Chris Thomas ParsonsEnvironment and Climate Change Canada · Watershed Hydrology and Ecology Research Division
Chris Thomas Parsons
Ph.D Biogeochemistry
About
42
Publications
11,576
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Introduction
My research interests are shaped by the impacts that human activities have on microbial, geochemical and hydrological processes influencing water quality and the health of freshwater ecosystems. I focus on coupled biogeochemical cycles and the speciation and transport of redox-sensitive elements (e.g. C, N, P, Si, Fe, Mn, S, As, Se, U, Cr). My ultimate goal as a scientist is to improve predictive understanding of biogeochemical processes to address societally important environmental problems.
Additional affiliations
September 2019 - present
Position
- Researcher
Description
- Stream and watershed biogeochemist within the Watershed Hydrology and Ecology Research Division (WHERD).
June 2017 - present
June 2015 - May 2017
Education
September 2007 - October 2011
September 2003 - July 2007
Publications
Publications (42)
Anthropogenic nutrient enrichment has caused phosphorus (P) accumulation in many freshwater sediments, raising concerns that internal loading from legacy P may delay the recovery of aquatic ecosystems suffering from eutrophication. Benthic recycling of P strongly depends on the redox regime within surficial sediment. In many shallow environments, r...
Many physical, chemical, and biological processes in freshwater ecosystems mobilize the nutrient phosphorus (P) from sediments, which in turn may contribute to the formation of harmful algal blooms. Here, we critically reviewed internal P loading in Canadian fresh waters to understand the geographic patterns and environmental drivers of this import...
Extensive efforts are underway to reduce phosphorus (P) export from the Lake Erie watershed. On the Canadian side, the Thames River is the largest tributary source of P to Lake Erie’s western basin. However, the role of dams in retaining and modifying riverine P loading to the lake has not been comprehensively evaluated. We assessed whether Fanshaw...
Management strategies aimed at reducing nutrient enrichment of surface waters may be hampered by nutrient legacies that have accumulated in the landscape. Here, we apply the Net Anthropogenic Phosphorus Input (NAPI) model to reconstruct the historical phosphorus (P) input trajectories for the province of Ontario, which encompasses the Canadian port...
An enhanced understanding of nonpoint source (NPS) nutrient export to the lower Great Lakes is needed to inform land use and land management decisions within southern Ontario. However, this understanding is limited by a lack of long-term, temporally-intensive monitoring. To address this knowledge gap, we revisit six agriculturally-dominated subwate...
Lake Wilcox (LW), a shallow kettle lake located in southern Ontario, has experienced multiple phases of land use change associated with human settlement and residential development in its watershed since the early 1900s. Urban growth has coincided with water quality deterioration, including the occurrence of algal blooms and depletion of dissolved...
Release of sorbed phosphate from ferric iron oxyhydroxides can contribute to excessive algal growth in surface water bodies. Dissolved silicate has been hypothesized to facilitate phosphate desorption by competing for mineral surface sites. Here, we conducted phosphate and silicate adsorption experiments with goethite under a wide pH range (3–11),...
Previous work has shown that about 10% of total clay-bound Fe(III) in unaltered nontronite NAu-1 is bioreducible, although it remains unclear how much of the bioreducible Fe pool persists after repeated oscillations between anoxic and oxic conditions. Here, we report on results from an experiment where we monitored the abundance of bioreducible Fe(...
Abstract The degradation and loss of ecologically important wetlands has been a topical issue in the Great Lakes region, where 60–80% of the coastal wetlands have been lost since the 1800s. The present modeling study aims to guide the restoration efforts in Cootes Paradise marsh, one of the most degraded shallow wetlands in Southern Ontario. We use...
Fen construction has recently been tested in the Athabasca Oil Sands Region, Alberta, Canada in an effort to return peatlands to the post-mining landscape. Understanding the drivers of organic matter decomposition in constructed fens will improve our capacity to evaluate the return of ecosystem function while also helping to inform management activ...
Eutrophication of freshwaters is already a problem in many regions globally and will probably worsen as human populations grow and consume more resources. The ability of researchers and governments to anticipate, mitigate, and restore eutrophic freshwaters in a cohesive, integrated manner suffers from key uncertainties in our understanding of the w...
The chemical and physical characteristics of humic acids (HA) may differ depending on their
source, and ideally the extraction method should not modify the characteristics of HA.
Hydrofluoric acid (HF) is often used in HA extraction methods to remove inorganic substances that are often present in the sample in addition to the organic molecules of i...
We examined the fractions of particulate phosphorus (PP) in the lower reaches of the Grand River, Canada, to test the hypothesis that the river is a source of both particulate-bound orthophosphate and labile species of PP. At the mouth of the Grand River, the proportion of particulate organic P (POP) was, on average, 57.7% of total PP, which was si...
Redox electrodes are commonly used to measure redox potentials (EH) of natural waters. The recorded EH values are usually interpreted in terms of the dominant inorganic redox couples. To further advance the interpretation of measured EH distributions along temporal and spatial redox gradients, we performed a series of reactor experiments in which o...
