Hazardous Residues Research Articles

Metal Precipitation in Two Landfill Leachates

Leachate from solid‐waste landfills poses a significant environmental threat to groundwater supplies, warranting capture and treatment. Treatment prior to biological co‐production to reduce heavy metal concentrations via sorption onto in situ precipitated hydrous ferric and manganese oxides may provide adequate reductions while minimizing hazardous residuals. This investigation studied the partitioning of cadmium, copper, zinc, and nickel with iron and manganese solid phase formed from leachate constituents at pH 9. Batch‐type partitioning experiments were conducted using sodium hydroxide and calcium hydroxide for pH control. Naturally produced leachate was obtained from the Snohomish County and King County solid‐state disposal facilities in Washington state. The cadmium‐sorbent ratios of this investigation were well below those found by previous researchers; however, removal rates were somewhat below those found in organic‐free systems. These lower removal rates might be attributed to the “complexation” of cadmium by leachate organic constituents. Copper‐sorbent ratios were also well below those found by previous researchers; conversely, removal rates were significantly below those found for organic‐free systems. Lower copper removal rates could be attributed to the complexation by organics and the formation of uncharged and negatively charged species at pH 9. Zinc‐sorbent ratios were much higher than those found by previous researchers; however, removal rates were similar. The mechanism of zinc partitioning was probably the formation of a zinc oxide solid phase. Nickel‐sorbent ratios were well below those found by previous researchers, while removal rates were far below those of organic‐free systems. Lower nickel removal rates cannot be attributed to either organic complex formation or speciation effects.

Studies of forest floor biological activities in an area previously damaged by sulphur dioxide emissions

As part of an environmental control program aimed to assess possible future effects of air contaminants from a new destruction plant for hazardous chemical residuals in Central Sweden, a study was undertaken the year before the plant went into operation to collect base-line information on biological activities in the soils of the surrounding forests. Measurements were made of N-mineralization, respiration, phosphatase-, dehydrogenase-, and nitrogenase activity on sieved samples from the forest floor (0 to 3 cm).

Waste Generation Reduction: A First Step Toward Developing a Regulatory Policy to Encourage Hazardous Substance Management through Production Process Change

From an engineering perspective, the issue of hazardous chemical wastes is no different than the air, water, and workplace pollution issues with which the nation has long grappled. Quite simply, hazardous residues are a production process problem; the nature and amount of the residues produced are determined by the nature of the production processes employed. The long-term goal of a reasoned hazardous waste management policy must be to effect changes in industrial processes so as to reduce significantly the amount of hazardous residues generated by those processes. This goal will not be reached unless industry itself is motivated to explore the necessary technological innovation and adaptation. The challenge, then, is to create a regulatory climate which provides such motivation. We believe that the development of effective regulatory policies at the state level to encourage production process change will require a commitment to overall hazardous substance management, rather than to the management of hazardous residues deposited into any particular environmental medium. If state hazardous waste policies are to serve as a focal point for hazardous substance management, they must incorporate: (1) a specific programmatic emphasis on waste generation reduction as the preferred means of hazardous waste management; (2) vigorous enforcement of current treatment and disposal laws; (3) a shift in emphasis from the nature of the various waste streams that are produced to the nature of the various industrial "productive segments" that generate hazardous waste; (4) refinement and expansion of programs for the sharing of technological information; and (5) a graduated increase in regulatory stringency over time.

Mixing alternatives for the polyester microencapsulation process for immobilization of hazardous residuals

The evaluation of two mixing methods, as alternatives to impeller mixing in the polyester immobilization of hazardous residuals, is described. These are (1) emulsification of the toxic waste solution into the polyester resin by air sparging and (2) mixing of neat polyester resin with volume reduced wastes in a rotary drum type mixer. The evaluation in the first method is in terms of time for emulsification, viscosity and droplet size distribution, and time for emulsion curing, as compared to low- and high-speed impeller mixing. In the second method, the discussion is limited to the time and nature of solidification.

