Prolonged toxicity characteristic leaching procedure for nickel and copper aluminates

The toxicity characteristic leaching procedure (TCLP) is a regulatory testing method widely employed to evaluate the environmental friendliness of waste materials. TCLP analysis provides a fast, easy and economical way to determine the mobility of waste pollutants under simulated landfill conditions. Recent studies on metal stabilization have reported the potential for nickel and copper aluminates to form in thermal treatment conditions, and suggested a more reliable method of stabilizing hazardous metals, particularly when products are to be reused. There is thus an urgent need for a convenient and effective method of quantifying metal leachability and identifying the metal leaching behavior of sparingly soluble materials. In this study, standard TCLP analysis was modified into a prolonged leaching experiment to investigate the leaching behavior of nickel and copper oxides (NiO and CuO) and their aluminates (NiAl(2)O(4), CuAl(2)O(4) and CuAlO(2)). The results demonstrate the difficulty of differentiating the leachability of highly insoluble phases, such as NiO and NiAl(2)O(4), using the standard TCLP. The prolonged TCLP method, however, confirmed NiAl(2)O(4) to have a lower degree of intrinsic leachability than NiO and that it could be expected to undergo congruent dissolution under landfill conditions. For the more soluble copper system, the aluminates were still found to possess a much lower degree of leachability, and their leaching behavior to follow an incongruent dissolution pattern. The results of this study prove prolonged TCLP analysis to be a convenient and effective way to evaluate the environmental friendliness of metal waste and to identify the leaching behavior of waste materials.     

Exposure and health-risk assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) for sinter plant workers

This study was set out to assess polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) exposures and health-risk impact posed on sinter plant workers. One sinter plant located in southern Taiwan was selected and their workers were divided into four exposure groups based on their work tasks, including raw material charging workers, sintering grate workers, shredding workers, and others. Results show that their mean total PCDD/F and the corresponding total I-TEQ exposure levels shared the same trend as: shredding workers>others>sintering grate workers>raw material charging workers. For all selected exposure groups, their PCDD/F exposures were dominated by the particle phase contents. Congener profiles of the gaseous+particle phase PCDD/Fs were found with more fractions of high chlorinated congeners than low chlorinated congeners. The lifetime average daily doses (LADDs) and their resultant excess cancer risks (ECRs) found for sinter plant workers were higher than those residents living at the residential area and rural area, but were lower than those living at the nearby of the selected sinter plant, urban area, industrial area. Considering ECRs of the sinter plant workers were still higher than 10(-6) suggesting the need for adopting proper control measurements for reducing workers' PCDD/F exposures, particularly for those sinter zone workers.     

Biodegradable nanocomposites based on poly(butylene succinate)/organoclay

In this work, we try to incorporate the inorganic system into the biodegradable polymers to compose an organic/inorganic polymer hybrid. Various nanocomposites of poly(butylene succinates) (PBS) with different ratios of organically modified layered silicates (OMLS) prepared by solution blending were investigated. The OMLS used for the preparation of nanocomposites were functionalized ammonium salts modified montmorillonite. The effects of OMLS on the nanocomposites were investigated by XRD, TEM, DMA and TGA in the aspect of the d-spacing of clay, mechanical and thermal properties. Interestingly, all these nanocomposites exhibited improved properties when compared with the pristine PBS sample. XRD indicates that the layers of clay were intercalated by the modifiers, and the interlayer distance of organoclay in the nanocomposites could be extended to about 29.4 Å. Moreover, the thermal stability of the nanocomposites was enhanced by the addition of organoclay via TGA study, closely related to the organoclay content in the PBS matrix. DMA data shows that the storage and loss moduli were concurrently enhanced by the addition of organoclay as compared to the pristine PBS sample. Moreover, the glass transition temperatures also increased about 5 to 20 °C (from DMA, peak of tanδ) for the various organoclay-containing samples. The enhanced mechanical and thermal properties can be achieved from these organoclay modified-nanocomposites.     

IMPACT OF WATER CUTBACK ON SUGARCANE PRODUCTION IN THE FLORIDA EVERGLADES1

ABSTRACT: Sugarcane (Saccharum spp.) was planted in six lysimeters containing Pahokee muck (Lithic Mediaprist) where water tables were maintained at 30, 60, and 90 cm depths. The main objective was to study the impact of a 40 percent water cutback (108 mm) on sugarcane production during the period near the end of the dry season (i.e., May). The water cutback treatment was simulated through manipulation of water table depth. Due to the high available water capacity of the muck soil and selection of a sugarcane cultivar ‘CP63-588’ (which has a high tolerance of water table fluctuations), the sugarcane growth, and the yields of sugarcane biomass and sugar were not significantly different as a result of the treatments with and without 40 percent water cutback during a period of two months. This result is in good agreement with the 1981 cane yield in the Everglades Agricultural Area where a 35 percent water cutback was imposed during the 1981 drought.     

GENERATION OF SYNTHETIC AND MISSING CLIMATIC DATA FOR PUERTO RICO1

ABSTRACT: Climatic data such as temperature, solar radiation, relative humidity, and wind speed have been widely used to estimate evapotranspiration. Moat of the solar radiation data and portions of the relative humidity data are either not available or missing from the records in Puerto Rico. Depending upon the availability and data characteristics of records, three methods (including a regression technique, an averaging of historical data, and a regional average) were used to generate missing data, and a time series analysis was used to synthesize a series of climatic data. The limitations and applicability of each method are discussed. The results showed that the time series analysis method can be successfully used to synthesize a series of monthly solar radiations for several stations. The regression technique and the regional average can be successfully applied to generate missing monthly solar radiation data. The regression technique and the averaging of historical data have been satisfactorily used to interpolate missing monthly relative humidity. The explained variance (R²) varied from 0.68 to 0.88, which are both significant at the 0.05 level of significance.     

SUBJECTIVE DECISION-MAKING FOR URBAN WATER RESOURCES DEVELOPMENT1

ABSTRACT: Bayesian decision theory provides a procedure for the use of subjective data in a decision-making situation related to urban water resources development. This procedure is effectual in pursuing a set of goals and in transforming individual or group indecisiveness into satisfactory decisions. This approach is highlighted due to its capability to incorporate seemingly unquantifiable, abstract factors into the decision-making process. It is realized that the soliciting of expert and general public opinion is indispensable in making choices for the welfare of the general public from alternative courses of action under uncertainty. The analysis presented here considers engineering alternatives, quality, quantity, cost and the intangible public response in an integrated effort for the selection of optimum strategies in urban water resources development.     

USING CROP YIELD AND EVAPOTRANSPIRATION RELATIONS FOR REGIONAL WATER REQUIREMENT ESTIMATION1

ABSTRACT: Values of dry biomass of corn, sugarcane, sorghum, rice, taro, millet, cotton, cowpeas, soybeans, and velvet beans as related to the evapotranspiration (ET) were studied. The linear regression model was sufficiently accurate to establish the crop dry biomass and ET relations. A water-use efficiency index (WUE), which is defined as the additional crop dry biomass per unit ET, is used in this study. The WUE were grouped into high, medium, and low categories. The WUE varied from greater than 35 kg ha^-1/mm for the high category, between 15 and 35 kg ha^-1/mm for the medium category, and less than 15 kg ha^-1/mm for the low category. Application of the established model to the Everglades Agricultural Area, Florida, showed that the regional El can be predicted from the known regional crop yields. The crop yield and ET relations could be used as a potential tool to improve water resources planning and management practices for crop production.