城区交通干道绿化带土壤-植物系统汞、砷污染研究

摘要

为了解城区交通于道土壤-植物系统中汞(Hg)和砷(As)的污染特征,以聊城市为例,在其城区主要交通干道旁绿化带内采集表层土壤样品并同步采集扁竹兰(Iris confusa)、侧柏(Platycladus orientalis)、冬青(Ilex chinensis)、马尼拉草(Zoysia matrella)和石楠(Photinia serrulata)等5种常见绿化植物测定Hg和As含量.采用单因子指数法、综合指数法和潜在生态危害指数法对土壤Hg和As的污染水平及其潜在生态危害进行了评价,并采用富集系数法分析了绿化带植物对土壤中Hg和As的富集能力.结果表明,聊城市绿化带土壤Hg和As质量分数分别在0.17～6.21 mg·kg1和1.18～12.22 mg.kg1之间,20％样品Hg含量超过《土壤环境质量标准》(GB15618-1995) Ⅲ级标准.以山东省土壤背景值为评价标准,Hg表现为严重污染,其潜在生态危害很高,As表现为轻度污染和轻微的生态危害.绿化带植物中Hg和As质量分数分别在0.03～0.72 mg·kg-1和0.06～1.86 mg·kg-1之间,平均值分别为0.25 mg·kg-1和0.55 mg·kg-1;植物体内Hg的富集系数在0.01～2.82之间,平均值表现为:马尼拉草＞石楠＞扁竹兰＞侧柏＞冬青;植物体内As的富集系数在0.01～0.65之间,平均值表现为马尼拉草＞侧柏＞冬青＞石楠＞扁竹兰.绿化带植物对Hg污染具有一定的修复作用,对As污染不具有修复效果,不同植物中Hg和As的含量以及对Hg和As的生物富集系数均无显著性差异(P＞0.05),这可能与植物本身的生理特性、种植时间及绿化带土壤环境条件有关,具体原因有待进一步探讨.%In order to understand the mercury (Hg) and arsenic (As) pollution characteristics of soil-plant system in urban main traffic road,samples of surface soil and five common green plants including Iris confusa,Platycladus orientalis,Ilex chinensis,Zoysia matrella and Photinia serrulata were collected in the green belt of Liaocheng urban main roads to determine the concentrations of Hg and As.Using the soil background concentrations in Shandong Province as standards,single factor index,comprehensive index and potential ecological risk index methods were applied to assess the degree and risk of Hg and As contamination,and bioaccumulation factor (BCF) was calculated to analyze the enrichment capability of green belt plants for Hg and As in soil.The results showed that the Hg and As mass fraction in green belt soil were 0.17～6.21 mg·kg-1 and 1.18～12.22 mg·kg-1 respectively.Hg mass fraction in 20％ of the sampling sites were higher than the class Ⅲ limit value of environmental quality standard for soils in China (GB15618-1995).Hg pollution in the green belt soil was very severe and posed very high potential ecological risk,while As pollution was slight and its ecological risk was low.The mass fraction of Hg in the green plants were 0.03～0.72 mg·kg-1 with an average of 0.25 mg·kg-1,and 0.06～1.86 mg·kg-1 with an average of 0.55 mg·kg-1 for As.The mercury bioaccumulation factors of green plants were between 0.01 and 2.82,and the average values of green plants descended as follows:Zoysia matrella＞Photinia serrulata＞Iris confusa＞Platycladus orientalis＞llex chinensis.The arsenic bioaccumulation factors were between 0.01 and 0.65,and the average values were in the order of Zoysia matrella＞Platycladus orientalis＞llex chinensis＞Photinia serrulata＞Iris confusa.Green plants showed bioaccumulation of Hg from soil in some sampling sites but not for As.There were no significant differences (P＞0.05) in the concentrations of Hg and As between different types of plants,and were neither in their bioaccumulation factors,which might be related to the plant physiological characteristics,planting time and the physicochemical properties of green belt soil.The effect of herb and shrub plants in green belt on remediation of heavy metals still needs to be further studied.