Koelmans Albert A, Meulman Brendo, Meijer Thijs, Jonker Michiel T O
Aquatic Ecology and Water Quality Management Group, Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
Environ Sci Technol. 2009 Feb 1;43(3):736-42. doi: 10.1021/es802862b.
Strong sorption to black carbon may limit the environmental risks of organic pollutants, but interactions with cosorbing humic acid (HA) may interfere. We studied the attenuative effect of HA additions on the sorption of polychlorinated biphenyls (PCBs) to a charcoal. "Intrinsic" sorption to HA-amended charcoal was calculated by subtracting the sorption contribution of HA from the total sorption to charcoal and HA. Association of PCBs with HA was proportional to hydrophobicity. However, the planar PCBs 77 and 126 had an additional 2-4 times stronger association than expected from hydrophobicity alone. Sorption isotherms for the raw charcoal fitted slightly better to a three-parameter Polanyi-Dubinin-Manes model than to a two-parameter Langmuir model. Preloading the charcoal with 1-75 mg of HA/g of charcoal increasingly attenuated sorption to charcoal with up to a factor of 10. The resultant isotherms could be described adequately with the Freundlich model. Isotherm nonlinearity increased with HA loading, suggesting increased sorption competition between HA and PCBs. Attenuation was negligible in the PCB picogram per liter to nanogram per liter range and increased at higher PCB concentrations, which points to saturation of binding sites on the charcoal. Attenuation was highest for planar congeners, which suggests an additional site blockage mechanism. These variations due to HA loading and PCB concentration can explain the variability in attenuation reported in earlier work and imply that the use of constant "attenuation factors" to adjust sorption coefficients determined for pure carbonaceous materials in order to apply them to field situations may not be warranted.
对黑碳的强吸附作用可能会限制有机污染物的环境风险，但与共吸附腐殖酸（HA）的相互作用可能会产生干扰。我们研究了添加HA对多氯联苯（PCBs）吸附到木炭上的衰减效应。通过从对木炭和HA的总吸附量中减去HA的吸附贡献，计算出对HA改性木炭的“本征”吸附。PCBs与HA的缔合与疏水性成正比。然而，平面PCBs 77和126的缔合作用比仅由疏水性预期的要强2至4倍。原始木炭的吸附等温线与三参数的Polanyi-Dubinin-Manes模型的拟合略优于二参数的Langmuir模型。用1至75毫克HA/克木炭对木炭进行预加载，会使对木炭的吸附衰减增加，最高可达10倍。所得等温线可用Freundlich模型充分描述。等温线非线性随HA负载量增加，表明HA与PCBs之间的吸附竞争加剧。在每升皮克至每升纳克的PCB浓度范围内，衰减可忽略不计，而在较高的PCB浓度下衰减增加，这表明木炭上的结合位点饱和。平面同系物的衰减最高，这表明存在额外的位点阻塞机制。由于HA负载量和PCB浓度导致的这些变化可以解释早期工作中报道的衰减变异性，并意味着使用恒定的“衰减因子”来调整为纯碳质材料确定的吸附系数以便将其应用于现场情况可能并不合理。
