INSSECT—an instrumented platform for investigating floc properties close to the seabed

Abstract

A new type of tripod, INSSECT (IN situ Size and SEttling Column Tripod), designed for floc measurements in the shallow parts of the continental shelf, is described. INSSECT orientates itself into the current so that instrumentation on it faces upstream, thereby minimizing flow disturbance. The instrumentation includes a digital floc camera, a video settling column, a unique sediment trap designed for capturing flocs intact, a laser sizer, an optical backscatterance sensor, a compass and tilt meter, and a current meter. It is designed for relatively short deployments of up to 2 weeks and can be recovered, turned around, and redeployed rapidly. It was designed for use in semi-synoptic surveys of the spatial variation in floc properties such as size and settling velocity and the factors that influence them. The paper describes the various components of the INSSECT and presents selected results from the first deployments, demonstrating its ability to turn in the current and capture single flocs intact. Contrary to recent findings on the influence on settling columns on floc size, intercomparison between the video settling column and the digital floc camera reveals that the sizes are similar.

The influence of schlieren on in situ optical measurements used for particle characterization

“…Styles (2006) reported only on the impact of density differences on a LISST-100. However, other types of beam transmissometers as well as (digital) floc cameras are frequently used in optical studies and in studies concerned with sediment dynamics (Bartz et al 1978;Milligan 1996;Mikkelsen et al 2004). This paper sets out to elaborate on the pioneering work of Styles (2006) by investigating the impact of density gradients on the results obtained by a digital floc camera (DFC), a LISST-100C, and a SeaTech beam transmissometer in two different water bodies: a highly stratified estuary with buoyancy frequencies around 0.20 s -1 and a less stratified shelf sea with buoyancy frequencies around 0.02 s -1…”

Floc Property of Yeongsan Cohesive Bed Sediment with Respect to Salinity and Sediment Concentration

“…그렇지만, 1회 관측에 많은 시간이 소요될 뿐 만 아니라, 현장에서 채취한 시료를 사용할 경우 플럭 입경이나 침 강속도와 같은 변수를 실험실에서 같은 조건으로 재현하기 어렵다. 이 후에 오웬침강관을 개선한 Sedimentation Velocity(SEDVEL)이 개발되었다 (Mantovanelli and Ridd, 2006; Mikkelsen et al, 2004;2005), Particle Imaging Camera System(PICS, Smith and Friedrichs, 2011). 플럭카메라 시스템은 해상도에 의해 관측 가능 한 최소 플럭의 크기가 제한되는 단점이 있지만 (Hill et al, 2001), LISST와 함께 사용함으로써 단점을 보완할 수 있다 (Mikkelsen et al, 2006).…”

Seasonal variability of total suspended matter in Minas Basin, Bay of Fundy

“…Enhanced flocculation in the summer also could account for the decrease in suspended sediment concentration in that season. Flocculation increases the settling velocity of the fine-grained particles by several orders of magnitude (Hill et al, 2000;Mikkelsen et al, 2004), which would lower TSM concentration in the water column in summer.…”