Thursday, November 16, 2006 - 9:40 AM

Adsorbed Heavy Metals and SVOCs in Wadi Secher Channel Banks and Flood Water Draining the Industrial Hovav Complex, Northern Negev Desert, Israel.

Noa Balaban, Jonathan Laronne, and Shimon Feinstein. Ben-Gurion Uni., ben-gurion st., Beer-sheva, Israel

River pollution by suspended sediments has been acknowledged to be a major environmental problem. Fine particles have a very large ability to adsorb pollutants such as heavy metals and SVOC's, and they are capable of traveling long distances in flood waters, thereby potentially contaminating the channel banks and areas distant from the polluting source. The contaminated channel banks may function as a source for further future contamination. The pollution potential is enhanced in semiarid dryland channels transporting elevated concentrations of suspended sediment. In this research we have been monitoring Wadi Secher, a flash-flood ephemeral channel that drains the Ramat Hovav industrial zone in the northern Negev desert of Israel. With a semi arid climate, suspended sediment concentrations in wadi Secher are elevated, about 50,000 mg/l, resulting in high polluting potential. This research has two objectives: (1) examining the channel banks to determine the content of adsorbed heavy metals as a function of the distance from the industrial zone and height on the channel bank; (2) monitoring the concentration and loads of heavy metals and SVOCs adsorbed onto suspended sediments during flood events.The sampling station includes an automatic sampler, water stage measurement with pressure transducers, continuous monitoring of pH, EC and temperature of floodwater by a multi-sensor sonde and a high-end turbidity sensor. Sampled suspended sediments are analyzed for heavy metal and SVOC sorbates. Preliminary results show that the banks contamination differs with distance from the industrial zone and sampling height. In addition, adsorbed contaminant concentrations and sediment quantities are larger in the first flush, as originally hypothesized. Most of the heavy metal load is adsorbed rather than dissolved. The concentration of suspended particulates and the extent of adsorption onto them, at the sampling station have been calculated.