Ellen L. Petticrew

Evaluation of iron-phosphate as a source of internal lake phosphorus loadings

Biological, physical and chemical characteristics of the water column of a shallow (Zmax = 9.2 m), small (surface area 3.8 km2) residential and recreational lake near Prince George, British Columbia, indicated that the system was being loaded internally with phosphorus (P) from the sediments. The abundance of P released from the fine glaciolacustrine, and organic rich sediments was resulting in excess algal and weed growth. It was postulated that iron-phosphate reduction at redox potentials below approximately 200 mV and/or bacterially mediated orthophosphate (PO4-P) releases could be occurring. The development of an appropriate nutrient management strategy required that the process associated with the sediment P release be determined. The MINTEQA2 geochemical model was used to predict the release of orthophosphate (PO4-P) into the interstitial water with the assumption that P is present alternately as strengite, variscite and hydroxyapatite. The predicted release of PO4-P from these P containing minerals was compared to the concentration of PO4-P and total phosphorus (TP) in the overlying hypolimnion. In order to improve the accuracy of the model prediction, the proportion of the sediment present as iron-bound phosphate was estimated. A significant correlation between the observed hypolimnetic TP and interstitial PO4-P concentrations as predicted from iron-bound P dissolution (r2 = 0.59) was found. Total phosphorus release rates to the hypolimnion were also found to be strongly correlated to the iron-bound P component of the sediment (r2 = 0.88). Multivariate regression analyses showed significant relationships between hypolimnetic PO4-P and sediment iron-bound P, Eh, and interstitial Fe (r2 = 0.76). These results provided sufficient evidence to conclude that PO4-P in the system is predominantly bound to Fe-containing minerals and therefore could be managed using treatment techniques that address iron-bound phosphates.

The use of fine sediment fractal dimensions and colour to determine sediment sources in a small watershed

As many particle-associated contaminants and nutrients are supply controlled, the question of particle source is crucial. In addition, sediment storage has important implications for the delivery and fate of pollutants. Increased accumulations of fine sediment (<63 μm) in gravel beds not only modify benthic habitat but also increase the retention time of sediment-associated contaminants in these biologically active areas of river systems. It is of overriding importance to determine the origin of the fines and the amount, location and process of storage. There is little doubt that the characteristics of particles can be used to derive this information. There is no general agreement, however, about the characteristics that should be considered in such investigations. Furthermore, scientists have a great demand for simple methods, especially for routine use under dry weather conditions when suspended particle concentrations are low. This investigation shows that, in addition to loss on ignition, the determination of fractal dimension and particle colour also provide a fast and easy approach. After filtering the suspensions through glass microfibre filters, the dried filter residues are scanned by a colour scanner. Particle-bound cations and heavy metals were analysed by atomic absorption spectrometry after material decomposition with nitric acid. Fractal dimensions were obtained from measurement of the digital pictures using standard methods of digital image analysis. The fractal dimension decreases, indicating an increase in the regularity of particle morphology as one moves from gravel-stored sediment to surface-stored sediment to suspended sediment. Generally, flocs with high organic content exhibit more irregular morphology while single mineral particles have a more regular shape. In this study, the dominant factor for variable particle morphology was determined to be the mechanical forces influencing the flocs. An increase in shear associated with high flows and the impact of colliding with the channel bed appears to result in less flocculated, more regular particles at the surface. In addition, the morphology of particles shows that the exchange of particles in the gravel bed takes place during and shortly after flood events when the armoured layer is broken up and the sediment down to a depth of several centimetres is disturbed. Deposition onto the sediment surface was observed during the falling limb of every event. Surface sediment and suspended sediment show similarities in loss on ignition and particle morphology, particularly in low flow conditions when the stored amount of 25 mg/cm2 is not exceeded. The exchange between suspended sediment sources over the course of a year can be described using colour variation of the fine sediment. Along with particle-bound manganese, it can be shown that during both the winter month, which exhibit a high baseflow, and flood events, distant sediment sources predominate. In summer low flow conditions, in-channel sources are more important. Furthermore, the use of colour values can allow prediction of the sediment chemical properties as, for example a significant linear correlation between particle colour and particle-bound manganese was found.

