Simulation of Airport Air Quality by Box Photochemical and Gaussian Models

Brookhaven National Laboratory has critically evaluated the structure and results of the Stanford Research Institute model (SRI model) for assessing national-level economic impacts of oxidants on plants. In response to inherent weaknesses in the SRI approach, a new model (DAMAGE) was constructed to estimate national-level damage from oxidants for alfalfa. DAMAGE uses actual oxidant measurements and the Oshima dose-response function for alfalfa to estimate effects on yield. Economic loss is then simply calculated by multiplying crop value by percent loss. Estimates of oxidant effects on alfalfa in 1974 were calculated with both DAMAGE and the SRI model. Results of the SRI model closely approach those of DAMAGE when the dose estimate is approximated by the seasonal total of the hourly averages. Other methods of estimating dose in DAMAGE give distinctly higher estimates of economic loss. The lower bound estimates suggest losses equal to $20 million or 4% of the total yield in the counties examined. Upper estimates suggest losses as high as $200 million or a 36% reduction in yield.     

A general bioeconomic simulation model for annual-crop marine fisheries

A generalized bioeconomic simulation model of annual-crop marine fisheries is described and its use in marine fisheries management is demonstrated. The biological submodel represents the recruitment of new organisms into the fishery, the movement of organisms from one fishing area to another and from one depth to another, the growth of organisms and the mortality of organisms resulting both from natural causes and from fishing. The economic submodel represents the fishing effort exerted on each resource species, the monetary costs of fishing, the value of the harvest and the rent (or excess profits) to the fishery.Basic dynamics of the model results from changes in the number of organisms in the fishery over time, which can be summarized as a set of difference equations of the general form ΔN/Δt = R + I ? E ? M ? F where ΔN/Δt is the net change in number of organisms in the fishery over time, R is recruitment, I is immigration, E is emigration, M is natural mortality and F is fishing mortality. R is a driving variable, whereas I, E, M and F are functions of the state of the system at any given point in time. The model can be run in a deterministic or stochastic mode. Values for parameters affecting rates of recruitment, movement, growth, natural mortality and fishing mortality can be selected from uniform, triangular or normal distributions.Use of the model within a fisheries-management framework is demonstrated by evaluating several management alternatives for the pink shrimp (Penaeus duorarum) fishery on the Tortugas grounds in the Gulf of Mexico. Steps involved in use of the model, including parameterization, validation, sensitivity analysis and stochastic simulations of management policies, are explained.     

Serengeti wildebeest migratory patterns modeled from rainfall and new vegetation growth

We used evolutionary programming to model innate migratory pathways of wildebeest in the Serengeti Mara Ecosystem, Tanzania and Kenya. Wildebeest annually move from the southern short-grass plains of the Serengeti to the northern woodlands of the Mara. We used satellite images to create 12 average monthly and 180 10-day surfaces from 1998 to 2003 of percentage rainfall and new vegetation. The surfaces were combined in five additive and three multiplicative models, with the weightings on rainfall and new vegetation from 0% to 100%. Modeled wildebeest were first assigned random migration pathways. In simulated generations, animals best able to access rainfall and vegetation were retained, and they produced offspring with similar migratory pathways. Modeling proceeded until the best pathway was stable. In a learning phase, modeling continued with the ten-day images in the objective function. The additive model, influenced 25% by rainfall and 75% by vegetation growth, yielded the best agreement, with a multi-resolution comparison to observed densities yielding 76.8% of blocks in agreement (kappa = 0.32). Agreement was best for dry season and early wet season (kappa = 0.22-0.57), and poorest for the late wet season (0.04). The model suggests that new forage growth is a dominant correlate of wildebeest migration.     

