TIME-DEPENDENCY OF NAPHTHALENE SORPTION IN SOIL: SIMPLE RATE-, DIFFUSION-, AND ISOTHERM-PARAMETER-BASED MODELS
TIME-DEPENDENCY OF NAPHTHALENE SORPTION IN SOIL: SIMPLE RATE-, DIFFUSION-, AND ISOTHERM-PARAMETER-BASED MODELS
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DOI：
10.1097/01.ss.0000128011.69526.e6
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发表时间：
2004-05
期刊：
影响因子：
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通讯作者：
J. Gamst;P. Møldrup;D. Rolston;K. Scow;K. Henriksen;T. Komatsu
中科院分区：
文献类型：
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作者：
J. Gamst;P. Møldrup;D. Rolston;K. Scow;K. Henriksen;T. Komatsu
吸附机理和动力学在很大程度上决定了污染物在土壤中的归宿和生物有效性。在这项研究中，萘吸附的时间发展进行了测量，在四种土壤，并显示不断增加的吸附随着时间的推移。两种基于机理的分析模型拟合到吸附动力学数据：（i）双R吸附K_（max）模型（TRSK）和（ii）具有初始吸附容量Xi的颗粒内扩散模型（ID）。两种模型都很好地描述了测量数据，TRSK模型提供了最佳拟合（最低均方根误差）。虽然这两个模型在数学上是不同的，但两个模型中描述缓慢吸附速率的参数（ID中的有效扩散系数Da/l2，TRSK中的缓慢速率系数rs）显示出相当的值。Da/l2和rs均表现出轻微的浓度依赖性。不同时间尺度下测定的吸附等温线均符合Freundlich方程，Freundlich系数K′F随时间增加而增大。Freundlich指数n′a在短时间内（t4 d）下降。经验的两项K′F（t）模型与Freundlich指数n′a（定义为在t > 4天时测得的n′a）的常数值一起使用，对不同时间尺度下测得的吸附进行了良好的预测，代表了ID和TRSK模型的简单替代方案。使用两项K′F（t）模型计算萘阻滞因子作为时间的函数R（t），表明在评估短期和长期萘在土壤中的迁移性时，吸附非线性非常重要，并且通常会掩盖吸附时间依赖性的影响。
SORPTION mechanisms and kinetics govern contaminant fate and bioavailability in soil to a great extent. In this study, temporal development of naphthalene sorption was measured on four soils and showed continuously increasing sorption with time. Two mechanistically based analytical models were fitted to the sorption kinetics data: (i) a T wo-R ate S orption K inetics model (TRSK) and (ii) an I ntraparticle D iffusion model (ID) with an initial sorption capacity, Xi. Both models described measured data well, with the TRSK model providing the best fit (lowest root mean square error). Although the two models are mathematically different, the parameters describing the slow sorption rate in the two models (in ID the effective diffusion coefficient, Da/l2, and in TRSK the slow rate coefficient, rs) exhibited comparable values. Both Da/l2 and rs showed a minor concentration dependency. Sorption isotherms measured at different time scales were described well by the Freundlich equation and showed that the Freundlich coefficient, K′F, increased with time. The Freundlich exponent, n′a, decreased at short sorption times (t 4 days). An empirical, two-term K′F(t) model, used together with a constant value of the Freundlich exponent, n′a (defined as n′a measured at t > 4 days), gave good predictions of the measured sorption at different time scales and represented a simple alternative to the ID and TRSK models. Calculating the naphthalene retardation factor as a function of time, R(t), using the two-term K′F(t) model implied that sorption non-linearity is highly important when evaluating both short- and longer-term naphthalene mobility in soil and will often overshadow the effects of sorption time-dependency.