Monitoring Of CO2 Fluxes Research Articles

All-fiber multifunction differential absorption CO2 lidar integrating single-photon and coherent detection

This study demonstrates a differential absorption lidar (DIAL) for CO2 that integrates both single-photon direct detection and coherent detection. Based on all-fiber 1572 nm wavelength devices, this compact lidar achieves detection of CO2 concentration, wind field, and single photon aerosol backscattering signal. First, by comparing DIAL with VAISALA-GMP343, the concentration deviation between the two devices is less than 5 ppm, proving the accuracy of the DIAL. Second, through the scanning detection experiment in Chaohu Lake, Hefei, not only the CO2 concentration between single-photon detection and coherent detection but also the wind field was obtained, proving the multifunctionality and stability of the DIAL. Benefiting from the advantages of combined the two detection methods, single photon detection offers 3-km CO2 and aerosol backscattering signals; coherent detection offers a 360-m shorter blind zone and wind field. This DIAL can achieve monitoring of CO2 flux and sudden emissions, which can effectively compensate for the shortages of in-situ sensors and spaceborne systems.

Experimental Preliminary Measurements of CO2 Flux for Exploring Hidden Geothermal Systems

Geothermal energy is a promising renewable energy source, and to enhance its use, identifying Hidden Geothermal Systems (HGS) without thermal manifestations on the surface is a challenging subject. Soil CO2 flux monitoring has become an effective method for detecting HGS, different from traditional methods that target thermal indicators. Expensive portable CO2 gas analyzers are commonly used for this purpose, but their high cost prevents wide applications. Thus, this study tries to design and test a cost-effective solution for measuring CO2 flux while keeping high accuracy and reliability of measured data. The method incorporates a self-made accumulation chamber connected to a relatively inexpensive CO2 portable meter, the GasLab Pro Carbon Dioxide Sampling Data Logger CM-1000. The device uses non-dispersive infrared (NDIR) to detect CO2 and is equipped with a data logger for continuous monitoring. The CO2 flux measurement is performed using the accumulation chamber method. The reliability of this tool for detecting CO2 flux is evaluated, and the experimental results are verified by comparing them with an intelligent gas flow meter, the Shimadzu Intelligent Flow Meter DFM-1000. The tool is tested in various conditions, with CO2 flux values ranging from 3.30 to 1013.02 g m-2 day-1, proving capable of measuring CO2 flux up to 1000 g m-2 day-1. Field tests were conducted at 60 sites to evaluate the tool’s performance. The results suggest that the lower measurement limit of the tool is approximately 0.1 g m-2 day-1. Overall, the cost-effective solution holds promise as a reliable tool for investigating HGS, with potential applications in other environments with similar or higher CO2 flux rates. In addition, conducting further comparison studies with a common sophisticated automatic flux tool such as LI-COR 850 can help improve the accuracy and reliability of the tool.

A dataset of biomass of the alpine shrub meadow (2003–2020) and the alpine Kobresia humilis (2002–2020) observed at the CO2 flux monitoring station in Haibei, China

The Qinghai-Tibet Plateau (QTP) is a hotspot and sensitive region affected by global climate change. The alpine shrub and alpine Kobresia humilis meadow are the primary types of alpine meadow found in this area, which play an important role in the sustainable development of the QTP and even the global alpine meadow ecosystem. Biomass, as a direct index reflecting the production function of grassland ecosystem, can be used to effectively study the relationship between grassland ecosystem function and other influencing factors. The precise measurement and assessment of the biomass of the alpine shrub and alpine Kobresia humilis meadow are crucial elements for gaining a scientific understanding of the ecological functions of the alpine meadow on the QTP. The National Field Scientific Observation and Research Station of Alpine Grassland Ecosystem located in Haibei Prefecture, Qinghai Province (Haibei Station) has been conducting scientific monitoring of the biomass of alpine Potentilla fruticosa shrub and alpine Kobresia humilis meadow respectively since 2002 and 2003. Haibei Station has continuously accumulated the original data of these two ecosystems for 17 and 18 years respectively. In order to precisely evaluate the carbon sink potential of the alpine shrub and alpine Kobresia humilis meadow ecosystems in the QTP and even the global, and accurately predict the long-term response of the ecosystem to climate change, we published the biomass data of the alpine shrub (2003-2020) and alpine Kobresia humilis meadow (2002-2020) in the Haibei Flux Monitoring Station. This dataset includes aboveground biomass and underground biomass of the alpine shrub and alpine Kobresia humilis meadow. It can provide ground observation data support for scientific cognition, remote sensing inversion and model verification of the spatial and temporal dynamics of ecosystem biomass in alpine meadows, and contribute to the healthy and sustainable development of alpine meadows.

