Effect of dissolved humic matters on the leachability of PCDD/F from fly ash--laboratory experiment using Aldrich humic acid

The effect of dissolved humic matters (DHM) on the leachability of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) in fly ash was studied theoretically and in laboratorial condition to verify the previous results for pilot and field experiment of incineration residues landfill. In theoretical review, it was shown that DHM could influence the actual solubility and leachability of PCDD/F. The higher concentration of DHM showed the higher leachability of PCDD/F. In the leaching test, three different DHM concentrations and pHs of solutions were adopted to fly ash samples imaging the various characteristics of municipal solid waste leachate. It was proved experimentally that the leachability of PCDD/F increased with increasing DHM concentration in all pH conditions. The highest leachability was shown at the highest pH. Isomer distribution patterns of PCDD/F in all leachates were similar in all pH conditions. It backed up the distribution theory of PCDD/F between DHM and water.     

Anaerobic digestion of polyelectrolyte flocculated waste activated sludge

This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge. Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests. The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge. The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one. In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined. For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively. The role of flocculants could change in different stages of digestion.The dosed polymers had no apparent toxicity to the inoculum used. The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge. Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion. Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge.     

Determination of mutagenic potential and organic contaminants of Great Lakes drinking water

Extracts of organic compounds were obtained, using XAD-2 macroreticular resin, from drinking water supplies in 12 Great Lakes municipalities. The extracts were tested for mutagenic potential using the Salmonella/mammalian-microsome assay and analysed for organochlorine pesticides, polyaromatic hydrocarbons, organophosphorous pesticides and trialkyl-arylphosphates. Grab samples of drinking water were also analysed for volatile organic compounds. Dose-related increases in mutagenicity were found in extracts from 11 of the drinking water supplies.     

Water transformation in the media of biofilters controlled by Rhodococcus fascians in treating an ethyl acetate-contaminated airstream

Biofilters do not provide much water for bacteria to grow. To use them efficiently and properly, it is essential to understand the kinetics of water transformation and to control moisture levels. This study aims to clarify whether the metabolism of microorganisms will improve the water-holding capacity of media or will intensify drying. This experiment was conducted in duplicate, that is, both with and without bacterial inoculation. Both the constant water content mode and the declining water content mode show that microbial growth in a log phase will enhance drying. In contrast, the bacteria growing in a logarithmic decline phase will improve water-holding capacity. Basically, water evaporation can result from the latent heat obtained from microbial respiration or from the physical temperature difference between the unsaturated air and the wet media. Two ways that biofilters can gain water are from water incorporated into bacteria cells and from water obtained from the oxidation of volatile organic compounds (VOCs).     

Sustainable soil management practices and quality of potato grown on erodible lands

Land productivity can decline when top soil is lost. In Kentucky, limited resource farmers often produce vegetable crops on erodible lands. The objectives of this study were 1) to quantify the impact of three soil management practices (SMPs) on quantity of potato produced on erodible land, 2) to evaluate the impact of pyrethrin and azadirachtin insecticides on potato tuber quality, and 3) to assess the impact of yard waste compost on the chemical composition (ascorbic acid, free sugars, phenol contents) of potato tubers. Potatoes (Solanum tuberosum L. cv. Kennebec) were grown in a silty loam soil of 10% slope. Plots (n= 18) were 3.7 m wide and 22 m long (10% slope), with metal borders of 20 cm above ground level. Two botanical insecticides, Multi-Purpose Insecticide (containing pyrethrin 0.2%) and Neemix 4EC (containing 0.25% azadirachtin) were sprayed twice on potato foliage during each of two growing seasons (1997 and 1999) at the recommended rates of 6 lbs and 2 gallons.acre(-1), respectively. The SMPs were tall fescue strips (FS) intercropped between each two potato rows, soil mixed with yard waste compost (COM) and no-mulch (NM) treatment (roto-tilled bare soil). The experimental designwas a 2 x 3 x 3 factorial with main factors of two insecticides and three SMPs replicated three times. Average potato yield was lowest in NM and FS and highest in COM treatments. Yield obtained from the bottom of the plots was greater than that obtained from the top of plots. Tuber defects (rot, scab, sun green, hollow heart, necrosis, and vascular discoloration) were significantly different between the two growing seasons. The two insecticidal treatments did not have much influence on potato yield or tuber defects. Tubers obtained from tall fescue treatments had low levels of ascorbic acid and reducing sugars compared to compost treatments.     

Quantification of the dissolved organic matter effect on the sorption of hydrophobic organic pollutant: application of an overall mechanistic sorption model

This study presents an overall sorption model to estimate the sorption equilibrium coefficients of hydrophobic organic pollutants for heterogeneous aquatic systems. This proposed model combines a series of sorption equilibrium relationships including the adsorption of dissolved organic matters on particulates, the binding between organic pollutants and dissolved organic matters, and the sorption of organic pollutants on particulates with or without the presence of dissolved organic matters. By using this model, variations among the sorption equilibrium coefficients with the concentrations of dissolved organic matters are obtained. Also discussed herein are case studies involving pollutants having a wide spectrum of K(ow)s, different types of dissolved organic matters, different pH values and ionic strengths. In most of the case studies, the sorption equilibrium coefficients initially increase with the-concentrations of dissolved organic matters and, then, decrease after reaching a maximum value. This study also addresses the relative errors of partition coefficients attributed to the negligence of the effect caused by the dissolved organic matter, the so-called third-phase effect.     

