Effects of a non-ionic surfactant (Tween-80) on the mineralization, metabolism and uptake of phenanthrene in wheat-solution-lava microcosm

Effects of a non-ionic surfactant (Tween-80) on the mineralization, metabol ism and uptake of phenanthrene in wheat-solution-lava microcosm were studie d using C-14-labeled phenanthrene. The mineralization and metabolism of phe nanthrene were fast in such a system. At least 90% of the applied phenanthr ene were transformed within 24 days. Only 0.3% of the applied C-14-activity were identified to be the parent phenanthrene. Most of the applied C-14-ac tivity (70%) was recovered from wheat, in which ca. 70% were associated wit h wheat shoots (stems and leaves) and ca. 30% wheat roots. 33% and 20% of t he applied C-14-activity had been constructed into wheat tissues of shoots and roots, respectively. The C-14-activity recovered in forms Of CO2 and vo latile organic chemicals (VOCs) was 12-16% and 4-5%, respectively. The majo r metabolites of phenanthrene were polar compounds (18% of the applied C-14 ) and only 2.1% were identified as non-polar metabolites. No phenanthrene w as found in wheat shoots indicating that it could not be transported from r oots to upper parts of the plant but in form of metabolites (mostly polar m etabolites). Foliar uptake of C-14-activity via air in form of (CO2)-C-14 o ccurred. The presence of Tween-80 significantly enhanced the degradation of phenanthrene, which could be attributed to its increase of microbial activ ities in the system. Tween-80 also significantly (P < 0.05) reduced the phe nanthrene level in wheat roots, which probably resulted from desorption of phenanthrene from root surface caused by the surfactant. (C) 2001 Elsevier Science Ltd. All rights reserved.