Seasonal variations and driving mechanisms of CO2 fluxes over a winter-wheat and summer-maize rotation cropland in the North China plain

Characterization of crop CO2 fluxes in different growing periods and their corresponding responses to abiotic and biotic factors is essential for the adaption of cropland ecosystem carbon balance to future climate change and management practices. In this study, based on long-term (2003–2018) monitoring of CO2 fluxes, meteorological data and leaf area index (LAI) of a winter wheat-summer maize rotation cropland in the North China Plain, the relationship between CO2 fluxes of different growing periods and the driving factors (i.e., abiotic and biotic factors) was explored to identify the important affecting factors. The Random Forest (RF) algorithm revealed that LAI was the most important driving factor of CO2 fluxes in the wheat season, except for WGPW (from sowing to maturity). Net ecosystem productivity (NEP) had significant positive relationships with LAI, photosynthetically active radiation (PAR) and soil water content (SWC) in four different growing periods. Air temperature (Ta) was positively correlated with ecosystem respiration (ER), and LAI and PAR were positively correlated with gross primary productivity (GPP). In the maize season, the RF algorithm revealed that LAI, PAR and SWC were important drivers of CO2 fluxes. NEP and GPP had significant negative relationships with precipitation (PPT) in RGPM (from tasseling to maturity) and WGPM (from sowing to maturity). Ta was positively correlated with ER, and SWC was positively correlated with NEP and GPP except for VGP2M (from jointing to tasseling). For annual fluxes, the interannual variability (IAV) of NEP, ER and GPP were mainly attributed to IAV of the maximum daily NEP (NEPmax), maximum daily ER (ERmax) and maximum daily GPP (GPPmax), respectively. Our findings provide deep insight into CO2 flux characteristics of wheat-maize rotation systems in different growing periods and their influencing mechanisms, which are crucial for predicting the carbon cycle of cropland ecosystems under climate change.

Detection and attribution of an anomaly in terrestrial photosynthesis in Europe during the COVID-19 lockdown

Carbon dioxide (CO2) uptake by plant photosynthesis, referred to as gross primary production (GPP) at the ecosystem level, is sensitive to environmental factors, including pollutant exposure, pollutant uptake, and changes in the scattering of solar shortwave irradiance (SWin) − the energy source for photosynthesis. The 2020 spring lockdown due to COVID-19 resulted in improved air quality and atmospheric transparency, providing a unique opportunity to assess the impact of air pollutants on terrestrial ecosystem functioning. However, detecting these effects can be challenging as GPP is influenced by other meteorological drivers and management practices. Based on data collected from 44 European ecosystem-scale CO2 flux monitoring stations, we observed significant changes in spring GPP at 34 sites during 2020 compared to 2015–2019. Among these, 14 sites showed an increase in GPP associated with higher SWin, 10 sites had lower GPP linked to atmospheric and soil dryness, and seven sites were subjected to management practices. The remaining three sites exhibited varying dynamics, with one experiencing colder and rainier weather resulting in lower GPP, and two showing higher GPP associated with earlier spring melts. Analysis using the regional atmospheric chemical transport model (LOTOS-EUROS) indicated that the ozone (O3) concentration remained relatively unchanged at the research sites, making it unlikely that O3 exposure was the dominant factor driving the primary production anomaly. In contrast, SWin increased by 9.4 % at 36 sites, suggesting enhanced GPP possibly due to reduced aerosol optical depth and cloudiness. Our findings indicate that air pollution and cloudiness may weaken the terrestrial carbon sink by up to 16 %. Accurate and continuous ground-based observations are crucial for detecting and attributing subtle changes in terrestrial ecosystem functioning in response to environmental and anthropogenic drivers.

