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891.
Anthony L. Pometto III Kenneth E. Johnson Meera Kim 《Journal of Polymers and the Environment》1993,1(3):213-221
Eleven starch-polyethylene degradable plastic films were prepared from masterbatches from Archer Daniels Midland Inc. (ADM), EcoStar Inc. (SLS), and Fully Compounded Plastic Inc. The biodegradability of initial and 70°C heat-treated materials was determined using a pure-culture assay withStreptomyces badius 252,S. setonii 75Vi2, orS. viridosporus T7A or without bacterial culture (control). Films were treated with 10-foldS. setonii culture concentrates and compared with inactive enzyme controls. Changes in each films mechanical property, molecular weight distribution, and Fourier-transformed infrared spectrum (FT-IR) were determined, and results were evaluated for significant differences by analysis of variance. Cell mass accumulation on each film was quite pronounced. In pure-culture studies, biodegradation was demonstrated for ADM-7 and SLS-2 initial films and for ADM-6 heat-treated films, whereas after 3-week treatment with activeS. setonii culture concentrates (enzyme assay), reductions in mechanical properties and changes in FT-IR spectrum were illustrated by all the films except SLS-2. Thus the absence of biofilm formation on the film surface permitted enzymatic attack of the materials. Furthermore, inhibition of chemical oxidative degradation in the pure-culture assay was demonstrated for ADM-11, SLS-5, and SLS-10 initial materials and for ADM-4, ADM-7, SLS-8, and SLS-10 heat-treated films. These data suggest that biological and chemical degradation were directly affected by the reduction in oxygen tension on the plastic film surface due to cell mass accumulation. This same phenomenon could be the cause for slow degradation rates in nature.Journal Paper No. J-15061 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project Nos. 0178 and 2889. 相似文献
892.
A composite model for the risk assessment is developed for the shallow-land burial of low-level radioactive waste. The composite model is composed of a source term, repository failure model, geosphere model, biosphere model, and finally, a dose-and-health-effects model. Uncertainty and sensitivity analyses are also carried out. In addition to the time-dependent annual release rate and dose rate for each nuclide, the ultimate risk in terms of cancer death rate is estimated.The results show that the highest value of the annual dose for the repository is less than the individual dose limit to the human body, and the calculated highest cancer death rate is much lower than other various risks. The highest value of the total annual dose appears at about 100 years after disposal, and at this time, dominant nuclides are Ni-63 and Cs-137.From the results of uncertainty and sensitivity analyses, it is found that the uncertainty associated with the public risk is strongly sensitive to the volume flow rate and irrigation rate of surface water and the retardation coefficient of geological structure.It is concluded that the methodology of simplified mathematical modeling for the risk assessment can be an effective tool for the decision making of the radioactive waste repository selection and the management of the repository system. 相似文献
893.
Kyehyun Kim Richard H. Hawkins 《Journal of the American Water Resources Association》1993,29(3):449-459
ABSTRACT: Environmental response to acidic deposition results from movement of water through the ecosystem. As a part of the environmental studies for acidic deposition sponsored by the U.S. Environmental Protection Agency (EPA), hydrologic classification based on regional baseflow properties was done. To obtain the amount of baseflow, a flow separation method was developed based on the division of streamflows into “baseflow” and “other” runoff sources. Because of the differences in the flow paths and exposure duration, the two components were assumed to be associated with distinct geo-chemical responses. Individual annual hydrographs were analyzed using 31 separation slopes to determine the amount of baseflow. A total of 1575 streamflow stations in the Northeastern U.S. were analyzed through the access of a long-term daily stream-flow data base. An interactive computer program was developed to obtain baseflow properties and other hydrologic characteristics of each station. The output from this analysis was used to perform cluster analysis to classify streamflow behaviors. The clustering output showed different regional boundaries than those currently used by the EPA for water quality studies. 相似文献
894.
Slobodan P. Simonovic Patrice M. Pelletier Kim D. Barlishen 《Journal of the American Water Resources Association》1988,24(6):1185-1192
ABSTRACT: The problem of determining the optimal route to operate a network of hydrometric gauges within a given area is formulated and solved by an original heuristic traveling salesman algorithm. The algorithm used for solving the problem takes into account the variation of station service time, the eight-hour maximum working day, existence of more than one home base, and the budget constraint. The traveling salesman algorithm is used to solve the optima! assignment problem within a one-day time limit, locating a starting base, stations to visit, and the closest home base. The ending base for the previous day becomes the starting base for the next day, and the assignment procedure is repeated. The computation proceeds from day to day, until all the stations in the considered region are serviced. The solution obtained presents the optimal route to operate a network of hydrometric gauges. The optimization procedure has been applied to the Dauphin hydrometric field area in Manitoba. 相似文献
895.
