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Here, a degraded soil, located in a semi-arid Mediterranean region, was characterized 17 years after organic amendment with sludge or compost (differing in their stabilization degree) for restoration purposes. To do this, (i) soil physicochemical properties and plant cover, (ii) soil organic matter (SOM) content and composition, (iii) soil basal respiration and enzymatic activities, and (iv) abundance, taxonomic composition, and functionality (shotgun metagenomics) of microbial communities were studied. Increased SOM and nutrient contents were found in soil from amended plots with respect to the control, with no differences between amendment types. This is explained by the lasting effects of organic amendments and the higher plant cover. Thermal and pyrolytic analyses showed that the restoration process enriched soil mainly with SOM of intermediate recalcitrance and of high chemical diversity. SOM composition did not differ between amendment types. Increased microbial abundances and activities were found in the amended plots, without differences between compost and sludge. Shotgun metagenomics showed that microbial communities changed in taxonomic and functional terms between amended and unamended plots, but these differences were rather limited. The taxonomic differences between treatments were mainly driven by increasing abundances of Actinobacteria and decreasing abundances of Proteobacteria in soil from amended plots. Soil microbial communities in amended plots showed some functional adaptation to the increased nutrient contents and predominant nutrients forms. This, together with the higher microbial abundances detected, explained the conspicuous soil enzymatic activities reported in amended plots. The effectiveness of the studied soil restoration process was confirmed here from an integrative perspective.

Removing lampenflora, phototrophic organisms developing on rock surfaces in tourist cavities due to the artificial lighting, is a challenge for sustainable and appropriate long-term management of caves. Photosynthetic-based biofilms usually cause rock biodeterioration and an ecological imbalance in cave ecosystems. In this work, a detailed investigation of the effects of the 3 most commonly used lampenflora cleaning operations (NaClO, H2O2 and UVC) was carried out in Pertosa-Auletta Cave (Italy). The application of NaClO showed good disinfection capability over extended periods of time without causing any appreciable rock deterioration. The H2O2 treatment showed to be corrosive for the rock surfaces covered with vermiculation deposits. The chemical alteration of organic and inorganic compounds by H2O2 did not remove biomass, favoring biofilm recovery after three months of treatment. Both NaClO and H2O2 treatments were effective at removing photoautotrophs, although the bacterial phyla Proteobacteria and Bacteroidetes as well as Apicomplexa and Cercozoa among the Eukaryotes, were found to be resistant to these treatments. The UVC treatments did not show any noticeable effect on the biofilms.

The impact of biochar modification on its behavior towards the adsorption and cracking of naphthalene (in a mixture naphthalene/toluene) as tar model compound has been investigated. Both tar adsorption and cracking may be considered alternative tar cleaning technologies which enable its further energetic use. Biochars were produced using different feedstocks and process conditions to tune their physico-chemical and morphological properties. Beech wood, representative of woody biomass, and almond shell and rice husk, representative of agricultural residues, were used. Furthermore, beech wood was also washed with deionized water and doped with KCl and FeSO4. Biochars were produced at 700 degrees C under several atmospheres (pure N2 and mixtures of N2, CO2, H2O, and CO), resulting in different physico-chemical properties and thus naphthalene adsorption and cracking behavior. Naphthalene adsorption experiments were performed at 250 degrees C and naphthalene cracking experiments were carried out at 750 degrees C and 850 degrees C. The performance of the investigated biochars towards naphthalene adsorption and cracking depended strongly on the production conditions, with biochars produced under reactive atmosphere (including N2, CO2, and H2O) yielding the best behavior. For naphthalene adsorption, an easily accessible high surface area seemed to be the dominant parameter determining the biochar adsorption capacity. Wood doping with FeSO4 resulted in biochars with higher adsorption capacity due to the formation of mesopores and Fe clusters within these mesopores that could likely enhance the adsorption capacity. In the case of naphthalene cracking, biochars produced under reactive atmosphere (G1) with untreated wood and H2O-washed wood showed the highest naphthalene conversion. In this case, the specific surface area was not the most relevant parameter determining the biochars performance. Wood doping with KCl had a negative impact on naphthalene cracking, while wood dopin

Volcanic caves are priceless resources found worldwide. Recently, these environments and the life within have captured the attention of the world, due to the detection of numerous volcanic cave entrances on the Moon and Mars. The TUBOLAN and HIRES-SOM (funded by the Spanish Ministry of Science and Innovation), the MICROCENO (funded by the Portuguese Foundation for Science and Technology) and the MICROLAVA (funded by the Regional Government of Andalusia) research projects are extraordinary examples of the raising scientific interest in exploring lava tubes on Earth. The goals are the deep characterization of the highly complex subsurface microbial communities adapted to lava tubes from Lanzarote and La Palma (Canary Islands, Spain), and Selvagens Islands (Portugal), respectively, and understand their interactions with biotic and abiotic factors to provide clues on how microbial life has evolved. Recognizing biosignatures and reconstruct climate information recorded in siliceous speleothems from these volcanic caves are also key priorities of these ongoing projects. The interdisciplinary and international dimensions gleaned in these projects are crucial toward properly exploring and protect these unique underground resources. The objective of this multidisciplinary meeting was to gather European leading researchers involved in the study of volcanic caves to share their knowledge, results obtained thus far and discuss current development in their respective fields.

Today’s agriculture has the challenge of ensuring food supply for a growing population while human activity has already deteriorated about 40% of the world’s soils, reducing productive capacity and increasing reliance on mineral fertilizers. In this context, valorizing and recycling mineral and agricultural waste for use as substrates or soil supplements enhance a sustainable economy, as well as the development of activities focused on finishing the soil nutrients’ cycle. Looking for an effective solution to the massive waste generation and to enhance the agronomic qualities of soils, this study investigates the agronomic impact of contrasting inorganic and organic materials such as green compost (GC), wood biochar (WB), rice husk ash (RA), and volcanic ash (VA) as amendments to an alkaline Luvisol under controlled conditions. In this sense, barley seeds were planted and grown in a greenhouse under controlled conditions for 60 days on a soil amended with the aforementioned materials. The amendments demonstrated appropriate attributes for improving soil agronomic properties, enhancing the soil’s nutritional content with no effect on barley germination. The WB showed high aromaticity and abundance of refractory organic C. Both ash-rich amendments showed high P and K contents, which are important elements for plant development. The GC has high water retention capacity and an adequate C and N balance. Although the application of the amendments had no effect on barley yields, the plants from the ash-amended pots showed an increase of Photosystem II efficiency, indicative of a better physiological status. In terms of toxicological safety, the abundance of trace elements in soils and plants was investigated. All soils met the maximum allowable limits for these persistent pollutants. Nevertheless, longer-term tests on plants are required to determine the risk of Pb accumulation, particularly in soils amended with GC and compost-ash mixtures. The simultaneous combination of

