可溶性有机物对玉米根部菲与芴吸着与吸收过程的影响

在水培玉米幼苗的暴露实验中，控制溶液中可溶性有机物（DOM）的浓度水平（0、0．5、1、2、5、10mg·L^-1），观察其对水培溶液中多环芳烃（芴与菲）生物有效性的影响。通过控制洗脱条件，将根部多环芳烃分为弱吸着（氯化钙提取）、强吸着（甲醇提取）与吸收（索氏提取）3种不同的形态。结果表明，短期暴露（4d）后，培养液中多环芳烃浓度迅速下降至起始浓度的10％左右，玉米幼苗对菲的吸收强于对芴的吸收，而吸着量相似，大部分以强吸着态存在于根表。低浓度可溶性有机物（小于2mg·L^-1）的加入有助于芴与菲在根表的吸着，浓度继续增大时，对吸着过程则产生抑制作用；吸收量随可溶性有机物浓度的升高而增大，逐渐趋于稳定。吸着与吸收总量在DOM浓度约为1mg·L^-1时达到最大值，之后随DOM浓度增加而下降。

Impact of Dissolved Organic Matter on Sorption and Absorption of Fluorene and Phenanthrene to Maize Root

Impact of dissolved organic matter on phyton-bioavailability of fluorene and phenanthrene to maize seedling was studied through hydroponic exposure experiments to simulate the plant uptake of fluorene and phenanthrene from the soil solution. Fluorene and phenanthrene combinded with maize seedling＇s root were divided into three parts, weakly adsorbed, strongly adsorbed on root surface, and interior absorbed fraction in root tissues in this study. Fluorene and phenanthrene concentration of the culture solution was controlled at 253.5ug·L^-1 and 244.5 ug·L^-1 respectively, with dissolved organic matter concentration of 0, 0.5, 1, 2, 5 and 10 mg·L^-1. Fluorene and phenanthrene weakly adsorbed and strongly adsorbed on root surface were rinsed by calcium chloride and methanol in sequence and the interior absorbed fraction in root tissues were eluted by Soxhlet＇ s apparatus with acetone and dichloromethane （ 1： 1 ）. After four days＇ exposure, fluorene and phenanthrene concentration in culture solution dropped to 8.29 ug·L^-1 and 8.55 ug·L^-1. With added dissolved organic matter concentration below 2 mg·L^-1, sorption of fluorene and phenanthrene were improved when dissolved organic matter concentration increased. While dissolved organic matter concentration rose above 2 mg·L^-1, sorption of fluorene and phenanthrene were inhibited. Steep increase of fluorene and phenanthrene concentration in maize root was observed at the front-end of the curve （concentration of dissolved organic matter ≤ 2 mg·L^-1）and then tended towards constant with 0.8 ug·g^-1 and 2ug·g^-1, respectively. Total amount of adsorbed and absorbed lluorene and phenanthrene reached maximum level at dissolved organic matter concentration of 1 -2 mg·L^-1, and then decreased while more dissolved organic matter added in culture solution. Similar amount of fluorene and phenanthrene were adsorbed on root surface but more phenanthrene transported into root tissue, that mainly due to their hydrophobic properties.