Poster 169 – Click on poster below to view presentation from author.
Co-Authors: Niroj Aryal
The chemistry and biology of a soil system is heavily influenced by the roots in the rhizosphere. The objectives of this experiment were: (1) to quantify the influence of exudates and root oxygenation on metal mobilization, and (2) evaluate evapotranspiration, plant uptake, oxygenation of soils and rhizostimulation. This was done using two complementary experiments. In the first experiment, six (6) small columns were filled with silica sand-soil mix and fitted with a platinum redox potential (ORP) probe and soil oxygen probe to monitor redox potential and soil oxygen levels, respectively. The six columns were spiked with arsenic, manganese and iron to mimic their environmentally relevant concentrations. Three of the six columns were planted with tall shade poplars and the remaining three were used as no-plant controls. In the second experiment, six (6) large tanks were filled with soil and fitted with 11 probes (moisture, ORP and soil oxygen sensors) at various depths (0, 9 and 18 inches).Three columns were planted with tall shade poplars and the remaining three were no-plant controls. During plant establishment, water was added to all columns according to the needs of the poplars. After establishment, carbon-rich, synthetic food-processing wastewater was prepared and added at a rate of 1.50 GPD ft-2 for a month to all columns. Leachate was collected and analyzed weekly. ORP and soil oxygen values, COD leached, and microbial data in each system indicated the redox state of the experimental systems, rates of chemical oxygen demand (COD) degradation as well as diversity and abundance of microorganisms between planted and control columns. Comparison of metal masses leached from the columns quantified the net effects of exudates and root oxygenation on the mobilization of metals. This information is useful in preventing groundwater contamination from heavy metals and nitrates.
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