In recent years, it has become apparent that carbon dioxide (CO2) emissions from inland water bodies and lakes are an important component of the global carbon cycle. Large-scale lake heterotrophy is thought to be a major driver of CO2 production and may mask other processes such as groundwater input. This study uses radon (222Rn, a natural groundwater tracer) to quantify groundwater discharge, and estimates CO2 outgassing to determine the contribution of groundwater-derived CO2 inputs into Lake Ainsworth (New South Wales, Australia). Lake Ainsworth was a source of CO2 to the atmosphere throughout the study period with outgassing rates ranging from 10.6 to 152.3 mmol m2 day−1. Annual groundwater fluxes were determined using a radon mass balance equated to about 55 ± 50 % of the total volume of water input (via direct precipitation and groundwater) into the lake. In spite of large uncertainties, groundwater seepage was a source of CO2supersaturation in Lake Ainsworth equivalent to 13 ± 25 % of total CO2 outgassing rates. Hence, groundwater discharge may need to be considered for carbon budgets of other lakes.
Perkins, AK, Santos, IR, Sadat-Noori, M, Gatland, JR & Maher, DT in 2015, 'Groundwater seepage as a driver of CO2 evasion in a coastal lake (Lake Ainsworth, NSW, Australia)', Environmental Earth Sciences, vol. 74, no. 1, pp. 779-792.
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