A novel infrastructure for the continuous monitoring of soil CO2 emissions: a case study at the alto Tiberina near fault observatory in Italy

Static and dynamic stress, along with earthquakes, can trigger the emission and migration of crustal fluids, as frequently observed on the surface and within the upper crust of tectonically active areas such as the northern Apennines of Italy. To investigate the origin of these fluids and their interconnection with the seismogenic process, we complemented The Alto Tiberina Near Fault Observatory (TABOO-NFO), a multidisciplinary monitoring infrastructure composed of a dense array of seismic, geodetic, strain, and radon sensors, with a proper geochemical network grounded on four soil CO2 flux monitoring stations and weather sensors, placed near the main vents of the superficial manifestations. The TABOO-NFO is a state-of-the-art monitoring infrastructure, which allows for studying various geophysical parameters connected to the deformation processes active along a crustal fault system dominated by the Alto Tiberina fault (ATF), which is a 60 km long normal fault dipping at a low angle (<15°–20°). The region is favourable for conducting geochemical studies, as it is characterised by the presence of over-pressurised fluids trapped at certain depths and superficial manifestations associated with the emission of large quantities of fluids. After describing the theoretical framework and the technological aspects based on which we developed the geochemical monitoring network, we described the data recorded in the first months. Over the studied period, the results showed that soil CO2 flux was primarily influenced by environmental parameters, and that the selected sites received a regular supply of deep-origin CO2.

Unique characteristics of ecosystem CO2 exchange in Sundarban mangrove forest and their relationship with environmental factors

Sundarban mangroves, known to be the largest single block of tidal halophytic mangrove forest globally, covers a significant portion of the world's mangroves and contributes substantially to the global mangrove carbon budget. Nevertheless, there is still a lack of long-term continuous monitoring of CO2 fluxes over this crucial ecosystem and their dynamics in response to climatic variations. This study presents the carbon balance and seasonal dynamics of this oldest and undisturbed mangrove ecosystem using quasi-continuous eddy covariance measurements from April 2012 to March 2016. These tidal forests are found to be net C sink with a mean net primary production (NEP) of 276 g C m−2 yr−1 (±35; ±1 Standard deviation amongst the four years). The NEP is partitioned into gross primary production (GPP) and ecosystem respiration indicate gross sequestration of 1581 (±152) g C m−2 yr−1 with a respiratory loss of 1305 (±184) g C m−2 yr−1. We have observed that inter- and intra-annual variations in CO2 fluxes are primarily controlled by environmental factors such as temperature, vapour pressure deficit (VPD), rainfall and photosynthetic active radiation. At the study site, the photosynthetic activity and light use efficiency decreased with an increase in temperature and VPD. Though minimal seasonal fluctuations in CO2 fluxes were observed, a strong linkage has been observed between C fluxes and satellite-derived enhanced vegetation index (MODIS EVI) during the study period. Further, the carbon assimilation rates were found to be higher under diffused sky than normal conditions due to the increased photosynthetic activity by penetration of diffused radiation within the mangrove canopies. Additionally, ecosystem productivity during the study period was higher during the wet periods than dry periods. Our findings show that ecosystem productivity rates are strongly related to temperature, vapour pressure deficit, rainfall, and radiation, implying that global warming could have a significant impact on these environmental factors and other underlying parameters (such as salinity, tidal inundation patterns etc.) and potentially reduce the C sequestration potential of these tropical mangroves of India.

