Soil compaction induced by frequent field traffic often causes surface waterlogging in wheel rut areas during the rainy season. In arsenic (As)-contaminated farmlands, this process creates varying redox conditions that affect As mobility and transformation at different depths. This study examined the effects of compaction on As behavior in a clay loam Alfisol (from A horizon) under periodic waterlogging over 66 days. Four soil columns were packed with two bulk densities of 1.3 g cm⁻³ and 1.65 g cm⁻³ to simulate different compaction treatments across a 0–40 cm profile: no compaction(CK), low compaction(LC), medium compaction (MC), and heavy compaction (HC) with corresponding compacted thickness of 0 cm, 16 cm, 24 cm, and 32 cm. Results showed that compaction significantly decreased soil air permeability (Ka) and redox potential (Eh). During waterlogging, excess water stagnated in compacted layers, creating reducing conditions that promoted the release of the mobile As (III) species into pore water. In the first two waterlogging cycles, As(III) concentrations in pore water peaked at 5.6, 6.2, 7.3, and 8.0 μg L⁻¹ under CK, LC, MC, and HC, respectively, while the average Fe-(hydr)oxide-bound As decreased by 22.9 %, 22.9 %, 23.7 %, and 26.5 %, respectively. During the subsequent waterlogging cycles, with the increase of Ka, Eh, and microbial activity of aerobic species the As was stabilized on soil particles in the fractions of specifically bound As and Fe-(hydr)oxide-bound As with reduced mobility. These findings highlight the potential risks of soil compaction-induced As transformations, particularly the conversion of less mobile As(V) to the more toxic and mobile As(III), posing environmental and health concerns.

中文翻译：

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土壤压实会影响砷的流动性和转化行为吗 - Alfisol 的案例研究

频繁的田间交通引起的土壤压实通常会导致雨季车轮车辙地区的地表积水。在受砷 （As） 污染的农田中，这个过程会产生不同的氧化还原条件，从而影响不同深度的 As 迁移和转化。本研究考察了压实对 Alfisol 粘壤土 Alfisol（来自 A 层）在 66 天内周期性淹水中行为的影响。四根土柱填充了 1.3 g cm⁻³ 和 1.65 g cm⁻³ 两种堆积密度，以模拟 0-40 cm 剖面上的不同压实处理：无压实 （CK）、低压实 （LC）、中压实 （MC） 和重压实 （HC），相应的压实厚度为 0 cm、16 cm、24 cm 和 32 cm。结果表明，压实显著降低了土壤透气性 （Ka） 和氧化还原电位 （Eh）。在内涝过程中，多余的水停滞在压实层中，创造了还原条件，促进了移动的 As （III） 物质释放到孔隙水中。在前两个淹水周期中，孔隙水中 As（III） 浓度在 CK、LC、MC 和 HC 下分别达到 5.6、6.2、7.3 和 8.0 μg L⁻¹ 的峰值，而 Fe-（氢）氧化物结合砷的平均浓度分别下降了 22.9 %、22.9 %、23.7 % 和 26.5 %。在随后的淹水循环中，随着 Ka、Eh 和好氧物种微生物活性的增加，As 在土壤颗粒上以特异性结合的 As 和 Fe-（氢）氧化物结合的 As 的组分稳定，迁移率降低。这些发现强调了土壤压实诱导的 As 转化的潜在风险，特别是将流动性较低的 As（V） 转化为毒性更大且流动性更强的 As（III），从而带来环境和健康问题。