Study On Remediation Of Copper-polluted Lake Water Using Both Biochar And A Submergerd Macrophyte,Vallisneria Spinulosa

Biochar and submerged macrophytes are both good absorbing material or hyperaccumulators of heavy metal copper(Cu).However,the influence of biochar on submerged macrophytes in restoration of water environment polluted by heavy metal Cu is not very clear.It is important to study the effects of biochar on the growth of submerged macrophytes and the remediation of Cu pollution in water environment,which is of great significance to seek efficient and cheap methods for water ecological management.In this study,rice husk biochar and Vallisneria spinulosa are used as the main research object to carry out the following experiments.The tolerance and recovery ability of V.spinulosa on copper stress were studied.V.spinulosa was planted in aquariums and exposed to copper of four different concentrations,i.e.,CK: 0mg/L,T1: 0.5mg/L,T2: 1mg/L and T3: 2mg/L for a week.Then the copper polluted water was changed into clean tap water to study a two-week recovery of the plants.The results indicated that the copper treatments significantly inhibited the growth of V.spinulosa.The height,wet weight and chlorophyll contents of V.spinulosa in the copper treatments were significant lower than those in the CK treatments.The copper removal rate of V.spinulosa was significant higher as indicated by the decreasing copper content in the water of the copper treatments than the CK treatment.The copper contents in the aboveground parts of V.spinulosa were increased with the increasing copper contents in the water column,while there were no differences among treatments for belowground parts.The stoichiometric homeostasis index(1/H)of V.spinulosa for copper was approximately1.11,which indicated a flexible copper stoichiometric homeostasis of V.spinulosa.In the recovery stage after the copper stress was removed,the length of aboveground and belowground parts and copper contents of aboveground parts of V.spinulosa among treatments were significant different,while the wet weight,chlorophyll contents and copper contents of belowground parts of V.spinulosa among the three copper treatments were no difference.Our study indicated that V.spinulosa was a good copper hyperaccumulator with a capacity of recovery after the removal of copper stress.The influences of rice husk biochar on v.spinulosa remediation of copper contaminated sediment.The polluted sediment(0.5mg/g)was prepared by adding Cu.Four rice husk biochar concentration gradient(CK: 0 g/L,T1:3 g/L,T2:6 g/L,T3:12 g/L)were set up and the experiments lasted for two weeks to study the influence of rice husk biochar on the growth of V.spinulosa under the Cu polluted sediment.The results indicated that the release of Cu to the water is only 0.04% in the Cu polluted sediment.So,the useless of V.spinulosa-rice husk biochar system help the release of Cu in the sediment.There was no significant difference between the water content of Cu treatment group,but there were significant differences in treatment group and control group after the end of the incubationperiod.The rice husk biochar can effectively reduce the water Cu2+ concentration,decrease Cu accumulation in V.spinulosa,improve the growth and chlorophyll content of V.spinulosa under the Cu polluted water.But there was no significant correlation between the amount of biochar and Cu content in the sedimentThe effect of biochar on V.spinulosa remediation of copper contaminated water.By setting four rice husk carbon content gradient(CK: 0g/L,T1:3g/L,T2:6g/L,T3:12g/L),the biochar was added to 1mg/L Cu concentration in water to study the effects of biochar on V.spinulosa and water environment on Cu in water stress condition.The results show that rice husk biochar can effectively reduce the concentration of Cu2+ in water and V.spinulosa accumulation and leaf nitrogen content on Cu.The stress of copper V.spinulosa can be alleviated,thus extending the V.spinulosa reaches the maximum accumulation time However,in the case of copper polluted sediment,the rice husk biochar has no significant influence on dissolved oxygen and PH in water,but can reduce the nitrogen and increase the phosphorus content of water.