|
(117) pH Effects on the Desorption and Interaction of Natural Organic Matter and Trace Metals in Soils. Impellitteri, Christopher 1, Vasconselos, Flavio1, Saxe, Jennifer1, Peijnenburg, Willie2, Cochran, Melissa1, Allen, Herbert1, 1 2 ABSTRACT- Soil leaching is an important source of dissolved organic matter (DOM) for natural waters. Parameters, such as pH and particulate matter, differ between the soil and receiving waters. DOM in water extracts of 18 Dutch soils at varying pH levels were fractionated and characterized using an XAD-8 resin column. Three operationally defined fractions were distinguished; hydrophilic acid (Hyd), fulvic acid (FA), and humic acid (HA). The soils were analyzed for total organic carbon (solid phase) by boat sampler. Partitioning of each operationally defined fraction was analyzed as a function of pH. Total concentrations of individual fractions increased with increasing solution pH. The greatest percentage increase with increasing pH, with respect to total DOM, occurred for HA. The percentage of FA in solution remained roughly constant as a function of pH while the percentage of Hyd decreased with increasing pH. Correlative studies strongly suggest that HA plays a very important role in the solubilization of Cu and Pb at pH values ranging from 5 to 9. FA partitioning also correlates significantly with the partitioning of Cu and Pb in these soils. There exists little correlation between Hyd and metal partitioning. The effects of OM partitioning on Zn partitioning are minimal compared with Cu and Pb. The operationally defined fractions of the extracts of two soils at five different pH values were adjusted to pH levels commonly found in surface waters (pH = 7) and titrated with Cu in order to examine the binding properties of the individual fractions. Key words: Trace Metals, Humic Acid, Fulvic Acid, Hydrophilic Acid |
