Sulfur polymer solidification/stabilization of elemental mercury waste

Elemental mercury, contaminated with radionuclides, presents a waste disposal problem throughout the Department of Energy complex. In this paper we describe a new process to immobilize elemental mercury wastes, including those contaminated with radionuclides, in a form that is non-dispersible, will meet EPA leaching criteria, and has low mercury vapor pressure. In this stabilization and solidification process, elemental mercury is combined with an excess of powdered sulfur polymer cement (SPC) and sulfide additives in a mixing vessel and heated to approximately 40 degrees C for several hours, until all of the mercury is converted into mercuric sulfide (HgS). Additional SPC is then added and the temperature of the mixture raised to 135 degrees C, resulting in a molten liquid which is poured into a mold where it cools and solidifies. The final treated waste was characterized by powder X-ray diffraction and found to be a mixture of the hexagonal and orthorhombic forms of mercuric sulfide. The Toxicity Characteristic Leaching Procedure was used to assess mercury releases, which for the optimized process averaged 25.8 microg/l, with some samples being well below the new EPA Universal Treatment Standard of 25 microg/l. Longer term leach tests were also conducted, indicating that the leaching process was dominated by diffusion. Values for the effective diffusion coefficient averaged 7.6x10(-18) cm2/s. Concentrations of mercury vapor from treated waste in equilibrium static headspace tests averaged 0.6 mg/m3.     

Alaska’s Freshwater Resources: Issues Affecting Local and International Interests1

Alessa, Lilian, Mark Altaweel, Andrew Kliskey, Christopher Bone, William Schnabel, and Kalb Stevenson, 2011. Alaska’s Freshwater Resources: Issues Affecting Local and International Interests. Journal of the American Water Resources Association (JAWRA) 47(1):143‐157. DOI: 10.1111/j.1752‐1688.2010.00498.x Abstract: The State of Alaska faces a broad range of freshwater challenges including limited resource access in rural communities, increasing freshwater use, and a pressing need to better understand and prepare for climate‐driven change. Despite these significant issues, Alaska is relatively water‐rich and far more equipped to address its water resource concerns compared with other regions of the world. Globally, simultaneous and rapid water stresses have influenced and complicated conflicts and are motivating nations to develop markets and trade as one of the primary means to manage their needs for this resource. This paper presents these interacting issues in the context of Alaska’s relationship with a world undergoing significant social and ecological changes that affect freshwater supplies. We present the challenges faced by Alaska in the context of a larger global perspective, and briefly explore the relative effects these issues have on local, regional, and global scales. We present the argument that Alaska needs to develop more robust institutions and policies that can alleviate both household concerns and ensure that Alaska plays a significant role in the international freshwater arena for its long‐term resilience.     

Ionic liquids for post-combustion CO2 absorption

The present work is a study to evaluate ionic liquids as a potential solvent for post-combustion CO₂ capture. In order to enhance the absorption performance of a CO₂ capture unit, different ionic liquids have been designed and tested. The main goal was to get a comparison between a reference liquid and selected ionic liquids. As the reference, a solution of 30 w% monoethanolamine (MEA) and water was used. A large range of different pure and diluted ionic liquids was tested with a special screening process to gain general information about the CO₂ absorption performance. Based on these results, a 60 w% ionic liquid solution in water was selected and the vapour–liquid equilibrium was measured experimentally between 40 °C and 110 °C. From these curves the enthalpy of absorption for capturing CO₂ into the ionic liquid was determined. With these important parameters one is able to calculate the total energy demand for stripping of CO₂ from the loaded solvent for comparison of the ionic liquid based solvent with the reference MEA solvent. The energy demand of this 60 w% ionic liquid is slightly lower than that of the reference solution, resulting in possible energy savings between 12 and 16%.     

Cross-sectional biomonitoring study of pesticide exposures in Queensland,Australia, using pooled urine samples

A range of pesticides are available in Australia for use in agricultural and domestic settings to control pests, including organophosphate and pyrethroid insecticides, herbicides, and insect repellents, such as N,N-diethyl-meta-toluamide (DEET). The aim of this study was to provide a cost-effective preliminary assessment of background exposure to a range of pesticides among a convenience sample of Australian residents. De-identified urine specimens stratified by age and sex were obtained from a community-based pathology laboratory and pooled (n = 24 pools of 100 specimens). Concentrations of urinary pesticide biomarkers were quantified using solid-phase extraction coupled with isotope dilution high-performance liquid chromatography–tandem mass spectrometry. Geometric mean biomarker concentrations ranged from <0.1 to 36.8 ng/mL for organophosphate insecticides, <0.1 to 5.5 ng/mL for pyrethroid insecticides, and <0.1 to 8.51 ng/mL for all other biomarkers with the exception of the DEET metabolite 3-diethylcarbamoyl benzoic acid (4.23 to 850 ng/mL). We observed no association between age and concentration for most biomarkers measured but noted a “U-shaped” trend for five organophosphate metabolites, with the highest concentrations observed in the youngest and oldest age strata, perhaps related to age-specific differences in behavior or physiology. The fact that concentrations of specific and non-specific metabolites of the organophosphate insecticide chlorpyrifos were higher than reported in USA and Canada may relate to differences in registered applications among countries. Additional biomonitoring programs of the general population and focusing on vulnerable populations would improve the exposure assessment and the monitoring of temporal exposure trends as usage patterns of pesticide products in Australia change over time.     

Cytogenetic diagnoses after chorionic villus sampling are less reliable in very-high- or very-low-risk pregnancies

An increasing number of cytogenetic prenatal diagnoses are performed on chorionic villus samplings. The accuracy of this method is influenced by chromosomal mosaicism, mostly confined to direct preparation methods. Especially those investigators who have experienced false-negative and false-positive findings propagate the combined use of direct and culture methods. Yet large collaborative studies have shown that in approximately two-thirds of diagnostic cases only one procedure is applied. Moreover, the accuracy of a cytogenetic investigation depends not only on the ontogenetic origin of the tissues investigated, but also on interacting factors such as the ‘a priori risk’ and the ‘predictive value of a cytogenetic finding’. On this basis a differentiated prenatal diagnostic procedure is discussed, including either sole short-term culture (STC), combined STC and long-term culture (LTC), primary amniocentesis (AC), or primary percutaneous umbilical blood sampling (PUBS). The predictive value of the cytogenetic diagnosis from CVS varies significantly dependent on the a priori risk of a chromosome aberration and, in the case of an abnormal karyotype, on the specific chromosome involved. A non-mosaic and ‘non-lethal’ trisomy detected in STC is highly representative of the embryo/fetus, but there are exceptions of limited predictive value, e.g., trisomy 18. Guided by the strategy of an optional follow-up by LTC, AC, or PUBS in 1317 successive CV samplings, we are not aware of a false-negative diagnosis, but probably had one false-positive diagnosis: 47,XXY after STC; 46,XY after LTC. When referring to the rate of fetuses with an unbalanced karyotype expected in the different indication groups, a relative increase of false-positive findings in the very-low-risk group (maternal age ⩽35 years of age) and of false-negative findings in the very-high-risk group (abnormal ultrasonographic findings) of pregnant women when only performing CVS becomes obvious. Because of this dilemma, AC or—especially in the latter group—PUBS might be primarily offered to these indication groups instead of CVS.