PARTICULATE METALS CONTAMINATION IN THE KISHON RIVER ESTUARY, ISRAEL

Suspended particulate matter (SPM) collected along the axis of the Kis hon River, its estuary and Haifa Bay were analysed for trace metal con centrations together with measurements of water density, pH and dissol ved oxygen, The concentrations of particulate Cd, Zn and Cu generally increased from the upper Kishon system (upstream from Tzipori-Kishon J unction) downstream and decreased from the Kishon Harbour seaward, whi le particulate Al concentrations decreased downstream and towards the open sea, Enrichment of Cd, Zn and Cu was found at Haifa Bay compared to the upper Kishon system, The axial profile of Mn concentrations ind icated reduction of Mn at the anoxic and low pH zone of the lower rive r system and precipitation of Mn-oxides at the estuary in response to the increase in pH and dissolved oxygen concentrations, Although Fe co ncentrations showed similar behavior to that of Al, the higher Fe/Al r atios at the estuary are probably due to precipitation of Fe-oxides on to pre-existing particles. This spatial non-conservative behavior of m etals is presumably due to the: 1. mixing between polluted river-borne particles and material of drainage basin and coastal origin; 2. chang es of the distribution coefficient of metals between the particulate a nd solution phases (K-d) with variations of salinity, pH and SPM conce ntrations; and 3. physical settling and currents, Short-term, tidal cy cle measurements undertaken at the lower Kishon system (Julius Simon B ridge) indicated a high contribution of resuspended sediments to the S PM amounts due to the high tidal energy, It is hypothesized that the l atter is the main mechanism by which SPM, which settles in the estuary , is transported landward creating a turbidity maximum zone between th e Julius Simon and Histadrut bridges, i.e. about 3 km upstream from th e estuary, It is proposed that the upper estuary zone acts as a purgin g system through which a low flux of SPM, enriched by organic and trac e metal content, is transported seaward and from which a high flux of SPM is returned landward due to tidal stress. (C) 1997 Elsevier Scienc e Ltd.