CO₂ discharge from the bottom of volcanic Lake Rotomahana, New Zealand

Abstract

, CO 2 flux surveys were performed on Lake Rotomahana, New Zealand. The area has been hydrothermally active with fumaroles and sublacustrine hydrothermal activity before and since the eruption of Mt Tarawera in 1886. The total CO 2 emission from the lake calculated by sequential Gaussian simulation is 549 6 72 t d 21 . Two different mechanisms of degassing, diffusion through the water-air interface and bubbling, are distinguished using a graphical statistical approach. The carbon dioxide budget calculated for the lake confirms that the main source of CO 2 to the atmosphere is by diffusion covering 94.5% of the lake area (mean CO 2 flux 25 g m 22 d 21 ) and to a lesser extent, bubbling (mean CO 2 flux 1297 g m 22 d 21 ). Mapping of the CO 2 flux over the entire lake, including over lake floor vents detected during the survey, correlates with eruption craters formed during the 1886 eruption. These surveys also follow regional tectonic patterns present in the southeastern sector of Lake Rotomahana suggesting a deep magmatic source ( 10 km) for CO 2 and different pathways for the gas to escape to the surface. The values of d 13 C CO2 (22.88 and 22.39&) confirm the magmatic origin of CO 2 .

Intense magmatic degassing through the lake of Copahue volcano, 2013–2014

“…Gases escape from the lake surface as bubbles (convective/advective degassing) or by diffusion at the water/air interface [ Mazot and Taran , ; Caudron et al ., ]. Diffusive lake CO 2 degassing has been measured in volcanic lakes worldwide using a floating accumulation chamber and infrared sensors [ Mazot et al ., , ; Pérez et al ., ]. These studies contributed a global volcanic lake CO 2 emission of ~94 Mt/yr or 4.2% of the global volcanic CO 2 fluxes [ Pérez et al ., ].…”

High-resolution water column survey to identify active sublacustrine hydrothermal discharge zones within Lake Rotomahana, North Island, New Zealand

“…13A and 3B). B. Near-bottom turbidity, ORP, and specific conductance for like to dedicate this paper to my brother Steven Lawrence Walker (1960-2014 who was always very supportive and interested in our work. The actual values differ due to the instruments having been calibrated at different times and the length of time between the most recent calibration and our field survey.…”

“…As with temperature, pH varies with depth. Surface layer values range from 7.6 to 8, then decrease through the thermocline to average hypolimnion values of 6.5-6.7 due to high levels of dissolved CO 2 (Timperly and Brown, 1986;Mazot et al, 2014;Stucker et al, 2016). Identifying anomalous pH also relies on comparing values relative to other values at similar locations and depths rather than assigning one "background" value.…”

“…While one study measured much warmer temperatures within 1 m of the lake floor (~80 m water depth) in a limited area southwest of Patiti Island (Irwin, 1968), and discolored water and bubbles have been observed at the surface at a few near-shore locations (Nairn, 1989), the distribution of active hydrothermal venting beneath Lake Rotomahana remained unknown. A systematic survey in January 2011 using echo sounding equipment identified over 100 locations where bubble plumes could be seen rising from the lake bed (Mazot et al, 2014;de Ronde et al, 2016). Gas composition indicated a magmatic origin; however, this survey did not determine how many of these bubble plumes were accompanied by warm water.…”

CO2 Flux from Volcanic Lakes in the Western Group of the Azores Archipelago (Portugal)

“…Volcanic gases, composed mainly of water vapor and varied amounts of carbon compounds, sulfur, halogens, and several minor constituents, are the main drivers of volcanic water composition [13][14][15][16].Natural CO 2 can have several origins in that it can originate from the mantle, from carbonate rocks existing in the crust, or as the result of biogenic activity [17]. Over the last decade, studies of diffuse degassing CO 2 have been conducted in volcanic lakes all over the world and in other types of water bodies, and such studies have provided important information about their spatial and temporal flux variations and have been shown to be a relevant tool for mapping hidden active faults and/or for active volcano monitoring [10,[18][19][20][21][22][23][24][25]. In addition, these studies have contributed to improving the Earth's carbon budget (e.g., [9,24,[26][27][28][29][30][31][32][33][34][35][36]).…”