Effects Of DOM And Dissimilatory Iron-Reducing Bacteria On The Bioavailability Of Heavy Metals In Rhizosphere Micro-Domains Under Hydraulic Conditions

Starting from the rhizosphere micro-domain,the root box was used to plant the Podo Lake wetland plant moss,combined with the interaction between DOM,microbial iron-reducing bacteria and heavy metal bioavailability(Cu,Pb,Cd)to study the hydrological situation.The changes of morphological contents of heavy metals in plant rhizosphere soil by DOM and dissimilatory iron bacteria,as well as the distribution characteristics and migration and transformation of heavy metals in various parts of plants,revealing the role of DOM-hydrogenated iron-reducing bacteria-heavy metal ternary in hydrological situation The mechanism of action on the bioavailability of heavy metals in the rhizosphere provides a theoretical basis for phytoremediation.The main findings are as follows:(1)DOM acts to activate Cu and Pb elements at 0cm and 2~3cm water level,which promotes the transfer of Cu and Pb elements from soil to Carex,and inactivates Cd,at 0cm.Under the water level,Cu and Pb elements are enriched in the leaves of Carex,and their enrichment to the roots is inhibited.Under the dry and wet alternate water level,DOM can passivate the Cu and Pb elements in the soil,and activate the Cd element in the soil,which promotes the transfer of Cd from the soil to the moss.At these three water levels,DOM inhibited the enrichment of Cd in the soil to the moss leaves.(2)The dissimilatory iron-reducing bacteria inactivated the Cu element in the soil at 0 cm water level,and enriched the Cu element from the moss leaf to the moss root,and Cu element in the soil at 2~3 cm and dry and wet alternate water level.It activates and inhibits the absorption of Cu by the moss leaves,promotes the absorption of Cu in the moss roots,activates the Pb element at the 0 cm water level,promotes the transfer of Pb to the moss leaves,and inhibits its Transfer to the root;passivate the Pb element in the soil at 2~3cm and the alternate dry and wet water level;activate the Cd element at the 0cm water level and the 2~3cm water level,and the Cd element under the dry and wet alternate water level It has a passivation effect.When the water level is 0 cm,it promotes the enrichment of Cd elements in the leaves and roots of the moss,and the alternate water level of 2~3 cm and dry and wet promotes the enrichment of Cd into the moss root,and inhibits its enrichment into the leaves.(3)The combination of DOM and dissimilatory iron-reducing bacteria has a passivation effect on Cu in soil at 0cm and dry-wet alternate water level,activates Cu element at 2~3cm water level,and promotes soil Cu element to moss.Enrichment in grass roots,2-3 cm and alternating wet and dry water levels inhibited the enrichment of Cu in mossy leaves and promoted the absorption of Cu in moss roots;activated Pb at 0 cm water level;in 2~3 cm and The dry and wet alternate water level has a passivation effect on the Pb element in the soil;the Cd element in the soil is activated at 0cm and 2~3cm water level;and the Cd element in the soil is inactivated under the dry and wet alternate water level.The ability to enrich Pb and Cd elements on mossy grassland and roots was improved under 0cm water level.The 2-3cm and dry-wet alternate water level conditions promoted the enrichment of Pb and Cd elements in the soil to the moss root,inhibiting its Enriched with leaves.(4)The separate action and combined action of DOM and dissimilatory iron reducing bacteria can activate the Cu,Pb and Cd elements in the soil of the rhizosphere micro-domain,and improve the migration and transformation ability of these three heavy metal elements in the soil.The combined effect of DOM and dissimilatory iron reducing bacteria on Cu and Pb elements is more obvious than the single effect.The activation effect on Cd is stronger than the addition of DOM alone,but weaker than the addition of dissimilatory iron reducing bacteria.