Diurnal and Seasonal Variation of Area-Fugitive Methane Advective Flux from an Open-Pit Mining Facility in Northern Canada Using WRF

Abstract

Greenhouse Gas (GHG) emissions pose a global climate challenge and the mining sector is a large contributor. Diurnal and seasonal variations of area-fugitive methane advective flux, released from an open-pit mine and a tailings pond, from a facility in northern Canada, were simulated in spring 2018 and winter 2019, using the Weather Research and Forecasting (WRF) model. The methane mixing ratio boundary conditions for the WRF model were obtained from the in-situ field measurements, using Los Gatos Research Ultra-Portable Greenhouse Gas Analyzers (LGRs), placed in various locations surrounding the mine pit and a tailings pond. The simulated advective flux was influenced by local and synoptic weather conditions in spring and winter, respectively. Overall, the average total advective flux in the spring was greater than that in the winter by 36% and 75%, for the mine and pond, respectively. Diurnal variations of flux were notable in the spring, characterized by low flux during thermally stable (nighttime) and high flux during thermally unstable (daytime) conditions. The model predictions of the methane mixing ratio were in reasonable agreement with limited aircraft observations (R2=0.68). The findings shed new light in understanding the area-fugitive advective flux from complex terrains and call for more rigorous observations in support of the findings.

Modeling Impacts of Mining Activity-induced Landscape Change on Local Climate

“…The GRD, as one of the key terms of energy expenditure, is in uenced by net radiation and directly related to the thermodynamic properties of the subsurface. When the GRD value is less than 0, it means that heat enters the soil, and conversely, when the GRD value is greater than 0, it means that heat is released from the soil to the surface (Elizabeth et al 2018, Nambiar et al 2020. During the daytime, the GRDs of the two experiments were -118.07 W/m2 and -118.412 W/m2, with an overall average decrease of 0.753 W/m2.…”

Machine Learning to Predict Area Fugitive Emission Fluxes of GHGs from Open-Pit Mines

“…For instance, aircraft sampling misses the first few tens of meters near the ground, the measurement of which is crucial for the accurate estimation of the emission fluxes [37]. In addition, mass balance measurements are conducted for a facility only a few times a year, while a more continuous measurement technique is ideal to capture diurnal and seasonal variations of emission fluxes [22]. Because of the large footprint of open-pit mining facilities, precise measurements of their emission fluxes are not possible.…”

“…In regards to emission flux calculations, the WRF model is furnished with a built-in passive tracer dispersion method [22,64,65], which is accompanied by other chemistry modules that can be utilized to compute the temporal and spatial evolution of the mixing ratio of tracers, and consequently, emission fluxes in the forward dispersion paradigm of modeling [66][67][68][69]. The functionality of WRF for dispersion simulations in complex terrain and the land use environment of a mine pit has been investigated comprehensively [22].…”

“…Large estimation differences of methane emission fluxes from such facilities are the result of ignoring the meteorological effects that complicate pollutant transport in complex topographies [14]. While orographic complexities confound atmospheric boundary layer (ABL) flows compared to ABL flows over flat and homogeneous terrains [15][16][17][18][19][20][21][22][23], only a handful of investigations are dedicated to ABL flows over open-pit mines [24,25], primarily due to operational, risk, access, economic, and other concerns [25,26]. Open-pit mines represent an unusual topographic feature.…”

“…Open-pit mines represent an unusual topographic feature. The meteorological patterns within and near these mines can be quite different from flat terrain [20][21][22]27,28], and understanding these patterns is important given the environmental impact of mining activities. The release of GHGs from such environments is associated with multiple steps of the resource extraction process, starting from land modification to the exportation of the mined goods [4,14].…”