Suchergebnisse

Abstract
The overall project objective at the Iron King Mine Superfund site is to determine the level and potential risk associated with heavy metal exposure of the proximate population emanating from the site's tailings pile. To provide sufficient size-fractioned dust for multi-discipline research studies, a dust generator was built and is now being used to generate size-fractioned dust samples for toxicity investigations using in vitro cell culture and animal exposure experiments as well as studies on geochemical characterization and bioassay solubilization with simulated lung and gastric fluid extractants. The objective of this study is to provide a robust method for source identification by comparing the tailing sample produced by dust generator and that collected by MOUDI sampler. As and Pb concentrations of the PM10 fraction in the MOUDI sample were much lower than in tailing samples produced by the dust generator, indicating a dilution of Iron King tailing dust by dust from other sources. For source apportionment purposes, single element concentration method was used based on the assumption that the PM10 fraction comes from a background source plus the Iron King tailing source. The method's conclusion that nearly all arsenic and lead in the PM10 dust fraction originated from the tailings substantiates our previous Pb and Sr isotope study conclusion. As and Pb showed a similar mass fraction from Iron King for all sites suggesting that As and Pb have the same major emission source. Further validation of this simple source apportionment method is needed based on other elements and sites.

Abstract
The Navajo Nation is the largest and one of the driest Native American reservations in the US. The population in the Navajo Nation is sporadically distributed over a very large area making it extremely ineffective to connect homes to a centralized water supply system. Owing to this population distribution and the multi decadal drought prevailing in the region, over 40% of the 300,000 people living on Navajo Tribal Lands lack access to running potable water. For many people the only alternative is hauling water from filling stations, resulting in economic hardship and limited supply. A solution to this problem is a de-centralized off-grid water source. The University of Arizona and US Bureau of Reclamation's Solar Membrane Distillation (SMD), stand-alone, pilot desalination system on the Navajo Reservation will provide an off-grid source of potable water; the pilot will serve as a proximal water source, ease the financial hardships caused by the drought, and provide a model for low-cost water treatment systems in arid tribal lands. Bench-scale experiments and an earlier field prototype plant showed viable operation of a solar heated, membrane distillation (MD) system, but further optimization is required. The objectives of the Navajo pilot study are to i) demonstrate integration of solar collectors and membrane distillation, ii) optimize operational parameters, iii) demonstrate and monitor technology performance during extended duration operation, and iv) facilitate independent system operation by the Navajo Water Resources Department, including hand-over of a comprehensive operations manual for implementation of subsequent SMD systems. The Navajo SMD system is designed as a perennial installation that includes remote communication of research data and full automation for remote, unmanned operation.