Gas transfer velocities in small forested ponds

Abstract

Inland waters actively exchange gases with the atmosphere, and the gas exchange rate informs system biogeochemistry, ecology, and global carbon budgets. Gas exchange in medium‐ to large‐sized lakes is largely regulated by wind; yet less is known about processes regulating gas transfer in small ponds where wind speeds are low. In this study, we determined the gas transfer velocity, k600, in four small (<250 m2) ponds by using a propane (C3H8) gas injection. When estimated across 12 h periods, the average k600 ranged from 0.19 to 0.72 m d−1 across the ponds. We also estimated k600 at 2 to 3 h intervals during the day and evaluated the relationship with environmental conditions. The average daytime k600 ranged from 0.33 to 1.83 m d−1 across the ponds and was best predicted by wind speed and air or air‐water temperature; however, the explanatory power was weak (R2 < 0.27) with high variability within and among ponds. To compare our results to larger water bodies, we compiled direct measurements of k600 from 67 ponds and lakes worldwide. Our k600 estimates were within the range of estimates for other small ponds, and variability in k600 increased with lake size. However, the majority of studies were conducted on medium‐sized lakes (0.01 to 1 km2), leaving small ponds and large lakes understudied. Overall, this study adds four small ponds to the existing body of research on gas transfer velocities from inland waters and highlights uncertainty in k600, with implications for calculating metabolism and carbon emissions in inland waters.

Turbulence in a small arctic pond

“…Diel variations in the stability of the atmosphere and within ponds and lakes will contribute to between site differences. For example, 12 h k 600 from ponds in temperate regions tend to be lower than we compute (Holgerson et al ). For winds of ∼ 2 m s −1 , Clark et al () obtained average values ranging from 0.5 cm h −1 to 3 cm h −1 at a larger pond.…”

A simple and cost-efficient automated floating chamber for continuous measurements of carbon dioxide gas flux on lakes

“…3, d) within the range of previously published values (Torgersen and Branco, 2008;Holgerson et al, 2017; and similar to values found in the same system using ordinary floating chambers (not shown). Because 25 the ventilation of the chamber headspace occurs through dilution with atmospheric air, CO 2 concentrations do not always reach the ambient atmospheric values (Fig.…”

Lakes as nitrous oxide sources in the boreal landscape

“…Total annual N 2 O flux from Finnish lakes (total LA 32,663 km 2 ) was estimated as 0.6–0.8 Gg N 2 O‐N/year, based on the areas of the lake size distribution by Raatikainen and Kuusisto () and the evasion estimates for the different lake size classes (Figure ). Both Holgerson et al () and Heiskanen et al () approaches resulted in an estimate of 0.6 Gg N 2 O‐N/year for Finnish lakes, when the median N 2 O evasion estimates of different lake size classes were multiplied with the respective lake surface area distribution. The Vachon and Prairie () approach resulted in a little bit larger estimate of 0.8 Gg N 2 O‐N/year (Table ; Tables S1 and S2).…”

“…where F gas is the lake-atmosphere flux of N 2 O, kN 2 O is the gas transfer velocity (m/day), C gas is the concentration of the gas in the surface water (μmol/L), C eq is the concentration of the gas (μmol/L) in equilibrium with the atmosphere. Since the data behind measured gas transfer coefficients (k values) are limited and the relationship between lake size and k values varies, we used three approaches to estimate lake-atmosphere gas exchange (Heiskanen et al, 2014;Holgerson, Farr, & Raymond, 2017;Vachon & Prairie, 2013). We calculated the gas fluxes for the 94 lakes that had N 2 O concentrations measured in all four seasons.…”

“…Also, our data demonstrated Area (km 2 ) 32,663 a 1,422,448 b a Lake area distribution (Raatikainen and Kuusisto, 1990 TA B L E 5 Annual N 2 O flux estimates (mg N 2 O-N m −2 year −1 ) by lake type based on all lakes that were sampled at all four seasons (n = 94; the water quality data were missing from two lakes and the lake type could not be assigned): annual fluxes for the randomly selected lakes (n = 71) and for the subset of Eutrophic lakes with the highest total P concentrations (n = 23). The annual fluxes (7 month ice-free season) consist of fluxes at the thaw (0.5 months), in spring (1.5 months), in summer (3 months), and in autumn (2 months) calculated using k values by Holgerson et al (2017). Two small humic lakes with fluxes of 863 and 22,085 mg N 2 O-N m −2 year −1 were excluded as outliers driver for CO 2 in our data, with similar explanation power, 78%, of the variation across all lakes and depths (Kortelainen et al, 2006).…”