Cheryl I. E. Wiramanaden

Selenium uptake and speciation in wild and caged fish downstream of a metal mining and milling discharge

The aim of this research was to evaluate the dominance of the feeding pathway with respect to selenium (Se) uptake and speciation in fish inhabiting the receiving waters downstream of a uranium processing mill in northern Saskatchewan, Canada. The experimental design included analysis of Se in the predominant fish species located in the study area, a caging validation study using wild, naïve (i.e., collected from a reference lake) lake chub (Couesius plumbeus) and spottail shiner (Notropis hudsonius), and a 21-day feeding cage study using wild naïve lake chub. Three exposure lakes located downstream of the uranium mill and one reference lake situated in an adjacent watershed were studied to investigate a gradient of Se exposure. Lake chub were identified as more suitable candidates for caging due to higher survival and condition factor at the completion of the 21-day trial. Analytical results indicated that lake chub caged in the exposure lakes had significantly greater whole-body Se concentrations after 21 days compared to fish caged in the reference lake. Selenium speciation results (obtained using X-ray absorption spectroscopy) from wild and caged lake chub indicated that organic Se modeled as selenomethionine was the dominant form of Se found in both wild and caged lake chub from the exposure lakes, and that selenomethionine (R-Se-R) acts as a marker of bioavailable Se exposure.

Selenium distribution in a lake system receiving effluent from a metal mining and milling operation in Northern Saskatchewan, Canada

The release of selenium (Se) at relatively low concentrations into aquatic ecosystems over time can result in the accumulation and, if thresholds are exceeded, subsequent adverse effects in sensitive species, including higher trophic levels (such as fish). A milling operation in Northern Saskatchewan, Canada, releases treated effluent into a small stream system, and Se has accumulated in sediments and aquatic biota over time. The present study evaluated four small lakes downstream of the effluent discharge point, and one lake upstream, in order to describe and understand the distribution of Se in abiotic environmental compartments and the transfer of Se into benthic macroinvertebrates. The concentrations of Se in sampled sediments were highly variable but exceeded proposed thresholds for the protection of fish and aquatic birds in all study lakes downstream of the effluent discharge point. Selenium concentrations in surface water, whole-sediment, and sediment pore water revealed that whole-body Se concentrations in benthic invertebrates (chironomids) are best correlated with Se in pore water. It is proposed that Se accumulates in sediments through an association with the total organic carbon content of sediment and that Se is fixed from the surface water by micro-organisms and primary producers. The relationship between Se in pore water and Se in whole sediments appears to be influenced by the organic carbon content of each medium, and Se bioavailability in sediment and transfer to higher trophic levels via benthic macroinvertebrates is likely speciation dependent.

Selenium Speciation in Whole Sediment using X-ray Absorption Spectroscopy and Micro X-ray Fluorescence Imaging

A field survey was conducted in a freshwater lake system in the Athabasca Basin, northern Saskatchewan, Canada that receives treated metal mining and milling process effluent containing elevated levels of selenium. Whole sediment, pore water, surface water, and chironomid larvae were analyzed in an attempt to link whole sediment selenium speciation to various environmental factors, including selenium availability to benthic macro-invertebrates, a trophic level through which selenium can enter the diet of higher trophic level organisms. Speciation was measured using synchrotron-based selenium K-edge X-ray absorption spectroscopy (XAS). All lake averages of sediment samples (reference or exposure sites) contained a significant proportion (approximately 50%) of elemental selenium which is relatively insoluble in water, immobile, and not considered to be bioavailable. The presence of elemental selenium was confirmed by extended X-ray absorption fine structure (EXAFS) analysis of select samples. Inorganic metal selenides were also found in whole sediment samples and confirmed using micro X-ray fluorescence imaging. Dissolved selenium concentrations in pore water were correlated to the amount of selenite in whole sediments provided that the sites were classified according to whole sediment sand content. Sand content itself is likely inversely correlated to sediment organic matter content, adsorption sites, and redox potential.

Selenium bioaccumulation and speciation in Chironomus dilutus exposed to water-borne selenate, selenite, or seleno-DL-methionine.

