Methane emission to the atmosphere from landfills in the Canary Islands

Methane (CH4) is an important greenhouse gas, and is increasing in the atmosphere by 0.6% (10 ppb) each year. Important sources of this gas are landfills; in fact more than 10% of the total anthropogenic emissions of CH4 are originated in them by anaerobic degradation of organic matter. Even after years of being closed, a significant amount of landfill gas can be released to the atmosphere through its surface as diffuse or fugitive degassing.Many landfills currently report their CH4 emissions to the atmosphere using model-based methods, which are based on the rate of production of CH4, the oxidation rate of CH4 and the amount of CH4 recovered (Bingemer and Crutzen, 1987). This approach often involves large uncertainties due to inaccuracies of input data and many assumptions in the estimation. In fact, the estimated CH4 emissions from landfills in the Canary Islands published by the Spanish National Emission and Pollutant Sources Registration (PRTR-Spain) seem to be overestimated due to the use of protocols and analytical methodologies based on mathematical models. For this reason, direct measurements to estimate CH4 emissions in landfills are essential to reduce this uncertainty.In order to estimate the CH4 emissions to the atmosphere from landfills in the Canary Islands, 34 surveys have been performed since 1999 to the present. Each survey implies hundreds of CO2 and CH4 efflux measurements covering the landfill surface area. Surface landfill CO2 efflux measurements were carried out at each sampling site by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. Samples of landfill gases were taken in the gas accumulated in the chamber and CO2 and CH4 were analyzed using a double channel VARIAN 4900 micro-GC. The CH4 efflux measurement was computed combining CO2 efflux and CH4/CO2 ratio. To quantify the diffuse or fugitive CO2 and CH4 emission, gas efflux contour maps were constructed using sequential Gaussian simulation (sGs) as interpolation method. Considering that (a) there are 6 controlled landfills in the Canary Islands, (b) the average area of the 34 studied cells is 0.15 km2 and (c) the mean value of the CH4 emission estimated for the studied cells range between 6.2 and 7.2 kt km-2 y-1, the estimated CH4 emission to the atmosphere from landfills in the Canary Islands showed a range of 5.7-6.7 kt y-1 (mean value of 6.2 kt y-1). On the contrary, and for the same period of time, the PRTR-Spain estimates the CH4 emission in the order of 6.4-16.4 kt y-1 (mean value of 9.2 kt y-1), nearly 46% more than our estimated value. This result demonstrates the need to perform direct measurements to estimate the surface fugitive emission of CH4 from landfills.Bingemer, H. G., and P. J. Crutzen (1987), J. Geophys. Res. 92, 2182-2187.

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Monitoring of diffuse CO2 degassing at NERZ, NWRZ and NSRZ volcanic systems of Tenerife, Canary Islands

10.5194/egusphere-egu21-15427 ◽

2021 ◽

Author(s):

Fátima Rodríguez ◽

Eleazar Padrón ◽

Gladys Melián ◽

María Asensio-Ramos ◽

Mar Alonso ◽

...

Keyword(s):

