Marzi Mostafa, Towfighi Hasan, Shahbazi Karim, Farahbakhsh Mohsen, Rinklebe Jörg, Lima Eder C
Soil Science Department, University of Tehran, Tehran, Iran.
Soil and Water Research Institute, Agricultural Research Education and Extension Organization, Tehran, Iran.
Environ Sci Pollut Res Int. 2023 Jan;30(1):1318-1332. doi: 10.1007/s11356-022-22310-7. Epub 2022 Aug 1.
Irrigation of carbonate-rich agricultural soils with arsenic (As)-contaminated water leads to the accumulation of As in these soils. In this regard, there is an opportunity to adsorb and fix the As in soil and decrease the As transportation to the plants and subsequently the human food chain. So, the present study aimed to investigate the adsorption-desorption characteristics of As in calcareous soils and the potential of As fixation over time. First, to achieve this purpose, 53 soil samples were gathered from the study site and after the laboratory analysis, the soils were categorized into four groups based on their physicochemical properties. Then, four representative samples of these groups were selected, namely soil 1, soil 2, soil 3, and soil 4. Afterward, the As adsorption-desorption was investigated in a lab-scale batch experiment. Next, the effect of age was assessed by incubating the As-adsorbed soils for 60 days, and to study the impact of temperature, the adsorption was performed at four temperature levels (10, 20, 30, and 40 °C). Finally, the isotherm models were fitted to experimental data, and the amount of loosely and tightly held As was quantified. Results revealed that the As adsorption isotherms were L-type, in which As adsorption increased with the increase of As loading. The double-site Langmuir (DSL) estimated that a limited amount of As was adsorbed on high-energy surfaces and a large amount of As was adsorbed on low-energy surfaces. Desorption results showed that a significant amount of As desorbed immediately; however, the desorption significantly decreased with the increase of age, especially at low equilibrium concentrations. By aging the loosely held As transformed into non-labile forms so that in soils 1, 2, 3, and 4, the fraction of As adsorbed on high-energy surfaces increased from 72.5, 93.2, 63.2, and 123 mg/kg to 167, 141, 70.6, and 196 mg/kg, respectively, and the fraction of As adsorbed on low-energy surfaces decreased from 397, 256, 202, and 317 mg/kg to 182, 238, 173, and 172 mg/kg, respectively (after aging for 60 days). Aging proved to be a promising solution for decreasing As transport into the human food chain and could be employed for crops with longer irrigation cycles. ΔH values were positive and varied from 9.26 to 13.0 kJ/mol, confirming the endothermic nature of adsorption. ΔG values were negative and varied from - 18.8 to - 22.8 kJ/mol at all temperatures, demonstrating the spontaneous nature of adsorption.
用受砷（As）污染的水灌溉富含碳酸盐的农业土壤会导致这些土壤中砷的积累。在这方面，存在吸附和固定土壤中砷并减少砷向植物以及随后人类食物链转移的机会。因此，本研究旨在调查石灰性土壤中砷的吸附 - 解吸特性以及砷随时间固定的潜力。首先，为实现这一目的，从研究地点采集了53个土壤样本，经过实验室分析后，根据其理化性质将土壤分为四组。然后，从这些组中选取了四个代表性样本，即土壤1、土壤2、土壤3和土壤4。之后，在实验室规模的批量实验中研究了砷的吸附 - 解吸。接下来，通过将吸附砷的土壤孵育60天来评估时间的影响，并且为了研究温度的影响，在四个温度水平（10、20、30和40℃）下进行吸附。最后，将等温线模型拟合到实验数据，并对松散和紧密吸附的砷量进行了量化。结果表明，砷吸附等温线为L型，其中砷吸附量随砷负载量的增加而增加。双位点朗缪尔（DSL）模型估计，有限量的砷吸附在高能表面上，大量的砷吸附在低能表面上。解吸结果表明，大量的砷立即解吸；然而，解吸量随着时间的增加而显著降低，特别是在低平衡浓度下。通过老化，松散吸附的砷转化为非活性形式，因此在土壤1、2、3和4中，吸附在高能表面上的砷分数分别从72.5、93.2、63.2和123mg/kg增加到167、141、70.6和196mg/kg，吸附在低能表面上的砷分数分别从397、256、202和317mg/kg降低到182、238、173和172mg/kg（老化60天后）。老化被证明是减少砷向人类食物链转移的一种有前景的解决方案，可用于灌溉周期较长的作物。ΔH值为正，范围从9.26到13.0kJ/mol，证实了吸附的吸热性质。ΔG值为负，在所有温度下范围从 - 18.8到 - 22.8kJ/mol，表明吸附是自发的。
