Wednesday, 9 November 2005
10

Influence of Chemical Amendments on the Inorganic Chemical Signature of leachate collected from a Norfolk soil.

Jeff Novak, Warren Busscher, and Don Watts. USDA-ARS, Coastal Plains Soil, Water and Plant Research Center, 2611 W Lucas St., Florence, SC 29501-1242

Chemical amendments [i.e., polyacrylamides (PAM), drinking water treatment residuals (WTR), etc.] are added to degraded soils to improve physical conditions and/or to sequester excess nutrients. These amendments contain inorganic oxidizing agents (i.e., Na2O, etc.) or have ionic exchange properties that can alter the inorganic chemical signature of soil pore water. Gross chemical alterations in soil pore water due to ionic compounds or sequestration of essential trace elements can further degrade soils. We examined the inorganic chemical characteristics of leachate collected from a Norfolk soil that had been amended with either PAM or WTR. An alum-based WTR (60 g/kg) or an anionic-charged PAM polymer (30 and 120 mg/kg) were mixed into pots containing the Norfolk soil and were incubated for 60 d at 10% (w/w) soil moisture content. The pots were leached after 30 and 60 d with between 1.2 to 1.5 pore volumes of deionized water and the inorganic chemical composition determined. Both the WTR and PAM reduced Fe and Al concentrations in the leachate. Neither amendment changed K, Ca, and Mg concentrations; however, WTR significantly increased Na, Mn, and S concentrations in the leachate compared to the control (soil with 0% PAM or WTR). More Fe and Al were sequestered at the higher PAM concentration. Results indicate that both amendments can significantly alter the inorganic chemical signature of pore water.

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