La repelencia al agua del suelo (RAS) se atribuye a la acumulación de compuestos hidrofóbicos (lípidos), pero su extracción no siempre elimina la RAS, lo que sugiere que componentes macromoleculares no extraíbles también pueden estar relacionados con una RAS. Se han estudiado suelos quemados (B) y control (UB) del Parque Nacional de Doñana (Huelva, España) bajo dos tipos de vegetación (alcornoque y brezo) y fracciones de suelo: gruesa (1–2 mm) y fina (<0.05 mm). La composición molecular de la materia orgánica del suelo (MOS) se analizó mediante espectrometría de masas de ultra-alta resolución. Además, se empleó la regresión por mínimos cuadrados parciales (PLS) para explorar la relación entre la RAS y la MOS definida por la abundancia de los 1221 compuestos orgánicos comunes. También se utilizaron índices para obtener gráficas que faciliten la identificación de biomarcadores de la RAS. En los suelos quemados, la RAS estaba significativamente relacionada (P<0.05) con compuestos aromáticos y condensados, mientras que, en los suelos control, la MOS incluía compuestos aromáticos y ligninas. En las fracciones finas, la RAS estuvo relacionada principalmente con lípidos, pero, no se encontró correlación en las fracciones gruesas. Los resultados permiten concluir que la hidrofobicidad depende de varias famílias de compuestos orgánicos. La combinación de la FT-ICR/MS con herramientas estadísticas ha facilitado la obtención de nuevos biomarcadores de RAS.

Las sabanas mediterráneas (dehesas) son sistemas agrosilvopastoriles típicos, caracterizados por la presencia dispersa de robles (Quercus spp.) y especies arbustivas. Estos ecosistemas están sometidos a una marcada estacionalidad, propia del clima mediterráneo, lo que se refleja en la dinámica microbiana del suelo. La interacción de los factores que más afectan la dinámica microbiana (clima, vegetación y suelo), es clave para comprender los ciclos biogeoquímicos que, a su vez se espera que se reflejen en la estructura de la materia orgánica (MOS). Para evaluar el efecto del cambio climático, utilizamos pirólisis analítica (Py-GC/MS) para la caracterización molecular de la MOS en un experimento de imitación en campo (2017-2021). Entre los 117 compuestos biogénicos encontrados, las distribuciones y contenidos de ác. grasos y n-alcanos fueron más sensibles a los tratamientos climáticos. Además, se observa una degradación preferencial de compuestos derivados de holocelulosa y acumulación de compuestos derivados de la lignina, que se encuentra poco evolucionada, lo que apunta a condiciones desfavorables para la su degradación. Los resultados sugieren que la composición molecular de la MOS y la aplicación de Py-GC/MS aporta información sobre los cambios ambientales del suelo y que tienen valor como biomarcadores para el seguimiento del cambio climático en suelos mediterráneos.

The effects of olive waste biochar and green compost as soil amendments on soil physical properties, as well as on physiological parameters and yield of a super-intensive olive crop cultivated under deficit irrigation conditions, were investigated in south-west Spain during the 2021 growing season. Thus, soils were amended with 40 t ha−1 of olive pomace waste biochar, green-compost, or a biochar-compost mixture (50% w/w), and no amended plots were used as control. On a bi-monthly basis, soil pH, water holding capacity, humidity, and resistance to penetrability were determined. In addition, various indicators of the physiological status and water stress of the plant were also monitored. Finally, the olive yield per tree was measured. Results showed that biochar application was the most effective amendment for increasing soil moisture and reducing soil compaction. The latter was evidenced by the significant reduction of the resistance to the penetrability of the amended soils. Plants of the amended plots showed better leaf water potential. In addition, values of the net photosynthesis rate, the average intrinsic water-use efficiency, and the maximum rate of electron transport in the time before the harvest improved significantly in the trees from the biochar-amended plots, for which olive fruit yields increased by about 15% in comparison with the other treatments. Nevertheless, the estimated net oil yield per tree was similar because the olives from the biochar-amended trees contained more moisture. This field trial shows for the first time that by providing the soil with biochar from olive crop waste as an organic amendment, having high water retention capacity, porosity, and stability, it would be possible to reduce the irrigation water needed and maintain plant yields.

This study aims to evaluate the effects of technosols made with different organic amendments to restore degraded soils in a semiarid limestone quarry. The effects on soil quality, functionality and organic matter dynamics of the technosols amended with waste of gardening, greenhouse horticultural, stabilized sewage sludge and two mixtures of sludge with both vegetable composts were assessed. Several physical and chemical properties, humus fractions, soil respiration and molecular composition was performed after 6 and 18 months. Un-amended soils, and nearby natural undegraded soils served as reference. Amended technosols increased water retention capacity, electrical conductivity, total organic carbon and nitrogen, respect to not amended and natural soils. Humus fraction composition was not altered over time. Un-amended soils, very poor in organic matter, did not show any pyrolyzable compounds or labile soil organic matter by thermogravimetry. In contrast, the pyrochromatograms of natural soils showed lignocellulosic materials, polypeptides and a noticeable presence of alkylic compounds. In technosols with both types vegetable compost, the organic matter structure was more complex, showing compounds from lignin-derived and long-chain alkyl, polysaccharides, chlorophyll isoprenoids and nitrogen. In sludge technosol, a set of sterols was outstanding. The mixtures showed a molecular fingerprint of materials derived from the decomposition of the organic amendments that formed them. These signs of the contribution of different organic matter forms derived from the amendments were also reported by the series exothermic peaks found in the calorimetry. This short-term study indicates a clear effect of the amendments on the recovery of soil organic matter and presumably of its functionality. After the amendments application, microbial activity and soil respiration rates increased rapidly but ceased 18 months later. The molecular composition of the organic matter of the soils