The objective of the present study was to describe the uptake and elimination kinetics of selenium (Se) administered in the forms of selenate, selenite, and selenomethionine (seleno-DL-methionine) in different life stages of the midge Chironomus dilutus, and to determine the relationship between Se bioavailability and Se speciation using X-ray absorption spectroscopy (XAS). Midge larvae exposed to 4.3 µg/L as dissolved selenate for 10 d of had negligible accumulation of Se (indistinguishable from control organisms). However, larvae rapidly accumulated Se over 10 d of exposure to 3.8 and 1.8 µg/L selenite and seleno-DL-methionine (Se-met), respectively. Most Se accumulated by larvae exposed to selenite or Se-met was retained after 10 d of elimination in clean water. When additional midge larvae were exposed to Se until emergence, Se accumulated during the larval stage was largely retained in the adults. Although a strong correlation was found between the adult whole-body Se concentration and the Se concentration in the exuvia after emergence, only a minor loss of Se occurred in the shed exuvia compared with larvae and adult whole-body concentrations. X-ray absorption spectroscopy analysis showed that organic selenides and diselenides, modeled as Se-met and selenocystine, respectively, were the dominant forms of Se in both the larval and adult insect stages. The proportion and concentration of organic selenides (selenomethionine) increased in larvae and adults exposed to Se-met and selenite compared with larvae exposed to selenate, whereas the concentration of diselenides (selenocystine) remained relatively constant for all treatments.

Biogeochemical Mechanisms of Selenium Exchange between Water and Sediments in Two Contrasting Lentic Environments

The biogeochemical mechanisms of Se exchange between water and sediments in two contrasting lentic environments were assessed through examination of Se speciation in the water column, porewater, and sediment. High-resolution (7 mm) vertical profiles of <0.45 μm Se species across the sediment-water interface demonstrate that the behavior of dissolved Se(VI), Se(IV), and organo-Se are closely linked to redox conditions as revealed by porewater profiles of redox-sensitive species (dissolved O2, NO3-, Fe, Mn, SO4(2-), and ΣH2S). At both sites Se(VI) is removed from solution in suboxic near-surface porewaters demonstrating that the sediments are serving as diffusive sinks for Se. X-ray absorption near edge spectroscopy (XANES) of sediments suggests that elemental Se and organo-Se represent the dominant sedimentary sinks for dissolved Se. Dissolved Se(IV) and organo-Se are released to porewaters in the near-surface sediments resulting in the diffusive transport of these species into the water column, where between-site differences in the depths of release can be linked to differences in redox zonation. The presence or absence of emergent vegetation is proposed to present a dominant control on sedimentary redox conditions as well as on the recycling and persistence of reduced Se species in bottom waters.

Integrative assessment of selenium speciation, biogeochemistry, and distribution in a northern coldwater ecosystem

For the past decade, considerable research has been conducted at a series of small lakes receiving treated liquid effluent containing elevated selenium (Se) from the Key Lake uranium (U) milling operation in northern Saskatchewan, Canada. Several studies related to this site, including field collections of water, sediment, and biota (biofilm and/or periphyton, invertebrates, fish, and birds), semicontrolled mesocosm and in situ caging studies, and controlled laboratory experiments have recently been published. The aim of the present investigation was to compile the site-specific information obtained from this multidisciplinary research into an integrative perspective regarding the influence of Se speciation on biogeochemical cycling and food web transfer of Se in coldwater ecosystems. Within lakes, approximately 50% of sediment Se was in the form of elemental Se, although this ranged from 0% to 81% among samples. This spatial variation in elemental Se was positively correlated with finer particles (less sand) and percent total organic C content in sediments. Other Se species detected in sediments included selenosulfides, selenite, and inorganic metal selenides. In contrast, the major Se form in sediment-associated biofilm and/or periphyton was an organoselenium species modeled as selenomethionine (SeMet), illustrating the critical importance of this matrix in biotransformation of inorganic Se to organoselenium compounds and subsequent trophic transfer to benthic invertebrates at the base of the food web. Detritus displayed a Se speciation profile intermediate between sediment and biofilm, with both elemental Se and SeMet present. In benthic detritivore (chironomid) larvae and emergent adults, and in foraging and predatory fishes, SeMet was the dominant Se species. The proportion of total Se present as a SeMet-like species displayed a direct nonlinear relationship with increasing whole-body Se in invertebrates and fishes, plateauing at approximately 70% to 80% of total Se as a SeMet-like species. In fish collected from reference lakes, a selenocystine-like species was the major Se species detected. Similar Se speciation profiles were observed using 21-day mesocosm and in situ caging studies with native small-bodied fishes, illustrating the efficient bioaccumulation of Se and use of these semicontrolled approaches for future research. A simplified conceptual model illustrating changes in Se speciation through abiotic and biotic components of lakes was developed, which is likely applicable to a wide range of northern industrial sites receiving elevated Se loading into aquatic ecosystems.

