Cornelissen Gerard, Gustafsson Orjan
Institute for Applied Environmental Research (ITM), Stockholm University, 10691 Stockholm, Sweden.
Environ Sci Technol. 2004 Jan 1;38(1):148-55. doi: 10.1021/es034776m.
Strong sorption to soot- and charcoal-like material (collectively termed black carbon or BC) in soils and sediments is possibly the reason for recent observations of elevated geosorbent-water distribution ratios, slow desorption, limited uptake, and restricted bioremediation. We evaluated the role of environmental BC in the sorption of phenanthrene (PHE) to a polluted lake sediment from a Rhine River sedimentation area. Sorption isotherms were determined over a wide concentration range (0.0005-6 microg/ L) for the original sediment (with organic matter or OM, native sorbates, and BC), sediment from which we had stripped > 90% of the native sorbates (only OM and BC), and sediment combusted at 375 degrees C (only BC). The sorption isotherms of the original and stripped sediments were almost linear (Freundlich coefficient or n(F) > 0.9), whereas the isotherm of the BC remaining after the sediment combustion was highly nonlinear (n(F) = 0.54). At low concentrations (ng/L range), PHE sorption to BC in the combusted sediment was found to exceed the total PHE sorption in the original and stripped sediments. This implies that it may not be possible to use a BC-water sorption coefficient measured in combusted sediment to estimate total sorption to the original sediment. This "intrinsic" BC-water sorption coefficient after combustion was calculated to be 9 times larger than the "environmental" one in the untreated sediment. Competition between the added PHE and the native PAHs and/or OM may explain this difference. It appears that, at low aqueous PHE concentrations (ng/L and below), BC is the most important geosorbent constituent with respect to sorption. At higher concentrations (microg/L), BC sorption sites become saturated and BC sorption is overwhelmed by sorption to the other OM constituents. Because sorption is a central process affecting contaminant behavior and ecotoxicity, understanding this process can strongly contribute to risk assessment and fate modeling.
土壤和沉积物中对烟尘和木炭状物质（统称为黑碳或BC）的强烈吸附，可能是近期观测到的地球吸附剂-水分配比升高、解吸缓慢、吸收有限以及生物修复受限的原因。我们评估了环境BC在菲（PHE）吸附到莱茵河沉积区受污染湖泊沉积物中的作用。在较宽的浓度范围（0.0005 - 6微克/升）内，测定了原始沉积物（含有有机质或OM、天然吸附质和BC）、去除了> 90%天然吸附质的沉积物（仅含OM和BC）以及在375℃燃烧后的沉积物（仅含BC）的吸附等温线。原始沉积物和去除吸附质后的沉积物的吸附等温线几乎呈线性（弗伦德利希系数或n(F)> 0.9），而沉积物燃烧后剩余BC的等温线高度非线性（n(F)= 0.54）。在低浓度（纳克/升范围）下，发现燃烧后沉积物中PHE对BC的吸附超过了原始沉积物和去除吸附质后的沉积物中PHE的总吸附量。这意味着，可能无法使用在燃烧后沉积物中测得的BC - 水吸附系数来估算对原始沉积物的总吸附量。燃烧后这种“本征”的BC - 水吸附系数经计算比未处理沉积物中的“环境”吸附系数大9倍。添加的PHE与天然多环芳烃和/或OM之间的竞争可能解释了这种差异。看来，在低水相PHE浓度（纳克/升及以下）时，就吸附而言，BC是最重要的地球吸附剂成分。在较高浓度（微克/升）时，BC吸附位点饱和，BC吸附被其他OM成分的吸附所掩盖。由于吸附是影响污染物行为和生态毒性的核心过程，了解这一过程对风险评估和归宿建模有很大帮助。