Rift Zone ◽

Emission Rate ◽

Interpolation Method ◽

Sampling Site ◽

Sequential Gaussian Simulation ◽

Rift System ◽

Volcanic Complex ◽

North East ◽

The North ◽

Volcanic Seismicity

One of the main volcano-structural and geomorphological feature in Tenerife (2,034 km2) is the triple rift system, formed by aligned of hundreds of monogenetic eruptive products of shield basaltic volcanism. At the intersection of this triple rift system rises the Teide-Pico Viejo volcanic complex. These volcanic rifts are considered as active volcanic edifices. The North East volcanic Rift Zone (NERZ, 210 km2) form a main NE-SW structure. The North West volcanic Rift Zone (NWRZ, 72 km2) is oriented in NW-SE direction and the North South volcanic Rift Zone (NSRZ, 325 km2) comprises a more scattered area on the south of these monogenetic cones. The most recent eruptive activity of Tenerife has taken place in these rift systems. NERZ host the fissural eruption of Arafo-Fasnia-Siete Fuentes (1704-1705). NWRZ host two historical eruptions: Arenas Negras in 1706 and Chinyero in 1909. Recently the eruption of Boca Cangrejo (1492) has been added to the historical register through 14C dating. NSRZ does not host historical volcanism, although it is recent, up to 10,000 years old.In order to provide a multidisciplinary approach to monitor potential volcanic activity changes at the NERZ, NWRZ and NSRZ, diffuse CO2 emission surveys have been undertaken since 2000, in general in a yearly basis, but with a higher frequency when seismic swarms have occurred in and around NWRZ volcano. Each study area for NERZ, NWRZ and NSRZ comprises hundreds of sampling sites homogenously distributed. Soil CO2 efflux measurements at each sampling site were conducted at the surface environment by means of a portable non-dispersive infrared spectrophotometer (NDIR) LICOR Li820 following the accumulation chamber method. To quantify the CO2 emission rate from the NERZ, NWRZ and NSRZ a sequential Gaussian simulation (sGs) was used as interpolation method.The diffuse CO2 emission rate for the NERZ ranged from 532 up to 2823 t d-1 between 2001 and 2020, with the highest value measured in 2020. In the case of NWRZ, the diffuse CO2 emission rate ranged from 52 up to 867 t d-1 between 2000 and 2020, with the highest value measured in one of the surveys of 2005. Finally, and for NSRZ, the diffuse CO2 emission rate ranged from 78 up to 819 t d-1 between 2002 and 2020, with the highest value measured in 2019. The temporal evolution of diffuse CO2 emission at the NERZ, NWRZ and NSRZ shows a nice and clear relationship with the volcanic seismicity in and around Tenerife Island, which started to take place from the end of 2016. The good temporal correlation between the volcanic seismicity and the increase trend observed in the time series of diffuse CO2 emission rates at NERZ, NWRZ and NSRZ is also coincident with the observed increase of diffuse CO2 emission rate at the summit crater of Teide. This work demonstrates the importance of performing soil CO2 efflux surveys at active rift systems in volcanic oceanic islands as an effective geochemical monitoring tool.

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Urban soil gas geochemistry to identify permeable zones and possible upflow of deep-seated gases at the city of Ourense, Galicia, Spain

10.5194/egusphere-egu2020-19805 ◽

2020 ◽

Author(s):

Gladys V. Melián ◽

Nemesio Pérez ◽

Lucía Sáez -Gabarrón ◽

Fátima Rodríguez ◽

Pedro A. Hernández ◽

...

Keyword(s):

Urban Area ◽

Sampling Site ◽

Mean Value ◽

Soil Gas ◽

Sequential Gaussian Simulation ◽

Geochemical Data ◽

Distribution Analysis ◽

Activity Measurements ◽

Gas Geochemistry ◽

The City

Thermal waters from natural hot springs and boreholes are clear geothermal features of the city of Ourense (Galicia, Spain). The urban area of Ourense is located in the Mi&#241;o River&#8217;s valley which is characterized by two fault systems (NW&#8211;SE and NE&#8211;SW) that determine the groundwater circulation in the region. The low permeability of the granite and granodiorite only allows fluid circulation throughout faults and fractures transporting the fluid and transferring the heat to the lower elevations in the valley (Araujo 2008; Fern&#225;ndez Portal et al. 2007). During July to August 2019, an intensive soil gas geochemical survey was carried out at urban area of Ourense in order to identify the presence of vertical permeable structures and possible upflow of deep-seated gases. A total of 539 soil gas samples were taken with an average distance of &#8776;100 m between sampling sites and covering an area about 13Km2. In-situ soil CO2 efflux and soil gas 222Rn activity measurements were performed at each sampling site. In addition, soil gas samples at 40 cm depth were collected for chemical (He, Ne, H2, O2, N2, CH4 and CO2) and isotope (d13C-CO2 vs. VPDB) analysis by micro-gas chromatography and IRMS, respectively. Soil CO2 efflux and 222Rn activity values ranged from 0.7 to 92 g&#183;m-2&#183;d-1 (mean value of 16 g&#183;m-2&#183;d-1) and from 2.7 to 743 Bq&#183;m-&#179; (mean value of 73 Bq&#183;m-&#179;), respectively. Regarding soil gas He and H2 concentration, the values ranged from 5.2 to 25.0 ppmV (mean value of 6.2 ppmV) and from 0.5 to 24.9 ppmV (mean value of 1.9 ppmV), respectively. Soil CO2 concentrations showed a range between 355 and 53,766 ppmV (mean value of 7,824 ppmV) with a range of isotopic ratios from -14.1 to -28.5&#8240; vs. VPDB (mean value of -22.1 &#8240;). The binary plot of d13C-CO2 vs 1/CO2 concentration suggest the presence of small fractions of CO2 deep-seated in the soil gas atmosphere (mainly an atmospheric and biogenic gas mixture) of the city of Ourense. Soil CO2 efflux, soil gas Rn-222 activity and soil gas He, H2 and CO2 concentration contour maps were constructed using the sequential Gaussian simulation (sGs) interpolation method. Estimated diffuse CO2 emission from the study area is about 201 tons per day and about 8 tons per day could be considered deep-seated degassing. Spatial distribution analysis of the soil gas geochemical data show relatively high values of soil CO2 efflux and soil gas H2 concentration at the Chavasqueira-Tinteiro urban sector, while As Burgas and Outariz-Mui&#241;o urban sectors showed relatively high values of soil 222Rn activity. These results show the usefulness of the soil gas geochemistry to identify permeable zones and possible upflow of deep-seated gases at the city of Ourense.

