Exploitation of bitumen-rich deposits in the Alberta Oil Sands Region (AOSR) by large-scale minin... more Exploitation of bitumen-rich deposits in the Alberta Oil Sands Region (AOSR) by large-scale mining and processing activities has generated widespread concern about the potential for dispersal of harmful contaminants to aquatic ecosystems via fluvial and atmospheric pathways. The release of mercury has received attention because it is a potent neurotoxin for wildlife and humans. However, knowledge of baseline mercury concentration prior to disturbance is required to evaluate the extent to which oil sands development has contributed mercury to aquatic ecosystems. Here, we use stratigraphic analysis of total mercury concentration ([THg]) in radiometrically dated sediment cores from nine floodplain lakes in the AOSR and downstream Peace-Athabasca Delta (PAD) and two upland lakes in the PAD region to establish pre-1900 baseline [THg] and evaluate if [THg] has become enriched via fluvial and atmospheric pathways since oil sands mining and processing began in 1967. Concentrations of THg in...
This project try to establish and investigate the correlations between rock physical properties (... more This project try to establish and investigate the correlations between rock physical properties (porosity, permeability and sonic velocity) of carbonates rocks from Gunung Rapat, Ipoh, Perak. Generally, correlations between rock physical properties of the carbonates are not easy to be established as compared to siliclastic sedimentary rocks due to the heterogeneity that they have in terms of pore type, grains and geometry. We used correlations of porosity-sonic velocity, permeability-sonic velocity and porositypermeability in order to study the interrelationship between the carbonate rocks physical properties. The preliminary results show a large scatter in the correlations of porositysonic velocity, permeability-sonic velocity and porosity-permeability thus indicates the heterogeneity of pore types, structure and distribution in the carbonates. From the SEM images, we found that the scattered correlations are may due to different kinds of microporosity and micrite microtextures presence in the carbonate rocks and also due to the variations in pore geometry. This study has a great significance in the process of a better understanding of how rock properties of carbonates relate to each other.
<p>Episodic flood events are critical for recharging water balance of flood... more <p>Episodic flood events are critical for recharging water balance of floodplain lakes and maintaining their ecological integrity, yet are subject to alteration in frequency and magnitude by natural and anthropogenic processes that operate over a range of spatial and temporal scales. To evaluate roles of potential stressors, paleolimnological reconstructions are used to obtain insights into hydrological variability of dynamic floodplain lakes. However, spatial and temporal integration is often underdeveloped because different paleolimnological measurements must be applied across lakes due to the wide range of energy conditions that impart marked differences in sediment composition. Here, we use a linear discriminant analysis to identify 10 significant elemental concentrations in surveyed sediment from multiple sampling campaigns that distinguish the geochemical fingerprints of three end-member sources in lakes at the Peace-Athabasca Delta (PAD; Canada): the Athabasca River, the Peace River and local catchment runoff. Over 90% of the sediment samples were correctly classified into the original groups after cross-validation due to the distinctiveness of the three end members, which permits development of a robust Bayesian mixing model to discern the relative contributions of sediment from the three sources. We evaluate the mixing model at two adjacent lakes in the Athabasca sector of the PAD and demonstrate its effectiveness to discriminate three known hydrological phases during the past 300 years. Notably, the model infers ~60% of the sediment originated from the Peace River during the largest ice-jam flood event on record (1974), which was unrecognized by other methods. We then applied our model to sediment records from 18 lakes spanning the hydrological gradients across the 6000 km<sup>2</sup> PAD to further probe the hydrological evolution during the past ~150 years. Results demonstrate decline in frequency of flooding from both the Athabasca and Peace rivers and lake-level drawdown since the early 20<sup>th</sup> century and align remarkably well with prior interpretation of conventional paleohydrological records of individual lakes. We advocate our approach provides a universal method that can be applied across the full range of sediment composition to quantify change in source, frequency and magnitude of river floodwaters to lakes and is transferable to other dynamic floodplain landscapes where variation of sediment composition challenges efficacy of other approaches.</p>
