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植物修复技术用于修复重金属污染土壤是当前的研究热点，由于植物修复过程需要施加添加剂以提高修复效率，继而添加剂的选择也成了植物修复技术中的重要一环。同时，作为As超富集植物的蜈蚣草还存在着富集Cd和Hg的潜力。因此本研究旨在通过室外盆栽试验模拟蜈蚣草搭配添加剂修复汞矿区重金属复合污染土壤的实际情况，找出与蜈蚣草搭配效果最佳的添加剂，为开展田间修复试验奠定基础。土壤取自贵州万山汞矿区，并未进行过磨细处理，培植盆栽也是放于室外。通过盆栽培养试验研究磷酸二氢钙、磷酸二氢铵、EDTA、柠檬酸、草酸、EDDS、硫代硫酸铵、纳米TiO2及其混合搭配对土壤理化性质、蜈蚣草生理指标及植株各部分吸收累积Hg、Cd、As的影响，得到结论如下：1）不同添加剂引起了土壤理化性质的改变和在一定程度上活化了土壤中的Hg、Cd、As。在植物修复过程中需要增加土壤pH时，可以单独施加磷酸二氢钙或让磷酸二氢钙搭配EDTA、硫代硫酸铵。此等措施都能较大幅度地提高土壤中的pH；若需要减少pH，可以使用EDTA、EDDS、磷酸二氢铵+柠檬酸或磷酸二氢铵+纳米TiO2的添加方案，效果显著。对土壤有机质而言，磷酸二氢铵+柠檬酸对有机质的增加影响最为显著，磷酸二氢钙+EDDS对有机质的减少影响最显著。磷酸二氢钙搭配多种试剂都能够促使土壤中可交换态Hg、Cd、As的含量增多，特别是磷酸二氢钙+EDDS的组合能够同时促使土壤中Hg、Cd、As的可交换态含量较大幅度地增加。2）纳米TiO2、磷酸二氢钙+EDTA、磷酸二氢钙+柠檬酸、磷酸二氢钙+硫代硫酸铵和磷酸二氢铵+EDDS均能较大程度地提高蜈蚣草的生物量。而硫代硫酸铵、磷酸二氢铵+EDTA和磷酸二氢铵+硫代硫酸铵对蜈蚣草的生长有显著抑制作用，导致其生物量低。3）蜈蚣草自身对Hg就具有较强的累积能力和耐受性，蜈蚣草在磷酸二氢钙+柠檬酸的作用下大量累积Hg，体内Hg含量高达7.7mg/kg。对蜈蚣草吸收土壤As的能力提升显著的添加剂效果大小排序为磷酸二氢钙+柠檬酸>磷酸二氢钙+硫代硫酸铵>磷酸二氢铵+纳米TiO2>磷酸二氢钙+草酸>磷酸二氢铵+草酸。其中硫代硫酸铵+磷酸二氢钙的使用则能在促使蜈蚣草大量吸收Hg的同时保证其产生较佳的转运效果（转运系数为1.1）。磷酸二氢铵+草酸的组合对蜈蚣草吸收和转运土壤中的Hg也具有促进作用，其地上、地下部分能分别达到2.2mg/kg和2.5mg/kg，转运系数约为0.9。磷酸二氢钙+柠檬酸可使蜈蚣草根系对Hg的吸收积累能力大大提高，根部Hg含量高达12.5mg/kg。4）单独添加磷酸二氢钙明显增加了蜈蚣草吸收土壤中Cd的效果，植物体内Cd含量高达6.6mg/kg。对蜈蚣草吸收土壤Cd的能力提升显著的添加剂效果大小排序为磷酸二氢钙>磷酸二氢铵+EDTA>EDDS>硫代硫酸铵。纳米TiO2对蜈蚣草吸收Cd有抑制作用，致使蜈蚣草体内Cd含量只有0.7mg/kg。磷酸二氢钙+EDDS、磷酸二氢铵+EDDS能有效提升蜈蚣草体内转运Cd的能力，转运系数分别为1.1和1.8。5）对蜈蚣草吸收土壤As的能力提升显著的添加剂效果大小排序为磷酸二氢钙+柠檬酸>磷酸二氢铵> EDDS>磷酸二氢钙+硫代硫酸铵。而硫代硫酸铵、磷酸二氢铵+EDTA、磷酸二氢铵+草酸和磷酸二氢铵+EDDS则是较大程度地限制了蜈蚣草对As的吸收效果。在磷酸二氢铵+草酸的作用下，蜈蚣草体内As的含量只有4.1mg/kg，约为空白水平的1/3。在添加磷酸二氢钙、EDTA、草酸、纳米TiO2、磷酸二氢钙+硫代硫酸铵、磷酸二氢钙+纳米TiO2、磷酸二氢铵+柠檬酸、磷酸二氢铵+硫代硫酸铵或磷酸二氢铵+纳米TiO2的土壤中生长的蜈蚣草除了体内As含量高，其富集系数和转运系数均大于1。纳米TiO2作为添加剂时，无论是其单独添加，还是与磷酸二氢钙和磷酸二氢铵搭配使用，都促使了蜈蚣草对As富集与转运的能力显著提升。单独添加硫代硫酸铵或磷酸二氢铵+草酸抑制了蜈蚣草对As的富集效果。6）施加磷酸二氢钙+EDTA和磷酸二氢铵+EDDS时，修复Hg污染土壤效果最佳。土壤Hg含量减少了0.06mg/kg，修复效率为0.12%和0.11%，为不添加试剂时修复效率的2.5倍。添加EDDS、磷酸二氢钙+EDTA和磷酸二氢钙+纳米TiO2的土壤中Cd含量减少0.04mg/kg、0.07mg/kg和0.07mg/kg，蜈蚣草修复Cd污染土壤的效率分别为0.31%、0.49%和0.54%，远超不使用添加剂的情况（0.07%）。在施加了磷酸二氢钙+EDTA的土壤中，蜈蚣草对As污染的修复效率最大，可达2.78%，远远超过空白水准（0.76%）。7）蜈蚣草在修复土壤中Hg、Cd、As时，磷酸二氢钙+EDTA是提升蜈蚣草对这三种重金属修复效率的共同最佳添加剂。实际的重金属污染往往不是单一元素超标，而是多种重金属复合污染。所以磷酸二氢钙+EDTA的组合是修复Hg、Cd、As复合污染土壤的潜在适宜添加剂。对于不同污染比重的Hg、Cd、As污染土壤，可考虑针对性的添加剂，如选择磷酸二氢钙+硫代硫酸铵作为蜈蚣草修复以Hg污染为主的复合污染土壤的添加剂。

Phytoremediation technology for remediation of heavy metal contaminated soil is a current research hotspot, and the selection of additives has become an important part of phytoremediation technology. The purpose of this study was to simulate the actual situation of remediation of heavy metal contaminated soil in mercury mining area by outdoor pot experiment. Soil was taken from Wanshan Mercury Mine, Guizhou Province, without grinding, and potted plants were also planted outdoors. Pot culture experiments were conducted to study the effects of calcium dihydrogen phosphate , ammonium dihydrogen phosphate, EDTA, citric acid, oxalic acid, EDDS, ammonium thiosulfate, nano-TiO2 and their mixtures on soil physical and chemical properties, Pteris vittata physiological indices and plant uptake and accumulation of Hg, Cd and As. The conclusions were as follows:1) Different additives cause changes in soil physical and chemical properties and activate Hg, Cd and As in