The Absorption Of Cd²⁺ And The Affection In Photosynthetic Activity Of Ulva Prolifera

The issue concerning heavy metal pollution becomes increasingly serious with the development of chemical industry,especially the cadmium pollution. To remove heavy metals from the environment, a variety of methods have been developed, including physical methods, chemical methods and biological methods. However, these traditional methods have many limitations, such as expensive costs and low removal efficiency. Therefore, an effective, low cost and easy to popularize method urgently need to be open up.Marine macro-algae are large photosynthetic organisms which possess remarkable properties. For example, it can be used as adsorbing material to remove heavy metals from environment. Additionally, the removal efficiency of macro-algae is quietly high, and macro-algae resources are abundant and easy to get. In our study, we attempt to use Ulva prolifera, a kind of marco-alga with tremendous biomass, to remove Cd2+ in various water environments. We add different concentrations of Cd2+ in seawater, semi-seawater, freshwater, C ity inner river water, industrial wastes water and Cd2+ contained elutriant of soil,and U. prolifera was used to remove Cd2+ in these Cd2+ contained water environments. We measured the Cd2+ removal efficiency of U. prolifera and its photosynthetic activity at the presence of Cd2+. The results show that U. prolifera can remove Cd2+ in water environment effectively. The highest removal efficiency of U. prolifera was observed when 1 μmol/L Cd2+ was added in freshwater and treated for 1 day, which can reach at 94.89%. However, the removal efficiency of U. prolifera in other Cd2+ contained water environment was only about 50%. The photosynthetic activity of U. prolifera was inhibited in a certain degree and the inhabitation was more serious for YII than YI under high Cd2+ environment. With Cd2+ concentrations of 1 and 10 μ mol/L, no significant suppress was found in the photosynthetic activity of U. prolifera. As Cd2+ concentration was up to 50 μmol/L, the photosynthetic activity of U. prolifera was significantly inhibited, and the values of YII and Fv/Fm were nearly zero. After treatment in Cd2+ contained water samples for 5 days, U. prolifera was maintained in the Cd2+- deficiency water to recover its photosynthetic activity. With the exception of fresh alga, dry U. prolifera, which was made by different way, was used to remove Cd2+ in freshwater with additional Cd2+. The results show that the removal efficiency of dry alga was also very high, and the highest removal efficiency was found in fresh water with 1μ mol/L of Cd2+ concentration, which reached at 88.21% after treatment for 1 day. The preliminary results show that U. prolifera can be an eminent material for removing heavy metals in environment. Once promotion, a large number of thalli were used to remove heavy metals. Therefore, this can solve the problem of tremendous thalli of Green Tides, avoiding secondary pollution.