三种添加剂对矿冶区多种重金属污染土壤的修复效果评估——大豆苗期盆栽实验

Assessment of three chemical additives for remediation of heavy metal contaminated soils from mining and smelting areas: A seedling pot trial using soybeans

以湖南省水口山矿冶区周边的农田土壤为供试土壤,通过人工添加化学改良剂的植物盆栽实验,研究了添加不同量的赤泥(质量分数1%、2%、5%)、磷灰石(质量分数1%、2%、5%)、亚硒酸钠(0.1、1、5 m.gkg-1,以硒计)对苗期大豆生长及其吸收重金属As、Cd、Cu、Pb、Zn的影响.结果表明,添加5%赤泥明显提高了土壤的pH值,同时降低了土壤中重金属有效态含量,在5%赤泥处理条件下,Cd、Cu、Pb、As、Zn有效态含量仅为对照(不加任何添加剂)的15.71%、38.62%、19.23%、36.00%、46.35%.添加磷灰石也明显降低了土壤中重金属的有效态含量,硒对土壤重金属有效态含量没有显著影响.除5 m.gkg-1硒处理外,实验中其他所有不同水平处理的添加剂均显著促进了大豆的生长,其中以1 m.gkg-1硒处理效果最佳,该处理下大豆生物量和株高分别比对照提高了145%和39%.在对照处理中,大豆苗株地上部分Pb、Cd含量分别为12.2、13.8 m.gkg-1,超过陆地植物地上部重金属含量的上限值,其它重金属含量均在正常范围之内.加入添加剂后,大豆地上部Pb、Cd含量明显下降,其中,5%赤泥处理下大豆地上部Pb含量较对照降低72%,0.1 m.gkg-1硒处理下大豆地上部Cd含量降至最低,较对照降低了89.7%.3种添加剂还明显抑制了大豆幼苗对Cd和Pb的生物富集,减少了Cd、Cu、Pb、As元素从根部向大豆地上部分的转移.总体而言,3种添加剂均在一定程度上降低了重金属复合污染土壤地区的生态及健康风险,其中以硒的效果最为明显;赤泥和磷灰石可改变土壤中重金属的形态,降低其有效态含量,减少大豆对重金属的吸收,从而促进大豆生长;而硒则可能更多地通过元素拮抗作用来降低大豆对重金属的吸收富集.

This study was conducted to investigate the effects of three additives（red mud,apatite and selenite） on the growth and heavy metal uptake of soybeans grown in multiple heavy metal contaminated soils collected from the mining area in Shuikoushan,Hunan province,China The addition of red-mud（1%,2% and 5%）,apatite（1%,2% and 5%） and selenite（0.1 and 1 mg·kg-1 Se） all significantly improved the growth of soybeans,especially when 1 mg·kg-1 Se was added,with an up to 145% increase of the fresh biomass and 39% increase of dry weight,as compared with the control.Without additives,the average concentrations of Pb and Cd in the aboveground parts of the soybean plants were 12.2 mg·kg-1 and 13.8 mg·kg-1,respectively,being much higher than those for normal terrestrial vascular plants;while concentrations of other heavy metals fell in normal ranges.The uptake of Pb and Cd in soybean were obviously inhibited by the above three additives.Additions of 0.1 mg·kg-1Se and 5% red mud were more efficient than that of apatite in decreasing Pb accumulation in the aboveground soybean tissues,with reductions of 67% and 72% compared to the control,respectively;0.1 mg·kg-1 Se treatment had the highest efficiency in decreasing Cd accumulation in the aboveground parts of the soybean plants,with a drop of 89.7% as compared with the control.All three additives depressed the translocation factors of Cd,copper（Cu）,Pb,and As,and bioaccumulation of Pb and Cd in soybean as well.Addition of additives significantly reduced the bioavailability of heavy metals in the soils.Treatment with 5% red mud was the most efficient,with bioavailable concentrations of Cd,Cu,Pb,Zn and As in the soils measured as 15.71%、38.62%、19.23%、36.00%、46.35% of those in the control,respectively.The results indicated that red mud and apatite might directly inhibit the uptake of heavy metals in soybean through reducing the bioavailability of heavy metals in the soils,whereas Se decreases the accumulations of heavy metals mainly via elemental antagonism.Consequently,additives of red mud,apatite and selenite could efficiently reduce the ecological and health risks generated from multiple heavy metal contaminated soils,with Se the preferred choice.