W11 PM Advances in Biorestoration Strategies for Contaminated Sediments
Wednesday, 16 November 2005: 1:50 PM - 5:30 PM in 343-344

(JAF-1117-818108) Effect of Plants on Sulfur Species and the Bioavailability of Trace Metals in Wetland Sediments.

Jaffe, P¹, Choi, H¹, ¹ Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ, USA

ABSTRACT- The effects of oxygen release, evapotranspiration, and root exudation can influence sulfur dynamics in wetland sediments, which in turn is strongly coupled to the dynamics of trace metals. To gain a better understanding how the presence of plants and their seasonal growth cycle affects the biogeochemistry of sulfur species in wetland sediments, and how this in turn relates to the mobility of heavy metals, we conducted comparative in situ measurements between vegetated and non-vegetated sediments. Results show that in the presence of plants, sediments had substantially elevated SO42- concentrations in the rhizosphere during the growing season, ranging from 0.2 mmol/l to 6.20 mmol/l, with the highest increases occurring early during the growing season. The sulfide mass in the sediments, measured as AVS, showed that the AVS pool is sufficient to account for the increase in the SO42- concentration in the sediment pore water during the beginning of the growing season, and that the AVS pool was significantly higher in the vegetated sediments. Evapotranspiration is a major contributor in the transport of SO42- and trace metals from the overlaying water column into the sediments. The results from our measurements show that AVS and AVS associated zinc, cadmium, and lead penetrate deeper into vegetated sediments, where they are expected to be less vulnerable to erosion processes or to the exposure to air during low-flow conditions. The AVS to trace-metal ratio in the sediments was sufficiently high so the trace metals are considered to be non-bioavailable, even during the early growing season when a fraction of the AVS is reoxidized.

Key words: Plants, Sediments, Trace Metals, Acid Volatile Sulfides