Effect of dry-wet cycles on leaching behavior of recovered soil collected from tsunami deposits containing geogenic arsenic
Effect of dry-wet cycles on leaching behavior of recovered soil collected from tsunami deposits containing geogenic arsenic
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DOI：
10.1016/j.sandf.2022.101271
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发表时间：
2023-02
影响因子：
3.7
通讯作者：
Jiajie Tang;H. Sakanakura;A. Takai;T. Katsumi
中科院分区：
文献类型：
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作者：
Jiajie Tang;H. Sakanakura;A. Takai;T. Katsumi
地质污染物，如砷，经常在沿海地区回收的土壤中发现。当土壤用作路基材料时，这些污染物可能会浸出。此外，这类污染物的浸出可能受到环境变化的影响，例如干湿循环，在某些情况下，由于浸出量较大，预计会造成更高的环境风险。因此，在本研究中，从海啸沉积物中恢复的土壤在三种不同的干燥条件下进行干湿循环，以研究环境变化如何影响淋滤行为。为了评价土壤表面的物理和化学变化，进行了显微/光谱研究。批量浸出试验表明，干湿循环对大多数元素（如Fe、Si、Na、Ca等）的浸出行为略有改变。砷浸出在某些干湿循环中增加，然后减少，显微镜/光谱证实这种增加可能是由于黄铁矿氧化。这些干湿循环可以分解黄铁矿的形态，引起黄铁矿氧化，导致更酸性的浸出条件，加速砷的浸出。经过一定的氧化过程后，生成的氢氧化铁可以防止黄铁矿表面进一步氧化。铁氧化物和氢氧化物也可作为砷的吸附剂，防止砷浓度的增加。
Geogenic contaminants, such as arsenic, are often found in soil recovered from coastal areas. These contaminants may leach out when the soil is used as embankment material. Moreover, the leaching of such contaminants might be influenced by environmental changes, such as dry-wet cycles, and higher environmental risks due to a larger amount of leaching are anticipated in some cases. In this study, therefore, soil recovered from tsunami deposits was subjected to dry-wet cycles under three different drying conditions to investigate how environmental changes affect the leaching behavior. To evaluate the physical and chemical changes in the soil surface, microscopic/spectroscopic studies were conducted. Batch leaching tests revealed that dry-wet cycles slightly alter the leaching behavior of most elements, such as Fe, Si, Na, Ca, etc. Arsenic leaching was seen to increase in certain dry-wet cycles before decreasing, and microscopic/spectroscopic confirmed that this increase was likely due to pyrite oxidation. These dry-wet cycles can disintegrate pyrite morphology and cause pyrite oxidation, leading to a more acidic leaching condition that accelerates arsenic leaching. After a certain oxidation procedure, the resulting ferric hydroxide may prevent the pyrite surfaces from further oxidation. The Fe oxides and hydroxides can also act as arsenic adsorbents, preventing the increase in arsenic concentration.