Environmental Persistence of Chemicals

- DOI: http://dx.doi.org/10.1065/espr2006.01.008 Background The hazard criterion of persistence as it applies to chemicals in the environment is reviewed and discussed. This quantity can not be measured directly in the environment, thus it must be estimated using models that synthesise information on chemical half-lives and partitioning properties, the nature of the environment and how the chemical is released into the environment. Main Features It is suggested that the preferred criterion is the average residence time of the chemical in the environment, i.e. conceptually the sum of the life-times of all molecules (attributable only to losses by degrading reactions) divided by the number of molecules. If all chemical fate processes are first order, this persistence is independent of the quantity of chemical introduced and whether introduction is steady- or unsteady-state in nature. It is shown that in a multimedia environment persistence is affected not only by degradation kinetics, but also by mode-of-entry and partitioning. For screening level purposes a Level II equilibrium model may be adequate but a Level III model is generally preferable for estimating the average persistence. If a distribution of persistences is required a dynamic Level IV model must be used. Discussion The implications for regulating chemicals on the basis of persistence are discussed. Conclusion It is concluded that the preferred strategy is to use Level II, III, and IV models and that the use of only degradation kinetics or media-specific half-lives can be misleading and uneconomical.     

Effects of sulfur dioxide and nitric oxide on mercury oxidation and reduction under homogeneous conditions

This paper is particularly related to elemental mercury (Hg0) oxidation and divalent mercury (Hg2+) reduction under simulated flue gas conditions in the presence of nitric oxide (NO) and sulfur dioxide (SO2). As a powerful oxidant and chlorinating reagent, Cl2 has the potential for Hg oxidation. However, the detailed mechanism for the interactions, especially among chlorine (Cl)-containing species, SO2, NO, as well as H2O, remains ambiguous. Research described in this paper therefore focused on the impacts of SO2 and NO on Hg0 oxidation and Hg2+ reduction with the intent of unraveling unrecognized interactions among Cl species, SO2, and NO most importantly in the presence of H2O. The experimental results demonstrated that SO2 and NO had pronounced inhibitory effects on Hg0 oxidation at high temperatures when H2O was also present in the gas blend. Such a demonstration was further confirmed by the reduction of Hg2+ back into its elemental form. Data revealed that SO2 and NO were capable of promoting homogeneous reduction of Hg2+ to Hg0 with H2O being present. However, the above inhibition or promotion disappeared under homogeneous conditions when H2O was removed from the gas blend.     

A flume study of drift in marine infaunal amphipods (Haustoriidae)

Amphipods of the infaunal family Haustoriidae are characteristic of high-energy marine sands and occur both in the sediment and the overlying water column. Sediments in this habitat are subject to constant reworking by tidal currents, suggesting that resident amphipod populations are affected by this disturbance in a phenomenon similar to freshwater invertebrate drift. A controlled-velocity laboratory flume was used to examine the effect of haustoriid density, current velocity, illumination, and food availability on drift rates to determine a causal basis for drift. Drift is densityindependent and greatest at night and during high current flow; it is also greater at night from sterile sediment than from untreated sand. Flume transport was usually less than 10% of amphipods present in the sediment. Haustoriids captured downstream were mostly adults occurring in a 1:1 sex ratio, suggesting no obvious function of drift in reproduction. Current-induced displacement of haustoriids may produce the patchiness in distribution observed in nature. Disturbance of the bed could also function to keep amphipod densities below the carrying capacity of the local environment. In certain cases, food limitation may cause amphipods to actively leave the substrate. Under all conditions, greater drift rates in darkness are probably adaptive in avoidance of predators. Despite the nature of sediment movement in a high-energy environment, haustoriid drift may have an active as well as passive component.     

Localized defecation by pike: a response to labelling by cyprinid alarm pheromone?

