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Title: Wet/Dry Cycling Effects on Soil Contaminant Stabilization with Apatite and

Authors:
;
Publication Date:
Research Org.:
Subsurface Biogeochemical Research (SBR)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1154456
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Materials in Civil Engineering; Journal Volume: 19; Journal Issue: 1
Country of Publication:
United States
Language:
English

Citation Formats

Daniel I.,Kaplan, and Anna S.,Knox. Wet/Dry Cycling Effects on Soil Contaminant Stabilization with Apatite and. United States: N. p., 2007. Web. doi:10.1061/(ASCE)0899-1561(2007)19:1(49).
Daniel I.,Kaplan, & Anna S.,Knox. Wet/Dry Cycling Effects on Soil Contaminant Stabilization with Apatite and. United States. doi:10.1061/(ASCE)0899-1561(2007)19:1(49).
Daniel I.,Kaplan, and Anna S.,Knox. Mon . "Wet/Dry Cycling Effects on Soil Contaminant Stabilization with Apatite and". United States. doi:10.1061/(ASCE)0899-1561(2007)19:1(49).
@article{osti_1154456,
title = {Wet/Dry Cycling Effects on Soil Contaminant Stabilization with Apatite and},
author = {Daniel I.,Kaplan and Anna S.,Knox},
abstractNote = {},
doi = {10.1061/(ASCE)0899-1561(2007)19:1(49)},
journal = {Journal of Materials in Civil Engineering},
number = 1,
volume = 19,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The microstructural and chemical mechanisms responsible for pulp fiber-cement composite degradation during wet/dry cycling are being investigated through environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), and mechanical testing. Based on these results, a three-part progressive degradation mechanism for cast-in-place kraft pulp fiber-cement composites is proposed, which involves: (1) initial fiber-cement or fiber interlayer debonding (2) reprecipitation of needle-like or sheath-like ettringite within the void space at the former fiber-cement interface or between the S1 and S2 fiber layers, and (3) fiber mineralization due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Thismore » investigation also revealed that kraft pulp fibers exhibit poor resistance to degradation due to their inferior dimensional stability, as compared to thermomechanical pulp (TMP) fibers. TMP fibers contain significant amounts of lignin, which is alkali sensitive. Despite this, TMP fiber-cement composite exhibit improved resistance to degradation during wet/dry cycling. It is proposed that this improvement in durability may be attributed to the presence of lignin in the cell wall restricting fiber dimensional changes during wetting and drying, and hence, minimizing fiber-cement debonding. Additionally, it is proposed that lignin acts as physical barrier to calcium hydroxide formation within the fiber cell wall, minimizing fiber mineralization of TMP fibers.« less
  • Efficacy of stabilizing Ce, Co, and Pb by adding apatite and zero-valent Fe (Fe(0)) to contaminated wetland sediments was quantified under oxidizing and reducing conditions. The redox status and the general water chemistry of the oxidized and reduced treatments differed greatly, yet the influences of the amendments on contaminant stabilization were quite similar; both amendments significantly (p less than or equal to 0.05) reduced aqueous contaminant concentrations. Based on resin sorption studies and thermodynamic calculations, Ce existed primarily as cationic and to a smaller extent, anionic species, and Co existed almost as cationic, neutral, and organically complexed species. Based onmore » a series of varying selective extractions, almost 50 wt-percentage of the Co and Pb were already strongly bound to the sediment, thereby limiting the potential (and need) of affecting additional immobilization through the use of amendments.« less
  • To investigate the potential effects of changing precipitation on forest ecosystems, the Throughfall Displacement Experiment (TDE) was established on Walker Branch Watershed, Tennessee in 1993. Three different throughfall amounts were tested: -33% (DRY), ambient (no change, AMB), and +33% (WET). Throughfall manipulations had no statistically significant effects on total C, N, exchangeable Ca2+, Mg2+, bicarbonate-extractable P, or extractable SO42- in soils after twelve years of sustained treatments. Increased K+ inputs in the WET treatment resulted in relative increases in exchangeable K+ compared to the AMB and DRY treatments. Soil C, N, and extractable P declined in all treatments over themore » 12-year study, and the declines in N were inexplicably large. Field observations contrasted with earlier simulations from the Nutrient Cycling Model (NuCM), which predicted greater decreases in exchangeable K+, Ca2+, Mg2+, and extractable P on the order of WET > AMB > DRY and no change in C, N, and extractable SO42-. The failure of the NuCM model to accurately predict observed changes is attributed to the lack of mechanisms for deep rooting and the transfer of throughfall K+ from one plot to another in the model. Measurements of element availability using resin membranes during the final years showed higher values in wet and lower values in dry treatments compared to ambient in for mineral N, K, Mn, Zn, and Al but the opposite for B, Ca, and Mg. In the cases of Ca and Mg, the patterns in resin values were similar to those on the soil exchange sites (greatest in the dry treatment) and appeared to reflect pre-treatment differences. This study showed that while longer term changes in soil nutrients are likely to occur with changes in precipitation, potential changes over this twelve-year interval were buffered by ecosystem processes such as deep rooting.« less
  • Atterberg limits, free swell, and hydraulic conductivity tests were conducted to assess how wet-dry cycling affects the plasticity and swell of bentonite, and the hydraulic conductivity of geosynthetic clay liners (GCLs) hydrated with deionized (DI) water (pH 6.5), tap water (pH 6.8), and 0.0125-M CaCl{sub 2} solution (pH 6.2). The plasticity of bentonite hydrated with DI water increased during each wetting cycle, whereas the plasticity of bentonite hydrated with tap water and CaCl{sub 2} decreased during each wetting cycle. Wet-dry cycling in DI water and tap water had little effect on swelling of the bentonite, even after seven wet-dry cycles.more » However, swelling decreased dramatically after two wetting cycles with CaCl{sub 2} solution. Hydraulic conductivity of GCL specimens remained low during the first four wetting cycles ({approximately}1 x 10{sup {minus}9} cm/s). However, within five to eight cycles, the hydraulic conductivity of all specimens permeated with the 0.0125-M CaCl{sub 2} solution increased dramatically, to as high as 7.6 x 10{sup {minus}6} cm/s. the hydraulic conductivity increased because cracks, formed during desiccation, did not fully heal when the bentonite rehydrated. In contrast, a specimen continuously permeated for 10 months with the 0.0125-M CaCl{sub 2} solution had low hydraulic conductivity ({approximately}1 x 10{sup {minus}9} cm/s), even after eight pore volumes of flow.« less
  • Mobile irrigation application systems, such as the LEPA system (Lyle and Bordovsky, 1981), are being designed to maximize irrigation efficiencies and minimize energy requirements. The drop tube application of water with such systems results in dry wheel operation in contrast to the wet operations experienced with conventional sprinkler and spray systems. Field tests were conducted using a load cell, power/energy instrumentation, and recorder to determine the magnitude of energy savings resulting from dry wheel operation on firm loam soil. The results indicate that wet soil increased the energy requirement by an average of 28 percent on interior towers and 50more » percent on the end tower.« less