Volcanic speleothems are cave formations found in lava tubes that are composed of minerals that have been deposited by volcanic activity. Siliceous speleothems are important to determine the timing and intensity of past volcanic eruptions, as well as assessing the environment conditions [1]. Another important contribution is the identification of biosignatures (organic compounds or microorganisms) preserved within the speleothems, which is relevant for astrobiology. However, for that, it is required the use of increasingly cutting-edge analytical molecular characterization techniques with the goal to analyze a remarkable number of different organic compounds. One of the most promising techniques is analytical pyrolysis coupled to ultra-high resolution mass spectrometry (Py-GC/Q-TOF). This advanced technique allows the analyze of more than 15,000 different organic compounds per sample, without any pre-treatment. However, this overwhelming number is not feasible to study each organic compound individually. Therefore, it is mandatory the development of novel graphical-statistical tools to help identifying their main biogenic families [2], as well as the alterations and adaptation of microorganisms to environmental (e.g., climate change, drought) or anthropogenic (e.g., oil spills, forest fires) factors [3,4]. In this communication, it will present the advantages of the combination of ultra-high resolution analytical pyrolysis technique and chemometrics as an innovative strategy for unsupervised classification and visual analysis of organic matrices preserved in siliceous speleothems. References: [1] Miller, A.Z., et al., Journal of Chromatography A 1461 (2016) 144-152. [2] Jiménez-Morillo, N.T., et al., Science of the Total Environment 817 (2022) 152957. [3] Miller, A.Z., et al., Science of the Total Environment 698 (2020) 134321. [4] Miller, A.Z., et al., IScience 25 (2022) 104556.

Pyrolysis (Py) is the thermochemical decomposition of organic materials (OM) at elevated temperatures without oxygen. The products of Py are amenable to chromatographic separation which, when combined with appropriate detectors, yields valid fingerprint information about the composition and molecular structure of complex mixtures of natural and synthetic macromolecules [1-2]. Analytical Py poses several advantages over other techniques for OM characterization: minimal or no sample preparation needed, the small sample size required, and the ability to detect and characterize a wide variety of organic materials in a single analysis, including recalcitrant and low solubility organic forms [3]. Therefore, this technique is convenient for relatively rapid analyses of scarce or precious organic samples such as those that may be found in extreme environments. In this communication, apart from the conventional Py techniques such as Py associated with gas chromatography and mass spectrometry (Py-GC/MS), will give examples of the application of other more advanced variants to speleothems analyses that provide complementary or more accurate information. These include pyrolysis associated with compound-specific isotope analysis (Py-CSIA) and ultra-high resolution analytical Py (Py-GC/Q-TOF) that are unique and available in our labs at IRNAS-CSIC MOSS Group. References: [1] González-Pérez, J.A., et al., Journal of Chromatography A 1388 (2015) 236–243. [2] San-Emeterio, L.M., et al., Applied Science 11 (2021) 6684. [3] Quénéa, K., et al., Journal of Analytical and Applied Pyrolysis 76 (2006) 271–279.

Speleothems represent a valuable archive of paleoclimatic information. In order to identify environmental changes that occurred in the past [1] and to establish protocols for valid models in searching for signs of life in lava tubes, the TUBOLAN and MICROCENO projects study the composition of the organic matter remains preserved in siliceous speleothems in lava tubes from Lanzarote and Selvagens islands, respectively. However, the small size of the samples, their nature, and the challenges of extracting the organic components trapped in them and analyzing with conventional methods, have hindered their use for reconstructing environmental changes [2]. Lanzarote Island offers an extraordinary variety of lava tubes and siliceous speleothems formed through different post-volcanic processes. In addition, Selvagens Islands (Madeira, Portugal) constitute an isolated and undisturbed ecosystem, and consequently, its volcanic caves are a promising model system for investigating pristine biosignatures preserved in siliceous speleothems. Here we show the results of thermal analyses performed on a gypsum core collected in the Inferno Cave (Selvagen Grande Island) and on sediments sampled on the floor of Naturalistas, Las Breñas, and Pescadores caves (Lanzarote). The gypsum core showed the presence of thermostable organic compounds preserved mainly in layers H3-H5 and H7, matching the highest organic carbon contents of the whole profile. The H6 layer shows the presence of organic constituents with contrasting composition. Sediments from Lanzarote lava tubes exhibit a high abundance of organic compounds derived from micro-organisms and the remains of higher plants (leached from the soil above the cave). A complete characterization of the samples, including geochronology, is being performed to relate changes in the speleothems composition to historical episodes of environmental disturbance or/and climatic events. References: [1] Miller, A.Z., De la Rosa, JM, Jimenez-Morillo, NT, Pe

Compost amendments, apart from improving fertility and the general characteristics of agricultural soils, have known implications for global C cycling and sequestration in soils. Their effects are usually assessed via the quantification of soil organic carbon (SOC) pools, usually labile (fast) and recalcitrant (slow) pools, with varying intrinsic decomposition rates and distinct resident times. However, the real C-sequestration potential of organic additions to soil is still under discussion. In this study, a field trial and a lab incubation experiment were designed to study the C-sequestration mechanism in an agricultural Mediterranean soil. Soil with a history of C3 photosystem crop was amended with two maize composts from maize harvesting surpluses (C4 photosystem) with different maturity stages (AC: aged compost; NC: new, less mature compost). The evolution of SOM was monitored for 6 months using complementary analytical techniques, including analysis of stable C isotopes (IRMS), thermogravimetry (TG) and C-stock and priming effect (PE) modelling. Based on the natural C-isotope labelling, the proportion of new C was calculated. More than 50% of the C added to the soil with the compost was incorporated into the SOM in only 6 months. However, the application of maize compost did not always enhance soil C-sequestration capacity. The addition of compost caused a general PE, enhancing SOM decay and reducing the fast (labile) SOM mean residence time (MRT) (11.2 days). This was more pronounced with the addition of a higher dose of AC, causing a PE up to a 718%. On the other hand, a higher MRT (54.4 days) occurred in soils with NC applied, likely due to its deleterious effects, limiting heterotrophic activity. Despite that, the average MRT of the slow (recalcitrant) SOM pool was lower than usually reported. The application of higher doses of both composts generally showed greater MRT values compared to control (1.7 years vs. 3.8 and 2.9 years for NC and AC, respectively