Remotely Sensed Land Surface Temperature Can Be Used to Estimate Ecosystem Respiration in Intact and Disturbed Northern Peatlands

AbstractRemotely sensed land surface temperature (LST) enables global modeling and monitoring of CO2 fluxes from peatlands. We aimed to provide the first overview of the potential for using LST to monitor ecosystem respiration (Reco) in disturbed (drained and extracted) peatlands. We used chamber‐measured data (2017–2020) from five disturbed and two intact northern peatlands and LST data from Landsat 7, 8, and MODIS missions. First, we studied the strength of the relationships between fluxes and their in situ drivers (i.e., thermal and moisture conditions). Second, we examined the association between LST and in situ temperatures. Third, we compared chamber‐measured Reco with the modeled Reco driven by in situ measured water table depth and (a) in situ measured surface temperature and (b) remotely sensed MODIS LST data. In situ temperatures were a stronger driver of CO2 fluxes in disturbed sites (repeated measures correlation rmR = 0.8–0.9) than in intact ones (rmR = 0.5–0.8). LST had a higher association with in situ measured temperatures in disturbed sites (mean rmR = 0.79 for MODIS) and weaker in the intact (hummocks and hollows) peatlands (mean rmR = 0.38 for Landsat and 0.48 for MODIS). Reco models driven by MODIS LST and in situ surface temperature yielded similar accuracy: R2 was 0.27, 0.66, and 0.67 and 0.29, 0.70, and 0.66 for intact and for drained and extracted sites, respectively. Overall, these findings suggest the applicability of LST as a proxy of the thermal regime in Reco models, particularly for disturbed peatlands.

Monitoring the response of volcanic CO2 emissions to changes in the Los Humeros hydrothermal system

Carbon dioxide is the most abundant, non-condensable gas in volcanic systems, released into the atmosphere through either diffuse or advective fluid flow. The emission of substantial amounts of CO2 at Earth’s surface is not only controlled by volcanic plumes during periods of eruptive activity or fumaroles, but also by soil degassing along permeable structures in the subsurface. Monitoring of these processes is of utmost importance for volcanic hazard analyses, and is also relevant for managing geothermal resources. Fluid-bearing faults are key elements of economic value for geothermal power generation. Here, we describe for the first time how sensitively and quickly natural gas emissions react to changes within a deep hydrothermal system due to geothermal fluid reinjection. For this purpose, we deployed an automated, multi-chamber CO2 flux monitoring system within the damage zone of a deep-rooted major normal fault in the Los Humeros Volcanic Complex (LHVC) in Mexico and recorded data over a period of five months. After removing the atmospheric effects on variations in CO2 flux, we calculated correlation coefficients between residual CO2 emissions and reinjection rates, identifying an inverse correlation of ρ = − 0.51 to − 0.66. Our results indicate that gas emissions respond to changes in reinjection rates within 24 h, proving an active hydraulic communication between the hydrothermal system and Earth’s surface. This finding is a promising indication not only for geothermal reservoir monitoring but also for advanced long-term volcanic risk analysis. Response times allow for estimation of fluid migration velocities, which is a key constraint for conceptual and numerical modelling of fluid flow in fracture-dominated systems.

Carbon dioxide fluxes and carbon balance of an agricultural grassland in southern Finland

Abstract. A significant proportion of the global carbon emissions to the atmosphere originate from agriculture. Therefore, continuous long-term monitoring of CO2 fluxes is essential to understand the carbon dynamics and balances of different agricultural sites. Here we present results from a new eddy covariance flux measurement site located in southern Finland. We measured CO2 and H2O fluxes at this agricultural grassland site for 2 years, from May 2018 to May 2020. In particular the first summer experienced prolonged dry periods, which affected the CO2 fluxes, and substantially larger fluxes were observed in the second summer. During the dry summer, leaf area index (LAI) was notably lower than in the second summer. Water use efficiency increased with LAI in a similar manner in both years, but photosynthetic capacity per leaf area was lower during the dry summer. The annual carbon balance was calculated based on the CO2 fluxes and management measures, which included input of carbon as organic fertilizers and output as yield. The carbon balance of the field was −57 ± 10 and −86 ± 12 g C m−2 yr−1 in the first and second study years, respectively.

