Department of Animal and Plant Sciences, The University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
Sci Total Environ. 2012 Feb 1;416:455-63. doi: 10.1016/j.scitotenv.2011.11.078. Epub 2012 Jan 4.
Synthetic microplastics (≤5-mm fragments) are globally distributed contaminants within coastal sediments that may transport organic pollutants and additives into food webs. Although micro-Fourier-transform infrared (micro-FT-IR) spectroscopy represents an ideal method for detecting microplastics in sediments, this technique lacks a standardized operating protocol. Herein, an optimized method for the micro-FT-IR analysis of microplastics in vacuum-filtered sediment retentates was developed. Reflectance micro-FT-IR analyses of polyethylene (PE) were compared with attenuated total reflectance FT-IR (ATR-FT-IR) measurements. Molecular mapping as a precursor to the imaging of microplastics was explored in the presence and absence of 150-μm PE fragments, added to sediment at concentrations of 10, 100, 500 and 1000ppm. Subsequently, polymer spectra were assessed across plastic-spiked sediments from fifteen offshore sites. While all spectra obtained of evenly shaped plastics were typical to PE, reflectance micro-FT-IR measurements of irregularly shaped materials must account for refractive error. Additionally, we provide the first evidence that mapping successfully detects microplastics without their visual selection for characterization, despite this technique relying on spectra from small and spatially separated locations. Flotation of microplastics from sediments only enabled a fragment recovery rate of 61 (±31 S.D.) %. However, mapping 3-mm(2) areas (within 47-mm filters) detected PE at spiking concentrations of 100ppm and above, displaying 69 (±12 S.D.) % of the fragments in these locations. Additionally, mapping detected a potential PE fragment in a non-spiked retentate. These data have important implications for research into the imaging of microplastics. Specifically, the sensitivity and spatial resolution of the present protocol may be improved by visualizing the entire filter with high-throughput detection techniques (e.g., focal plane array-based imaging). Additionally, since micro-FT-IR analyses depend on methods of sample collection, our results emphasize the urgency of developing efficient and reproducible techniques to separate microplastics from sediments.
合成微塑料（≤5 毫米碎片）是全球分布在沿海沉积物中的污染物，它们可能将有机污染物和添加剂输送到食物网中。尽管微傅里叶变换红外（micro-FT-IR）光谱代表了检测沉积物中微塑料的理想方法，但该技术缺乏标准化的操作协议。本文开发了一种优化的真空过滤沉积物截留物中微塑料的微-FT-IR 分析方法。对聚乙烯（PE）的反射微-FT-IR 分析与衰减全反射 FT-IR（ATR-FT-IR）测量进行了比较。在存在和不存在 150-μm PE 碎片的情况下，探索了分子图谱作为微塑料成像的前体，这些碎片以 10、100、500 和 1000ppm 的浓度添加到沉积物中。随后，评估了来自 15 个近海地点的塑料污染沉积物中的聚合物光谱。虽然对形状均匀的塑料进行的所有光谱测量均为典型的 PE，但必须考虑到不规则形状材料的折射误差进行反射微-FT-IR 测量。此外，我们首次提供的证据表明，尽管该技术依赖于来自小且空间上分离的位置的光谱，但图谱成功地检测到了微塑料，而无需对其进行视觉选择以进行表征。从沉积物中浮选微塑料只能使微塑料的回收率达到 61（±31 S.D.）%。然而，在 100ppm 及以上的浓度下，对 3-mm(2) 区域（在 47-mm 过滤器内）进行图谱探测，可探测到 PE，显示出这些位置 69（±12 S.D.）%的碎片。此外，图谱探测到在未污染的截留物中存在潜在的 PE 碎片。这些数据对微塑料成像研究具有重要意义。具体而言，通过使用高通量检测技术（例如基于焦平面阵列的成像）可视化整个过滤器，可以提高本协议的灵敏度和空间分辨率。此外，由于微-FT-IR 分析取决于样品采集方法，因此我们的结果强调了开发高效且可重复的技术以将微塑料从沉积物中分离出来的紧迫性。