Insect excretes unusual six-coordinate pentavalent arsenic species

Environmental context. Arsenate, in which oxidised arsenic is coordinated to four oxygen atoms, is common in the environment. We have found that a moth larva excretes an unusual form of oxidised arsenic which is bound to six oxygen atoms. Since the chemical groups which give rise to this species are abundant in environmental and biological systems, more research is needed into the possible presence of such six-coordinate complexes in natural systems. Abstract. Arsenate, in which pentavalent arsenic (AsV) is approximately tetrahedrally coordinated by oxygen, is common in biological or environmental systems. Octahedral coordination of AsV by oxygen is known chemically but hitherto has not been observed in natural systems. In an effort to understand the effect of elevated levels of arsenic on insects and other insectivorous animals in the food chain, larvae of the moth bertha armyworm (Mamestra configurata Walker) [Lepidoptera : Noctuidae] were examined under laboratory conditions. Synchrotron X-ray absorption spectroscopy was used to show that the exuvia (shed skin) and frass (fecal matter) contain an unusual AsV species six-coordinated by oxygen. The species is modelled as a low pH octahedral chelation complex with vicinal dihydroxyls such as glycerol or catechol. Structural characterisation using extended X-ray absorption fine structure (EXAFS) shows interatomic distances which are more similar to those of the glycerol complex and the near-edge also shows more similarity with the aliphatic chelator. The larvae may be using the six-coordinate AsV species as a specific excretory molecule. Since vicinal dihydroxyl species are common, more research is needed into the possible presence of such six-coordinate complexes in natural systems.

An in situ assessment of selenium bioaccumulation from water-, sediment-, and dietary-exposure pathways using caged Chironomus dilutus larvae.

An in situ caging study was conducted downstream of a metal mine in northern Canada to determine the significance of surface water versus sediment exposure on selenium (Se) bioaccumulation in the benthic invertebrate Chironomus dilutus. Laboratory-reared C. dilutus larvae were exposed to either site-specific whole-sediment and surface water or surface water only for 10 d at sites with differing sediment and Se characteristics. Results showed elevated whole-body Se concentrations in C. dilutus larvae when exposed to sediment and water, compared with larvae exposed to Se in the surface water only at concentrations ranging from <1 µg Se/L to 12 µg Se/L. In response to these findings, a second in situ experiment was conducted to investigate the importance of dietary Se (biofilm and detritus) versus whole-sediment-exposure pathways. Larvae exposed to sediment detritus had the highest Se concentrations after 10 d of exposure (15.6 ± 1.9 µg/g dry wt) compared with larvae exposed to whole-sediment (12.9 ± 1.7 µg/g dry wt) or biofilm (9.9 ± 1.6 µg/g dry wt). Detritus and biofilm appear to be enriched sources of organic Se, which are more bioaccumulative than inorganic Se. Midge larvae from the reference treatment contained elevated concentrations of diselenides (i.e., selenocystine), while larvae from the biofilm treatment had the highest concentrations of selenomethionine-like compounds, which may be a biomarker of elevated Se exposures derived from anthropogenic sources. Whenever possible, Se concentrations in the organic fraction of sediment should be measured separately from whole-sediment Se and used for more accurate ecological risk assessments of potential Se impacts on aquatic ecosystems.

Assessment of radium‐226 bioavailability and bioaccumulation downstream of decommissioned uranium operations, using the caged oligochaete (Lumbriculus variegatus)

The present study investigated the integrated effects of several geochemical processes that control radium-226 ((226) Ra) mobility in the aquatic environment and bioaccumulation in in situ caged benthic invertebrates. Radium-226 bioaccumulation from sediment and water was evaluated using caged oligochaetes (Lumbriculus variegatus) deployed for 10 d in 6 areas downstream of decommissioned uranium operations in Ontario and Saskatchewan, Canada. Measured (226) Ra radioactivity levels in the retrieved oligochaetes did not relate directly to water and sediment exposure levels. Other environmental factors that may influence (226) Ra bioavailability in sediment and water were investigated. The strongest mitigating influence on (226) Ra bioaccumulation factors was sediment barium concentration, with elevated barium (Ba) levels being related to use of barium chloride in effluent treatment for removing (226) Ra through barite formation. Observations from the present study also indicated that (226) Ra bioavailability was influenced by dissolved organic carbon in water, and by gypsum, carbonate minerals, and iron oxyhydroxides in sediment, suggestive of sorption processes. Environmental factors that appeared to increase (226) Ra bioaccumulation were the presence of other group (II) ions in water (likely competing for binding sites on organic carbon molecules), and the presence of K-feldspars in sediment, which likely act as a dynamic repository for (226) Ra where weak ion exchange can occur. In addition to influencing bioavailability to sediment biota, secondary minerals such as gypsum, carbonate minerals, and iron oxyhydroxides likely help mitigate (226) Ra release into overlying water after the dissolution of sedimentary barite. Environ Toxicol Chem 2015;34:507-517.

