| With the rapid development of industry and agriculture,farmland ecosystems have been contaminated by toxic heavy metals,posing a severe threat to food security and human health.Phytoremediation is an eco-friendly and efficient in-situ remediation technology for reducing environmental pollutants and risks.However,most phytoremediation plants exhibit low restoration efficiency,long cycle,narrow application scope,and no resource utilization value,which significantly limits their implementation in cultivated land restoration.Artemisia argyi,an essential resource plant,has been identified to possess Cd enrichment ability through field investigations.Nevertheless,limited understanding of its Cd enrichment characteristics,primarily due to current production practices,has restricted its application potential in cadmium-contaminated farmland.Therefore,in this study,A.argyi was utilized as the primary research material to investigate its ability to absorb Cd at varying pH levels and Cd concentrations through pot experiments.Furthermore,the effects of root interaction on the characteristics of plant Cd enrichment and rhizosphere organic acid secretion were analyzed under intercropping conditions with Oryza sativa,and the remediation effects of different doses of sodium citrate on cadmium-contaminated paddy soil were evaluated by field plot experiments.The key findings are summarized as follows:1.The present study investigated the effects of soil Cd content and pH on the biomass and subcellular distribution of Cd in A.argyi grown under different pH conditions（pH=5,pH=6,pH=7）.The pot experiment results showed that soil Cd content significantly affected the biomass of A.argyi and the distribution of Cd in the subcellular level of organs and leaves,and there was a significant interaction between Cd content and soil pH.In lightly polluted soil,the contents of Cd in stems,leaves,and roots of A.argyi were 6.28,5.07,and 2.93 mg/kg,respectively,under neutral conditions（pH=6）,and the bioconcentration factors in stems（11.47）was significantly higher than that under acidic conditions（pH=5）.With the increase of soil pH,Cd content in leaf cell wall of slightly polluted soil increased,while Cd content in organelles decreased.In moderately polluted soil,the contents of Cd in stems and leaves of A.argyi were 8.41 and 5.45 mg/kg,respectively,and the bioconcentration factors were10.75 and 6.96,respectively,which were significantly higher than those under other conditions.In moderately polluted soil,the proportion of Cd in cell wall and soluble component of A.argyi decreased significantly with the increase of soil pH,but the proportion of Cd in organelles increased significantly with the increase of soil pH.These findings suggest that reasonable adjustment of soil pH according to the degree of soil pollution can effectively improve the efficiency of A.argyi remediation of Cd-contaminated soil.2.This study investigated the Cd enrichment characteristics of A.argyi and O.sativa under different root separation treatments.The results showed that the biomass of the two plants increased significantly under root interaction,and the content of Cd in the aboveground part of A.argyi and all organs of O.sativa increased significantly.The Cd content,bioconcentration factors,and translocation factor of partially separated A.argyi were 14.26 mg/kg,17.22,and 1.85,respectively.Cd accumulation in shoots and roots was 0.22mg/pot and 0.06 mg/pot,respectively,which were significantly higher than those in completely separated roots（control）.The content of Cd in brown rice,shoots,and roots of rice separated by root parts were 3.34,16.82,and 47.01 mg/kg,respectively,and the bioconcentration factors were 4.38,21.91,and 61.02,respectively,which were significantly higher than those of the control.The maximum Cd removal amount was 19.01%under O.sativa-A.argyi root interaction.These findings suggest that using a A.argyi and O.sativa intercropping system can establish a more efficient Cd-contaminated paddy field remediation technology and shorten the paddy field soil remediation cycle.3.The effects of different doses of sodium citrate（CK:control,T1:37.5 g/m2,T2:75g/m2,T3:112.5 g/m2 and T4:150 g/m2）on phytoremediation of Cd-contaminated paddy fields using A.argyi were analyzed in a field experiment.Results showed that the shoot Cd concentration was significantly higher under T2 treatment（9.08 mg/kg）than CK（6.51mg/kg）.Bioconcentration factors of shoots and leaves of A.argyi were significantly higher under T2 treatment（26.58 and 18.68,respectively）than CK（18.12 and 14.39,respectively）;the translocation factor of aboveground parts was also significantly higher under T2 treatment（3.51）than CK（2.45）;the amount of Cd removed by A.argyi from soil was significantly higher under T2 treatment（1.99 mg/m2）than CK（1.68 mg/m2）.After harvest,soil Cd concentration reduced,particularly under T2 treatment（by 19.4%）.However,high doses of sodium citrate application（over T3 treatment）constrained growth,reduced Cd accumulation and translocation capacity,and decreased the amount of Cd removed from the soil.Therefore,A.argyi has potential for Cd phytoremediation based on its high Cd accumulation and translocation capacity and resource utilization potential.Applying appropriate amounts of sodium citrate and multiple harvest of aboveground parts can enhance the remediation capacity of A.argyi to remove more Cd from contaminated soil. |
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