PARENT SESSION
PM5 - Fate & Effects of Metals in Wetland & Terrestrial Systems
Monday, 18 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P261) Contributions of Scirpus californicus in a constructed wetland system receiving copper contaminated wastewater.

Murray-Gulde, Cynthia^*,1, Rodgers, John¹, ¹ Clemson University, Pendleton, SC, USA

ABSTRACT- Selected functional roles of Scirpus californicus, giant bulrush, were evaluated in an eight-acre constructed wetland treatment system receiving copper-contaminated water. The constructed wetland used in this research was designed to decrease bioavailable copper concentrations in a wastestream and eliminate associated toxicity to downstream biota by exploiting the thermodynamic processes responsible for copper speciation. This is achieved by integrating carbon, sulfur and copper biogeochemical cycles. S. californicus, which represents an integral part of the carbon cycle in this system, plays a physical, chemical and biological role in removing metals from the aqueous phase. Specific contributions of S. californicus in this system include providing a sustainable carbon source for removal of copper by 1) providing organic ligands for sorption of copper entering the system, 2) continuous production of organic ligands through the growth of S. californicus, 3) accretion of organic ligands over time due to decomposition of S. californicus detritus, and 4) production of organic carbon as an energy source for dissimilatory sulfate reduction. Shoots and roots of S. californicus sorbed 0.6% and 1.9%, respectively, of copper entering the system. Production of S. californicus increased by 90% in its first year of growth and an additional 60% during the second growing season representing a significant increase in organic ligands during the ontogeny of this system. The half-life for S. californicus detritus in the constructed wetland system was approximately 44 d, indicating that detritus will accrete over time, providing binding sites for copper as well as a continuous energy source for bacterial metabolic processes that contribute to copper immobilization in wetland systems. In addition to providing a carbon source, S. californicus does not aerate its root zone allowing a negative redox (−100 to −250 mV) to be maintained and providing conditions necessary for the production of acid volatile sulfides. The multiple roles played by S. californicus in this constructed wetland treatment system represents a novel approach to phytoremediation of metals.

Key words: Constructed wetland, copper, Scirpus californicus, phytoremediation