High sulphur dioxide deposition velocities measured with the flux/gradient technique in a boreal forest in the Alberta oil sands region

Gordon, Mark; Blanchard, Dane; Jiang, Timothy; Makar, Paul A.; Staebler, R. M.; Aherne, Julian; Mihele, C.; Zhang, Xuanyi

doi:10.5194/acp-2022-668

Cited by 3 publications

(7 citation statements)

References 17 publications

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“…Although the deposition velocity resulting in the best fit to observed O3 profiles is lower here than deposition velocities reported in boreal forests such as Rannik et al (2012), this could be due to the sparser forest and lower LAI at this location relative to those locations. This lower deposition velocity for ozone contrasts with the higher deposition velocity for SO 2 for this region as described in both Gordon et al (2022) and Hayden et al (2022), suggesting that the increased SO 2 deposition could be related to a chemical process such as surface acidity that does not affect ozone deposition.…”

Section: Discussionmentioning

confidence: 60%

“…No ozone measurements were made during this field study, but SO2 measurements (43i, Thermo Scientific and AF22e, Envea) at ground level and a height of 30 m and sizeresolved sub-micron aerosol measurements (UHSAS, DMT) helped to further identify wind sectors bringing polluted air to the site. The SO 2 and aerosols measurements are discussed in our companion papers Gordon et al (2022) and Jiang et al (2022) respectively.…”

Section: Site Location and Instrumentationmentioning

confidence: 99%

“…Gradient and mixing ratio measurements are compared with a 1D canopy model with various deposition schemes using a "big leaf" approach, which assumes a deposition flux at the lowest model layer. This paper is a companion paper to Jiang et al (2022) and Gordon et al (2022) which respectively investigate aerosol and SO2 deposition at this site.…”

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confidence: 99%

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Ozone in the boreal forest in the Alberta oil sands region

Zhang

Gordon²,

Makar³

et al. 2023

Preprint

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Abstract. Measurements of ozone were made using an instrumented tower and a tethersonde located in a forested region surrounded by oil sands production facilities in the Athabasca Oil Sands Region (AOSR). Our observations and modelling show that the concentration of ozone was modified by vertical mixing, photochemical reactions, and surface deposition. Measurements on the tower demonstrated that when winds are from the direction of anthropogenic emissions from oil sand extraction and processing facilities, the ozone mixing ratio in the forest is as much as 10 ppb lower than when winds are from the direction of undisturbed forest. This finding is supported by previous studies which suggest that surplus NOx from oil sands emissions results in ambient ozone titration. Gradients of ozone mixing ratio with height were observed using instruments on a tethered balloon (up to a height of 300 m) as well as a pulley system and 2-point gradients within the canopy. Strong gradients (ozone increasing with height between 0.2 and 0.4 ppb m-1) were measured in the canopy overnight, while daytime gradients were weaker and highly variable. A 1D canopy model was used to simulate the afternoon in-canopy gradient with reduced mixing overnight (suggesting high stability within the canopy), and an ozone deposition velocity of 0.2 cm s-1. Sensitivity simulations using the model suggest the local NO concentration profile and coefficients of vertical diffusivity have a significant influence on the O3 concentrations and profiles in the region.

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Section: Discussionmentioning

confidence: 60%

Section: Site Location and Instrumentationmentioning

confidence: 99%

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Ozone in the boreal forest in the Alberta oil sands region

Zhang

Gordon²,

Makar³

et al. 2023

Preprint

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“…One approach is to parameterize K based on a measured two-point wind gradient and momentum flux (You et al, 2021, andGordon et al, 2022). Here Prandtl's mixing length model is adjusted for stability following Garratt (1994) to give…”

Section: Canopy Decoupling and Gradientsmentioning

confidence: 99%

“…The three primary goals of this study were to determine the sources of specific aerosol size distributions from oil sands operations at ground level, to determine the size-resolved deposition rate of anthropogenic source aerosols into forests, and to study the effect the forest has on the vertical mixing of aerosols. This paper is a companion paper to Gordon et al (2022) and Zhang et al (2023), which respectively investigate SO 2 and ozone deposition at this site.…”

Section: Introductionmentioning

confidence: 99%

Aerosol deposition to the boreal forest in the vicinity of the Alberta Oil Sands

et al. 2023

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Abstract. Measurements of size-resolved aerosol concentration and fluxes were made in a forest in the Athabasca Oil Sands Region (AOSR) of Alberta, Canada, in August 2021 with the aim of investigating (a) particle size distributions from different sources, (b) size-resolved particle deposition velocities, and (c) the rate of vertical mixing in the canopy. Particle size distributions were attributed to different sources determined by wind direction. Air mixed with smokestack plumes from oil sands processing facilities had higher number concentrations with peak number at diameters near 70 nm. Aerosols from the direction of open-pit mine faces showed number concentration peaks near 150 nm and volume distribution peaks near 250 nm (with secondary peaks near 600 nm). Size-resolved deposition fluxes were calculated which show good agreement with previous measurements and a recent parameterization. There is a minimum deposition velocity of vd=0.02 cm s−1 for particles of 80 nm diameter; however, there is a large amount of variation in the measurements, and this value is not significantly different from zero in the 68 % confidence interval. Finally, gradient measurements of aerosol particles (with diameters <1 µm) demonstrated nighttime decoupling of air within and above the forest canopy, with median lag times at night of up to 40 min and lag times between 2 and 5 min during the day. Aerosol mass fluxes (diameters <1 µm) determined using flux–gradient methods (with different diffusion parameterizations) underestimate the flux magnitude relative to eddy covariance flux measurements when averaged over the nearly 1-month measurement period. However, there is significant uncertainty in the averages determined using the flux–gradient method.

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High sulfur dioxide deposition velocities measured with the flux–gradient technique in a boreal forest in the Alberta Oil Sands Region

Gordon¹,

Blanchard²,

Jiang³

et al. 2023

Atmos. Chem. Phys.

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Abstract. The emission of SO2 from the Athabasca Oil Sands Region (AOSR) has been shown to impact the surrounding forest area. Recent studies using aircraft-based measurements have demonstrated that deposition of SO2 to the forest is at a rate many times higher than model estimates. Here we use the flux–gradient method to estimate SO2 deposition rates at two tower sites in the boreal forest downwind of AOSR SO2 emissions. We use both continuous and passive sampler measurements and compare the two techniques. The measurements infer SO2 deposition velocities ranging from 2.1–5.9 cm s−1 (when corrections are applied). There are uncertainties associated with the passive sampler flux–gradient analysis, primarily due to an assumed Schmidt number, a required assumption of independent variables, and potential wind effects. We estimate the total uncertainty as ± 2 cm s−1. Accounting for these uncertainties, the range of measurements is approximately double the previous aircraft-based measurements (1.2–3.4 cm s−1) and more than 10 times higher than model estimates for the same measurement periods (0.1–0.6 cm s−1), suggesting that SO2 in the AOSR has a much shorter lifetime in the atmosphere than is currently predicted by models.

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High sulphur dioxide deposition velocities measured with the flux/gradient technique in a boreal forest in the Alberta oil sands region

Cited by 3 publications

References 17 publications

Ozone in the boreal forest in the Alberta oil sands region

Ozone in the boreal forest in the Alberta oil sands region

Aerosol deposition to the boreal forest in the vicinity of the Alberta Oil Sands

High sulfur dioxide deposition velocities measured with the flux–gradient technique in a boreal forest in the Alberta Oil Sands Region

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