The biogeochemical behaviour of selenium in two lentic environments in the Elk River Valley, British Columbia

The biogeochemical behaviour of selenium (Se) in two lentic environments (Goddard Marsh (GM) and Fording River Oxbow (FRO)) was assessed through detailed examination of Se speciation in bottom water, porewater and sediment components. The depositional environments at GM and FRO differ with regards to organic matter content, organic matter sources (as revealed by C:N ratios) and redox character. X-ray absorption near edge spectral (XANES) data suggest that elemental Se and organo-Se represent the dominant hosts for Se at GM and FRO. At both sites, the vertical distributions of dissolved Se species in porewater are closely linked to the profiles of redox-sensitive metabolites. Porewater profiles indicate that the sediments at GM and FRO are serving as diffusive sinks for Se through in situ adsorption/precipitation of Se in suboxic horizons. Although the sediments at both sites serve as net sinks for dissolved Se, interfacial peaks in dissolved selenite (Se) and organo-Se demonstrate these species are recycled back into the water column. The conditions present at GM are more favourable for the recycling of reduced Se species. Such observations can be linked to subtle differences in redox conditions as illustrated by profiles of redox-sensitive species (dissolved NO3, Fe, Mn, SO4 and ΣH2S). These differences have important implications to both the recycling of reduced Se species into the water column and Se uptake by aquatic biota. Implications with regards to Se management, bioremediation and biologically availability (food chain transport) are discussed. INTRODUCTION The fine-grained organic-rich substrates typical to lentic systems (e.g., wetlands, ponds, lakes) serve as optimum media for the microbially-mediated transformations of selenate (Se) to reduced forms, including selenite (Se), elemental selenium (Se) and organic species (Masscheleleyn and Patrick 1993; Zhang and Moore 1996; Simmons and Wallschlager 2005). Accordingly, understanding and quantifying mechanisms involved in Se cycling within lentic environments is required to assess the long-term fate of Se and risks to biological receptors. Studies to date conducted through the Elk Valley Selenium Task Force (EVSTF), including assessments of fish, waterbirds, waterfowl and amphibians (McDonald and Strosher 2000; Minnow 2004; Golder 2005), have advanced our understanding of the effects of Se on biological receptors in both lentic and lotic environments. However, there remains a dearth of information with respect to the biogeochemical mechanisms controlling the speciation, accumulation and remobilization of Se within lentic environments in the region. B.C.’32 Annual Mine Reclamation Symposium Technical Paper 8 2 To expand our current understanding of Se behaviour in lentic systems, studies were conducted in two lentic environments in the Elk River Valley of southeastern B.C. This study represents a collaborative effort between the EVSTF, Lorax Environmental Services Ltd., Trent University (Dr. Dirk Wallschlager), University of Saskatoon (Drs. Cheryl Wiramanaden and Ingrid Pickering) and Laurentian University (Dr. Nelson Belzile). The approach focused on the collection of high vertical-resolution profiles of Se species in sediment, bottom water and porewater, with the primary objective being to delineate the biogeochemical processes governing Se behaviour. The results have both local and global relevance to our understanding of Se behaviour in aquatic systems. The preliminary work presented herein, prepared for the EVSTF, has not been fully reviewed nor endorsed by its membership. FIELD AND ANALYTICAL METHODS Environmental Setting Field surveys at Goddard Marsh (GM) (Elkview Coal Operations) and Fording River Oxbow (FRO) (Fording River Operations) were conducted between August 21-23 and September 4-7, 2007. These lentic zones were selected for study based on previous work at these sites, ecological significance, and proximity to mine-related inputs. GM is located immediately downstream of a sediment-pond discharge from Elkview Mine, and comprises a dense cattail (Typha latifolia) marsh with limited areas of open water. Water depths range from ~0.5 to 1.0 m. Sediments at GM are organic rich and fine-grained. FRO is located adjacent to the Fording River ~9 km downstream of the Fording Mine. FRO extends for several hundred metres and comprises narrow channels and open ponds which are hydraulically connected to the Fording River. Water depths at FRO range from 0.5 to 1.5 m. The system is replete in organic matter and hosts fine-grained sediments. Field Methods Duplicate sediment cores were collected by hand from GM and FRO using 8 cm