Effects Of Multi-walled Carbon Nanotubes On The Growth,Physiology Of Chlorella Pyrenoidosa And Discussion Of Influence Mechanism

Carbon nanomaterials can be widely produced and used due to their excellent properties.Thus,they will inevitably enter into water environment and cause potential impact on the aquatic ecosystems.Multi-walled carbon nanotubes(MWCNTs),hydroxylated multi-walled carbon nanotubes(MWCNTs-OH)and carboxylated multi-walled carbon nanotubes(MWCNTs-COOH)as three typical materials of nanomaterials,are widely applied and their potential environmental effects are being attracted more and more attention.Therefore,Chlorella pyrenoidosa was used as a test organism to study the biological effects and mechanism of nanomaterials on algae in this paper.The biological effects of MWCNTson Chlorella pyrenoidosawere investigated via exposure experiment.The results showed as following:(1)When the concentration of MWCNTs was 10 mg/L or less,Chlorella pyrenoidosa kept a nice specific growth rate and they kept a good state of growing.(2)The 96 h IC50 of purified MWCNTs,purified MWCNTs-OH and purified MWCNTs-COOH on Chlorella pyrenoidosawere 9.06 mg/L,16.03mg/Land 23.45 mg/L respectively;the 96 h IC50 of non purified MWCNTs,non purified MWCNTs-OH and non purified MWCNTs-COOH on Chlorella pyrenoidosawere 7.75 mg/L,14.58 mg/Land 24.21 mg/L respectively.(3)The content of chlorophyll a decreased with addition of nanomaterials dose,however,among all the experimental groups,when the dose of non functionalized multi-walled carbon nanotubes was less than 10mg/L and the dose of functionalized multi-walled carbon nanotubes was less than 20 mg/L,their content of chlorophyll a increased.(4)The contents of soluble protein of Chlorella pyrenoidosadecreased firstly enhanced then when nanomaterials dose added gruadlly,the maxium of content of soluble protein in purified nanomaterials experimental groups was obstained when the dose of nanomaterials was 10mg/L,the maxium of content of soluble protein in non purified nanomaterials experimental groups was obstained when the dose of nanomaterials was 20mg/L.(5)The total antioxidant capacity of Chlorella pyrenoidosa in all the experimental groups decreased continuously with dose addition of nanomaterials.(6)When the concentration of purified MWCMNTs was 20 mg/L ro more,functionalized MWCNTs dose was 40 mg/Lthe malondialdehyde content of experimental groups enhanced significantly(P<0.05);when the content of non purified MWCNTs was 40 mg/L ro more,the malondialdehyde content increased significantly(P<0.05),the malondialdehyde content increased significantly as well when the content of functionalized MWCNTs was 20 mg/L(P<0.05).(7)The process of purification could not ehance the IC50 of nanomaterials on Chlorella pyrenoidosa.The effects of shading effect,pH change in media,co-sedimentation and dispersion of nanomaterials on the growth of algae in exposure experiments were further studied through data fitting,measuring the algal growth indexes.It is clearly that the growth state has a direct relationship with the dispersion state of nanomaterials,and the pH change caused by the addition of nanomaterials to the culture medium is not the reason why the nanomaterials have a biological effect on algae under laboratory conditions.The shading effect and aggregation co-sedimentation may be the factors of the biological effect of nanomaterials,but the quantification of the degree of influence remains to be further studied.