Abstract Predicting the kinetics of heavy metal release from the field-contaminated soils requires the consideration of the chemical and physical heterogeneity of soil composition, such as multiple soil adsorbents, heterogeneous binding sites, and varying soil particle sizes. In this study, we conducted kinetic experiments to investigate kinetics of copper (Cu) release from different size fractions of two field-contaminated soils. The morphology and elemental distribution of different size fractions of soil particles were measured with scanning electron microscopy (SEM) and spherical aberration corrected scanning transmission electron microscopy (Cs-STEM). A kinetics model considering both variations of soil adsorbents and particle sizes was developed. Overall, different size fractions of soil particles showed highly heterogeneous physical and chemical properties. The reactive soil adsorbents (e.g., soil organic matter (SOM)) and Cu concentrations increased with the decrease of the particle size, and the rate of Cu release from soil particles also increased with the decrease of the particle size. The kinetics model described the experimental kinetics data from different size fractions of soil particles reasonably well. More significantly, the model was able to predict Cu release from the bulk soil samples based on Cu kinetic reactions with different size fractions of soil particles. SOM appeared to be the most dominant adsorbent for Cu under our experimental conditions, and, among different SOM binding sites, bidentate sites involving carboxylic and phenolic functional groups were the most significant. Our results suggested that a unified modeling framework, which specifically considers the chemical heterogeneity of soil binding sites and variations of particle sizes, is promising for predicting kinetic reactions of metals with heterogeneous soil particles in the field.

中文翻译：

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土壤粒径对田间污染土壤中铜释放动力学的影响：实验和定量模型

摘要 预测受污染土壤重金属释放的动力学需要考虑土壤成分的化学和物理异质性，例如多种土壤吸附剂、异质结合位点和不同的土壤粒径。在这项研究中，我们进行了动力学实验，以研究铜 (Cu) 从两种受污染土壤的不同尺寸部分释放的动力学。用扫描电子显微镜（SEM）和球差校正扫描透射电子显微镜（Cs-STEM）测量土壤颗粒不同尺寸部分的形态和元素分布。开发了一种同时考虑土壤吸附剂和粒径变化的动力学模型。全面的，不同大小的土壤颗粒表现出高度异质的物理和化学性质。活性土壤吸附剂（如土壤有机质（SOM））和Cu浓度随着粒径的减小而增加，并且随着粒径的减小，Cu从土壤颗粒中释放的速率也增加。动力学模型很好地描述了土壤颗粒不同尺寸部分的实验动力学数据。更重要的是，该模型能够基于与土壤颗粒的不同尺寸分数的 Cu 动力学反应来预测大量土壤样品中的 Cu 释放。在我们的实验条件下，SOM 似乎是 Cu 的最主要吸附剂，并且在不同的 SOM 结合位点中，涉及羧基和酚官能团的双齿位点是最重要的。