Lessons learned from more than a decade of greenhouse gas flux measurements at boreal forests in eastern Siberia and interior Alaska

We summarized our recently-published papers on greenhouse gas exchanges at two important boreal regions underlain by permafrost: eastern Siberia and interior Alaska. Relevant literatures were also referred to, and future research directions on the high-latitude terrestrial processes were suggested. Long-term monitoring of CO2 fluxes at the boreal forests revealed that anomalous weather and disturbances changed the CO2 balance. More than a decade is required to return to a CO2 sink at burned forests in interior Alaska. Anomalous high precipitation altered the forest structure in eastern Siberia, shifting the overstory/understory contributions to the CO2 balance. The CH4 emissions were higher in the two boreal forests than in the other boreal forests. Upscaling the in-situ observations and comparisons with top-down approaches revealed considerable inconsistencies exist among the approaches. We recommend the following directions in future research. First, long-term monitoring is indispensable to detect the effect of climate change on ecosystems. Second, disturbance impacts, including fire, thermokarst, and wet spells, need to be quantified. Third, further observations are necessary for constraining CH4 exchange models. Finally, reconciling top-down and bottom-up approaches is required to reduce uncertainty. Prompt sharing of observed data and model products is crucial to improve our understanding of high-latitude processes.

Monitoring of CO2 fluxes on Svalbard: land use alters the gas exchange in the arctic tundra

The article summarized the results of long-term observations (20142018) of soil emissions and net CO2 fluxes (20172018) in natural and anthropogenically modified (AI) ecosystems of Arctic tundra on the territory of the archipelago of Svalbard (Barentsburg, 7804N, 1413E). Anthropogenic controls associated with local land use, during the period of their active impact may redouble the emissions of carbon dioxide from soil (0.111 0.021 0.064 0.011 gС m2h1). During the same period, the net C-balance at the sites with active land use is estimated as a source to the atmosphere. Self-recovering after human influence plots (II) demonstrate intermediate values of soil emissions of СО2 between unaffected tundra (I) and plots with active land use (III). With that they demonstrate the greatest net C-sink within the observed range of Photosynthetically Active Radiation as compared to (I) and (III). At the height of the vegetation period unaffected tundra ecosystems demonstrate a neutral net C-balance. The greatest contribution to soil emissions variance make spatial controls (they explain 5666% of variance), whereas temporal factors are responsible for 3.85.5% only. Amongst spatial controls, the thickness of organogenic layer makes the greatest contribution. Inter-annual fluctuations of key factors, among which the most important are the soil moisture and temperature of the upper soil layer, both affect AI and natural ecosystems hence the spatial differences between them remain constant from year to year. According to preliminary estimates, unlike the carbon dioxide, the contribution of methane and nitrous oxide net fluxes in local ecosystems is insignificant and does not depend on human land use.