A century of hydrological variability and trends in the Fraser River Basin

This study examines the 1911‐2010 variability and trends in annual streamflow at 139 sites across the Fraser River Basin (FRB) of British Columbia (BC), Canada. The Fraser River is the largest Canadian waterway flowing to the Pacific Ocean and is one of the world’s greatest salmon rivers. Our analyses reveal high runoff rates and low interannual variability in alpine and coastal rivers, and low runoff rates and high interannual variability in most streams in BC’s interior. The interannual variability in streamflow is also low in rivers such as the Adams, Chilko, Quesnel and Stuart where the principal salmon runs of the Fraser River occur. A trend analysis shows a spatially coherent signal with increasing interannual variability in streamflow across the FRB in recent decades, most notably in spring and summer. The upward trend in the coefficient of variation in annual runoff coincides with a period of near-normal annual runoff for the Fraser River at Hope. The interannual variability in streamflow is greater in regulated rather than natural systems; however, it is unclear whether it is predominantly flow regulation that leads to these observed differences. Environmental changes such as rising air temperatures, more frequent polarity changes in large-scale climate teleconnections such as El

Changes in Sediment Sources following Wildfire in Mountainous Terrain: A Paired–Catchment Approach, British Columbia, Canada

This paper describes a study examining the potential of mineral magnetic, geochemical and organic properties to determine if a 2003 wildfire in a catchment in British Columbia, Canada, caused a change in the sources of the suspended sediment transported in the channel relative to a nearby unburnt (reference) catchment. The results show that some of the properties offer the potential to determine sediment sources in the unburnt catchment. However, the 2003 wildfire modified the concentrations of some properties and this can either compromise or enhance their ability as tracers in the burnt catchment. At present, the source tracing results are inconclusive. This has implications for the use of certain properties as fingerprints and raises important issues about approaches to sediment source identification.

Recent (1995-1998) Canadian research on contemporary processes of river erosion and sedimentation, and river mechanics.

Canadian research on contemporary erosion and sedimentation processes covers a wide range of scales, processes, approaches and environmental problems. This review of recent research focuses on the themes of sediment yield, land-use impact, fine-sediment transport, bed material transport and river morphology and numerical modelling of fluvial landscape development. Research on sediment yield and denudation has confirmed that Canadian rivers are often dominated by riparian sediment sources. Studies of the effects of forestry on erosion, in-stream sedimentation and habitat are prominent, including major field experimental studies in coastal and central British Columbia. Studies of fine-sediment transport mechanisms have focused on the composition of particles and the dynamics of flocculation. In fluvial dynamics there have been important contributions to problems of turbulence-scale flow structure and entrainment processes, and the characteristics of bedload transport in gravel-bed rivers. Although much of the work has been empirical and field-based, results of numerical modelling of denudational processes and landscape development also have begun to appear. The nature of research in Canada is driven by the progress of the science internationally, but also by the nature of the Canadian landscape, its history and resource exploitation. Yet knowledge of Canadian rivers is still limited, and problems of, for example, large pristine rivers or rivers in cold climates, remain unexplored. Research on larger scale issues of sediment transfer or the effects of hydrological change is now hampered by reductions in national monitoring programmes. This also will make it difficult to test theory and assess modelling results. Monitoring has been replaced by project- and issues-based research, which has yielded some valuable information on river system processes and opened opportunities for fluvial scientists. However, future contributions will depend on our ability to continue with fundamental fluvial science while fulfilling the management agenda.

Sources of variability in fatty acid (FA) biomarkers in the application of compound-specific stable isotopes (CSSIs) to soil and sediment fingerprinting and tracing: A review.

Determining soil redistribution and sediment budgets in watersheds is often challenging. One of the methods for making such determinations employs soil and sediment fingerprinting techniques, using sediment properties such as geochemistry, fallout radionuclides, and mineral magnetism. These methods greatly improve the estimation of erosion and deposition within a watershed, but are limited when determining land use-based soil and sediment movement. Recently, compound-specific stable isotopes (CSSIs), which employ fatty acids naturally occurring in the vegetative cover of soils, offer the possibility of refining fingerprinting techniques based on land use, complementing other methods that are currently in use. The CSSI method has been met with some success; however, challenges still remain with respect to scale and resolution due to a potentially large degree of biological, environmental and analytical uncertainty. By better understanding the source of tracers used in CSSI work and the inherent biochemical variability in those tracers, improvement in sample design and tracer selection is possible. Furthermore, an understanding of environmental and analytical factors affecting the CSSI signal will lead to refinement of the approach and the ability to generate more robust data. This review focuses on sources of biological, environmental and analytical variability in applying CSSI to soil and sediment fingerprinting, and presents recommendations based on past work and current research in this area for improving the CSSI technique. A recommendation, based on current information available in the literature, is to use very-long chain saturated fatty acids and to avoid the use of the ubiquitous saturated fatty acids, C16 and C18.

