Study On The Effect Of Long-term Heavy Metal Stress On The Growth Of Chlorella In Water

At present,the research on algae stress of heavy metals mainly focuses on the study of high concentration spans and short-term toxicity effects.There is still little research on whether heavy metals will affect the algae growth and change after long-term adaptation.The exogenous input of heavy metals has been most strictly controlled.The content of heavy metals in in-situ water often does not reach the concentration level set by most experiments.For copper,zinc,and lead as persistent pollutants,this article conducted a long-term toxicity test to investigate whether these three heavy metals are important for the growth of chlorella.Has persistent toxic effects.Therefore,in order to investigate the effects of heavy metals in water on algae growth under long-term stress,chlorella was used as the research object,and different concentrations of Cu²⁺,Zn²⁺,and Pb²⁺were set according to the"Quality Standards for Surface Water Environment"and"Integrated Wastewater Discharge Standards"Variables,taking into account that under natural conditions,the temperature of the water body is mostly in a changing state.This article uses an extreme case of 10°C as a span,and simulates temperature changes by changing the air temperature.Indicators such as activity,analyzed the effects of heavy metals and temperature changes on their growth,and the possible impact mechanisms,the main conclusions are as follows:Chlorella can maintain a good growth condition with Cu²⁺concentration of 0.01 mg/L and 0.05 mg/L.At a concentration of 0.05 mg/L,chlorella Both the MDA content and the superoxide dismutase?SOD?activity in the cells reached the highest,the membrane lipid peroxidation reaction was violent,and the antioxidant enzyme activity was also increased.The chlorella cells still maintained relatively stable growth.When the concentration of Cu²⁺reached 0.1 mg/L,all the indicators decreased significantly,the cell biomass and chlorophyll a had almost no change,the cells were severely damaged,and the pH value increased little,which was significantly lower than that of the low concentration and the control group.Under the condition of Zn²⁺concentration of 0.01 mg/L,the soluble protein,polysaccharide and chlorophyll a content were higher than those of the control group,which significantly promoted the growth of chlorella,the pH increased significantly and was higher than that of the control group,?pH They are 1.55 and 1.36 respectively.However,starting from 0.5 mg/L,the MDA content increased significantly on the 15th day,but both the SOD and catalase?CAT?activities were significantly reduced,the cell's antioxidant damage was significantly reduced,and the synthesis of chlorophyll a was also inhibited.Chlorophyll a did not increase,and the biomass of algal cells did not increase significantly.As a whole,the effects of different concentrations of Pb²⁺on the growth of chlorella are small.Normal growth can be maintained at concentrations of 0.05,1 and 2 mg/L.Chlorophyll a can be synthesized normally.Soluble proteins,polysaccharides,MDA Both SOD and SOD increased gradually with increasing concentration.However,at the concentration of 5 mg/L,the soluble protein and polysaccharide decreased significantly,and MDA,SOD,and CAT increased significantly,but the soluble protein and polysaccharide increased gradually with time,and the chlorophyll a and chlorella biomass began to increase from around the 15th day.There was a clear upward trend,and chlorella gradually returned to normal growth.Under the dual stress of temperature change and Pb,at 25?constant temperature,the biomass,chlorophyll a,soluble protein,and enzyme properties of chlorella cells were significantly higher than those under variable temperature conditions.Soluble sugars were not significantly affected by temperature.CK-25 Under four different conditions,CK-variable temperature,Pb-25 and Pb-variable temperature,the polysaccharide content increased sequentially.Under temperature changes,whether or not Pb²⁺is added has little effect on the indicators.The overall indicators of CK-variable temperature and Pb-variable temperature are similar and fluctuating.Based on water quality standards,this study describes the long-term effects of different concentrations of Cu²⁺,Zn²⁺,Pb²⁺,and temperature changes and lead stress on the growth of chlorella.The prevention of pollution provides a certain theoretical basis.