Demonstration of Non-Endangerment at the Secarb Anthropogenic Test Site

The Southeast Carbon Sequestration Partnership (SECARB) Anthropogenic Test became the first fully integrated carbon capture, transport, and storage project to successfully demonstrate non-endangerment towards the closure of a Alabama Department of Environmental Management (ADEM) underground injection control (UIC) permit. Despite being a state-issued UIC Class V experimental well permit, this permit contained many elements specific to geologic sequestration of CO2 included in the United States Environmental Protection Agency (EPA) regulations for Class VI wells. This paper will outline the permit structure and the steps taken to demonstrate non-endangerment for the first fully integrated Carbon Capture and Storage (CCS) project on a coal-fired power plant using advanced amines for CO2 capture. The SECARB Anthropogenic Test is a U.S. Department of Energy (DOE), Southern Company, and Electric Power Research Institute (EPRI) funded, Southern States Energy Board (SSEB) managed, project designed to demonstrate deep underground injection and containment of anthropogenic CO2 sourced from a 750 MW (net) coal -fired electric generating unit at Plant Barry, Alabama. From August 2012 to September 2014, a total of 114,104 metric tonnes of CO2 were captured and transported via a 12-mile pipeline from Alabama Power Company’s Plant Barry and successfully injected and stored in the upper Paluxy formation, a Lower Cretaceous sandstone unit, at the Denbury Onshore operated Citronelle Oil Field in Citronelle, Alabama. One CO2 injection well and three monitoring wells were drilled for this project. The initial Class V experimental technology UIC permit application was modified to include some Class VI permit requirements by the EPA to demonstrate protection of underground sources of drinking water (USDWs). These requirements included but were not limited to bottom to top cement coverage, a model-based Area of Review (AoR) determination with periodic updates, and a suite of Monitoring, Verification and Accounting (MVA) methods to track and monitor the CO2 plume migration and containment within the permitted injection zone. The UIC permit required extensive monitoring of the injected CO2 with objectives to create and sustain well integrity, assure safe CO2 injection operations, verify the location and migration of the CO2 plume, and monitor for any CO2 leakage. As such, a suite of technologies were applied and developed to demonstrate non-endangerment of underground sources of drinking water (USDW’s) and to ensure that CO2 does not migrate out of the intended storage zones. This involved several levels of monitoring: surface monitoring, shallow groundwater monitoring, and deep reservoir monitoring via commercially available and experimental MVA methods. Sufficient evidence was provided by the suite of monitoring efforts to indicate successful non-endangerment of USDWs at the Citronelle site. No CO2 release or build-up was detected using groundwater analysis, tracer detection, and soil CO2 flux monitoring to indicate any shallow or surficial leakage of CO2. Additionally, no evidence of gas saturation was observed within or above the confining zone, based on the results of time-lapse pulsed neutron capture logging. Cross-well seismic results show no negative velocity anomalies in or above the confining unit, which implies that there is no detectable leakage out of the injection zone. The associated models simulating the distribution of CO2 through the injected geological layers agreed with observed monitoring data, demonstrating confinement within the injected zone and confirming that the Citronelle Dome structure forms an ideal CO2 storage complex for the confinement of CO2 in the subsurface.

CO2 balance of a secondary tropical peat swamp forest in Sarawak, Malaysia

Tropical peat swamp forest (PSF) has accumulated a huge amount of carbon as peat over millennia, though the carbon rich ecosystem is now threatened with disturbances due to land-use change to industrial plantations of oil palm and pulp woods. Through the land conversion, peat carbon has become vulnerable and potentially changes to a great carbon dioxide (CO2) source to the atmosphere. It is essential to quantify the CO2 balance of the ecosystem and understand how the CO2 balance responds to environmental changes to predict the role of PSF in global carbon cycles. However, filed studies based on the ecosystem-scale monitoring of CO2 flux are quite limited. Thus, we began CO2 flux monitoring over a secondary PSF in Sarawak, Malaysia, by the eddy covariance technique in 2010. Daily NEE and RE were significantly different between the dry and wet periods (p<0.01), respectively, whereas no significant difference was found in daily GPP. As a result, the seasonal difference in NEE between the two periods (0.52gCm−2d−1) was due to that in RE (0.57gCm−2d−1). Daily RE was significantly greater in the dry period mainly because of lower groundwater level (GWL). Lower GWL enhances peat aeration and potentially increases oxidative peat decomposition, which results in higher soil CO2 efflux. Annual NEE was −136±51gCm−2yr−1 (mean±1 standard deviation) during the four years until 2014. The negative annual NEE was equivalent to those of some tropical rain forests on mineral soil, but was more negative than 174gCm−2yr−1 for an almost undrained PSF in Central Kalimantan, Indonesia (Hirano et al., 2012). The difference in annual NEE between the two sites is attributable to higher leaf area index and less distinct seasonality in precipitation in this site.

A reliable and effective methodology to monitor CO2 flux from soil: The case of Lipari Island (Sicily, Italy)

