Eric Duchemin

Bio: Eric Duchemin is an academic researcher from Université du Québec à Montréal. The author has contributed to research in topics: Greenhouse gas & Urban agriculture. The author has an hindex of 13, co-authored 23 publications receiving 1451 citations.

Production of the greenhouse gases CH4 and CO2 by hydroelectric reservoirs of the boreal region

Abstract: The emission fluxes and the distribution of dissolved methane (CH4) and carbon dioxide (CO2) were determined for 11 sampling stations in two hydroelectric reservoirs (flooded since 1978 and 1993) located in the James Bay territory of northern Quebec. The measured benthic fluxes for the two greenhouse gases were found to be either higher or similar to those determined at the water-air interface during the ice-free sampling periods. For the 2 year duration of the study, emission fluxes of CH4 to the atmosphere generally varied between 5 and 10 mg m−2 d−1, while those for CO2 ranged from 500 to 1100 mg m−2 d−1. Furthermore, through the use of static chambers at the water-air interface, we determined that the emission fluxes for the gases are controlled by molecular diffusion. Our calculated fluxes have been separated into two groups: (1) regular emission fluxes and (2) above-average emission fluxes. The first type comprises the majority of fluxes measured during the sampling periods (i.e., 88% for CH4 and 87% for CO2). The second group reflects unusual sampling conditions (e.g., strong winds, water column depths of less than 1 m, or flooded peatland mats floating at the surface). Although data for this group are limited, our preliminary results suggest that they may be an important component in an atmospheric emissions budget for large reservoirs. Concentration profiles for CH4 and CO2 dissolved in the water column clearly show that oxidation and/or horizontal advection of these gases are controlling factors in their subsequent release to the atmosphere. Most of the CH4 is oxidized within the first 25 cm above the flooded soil-water interface. Consequently, neither benthic emissions of CH4 and CO2 nor the type of flooded soil appear to control atmospheric emissions of these gases from hydroelectric reservoirs.

Greenhouse gas emissions from reservoirs of the western United States

Abstract: = 0.81; p < 0.0001). All other correlations between GHG diffusivefluxes and independent variables tested were weak and/or not significant. Finally,while attempting to resolve the spatial variability in diffusive fluxes, we were able tocluster reservoirs neither according to geological nor ecological criteria.

Comparison of Static Chamber and Thin Boundary Layer Equation Methods for Measuring Greenhouse Gas Emissions from Large Water Bodies

Abstract: The emission fluxes of CH4 and CO2 at the water−air interface of two large reservoirs were evaluated using two methods: (1) static chambers (STAT) and (2) the boundary layer equation (BLE). Such a comparison was rendered necessary in order to verify the information yielded by various automated measurement devices recently developed and based on BLE flux measurement principles. Our study shows that the BLE method underestimates the actual fluxes of CO2 and CH4. The variation observed between the two measurement techniques may be explained by different errors or biases inherent in the methods and therefore not a reflection of the true emissions. Variability observed in both data sets impose cautiousness on any drastic conclusion about this comparison, but it appears that the BLE method underestimates the CO2 and CH4 emission fluxes from large water bodies. Additionally, compared to the STAT technique, the BLE method overestimates the wind effect in deep areas. For shallow zones, however, the use of the BLE...

Is food a motivation for urban gardeners? Multifunctionality and the relative importance of the food function in urban collective gardens of Paris and Montreal

Abstract: In the cities of industrialized countries, the sudden keen interest in urban agriculture has resulted, inter alia ,i n the growth of the number and diversity of urban collective gar- dens. While the multifunctionality of collective gardens is well known, individual gardeners' motivations have still not been thoroughly investigated. The aim of this article is to explore the role, for the gardeners, of the food function as one of the functions of gardens, and to establish whether and how this function is a motivating factor for them. We draw on a set of data from semi-structured interviews with 39 gardeners in 12 collective gardens in Paris and Montreal, as well as from a survey on 98 gardeners and from field observations of the gardeners' practices. In the first part we present the nature and diversity of garden produce, and the gardeners' assessment thereof. In the second part we describe the seven other func- tions mentioned by the gardeners, which enables us to situate the food function in relation to them. We conclude that the food function is the most significant function of the gardens, and discuss the implications for practitioners and policy makers.

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget

Abstract: Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y−1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y−1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described.

Principles of Terrestrial Ecosystem Ecology

Abstract: I. CONTEXT * The Ecosystem Concept * Earth's Climate System * Geology and Soils * II. MECHANISMS * Terrestrial Water and Energy Balance * Carbon Input to Terrestrial Ecosystems * Terrestrial Production Processes * Terrestrial Decomposition * Terrestrial Plant Nutrient Use * Terrestrial Nutrient Cycling * Aquatic Carbon and Nutrient Cycling * Trophic Dynamics * Community Effects on Ecosystem Processes * III. PATTERNS * Temporal Dynamics * Landscape Heterogeneity and Ecosystem Dynamics * IV. INTEGRATION * Global Biogeochemical Cycles * Managing and Sustaining Ecosystem * Abbreviations * Glossary * References

Fragmentation and flow regulation of the world's large river systems

Abstract: A global overview of dam-based impacts on large river systems shows that over half (172 out of 292) are affected by dams, including the eight most biogeographically diverse. Dam-impacted catchments experience higher irrigation pressure and about 25 times more economic activity per unit of water than do unaffected catchments. In view of projected changes in climate and water resource use, these findings can be used to identify ecological risks associated with further impacts on large river systems.

Lakes and reservoirs as regulators of carbon cycling and climate

Abstract: We explore the role of lakes in carbon cycling and global climate, examine the mechanisms influencing carbon pools and transformations in lakes, and discuss how the metabolism of carbon in the inland waters is likely to change in response to climate. Furthermore, we project changes as global climate change in the abundance and spatial distribution of lakes in the biosphere, and we revise the estimate for the global extent of carbon transformation in inland waters. This synthesis demonstrates that the global annual emissions of carbon dioxide from inland waters to the atmosphere are similar in magnitude to the carbon dioxide uptake by the oceans and that the global burial of organic carbon in inland water sediments exceeds organic carbon sequestration on the ocean floor. The role of inland waters in global carbon cycling and climate forcing may be changed by human activities, including construction of impoundments, which accumulate large amounts of carbon in sediments and emit large amounts of methane to the atmosphere. Methane emissions are also expected from lakes on melting permafrost. The synthesis presented here indicates that (1) inland waters constitute a significant component of the global carbon cycle, (2) their contribution to this cycle has significantly changed as a result of human activities, and (3) they will continue to change in response to future climate change causing decreased as well as increased abundance of lakes as well as increases in the number of aquatic impoundments.