Sediment source fingerprinting: benchmarking recent outputs, remaining challenges and emerging themes

Abstract

Purpose: This review of sediment source fingerprinting assesses the current state-of-the-art, remaining challenges and emerging themes. It combines inputs from international scientists either with track records in the approach or with expertise relevant to progressing the science.

Methods: Web of Science and Google Scholar were used to review published papers spanning the period 2013-2019, inclusive, to confirm publication trends in quantities of papers by study area country and the types of tracers used. The most recent (2018-2019, inclusive) papers were also benchmarked using a methodological decision-tree published in 2017.

Scope: Areas requiring further research and international consensus on methodological detail are reviewed, and these comprise spatial variability in tracers and corresponding sampling implications for end-members, temporal variability in tracers and sampling implications for end-members and target sediment, tracer conservation and knowledge-based pre-selection, the physico-chemical basis for source discrimination and dissemination of fingerprinting results to stakeholders. Emerging themes are also discussed: novel tracers, concentration-dependence for biomarkers, combining sediment fingerprinting and age-dating, applications to sediment-bound pollutants, incorporation of supportive spatial information to augment discrimination and modelling, aeolian sediment source fingerprinting, integration with process-based models and development of open-access software tools for data processing.

Conclusions: The popularity of sediment source fingerprinting continues on an upward trend globally, but with this growth comes issues surrounding lack of standardisation and procedural diversity. Nonetheless, the last 2 years have also evidenced growing uptake of critical requirements for robust applications and this review is intended to signpost investigators, both old and new, towards these benchmarks and remaining research challenges for, and emerging options for different applications of, the fingerprinting approach.

Keywords: Biomarkers; Fingerprinting approach; Sediment-age dating; Tracers; Weathering indices.

Fig. 1

a Published papers reporting the use of fingerprinting each year between 2013 and 2019, inclusive (trend not statistically significant). b A breakdown of the composite signatures used by papers published during 2013–2017 (n = 131 papers) and 2018–2019 (n = 71 papers)

Fig. 2

The number of fingerprinting papers published between 2013 and 2019, inclusive, using the countries for the study sites

Fig. 3

Benchmarking of recent (2018 and 2019, inclusive) papers for use of critical methodological steps

Fig. 3

Benchmarking of recent (2018 and 2019, inclusive) papers for use of critical methodological steps

Fig. 4

The relative solubility (hydrophobicity) of selected inorganic constituents in natural waters. The lower the solubility, the greater the stability. Stability increases from the lower right to the upper left of the figure (after Meybeck and Helmer 1989)

Fig. 5

Carbon isotopic (δ¹³C) values of FAs (fatty acids) among size fractions in a early summer and b summer suspended particulate matter from the Yellow River, China. LCFA indicates the abundance-weighted average values of the δ¹³C_{26 + 28 + 30} FAs (after Yu et al. 2019)

Fig. 6

Distribution of δ¹³C values (a) and content (b) of representative short-chain (C18) and long-chain (C32) saturated FAs (fatty acids) in potential sediment sources (BLF, broadleaf forest; MF, mixed forest; PF, pine forest; LL, lowland agricultural terraces; UP, upland agriculture terraces; RT, road tracks) and target sediment (Dps) in the Chitlang stream, Nepal (after Upadhayay et al. 2018b)

Fig. 7

General model of sediment transit and residence times (after Gellis et al. 2019)

Fig. 8

Visual comparison of the discrimination of tributary sub-catchment spatial sediment sources using two different composite signatures: left hand plot—weathering indices and geochemical tracers (CIA, WIP, IR, Cu, Fe, Mn, Sr, Zn) and right hand plot—geochemical tracers only (Cu, Fe, Mn, Sr, Zn) (after Nosrati et al. 2019)