A new unit for continuous monitoring of CO2 flux diffused from soil was developed and preliminary tested in the field at Lipari Island (Sicily, Italy). The developed device (CO2-S-POT), based on the accumulation chamber method, is an assembled unit easy to install and to manage. Both dimensions (104 × 61 × 75 cm) and weight (32 Kg) of CO2-S-POT are lower than the equipment which are commonly used for continuous monitoring of diffused CO2 flux. Besides CO2 flux measurements, it is able to measure several environmental parameters [air temperature, soil temperature, atmospheric pressure, Volumetric Water Content (soil VWC%) and soil conductivity]. Laboratory tests showed a very good performance of the assembled system in terms of detection limit (0.1 mol m−2·day−1), reproducibility (RSD better than 3.5%) and linearity (up to 4 order of magnitude). Field tests (3 months) were performed at Lipari Island (Sicily, Italy), where no continuous monitoring of diffuse CO2 flux using the accumulation chamber method is ongoing. During field tests, the CO2-S-POT performed flux measurements every hour, together with monitoring of the environmental parameters. During field tests, no ordinary or extraordinary maintenance was necessary and no missing data were detected. The soil CO2 flux showed strong influence operated by air pressure, air temperature, soil temperature, soil conductivity, Volumetric Water Content and rain. Statistical methods based on Time Series Fourier analysis (TSFA), Principal Component Analysis (PCA) and also Multiple Linear Regression Analysis (MLRA) are used in order to filter the influence of the environmental parameters on the flux data, and, at the same time, to highlight the contribution which could be due from deep system. Raw flux data (in ppm·sec−1) are used in time series analysis, since these represent the real physical variable measured in the field, without transformations. In fact, the conversion from ppm·sec−1 to another dimension (i.e. mol·m−2·day−1) affects the correlation between the measured parameters (i.e. CO2 flux and environmental parameters).The results of the statistical procedure showed that 1) the oscillation at low period (hours and days) are due to variations of environmental parameters and 2) the soil CO2 flux measured at Lipari is characterized also by long period variations (compared to the previous ones, i.e. weeks), difficult to explain just in terms of environmental parameters. The applied methodology, based on multivariate statistical techniques, has allowed to identify residual anomalies, following a suitable procedure to handle the multicollinearity. In the period from August 20 to August 23, 2014, when there were not both significant air pressure variations and rain events, anomalous positive residuals were identified. These residual anomalies are those interesting from volcanic surveillance point of view. However, to assess whether the residual anomalies are effectively controlled by variations induced by the deep system (i.e. seismic and/or volcanic activity) others parameters, such as wind speed and wind direction, and more time of observation should be taken into consideration.

New perspectives on volcano monitoring in a tropical environment: Continuous measurements of soil CO2 flux at Piton de la Fournaise (La Réunion Island, France)

AbstractDetecting renewal of volcanic activity is a challenging task and even more difficult in tropical settings. Continuous measurements of soil CO2 flux were carried out at the Piton de la Fournaise volcano during 2013–2016. Since this site is in the tropics, periods of heavy rainfall are in the norm. Measurements covered volcanic unrest after a hiatus of 3.5 years. We find that while temperature has the strongest effect, extreme rainfall causes short‐term noise. When corrected and filtered from the environmental influence, soil CO2 time series permit to detect a major deep magmatic event during March–April 2014, 3 months before the first eruption of the new activity phase. Correlation with geophysical data sets allows timing of further stages of upward fluid ascent. Our study validates soil CO2 flux monitoring in tropical environments as a valuable tool to monitor magma transfer and to enhance understanding of volcano unrest down to the lithospheric mantle.

River sequesters atmospheric carbon and limits the CO2 degassing in karst area, southwest China

CO2 fluxes across water-air interfaces of river systems play important roles in regulating the regional and global carbon cycle. However, great uncertainty remains as to the contribution of these inland water bodies to the global carbon budget. Part of the uncertainty stems from limited understanding of the CO2 fluxes at diurnal and seasonal frequencies caused by aquatic metabolism. Here, we measured surface water characteristics (temperature, pH, and DO, DIC, Ca2+ concentrations) and CO2 fluxes across the air-water interface at two transects of Guijiang River, southwest China to assess the seasonal and diurnal dynamics of fluvial carbon cycling and its potential role in regional and global carbon budgets. The two transects had differing bedrock; DM transect is underlain by carbonate and detrital rock and PY is underlain by pure carbonate. Our results show that the river water both degasses CO2 to and absorbs CO2 from the atmosphere in both summer and winter, but the degassing and absorption varied between the two transects. Further, CO2 fluxes evolve through diurnal cycles. At DM, the river evaded CO2 from early morning through noon and absorbed CO2 from afternoon through early morning. At PY in summer, the CO2 evasion decreased during the daytime and increased at night while in winter at night, CO2 uptake increased in the morning and decreased in the afternoon but remained relatively stable at night. Although the river is a net source of carbon to the atmosphere (~15mMm−2day−1), the evasion rate is the smallest of all reported world's inland water bodies reflecting sequestration of atmospheric carbon through the carbonate dissolution and high primary productivity. These results emphasize the need of seasonal and diurnal monitoring of CO2 fluxes across water-air interface, particularly in highly productive rivers, to reduce uncertainty in current estimates of global riverine CO2 emission.