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Diffuse CO2 degassing monitoring of the Tenerife North–South Rift Zone (NSRZ) volcano, Canary Islands

10.5194/egusphere-egu2020-12067 ◽

2020 ◽

Author(s):

María Cordero-Vaca ◽

Carolina A. Figueiredo ◽

Nicole L. Czwakiel ◽

Eleazar Padrón ◽

Gladys V. Melián ◽

...

Keyword(s):

Canary Islands ◽

Rift Zone ◽

Emission Rate ◽

Interpolation Method ◽

Graphical Analysis ◽

Sequential Gaussian Simulation ◽

Average Value ◽

Effusive Activity ◽

Background Population ◽

Tenerife Island

Tenerife (2,034 km2) is the largest of the Canary Islands and the North South Rift Zone (NSRZ) is one of the three active volcanic rift-zones of the island. The NSRZ (325 km2) is characterized mainly by effusive activity of basaltic lavas forming spatter and cinder cones and comprises 139 monogenetic cones representing the most common eruptive activity occurred on the island during the last 1Ma. In order to provide a multidisciplinary approach to monitor potential volcanic activity changes at the NSRZ volcano, diffuse CO2 emission surveys have been undertaken since 2002. This study shows the results of the last soil CO2 efflux survey undertaken in summer 2019, with &#8275;600 soil gas sampling sites homogenously distributed in the study area. Soil CO2 efflux measurements were performed at the surface environment by means of a portable non-dispersive infrared spectrophotometer (NDIR) LICOR Li820 following the accumulation chamber method. Soil CO2 efflux values ranged from non-detectable (&#8275;0.5 g m-2 d-1) up to 30 g m-2 d-1, with an average value of 2.6 g m-2 d-1. In order to distinguish the existence of different geochemical populations on the soil CO2 efflux data, a Sinclair graphical analysis was done. The average value of background population was 2.1 g m-2 d-1 and that of peak population was 18.5 g m-2 d-1, representing the 97% and the 1% of the total data, respectively. To quantify the total CO2 emission rate from the NSRZ volcano a sequential Gaussian simulation (sGs) was used as interpolation method. The diffuse CO2 emission rate for the studied area was estimated in 2019 in 819 &#177; 18 t d-1, ranging from 466 to 819 t d-1 between 2002 and 2019, with the highest value measured in 2015 (707 t d-1). The temporal evolution of diffuse CO2 emission at the NSRZ shows a clear relationship with the volcano seismic activity in and around Tenerife Island, which started to taking place from the end of 2016. This study demonstrates the importance of studies of soil CO2 efflux at the NSRZ volcano of Tenerife island as an effective volcanic monitoring tool, especially in areas where there is no visible degassing (fumaroles, etc.)

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Surface diffuse degassing monitoring of the Tenerife Northeastern Rift Zone (NERZ) volcano, Canary Islands

10.5194/egusphere-egu2020-11604 ◽

2020 ◽

Author(s):

Lucía Sáez-Gabarrón ◽

Jazlyn Beeck ◽

Sian Reilly ◽

Mar Alonso ◽

Víctor Ortega-Ramos ◽

...

Keyword(s):

