurately reflected the location and magnitude of the highest concentrations from each test, as well as the shape of the concentration-versus-crosswind distance curve.     

The Emissions and Dispersion Modeling System (EDMS): Its Development and Application at Airports and Airbases

A new complex source microcomputer model has been developed for use at civil airports and Air Force bases. This paper describes both the key features of this model and its application in evaluating the air quality impact of new construction projects at three airports: one in the United States and two in Canada.

The single EDMS model replaces the numerous models previously required to assess the air quality impact of pollution sources at airports. EDMS also employs a commercial data base to reduce the time and manpower required to accurately assess and document the air quality impact of airfield operations.

On July 20, 1993, the U.S. Environmental Protection Agency (EPA) issued the final rule (Federal Register, 7/20/93, page 38816) to add new models to the Guideline on Air Quality Models. At that time EDMS was incorporated into the Guideline as an Appendix A model.     

Biological nitrogen and carbon removal in a gravity flow biomass concentrator reactor for municipal sewage treatment

A novel membrane system, the Biomass Concentrator Reactor (BCR), was evaluated as an alternative technology for the treatment of municipal wastewater. Because the BCR is equipped with a membrane whose average poresize is 20 μm (18–28 μm), the reactor requires low-pressure differential to operate (gravity). The effectiveness of this system was evaluated for the removal of carbon and nitrogen using two identical BCRs, identified as conventional and hybrid, that were operated in parallel. The conventional reactor was operated under full aerobic conditions (i.e., organic carbon and ammonia oxidation), while the hybrid reactor incorporated an anoxic zone for nitrate reduction as well as an aerobic zone for organic carbon and ammonia oxidation. Both reactors were fed synthetic wastewater at a flow rate of 71 L d^?1, which resulted in a hydraulic retention time of 9 h. In the case of the hybrid reactor, the recycle flow from the aerobic zone to the anoxic zone was twice the feed flow rate. Reactor performance was evaluated under two solids retention times (6 and 15 d). Under these conditions, the BCRs achieved nearly 100% mixed liquor solids separation with a hydraulic head differential of less than 2.5 cm. The COD removal efficiency was over 90%. Essentially complete nitrification was achieved in both systems, and nitrogen removal in the hybrid reactor was close to the expected value (67%).     

Effects of simulated sublethal predation on the growth and regeneration rates of a spionid polychaete in laboratory flumes

Most spionid polychaetes switch from deposit feeding to suspension feeding as current speed and the flux of suspended food increase. Growth rates of juvenile Polydora cornuta are strongly affected by flow and can be as rapid as 60% day⁻¹ in moderate currents. Feeding palps that extend above the sediment–water interface during suspension feeding are especially vulnerable to sublethal predation, but individuals with damaged posteriors are also common. We performed a series of laboratory flume experiments to test the effects of sublethal tissue damage on the growth and regeneration rates of P. cornuta juveniles. Replicated experiments were conducted at three flow speeds in counter-rotating annular flumes containing field-collected sediment and a nonliving algal slurry as deposited and suspended food. In the first set of experiments, we removed 2, 1, or 0 of worms’ two feeding palps and measured the relative growth rates of worm bodies and palps after 3 days in the flumes. Worms that lost both palps grew significantly slower than the other two groups, but the growth rate of worms that had one undamaged palp was not significantly different from worms that had two undamaged palps. Faster flow speeds significantly increased rates of body growth, and there was a significant interaction between flow and the effect of palp loss. During the 3-day experiments, damaged palps fully regenerated and often grew larger than they were prior to being removed. Damaged palps also grew significantly faster than undamaged palps. The second set of experiments tested the effects of removing a worm’s posterior region (~18% of body volume). The growth rates of these damaged and undamaged worms did not differ significantly. By the end of a 3-day flume experiment, damaged worms had grown 6× larger than they were prior to the posterior damage. The rapid regeneration of damaged palps and posterior tissue in moderate flows that allow suspension feeding suggests that sublethal predation on spionids might be more frequent than previously estimated and will have little impact on the growth of juvenile recruits.     

Molecular phylogeny and population structure of tideland snails in the genus Cerithidea around Japan

Phylogenetic relationships and genetic population structures were analyzed for tideland gastropods in the genus Cerithidea around Japan on the basis of partial sequence of the mitochondrial COI gene. Large genetic divergence was shown between individuals of Cerithidea cingulata in the southern Ryukyus and those in the central Ryukyus and the Japanese Islands. Haplotypes of C. cingulata from the Japanese Islands were paraphyletic with the exclusion of a monophyletic group from the central Ryukyus. Genetic differentiation of C. cingulata was also detected between Amami-Oshima Island and Okinawajima Island. No genetic divergence was found between Cerithidea rhizophorarum in the Japanese Islands and its subspecies C. rhizophorarum morchii in the Ryukyu Islands. The lack of genetic divergence of Cerithidea largillierti between continental China and Japan suggests relatively recent migration between the Japanese Islands and the Asian continent. For all three Cerithidea species distributed in both the Japanese Islands and the Ryukyu Islands, the Tokara Gap and the Kerama Gap were shown to have acted as barriers to the dispersal.     

Does information of predators influence general wariness?

Antipredator behavior includes several qualitatively distinct activities, but few studies have determined the degree to which these activities are independent. If behaviors are not independent, then the nature of the relationship would illustrate potential performance constraints. We studied crimson rosellas (Platycercus elegans) and first focused on acoustic predator discrimination. We measured time allocation before and after playback of one of three experimental treatments (peregrine falcons—Falco peregrinus, wedge-tailed eagles—Aquila audax, and crimson rosellas) to determine whether or not rosellas discriminated predators from non-predators, and specifically whether or not they discriminated large from small predators. We then focused on the decision to flee. We experimentally approached subjects and measured the distance at which they oriented to us (alert distance) and the distance at which they fled (flight initiation distance; FID). We found that rosellas could distinguish among predators; however, there was no effect on general wariness as measured by FID. These two processes of antipredator behavior may, thus, be independent.     

Hidden ancient diversification in the circumtropical lancelet Asymmetron lucayanum complex

The tropical lancelet Asymmetron lucayanum (= Epigonichthys lucayanus) is distributed from the western Indian Ocean to the central Pacific Ocean, and the western Atlantic Ocean. Molecular phylogenetic analysis of mitochondrial cytochrome c oxidase subunit I (COI) sequences (1,035 bp) of A. lucayanum (80 specimens from seven localities) showed clearly that this species is genetically distinguished into three major groups of geographical populations based on neighbor-joining tree using maximum likelihood distance (HKY model with invariable sites and gamma correction), suggesting the existence of three cryptic species. Our genetic data show that (1) inter-oceanic divergence time between Clade B (the West-Central Pacific) and Clade C (the Atlantic) (d = 6.6%, ca. 12 million years ago) was smaller than intra-oceanic divergence time between Clade A (the Indo-West Pacific) and Clade B (d=39.5%, ca. 100 million years ago); (2) there are two cryptic species in the West Pacific in sympatry; and (3) high gene flow is implied between the Maldives and the Ryukyus in Clade A (10,000 km distance), the Philippines and Hawaii in Clade B (8,500 km distance), and Barbados and Bermuda in Clade C (2,200 km distance).