It is accepted that prescribed fires generally led to low losses of the organic and mineral superficial layers,especially as compared to the moderate or high intensity burning of wildfires. Consequently, prescribed fires have been largely used to reduce wildfire risk or change the land use. Still, the effects of the fire in the soil C and N pools are not totally understood. The main objective of this research was to assess the effects of prescribed versus wildfires on the soil C and N stocks of Mediterranean forest and shrublands. Additionally, the relation of proxy visual indicators, such as the Soil Burn Severity (SBS) with the maximum temperature reached at different depths was also assessed in the prescribed fires. Pre-/unburned and post-fire/burned organic (L, FH) and mineral soil samples (0-2, 2-5, 5-10 cm) were gathered from three prescribed fires and four wildfires. The three prescribed fires burned at low SBS (Cartaya: 2.2, Doñana20:1.9 and Doñana21: 0.7), two wildfires burned at moderate SBS (Casares: 3.2 and Bermeja-L: 2.7) and twoat high SBS (Monchique: 4.4, Bermeja-H: 3.9). Pre-fire C stocks ranged from 70-15 Mg ha-1 in theprescribed fire sites; and from 60-30 Mg ha-1 in the wildfire sites. All fires dropped the C and N contentson the organic layers, and the effect consistently decreased with increasing the mineral soil depth. The consumption of the C stocks was, on average, 50, 34 and 14%, respectively for Cartaya, Doñana20 and DOñana21 prescribed fires; while in the moderate wildfires it was 26% and 12% (Casares and Bermeja-L) and 38-39% for the high severity wildfires. The consumption of the N stocks on the prescribed sites was high (37 to 13%) if compared to the moderate wildfires (8-2%) but similar to the 35-27% consumption in the high severity wildfires. The pre-fire soil C and N stocks, as well as the conditions at which prescribed fires were carried out should be re-evaluated to prevent high consumptions of the soil organic matter

Soil phosphorus (P) is a limiting element, essential for the ecosystem functioning and the long-term plant nutrition. The changes in the availability of P forms in different post-fire scenarios is still scarce. Our main objective was to assess the effects of prescribed fires and wildfires in the dynamics of soil P forms in Mediterranean forests (Southern Iberian Peninsula). Both wildfires (Sierra Bermeja) and prescribed fires (Cartaya, Doñana) were selected, and the surface organic layer and the uppermost mineral soil (0-2 cm) were sampled in unburned (pre-fire) and burned (post-fire) sites immediately after fire and one year after. Besides the strong increase in pH (>2 pH units) and the loss of SOM, extractable P increased immediately after fire. 31P-NMR spectroscopy indicated that both prescribed and wildfiresled to the transformation of the different P fractions, especially at the organic layer. The low severity burning on the organic layer produced a short-term peak of orthophosphate, reducing the organic P (P mono- and diesters) in both prescribed and wildfires. However, fire affected more severely the P pool in the organic than the mineral fraction. P forms were almost completely mineralized, the effect decreasing with decreasing fire severity: Sierra Bermeja (high severity) > Sierra Bermeja (low severity) ~ Cartaya fire > Doñana fire. As fire severity decreased, different P forms and the organic:inorganic P ratios (Po:Pi) dramatically increased. The profile of P compounds was markedly dependent on the origin of fire. Despite both wildfires and prescribed burns affected the mineral fraction (0-2 cm), clear differences were observed in the organic layer. After one year, the composition of the different soil P forms in prescribed fires was similar to prefire conditions, but this was not the case of the wildfires, even the low severity burning.

La agricultura actual se enfrenta al reto de garantizar el suministro de alimentos a una población en continuo crecimiento mientras la actividad humana ya ha deteriorado sobre el 40% de los suelos cultivables del planeta, aumentando la dependencia de los fertilizantes minerales. En este contexto, la valorización de residuos agrícolas para utilizarlos como sustratos o suplementos del suelo se propone como alternativa, creando además una solución a la generación masiva de residuos orgánicos agro-ganaderos. Este trabajo muestra las propiedades físicas de interés agrnómico y la composición (macro y micronutrientes) de biochars, composts y cenizas producidas a partir de restos vegetales de las agroindustrias olivadera y des arroz, y los efectos de su aplicación a los suelos calcáreos (Xerochrept y Luvisol) bajo condiciones de clima mediterraneo. Las enmiendas mostraron atributos apropiados para mejorar las propiedades agronómicas del suelo. El biochar mostró una alta aromaticidad y abundancia de C orgánico estable. Las enmiendas ricas en ceniza mostraron altos contenidos en P y K y micronutrientes. El compost presento una elevada capacidad de retención de agua y un adecuado balance de C y N. Todas las enmiendas orgánicas redujeron la hidrofobicidad del suelo. La aplicación de biochar consiguió aunmentar la humedad del suelo en los primeros 10 cm y reducir su compactación, los que se evidencio por la reducción significativa de la resistencia del suelo a la penetrabilidad. Las plantas de las parcelas enmendadas mostraron un mejor potencial hídrico foliar. Además, los valores de la tasa de fotosíntesis neta, la eficiencia media de uso del agua intrínseca y la tasa máxima del transporte de electrones en el momento de la cosecha mejoraron significativamente en los árboles de las parcelas enmendadas con una dosis de biochar de 40 t ha-1. En relación al ciclo de C, la adición de compost incrementó de manera significativa la respiración (emisión de CO2) y la cantidad de C proced

Volcanic eruptions are geological events spewing large amounts of magma-derived products such as hot lava, volcanic ash, water, and gases. Among the most iconic features of effusive eruptions are lava tubes, which have also been detected on the Moon and Mars. On Earth, these cavities are rapidly colonized by specialized microorganisms, whose growth is fueled by surface-derived organic matter transported via percolation water or by CO2 fixed in situ by chemolithoautotrophic organisms. The likelihood presence of essential life-supporting molecules on Mars, coupled with the interconnection between the origin of life and volcanic eruptions, leads to an intriguing possibility: the existence of specialized chemoautotrophic life within planetary caves. This notion fuels excitement regarding the potential preservation of microbial life within the lava tubes of Mars. Combining microbiological, mineralogical, and organic geochemistry tools, an in-depth characterization of speleothems and associated microbial communities in lava tubes of Lanzarote (Canary Islands, Spain) is provided. The aim is to untangle the underlying factors influencing microbial colonization in Earth’s subsurface in order to gain insight into the possibility of similar subsurface microbial habitats on Mars and to unequivocally identify biosignatures preserved in lava tubes. In this sense, analytical pyrolysis, stable isotope analysis and chemometrics were conducted to characterize the complex organic fraction preserved in speleothems from Lanzarote lava tubes, one of the best terrestrial analogues to Martian volcanology. Our data show that bacterial communities are important contributors to biomarker records in volcanic-hosted speleothems. Within them, the lipid fraction primarily consists of low molecular weight n-alkanes, α-alkenes, and branched-alkenes, providing further evidence that microorganisms serve as the origin of organic matter in these formations. Thus, our research will lay the foundation