Use of oyster, Crassostrea gigas, and ambient water to assess metal pollution status of the charting coastal area, Taiwan, after the 1986 green oyster incident

Most of the oyster mariculture beds in Taiwan are in areas located along the west of the island. One of these areas is the Charting coast, where green oysters were found in 1986. During this incident, which became internationally notorious, mass mortality occurred in the Charting oyster beds. After this discovery, measures were taken by the authorities to counter pollution which lead to the problem. The effectiveness of these pollution control actions was evaluated in this study. Two water column indicators, particulate and sediment, and oysters were sampled and analyzed for metals (Cu, Zn, Pb, Ni) in Charting and its neighboring areas, Kuen-Shen Lake and Shin-Da Harbor, and the control area/station, Dah-Pen Wan. The current study shows that copper and zinc concentrations in both oysters and particulates significantly decreased in the Charting area, compared with concentrations found during the period of the green oyster incident. Six years after the incident, the copper concentration in oysters had fallen from a high of 4400 μg/g dry weight to an average of 300±69 μg/g dry weight, figures similar to the copper concentration in 1982. The pollution control actions taken after the incident are believed to be the cause of this recovery of the coastal environment. Nevertheless, Charting still produced oysters with the highest copper and zinc concentrations among the areas investigated. Further measures currently being taken by the government, including removing the sediment of some portions of Erhjin Chi, should be able to bring the oyster copper concentrations down to the levels similar to those observed in the neighboring area, (average concentration below 200 μg/g dry weight or all time maximum concentration below 500 μg/g dry weight).     

Rapid reductive destruction of hazardous organic compounds by nanoscale Fe0

Fe0-mediated reductive destruction of hazardous organic compounds such as chlorinated organic compounds (COCs) and nitroaromatic compounds (NACs) in the aqueous phase is one of the latest innovative technologies. In this paper, rapid reductive degradation of COCs and NACs by synthesized nanoscale Fe0 in anaerobic batch systems was presented. The nanoscale Fe0, characterized by high specific surface area and high reactivity, rapidly transformed trichloroethylene (TCE), chloroform (CF), nitrobenzene (NB), nitrotoluene (NT), dinitrobenzene (DNB) and dinitrotoluene (DNT) under ambient conditions, which results in complete disappearance of the parent compounds from the aqueous phase within a few minutes. GC analysis reported that the main products of the dechlorination of TCE and CF were ethane and methane as well as that most of the nitro groups in NACs were reductively transformed to amine groups. These results suggest that the rapid reductive destruction by nanoscale Fe0 is potentially a viable in situ or aboveground treatment of groundwater contaminated with hazardous organic compounds including COCs and NACs.     

PCBs fires: Correlation of chlorobenzene isomer and PCB homolog contents of PCB fluids with PCDD and PCDF contents of soot

PCBs, PCDDs, and PCDFs are subject to new regulations promulgated under the Toxic Substances Control Act and the Resource Conservation and Recovery Act. The finding of PCDDs and PCDFs in PCBs could restrict disposal options for PCBs. A review of major fire incidents in the U.S., indicates that PCDDs have been found only in the Binghamton, N.Y., transformer fire incident. Laboratory combustion studies further support PCDFs formation from PCBs and PCDDs from chlorobenzenes. No PCDDs were found in analyses of fluids from transformers involved in transformer fire incidents. PCDFs do not appear to increase in PCBs askarel fluids from normal usage in electrical equipment.     

Control targets for the management of biological systems

Attention is focused on biological systems which are describable in terms of ordinary differential equations subject to human control inputs. The concept of an isochronal system is introduced in order to include systems for which the differential equations are valid only over regularly reoccurring time intervals.It is assumed that the control inputs are to be chosen so that an integral cost function of the state of the system, the control used, current time, and the time interval of the control program is minimized. Problems associated with minimizing this cost function over an infinitely long time interval is then considered. Difficulties inherent with minimizing a cost integral on an infinite time interval are shown to be avoided by minimizing an average of the cost function over an unknown but periodic time interval. Under proper circumstance, the optimal control program for the average cost function is either identical to or a good approximation to the optimal control program for the original cost function over an infinitely long time interval.Necessary conditions are obtained for minimizing an average cost function over an unspecified time interval subject to the system equations. For a given problem the necessary conditions will yield but a single system trajectory in the state space. For management purposes this trajectory may be thought of as a target to which the system should be driven and maintained.A number of examples illustrate the use of the necessary conditions to obtain control targets. Certain problems associated with the stability of the target solutions are illustrated with the examples.