Reuse of used hand warmer for preventing nitrate pollution and estimation of relevant solute behavior

本研究旨在探讨废手暖物(HWCs)在两种土壤中的再利用，以延缓和扩散硝酸盐的运移，以避免硝酸盐迅速淋失到高浓度地下水中。通过柱实验，可以观察到不同流量、不同HWCs配比条件下的硝酸盐行为。利用时间矩估计频散系数、延迟因子和分布系数。结果表明，随着HWCs用量的增加，滞留系数增大，在硅砂和安迪松中的滞留系数分别达到3.3和1.7。特别是，HWCs对硅砂中硝酸盐的抑制作用似乎是显著的。因此，HWCs是砂质介质中硝酸盐运移的有效吸附剂，而具有团聚体结构的安第斯土等多孔介质可能会阻碍HWCs的能力。

This study focused on the possible reuse of used hand warmer contents (HWCs) for retarding and spreading nitrate transport in two types of soils to avoid a prompt nitrate leaching to groundwater with a high concentration. The column experiments allowed the observation of the nitrate behavior at various flow rates under the different conditions of mixture ratios of HWCs. Temporal moments were applied to estimate the dispersion coefficient, the retardation factor and the distribution coefficient. Results indicated that the retardation factor increased with the increase in the amount of HWCs and reached up to 3.3 and 1.7 in silica sand and Andisol, respectively. In particular, the effect of HWCs on nitrate retardation in silica sand appeared to be significant. Accordingly, HWCs have a potency to be an effective adsorbent for the nitrate transport in sandy media whereas porous media such as Andisols with an aggregate structure might hinder the ability of HWCs.