PARENT SESSION
PM5 - Fate & Effects of Metals in Wetland & Terrestrial Systems
Monday, 18 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P264) Effect of exposure mode and sorption capacity saturation rate on metal partitioning onto organic matter.
Twardowska, Irena*,1, Steinnes, Eiliv2, Kyziol, Joanna1, Aune, An-Magritt2, 1 Polish Academy of Sciences, Institute of Environmental Engineering, Zabrze, Poland2 Norwegian University of Science and Technology, Trondheim, Norway
ABSTRACT- Possible preferential subsequent Me binding onto particular sorption sites in organic matter under the unsaturated (specific for natural systems) and saturated conditions was evaluated using ombrotrophic Norwegian and high-moor Polish peats. The major aim was to contribute to (i) developing the methods of spiking that most closely simulate mobility and bioavailability of metals enriched in natural organogenic systems/soils; (ii) assessing binding strength and mobility/mobilization potential of metals sorbed in wetlands. Sequential fractionation of metal enrichment with respect to binding strength (BS-partitioning) in parallel with studies on sorption mechanisms was accomplished on unspiked peat with metal content in the range of 0.41-2.1 mg Cd/kg, 21.4-57.4 mg Zn/kg, 4.7-7.6 mg Cu/kg and 1.5-2.5 mg Cr/kg, d.m., and on peat spiked with metals under batch and flow-through contact mode, up to the sorption capacity saturation that was 3-5 orders of magnitude higher than natural Me enrichment. The effect of contact time with adsorbate (from 1 day to 3 months) on metal BS-partitioning in batch system was also studied. No preferential metal enrichment in particular sorption sites at any rate of saturation was observed: metal BS-partitioning appeared to depend predominantly upon the contact mode of Me solution (L) with organic matter (S) during sorption cycle. Batch conditions (high L/S ratio) due to screening of sorption sites affect adversely Me enrichment in stronger BS fractions determined by the formation of metal-organic complexes ("insoluble organics") and chelate rings involving proton displacement from COOH and OH functional groups in HS ("soluble organics"). Since fast process of sorption terminated, no changes in metal BS-partitioning have occurred independently on the time of exposure. Metal partitioning at the flow-through mode of Me spiking appeared to correlate well with that in real soil organic fraction/wetland systems and thus should be preferred in ecotoxicological soil testing and simulating metal sorptiom processes in wetlands with adequate reliability.
Key words: organic matter, sorption, partitioning, metals