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The identification of the sources of sediment is a key part of the management of waterways. This is typically achieved through the well‐established technique known as sediment source fingerprinting that uses tracers and statistical mixing models. Until recently, the approach for solving these mixing models has been dominated by frequentist methods. This review focuses on the growing interest in Bayesian methods for sediment fingerprinting and presents them as an alternative or complementary addition to the frequentist methods. Bayesian methods emphasize flexibility, for example, in the choice of probability distributions for tracers, inclusion of parameter probability terms, the choice of how to characterize tracer proportion, and the choice of fully or empirical Bayesian techniques. The Bayesian approach flexibly combines previous known and current information, to produce results that aim to accurately reflect the real‐world environment. Under the Bayesian paradigm, all model parameters are treated as random variables, and this allows all sources of variation to be explicitly communicated and modelled. Although there are considerable advantages to using a Bayesian approach for sediment tracing, there are some possible problems the practitioner should be aware of. These include computational issues and potential difficulties in choosing probability distributions to realistically represent model parameters. Though there are choices as to what Bayesian approach to implement (i.e., fully or empirical Bayesian), a fully Bayesian approach has been found to best retain fidelity to the Bayesian paradigm of treating all parameters as random variables. It has been recognized that the field of sediment source fingerprinting would greatly benefit from the development of a model that incorporates the tracer selection process into the modelling framework allowing for an all‐in‐one approach, and the flexibility of a Bayesian approach makes this development possible. [ABSTRACT FROM AUTHOR]

A decline in the ecosystem health of Australia's Moreton Bay, a Ramsar wetland of international significance, has been attributed to sediments and nutrients derived from catchment sources. To address this decline the regional management plan has set the target of reducing the loads by 50%. Reforestation of the channel network has been proposed as the means to achieve this reduction, but the extent of revegetation required is uncertain. Here we test the hypothesis that sediment and nutrient loads from catchments decrease proportionally with the increasing proportion of the stream length draining remnant vegetation. As part of a routine regional water quality monitoring program sediment and nutrient loads were measured in 186 flow events across 22 sub-catchments with different proportions of remnant woodland. Using multiple linear regression analysis we develop a predictive model for pollutant loads. Of the attributes examined a combination of runoff and the proportion of the stream length draining remnant vegetation was the best predictor. The sediment yield per unit area from a catchment containing no remnant vegetation is predicted to be between 50 and 200 times that of a fully vegetated channel network; total phosphorus between 25 and 60 times; total nitrogen between 1.6 and 4.1 times. There are ~48 000 km of streams in the region of which 32% drain areas of remnant vegetation. Of these 17 095 km are above the region's water storage dams. We estimate that decreasing the sediment and phosphorus loads to Moreton Bay by 50% would involve rehabilitating ~6350 km of the channel network below the dams; halving the total nitrogen load would require almost complete restoration of the channel network. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Increased sediment loads from accelerated catchment erosion significantly degrade waterways worldwide. In the South East Queensland region of Australia, sediment loads are degrading Moreton Bay, a Ramsar listed wetland of international significance. In this region, like most parts of coastal Australia, sediment is predominantly derived from gully and channel bank erosion processes. A novel approach is presented that uses carbon and nitrogen stable isotope ratios and elemental composition to discriminate between these often indistinguishable subsoil sediment sources. The conservativeness of these sediment properties is first tested by examining the effect of particle size separation (testing for consistency during transport) and the effect of sampling at different times (testing for temporal source consistency). The discrimination potential of these sediment properties is then assessed with the conservative properties, based on the particle size and temporal analyses, modelled to determine sediment provenance in three catchments. Nitrogen sediment properties were found to have significant particle size enrichment and high temporal variance indicative of non-conservative behaviour. Conversely, carbon stable isotopes had very limited particle size and temporal variability highlighting their suitability for sediment tracing. Channel erosion was modelled to be a significant source of sediment ( μ 51%, σ 9%) contrasting desktop modelling research that estimated gully erosion is the predominant sediment source. To limit the supply of sediment to Moreton Bay, channel bank and gully erosion must both be targeted by sediment management programs. By distinguishing between subsoil sediment sources, this approach has the potential to enhance the management of sediment loads degrading waterways worldwide. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The identification of sediment sources is fundamental to the management of increasingly scarce water resources. Tracing the origin of sediment with elemental geochemistry is a well-established approach to determining sediment provenance. Fundamental to the confident apportionment of sediment to their lithogenic sources is the modelling process. Recent approaches have incorporated distributions throughout the modelling process including source contribution terms for two end-member sources. The shift from modelling source samples to modelling samples drawn from distributions has removed relationships, including potential correlations between elemental concentrations, from the modelling process. Here, we present a novel modelling approach that re-incorporates correlations between elemental concentrations and models distributions for source contribution terms for multiple source end members. Artificial mixtures, based on catchment sources samples, were created to test the accuracy of this correlated distribution model and also examine modelling approaches used in the literature. The most accurate model incorporates correlations between elements, uses the absolute mixing model difference and does not use any weighting. This model was then applied to identify the sources of sediment in three South East Queensland catchments and demonstrated that Quaternary Alluvium is the most dominant source of sediment in these catchments ( μ 44%, σ 12%). This study demonstrates that it is important to understand how different weightings may impact modelling results. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including use of radionuclides for quantification of soil and rate of redistribution in catchments, sediment source tracing and sediment source fingerprinting techniques in Kharaa River, Mongolia.