soil to a certain extent. When soil pH needs to be increased during phytoremediation, calcium dihydrogen phosphate can be applied alone or combined with EDTA and ammonium thiosulfate. These measures can greatly improve the soil pH; if the need to reduce the pH, we can use EDTA, EDDS, ammonium dihydrogen phosphate + citric acid or ammonium dihydrogen phosphate + nano-TiO2 as addition scheme, the effect is remarkable. For soil organic matter, ammonium dihydrogen phosphate + citric acid had the most significant effect on the increase of organic matter, while calcium dihydrogen phosphate + EDDS had the most significant effect on the decrease of organic matter. Calcium dihydrogen phosphate combined with a variety of reagents can increase the exchangeable the concentration of Hg, Cd and As in soil, especially the combination of calcium dihydrogen phosphate and EDDS can simultaneously promote the exchangeable the concentration of Hg, Cd and As in soil to increase considerably. 2) Nano-TiO2, calcium dihydrogen phosphate + EDTA, calcium dihydrogen phosphate + citric acid, calcium dihydrogen phosphate+ammonium thiosulfate and ammonium dihydrogen phosphate + EDDS can greatly increase the biomass of Pteris vittata. However, ammonium thiosulfate, ammonium dihydrogen phosphate + EDTA and ammonium dihydrogen phosphate + ammonium thiosulfate significantly inhibited the growth of Pteris vittata, resulting in low biomass.3) Pteris vittata itself has strong accumulation ability and tolerance to Hg. Pteris vittata accumulates Hg in a large amount under the action of calcium dihydrogen phosphate and citric acid, and the concentrations of Hg in vivo is as high as 7.7 mg/kg. The order of additives for improving the ability of Pteris vittata to absorb As in soil is calcium dihydrogen phosphate + citric acid > calcium dihydrogen phosphate + ammonium thiosulfate > ammonium dihydrogen phosphate + nano-TiO2 > calcium dihydrogen phosphate + oxalic acid > ammonium dihydrogen phosphate + oxalic acid. Among them, ammonium thiosulfate + calcium dihydrogen phosphate can promote Pteris vittata to absorb Hg in large quantities while ensuring a better transport effect (transport coefficient is 1.1). The combination of ammonium dihydrogen phosphate and oxalic acid also promoted the uptake and transport of Hg in soil by Pteris vittata grass. Its aboveground and underground parts could reach 2.2 mg/kg and 2.5 mg/kg respectively, and the transport coefficient was about 0.9. Calcium dihydrogen phosphate + citric acid can greatly improve the absorption and accumulation of Hg by Pteris vittata root system, and the concentrations of Hg in root is up to 12.5 mg/kg. 4) Adding calcium dihydrogen phosphate alone significantly increased the effect of Pteris vittata to absorb Cd in soil. The concentrations of Cd in plant was as high as 6.6 mg/kg. The order of additives for improving the ability of Pteris vittata to absorb Cd in soil is calcium dihydrogen phosphate > ammonium dihydrogen phosphate + EDTA > EDDS > ammonium thiosulfate. Nano-TiO2 inhibited Cd uptake by Pteris vittata, resulting in only 0.7mg/kg of Cd in Pteris vittata. Calcium dihydrogen