Purpose

Sorption of organic compounds to soil largely determines their mobility and bioavailability in ecosystems. It is well known that molecular properties of the organic sorbates affect the sorbed amounts and sorption kinetics. But also changes in the hydration status of soils alter the physicochemical and sorptive properties of soil organic matter (SOM), which is the main sorbent for organic compounds in soils. This study elucidates the effects of varying SOM prehydration status on sorption of PAHs and PAH derivatives in peat soil.

Materials and methods

For sorption experiments, topsoil samples of a peat soil with 51% SOM were adjusted to water contents of 15, 30, and 50% (w/w based on dry soil mass) and conditioned for different water contact times of up to 2 years at one constant water content. Sorption kinetics and isotherms of naphthalene, three naphthalene derivatives, phenanthrene, and pyrene to these samples were investigated in batch experiments. Effects of the sorbates’ properties and SOM hydration on sorption were analyzed.

Results and discussion

Sorption to the peat soil was nonlinear and varied among sorbates and differently prehydrated soil samples. Sorbate polarizability, molecular volume, and weight increased the sorbed amount. Sorption kinetics were two-phased with a fast and a slow sorbing fraction. Hydroxyl groups in sorbates acting as H-donor or acceptor led to an increase of the slow sorbing fraction. Increasing total water contents, amounts of non-freezable water in SOM, increasing pore sizes, and decreasing hydrophobicity of SOM decreased the total sorbed amount and the fast sorbing fraction while increasing the slow sorbing fraction. The latter effects increased with increasing polarity and dipole moment of the sorbate. The SOM matrix rigidity varied with prehydration status; higher SOM matrix rigidity led to non-ideal sorption processes, namely, higher sorption nonlinearity and slower sorption.

Conclusions

The study revealed the effects and interplay of SOM prehydration status and molecular properties of the sorbates on sorption of PAHs and PAH derivatives. As sorbed amounts may decrease and become non-ideal upon aging at the presence of water, estimations of the mobility of organic compounds in the environment need to consider SOM prehydration status in high organic soils.

中文翻译：

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泥炭土壤中PAHs和PAH衍生物的吸附受预水化状态的影响：SOM和山梨酸酯性质的作用

目的

有机化合物对土壤的吸附在很大程度上决定了它们在生态系统中的流动性和生物利用度。众所周知，有机山梨酸酯的分子性质影响吸附量和吸附动力学。但是，土壤水化状态的变化也会改变土壤有机物（SOM）的理化和吸附特性，而有机物是土壤中有机化合物的主要吸附剂。这项研究阐明了泥炭土壤中不同的SOM预水化状态对PAHs和PAH衍生物吸附的影响。

材料和方法

对于吸附实验，将SOM为51％的泥炭土的表土样品的水分含量调整为15、30和50％（w / w，基于干土质量），并在不同的水接触时间下进行长达2年的调理。一种恒定的水含量。在批处理实验中研究了萘，三种萘衍生物，菲和pyr对这些样品的吸附动力学和等温线。分析了吸附物的性质和SOM水合对吸附的影响。

结果和讨论

对泥炭土壤的吸附是非线性的，并且在山梨酸盐和不同的预水合土壤样品之间变化。吸收极化率，分子体积和重量增加了吸附量。吸附动力学分为快速吸附和缓慢吸附两阶段。充当H供体或受体的山梨酸酯中的羟基导致缓慢吸附分数的增加。总水含量的增加，SOM中不可冻结水的量，孔径的增加以及SOM疏水性的降低，降低了总吸附量和快速吸附率，同时增加了缓慢吸附率。后者的影响随着被吸附物极性和偶极矩的增加而增加。SOM基质刚度随预水状态而变化；较高的SOM基体刚性导致非理想的吸附过程，即

结论

这项研究揭示了SOM预水化状态和山梨酸酯分子特性对PAHs和PAH衍生物吸附的影响和相互作用。由于在水中存在时，吸附量可能会减少并变得不理想，因此对有机化合物在环境中的迁移率的估算需要考虑高有机土壤中SOM的预水合状态。