Study Of Copper Bioavailability For Fish And Available Cu Long-term Monitoring Methods

Bioavailability of copper to Paracheirodon was studied in laboratory. Based on the result of investigation on uptake of copper in various species (free ion, complexed, adsorbed, in food) in artificial fresh water, the metal accumulated in fish body and gill was compared. The effect of lead on copper uptake was also examined.Application of dialysis membrane filled with cation exchange resins on long-term monitoring of free copper content in aquatic environment was investigated. The selectivity of copper by the membrane, the types of resins, the capacity of adsorption and the procedure of copper elution were studied. The main factors affecting the adsorption rate ( such as the temperature of water, the presence of impurities from natural water, membrane pore-size and the existence of lead) were investigated. The adsorption of copper in different species (free ion, complexed, adsorbed) and the adsorption kinetics were demonstrated.The dialysis membrane filled with resin was tested to simulate the uptake of copper by fish in laboratory and in situ.It was found that Paracheirodon accumulated copper in free and adsorbed form both in water and food by fish body and gill. The amount of copper accumulated in both fish and gill increased with the increase in copper concentration in water and food and exposure duration up to a level above which the normal physiological activity of fish was inhabited. With fulvic in the system, the uptake rate decreased significantly indicating that the fulvic combined copper is not available to the fish uptake. The amount and the uptake rate of copper in gill were one order higher than the other part of the fish. Copper uptaked from food was accumulated at fish body first, not the gill. The ratio of copper amount in gill and body increased with the exposure time. It also showed the significant synergism when lead was added to the system.It was demonstrated that the dialysis membrane filled with Chelex-100 resin absorbed the microcontent copper in water selectively and effectively. The coefficient of selectivity was four order higher than normal ions. The copper adsorbed in the resin was easily eluted by diluted hydrogen nitrate. The capacity of dialysis membrane filled with 0.4 ml resin can meet the requirement of monitoring for several months. The presence of impurities from natural water inhabited the absorption significantly by covering the surface of the membrane. The absorption rate was positively correlated to copper concentration, temperature and a non-integrated power function of membrane pore-size. It could be described as: M = a * [Cu] * S n , which M, [Cu] and S represent the accumulated copper amount, concentration of copper in water and membrane pore-size respectively. The existence of lead did not effect the copper absorption by membrane. All kinds of adsorbed and complexed copper with EDTA, fulvic acid, or other organic ligands from natural water were not available to the absorption of the dialysis membrane, indicating that the membrane is able to absorb free metal ion specifically.By comparing the copper accumulation by membrane and fish, it was found that the relation between the concentration of free copper in water and the amount of copper accumulated by membrane and fish. were correlated. This is same in laboratory and in situ. It was deduced that it is feasible to monitoring the bioavailable metal content in natural water by dialysis membrane filled with cation exchange resin.