Seacliff State Beach, along the shoreline of northern Monterey Bay, California, has a well-documented history of repeated destruction and reconstruction of seawalls and park facilities. Seven times in 60 years the timber seawall has been destroyed by winter storm waves and subsequently rebuilt. The deficiencies of the wall, including (a) inadequate attachment of timber lagging to pilings, (b) inability of pilings or lagging to withstand repeated impact of waves and logs, and (c) inadequate height and internal drainage system have never been adequately addressed and each successive wall has essentially been identical to the previously destroyed wall. 相似文献
896.
Kim Neil Irvine John J. Drake 《Journal of the American Water Resources Association》1987,23(6):1017-1025
ABSTRACT: Least squares regression and ARIMA models were developed from suspended sediment data for the Ausable River, Southern Ontario, Canada. A poor correlation between discharge and suspended sediment concentration results from the dynamics of the physical system, including seasonality, antecedent conditions, and hysteresis. Regression model results were significantly improved by the division of the data set into seasons and the addition of simple. but physically meaningful variables. Misleading improvements obtained from the regression of sediment load and discharge are discussed. ARIMA models provided accurate forecasts of sediment concentration on a real-time basis, but the rigorous data requirements limit their use in modeling suspended sediment concentrations in Canadian rivers. 相似文献
897.
The UV photooxidation with Fe(III) and H2O2 was employed to treat a naval derusting wastewater, which contains the high COD
(chemical oxygen demand) and various metal concentrations exceptionally with high concentrations of citric acid and iron. Because
of its iron containment, the Fenton-like reaction automatically took place with the added amount of H2O2. The decomposition rate
was found in a sequence of: UV/H2O2/Fe(III) > UV/H2O2 > Fe(II)/H2O2. Two H2O2 injection methods, single and multiple points,
were evaluated. The multiple-point H2O2 injection was more e cient to decompose the citric acid. The decomposition of the synthetic
citric acid and the real derusting citric acid wastewater was also compared. The 93% COD reduction of the derusting wastewater was
achieved using the UV/H2O2/Fe(III) treatment. 相似文献
898.
899.
After first commercialization in 90's, the applications of diamond-like carbon (DLC) have been significantly expanded to tool, automobile parts, machineries and moulds to enhance wear and friction properties. Although DLC has many advantages like high hardness, low friction electrical insulating and chemical stability and has the possible market, its application in the field is still very limited due to the gaps of understanding between end-user and developer of its advantage of costing. Recently, one of the most popular issues in the surface modification is providing the long lasting super-hydrophilic or -hydrophobic properties on the material surface for the outdoor usage. A lot of material loss is caused due to water corrosion which has to do with the flow and contacts of water like fuel cell separator and air conditioner parts. The consequence of development of functional surface based on the hydrophilic or hydrophobic design for the important parts would be really helpful for materials to be cleaner and more energy effective. Here, we first reviewed the DLC technology and then examined the kind of surface modification as well as its merits and disadvantage. We also looked at how we can improve super-hydrophilic and super hydrophobic for the DLC coating layer as well as current status of technology and arts of DLC. In the end, we would like to suggest it as one of the environmental friendly industrial technology. 相似文献
900.
Choi YH Kang HS Jun I Keum DK Lee H Kim SB Lee CW 《Journal of environmental radioactivity》2007,97(1):20-29
Lysimeter experiments were carried out in a greenhouse to study the fate of HTO following its soil deposition at different growth stages of Chinese cabbage. An HTO solution was applied to the surface of an acidic sandy soil at a time before, and four different times after, sowing. The transfer of HTO to the plants was quantified with the areal transfer factor (TFa, m2 kg(-1)-fresh) defined as the ratio of the plant concentration at harvest to the areal activity deposition. In the four post-sowing applications, the TFa values were in the ranges of 1.6 x 10(-5)-4.9 x 10(-3) for TFWT and 4.5 x 10(-6) -4.3 x 10(-5) for OBT, increasing with a decrease in the time interval between application and harvest. In the pre-sowing application, which was followed by a soil mixing, the TFa values for TFWT and OBT were 1.3 x 10(-4) and 8.6 x 10(-6), respectively. One week after harvest, soil samplings were made for the applications at 26 (A(26)) and 63d (A(63)) after sowing. Peaks of the depth profiles of the soil HTO appeared in the 10-15 cm layer for A(26) and the 5-10 cm layer for A(63). The top 30 cm of soil contained 0.5% and 20% of the applied activity for A(26) and A(63), respectively. Negligible fractions seemed to be in the deeper zone. It was estimated that almost all or most of the applied HTO had escaped to the air before plants' harvest. 相似文献