diameter butyrate tubing. Cores were extruded and sliced at intervals ranging from 1 cm in thickness near the sediment-water interface to 5 cm in thickness at deeper sediment depths. Sediment sub-samples were placed in polyethylene bags and frozen prior to transport. The post-depositional behaviour of Se and exchange with the overlying water column was assessed by sampling of the porewaters and bottom waters using dialysis arrays (peepers), as described in Martin et al. (2002, 2003). The peepers afford 7 mm-resolution profiling of dissolved constituents (0.45 μm pore size) from ~20 cm above the benthic boundary to a sub-interface depth of ~30 cm. Dissolved metal samples were acidified to pH <2 with ultrapure nitric acid while samples for nutrients and sulfate analysis were frozen. For hydrogen sulfide analysis, a 2.0 mL sample was taken and spiked with 50 μL of 1 M zinc acetate. Samples for Se speciation analysis were frozen with dry ice immediately upon collection. Analytical Methods Total Se in porewaters was determined by inductively-coupled-plasma dynamic-reaction-cell massspectrometry (ICP-DRC-MS). Inorganic Se species in porewater were determined by anion-exchange B.C.’32 Annual Mine Reclamation Symposium Technical Paper 8 3 chromatography coupled to ICP-DRC-MS (AEC-ICP-DRC-MS), similar to Wallschlager and Roehl (2001). Dissolved organic selenium was converted to selenite (Se) by selective UV-photo-oxidation, and then determined indirectly (by subtraction of the sample’s native selenite (Se) concentration) by hydride generation-atomic fluorescence spectrometry (HG-AFS) (Chen et al., 2005). Determinations of dissolved trace element concentrations were performed using inductively-coupled plasma mass spectrophotometry (ICP-MS) at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. Sulfate and nitrate concentrations in porewaters were measured by ion chromatography and total sulfide (ΣH2S = S, HS and H2S) was measured spectrophotometrically. Total carbon and sulphur concentrations in sediments were determined by combustion/gas chromatography at the University of British Columbia. Carbonate carbon was determined by coulometry. Organic carbon was determined by subtracting carbonate carbon values from the total value. Trace elements were analyzed by inductively-coupled plasma optical emission (ICP-OES) and mass spectrometry (ICP-MS) using solutions prepared by fusing sub-samples in lithium metaborate (LiBO2), followed by dissolution of the quenched glass in 10% nitric acid (HNO3). X-ray absorption near edge spectra (XANES) data were collected using the synchrotron at the Canadian Light Source Saskatoon, SK. XANES probes the absorption characteristics of a particular electron shell using tunable synchrotron light. The geometry of the resulting spectra is valence dependent so it is possible to determine the specific elemental oxidation states present (i.e., Se, Se, Se, Se) (Pickering et al., 1995). As well, XANES spectra can be used to obtain semi-quantitative determinations of the relative abundance of each oxidation state. To quantify the relative contribution of various Se forms, a XANES library of known Se compounds was compared to the sample spectra. RESULTS AND DISCUSSION Sediments Contrasts between the depositional environments at GM and FRO are illustrated by their carbon (C), nitrogen (N) and sulfur (S) content (Figure 1). The greater organic carbon content at GM (25 to 30 wt.%) in comparison to FRO (5 to 7 wt.%) likely relates to differences in the source(s) of organic matter. Specifically, the C-Org:N ratio in GM sediments (mean = 38) is closer to the C:N signature of terrestrial organic matter (45 to 50:1), while the C-Org:N ratio at FRO (mean = 20) is similar to organic matter produced by plankton decomposition (12:1) (Wetzel 1975). The higher C:N at GM indicates that the organic matter content at this site is composed largely of decomposing wetland vascular plants (e.g., Typha sp.). Conversely, the lower C:N contents at FRO imply a greater portion of the organic matter originates from in situ sources such as algal production. These differences likely have relevance to Se accumulation in sediments. Total-Se in sediments at GM range from 7 to 71 mg/kg dry wt. (mean = 37 mg/kg) while deposits at FRO range from 2 to 19 mg/kg dry wt. (mean = 10 mg/kg) (Figure 2). XANES spectra suggest that elemental Se, organo-Se (possibly seleno-methionine) and selenite (sorbed Se), are the dominant hosts for Se at B.C.’32 Annual Mine Reclamation Symposium Technical Paper 8 4 both GM and FRO (Figure 2). Of these, elemental phases and organo-Se contribute most to the total sediment inventory, which account for on average 35% and 50%, respectively, of the total at both sites. Org-C (wt.%) 0 5 10 15 20 25 30 35 0