Forest fires are a recurrent ecological phenomenon in the Mediterranean basin. They induce molecular changes in soil organic matter (SOM) leading to immediate and long-term environmental consequences [1]. The SOM is of paramount importance as indicator of soil health [2]. Fire-induced changes in SOM include the alteration of biogenic chemical structures and the accumulation of newly formed ones, enhancing dynamics in the complex balance between the different C-types [2,3]. Therefore, understanding SOM molecular composition, before and after fire, is fundamental to monitor changes in soil health, as well as its natural or man-mediated recovery [3,4]. Our aim was to assess the molecular composition of organic matter in fire-affected leptosols, at two depths (0-2 and 2-5 cm) under different vegetation types located in the southwestern of Portugal (Aljezur, Algarve). The SOM characterization was conducted by analytical pyrolysis (Py-GC/MS), a technique based on the thermochemical breakdown of organic compounds in the absence of oxygen at elevated temperatures [5]. The Py-GC/MS has been found suitable for the structural characterization of complex organic matrices [4], providing detailed structural information of individual compounds considered fingerprinting of SOM. However, due to the relative high number of molecular compounds released by analytical pyrolysis, the use of graphical-statistical methods, such as van Krevelen diagrams, are usually applied to help monitoring SOM molecular changes produced by fire [3,4]. This work represents the first attempt to evaluate the fire effects in SOM using a detailed molecular characterisation of SOM under different vegetation canopies, recently affected by wildfire, in southern Portugal. References:[1] Naveh, Z., 1990. Fire in the Mediterranean - a landscape ecological perspective. In: Goldammer, J.G., Jenkins, M.J. (Eds.), Fire in Ecosystems Dynamics: Mediterranean and Northern Perspective. SPB Academic Publishing, The Hague.[2

Siliceous speleothems, formed by mineral deposition in lava tubes, are vital for understanding past volcanic eruptions, assessing environmental conditions, and investigating extreme life forms. Molecular characterization of cave samples is also relevant, needing the use of cuttingedge analytical techniques. The analytical pyrolysis (Py) coupled with exact-mass spectrometry (Py-GC/Q-TOF) is a promising one. Analytical Py involves thermal decomposition of organic matter (OM) at high temperatures without oxygen, enabling chromatographic separation and providing valuable information about complex mixtures’ composition and molecular structure, including natural and synthetic macromolecules. Advantages of analytical Py include minimal sample preparation, small sample sizes, and detection of various organic materials, even those with low solubility or resistance to degradation. This technique facilitates rapid analysis of scarce or unique organic samples found in extreme environments and Mars analogues. Ultra-high resolution analytical pyrolysis (UH-Py) allows the identification of numerous distinct organic molecules in a sample without pre-treatment. However, due to the large number of chemical structures discovered, investigating each molecule separately is unfeasible. To address this, novel graphical-statistical tools are needed to identify primary chemical and biogenic families in a sample and investigate microorganisms’ adaptations to environmental or anthropogenic factors. This communication introduces the integration of UH-Py with multivariate statistical analysis and graphic-statistical tools as an innovative strategy for unsupervised classification and visual analysis of preserved organic matrices in siliceous speleothems from diverse lava tubes. The study focuses on samples from Selvagens Islands, La Palma (Canary Island), Easter Island, and the Galapagos Islands. By combining these analytical techniques, it becomes possible to identify biosignatures, such as mic

Plastic production has skyrocketed since the 1950s, resulting in over 8.3 billion tons of plastic generated and a projected 1500 million tons by 2050. Plastics have become pervasive but also environmentally impactful, contributing to CO2 emissions and marine pollution. Every year, 4.8 to 12.7 million metric tons of plastic waste enter the ocean, microplastics are small fragmented pieces (< 5 mm) of fragmented plastic debris, microbeads, and fibres, becoming a persistent pollutant in the sea and beaches. They absorb persistent organic pollutants (POPs) and Polybutylene terephthalate (PBTs) and can harm marine life by acting as carriers for pollution. Land-based sources account for 80% of microplastic pollution, while the fishing industry contributes 18%. In this work, we have sampled polluted sand at two depths (0–10 and 10–20 cm) at two sites in Lagoas de Santo André e da Sancha Nature Reserve, Alentejo coast (Portugal): close to the sea (P) and close to the lagoon (L) within a transect of 1.3 km with a separation of 150 m among sites. The main goal of this study was to monitor and identify the type of plastic at the molecular scale to understand its occurrence, composition, and impact to aid in the development of mitigation strategies and a better understanding of their environmental impact. In identifying microplastics techniques such as Fourier-transform infrared spectroscopy, Raman spectroscopy, and Thermogravimetry are commonly used. Another technique widely used in microplastic molecular characterization is nominal mass analytical pyrolysis (Py-GC/MS). Pyrolysis techniques have well-known advantages such as the requirement of small sample size with little or no preparation, being therefore convenient for inexpensive and relatively rapid analyses of scarce or little samples. Here, a novel exactmass high-resolution analytical pyrolysis (Py-GC/Q-TOF) technique is described and -to the best of our knowledge- for the first time used to identify the constituent mono

