Root Exudate Enhanced Contaminant Desorption: An Abiotic Contribution to the Rhizosphere Effect
Root Exudate Enhanced Contaminant Desorption: An Abiotic Contribution to the Rhizosphere Effect
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DOI：
10.1021/es402446v
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发表时间：
2013-10-15
影响因子：
11.4
通讯作者：
Novak, Paige J.
中科院分区：
文献类型：
--
作者：
LeFevre, Gregory H.;Hozalski, Raymond M.;Novak, Paige J.
尽管文献中报道了植物根区中的上级污染物降解，但人们对这种被称为根际效应的现象知之甚少。我们研究了根系分泌物是否可以增强残留污染物的解吸，从而提高生物利用度和随后的生物降解潜力。从三种水培生长的植物中收获根系分泌物，并使用文献配方创建人工根系分泌物（战神）。通过土壤细菌代谢等份的渗出物，以研究生物转化的渗出物是否表现出不同的化学特性或对污染物的生物有效性有不同的影响，比'原渗出物。含有原始渗出物的萘老化土壤的泥浆比含有代谢渗出物或无渗出物对照的泥浆具有显著更低的土壤-水分配系数（K-d），分别表现出50%和55%的中值降低。原渗出物有一个显着降低的表面张力，而不增加整体溶解度，表明存在的表面活性化合物低于临界胶束浓度，这是一个新观察到的根际效应的机制。渗出液样品的特征在于特定的UV吸光度，光谱斜率，荧光指数，和激发-发射矩阵。在有机碳的字符前和代谢后，收获的分泌物和战神之间的实质性变化，表明战神是不具有化学代表性的植物根系分泌物。总体而言，我们提出的证据表明，在渗出物的存在下，增强污染物解吸提供了一个非生物的贡献根际效应。
Despite reports in the literature of superior contaminant degradation in the root-zone of plants, this phenomenon, known as the rhizosphere effect, is poorly understood. We investigated whether root exudates could enhance desorption of residual pollutants, thus improving bioavailability and subsequent biodegradation potential. Root exudates were harvested from three species of hydroponically grown plants, and artificial root exudates (AREs) were created using a literature recipe. Aliquots of the exudates were metabolized by soil bacteria to investigate whether biotransformed exudates exhibited different chemical characteristics or had different effects on contaminant bioavailability than 'raw exudates.' Slurries of naphthalene-aged soil containing raw exudates had a significantly lower soil-water distribution coefficient (K-d) than slurries with metabolized exudates or no-exudate controls, exhibiting median reductions of 50% and 55%, respectively. Raw exudates had a significantly lower surface tension while not increasing overall solubility, indicating the presence of surface-active compounds below the critical micelle concentration; this is a newly observed mechanism of the rhizosphere effect. Exudate samples were characterized by specific UV absorbance, spectral slope, fluorescence index, and excitation-emission matrices. Substantial changes in organic carbon character pre- and postmetabolism, and between harvested exudates and AREs, suggest that AREs are not chemically representative of plant root exudates. Overall, we present evidence that enhanced contaminant desorption in the presence of exudates provides an abiotic contribution to the rhizosphere effect.