Dept. Biology, Loyola Univ. Chicago, 1032 W Sheridan Rd, Chicago, IL, 60660, USA.
Dept. Biological Sciences, Univ. of Notre Dame, Notre Dame, IN, 46556, USA.
Sci Rep. 2019 Mar 6;9(1):3740. doi: 10.1038/s41598-019-40126-3.
Accumulation of plastic litter is accelerating worldwide. Rivers are a source of microplastic (i.e., particles <5 mm) to oceans, but few measurements of microplastic retention in rivers exist. We adapted spiraling metrics used to measure particulate organic matter transport to quantify microplastic deposition using an outdoor experimental stream. We conducted replicated pulse releases of three common microplastics: polypropylene pellets, polystyrene fragments, and acrylic fibers, repeating measurements using particles with and without biofilms. Depositional velocity (v; mm/s) patterns followed expectations based on density and biofilm 'stickiness', where v was highest for fragments, intermediate for fibers, and lowest for pellets, with biofilm colonization generally increasing v. Comparing microplastic v to values for natural particles (e.g., fine and coarse particulate organic matter) showed that particle diameter was positively related to v and negatively related to the ratio of v to settling velocity (i.e., sinking rate in standing water). Thus, microplastic v in rivers can be quantified with the same methods and follows the same patterns as natural particles. These data are the first measurements of microplastic deposition in rivers, and directly inform models of microplastic transport at the landscape scale, making a key contribution to research on the global ecology of plastic waste.
塑料垃圾在全球范围内的积累正在加速。河流是微塑料（即<5 毫米的颗粒）进入海洋的源头，但目前对河流中微塑料截留的测量方法还很少。我们采用了螺旋式指标来测量颗粒有机物的传输，并用室外实验溪流来量化微塑料的沉积。我们对三种常见的微塑料进行了重复脉冲释放：聚丙烯颗粒、聚苯乙烯碎片和丙烯酸纤维，并对有和没有生物膜的颗粒重复进行了测量。沉积速度（v；毫米/秒）模式符合基于密度和生物膜“粘性”的预期，其中碎片的 v 最高，纤维居中，颗粒最低，生物膜定植通常会增加 v。将微塑料 v 与天然颗粒（例如，细颗粒和粗颗粒有机物）的 v 值进行比较表明，颗粒直径与 v 值呈正相关，与 v 与沉降速度（即静水下沉速度）的比值呈负相关。因此，河流中微塑料 v 可以用相同的方法进行量化，并遵循与天然颗粒相同的模式。这些数据是河流中微塑料沉积的首次测量，直接为景观尺度的微塑料传输模型提供了信息，为研究塑料垃圾的全球生态做出了重要贡献。