Pyrolysis, heating biomass in the absence of oxygen, enables the conversion of biomass residues into biochar [1]. It is an aromatic carbonaceous material with high porosity and adsorption capacity, which can be activated and used in the production of filters that function similarly to commercial activated carbon (AC) filters. This study evaluates the adsorption capacity of biochar produced from rice husk (RH) and almond shell (AS) for the removal of emerging organic contaminants (EOCs) in water. This application could reduce the concentration of EOCs derived from pharmaceuticals and pesticides present in water, avoiding the use of activated carbons (AC) derived from fossil coal or imported from long distances. Additionally, it would reduce the implementation of pyrolysis and activation processes that pose high environmental risks and promote the recycling and valorization of low-value residual biomass. Biocarbons (BCs) were produced from RH and AS at pyrolysis temperature of 750 °C and were activated with steam or KOH (for comparative purposes). The elemental composition, physical properties, and iodine index of the BCs were determined before and after activation. Subsequently, their adsorption capacity of Sulfamethoxazole, Atenolol, Carbamazepine, Diclofenac, Salicylic Acid, and Acetaminophen were measured (n=3). These organic compounds represent cationic, anionic, and neutral pharmaceuticals and pesticides, some of which are currently considered as EOCs due to their frequent presence in hospital and wastewater effluents. For this purpose, 100 mg of each BC sample were mixed with 20 mL of a 10 mg L-1 solution of each contaminant, shaken for 24 hours and centrifuged. The contaminant concentrations in the supernatant were measured using high-performance liquid chromatography with a diode array detector (HPLC-DAD). The chromatographic column used was a reverse-phase C18 (Novapack, Waters Co.) with specific mobile phases for each contaminant. All the activated BCs were

Olive cultivation is a crucial driver of the economy in the European Mediterranean basin, particularly in Spain, where it occupies about 2.75 million ha [1]. In recent years, there has been an expansion of super-intensive olive farming, which ensures high productivity but requires irrigation and is expected to increase organic waste generation and water demand. Consequently, it is imperative to adopt more sustainable approaches to manage the agricultural waste generated during olive harvesting and agro-industrial processing. To tackle that challenge, there is a renewed emphasis on utilizing organic amendments derived from agricultural residues. Biochar (B), a highly aromatic carbon obtained through biomass pyrolysis, has the potential to sequester carbon in the soil for extended periods and its unique physical properties increase soil porosity [2]. Nevertheless, B effects on SOM composition and functionality in the medium and long term are largely unknown. Additionally, green compost (Cp) is rich in nutrients and labile organic carbon, making it a valuable soil amendment for improving soil fertility, structure, and moisture retention. The two main goals of this study are: i) To discern the effects of transforming traditional olive orchards into bushrow olive cultivation on soil organic matter (SOM) composition, which plays an essential role in the carbon cycle and on soil quality, and ii) To assess the effects of of B and Cp on SOM composition two years after application. With such purposes, soil samples were taken from super-intensive olive orchards (1650 trees/ha; irrigated 30% water needs) amended with (B), green compost (Cp), a combination of B+Cp, as well as control plots [3]. Soil samples were also collected from traditional olive orchards in the same farm (La Hampa, Coria del Río) for comparative purposes. The free lipid fraction and volatile SOM were studied by using GC/MS and analytical pyrolysis (Py-GC/MS) respectively. Control soils, particularly those fr

[Introduction]: Caves are exceptional habitats for highly specialized microorganisms that can interact with minerals, allowing us to better understand the role of microorganisms in biogeochemical cycles and biomineralization processes. These priceless subterranean resources can be found all over the world, but they are one of the least explored habitats on Earth. Yet, lava caves have recently received special attention due to the discovery of numerous volcanic cave entrances on the Moon and Mars [1]. Such subsurface geological settings, characterized by stable physicochemical conditions, may support microbial activity over geological timescales, resulting in the preservation of traces of life in the rock record, recognized as biosignatures. These subterranean environments and the microbial life within thus provide a unique opportunity to study extremely specialized microorganisms, novel metabolic strategies, and interactions with igneous rocks relevant to astrobiology and planetary sciences., [Methods]: The diversity and function of microbial communities dwelling on speleothems from volcanic caves of Selvagens Islands (Madeira, Portugal), La Palma and Lanzarote (Canary Islands, Spain) have been investigated using portable cutting-edge DNAbased analysis, complemented by in-depth metagenomics and field emission scanning electron microscopy (FESEM), to understand which microorganisms grow in these extreme ecosystems, which functional properties they have, and their role in constructive and/or destructive mineral processes. In addition, advanced chromatography, and mass spectrometry techniques, such as GC/MS, PyrolysisGC/Q-TOF and Pyrolysis-compound specific isotope analysis (Py-CSIA) have been employed for an indepth biogeochemical characterization of the siliceous speleothems and for the assessment of biosignatures preserved in the samples, as described in Miller et al. [2,3]., [Results and Discussion]: Bacterial communities showed heterogeneity in composition among lava tubes, with the Actinomycetota, Bacillota and Bacteroidota phyla as the most abundant, exceeding 50% for most of the sampling sites. Using FESEM, we described the morphology of microbial cells and their interactions with the mineral substrate. FESEM images showed abundant actinobacteria-like cells and other morphotypes, resembling those reported by Riquelme et al. [4] in lava tubes from USA, Canada, Portugal and Spain, and in Etna lava tubes [5]. Observations conducted on microbial mat samples from a lava tube in Lanzarote revealed the presence of Ca-rich spheroids closely associated with filamentous cells of Crossiella sp.. The functional profile of microbial communities predicted by PICRUSt showed the presence of urease enzyme, that has been identified as responsible for the microbial precipitation of CaCO3 via urea hydrolysis [6], suggesting that this genus could promote speleothem formation. Similar biogenic-like CaCO3 microspheres were reported in colored microbial mats from Kipuka Kanohina lava cave in Hawaii, USA [4]. The presence of short-chain n-alkanes (C<20) and methylated fatty acids identified in the organic fraction of the siliceous speleothems are recognized as biosignatures of microbial origin (membrane lipids and/or microbial metabolites). High molecular weight lipid compounds (e.g., sterols and long-chain nalkanes) are indicative of vegetation biomarkers derived from lixiviation processes of the soil overlying caves