Interpolation Method ◽

Graphical Analysis ◽

Point Of View ◽

Sequential Gaussian Simulation ◽

Contour Maps ◽

Average Value ◽

North East ◽

The North ◽

Tenerife Island ◽

Total Data

The North East Rift volcanic Zone (NERZ) of Tenerife Island is one of the three volcanic rift-zones of the island, oriented NW-SE (NWRZ), NE-SW (NERZ) and a more scattered area on the south (NSRZ). From a volcano-structural point of view, NERZ is more complex than NW or NS rifts due the existence of Pedro Gil stratovolcano that broke the main NE-SW structure. Pedro Gil Caldera was formed&#160; 0.8&#160; Ma ago by a vertical collapse of this stratovolcano. The most recent eruptive activity along the NERZ took place during 1704 and 1705 along a 13 km of fissural eruption of Arafo-Fasnia-Siete Fuentes. Diffuse CO2 emission surveys have been undertaken in a yearly basis since 2001 in order to provide a multidisciplinary approach to monitor potential volcanic activity changes at the NERZ. The aim of this study is to report the results of the last soil CO2 efflux survey undertaken in summer 2019, with 639 measuring sites homogeneously distributed in an area of 210 km2. In-situ measurements of CO2 efflux from the surface environment of NERZ were performed by means of a portable non-dispersive infrared spectrophotometer (NDIR) following the accumulation chamber method. Soil CO2 efflux contour maps were constructed to identify spatio-temporal anomalies and to quantify the total CO2 emission using the sequential Gaussian simulation (sGs) interpolation method. The CO2 efflux values ranged from non-detectable (0.5 g m-2 d-1) up to 72,3 g m-2 d-1, with an average value of 10,9 g m-2 d-1. Statistical-graphical analysis of the 2019 data show two different geochemical populations; background (B) and peak (P) represented by 70.4% and 1.9% of the total data, respectively. The geometric means of the B and P populations are 0.4 and 4.3 g m-2 d-1, respectively. The diffuse CO2 emission rate was estimated in 2,205 t d-1. Studying the long-term variations on the diffuse CO2 emission since 2001, two main pulses are identified: one in 2007 and a second one sustained over time between 2014 and 2019. Enhanced endogenous contributions of deep-seated CO2 might have been responsible for the higher CO2 emissions values observed during those pulses. The 2014-2019 pulse appears to be related to the seismic activity that started taking place in Tenerife at the end of 2016. This study denotes the importance of soil CO2 efflux surveys at the NERZ volcano of Tenerife Island as an effective volcanic monitoring tool.

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Diffuse H2 degassing studies: a useful geochemical tool for monitoring Cumbre Vieja volcano, La Palma, Canary Islands

10.5194/egusphere-egu21-15403 ◽

2021 ◽

Author(s):

Nemesio M. Pérez ◽

Gladys V. Melián ◽

Pedro A. Hernández ◽

María Asensio-Ramos ◽

Eleazar Padrón ◽

...

Keyword(s):

Canary Islands ◽

Emission Rate ◽

Monitoring Program ◽

Hydrothermal Systems ◽

Sequential Gaussian Simulation ◽

Homogeneous Distribution ◽

La Palma ◽

Soil Degassing ◽

Geothermal Activity ◽

Cumbre Vieja

Hydrogen (H2) is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas. Although H2 can be produced in soils by N2-fixing and fertilizing bacteria, soils are considered nowadays as sinks of molecular hydrogen (Smith-Downey et al. 2006). Because of its chemical and physical characteristics, H2 generated within the crust moves rapidly and escapes to the atmosphere. These characteristics make H2 one of the best geochemical indicators of magmatic and geothermal activity at depth. Cumbre Vieja volcano (La Palma, Canary Islands) is the most active basaltic volcano in the Canaries with seven historical eruptions being Tenegu&#237;a eruption (1971) the most recent one. Cumbre Vieja volcano is characterized by a main north&#8211;south rift zone 20 km long, up to 1950 m in elevation and covering an area of 220 km2 with vents located at the northwest and northeast. Cumbre Vieja does not show any visible degassing (fumaroles, etc.). For that reason, the geochemical volcano monitoring program at Cumbre Vieja volcano has been focused on soil degassing surveys. &#160;Here we show the results of soil H2 emission surveys that have been carried out regularly since 2001. Soil gas samples were collected in about 600 sampling sites selected to obtain a homogeneous distribution at about 40 cm depth using a metallic probe and 60 cc hypodermic syringes and stored in 10 cc glass vials. H2 content was analysed later by a VARIAN CP4900 micro-GC. A simple diffusive emission mechanism was applied to compute the emission rate of H2 at each survey. Diffuse H2 emission values were used to construct spatial distribution maps by using sequential Gaussian simulation (sGs) algorithm, allowing the estimation of the emission rate from the volcano. Between 2001-2003, the average diffuse H2 emission rate was &#8764;2.5 kg&#183;d&#8722;1 and an increase of this value was observed between 2013-2017 (&#8764;16.6 kg&#183;d&#8722;1), reaching a value of 36 kg&#183;d&#8722;1 on June 2017, 4 month before the first recent seismic swarm in October, 2017 at Cumbre Vieja volcano. Six additional seismic swarms had occurred at Cumbre Vieja volcano (February 2018, July-August 2020; October 8-10, 2020; October 17-19, 2020, November 21, 2020 and December 23-26, 2020) and changes of diffuse H2 emission related to this unrest had been observed reaching values up to &#8764;70 kg&#183;d&#8722;1. Diffuse H2 emission surveys have demonstrated to be sensitive and excellent precursors of magmatic processes occurring at depth in Cumbre Vieja. Periodic diffuse H2 emission surveys provide valuable information to improve and optimize the detection of early warning signals of volcanic unrest at Cumbre Vieja volcano.

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