Toxic Effect And Enrichment Transfer Characteristics Of Arsenic And Mercury Pollution On Oenanthe Javanica

In this study,Oenanthe javanica was used as the test material.Through the two cultivation methods of Hydroponics and soil cultivation,A series of concentration gradients of exogenous As and Hg treatments were set up.Studied the growth physiological indexes of Oenanthe javanica and the distribution of heavy metals in the body under different concentrations of As and Hg stress,and discussed the toxic effects of As and Hg on Oenanthe javanica and the rules of enrichment and transfer in different parts,and conduct a safety risk assessment.Provided a reference for the cultivation of pollution-free vegetables and the feasibility of Oenanthe javanica used to repair water or soil in the future.Main conclusions were as follows:(1)Under hydroponic conditions,the changes of various physiological indexes of Oenanthe javanica show that: with the increase of growth time,the biomass of Oenanthe javanica showed an overall increasing trend.the greater the concentration of As and Hg stress,the smaller the increase in biomass;Low concentration of As and Hg can promote the chlorophyll production of Oenanthe javanica seedlings in the short term,and high concentration of As and Hg stress will inhibit the formation of chlorophyll;With the increase of As and Hg stress concentrations,the MDA content showed an increasing trend,indicating that the degree of membrane lipid peroxidation of Oenanthe javanica leaves gradually increased.When growed in the culture medium with As concentration of 40 mg/L and Hg concentration of 20 mg/L to 15 days,the superoxide anion radical oxidation damage is the biggest.and the two antioxidant enzymes SOD and POD play a key role in the removal of intracellular reactive oxygen species.CAT activity is not sensitive to changes in As and Hg concentrations.(2)Under the condition of soil cultivation,the biomass of different parts of Oenanthe javanica: leaves?roots?stems,when the As irrigation concentration was 10 mg/L and the Hg irrigation concentration was 5 mg/L,the biomass of stems and aerial parts of Oenanthe javanica reached the maximum;High concentration of As and Hg will reduce the content of chlorophyll a,chlorophyll b,chlorophyll a + b and carotenoid in Oenanthe javanica;Under As and Hg stress,the POD in Oenanthe javanica plays a major role in detoxification,SOD and CAT activity change is not significant;the degree of membrane peroxidation damage is proportional to the permeability of the cell membrane;Comparison of As and Hg stress at the same concentration found that Hg is more harmful to cress than As;The soluble sugar content increased first and then decreased;the soluble protein content increased.(3)With the increase of the concentration of As and Hg in the hydroponics and soil cultivation,the As and Hg content in various parts of Oenanthe javanica also increased,in order to ensure that the As content in the test Oenanthe javanica does not exceed the limit of 0.5 mg/kgFW,the concentration of As in the hydroponic nutrient solution must be limited to less than 0.393 mg/L,and the concentration of the irrigated As solution must be limited to less than 16 mg/L;to ensure that the Hg content in the test Oenanthe javanica does not exceed the limit of the standard 0.01 mg/kgFW,the concentration of Hg in the hydroponic nutrient solution must be limited to less than 0.021 mg/L,and the concentration of the Hg solution in the soil cultivation irrigation must be limited to less than 1.3 mg/L.(4)The enrichment coefficient of the aboveground part of Oenanthe javanica is smaller than that of the root system,and the enrichment capacity of Hg is greater than that of As;With the increase of the concentration of As and Hg in the cultivation solution,the transfer coefficient of Oenanthe javanica to As and Hg generally showed a downward trend,and the transfer ability of Oenanthe javanica to As was greater than that of Hg;the contribution rate of exogenous Hg in soil cultivation to Hg in plants is greater than the contribution rate of exogenous As to As in plants;The contribution rate of exogenous As and Hg to As and Hg in plants under hydroponics is greater than that in soil cultivation.Based on the comprehensive contribution rate of exogenous As and Hg to As and Hg in various parts of Oenanthe javanica and the enrichment transfer coefficient,Oenanthe javanica is suitable for remediation of low concentration As(5 mg/L)and Hg(1 mg/L)pollution of water environment.