The oxygen isotope composition (δ18O) of aquatic cellulose extracted from lake sediment cores has... more The oxygen isotope composition (δ18O) of aquatic cellulose extracted from lake sediment cores has long been used to reconstruct past hydrological responses to climate variation and anthropogenic (e.g. mining, agriculture, forestry) disturbance. Application of this method depends upon a constant oxygen isotope fractionation factor between aquatic cellulose and lake water, often reported as α18Ocell-lw = 1.028. Prior field-based assessments of α18Ocell-lw, however, commonly relied on one-time measures of lake water δ18O, which introduces uncertainties because values may not represent lake water δ18O at the time of cellulose synthesis. We field-tested the use of α18Ocell-lw = 1.028 across a broad hydrological gradient of lakes within the Peace-Athabasca Delta (PAD), west-central Canada, where we constrained cellulose production by periphyton on artificial substrates to bracketed measurements of lake water δ18O collected in late May 2015 and late June 2015. Cellulose-inferred lake water δ18O, calculated using α18Ocell-lw of 1.028 ± 0.0015, corresponded with the range of measured lake water δ18O in 36 of 52 (75%) of our study lakes. Agreement improved to 86% for ‘clean cellulose’ samples that appeared to be of higher quality (i.e. those with minimal minerogenic material). Mean apparent α18Ocell-lw calculated for clean cellulose samples, using both May lake water δ18O (1.0286) and the May–June mean lake water δ18O (1.0275), did not differ significantly from 1.028, but was significantly, albeit slightly, below 1.028 using June lake water δ18O (1.0264). Closer correspondence of apparent α18Ocell-lw, calculated using May and May–June average lake water δ18O, suggested rapid and early colonization and cellulose production by periphyton. For samples that were a mixture of cellulose and minerogenic material, mean apparent α18Ocell-lw was significantly below 1.028 for these corresponding lake water δ18O measurements, but differences were small and would potentially lead to under-estimation of cellulose-inferred lake water δ18O by only 1–2‰ in sediment stratigraphic records. Overall, strong agreement observed between the cellulose-inferred and directly measured lake water δ18O supports application of α18Ocell-lw = 1.028 ± 0.0015 and lends confidence to paleohydrological reconstructions using this method in lakes of the PAD and elsewhere.
Exploitation of bitumen-rich deposits in the Alberta Oil Sands Region (AOSR) by large-scale minin... more Exploitation of bitumen-rich deposits in the Alberta Oil Sands Region (AOSR) by large-scale mining and processing activities has generated widespread concern about the potential for dispersal of harmful contaminants to aquatic ecosystems via fluvial and atmospheric pathways. The release of mercury has received attention because it is a potent neurotoxin for wildlife and humans. However, knowledge of baseline mercury concentration prior to disturbance is required to evaluate the extent to which oil sands development has contributed mercury to aquatic ecosystems. Here, we use stratigraphic analysis of total mercury concentration ([THg]) in radiometrically dated sediment cores from nine floodplain lakes in the AOSR and downstream Peace-Athabasca Delta (PAD) and two upland lakes in the PAD region to establish pre-1900 baseline [THg] and evaluate if [THg] has become enriched via fluvial and atmospheric pathways since oil sands mining and processing began in 1967. Concentrations of THg in...
This project try to establish and investigate the correlations between rock physical properties (... more This project try to establish and investigate the correlations between rock physical properties (porosity, permeability and sonic velocity) of carbonates rocks from Gunung Rapat, Ipoh, Perak. Generally, correlations between rock physical properties of the carbonates are not easy to be established as compared to siliclastic sedimentary rocks due to the heterogeneity that they have in terms of pore type, grains and geometry. We used correlations of porosity-sonic velocity, permeability-sonic velocity and porositypermeability in order to study the interrelationship between the carbonate rocks physical properties. The preliminary results show a large scatter in the correlations of porositysonic velocity, permeability-sonic velocity and porosity-permeability thus indicates the heterogeneity of pore types, structure and distribution in the carbonates. From the SEM images, we found that the scattered correlations are may due to different kinds of microporosity and micrite microtextures presence in the carbonate rocks and also due to the variations in pore geometry. This study has a great significance in the process of a better understanding of how rock properties of carbonates relate to each other.