While a variety of physicochemical and biogeochemical factors have been involved to explain measured Eh values, the role of microorganisms remains comparatively understudied and uncertain. A set of separate abiotic experiments on the photoreduction of synthetic flavins (LMC, RF, FMN, and FAD, Sigma Aldrich) indicated that measured Eh values are buf...
![Fig. 2. Time series of modelled (line) and measured [As] (diamond),...](profile/Ekaterina-Markelova/publication/321846157/figure/fig3/AS:646100918759434@1531053871801/Time-series-of-modelled-line-and-measured-As-diamond-Sb-circle-and-Cr_Q320.jpg)
Argillaceous geological formations are considered promising repositories for waste containing inorganic con- taminants. However, the sequestration capacity of an argillaceous natural barrier may change as a result of dynamic environmental conditions, in particular changes in redox state. Here, we imposed redox cycles to ar- gillaceous suspensions a...
Overburden and tailings materials from oil sands production were used as construction materials as part of a novel attempt to create a self-sustaining, peat accumulating fen-upland ecosystem. To evaluate the potential for elemental release from the construction materials, total elemental concentrations in the tailings sand, petroleum coke and peat...
Anthropogenic nutrient enrichment has caused phosphorus (P) accumulation in many freshwater sediments, raising concerns that internal loading from legacy P may delay the recovery of aquatic ecosystems suffering from eutrophication. Benthic recycling of P strongly depends on the redox regime at the sediment-water interface (SWI) that, in many shallo...
More than 70,000 large dams have been built worldwide. With growing water stress and demand for energy, this number will continue to increase in the foreseeable future. Damming greatly modifies the ecological functioning of river systems. In particular, dam reservoirs sequester nutrient elements and, hence, reduce downstream transfer of nutrients t...
We observed a contrast in contaminant behaviour between soil and argillaceous materials. We ascribe this to the presence of Fe-and Mn-oxy(hydr)oxides in soil, which can act both as sorbents and as catalysts for oxidation, causing oscillating im/mobilization of As and Sb under oxic/anoxic conditions. Although, re-oxidation of reduced Cr was not obse...
Immobilization mechanisms of N(V), Cr(VI), As(V) and Sb(V) via sorption to the mineral matrix and microbially-mediated reduction reactions in argillaceous substrate were studied under controlled abiotic vs biotic and oxic vs anoxic conditions. The results indicate that sorption is less efficient in removing N, Cr, As and Sb than reductive transform...
There is an up-coming global surge in dam construction. River damming impacts nutrient cycling in watersheds through transformation and retention in the reservoirs. The bioavailability of silicon (Si) relative to nitrogen (N) and phosphorus (P) concentrations, in combination with light environment, controls diatom growth and therefore influences ph...
Many geochemical systems fluctuate regularly from oxic to anoxic conditions (flooded soils and nuclear waste surface repositories, for instance). In these conditions many inorganic contaminants including Sb, Se, Cr, As, and U are highly sensitive to changes in redox conditions. These oscillations may result in changes to their speciation, toxicity,...
Arsenic contamination of floodplain soils is extensive and additional fresh arsenic inputs to the pedosphere from human activities are ongoing. We investigate the cumulative effects of repetitive soil redox cycles, which occur naturally during flooding and draining, on a calcareous fluvisol, the native microbial community and arsenic mobility follo...
Recent technological improvements have led to the widespread adoption of field portable energy dispersive X-ray fluorescence (FP-XRF) by governmental agencies, environmental consultancies and research institutions. FP-XRF units often include analysis modes specifically designed for the quantification of trace elements in soils. Using these modes, X...
Arsenic is a toxic and carcinogenic metalloid, ubiquitous in the pedosphere and highly sensitive tofluctuations in soil redox conditions which dramatically influence both its toxicity and mobility. We reviewthe global biogeochemical cycle of arsenic in light of increasing resource usage and re-evaluate theimportance of anthropogenic and geogenic ar...
Projects
Projects (2)
1) Quantify effects of pulse nutrient loadings on algal community diversity and biomass and establish the environmental factors (e.g., hydrology) regulating the magnitude and nature of community change
caused by pulse nutrient loadings; and
2) Determine if biomass and diversity changes in algal communities have extended effects on food web structure and ecosystem processes (e.g., nutrient uptake, benthic metabolism)
The objectives of AquaTRAIN are to provide early stage researchers with
(a) analytical, geochemical, microbiological and environmental management training necessary for the technical implementation of EU policies on groundwater and soil protection;
(b) exposure to innovative developments in our understanding of
(i) the biogeochemical processes controlling the cycling of chemicals in groundwater/soil systems;
(ii) novel protection and remediation technologies;
(iii) the biochemistry of chemical uptake in humans and in the food chain; and
(iv) human health and environmental impacts arising from trace concentrations of chemicals in ground waters