Phosphorus (P) is often a key limiting nutrient in freshwater systems, and excessive P can result in algal blooms, with flow-on effects to aquatic food webs. P sorption is an important process in aquatic and terrestrial ecosystems whereby phosphate (PO) is exchanged between liquid and solid phases. This study shows that differences in the concentration of PO in a subtropical river system during high and low flow can be attributed to differences in P sorption characterises of its catchment soils and sediments. The sediments have lower Equilibrium Phosphate Concentrations (EPC) and higher binding energy (K); the surface soils have higher EPC and higher easily desorbed P (NHCl-P). A comparison of filterable reactive phosphorus (frP) in water samples collected at high and low flows, with soil and sediment EPC, suggested that during event flows, the high EPC and NHCl-P of surface soils is producing a net movement of PO from the soil/sediment system into runoff and stream flow. At baseflow, there is more likely a net movement of PO into the riverbed sediments. This has important implications for management actions aimed at reducing P loads to river systems and downstream water storages, namely the need to increase the infiltration of rainfall to decrease the amount of PO being flushed from the surface soil. [ABSTRACT FROM AUTHOR]

This study describes the use of linearly modulated optically stimulated luminescence (LM-OSL) to distinguish surface-soil derived sediments from those derived from channel bank erosion. LM-OSL signals from quartz extracted from 15 surface-soil and five channel bank samples were analysed and compared to signals from samples collected from two downstream river sites. Discriminant analysis showed that the detrapping probabilities of fast, first slow and second slow components of the LM-OSL signal can be used to differentiate between the samples collected from the channel bank and surface-soil sources. We show that for each of these source end members these components are all normally distributed. These distributions are then used to estimate the relative contribution of surface-soil derived and channel bank derived sediment to the river bed sediments. The results indicate that channel bank derived sediments dominate the sediment sources at both sites, with 90.1 ± 3% and 91.9 ± 1.9% contributions. These results are in agreement with a previous study which used measurements of 137Cs and 210Pbex fallout radionuclides to estimate the relative contribution from these two sources. This result shows that LM-OSL may be a useful method, at least in the studied catchment, to estimate the relative contribution of surface soil and channel erosion to river sediments. However, further research in different settings is required to test the difference of OSL signals in distinguishing these sediment sources. And if generally acceptable, this technique may provide an alternative to the use of fallout radionuclides for source tracing. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]