Mercury (Hg) contamination of aquatic ecosystems and subsequent methylmercury bioaccumulation are significant environmental problems of global extent. At regional to global scales, the primary mechanism of Hg contamination is atmospheric Hg transport. Thus, a better understanding of the long-term history of atmospheric Hg cycling and quantification of the sources is critical for assessing the regional and global impact of anthropogenic Hg emissions. Ice cores collected from the Upper Fremont Glacier (UFG), Wyoming, contain a high-resolution record of total atmospheric Hg deposition (ca. 1720-1993). Total Hg in 97 ice-core samples was determined with trace-metal clean handling methods and low-level analytical procedures to reconstruct the first and most comprehensive atmospheric Hg deposition record of its kind yet available from North America. The record indicates major atmospheric releases of both natural and anthropogenic Hg from regional and global sources. Integrated over the past 270-year ice-core history, anthropogenic inputs contributed 52%, volcanic events 6%, and background sources 42%. More significantly, during the last 100 years, anthropogenic sources contributed 70% of the total Hg input. Unlike the 2-7-fold increase observed from preindustrial times (before 1840) to the mid-1980s in sediment-core records, the UFG record indicates a 20-fold increase for the same period. The sediment-core records, however, are in agreement with the last 10 years of this ice-core record, indicating declines in atmospheric Hg deposition.

No abstract

Gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) were measured over two-week seasonal field campaigns near Salmon Falls Creek Reservoir in south-central Idaho from the summer of 2005 through the fall of 2006 and over the entire summer of 2006 using automated Tekran mercury analyzers. GEM, RGM, and particulate mercury (HgP) were also measured at a secondary site 90 km to the west in southwestern Idaho during the summer of 2006. The study was performed to characterize mercury air concentrations in the southern Idaho area for the first time, estimate mercury dry deposition rates, and investigate the source of observed elevated concentrations. High seasonal variability was observed with the highest GEM (1.91 ± 0.9 ng m -3 ) and RGM (8.1 ± 5.6 pg m -3 ) concentrations occurring in the summer and lower values in the winter (1.32 ± 0.3 ng m -3 , 3.2 ± 2.9 pg m -3 for GEM, RGM respectively). The summer-average HgP concentrations were generally below detection limit (0.6 ± 1 pg m -3 ). Seasonally-averaged deposition velocities calculated using a resistance model were 0.034 ± 0.032, 0.043 ± 0.040, 0.00084 ± 0.0017 and 0.00036 ± 0.0011 cm s -1 for GEM (spring, summer, fall, and winter, respectively) and 0.50 ± 0.39, 0.40 ± 0.31, 0.51 ± 0.43 and 0.76 ± 0.57 cm s -1 for RGM. The total annual RGM + GEM dry deposition estimate was calculated to be 11.9 ± 3.3 μg m -2 , or about 2/3 of the total (wet + dry) deposition estimate for the area. Periodic elevated short-term GEM (2.2 -12 ng m -3 ) and RGM (50 -150 pg m -3 ) events were observed primarily during the warm seasons. Back-trajectory modeling and PSCF analysis indicated predominant source directions from the southeast (western Utah, northeastern Nevada) through the southwest (north-central Nevada) with fewer inputs from the northwest (southeastern Oregon and southwestern Idaho). v vi ACKNOWLEDGMENTSWe are indebted to Sage Aslet for allowing us to do our air sampling on his ranch at House

No abstract

The intent of this study was to determine if composting is an effective means of managing water hyacinth while producing a quality horticultural compost product. Preliminary tests for the study included germination and seed mortality tests. Germination tests found that water hyacinth seeds germinated on filter paper media soaked in distilled water while placed in petri dishes held at a constant temperature of 27 C for 14 d. Seed mortality test results found that seeds of water hyacinth were rendered inviable at temperatures equal to or above 57 C. The study successfully developed a large-scale composting system that used water hyacinth as a primary feedstock. Eleven compost piles were derived from 10,000 kg of water hyacinth, 9,000 kg of food waste, 11,300 kg of poultry litter, and 17,200 kg of wood chips. Results indicated that the composting process reached and sustained sufficiently high enough temperatures to inactivate and fully decompose seeds and other propagules of water hyacinth. Therefore, water hyacinth can be composted without the potential danger of it spreading. Compost quality tests found that the compost produced was within acceptable to ideal ranges of accepted industry quality standards, though there was a learning curve by student workers in the preparation of the piles using the large equipment.