Department of Civil & Environmental Engineering, Faculty of Engineering, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
Department of Civil & Environmental Engineering, Faculty of Engineering, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
Sci Total Environ. 2018 Jul 15;630:1258-1268. doi: 10.1016/j.scitotenv.2018.02.306. Epub 2018 Mar 7.
Detection of metformin, an antidiabetic drug and its transformation product guanylurea in various environmental matrices such as surface water and groundwater, coupled with their effects on aquatic organisms warrant an understanding of the compounds fate and behaviour in the environment. Batch studies were conducted with the aim of evaluating the sorption of these two emerging contaminants in six New Zealand agricultural soils of contrasting physico-chemical properties. Kinetic studies revealed that metformin and guanylurea sorption in Te Kowhai soil was very rapid initially achieving 90% sorption within the first 4 and 13h, respectively. Fit of several isotherm models to the measured batch sorption data showed that the hybrid models Langmuir-Freundlich and Redlich-Peterson best described the isotherms. Freundlich isotherm showed higher linearity for guanylurea (n=0.58-0.93) in all soils compared to metformin (n=0.25-0.71). A linear isotherm was fitted at environmentally relevant low concentrations (< 3mg/L) of target compounds and calculated values of sorption distribution coefficient (K) were in the range of 8.97 to 53.49L/kg for metformin and between 10.6 and 37.51L/kg for guanylurea. Sorption of both metformin and guanylurea was dependent on the soil characteristics, however, no generalisation could be made as to which had higher affinity to soils studied. Pearson's correlation and multiple regression analyses indicate that Si/Al (p=0.042) and clay (p=0.015) significantly influenced metformin K values, whereas the soil's cation exchange capacity (p=0.024) is the single most significant factor determining guanylurea sorption in soils. It is likely that the type of minerals present in soils and its ion-exchange capacity could play an important role in metformin and guanylurea sorption, respectively.
检测二甲双胍（一种抗糖尿病药物）及其转化产物胍基脲在地表水和地下水等各种环境基质中的存在情况，以及它们对水生生物的影响，都需要了解这些化合物在环境中的迁移转化行为。本研究开展了批实验，旨在评估这两种新兴污染物在 6 种具有不同理化性质的新西兰农业土壤中的吸附情况。动力学研究表明，在 Te Kowhai 土壤中，二甲双胍和胍基脲的吸附非常迅速，分别在最初的 4h 和 13h 内达到 90%的吸附。几种等温线模型拟合实验批吸附数据的结果表明，混合模型 Langmuir-Freundlich 和 Redlich-Peterson 能够最好地描述等温线。与在所有土壤中 n 值为 0.25-0.71 的二甲双胍相比，在所有土壤中，Freundlich 等温线更适合描述胍基脲（n 值为 0.58-0.93）。在环境相关的低浓度（<3mg/L）下拟合线性等温线，并计算出吸附分配系数（K）的值，二甲双胍的范围为 8.97-53.49L/kg，胍基脲的范围为 10.6-37.51L/kg。二甲双胍和胍基脲的吸附均依赖于土壤特性，但不能对研究中哪种土壤具有更高的吸附亲和力做出一般性结论。皮尔逊相关性和多元回归分析表明，Si/Al（p=0.042）和粘土（p=0.015）显著影响二甲双胍的 K 值，而土壤的阳离子交换容量（p=0.024）是决定土壤中胍基脲吸附的唯一最重要因素。土壤中存在的矿物质类型及其离子交换能力可能分别在二甲双胍和胍基脲的吸附中起重要作用。
