HR: 0800h
AN: H31D-0429    [Abstracts]
TI: ``Phytomonitoring'': A Screening Tool For Detection Of Subsurface VOC Contamination
AU: * Graber, E R
EM: ergraber@agri.gov.il
AF: The Volcani Center, ARO, POB 6, Bet Dagan, 50250 Israel
AU: Ronen, D
EM: danronen@bgumail.bgu.ac.il
AF: Ben Gurion University of the Negev, Sde Boker Campus, Sde Boker, 84990 Israel
AU: Ronen, D
EM: danronen@bgumail.bgu.ac.il
AF: Israel Hydrologic Service, P.O.B. 20365, Tel Aviv, 61203 Israel
AU: Laor, Y
EM: laor@agri.gov.il
AF: Newe-Ya'ar Research Center, P.O.B 1021, Ramat Yishay, 30095 Israel
AU: Tandlich, R
EM: tandlich@agri.gov.il
AF: The Volcani Center, ARO, POB 6, Bet Dagan, 50250 Israel
AU: Atzmon, N
EM: atzmon@agri.gov.il
AF: The Volcani Center, ARO, POB 6, Bet Dagan, 50250 Israel
AB: In highly urbanized areas, characterizing the distribution of subsurface contamination is complicated by the dense urban underground and surface infrastructure. Drilling and monitoring in such settings requires extensive and complex coordination, and, for widespread problems extending over many square kilometers, high monetary outlays. When we encountered extensive groundwater contamination of the Central Coastal Plain aquifer of Israel underlying the Tel Aviv metropolis by volatile organic contaminants (VOCs), such problems rapidly became insurmountable. In this 200 km2 region, the average thickness of the vadose zone is about 30 m, and of the underlying freshwater saturated aquifer, about 130 m. As the ground surface is mainly impermeable due to urban development, volatile VOC vapors may build up to high levels in the vadose zone, and travel throughout long distances. As such, we were highly motivated to find an alternative, non-invasive, inexpensive means of scanning the vadose zone for VOCs, which would provide the basis for more traditional surveys at the predetermined sites. Specifically, we asked ourselves if it would be possible to exploit the VOC uptake ability of trees and shrubs for detecting subsurface vadose zone contamination below an urban environment. Preliminary laboratory tests showed that trees take up VOCs from unsaturated sediments. Further, VOCs were found in trees sampled at a former industrial site where the subsurface is heavily contaminated with chlorinated solvents (i.e., trichloroethene TCE; tetrachloroethene PCE), at the heart of our study area. As such, trees at numerous sites in the Tel Aviv area were sampled and analyzed for VOC content in tree trunk cores. Compounds detected in the tree cores include benzene, toluene, ethylbenzene, xylenes, TCE, PCE, and 1,1,1-trichloroethane. A good correlation between subsurface contamination and positive detection of contaminant VOCs in tree cores was found. The results support the idea that phytomonitoring can be implemented for preliminary screening of potentially contaminated sites in extensive urban areas where monitoring the unsaturated zone can prove problematic, time-consuming and expensive.
DE: 1803 Anthropogenic effects
DE: 1806 Chemistry of fresh water
DE: 1831 Groundwater quality
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting