The original MOUDI (Micro-Orifice Uniform Deposit Impactor) cascade impactor, reported in the literature in 1991, used an external gear system to achieve a uniform deposit and was intended for industrial hygiene studies with sample times in the range of minutes to a few hours. To facilitate much longer run times, a second generation MOUDI, MOUDI-II, which uses internal electric motors to rotate the impaction plates, was developed. Three model 120 MOUDI-IIs were used in a 32-month program to sample ambient atmospheric aerosols at several industrial and urban locations in Minnesota. For these sampling locations, each 120 MOUDI-II operated continuously for a minimum of five, and optimally 7 days, to collect a sample at a site. During these community sampling events, the three 120 MOUDI-IIs logged 4007, 2637, and 3230 h of operating time, respectively. A laboratory side-by-side comparison of the three 120 MOUDI-IIs showed good agreement amongst the three 120 MOUDI-IIs and, thus, the particle size distributions were independent of the 120 MOUDI-II used. Application of the 120 MOUDI-IIs for long-term ambient sampling was demonstrated by comparing size distributions from the background locations: Minneapolis, Duluth and Ely, Minnesota, representing urban, light industrial, and pristine area type of aerosols, respectively. PM 2.5 averages from Minneapolis and Duluth compare well with three-year averages from state regulatory sampling.

Pulp facilities which recycle office waste paper generate large amounts of waste by-products in the process of producing high-grade pulp. The paper-like residue, called de-inking residue, was evaluated for use in the revegetation of coarse taconite tailings in northeastern Minnesota. Minnesota Mineland Reclamation Rules specify that a 90 percent vegetative cover shall be established on tailings after three growing seasons; however, the 90 percent cover requirement on coarse tailings has not been consistently achieved using standard reclamation practices. Research plots were established in 1992 at the Eveleth Mines Fairlane Plant utilizing a randomized block design using five levels of de-inking residue, five levels of fertilization, and two plant mixes on 2.5-by 4.0-m plots. Lysirneters were installed to monitor changes in sub-surface water quality. Vegetative cover was measured at two sampling periods each in 1992 and 1993. Fertilization and de-inking residue amendments had significant effects on the vegetative cover of introduced and native plant species. Vegetative cover for introduced species increased from no cover to 49 percent at the end of the first growing season, to 90 percent at the end of the second growing season on tailings fertilized at the highest level and amended with residue at 22.4 kg ha· 1 • At the same fertilizer and de-inking residue rate, vegetative cover for native plants increased from no cover to 7 percent at the end of the first growing season, to 69 percent at the end of the second growing season.

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