Charateristics Of Tolerance And Mineral Elements Absorption Of Lolium Perenne Under Pollution Of Pb And B[a]P

In recent years,with the continuous growth of China’s industrial and agricultural production,environmental pollution has become increasingly serious.The accumulation,migration and transformation of inorganic and organic pollutants in the ecosystem lead to the gradual deterioration of environmental quality,which seriously harm the benign circulation of substances in the soil circle and the living environment of human beings.Heavy metals（HMs）and polycyclic aromatic hydrocarbons（PAHs）coexist and accumulate in the environment for a long time and have high biotoxicity in the environment.The existing toxicological studies mostly focus on the environmental toxic effects of a single substance,and cannot reflect the combined toxic effects of multiple pollutants in the environment.There are few reports on the combined toxic effects of HMs and PAHs on the mineral element absorption of plants.Ryegrass（Lolium perenne L.）is widely used in ecological remediation,which has a good enrichment effect on HMs and can effectively reduce HMs pollution in the soil.However,when both HMs and PAHs are present in the soil,the application in ecological remediation of ryegrass will be limited when the tolerance range of ryegrass to HMs and PAHs is exceeded.Therefore,it is increasingly important to study the tolerance of ryegrass to the combined toxicity of HMs and PAHs.In this paper,the effects of 200,400,600,800,1200μmol·L^-1single Pb and20,40,60,80,100μmol·L^-1single B[a]P and combined(400μmol·L^-1Pb+40μmol·L^-1B[a]P、400μmol·L^-1Pb+60μmol·L^-1B[a]P、400μmol·L^-1Pb+80μmol·L^-1B[a]P、800μmol·L^-1Pb+40μmol·L^-1B[a]P、800μmol·L^-1Pb+60μmol·L^-1B[a]P、800μmol·L^-1Pb+80μmol·L^-1B[a]P)toxicity on the germination rate,fresh weight,dry weight,root activity of ryegrass and the absorption of mineral nutrients were studied by pot experiment.This study provided a scientific basis for further research on phytoremediation of combined toxicity of HMs and PAHs.The results of this experiment were as follows:（1）The different concentrations of Pb and B[a]P under single and combined toxicity inhibited the growth of ryegrass in different degrees,and the germination rate of ryegrass seed was 86.43%under 200μmol·L^-1Pb.The germination inhibition rate of ryegrass was the highest under combined polltion of 800μmol·L^-1Pb and 80μmol·L^-1B[a]P,and the germination rate of ryegrass was only 54.67%.The inhibition effect of Pb and B[a]P on root growth was greater than that on bud length,and the inhibition effects of Pb and B[a]P on root and bud length were greater than those of Pb and B[a]P.The biomass of both aboveground and underground parts of ryegrass under the combined toxicity of 400μmol·L^-1Pb and40～80μmol·L^-1B[a]P increased firstly and then decreased.（2）The different concentrations Pb or B[a]P mainly concentrated in the root of ryegrass under single or combined of Pb and B[a]P.The application concentration of single Pb or single B[a]P was significantly positively correlated with the content of Pb or B[a]P in ryegrass,and the application concentration of Pb significantly affected the content of B[a]P in ryegrass.The contents of Cu,Cr,N,P and K in ryegrass under single Pb increased firstly and then decreased with the increase of Pb concentration,while the content of Zn gradually decreased with the increase of Pb concentration.200μmol·L^-1B[a]P can promote the absorption of K.The combined toxicity of 400μmol·L^-1Pb and B[a]P promoted the absorption of N,P and K in the leaves of ryegrass,while the combined toxicity of 800μmol·L^-1Pb and B[a]P inhibited the absorption of Zn,Cu,Cr,N,P and K in different degrees.（3）Principal component analysis was used to evaluate the growth status of ryegrass treated with different concentrations under single and combined toxicity.The top three treatments were 400μmol·L^-1Pb+80μmol·L^-1B[a]P,CK,400μmol·L^-1Pb+40μmol·L^-1B[a]P,respectively.The results indicated that ryegrass could repair the toxic properties of 400μmol·L^-1Pb and 80μmol·L^-1B[a]P,and promoted the absorption of mineral elements.However,when the concentration of Pb was 800μmol·L^-1,the inhibiting effect of Pb and B[a]P on the absorption of mineral elements of ryegrass was intensified with the increase of B[a]P concentration,and the growth of ryegrass was significantly inhibited under combined pollution of Pb and B[a]P.