Interactions Between Heavy Metal Lead, Cadmium And Two Freshwater Algae

Pollution of water by heavy metals is serious at present, especially for the leadand cadmium pollution. It not olny poses a potential hazard to water ecologicalsystem, but also can pose a serious threat to human health when heavy metalsaccumulate in organisms through food chain transfer..In this study, the interactions among lead and cadmium and two fresh algaewas discussed for the first time. In order to find a biological materials to indicateand repair heavy metals, we selected two common freshwater algae Microcysisaeruginosa(cyanophta) amd Scenedesmus Obliquus(chlorophyta), to investigate thetoxicity mechanism of lead and cadmium on algae and the tolerance and absorptionof algae on heavy metals. The results were as follows:1. Interactions between unitary lead and two freshwater algae: the resultshowed that Pb2+had a typical Hormesis effects on M. aeruginosa growth namelylow to promote and high to suppression, while Pb2+had a significant inhibitoryeffect for S.obliquus. Compare with M. aeruginosa, S.obliquus was more sensitiveto Pb2+, it can be considered as a biological monitoring materials of lead pollution.At the same time, this two algae had a strong capacity in absorbing Pb2+and themaximum amount of bioaccumulation was22.73mg/g and36.59mg/g respectively.This illustrated that it was an important significance research for bioremediation oflead pollution due to the effective absorption of two algae on Pb2+.2. Interactions between unitary cadmium and two freshwater algae: theresult showed that Cd2+had a significanyut inhibitory effect for M. aeruginosagrowth, while Cd2+had a typical Hormesis effects on S.obliquus, namely low to promote and high to suppression. It illustrated that M. aeruginosa was sensitive toCd2+, the algae can be considered as a biological indicator of cadmium pollution.Cd2+have an toxic effect on the cytomembrane and antioxidant systerm as the samewith Pb2+. Meanwhile, the absorption capacity of this two algae on Cd2+increasedwith increasing concentrations of heavy metals at the dosage range from0.05to0.2mg/L. The maximum amount of bioaccumulation was546μg/g and769μg/g. Thisproved that S.obliquus had a good capacity of Cd2+bioaccumulation. Therefore,S.obliquus was a good candidate for recovering Cd2+from waste water.3. Interactions among lead and cadmium and two freshwater algae: the resultshowed that the effect of Pb2+and Cd2+on M. aeruginosa growth was antagonistic,while effect on S.obliquus growth was synergy. The proliferation of the two algaewere inhibited by61.94%and83.23%respectively. In addition, the two algae hadgood strong capacity in removing heavy metal under joint dosage. The maximumamount of Pb2+bioaccumulation was12.110mg/g and15.999mg/g respectively.The maximum amount of Cd2+bioaccumulation was0.262mg/g and0.447mg/grespectively. It is clearly that the two algae could remove Pb2+and Cd2+effectivelyeven in the context of joint Pb2+and Cd2+, Therefore, the two algae were goodmaterial for monitoring and recovering Pb2+and Cd2+from waste water.Our study suggested that Pb2+have an toxic effect on the cytomembrane andantioxidant systerm by the results of the algae scanning electron microscope (SEM)and O-2content and POD and CAT enzyme activities. The study on the compoundtoxicity of cadmium and lead suggesting that the structure of large moleculeproteins and polysaccharides in algal cells may also have been damaged in varyingdegrees.