Qi Shengqi, Song Jianhao, Shentu Jiali, Chen Qian, Lin Kexin
Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, Zhejiang Provincial Engineering Research Center of Nonferrous Metal Waste Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, 310012, China; Instrumental Analysis Center of Zhejiang Gongshang University, Hangzhou, 310012, PR China.
Zhejiang Provincial Key Laboratory of Solid Waste Treatment and Recycling, Zhejiang Provincial Engineering Research Center of Nonferrous Metal Waste Recycling, School of Environmental Science and Engineering, Zhejiang Gongshang University, Hangzhou, 310012, China.
Chemosphere. 2022 Oct;305:135322. doi: 10.1016/j.chemosphere.2022.135322. Epub 2022 Jun 13.
Groundwater contamination by microplastics (MPs) has been gradually regarded as a potential human health risk, which calls for detailed investigation of MPs transport behavior in saturated zone. In this study, a series of sand column experiments were carried out to investigate the transport characteristics of large MPs with its diameter of 10-20 μm in porous media, in which the effects of different hydrological conditions and MPs characteristics were examined. Experimental results showed that the increase of water flow rate from 2.2 to 7.5 mL/min significantly increased the maximal outlet MPs concentration by two orders of magnitude, while a larger ratio of MPs diameter to soil particle diameter decreased its mobility. The increase of water salinity from 0 to 25 mmol/L (NaCl) decreased the maximal outlet MPs concentration by 50.5-68.4% for different sized MPs. Since chemical aging would lead to the formation of oxygen-containing functional groups and make MPs more negatively charged, it greatly increased the maximal outlet MPs concentration by 0.53-5.67 times. Compared with the traditional attachment model (AM), the attachment-detachment model (ADM) could better simulate the gradual desorption of large MPs from soil in the process of clean water flushing, indicating the nonnegligible detachment of large MPs from soil. In ADM, the desorption coefficient gradually decreased in the process of clean water flushing, which was only 31.6% of the initial value after flushing kept for 10 PV. Moreover, the equations to calculate the adsorption and desorption coefficients of MPs in the saturated zone were developed, which considered both MPs and aquifer characteristics. Results from this study described the desorption of large MPs in porous media under various conditions, which expands our knowledge about the fate and risk of MPs in underground environment.
微塑料（MPs）对地下水的污染已逐渐被视为一种潜在的人类健康风险，这就需要对MPs在饱和带中的运移行为进行详细研究。在本研究中，进行了一系列砂柱实验，以研究直径为10 - 20μm的大型MPs在多孔介质中的运移特性，考察了不同水文条件和MPs特性的影响。实验结果表明，水流速度从2.2 mL/min增加到7.5 mL/min，显著提高了最大出口MPs浓度两个数量级，而MPs直径与土壤颗粒直径的比值越大，其迁移性越低。水盐度从0增加到25 mmol/L（NaCl），不同粒径的MPs最大出口浓度降低了50.5 - 68.4%。由于化学老化会导致含氧官能团的形成，使MPs带更多负电荷，极大地提高了最大出口MPs浓度0.53 - 5.67倍。与传统的吸附模型（AM）相比，吸附 - 解吸模型（ADM）能更好地模拟在清水冲洗过程中大型MPs从土壤中的逐渐解吸，表明大型MPs从土壤中的解吸不可忽视。在ADM中，解吸系数在清水冲洗过程中逐渐降低，冲洗10孔隙体积（PV）后仅为初始值的31.6%。此外，还建立了计算饱和带中MPs吸附和解吸系数的方程，该方程同时考虑了MPs和含水层的特性。本研究结果描述了各种条件下多孔介质中大型MPs的解吸情况，扩展了我们对地下环境中MPs归宿和风险的认识。
