An equivalence factor between CO2 avoidedemissions and sequestration – description andapplications in forestry

Concern about the issue of permanence andreversibility of the effects of carbon sequestrationhas led to the need to devise accounting methods thatquantify the temporal value of storing carbon that hasbeen actively sequestered or removed from theatmosphere, as compared to carbon stored as a resultof activities taken to avoid emissions. This paperdescribes a method for accounting for the atmosphericeffects of sequestration-based land-use projects inrelation to the duration of carbon storage. Firstly,the time period over which sequestered carbon shouldbe stored in order to counteract the radiative forcingeffect of carbon emissions was calculated, based onthe residence time and decay pattern of atmosphericCO₂, its Absolute Global Warming Potential. Thistime period was called the equivalence time, andwas calculated to be approximately 55 years. From thisequivalence time, the effect of storage of 1 tCO₂ for 1 year was derived, and found to besimilar to preventing the effect of the emission of0.0182 tCO₂. Potential applications of thistonne.year figure, here called the equivalencefactor, are then discussed in relation to theestimation of atmospheric benefits over time ofsequestration-based land use projects.     

Feeding and associated electrical behavior of the Pacific electric ray Torpedo californica in the field

The predatory behavior of 74 Pacific electric rays (Torpedo californica), studied between August and December during 1988 through 1991 in situ off the Palos Verdes Peninsula, southern California, consisted of two feeding modes: an ambush from the substratum during the day and a more vigorous attack from the water column at night. Predatory motor patterns and electric organ discharges (EODs) were recorded on the video and audio channels of a housed camcorder. Predatory motor patterns included four phases: (1) jump (simultaneous with EOD initiation), (2) pectoral-fin cupping, (3) orientation to prey, and (4) ingestion. The initial electrical activity of the rays was a train of 46 to 414 5-ms monophasic EODs that lasted 0.45 to 7.06 s; the maximum number of EODs produced during an attack was >1200. Maximum output, measured on only one ray, was 45 V. Fifty-five rays were presented one of four types of prey stimuli: live fish (LF), freshly-speared fish (FSF), frozen fish (FF), or a simulated bioelectric field (SBF). The percent frequency of attacks for the LF, FSF, and FF treatments ranged from 70 to >90%, but was <30% for the SBF. The interval between prey presentation and attack was 30 s for the LF, FSF, and FF and over five times longer for the SBF; intervals averaged <4 s for the three rays tested at night. Attacks by rays on energized electrodes provide the first evidence that electric rays use electroreceptors to detect their prey. However, the lack of clear differences among the four prey treatments in five characteristics of the initial pulse train suggests that a suite of sensory stimuli cooperate in triggering an attack and regulating the electrical output during the attack.     

Availability of phosphorus to algae from eroded soil fractions

A study was conducted to determine the concentrations of algal-available P (P_aa) in unfractionated samples and size-classified separates of soil eroded from wheat stubble plots during a simulated rainfall experiment conducted in Warren County, Indiana, U.S.A. Run-off samples were collected, concentrated, dispersed by sonification, separated according to size and incubated with algal cells (Selanastrum capricornutum) in P-free nutrient medium for 2 weeks. Algal-available P in soil separates was determined by decreases in sediment inorganic P (P_i) over the incubation period. The initial concentrations of dissolved molybdate-reactive P_i (DMRP), P_i extractable with NaOH (NaOH-P_i), P_i extractable with HCl (HCl-P_i), organic P (P_o, and total P increased with decreasing particle size. A higher proportion of P_i was HCl-extractable in fractions > 2 μm than in clay-size separates. The level of P_aa in samples increased with decreasing particle size. Available P concentrations in separates < 0.2, 0.2–2, 2–50, > 50 μm and unfractionated samples averaged 447, 282, 113, 26 and 261 μg g^?1, respectively. From 42 to 69% of the P_i and 20–37% of the total P in unfractioned samples was P_aa. A lower proportion of P_i in the > 50 μm fraction was P_aa than in the other size fractions (34 vs. 50%). There was no relationship between particle size and the proportion of total P that was available. The majority (> 84%) of P_aa originated in the P_i fraction extractable with NaOH, whereas HCl-P_i only contributed small amounts of P_aa. The proportion of initial NaOH-P_i assimilated by algae in 2 weeks ranged between 43 and 77%, whereas an average of 16% of HCl-P_i in separates was P_aa. On average, a greater proportion of NaOH-P_i was assimilated by algae in samples from no-till plots as compared to those from chisel-plowed plots.     

Housing values,census estimates,disequilibrium, and the environmental cost of airport noise: A case study of Atlanta

Two unresolved issues about airport noise-property value studies are addressed. The first issue concerns the comparability of empirical results from aggregate census data vs individual sales values, and the second issue concerns the homogeneity and stability of results from housing price studies over time and across markets. Hedonic price models from two sets of data for a residential area near the Atlanta International Airport are estimated at two points in time 1979–1980 and 1970–1972. The available data yield similar estimates of the noise discount over time, and from the prices of individual house sales vs owner-appraised census block aggregates.     