phosphate + EDDS, ammonium dihydrogen phosphate + EDDS can effectively enhance Cd transport capacity of Pteris vittata, with transport coefficients of 1.1 and 1.8, respectively.5) The order of additives for improving the ability of Pteris vittata to absorb As in soil is calcium dihydrogen phosphate + citric acid > ammonium dihydrogen phosphate > EDDS > calcium dihydrogen phosphate + ammonium thiosulfate. However, ammonium thiosulfate, ammonium dihydrogen phosphate + EDTA, ammonium dihydrogen phosphate + oxalic acid and ammonium dihydrogen phosphate + EDDS greatly limited the absorption of As by Pteris vittata. Under the action of ammonium dihydrogen phosphate and oxalic acid, the concentrations of As in Pteris vittata was only 4.1 mg/kg, which was about 1/3 of the blank level. The enrichment and transport coefficients of Pteris vittatas grown in soil added with calcium dihydrogen phosphate, EDTA, oxalic acid, nano-TiO2, calcium dihydrogen phosphate + ammonium thiosulfate, calcium dihydrogen phosphate + nano-TiO2, ammonium dihydrogen phosphate + citric acid, ammonium dihydrogen phosphate + ammonium thiosulfate or ammonium dihydrogen phosphate + nano-TiO2 are all greater than 1 except for the high concentration of As in the soil. When nano-TiO2 is used as additive, whether it is added alone or combined with calcium dihydrogen phosphate and ammonium dihydrogen phosphate, the ability of Pteris vittata to enrich and transport As is enhanced significantly. Addition of ammonium thiosulfate or ammonium dihydrogen phosphate + oxalic acid alone inhibited the enrichment of As by Pteris vittata. 6) When calcium dihydrogen phosphate + EDTA and ammonium dihydrogen phosphate + EDDS were applied, the effect of remediation of Hg contaminated soil was the best. The concentrations of Hg decreased by 0.06mg/kg, and the remediation efficiency was 0.12% and 0.11% in soil, which was 2.5 times higher than that without reagents. The concentrations of Cd added with EDDS, calcium dihydrogen phosphate +EDTA and calcium dihydrogen phosphate +nano-TiO2 decreased by 0.04 mg/kg, 0.07 mg/kg and 0.07 mg/kg in soil The efficiency of Pteris vittata to remediate Cd-contaminated soil was 0.31%, 0.49% and 0.54% respectively, which was much higher than that without additives (0.07%). Among the soil with calcium dihydrogen phosphate and EDTA, Pteris vittata had the highest remediation efficiency for As pollution, reaching 2.78%, far exceeding the blank level (0.76%). 7) Calcium dihydrogen phosphate + EDTA is the best additive to improve the efficiency of Pteris vittata in remediation of Hg, Cd and As in soil. The actual heavy metal pollution is not a single element exceeding the standard, but a variety of heavy metal compound pollution. Therefore, the combination of calcium dihydrogen phosphate and EDTA is a potential suitable additive for remediation of Hg, Cd and AS contaminated soil. For Hg, Cd and As contaminated soils with different pollution proportions, specific additives can be considered, such as calcium dihydrogen phosphate + ammonium thiosulfate as additives for Pteris vittata to remediate compound contaminated soils dominated by Hg.