Today's agriculture faces the challenge of guarantee food supply of a growing population while human activity has already degraded nearly 40 % of the world's soils [1], which lose productive capacity and increase dependence on mineral fertilizers. In this context, the valorization and recycling of mineral and agricultural waste for use as substrates or soil amendments promotes the local and sustainable economy as well as the implementation of activities based on closing the soil nutrients’ cycle. Moreover, pyroclastic rocks and volcanic ashes formed by volcanic eruptions are usually rich in Si, Ca, Mg, Al, Fe, K, P and S [2], so they can be used in agriculture as inorganic mulch. Looking for an effective solution to the great waste generation and the current challenges of sustainable agriculture [3], this study addresses the agronomic effects of the application of contrasting inorganic and organic materials including green compost, wood biochar, rice husk ash and volcanic ash released in the recent eruption of the Tajogaite volcano (La Palma Island, Spain) as amendments of an alkaline soil typical of the Mediterranean basin. For this purpose, barley seeds were planted and grown under controlled conditions in a greenhouse for 60 days on a Luvisol amended with the above-mentioned materials. The organic amendments improved soil physical properties, such as the reduction of bulk density and of the soil resistance to penetration, and increased the organic carbon content. Biochar increased the amount of refractory organic matter of the Luvisol. The application of rice husk ash, volcanic ash, and to a lesser extent the green compost, increased the nutrient content of the soil. Nevertheless, no significant differences were observed on germination rates, productivity and abiotic markers of stress of the barley plants. Acknowledgements: Authors thank the financial support from the Spanish Ministry of Science and Innovation (MCIN) under the projects RES2SOIL (PID2021-126349OB

e expected shortage of global phosphate has enforced the search for alternative resources for P fertilizers. Therefore, the present study focuses on the turnover of phosphorus (P) of hydrochars and pyrochars derived from sewage sludge (SS) in soils during plant growth. We designed a pot experiment in which Lolium perenne L. was allowed to grow on a Calcic Cambisol amended with SS-derived chars. Hydrothermal carbonization (HTC) yielded the SS-hydrochars (200 °C, 260 °C; 30 min, 3 h), whereas the SS-pyrochars were obtained after dry pyrolysis (600 °C, 1 h). Increasing severity of HTC lowered the recovery of total P (PT) from the feedstock to 76%. The Olsen-P diminished from 4% PT in the untreated sludge to 1% PT in the hydrochars, whereas the pyrochars exhibited an Olsen-P between 3 and 6%. At the end of the pot experiment, the soils amended with pyrochars and with hydrochars produced at 200 °C contained more Olsen-P than the unamended soils, proving that P-rich chars can indeed serve as a P fertilizer. Part of the P sequestered in the chars turned into a mobile form during the experiment. After addition of our chars, the soil pH remained alkaline, allowing the conclusion that P could not have been solubilized through just abiotic processes. We suggest that biological and biochemical processes are involved in this mobilization. This work demonstrates that, in order to evaluate the efficiency of an organic amendment as a P fertilizer, the knowledge of their P availability alone is not sufficient and a better understanding of the biochemical processes involved in the cycling of its immobilized P is certainly required.

Understanding the global carbon (C) cycle is critical to accurately model feedbacks between climate and soil. Thus, many climate change studies focused on soil organic carbon (SOC) stock changes. Pyrogenic carbon (PyC) is one of the most stable fractions of soil organic matter (SOM). Accurate maps based on measured PyC contents are required to facilitate future soil management decisions and soil-climate feedback modelling. However, consistent measurements that cover large areas are rare. Therefore, this study aimed to map the PyC content and stock of the Iberian Peninsula, which covers contrasting climatic zones and has long-term data on wildfire occurrence. A partial least square (PLS) regression using the mid-infrared spectra (1800–400 cm−1) was applied to a dataset composed of 2961 soil samples from the Iberian component of the LUCAS 2009 database. The values of PyC for LUCAS points were modelled to obtain a map of topsoil PyC by a random forest (RF) approach using 36 auxiliary variables. The results were validated through comparison with documented historical wildfire activity and anthropogenic energy production. A strong relationship was found between these sources and the distribution of PyC. Our study estimates that the accumulated PyC in Iberian Peninsula soils comprises between 3.09 and 20.39% of total organic carbon (TOC) in the topsoil. Forests have higher PyC contents than grasslands, followed by agricultural soils. The incidence of recurrent wildfires also has a notable influence on PyC contents. This study shows the potential of estimating PyC with a single, rapid, low cost, chemometric method using new or archived soil spectra, and has the ability to improve soil-climate feedback modelling. It also offers a possible tool for measuring, reporting and verifying soil C stocks, which is likely to be important moving forward if soils are used as sinks for C sequestration

High severity wildfires cause a drastic alteration of soil carbon cycling – both oxidising and thermally altering soil organic matter (SOM) - and usually are followed by strong runoff and erosion events. To restore wildfire-degraded soils, SOM needs to be rebuilt while soil erosion is prevented. Post-fire straw mulching has been shown to mitigate soil erosion by providing a protective cover against rainsplash. However, SOM takes many decades or centuries to rebuilt naturally. Biochar, co-applied with straw to the soil surface can replace the SOM of the O-horizon, while the stabilised soil – by straw mulching – may gain in SOM naturally and by downward movement of biochar. We conducted a field study to test if straw-only and straw-biochar co-application could restore soils degraded by wildfire in one high burn severity (HBS) and one moderate burn severity (MBS) study area in southern Portugal and Spain, respectively, by monitoring erosion and SOM for the most intense rainfall period of the first post-fire year. Burned sites were characterized for soil and sediment physical properties, TOC content, SOM quality by thermogravimetry (DTG) and nuclear magnetic resonance (NMR 13C) spectroscopy. Straw-biochar mulching significantly reduced soil erosion by 76% and 65% in the HBS and MBS sites, respectively, in both cases similar to the erosion reduction by straw-only mulching. DTG and NMR 13C indicated that a relatively small proportion of the biochar eroded, i.e. 0.7%, indicating that co-application of straw with biochar may help restore the SOC lost in the wildfire in the medium term. The amount of SOM eroded was lower with straw-biochar mulching than in the untreated plots for both study areas. Straw-biochar mulching mitigate erosion of wildfire-degraded soils under extreme rainfall, while a relatively small proportion of the biochar is lost by erosion. Future studies need to monitor medium term effects.

Biochar application to soils has become a focus of research during the last decade due to its high potential for C sequestration. Nevertheless, there is no exhaustive information on the long-term effects of biochar application in soils contaminated with trace elements. In this work, a 2-year field experiment was conducted comprising the application of different types of biochar to acidic and moderately acidic soils with high concentrations of As, Cu, Pb, Ba and Zn. In addition, representative samples of each biochar were buried in permeable bags that allowed the flow of water and microorganisms but not their physical interaction with soil aggregates. The biochars significantly adsorbed trace elements from polluted soils. However, given the high total concentration of these persistent trace elements in the soils, the application of biochars did not succeed in reducing the concentration of available metals (CaCl2 extractable fraction). After 2 years of ageing under field conditions, some degradation of the biochars from olive pit, rice husk and wood were observed. This study provides novel information concerning the biochar alterations during ageing in polluted soils, as the decrease of aryl C signal observed by 13C nuclear magnetic resonance (NMR) spectroscopy and the presence of O-containing groups shown by Fourier Transform mid-Infrared Spectroscopy (FT-IR) in aged biochar which enhanced trace elements adsorption. Scanning electron microscopy (SEM) revealed slight changes on surface morphology of aged biochar particles.

