Assessing issues associated with a time‐integrated fluvial fine sediment sampler

Abstract

Collecting a representative time‐integrated sample of fluvial fine‐grained suspended sediment (<63 μm) is an important requirement for the understanding of environmental, geomorphological, and hydrological processes operating within watersheds. This study (a) characterized the hydrodynamic behaviour of a commonly used time‐integrated fine sediment sampler (TIFSS) using an acoustic Doppler velocimeter (ADV) in controlled laboratory conditions and (b) measured the mass collection efficiency (MCE) of the sampler by an acoustic Doppler current profiler under field conditions. The laboratory results indicated that the hydrodynamic evaluations associated with the original development of the TIFSS involved an underestimation of the inlet flow velocity of the sampler that results in a significant overestimation of the theoretical MCE. The ADV data illustrated that the ratio of the inlet flow velocity of the sampler to the ambient velocity was 87% and consequently, it can be assumed that a representative sample of the ambient fine suspended particles entered into the sampler. The field results showed that the particle size distribution of the sediment collected by the TIFSS was statistically similar to that for the ambient sediment in the Red River, Manitoba, Canada. The MCE of the TIFSS in the field trials appeared to be as low as 10%. Collecting a representative sample in the field was consistent with the previous findings that the TIFSS is a suitable sampler for the collection of a representative sample of sufficient mass (e.g., >1 g) for the investigation of the properties of fluvial fine‐grained suspended sediment. Hydrodynamic evaluation of the TIFSS under a wider range of hydraulic conditions is suggested to assess the performance of the sampler during high run‐off events.

Comparison of sediment biomarker signatures generated using time-integrated and discrete suspended sediment samples

“…This is one reason why TIMS have been adopted so widely for sediment source fingerprinting purposes (Collins and Walling 2004 ). One potential issue identified for the TIMS sampler, however, concerns the underrepresentation of the finest particles in the time-integrated sediment sample (Foets et al 2020 , Smith and Owens 2014 ), although, findings are contradictory in the sense that some researchers have reported similar particle size distributions in TIMS sediment samples compared with other samples (Goharrokhi et al 2019 ).…”

Sediment sources and transport dynamics in large, regulated river systems with multiple lakes and reservoirs in the subarctic region of Canada

“…The Red River suspended sediment samples were collected using a time-integrated suspended sediment sampler between May and November 2016. The sampler was designed by Phillips et al (2000) and evaluated for this watershed by Goharrokhi et al (2019). The MV Namao research vessel was used to access and collect the north shore materials from the middle height of the shore line using a small, stainless steel trowel.…”