Leppänen Matti T, Landrum Peter F, Kukkonen Jussi V K, Greenberg Marc S, Burton G Allen, Robinson Sander D, Gossiaux Duane C
Institute for Environmental Quality, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, USA.
Environ Toxicol Chem. 2003 Dec;22(12):2861-71. doi: 10.1897/02-541.
Only a fraction of all sediment-associated hydrophobic organic contaminants are bioavailable, and a simple Tenax extraction procedure may estimate this fraction. Bioavailability is assumed to coincide with the rapidly and, possibly, slowly desorbing sediment-associated contaminant. River sediment was spiked with radiolabeled (14C) and nonradiolabeled (12C) 3,4,3',4'-tetrachlorobiphenyl (TCBP), and desorption kinetics using Tenax extraction were obtained at 10 degrees C and 22 degrees C. Bioaccumulation was measured in Lumbriculus variegatus, Chironomus tentans, and Hyalella azteca. Desorption of TCBP was triphasic at 22 degrees C and slowed at 10 degrees C to show only biphasic kinetics. The rapidly desorbing fractions decreased with increasing TCBP sediment concentration. The biota sediment accumulation factors, biota accumulation factors, and sediment clearance coefficients (ks) also decreased with increasing sediment TCBP concentration. The rapidly plus slowly desorbing fractions and the total TCBP desorbed when 99.9% of the rapidly desorbing fraction had desorbed were used to estimate bioavailable TCBP. These Tenax-based fractions did not explain the decreasing bioavailability with increasing TCBP load. Several factors, such as animal behavior and TCBP water solubility limitations, were evaluated to explain the concentration effect, but the most likely cause was severe diffusion limitations in whole sediment that were not predicted by the fully mixed Tenax extraction. Therefore, desorbing fractions determined by Tenax extraction overestimated the bioavailable fractions in sediments.
所有与沉积物相关的疏水性有机污染物中，只有一小部分具有生物可利用性，一种简单的Tenax萃取程序可以估算这一部分。生物可利用性被认为与沉积物中快速且可能缓慢解吸的污染物相吻合。在河流沉积物中加入放射性标记（14C）和非放射性标记（12C）的3,4,3',4'-四氯联苯（TCBP），并在10℃和22℃下通过Tenax萃取获得解吸动力学。在颤蚓、摇蚊幼虫和墨西哥高原钩虾中测量生物累积。TCBP在22℃下的解吸呈三相，在10℃下减缓，仅显示双相动力学。快速解吸部分随着TCBP沉积物浓度的增加而减少。生物群沉积物累积因子、生物累积因子和沉积物清除系数（ks）也随着沉积物中TCBP浓度的增加而降低。当99.9%的快速解吸部分解吸时，快速加缓慢解吸部分以及解吸的总TCBP被用于估算生物可利用的TCBP。这些基于Tenax的部分并不能解释随着TCBP负荷增加生物可利用性降低的现象。评估了几个因素，如动物行为和TCBP的水溶性限制，以解释浓度效应，但最可能的原因是整个沉积物中严重的扩散限制，这是完全混合的Tenax萃取无法预测的。因此，通过Tenax萃取确定的解吸部分高估了沉积物中的生物可利用部分。