<p>Episodic flood events are critical for recharging water balance of flood... more <p>Episodic flood events are critical for recharging water balance of floodplain lakes and maintaining their ecological integrity, yet are subject to alteration in frequency and magnitude by natural and anthropogenic processes that operate over a range of spatial and temporal scales. To evaluate roles of potential stressors, paleolimnological reconstructions are used to obtain insights into hydrological variability of dynamic floodplain lakes. However, spatial and temporal integration is often underdeveloped because different paleolimnological measurements must be applied across lakes due to the wide range of energy conditions that impart marked differences in sediment composition. Here, we use a linear discriminant analysis to identify 10 significant elemental concentrations in surveyed sediment from multiple sampling campaigns that distinguish the geochemical fingerprints of three end-member sources in lakes at the Peace-Athabasca Delta (PAD; Canada): the Athabasca River, the Peace River and local catchment runoff. Over 90% of the sediment samples were correctly classified into the original groups after cross-validation due to the distinctiveness of the three end members, which permits development of a robust Bayesian mixing model to discern the relative contributions of sediment from the three sources. We evaluate the mixing model at two adjacent lakes in the Athabasca sector of the PAD and demonstrate its effectiveness to discriminate three known hydrological phases during the past 300 years. Notably, the model infers ~60% of the sediment originated from the Peace River during the largest ice-jam flood event on record (1974), which was unrecognized by other methods. We then applied our model to sediment records from 18 lakes spanning the hydrological gradients across the 6000 km<sup>2</sup> PAD to further probe the hydrological evolution during the past ~150 years. Results demonstrate decline in frequency of flooding from both the Athabasca and Peace rivers and lake-level drawdown since the early 20<sup>th</sup> century and align remarkably well with prior interpretation of conventional paleohydrological records of individual lakes. We advocate our approach provides a universal method that can be applied across the full range of sediment composition to quantify change in source, frequency and magnitude of river floodwaters to lakes and is transferable to other dynamic floodplain landscapes where variation of sediment composition challenges efficacy of other approaches.</p>
The oxygen isotope composition (δ18O) of aquatic cellulose extracted from lake sediment cores has... more The oxygen isotope composition (δ18O) of aquatic cellulose extracted from lake sediment cores has long been used to reconstruct past hydrological responses to climate variation and anthropogenic (e.g. mining, agriculture, forestry) disturbance. Application of this method depends upon a constant oxygen isotope fractionation factor between aquatic cellulose and lake water, often reported as α18Ocell-lw = 1.028. Prior field-based assessments of α18Ocell-lw, however, commonly relied on one-time measures of lake water δ18O, which introduces uncertainties because values may not represent lake water δ18O at the time of cellulose synthesis. We field-tested the use of α18Ocell-lw = 1.028 across a broad hydrological gradient of lakes within the Peace-Athabasca Delta (PAD), west-central Canada, where we constrained cellulose production by periphyton on artificial substrates to bracketed measurements of lake water δ18O collected in late May 2015 and late June 2015. Cellulose-inferred lake water δ18O, calculated using α18Ocell-lw of 1.028 ± 0.0015, corresponded with the range of measured lake water δ18O in 36 of 52 (75%) of our study lakes. Agreement improved to 86% for ‘clean cellulose’ samples that appeared to be of higher quality (i.e. those with minimal minerogenic material). Mean apparent α18Ocell-lw calculated for clean cellulose samples, using both May lake water δ18O (1.0286) and the May–June mean lake water δ18O (1.0275), did not differ significantly from 1.028, but was significantly, albeit slightly, below 1.028 using June lake water δ18O (1.0264). Closer correspondence of apparent α18Ocell-lw, calculated using May and May–June average lake water δ18O, suggested rapid and early colonization and cellulose production by periphyton. For samples that were a mixture of cellulose and minerogenic material, mean apparent α18Ocell-lw was significantly below 1.028 for these corresponding lake water δ18O measurements, but differences were small and would potentially lead to under-estimation of cellulose-inferred lake water δ18O by only 1–2‰ in sediment stratigraphic records. Overall, strong agreement observed between the cellulose-inferred and directly measured lake water δ18O supports application of α18Ocell-lw = 1.028 ± 0.0015 and lends confidence to paleohydrological reconstructions using this method in lakes of the PAD and elsewhere.
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