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71.
Economic theory asserts that to achieve maximum conservation benefits land acquisition needs to be cost effective. Yet the most common planning technique used by land conservation organizations is ‘benefit-targeting’ that focuses only on acquiring parcels with the highest benefits and ignores costs. Unlike most of the literature which focuses on covering problems, this research applies optimization techniques to achieve maximum aggregate conservation benefits for an ongoing land acquisition effort in the Catoctin Mountain Region in central Maryland. For this case study, optimization yields additional conservation benefits worth an estimated $3.1–$3.9 million or achieves the same level of conservation benefits but at a cost savings ranging from $0.9 to $3.5 million, depending on the initial budget size. Finally, the highest efficiencies are achieved in low budget scenarios, like those most prevalent in conservation efforts. 相似文献
72.
Kent W. Thornton Joe F. Nix Jimmy D. Bragg 《Journal of the American Water Resources Association》1980,16(1):86-92
ABSTRACT: Knowledge of coliform transport and disappearance may provide information for project design and operation that minimizes potential water quality problems such as the violation of body contact recreation standards. Storm events were sampled in the Caddo River above DeGray Reservoir, Arkansas, and then tracked through the reservoir using the increased turbidity associated with the storm flows. Fecal coliforms were sampled both in the river and throughout the water column in the reservoir. In general, increased fecal coliform concentrations were closely associated with the increased turbidity resulting from the storm flows. This association existed for all three types of turbidity plume movement - overflow, interflow, and underflow. As the turbidity plume moved down the reservoir, fecal coliform concentrations decreased due to die-off, settling, and dilution. With several assumptions, it is possible to use this information to assist in locating recreational sites in a reservoir or to anticipate possible body contact standard violations at existing recreation sites. 相似文献
73.
The application of a solvophobic approach for predicting the sorption of hydrophobic organic compounds (HOC) was evaluated with data collected using synthetic sorbents and soils. The experimental data consisted of batch equilibrium sorption coefficients (KD), as well as soil-TLC and reversed-phase liquid chromatographic (RPLC) retention factors (κ′). All data were collected using aqueous solutions and binary or ternary solvent mixtures of water, methanol, acetone, and acetonitrile. As predicted by the theory, the chromatographic retention factors and sorption coefficients for HOC decreased log-linearly with increasing fraction of organic cosolvent in binary solvents. Model parameters estimated from the binary solvent data could be used to predict sorption (or retention) from ternary solvents. Reasonable agreement was found between model parameters reported in the literature and those estimated using the data from batch sorption, soil-TLC, and RPLC studies. 相似文献
74.
A bioassay for rhizosphere-applied phytotoxicants was developed and evaluated with a broad range of chemicals. Test substances were applied to the rhizosphere of whole, intact bush bean plants (Phaseolus vulgaris L. cv. Bush Blue Lake 290) grown in a solid support medium and the resultant ethylene production was measured to detect the presence of phytotoxic materials. The beans were encapsulated in plastic bags for 2 hr following treatment and then incubated for 24 hr in the dark. Ethylene and ethane accumulating within the bags were quantified via gas-solid chromatography. The application of various concentrations of inorganic and organic chemicals induced various responses. No single equation adequately described the dose-response curves; therefore, a critical value (a statistically significant increase in stress ethylene) was computed for each test substance. A phytotoxic-response threshold for each test substance was defined as the test-substance concentration that caused ethylene production to exceed its respective critical-value concentration. Based on threshold concentrations determined by analysis of stress ethylene production, the relative phytotoxicity rankings of the inorganic test substances were: CdCl2>CuCl2>Pb(C2H3O2)2>LiCl, while those of the organic test substances were 2,4-D esters>paraquat dichloride>1-butanol>2-propanone>2-propanol. Both stress ethylene and ethane production were nonresponsive to hydrogen-ion concentration (measured before application) over a broad pH range. However, significant ethane production was detected at pH 2 and stress ethylene was produced at pH 1. The measurement of stress-induced ethylene provides a rapid and simple means to determine the relative phytoxicity of rhizosphere-applied substances. 相似文献
75.
