2004 Denver Annual Meeting (November 7–10, 2004)

Paper No. 2
Presentation Time: 8:15 AM


ASAF, Lior, Soil and Water Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot, 76100, Israel, NATIV, Ronit, Soil and Water Sciences, Faculty of Agriculture, The Hebrew University of Jerusalem, POB 12, Rehovot, 76100, Israel, HASSAN, Marwan, Department of Geography, Univ of British Columbia, Vancouver, BC V6T 1Z2, Canada, SHAIN, Dror, Dept. of Soil & Water Sciences, The Hebrew Univ of Jerusalem, The Faculty of Agricultural, P.O. Box 12, Rehovot, 76100, Israel and GEYER, Stefan, Hydrogeology, UFZ - Umweltforschungszentrum, Leipzig-Halle GmbH, Theodor Lieser Strase 4, Halle, D-06120, Germany, asaf@agri.huji.ac.il

The temporal variations in the chemical and isotopic compositions of urban stormwater under different land uses, and their dependence on physical parameters such as precipitation intensity, stormwater discharge, cumulative stormwater volumes and the size of the drainage area, were investigated in the coastal city of Ashdod, Israel.

During 2000/2001 and 2001/2002, 46 stormwater events were intensively monitored for precipitation distribution and intensity at three stations across the city, and for stormwater discharge at seven stations draining 85% of the city area. Sixty-eight and 202 precipitation samples were collected and analyzed for chemical and isotopic compositions, respectively, as were 186 stormwater samples, collected from the drains during 15 of the 46 events.

Land use had only a minor effect on the concentrations of major ions and trace elements. Conversely, the concentrations and variety of volatile and semi-volatile organic compounds were significantly higher in stormwater generated in the industrial area than in that draining from residential areas. Ion and trace-metal concentrations were very low (below drinking-water standards) in 97% of the stormwater samples collected from all drains. Stormwater concentrations were higher at stations draining a larger area, thereby linking concentrations to the length of the stormwater flow paths. A first-flush effect was documented on both a seasonal and event basis for both ions and trace elements. The high concentrations of fecal coliform bacteria exceeded the drinking-water standards and displayed a random pattern. The isotopic ratios of oxygen and hydrogen in the stormwater suggest very little exposure to the atmosphere, resulting in very limited fractionation. The presence of fecal coliforms, ammonium in some samples, and specific ratios of nitrogen and oxygen isotopes in the nitrate, suggest that although the sewer and stormwater-collection systems are separated, wastewater, possibly from overflowing sewers, contributed to the drained stormwater.