阿哈水库底泥基质中3种绿化植物的生长及Cd的富集特征

阿哈水库底泥的重金属潜在危害程度为中等,其中以Cd的贡献最大。以阿哈水库疏浚底泥为材料,采用盆栽试验研究了70%的底泥与珍珠岩、木屑、蘑菇渣和茶园土组成的基质对种植的三叶草、黑麦草和孔雀草生长情况的影响及Cd在植株内的富集特征。结果表明:1)配制的底泥基质有机质的含量范围为78.30～95.31 g·kg^-1,速效氮为109.33～124.45 mg·kg^-1,速效磷为17.20～24.70 mg·kg^-1,速效钾为178.12～206.46 mg·kg^-1,pH为7.62～7.71,总孔隙度为42%～75%,电导率(EC)为1.47～1.62 ms·cm^-1,Cd为0.88～1.12 mg·kg^-1,满足CJ/T 340-2011的要求,同时,由于木屑、蘑菇渣的养分含量高于珍珠岩和茶园土,所以木屑、蘑菇渣所占比重较大的T_5(70%底泥+10%珍珠岩+10%木屑+10%蘑菇渣)、T_3(70%底泥+15%珍珠岩+10%蘑菇渣+5%茶园土)和T_4(70%底泥+15%珍珠岩+10%木屑+5%茶园土)养分含量大于T_2(70%底泥+30%珍珠岩)和T_1(70%底泥+30%茶园土),此外,调节孔隙度能力为珍珠岩>木屑>蘑菇渣>茶园土,经调节后,孔隙度较大的为T_2、T_5、T_3和T_4,所以,T_5为本次试验理化性质最优基质。2)种植的三叶草、黑麦草和孔雀草的鲜重分别为127.63、37.51、61.02 g·盆^-1,干重为15.37、4.62、9.91 g·盆^-1,三叶草长势最好,其次是孔雀草。3)三叶草、黑麦草和孔雀草地上部分Cd的含量分别为0.10～0.14 mg·kg^-1、0.21～0.31 mg·kg^-1和0.93～1.22 mg·kg^-1,地下部分Cd的含量分别为0.04～0.15 mg·kg^-1、4.32～4.98 mg·kg^-1和0.40～0.93 mg·kg^-1,除黑麦草地下部分的Cd含量超过一般植物正常Cd含量0.2～3.0 mg·kg^-1外,三叶草和孔雀草植株Cd含量均在正常范围内,同时,孔雀草的Cd累积量为7.46～12.60μg·盆^-1,远大于三叶草和黑麦草的1.03～2.24μg·盆^-1、2.73～3.72μg·盆^-1。4)黑麦草地下部分的Cd富集系数为3.96～5.01,孔雀草地上和地下部分的Cd富集系数分别为0.93～1.11和0.37～1.06,而黑麦草地上部分和三叶草的Cd富集系数均小于0.31,且三叶草、黑麦草和孔雀草的Cd转移系数为0.67～3.23、0.05～0.07、1.00～2.52,可见,黑麦草为Cd根富集植物,孔雀草和三叶草是Cd地上部富集植物。综上,可以利用阿哈水库底泥制成基质种植三叶草、黑麦草和孔雀草,同时可利用其去除部分底泥中重金属,为阿哈水库及类似的喀斯特山区湖泊污染整治工程提供参考资料。

Growth and Cd accumulation characteristics of three representative plant species in artificial soils incorporating sediment substrate of the Aha Reservoir

The sediment in the Aha Reservoir has a moderate potential hazard classification, which with the largest contribution to the potential hazard being from Cd. This study comprised a pot experiment to compare the accumulation of Cd in roots and shoots of Oxalis triangularis, Lolium perenne and Tagetes patula so as to assess the potential suitability of those species for remediation applications. Sediment from the Aha Reservoir was used either alone (control) or mixed with perlite, wood sawdust, mushroom residue or tea garden soil to test a range of planting substrates. It was found that: 1) Excluding the control, the soil chemical property ranges were: organic matter content of the substrate, 78.30 to 95.31 g·kg^-1; available nitrogen, 109.33 to 124.45 mg·kg^-1; available phosphorus 17.20 to 24.7 mg·kg^-1; available potassium, 178.12 to 206.46 mg·kg^-1; pH, 7.62 to 7.71; total porosity, 42% to 75%; electrical conductivity, 1.47 to 1.62 ms·cm^-1; and Cd concentration, 0.88 to 1.14 mg·kg^-1. Those specifications exceeded the requirements of the standard, CJ/T 340-2011, and pH, total porosity and Cd were values were suitable for the growth needs of common plants. Considering all soil properties, T₅ was the substrate with the best physical and chemical plant growth environment. 2) The fresh weigh and dry weight of O. triangularis, L. perenne and T. patula were 127.63, 37.51, and 61.02 g·pot^-1 and 15.37, 4.62, and 9.91 g·pot^-1, respectively. The ranking for biomass was O. triangularis>T. patula>L. perenne. 3) The concentrations of Cd in O. triangularis, L. perenne and T. patula ranged from 0.10 to 0.14, 0.21 to 0.31 and 0.93 to 1.22 mg·kg^-1, respectively. The cumulative Cd uptake of Cd by T. patula was 7.46 to 12.60 μg·pot^-1, which was much larger than the values of 1.03 to 2.24 μg·pot^-1 and 2.73 to 3.72 μg·pot^-1 for O. triangularis and L. perenne, respectively. 4) The bioconcentration factor of L. perenne roots ranged from 3.96 to 5.01, while corresponding values for the aboveground organs and roots of T. patula were 0.93 to 1.11, and 0.37 to 1.06, respectively, and for O. triangularis and the shoots of L. perenne were less than 0.31. In addition, the translocation factors of O. triangularis, L. perenne and T. patula were 0.67 to 3.23, 0.05 to 0.07 and 1.00 to 2.52, which highlights plant species differences, with L. perenne accumulating Cd in the root system, O. triangularis and T. patula accumulating Cd in the shoot system. In conclusion, T. patula, O. triangularis and L. perenne are all capable of healthy growth and Cd extraction from a Cd-rich sediment substrate, and among the three, O. triangularis is recommended for lake sediment remediation projects, because of its higher biomass production.