Laboratoire Interdisciplinaire des Environnements Continentaux, Université de Lorraine (CNRS), 54506, Vandœuvre-lès-Nancy, France.
BRGM (French Geological Survey), 45060, Orléans CEDEX 02, France.
Environ Sci Pollut Res Int. 2018 May;25(15):14324-14335. doi: 10.1007/s11356-017-9123-1. Epub 2017 May 15.
Constructed wetlands (CWs) are used to reduce the pesticide inputs from tile drainage or run-off to surface water. Their effectiveness appears variable and remains to be better characterized and understood. The aim of this study was to assess the influences of two hydraulic parameters (i.e., dynamics and water level) on the sorption process occurring in CWs. Then, two solid/liquid ratios were studied (1/1 and 1/5) to mimic the water level variation in the field, and two agitation speeds were used (none and gentle agitation) to simulate different water dynamics (stagnation and flow pass, respectively). Sorption kinetics and isotherms were obtained for four pesticides with contrasting properties. The pesticide adsorption coefficients were classified as follows: boscalid (BSC) > cyproconazole (CYP) > isoproturon (IPU) ∼ dimethachlor (DMT) at any ratio or agitation, in agreement with their water solubilities and K values. The effect of the solid/liquid ratio was evidenced for all conditions. Indeed, the adsorption equilibrium time was reached more quickly for the 1/1 ratio (24-72 h) than for the 1/5 ratio (96-120 h). In addition, the adsorption coefficients (K ) were larger for the 1/1 ratio (1.8-11.2 L kg) than for the 1/5 ratio (1.0-5.9 L kg). The agitation effect was more evidenced for the 1/5 ratio and for the more hydrophobic molecules, such as BSC and CYP, for which adsorption equilibrium time was never reached with agitation (>120 h), while it was reached at 96 h without agitation. Moreover, the K values were larger with agitation than without agitation for BSC and CYP, whereas they were similar for the two agitations for IPU and DMT. Our results demonstrated that the hydrodynamic function of CWs could influence pesticide sorption with variable effects according to the molecular properties and consequently influence the mitigation effect of CWs throughout the year.
人工湿地（CWs）用于减少从排水渠或径流进入地表水的农药投入。其效果似乎各不相同，仍需更好地描述和理解。本研究的目的是评估两个水力参数（即动态和水位）对 CWs 中发生的吸附过程的影响。然后，研究了两种固液比（1/1 和 1/5）以模拟田间水位变化，并使用两种搅拌速度（无搅拌和温和搅拌）模拟不同的水动力（分别为停滞和流动通过）。获得了具有不同性质的四种农药的吸附动力学和等温线。在任何比例或搅拌条件下，农药吸附系数的分类如下：百菌清（BSC）> 吡虫啉（CYP）> 异丙隆（IPU）≈二甲戊乐灵（DMT），这与它们的水溶性和 K 值一致。固液比的影响在所有条件下都得到了证实。事实上，1/1 比例（24-72 小时）的吸附平衡时间比 1/5 比例（96-120 小时）更快达到。此外，1/1 比例的吸附系数（K）（1.8-11.2 L kg）大于 1/5 比例（1.0-5.9 L kg）。搅拌的影响在 1/5 比例和更疏水的分子（如 BSC 和 CYP）中更为明显，对于这些分子，搅拌条件下的吸附平衡时间从未达到（>120 小时），而无搅拌条件下在 96 小时达到平衡。此外，BSC 和 CYP 的 K 值在搅拌条件下大于无搅拌条件下的值，而对于 IPU 和 DMT 两种搅拌条件下的值相似。我们的结果表明，CWs 的水动力功能可能会影响农药的吸附，其影响根据分子性质而有所不同，从而影响 CWs 全年的缓解效果。