Delineating hazardous CO2 fluxes from acid mine drainage

Incidents of hazardous accumulations of CO2 in homes built on or near reclaimed mine land, in the last decade, have been shown to be linked to neutralization reactions between acidic mine drainage and carbonate material. Recent research has shown that CO2 fluxes on reclaimed mine land with this hazard are, sometimes, spatially autocorrelated (i.e., the spatial variability is not random). This result implies geostatistics can be used to delineate hazardous areas where fluxes are likely to exceed established thresholds. This study applies sequential Gaussian simulation to delineate this emerging hazard on a site in southwestern Indiana, USA. Due to lack of regulatory threshold limits for CO2 flux at the current time, the authors conduct a sensitivity analysis of the threshold limit using the 75th, 90th and 95th percentiles of the measured fluxes for the first day of monitoring. These limits are used to produce hazard maps, which are validated with the known hazard at the site. This work further shows the potential of surface CO2 flux monitoring as a cheap and effective strategy to monitor and delineate such hazards to avoid residential and commercial real estate development in high risk zones.

Technical Note: Cost-efficient approaches to measure carbon dioxide (CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;) fluxes and concentrations in terrestrial and aquatic environments using mini loggers

Abstract. Fluxes of CO2 are important for our understanding of the global carbon cycle and greenhouse gas balances. Several significant CO2 fluxes in nature may still be unknown as illustrated by recent findings of high CO2 emissions from aquatic environments, previously not recognized in global carbon balances. Therefore, it is important to develop convenient and affordable ways to measure CO2 in many types of environments. At present, direct measurements of CO2 fluxes from soil or water, or CO2 concentrations in surface water, are typically labor intensive or require costly equipment. We here present an approach with measurement units based on small inexpensive CO2 loggers, originally made for indoor air quality monitoring, that were tested and adapted for field use. Measurements of soil–atmosphere and lake–atmosphere fluxes, as well as of spatiotemporal dynamics of water CO2 concentrations (expressed as the equivalent partial pressure, pCO2aq) in lakes and a stream network are provided as examples. Results from all these examples indicate that this approach can provide a cost- and labor-efficient alternative for direct measurements and monitoring of CO2 flux and pCO2aq in terrestrial and aquatic environments.

Update on Soil CO2 Flux Monitoring at the Illinois Basin – Decatur Project, USA

The Illinois Basin – Decatur Project (IBDP) is a large-scale carbon capture and storage (CCS) project in Decatur, Illinois, USA demonstrating storage of one million metric tons of carbon dioxide (CO2) in a deep saline reservoir. The IBDP Monitoring, Verification, and Accounting (MVA) program at the 0.65 km2 study site includes a soil CO2 flux monitoring network, measured weekly during the growing season since 2009 and a high-frequency flux and atmospheric CO2 monitoring station. Over 11,000 flux measurements have been collected from the point network and over 50,000 flux measurements have been collected at a higher frequency from a LI-COR Biosciences® LI-8150 multiplexer. No anomalies related to CO2 injection were identified. We also examined site-specific biophysical relationships among soil CO2 flux, soil temperature, and soil moisture, and assessed the flux data to better characterize flux variability. This extensive dataset provides an opportunity to characterize site-wide flux variations in detail, and provides insights into ways t at measured fluxes could be evaluated to identify atypical variations.