Olson P E, Flechter J S, Philp P R
Colorado State University, Department of Biology, Fort Collins, CO 80523, USA.
Environ Sci Pollut Res Int. 2001;8(4):243-9. doi: 10.1007/BF02987400.
The natural attenuation of polyaromatic hydrocarbons (PAHs) in the vadose zone of a naturally revegetated former industrial sludge basin (0.45 ha) was examined. This was accomplished by comparing the concentration of 16 PAH contaminants present in sludge collected below the root zone of plants with contaminants present at 3 shallower depths within the root zone. Chemical analysis of 240 samples from 60 cores showed the average concentration of total and individual PAHs in the 0-30 cm, 30-60 cm, and bottom of the root zone strata were approximately 10, 20, and 50%, respectively, of the 16, 800 ppm average total PAH concentration in deep non-rooted sludge. Statistically significant differences in average PAH concentrations were observed between each strata studied and the non-rooted sludge except for the concentrations of acenaphthene and chrysene present at the bottom of the root zone in comparison to sludge values. The rooting depth of the vegetation growing in the basin was dependent on both vegetation type and plant age. Average rooting depths for trees, forbs (herbaceous non-grasses), and grasses were 90, 60, and 50 cm, respectively. The deepest root systems observed (100-120 cm) were associated with the oldest (12-14 year-old) mulberry trees. Examination of root systems and PAH concentrations at numerous locations and depths within the basin indicated that plant roots and their microbially active rhizospheres fostered PAH disappearance; including water insoluble, low volatility compounds, i.e. benzo(a)pyrene and benzo(ghi)perylene. The reduced concentration of PAHs in the upper strata of this revegetated former sludge basin indicated that natural attenuation had occurred. This observation supports the concept that through appropriate planting and management practices (phytoremediation) it will be possible to accelerate, maximize, and sustain natural processes, whereby even the most recalcitrant PAH contaminants (i.e. benzo(a)pyrene) can be remediated over time.
对一个自然植被恢复的 former industrial sludge basin（0.45公顷）包气带中多环芳烃（PAHs）的自然衰减情况进行了研究。通过比较植物根区以下收集的污泥中存在的16种PAH污染物浓度与根区内3个较浅深度处存在的污染物浓度来实现这一点。对来自60个岩芯的240个样本进行化学分析表明，根区地层的0 - 30厘米、30 - 60厘米和底部中总PAHs和单个PAHs的平均浓度分别约为深层无根污泥中16,800 ppm平均总PAH浓度的10%、20%和50%。除了根区底部存在的苊和屈的浓度与污泥值相比外，在所研究的每个地层与无根污泥之间观察到平均PAH浓度存在统计学上的显著差异。盆地中生长的植被的生根深度取决于植被类型和植物年龄。树木、杂草（非禾本科草本植物）和草的平均生根深度分别为90厘米、60厘米和50厘米。观察到的最深根系（100 - 120厘米）与最老（12 - 14岁）的桑树有关。对盆地内多个位置和深度的根系和PAH浓度进行检查表明，植物根系及其具有微生物活性的根际促进了PAH的消失；包括水不溶性、低挥发性化合物，即苯并(a)芘和苯并(ghi)苝。这个植被恢复的 former sludge basin上层中PAHs浓度的降低表明发生了自然衰减。这一观察结果支持了这样一个概念，即通过适当的种植和管理措施（植物修复），有可能加速、最大化和维持自然过程，从而随着时间的推移，即使是最难降解的PAH污染物（即苯并(a)芘）也可以得到修复。