Jennifer L. Harris Kevin MacIsaac Kent D. Gilkinson Ellen L. Kenchington 《Marine Biology》2009,156(9):1891-1902
Ophiura sarsii was collected in May/June from Banquereau Bank off Nova Scotia, Canada as part of the benthic fauna analyzed in a 2 year
clam dredging-impact experiment. In total, 529 O. sarsii specimens were analyzed; 174 (33%) had stomach contents while the rest were empty. Ophiura sarsii is a trophic generalist feeding on at least 31 taxa (52% identified to species) drawn from four phyla: Arthropoda (81.8%),
Annelida (13.2%), Mollusca (3%), and Cnidaria (1.5%). However, the diet was largely restricted to two amphipod families (Ampeliscidae
and Lysianassidae), accounting for 54–70% of stomach contents at any one sampling period. This diet provides indirect evidence
for carnivory. Limited spatial and temporal heterogeneity in the proportion of animals feeding showed no consistent pattern.
Where diet composition differed (ANOSIM) it was attributed to the proportion of lysianassid and ampeliscid amphipods consumed.
Dredging introduced new dietary items, although diet composition was not significantly altered. 相似文献
76.
Sven Andersson Evalena W. Blomqvist Linda Bäfver Frida Jones Kent Davidsson Jan Froitzheim Martin Karlsson Erik Larsson Jesper Liske 《Waste management (New York, N.Y.)》2014,34(1):67-78
Sulfur recirculation is a new technology for reducing boiler corrosion and dioxin formation. It was demonstrated in full-scale tests at a Waste to Energy plant in Göteborg (Sweden) during nearly two months of operation. Sulfur was recirculated as sulfuric acid from the flue gas cleaning back to the boiler, thus creating a sulfur loop.The new technology was evaluated by extensive measurement campaigns during operation under normal conditions (reference case) and operation with sulfur recirculation. The chlorine content of both fly ash and boiler ash decreased and the sulfur content increased during the sulfur recirculation tests. The deposit growth and the particle concentration decreased with sulfur recirculation and the dioxin concentration (I-TEQ) of the flue gas was reduced by approximately 25%. Sulfuric acid dew point measurements showed that the sulfuric acid dosage did not lead to elevated SO3 concentrations, which may otherwise induce low temperature corrosion.In the sulfur recirculation corrosion probe exposures, the corrosion rate decreased for all tested materials (16Mo3, Sanicro 28 and Inconel 625) and material temperatures (450 °C and 525 °C) compared to the reference exposure. The corrosion rates were reduced by 60–90%. Sulfur recirculation prevented the formation of transition metal chlorides at the metal/oxide interface, formation of chromate and reduced the presence of zinc in the corrosion products. Furthermore, measured corrosion rates at 525 °C with sulfur recirculation in operation were similar or lower compared to those measured at 450 °C material temperature in reference conditions, which corresponds to normal operation at normal steam temperatures. This implies that sulfur recirculation allows for higher steam data and electricity production without increasing corrosion. 相似文献
77.
Christian Steinberg Markus Haitzer Sebastian Höss Renate Lorenz Rainer Brüggemann B. Kent Burnison 《Environmental Sciences Europe》1997,9(2):64-68
Humic substances, in aqueous bodies primarily fulvic acids, may demonstrate an inhibitory as well as an activating influence on organisms. We present evidence with bacteria-containing algal cultures and with cultures of the nematodeCaenorhabditis elegans. Structural elements of the fulvic acids which may be responsible for such effects are not yet known. Furthermore, the presence of fulvic acids may lead to increases in bioconcentration of xenobiotics. Increase in the toxicity of xenobiotics in the presence of humic substances have also been described. We present studies applying lethal as well as sublethal toxicity endpoints. 相似文献
78.
John G. Hof Robert D. Lee A. Allen Dyer Brian M. Kent 《Journal of Environmental Economics and Management》1985,12(4)
This paper analyzes the tenability of line item budgeting and independently determined output costs for a managed forest ecosystem. The general problem of cost allocation in a joint production system is discussed as one of choosing paths of integration. A production structure is hypothesized for describing a managed forest ecosystem and its characteristics of “jointness” are discussed. Finally, an empirical case example is presented which indicates that cost estimates and associated means of production which result from single output costing procedures and from joint costing procedures may be significantly different in a managed forest ecosystem. 相似文献
79.
80.