Laboratory Observations of Variable Size and Shape Particles: Artificial Sand and Oil Agglomerates

Following marine oil spills, weathered oil can mix with sediment in the surf zone and settle to the seafloor to form mats up to hundreds of meters long. Wave action fragments these mats into 1 to 10 cm diameter sand and oil agglomerates (SOAs). SOAs can persist for years, becoming buried in or exhumed from the seafloor and/or transported cross-shore and alongshore (Dalyander and others, 2015). These fragments are angular near the source mat and become increasingly rounded as they are transported. To quantify SOA motion, the U.S. Geological Survey (USGS) conducted experiments in November 2016 (field activity number 2016-364-DD) and June 2017 (field activity number 2017-329-FA) using various size, shape, and density artificial sand and oil agglomerates (aSOAs). Video and velocity data were collected under a range of hydrodynamic forcing in the Small-Oscillatory Flow Tunnel at the U.S. Naval Research Laboratory in Stennis, Mississippi. Between November 14-18, 2016, laboratory studies were conducted on spherical and patty shaped particles on a roughened flat bed. Two types of particles were used, one consisting of paraffin wax and sand, another was machine fabricated out of aluminum and coated in sand. Between June 5-8, 2017, laboratory studies were conducted on spherical, patty, ellipsoidal, and angular-ellipsoidal particles using paraffin wax and sand, aluminum, and 3-D printed plastic particles.

海洋溢油发生后，经风化的原油可在激浪带（surf zone）与沉积物混合，沉降至海底形成长达数百米的油聚垫。波浪作用会将这些油聚垫破碎为直径1~10厘米的砂油团聚体（sand and oil agglomerates，SOAs）。砂油团聚体可留存数年，可被埋藏于海底、从海底暴露，或在跨岸与沿岸方向发生搬运（Dalyander等人，2015）。此类团聚体在源油聚垫附近呈棱角状，随搬运过程逐渐变得愈发圆润。为定量表征砂油团聚体的运移过程，美国地质调查局（U.S. Geological Survey，USGS）分别于2016年11月（野外活动编号2016-364-DD）与2017年6月（野外活动编号2017-329-FA）开展实验，使用了不同尺寸、形状与密度的人工砂油团聚体（artificial sand and oil agglomerates，aSOAs）。研究团队在密西西比州斯坦尼斯市的美国海军研究实验室小型振荡流隧道中，于一系列水动力强迫条件下采集了视频与流速数据。2016年11月14日至18日，研究团队在糙化平底床面上开展了球形与饼状颗粒的实验室研究，所用颗粒分为两类：一类为石蜡砂复合颗粒，另一类为机加工铝制颗粒并覆有砂层。2017年6月5日至8日，研究团队针对球形、饼状、椭球形与棱角椭球形颗粒开展了实验室研究，所用颗粒材料包括石蜡砂复合材料、铝制材料以及3D打印塑料颗粒。