| The rapid development of urbanization and industrialization has made the problem of soil lead pollution increasingly prominent.Although a great deal of progress has been made around the source,occurrence,distribution,migration and transformation mechanism of lead in the soil,etc,there are few reports on the migration mechanism of soil lead in the soil-plant system under the conditions of drought,sandstorm and high pH in the northwest.Based on the investigation of potential soil lead pollution risks in the Ningdong Coal Chemical Industry Base,this paper sets up different soil moisture,exogenous lead concentrations and passivators to study the impact of lead on the soil environment and the growth and development of oil sunflowers,and further explores the moisture and lead Effect of Concentration on the Bioavailability of Lead and the Lead Tolerance Mechanism of the Soil-oil Sunflower System.It is expected to provide a certain theoretical basis for the remediation of lead-contaminated soil under drought and water shortage and high pH environment.The results show:(1)The tolerance of oil sunflower to soil lead poisoning increases with the decrease of water content.The key mechanism is that the soil-oil sunflower system is realized through the differential response of different antioxidant enzymes,increasing the total antioxidant capacity of the plant and increasing the content of osmotic adjustment substances.As the relative water content of the lead-contaminated soil decreases from 90%to 45%,the available lead content in the soil decreases by 20.69%～32.84%.Under the corresponding humidity conditions,the lead content in the roots,stems,leaves,receptacles,and grains of oil sunflowers also decreases.Under the same soil moisture condition,the lead content in the underground part of oil sunflower was higher than that in the above-ground parts,and the lead content in the above-ground part was root>stem>leaf>disc>seed.As the relative water content of the lead-contaminated soil decreases from 90%to 45%,the soil phosphatase activity increased by 7.14%～28.57%,the invertase activity value decreased by 13.02%～48.46%,and the soil respiration decreased by 7.99%～35.46%;The fungus reached the maximum when the relative soil water content was 45%;the number of actinomycetes and catalase activity in each treatment reached the maximum when the relative soil water content was 75%,and the urease activity and the number of bacteria in each treatment were not significant difference.The decrease of soil moisture inhibits the growth of oil sunflower plant height,stem thickness and disk diameter,but water stress can promote the growth of root system.With the decrease of soil water content,the activities of CAT and SOD decreased by 9.31%～32.46%and 12.06%～39.40%respectively compared with the soil relative water content of 90%,while the activity of POD increases first and then decreases,and reaches the maximum when the relative water content of soil is 75%.The contents of osmotic adjustment substances and malondialdehyde were reduced to varying degrees,and there was no significant difference in the water content and chlorophyll content of the plant leaf tissue.(2)The resistance of oil sunflower to soil lead toxicity showed a trend of first strengthening and then weakening with the increase of lead concentration.With the aggravation of lead stress,the content of available lead in soil increased,and the lead content in oil sunflower roots,stems,leaves,receptacles,and grains also increases,and reached the maximum when the content of lead in soil was 800 mg·kg-1.Under the same soil lead concentration,the lead content of each part of oil sunflower is root>stem>leaf>disc>seed.With the aggravation of lead stress,the activity of sucrase increased by 3.32%～42.92%,the number of actinomycetes increased by 7.82%～254.76%,and the activities of urease and phosphatase decreased by 22.22%～33.33%,12.00%～44.00%.However,catalase activity has no obvious regularity,and soil respiration,fungi,and bacteria have no significant differences compared with the control..In terms of growth and development,a small amount of lead(50 mg·kg-1)can promote oil sunflower plant height,stem thickness,disks and roots,while too high a content can inhibit it.In terms of physiology and biochemistry,the water content and chlorophyll content of oil sunflower leaves in each treatment were lower than those of the control.The activities of CAT,SOD and POD increase first and then decrease.CAT and SOD all reach the maximum when the lead content is 100 mg·kg-1,while the POD reaches its maximum value when the lead content is 50 mg·kg-1.The content of proline,soluble sugar,soluble protein and malondialdehyde increased with the increase of lead content,and all reached the maximum when the soil lead content was 800 mg·kg-1.(3)Under the two levels of lead pollution,Passivation agent organic fertilizer,EDTA,fly ash,and the combined application of fly ash and organic fertilizer or EDTA can inhibit the absorption of lead in various parts of the oil sunflower,and also improved the growth and development,physiological and biochemical of the oil sunflower to a certain extent.Through comprehensive analysis of the effects of passivation agents on the lead content of oil sunflower organs,soil biological properties and plant growth and physiology,it is concluded that the application of fly ash has the best effect on soil lead pollution remediation. |