The disappearance of chlorobromuron in ensilage

Chlorobromuron, 3-(4-bromo,3-chlorophenyl)-l-methoxy-l-methylurea is a preemergent and postemergent herbicide used for the control of many annual broadleaf weeds and grasses in field corn and soybean production. Both corn and soybeans are very common forage crops used for ensilage production and feeding to farm animals. The ensilage process involves a fermentation wherein the aerobic organism utilize quickly the available oxygen in the silo causing the atmosphere to become anaerobic allowing the fermentation and subsequent acid production to proceed. Hence the procedure is a preservative measure minimizing putrefication. In practice, corn plants, including stalk, leaves and ears, or mixtures of corn plants, legumes, soybeans or other grasses are chopped and packed into air-tight silos. The period of 48-72 hours is one of great fermentive activity with the production of considerable heat and pressure. The organisms responsible for the fermentation are streptococci and lactobacilli producing lactic acid, butyric, propionic and acetic acid with small amounts of alcohol. A pH of 5.2 or less is generally necessary to prevent decomposition of the ensilage. As is common with most, if not all chemicals used in crop production, small but measurable amounts of herbicides and/or their metabolic products are present as residues in plant materials. Because of the great importance in assessing the potential for the production of hazardous substances or unwanted residues, a study of the stability of chlorobromuron in the ensilage process was undertaken. Materials

Evaluation of Insecticides for Control of the Pickle worm on Summer Squash1

Four experiments, beginning in 1963, were conducted at Gainesville, Florida, to evaluate insecticides for control of Diaphania nilidalis (Stoll) on summer squash. Carbaryl consistently gave as good or better control than other materials tested. Lindane, endosulfan, and trichlorfon also gave good control although trichlorfon was not so consistent. Monsanto CP-47114 (O,O-dimethyl O-4-nitro-m-tolyl phosphorothioate) at 1 1b active per acre gave excellent control and should be tested further, furadan® (2, 3-dihydro-2, 2-dimethyl-7-bellzofuranyl methylcarbamate) and Ortho 9006 (O, S-dimethyl phosphoramidothioate), both systemics, also gave good control, but they are not likely to be recommended for usc on squash, unless it can be shown that they are rapidly degraded and will not leave hazardous residues.

The gas chromatographic determination of organo-phosphorus pesticides : Part II. A comparative study of hydrolysis rates

The hydrolysis rates of organophosphorus pesticides are dependent upon their chemical structure and in pH 6.0 buffered solutiosn at 70° range from half lives of 0:5 h to 4.0 days and longer still for phosphoramidates. At 20° the rates are several hundred times slower. Oxidation of pesticides, where possible, usually results in decreased stability. Compared to the highly stable organochlorine pesticides the toxic phosphorus esters are undoubtedly less persistant, however, the rates of decomposition under uncatalyzed conditions are still relatively slow. Contamination of surface waters by accident or misuse could result in long-lived and potentially hazardous residues.

Systemic Insecticides for Theobroma cacao L., Their Translocation and Persistence in Foliage and Residues in Cacao Beans1

From preliminary screening of 14 systemic compounds with cacao seedlings in Costa Rica, Thimet, Chipman R-6200 ( 0,0 -diethyl S-(2-diethylamino)ethyl phosphorothiolate), demeton, Isolan and dimefox were selected for further study. These five systemics were compared on the basis of their translocation and persistence in the foliar parts of mature cacao trees after trunk implantation, their effect on the flavor of chocolate produced from beans from the treated trees, and the level and nature of residues in the beans using radiotracer and anticholinesterase methods of analysis. Thimet and Chipman R-6200 were readily translocated into the foliar portions of cacao trees and persisted for as long as 20 months after a single implantation treatment. Little or no residues were found in the cacao beans at any time after treatment regardless of the pod position on the trees in relation to the site of implantation. Studies with radioactive R-6200 demonstrated a high concentration of phosphorus-containing residues in the cotyledons of the cacao beans but these materials did not partition into chloroform and did not inhibit cholinesterase and therefore cannot be considered as hazardous residues. No off flavors were detected in chocolate from beans harvested from any of the systemic treatments but definite off-flavors were obtained when BHC was used as a foliar spray. The insecticidal efficiency of the systemics was not studied because the insect populations in the treated areas were not adequate for this purpose.