Title page for ETD etd-10022007-144646
|Type of Document
||Anderson, Martha Ann
||Long-term copper availability and adsorption in a sludge-amended Davidson clay loam
||Crop and Soil Environmental Sciences
|Martens, David C.
|Zelazny, Lucian W.
|Collins, Eldridge R. Jr.
|Donohue, Stephen J.
|Morse, Ronald D.
- Zea mays L.
|Date of Defense
A single application of aerobically digested sewage sludge was applied by Rappaport
et al. (1988) in 1984 at rates up to 210 dry Mt ha-1 on a Davidson clay loam (clayey,
kaolinitic, thermic, Rhodic KandiuduIts). The heavily contaminated sludge supplied up to
760 kg Cu and 620 kg Zn haha-1, which are below current cumulative limits, but above
annual loading limits for these metals (USEPA, 1993). Rappaport et al. (1988) reported an
increase in DTPA extractable Cu and Zn with increasing sludge rate. They observed a
linear increase in com yields with an increase in sludge rate, which was attributed to high
levels of available N supplied by the sludge. In the present residual study, conducted at the
same research site, DTPA extractable Cu and Zn followed the trend observed by
Rappaport et at. (1988). However, a linear decrease in corn and sorghum yields was
observed with increasing sludge rate. The sludge-related decrease in yields was attributed
to phytotoxicity (probably a combination of Al, Cu, Mn, and Zn) induced by low soil pH
levels. Whole plant tissue concentrations of eu and Zn at the high sludge rates were above
the normal range, however grain concentrations were within the normal range. An adsorption study was conducted, in which soils were amended with Ca(OH)2 and
Ala2(S04)3, to ascertain the effect of decreased pH on Cu adsorption on the soil. Copper
adsorption maxima decreased with a reduction in soil pH in all treatments. The effect of
ionic strength on Cu adsorption was also investigated. Regardless of pH or ionic strength,
Cu adsorption increased with an increase in sludge rate. This adsorption increase was
attributed to the higher organic matter content of the sludge treatments. The organic
matter at the highest sludge rate was approximately double that of the control after 11
years. The adsorption study shows that sludge amendment has long-term effects on metal
retention in soils and the field study reveals that careful management of sludge-amended
soils is necessary to prevent phytotoxicity.
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