Organic matter composition of gravel-stored sediments from salmon-bearing streams

The objective of this project was to evaluate the changing composition and structure of the sediment-associated organic matter (OM) stored in the gravel bed of highly productive salmon-bearing streams and, determine if the OM changes affect the morphology and settling rates of the sediment. In July of 2001, a dozen infiltration gravel bags were buried in the channel bed of O’Ne-eil Creek in northern British Columbia (Canada) to collect fine sediment and the associated organic matter for chemical and morphological analysis. The bags were removed over a 10 week period which incorporated summer low flows, salmon spawning, salmon die-off and the onset of autumn low flow conditions. Our results indicate two visibly different structures in the organic matter film overlying the mineral material of the flocs. A web-like structure was noted during mid-spawn while a film-like covering was observed in pre-spawn and post-fish periods. The strength of the film-like covering is surmised to be associated with the larger gravel-stored floc sizes noted at these times. Chemical analysis of these biofilms indicated higher metal complexation properties during the spawning periods as opposed to before or after salmon were present. The changing OM contributions were associated with changes in floc size, density and settling rates. The physical disturbance to the gravels associated with spawning salmon was also correlated with altered characteristics of the gravel-stored flocs.

Selecting Color-based Tracers and Classifying Sediment Sources in the Assessment of Sediment Dynamics Using Sediment Source Fingerprinting

The use of sediment color as a fingerprint property to determine sediment sources is an emerging technique that can provide a rapid and inexpensive means of investigating sediment sources. The present study aims to test the feasibility of color fingerprint properties to apportion sediment sources within the South Tobacco Creek Watershed (74 km) in Manitoba, Canada. Suspended sediment from 2009 to 2011 at six monitoring stations and potential source samples along the main stem of the creek were collected. Reflectance spectra of sediments and source materials were quantified using a diffuse reflectance spectrometry, and 16 color coefficients were derived from several color space models. Canonical discriminant analysis was used to reclassify and downsize sediment source groups. After the linear additive test and stepwise discriminant function analysis, four color coefficients were chosen to fit the Stable Isotope Analysis in R model. Consistent with the conventional fingerprinting approach, the color fingerprint results demonstrated a switch in the dominant sediment source between the headwaters and the outlet of the watershed, with the main sources being topsoil in the upper reaches, whereas outcrop shale and stream bank materials dominated in the lower reaches. The color fingerprinting approach can be integrated with conventional fingerprints (e.g., geochemical and fallout radionuclide properties) to improve source discrimination, which is a key component for source ascription modeling. We concluded that the use of color fingerprints is a promising, cost-effective technique for sediment source fingerprinting.

The impact of a catastrophic mine tailings impoundment spill into one of North America's largest fjord lakes: Quesnel Lake, British Columbia, Canada

On 4 August 2014, a catastrophic breach of the Mount Polley mine tailings impoundment released ~25 M m3 of tailings and water and scoured an unknown quantity of overburden into the West Basin of Quesnel Lake. We document Quesnel Lake and Quesnel River observations for 2 months postspill. Breach inflows raised Quesnel Lake by 7.7 cm, equivalent to ~21 M m3. The West Basin hypolimnion was modified immediately, exhibiting increased temperature (~5°C to 6–7.5°C), conductivity (110 to 160 μS/cm), and turbidity (<1 to 200–1000 nephelometric turbidity units (NTU)). Cooscillating seiches moved West Basin hypolimnetic water both westward and eastward contaminating the Main Basin. Postspill, high-turbidity water propagated eastward (~1 cm/s), introducing a persistent ~20 m thick layer below the thermocline and an ~30 m thick layer at the bottom. The contaminant introduction, mobilization, and bioaccumulation may pose risks to resident and anadromous fish stocks, which support recreational, commercial, and First Nations fisheries.

Bidirectional delivery of organic matter between freshwater and marine systems: the role of flocculation in Pacific salmon streams

Abstract The literature regarding freshwater and marine exchanges of organic matter (OM) focuses predominantly on the unidirectional delivery of allochthonous and autochthonous material from freshwater to the marine environment. Another ecologically significant exchange occurs when anadromous organisms move into coastal and interior watersheds and bring marine-accrued OM and its incorporated marine-derived nutrients (MDN). We use the example of Pacific salmon streams to discuss bidirectional transfers of OM in the upstream and downstream directions with specific reference to the role of flocculation. A fish-floc feedback loop has recently been presented as a mechanism that allows transfer of salmon OM to the gravel-bed matrix in the form of flocs. In the proposed fish-floc feedback loop, the OM source is salmon, but the OM source will change with fish species. Once fish-based flocs enter the gravel bed they can be stored or used by benthic organisms. A salmon disturbance regime that includes redistribution of gravel, fine sediment, and biofilm during redd construction and release of salmon OM to the stream is integral to the fish-floc feedback loop because it provides the inorganic fine sediment and OM required for floc formation. The MDN subsidy provided by returning salmon is important for natal watershed functioning as illustrated by a conceptual OM feedback loop that links these freshwater and marine exchanges. Retention of floc-bound OM in the gravel bed afforded by settling flocs allows slower downstream transfer of nutrients en route to the ocean and a correspondingly increased period for uptake in food webs downstream.