Fathead minnows (Pimephales promelas) that have never encountered a predatory pike (Esox lucius), are able to detect conspecific alarm pheromone in a pike's diet if the pike has recently consumed minnows. It remains unclear how this minnow alarm pheromone is secreted by pike and if a pike is able to avoid being labelled as a potential predator by localizing these cues away from its foraging range. The first experiment determined that minnow alarm pheromone is present in pike feces when pike are fed minnows. Individual fathead minnows exhibited a fright response to a stimulus of pike feces if the pike had been fed minnows, but not if the pike had been fed swordtails, which lack alarm pheromone. Individual minnows also exhibited a fright reaction to alarm pheromone in the water (which contained no feces) housing pike which had been fed minnows, suggesting that alarm pheromone is also released in urine, mucous secretions and/or via respiration. The second experiment determined that test pike spent a significantly greater proportion of time in the home area of the test tanks (i.e. where they were fed) but the majority of feces were deposited in the opposite end of the test tank. By localizing their defecation away from the home or foraging area, pike may be able to counter the effects of being labelled as a predator by the alarm pheromone of the prey species.     

Sensitivity of benthic community respiration and primary production to changes in temperature and light

In-situ measurements of benthic community respiration and primary production on an intertidal sandflat in Nova Scotia, Canada were used to test the hypothesis that community responses to light and temperature were similar within and between seasons. Multiple regression indicated that mean incubation temperature explained 57% of the variance in total sediment oxygen demand (TOD). The logarithmic relationship between TOD and temperature (Q₁₀=6.5) was not significantly different between fall and spring, suggesting no acclimation within season. Chemical oxygen demand measured in formalin-poisoned cores averaged 30% of TOD. Microalgal gross primary production (GROSS) was measured as oxygen production in light cores. Mean incubation temperature and sediment chlorophylla explained 56% of the variance. The linear relationship between GROSS and temperature had Q₁₀=2.0. When production was normalized to chlorophylla [GROSS(SP)], seasonal production-temperature curves were significantly different. The spring curve had Q₁₀=3.3; in the fall, production and temperature were not related. GROSS(SP)-light curves derived from Plexiglas shade experiments in the field were linear and not significantly different between fall and spring. Temperature alone was a better predictor of GROSS(SP) than light, even when P/I curves were adjusted for temperature. One can therefore model community respiration and photosynthesis at this site using daily averages in temperature, which are then summed over longer time scales to estimate monthly or seasonal rates.     

Aggressiveness and foraging mode of young-of-the-year brook charr,Salvelinus fontinalis (Pisces,Salmonidae)

Summary Young-of-the-year brook charr in streams use either an active or a sit-and-wait foraging tactic and exhibit a range of resource defense from territoriality to tolerating conspecifics. We use simple graphical models, based on encounter rate with drift and the theory of economic defendability, to predict qualitative changes in the aggressiveness and mobility of brook charr in relation to current velocity. Aggressiveness (percent of conspecifics eliciting an overt response) initially increases with increasing current velocity, as does drift rate and foraging rate. However, aggressiveness decreases at high current velocities, probably because of increased costs of defense at these velocities. In standing water areas, brook charr use primarily an active foraging tactic, but mobility (percent time spent moving) decreases rapidly as current velocity increases. These results are generally consistent with the simple graphical models. A literature survey suggests that the models can be generalized for most species of stream salmonids.     

Wave Enhancement of Diffusivities within Surficial Sediments

The enhancement of solute diffusivities within coastal surficial sediments as a result of wave action is examined. Fluctuating pressure gradients associated with passing waves cause interstitial water motions leading to enhanced diffusivities through the mechanism of shear dispersion. Wave amplification of diffusivities is likely to be greatest for waves of period 10 s, in shallow water, over a bottom of coarse grain. Diffusivity enhancement of hundreds of times molecular diffusivity is achievable. The mechanism is distinct from, but complements, the mechanism of rotational dispersion which has been previously described. Other mechanisms that enhance solute transport within surficial sediments rely on the interaction between wave-driven or steady flow over bottom obstructions such as biogenic structures or sand ripples. It is suggested that while the resulting advective flows may dominate solute transport within the top few 10 s of centimeters of the sediment column, shear dispersion may be more important deeper within the sediment. In any event, in contrast to these other mechanisms, shear dispersion is operative even when the seabed is flat. Application of the theory to sediments of the South Atlantic Bight would suggest that shear dispersion is capable of explaining a major part of the interstitial transport inferred from measurements.