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Ecohydrology Monitoring and Excavation of Semiarid Landfill Covers a Decade after Installation

^a School of Natural Resources, Institute for the Study of Planet Earth, and Department of Ecology & Evolutionary Biology, University of Arizona, Tucson, AZ 85721-0043 (present address) and Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545
^b Ecology Group, Risk Reduction and Environmental Stewardship Division, Mail Stop M887, Los Alamos National Laboratory, NM 87545
^c Los Alamos Technical Associates, 1200 Trinity Drive, Los Alamos, NM 87544 (present address) and Earth and Environmental Sciences Division, Mail Stop J495, Los Alamos National Laboratory, Los Alamos, NM 87545

View larger version (27K): [in a new window]   Fig. 1. Cross-sections showing design of landfill cover plots. A gravel mulch was applied to the surface of both designs.

View larger version (104K): [in a new window]   Fig. 2. Average volumetric water content in Conventional Plots and Integrated Plots from 1984 through 1994.

View larger version (147K): [in a new window]   Fig. 3. (a) Geotextile of Integrated plot I1 intact with extensive rooting above in topsoil. (b) Conventional plot C1 showing the effects of pocket gophers. Gopher burrows are at the interface between the topsoil (20 cm thick) and crushed tuff (detailed in Fig. 1). (c) Conventional plot C2 showing dye-stained root channels in crushed tuff. (d) Integrated plot I1 showing dye-stained root channels in crushed tuff and preferential flow paths around access tube used to measure soil water content via neutron probe. Compare to Figure 1 for scale.

View larger version (16K): [in a new window]   Fig. 4. Total biomass (g m–2) for conventional and integrated plots in 1986 and in 1995.

View larger version (44K): [in a new window]   Fig. 5. Bouteloua gracilis (blue grama), Pascopyron smithii (western wheatgrass, formerly Agropyron smithii), and other species as percentages of total biomass on conventional (C) and integrated (I) plots in 1986 (reported in Nyhan et al., 1990) and in 1995.

View larger version (30K): [in a new window]   Fig. 6. Root abundance with depth in conventional and integrated plots.

View larger version (9K): [in a new window]   Fig. 7. Conceptual graph illustrating trends in the relative influence of engineering factors (e.g, slope, soil textures and thicknesses) vs. environmental factors (e.g., succession, burrowing) in the long-term effectiveness of engineered landfill covers. (A) Three years or less after installation (Nyhan et al., 1990). (B) Ten years after installation (this paper). (C) Thirty years after closure (Wenzel et al., 1987). (D) One century or more after closure (no studies of landfill covers; analog studies in ecosystems)