Carbazole (CBZ) and acridine (ACR) are polycyclic aromatic nitrogen heterocycles (PANHs) widely found in combined contaminated soils, while investigations on organic-organic interactions have been very limited. In this study, batch experiments were carried out on five soils with different properties, taking CBZ as a representative of PANHs and ACR as a co-existing contaminant. The adsorption isotherms of CBZ (50–1000 μg/L) were nonlinear. Soil organic matter (SOM) and cation exchange capacity (CEC) showed positive correlations with CBZ adsorption-desorption coefficients. The adsorption mechanisms of CBZ involved hydrogen bonding, π-π interaction, and cation-π bonding. Different concentrations of ACR had varying effects on CBZ. The adsorption of CBZ was inhibited with 250 μg/L ACR. The cooperative adsorption was observed on three soils with increasing ACR concentration (1000 μg/L) and led to more pronounced nonlinear isotherms. The S-shaped isotherms of ACR indicated that ACR was adsorbed to the soil surface in a perpendicular configuration. New adsorption sites were created allowing for increased CBZ adsorption through π-π interaction with ACR. Therefore, variations in soil properties and potential impacts of co-existing contaminants should be well considered when assessing the combined pollution of site soil. This will contribute to a more accurate estimation of environmental and health risks.

中文翻译：

---

共存吖啶对土壤中咔唑吸附-解吸行为的影响：共吸附及机理研究

咔唑（CBZ）和吖啶（ACR）是多环芳香族氮杂环（PANH），广泛存在于复合污染土壤中，而对有机-有机相互作用的研究非常有限。本研究以CBZ为PANHs的代表，ACR为共存污染物，对5种不同性质的土壤进行了批量实验。 CBZ (50–1000 μg/L) 的吸附等温线是非线性的。土壤有机质（SOM）和阳离子交换量（CEC）与CBZ吸附-解吸系数呈正相关。 CBZ的吸附机制涉及氢键、π-π相互作用和阳离子-π键。不同浓度的ACR对CBZ有不同的影响。 250 μg/L ACR 抑制 CBZ 的吸附。随着 ACR 浓度（1000 μg/L）的增加，在三种土壤上观察到协同吸附，并导致更明显的非线性等温线。 ACR 的 S 形等温线表明 ACR 以垂直结构吸附到土壤表面。创建了新的吸附位点，通过与 ACR 的 π-π 相互作用增加了 CBZ 的吸附。因此，在评估场地土壤的综合污染时，应充分考虑土壤性质的变化和共存污染物的潜在影响。这将有助于更准确地估计环境和健康风险。