The rationale for this project is that marine geochemistry of reactive iron and associated chemicals are considerably influenced by estuarine processes, involving uptakescavenging onto particulates in the water column; desorptionresorption processes in the zone of salinity mixing; flux to the seabed and behaviour at the benthic interface and during early sediment burial. The net result of these processes is that coastal sediments often represent a major sink for iron within the marine environment.
Geochemical field and experimental studies on the dissolved and particulate constituents, especially iron, zinc, lead and copper, in the river Po and estuary and in sediments from 6 cores to the south of the Po delta have been used to understand estuarine processes and temporal patterns of discharge to the shelf during the period of intense anthropogenic activity. The geochemistry of dissolved and particulate matter in the estuary and mixing experiments on river and seawater indicate little or no sorptive reactivity, implying that the river particulate matter composition alone influences the composition of shelf sediments. Heavy metal (copper, zinc, lead) inventories and estimates of sediment accumulation rates, using lead-210 and correlatable high zirconium to aluminium ratio horizons have been used to demonstrate that shelf sediment accumulation is a net process of riverine and northern shelf input and sediment erosion rates. Relatively high erosion rates in the south compared to the north imply a source of particulate metals to the Adriatic basins and eastern Mediterranean. Estimates of anthropogenic metal inputs show linear increases with time. Using the magnesium to aluminium ratio as an indicator of sediment provenance, it has been shown that the riverine input relative to the northern shelf derived sediments varies spatially and with time. The significance of a well defined temporal reduction in riverine inputs is discussed.
It is intended to establish the processes of coagulation and precipitation of iron oxyhydroxide and the bonding of metal cations (Cu, Zn, Pb, Cr, Cd and Hg) and anions (P) during different river discharge rates and biological productivity. The loci of desorption and sorption reactions during salinity mixing will be established from hydrographic (ToC, Sooo) and nutrient (Si04, PO4, NO3, NH4) observations. The sedimentation of iron and associated elements and their subsequent alteration or removal during burial diagenesis will be studied in offshore (10-20m) sediments, from collections of shallow cores (0-1m), hydraulic cores (6-9m) and pore waters, from geochemical and magnetic trends that occur in vertical 2mm, 1cm, 5cm) subsamples.
Funding SchemeCSC - Cost-sharing contracts