Cystic fibrosis prenatal diagnosis: Confirmation of an equivocal microvillar enzyme result by direct analysis of the common gene mutation

A child was tentatively diagnosed as having cystic fibrosis, based on neonatal presentation with severe gastrointestinal complications; the diagnosis was not confirmed biochemically and no tissues were available for DNA analysis. The mother presented in her subsequent pregnancy, and microvillar enzyme analysis of cell-free amniotic fluid at both 18 and 20 weeks gestation gave equivocal results. The pregnancy was terminated voluntarily because of a trend towards abnormal enzyme assay results on the second amniocentesis. Retrospectively, fetal tissues were found to be homozygous for the most common mutation of the cystic fibrosis gene (AF₅₀₈), which confirmed the prenatal assessment and suggested that the first infant of the couple was probably also affected by the disease.     

An evaluation of the tapered element oscillating microbalance method for measuring diesel particulate emissions

We determined the usefulness of tapered element oscillating microbalances (TEOMs) for researchers and engineers involved with measuring diesel particulate mass. Two different test facilities were used for generating diesel particulates and comparing the TEOM to the commonly used U.S. Environmental Protection Agency (EPA) manual filter method. The EPA method is very labor-intensive and requires long periods of time to complete. The TEOM is an attractive approach because it has the potential to reduce the amount of time and labor required in diesel testing, as well as to provide real-time particulate-mass data that are not obtainable with the EPA method. It was found that the TEOM was a precise and easy-to-operate instrument that could measure the mass concentration (MC) of diesel particulate emissions in real time. Although the TEOM diesel particulate MC measurements were highly correlated with the manual filter measurements, the two techniques were not equivalent because the TEOM consistently reported MC results that were 20-25% lower than those obtained using the manual filter technique. In conclusion, the TEOM can be used to increase test-cell throughput and to measure transient values of diesel particulate emissions at sites performing diesel-engine testing. However, unless EPA is able to certify the TEOM as an equivalent method, it cannot replace the manual filter method for diesel certification work.     

Development of emission factors for polycarbonate processing

Emission factors for selected volatile organic compounds (VOCs) and particulate emissions were developed while processing eight commercial grades of polycarbonate (PC) and one grade of a PC/acrylonitrile-butadiene-styrene (ABS) blend. A small commercial-type extruder was used, and the extrusion temperature was held constant at 304 degrees C. An emission factor was calculated for each substance measured and is reported as pounds released to the atmosphere/million pounds of polymer resin processed [ppm (wt/wt)]. Scaled to production volumes, these emission factors can be used by processors to estimate emission quantities from similar PC processing operations.     

Transformation products distribution of atrazine in corn plants treated with radiolabelled herbicide

Roots of whole plants at four leaf stage grown in specialized soil treatment vessels were treated with ¹⁴C-atrazine. Plant tissues were exhaustively extracted with methanol and extracts were separated by preparative thin layer chromatography (TLC). The extracted material was separated in two TLC bands at Rf0.00 and Rf0.18 containing 33% and 67% of plant ¹⁴C-residues, respectively. Methanol extracts of these bands subjected to derivatization, hydrolysis and analysis by TLC, revealed the presence of a number of transformation products consisting of hydroxy analogues of atrazine and their dealkylated metabolites. The transformation products had variable distribution patterns amongst leaf, stalk and root tissues. Diaminohydroxyatrazine, hydroxyatrazine, and deethylhydroxyatrazine were the main ¹⁴C-residues. Stalk tissue contained more ¹⁴C-residues which were largely located at and just below the ligule. The significance of ¹⁴C-residue accumulation at the ligule and the transformation product compartmentalization are discussed.     

WATER QUALITY MODEL OUTPUT UNCERTAINTY AS AFFECTED BY SPATIAL RESOLUTION OF INPUT DATA1

ABSTRACT: Resolution of the input GIS data used to parameterize distributed‐parameter hydrologic/water quality models may affect uncertainty in model outputs and impact the subsequent application of model results in watershed management. In this study we evaluated the impact of varying spatial resolutions of DEM, land use, and soil data (30 × 30 m, 100 × 100 m, 150 × 150 m, 200 × 200 m, 300 × 300 m, 500 × 500 m, and 1,000 × 1,000 m) on the uncertainty of SWAT predicted flow, sediment, NO₃‐N, and TP transport. Inputs included measured hydrologic, meteorological, and watershed characteristics as well as water quality data from the Moores Creek watershed in Washington County, Arkansas. The SWAT model output was most affected by input DEM data resolution. A coarser DEM data resolution resulted in decreased representation of watershed area and slope and increased slope length. Distribution of pasture, forest, and urban areas within the watershed was significantly affected at coarser resolution of land use and resulted in significant uncertainty in predicted sediment, NO₃‐N, and TP output. Soils data resolution had no significant effect on flow and NO₃‐N predictions; however, sediment was overpredicted by 26 percent, and TP was underpredicted by 26 percent at 1,000 m resolution. This may be due to change in relative distribution of various hydrologic soils groups (HSGs) in the watershed. Minimum resolution for input GIS data to achieve less than 10 percent model output error depended upon the output variable of interest. For flow, sediment, NO₃‐N, and TP predictions, minimum DEM data resolution should range from 30 to 300 m, whereas minimum land use and soils data resolution should range from 300 to 500 m.