桑树(Morus alba L.)原位修复某尾矿区重金属污染土壤

In-situ phytoremediation of heavy metal-contaminated soil by Morus alba L. near a mine tailing

木本植物具有根系发达、生物量大、适应性强等特点,可广泛用于重金属污染土壤修复.本文通过5年的田间修复试验,研究了桑树(Morus alba L.)对污染土壤中重金属的累积和分布特征、土壤中重金属和营养元素有效性含量的变化,来探讨桑树修复某尾矿区污染土壤中Mn、Zn和Cd等重金属的效果.研究结果表明,桑树生物量大,可用于重金属污染土壤的生态修复与景观恢复.田间种植5年后,桑树整株干重每株可达4 kg.桑树对土壤中重金属具有一定的转运和累积能力,地上部分中Cd、Zn和Mn等重金属含量明显大于根部,尤其是叶片中重金属含量明显大于枝和主干中的含量.修复5年后,桑树地上部分Zn和Mn的累积总量可达3277.7 mg·100 m-2和2422.4 mg·100 m-2,且土壤中Mn和Zn含量分别从2192.5 mg·kg-1和103.2 mg·kg-1降低至1790.0 mg·kg-1和85.94 mg·kg-1,同时土壤有效态Mn和Zn分别显著(P<0.05)降低66.0%和28.6%.然而,桑树落叶中Cd、Zn和Mn含量分别可达0.36、64.5、189.2 mg·kg-1.因此,通过定期清除桑树落叶或刈割地上部分,可防止叶片中重金属对土壤造成二次污染,同时削减土壤中重金属含量.同时,经桑树修复5年后土壤中碱解氮、有效磷和速效钾含量均显著(P<0.05)降低,需定期补充相应氮、磷和钾肥来强化桑树修复尾矿区重金属污染土壤.

Woody plants have developed root system,large biomass production and strong adaptability,which can be widely used for heavy metal-contaminated soil remediation.Through 5 years in-situ phytoremediation experiment,the accumulation and distribution characteristics of heavy metals in Morus alba L.and the changes of total heavy metals and available nutrient elements contents in soil were conducted to study the phytoremediation effect of M.alba L.in a mining tailing area.The results indicated that M.alba L.had large biomass,which could be used for heavy metal-contaminated soil ecological remediation and landscape revegetation.The dry biomass of M.alba L.could reach up to 4 kg·plant-1 after 5 years cultivation in the field.Meanwhile,M.alba L.could effectively transport and accumulate heavy metals from the contaminated soil to some extent.The contents of heavy metals such as Cd,Zn,and Mn in the aboveground parts were significantly higher than those in the roots,particularly for metals in leaves were higher than those in branches and trunks.The accumulation amounts of Zn and Mn in the aboveground parts of M.alba L.could reach up to 3277.7 and 2422.4 mg·100 m-2 after 5 years remediation.Furthermore,total Mn and Zn content in soil decreased from 2192.5 mg·kg-1 to 1790.0 mg·kg-1 and 103.2 mg·kg-1 to 85.94 mg·kg-1,meanwhile available Mn and Zn in soil also significantly(P<0.05)decreased by 66.0%and 28.6%,respectively.However,the contents of Cd,Zn,and Mn in deciduous leaves could reach up to 0.36,64.5,and 189.2 mg·kg-1,respectively.Therefore,regularly removing leaves or cutting the parts of aboveground could prevent secondary contamination from heavy metals in deciduous leaves,which could also reduce heavy metal contents in the contaminated soil.Simultaneously,the availabilities of nitrogen(N),phosphorus(P),and potassium(K)in contaminated soil were significantly(P<0.05)decreased after 5 years phytoremediation with M.alba L.Therefore,it is necessary to strengthen the potential of ecological remediation with M.alba L.in the tail-mining area by adding corresponding N,P and K fertilizers at regular periods.