IN-SITU ENRICHMENT OF HEAVY-METALS FROM DEEP-SEA WATER BY AN ION-EXCHANGE PUMP SYSTEM

A deep-sea pump system, originally designed as an in-situ particle sam pler, was modified into an ''in-situ heavy-metal sampler'' in order to overcome the problems of shipboard contamination and low concentratio n in seawater analysis. The pump system was equipped with a prefilter, ion-exchange columns and an inductive flow meter to measure low flow rates. Preconcentration factors of up to 500 could be achieved in a pu mping time of about 5 h. Metal analysis was done onboard ship by measu ring the enriched solutions with stripping voltammetric methods. The p umping device was tested and optimized on four research cruises under varying conditions. Data from the Mediterranean Sea and the northeast Atlantic for up to eight heavy metals, including Mn, Fe, Ca, Ni, Zn, C u, Cd, and Pb, suggest the wide applicability of the system and the ad vantage of the in-situ preconcentration process. Though the first pump ing system was optimized on several cruises, constructive faults in pr inciple had not been overcome. A completely new system with a precisel y adjustable peristaltic pump and a programmable electronic microcontr oller unit was developed Two prototypes of the new system were tested successfully during R.V. Sonne cruise SO 92 in the Indian Ocean. The d eployment of the ''in-situ heavy-metal sampler'' allowed the measureme nt of heavy-metal concentrations in normal seawater and the detection of anomalies due to natural and anthropogenic sources.