This study assesses the biochemical degradability of biochars produced from five contrasting crop residues (rice husk, olive pit, almond shell, maize straw and wood chips) in acidic soils contaminated with trace elements. For this purpose, highly and moderately acid soils were amended with each of the proposed biochars and subjected to a microbial degradation experiment under controlled conditions for 155 days. CO2 production of pure biochars fitted with a single exponential model, indicating that they only had one C pool. Among the biochars studied, those derived from olive pit and almond shell showed the greatest stability, with mean residence times (MRT) of 293 and 214 years, respectively, whereas, maize straw biochar revealed MRT of 82 years. Despite that the average MRT of all tested biochars under controlled conditions were shorter than usually reported, biochar addition increased the MRT of the recalcitrant C pool of the studied soils by a factor from 2x to 13 × . Solid-state 13C NMR spectra confirmed a partial cracking of the biochar aromatic network during the experiment due to microbial degradation or physical alteration processes. It was further noted that biochar degradability depended on its aromaticity but we have also observed that in highly acidic and metal-contaminated soils biochar is less degraded, probably due to the difficulties for microbial development at these soils.

This work studies carbon (C) and hydrogen (H) isotope composition of plant biomass and soil organic matter (SOM) in an attempt to assess both, changes exerted by fire and possible inputs of charred materials to the soil after a wildfire. Isotope composition of bulk soil, soil particle size fractions and biomass of the dominant standing vegetation in the area (Quercus suber) from Donana National Park (SW-Spain) were studied by isotope ratio mass spectrometry (IRMS). SOM C isotope composition indicates the occurrence of two SOM pools with different degree of alteration. Coarse soil fractions (>0.5 mm) were found C-13 depleted with delta O-13 values close to those in leaf biomass, pointing to a predominance of poorly transformed SOM. Conversely, fine fractions (<0.1 mm) were found enriched in C-13 as corresponds to a more humified SOM. The fire produced no changes in this trend, although a consistent C-13 enrichment (c. 1 parts per thousand) was observed in all soil fractions with decreasing size. Concerning H isotopes, the coarse fractions (>0.5 mm) displayed significant lower delta H-2 values than the intermediate and fine ones (<0.5 mm), again similar to those in leaf biomass (c.-80 parts per thousand), whereas the fine fractions were found deuterium (H-2)-enriched with significant higher delta H-2 values (c. 50 parts per thousand), suggesting physical speciation of H depending on soil particle size. The fire produced a significant H-2 depletion (Delta H-2 c. -10 parts per thousand) in the finer fractions (<0.1 mm). The study of stable isotope analysis added new information and complements the results obtained by other proxies to better understand the effect of fire on SOM. (C)2020 Elsevier B.V. All rights reserved.

The lack of scientific information about the effects of wildfire on prehistoric structures and rock art, such as dolmens and petroglyphs, impedes the development of conservation guidelines. In this study, the impact of a recent wildfire (late 2017) on granite outcrops in the San Salvador de Coruxo archaeological site (Vigo, SW Galicia) was evaluated. Samples of the same type of granite were obtained from three sites characterised by different types of vegetation (natural scrub, native deciduous oak and non-native pine-eucalypt forest) in order to determine how the vegetation influences the fire-caused damage to the rock. Three subsamples were taken from each of the granite samples at depths of 1 cm–3 cm to study how fire affects the rock at depth. In all sites, the temperature reached at the granite surface was below 380 °C. No mineralogical changes due to fire exposure were detected, and no physical changes that could be attributed to the effect of the fire on the fissure system of the granite were identified. However, aesthetic colour changes due to the deposition of organic and charred matter, which even penetrated the fissures, were detected. The existence of lignin-derived compounds, lipids and carbohydrates in the samples from the oakwood site indicates greater resistance to fire effects in this type of vegetation than in the other two types. Although preliminary, these findings suggest that oakwoods could act as protective belts around archaeological sites by reducing the wildfire severity, because of their greater resistance to being burnt, and that they could buffer the damaging effects of fire in natural areas where parietal art is found.

Application of biochar has been widely suggested as a remediation tool for trace element-polluted soils, but the impact of biochar on microbial communities and on native plants remain largely unknown. To overcome this knowledge gap, biochar produced from rice husk and olive pit were applied at a rate of 8 t ha−1 into a soil with two contrasting levels of trace elements (high and moderate) to study their effects on soil microbial community composition, vegetation cover and soil properties after 1, 6, 12 and 20 months under field conditions. Differences in bacterial community composition were studied using the Illumina Miseq technology of the 16S rRNA gene. Although variations in soil properties and ecological function were seasonal and soil-type dependent, biochar application enhanced soil properties and vegetation cover in the moderately polluted soil (MPS), and increased microbial diversity as well as vegetation cover in the highly polluted soil (HPS). Enzymatic activities and soil respiration rates were not modified with the application of biochar, but increased total carbon content of soils. The application of biochar from crop residues to trace-element contaminated soils provided environmental benefits, including plant diversity and growth, as well as the increase of bacterial diversity and carbon sequestration.

To track changes in organic matter (OM) in peat soils, analytical techniques are needed that effectively characterize their chemical components. Pyrolysis-gas chromatography/mass spectrometry is a useful method for obtaining a chemical "fingerprint" of OM. To obtain representative fingerprints, the pyrolysis process should be highly reproducible and representative of the original sample; however, these key indicators for successful volatilization are underreported in the literature. We investigated the influence of instrumental parameters (temperatures, heating rates, sample mass), original organic C and nitrogen (N) content, and instrument type ("slow" vs "flash"), on volatilization of different peat samples by monitoring sample mass loss and changes in organic C and N content before and after pyrolysis. Average percent C by mass volatilized ("C pyrolysis efficiency") across all pyrolysis experiments conducted (mass, instrument types, and settings) was 47.8 +/- 1.8%. Sample mass was not a major driver; however, instrument temperatures, heating rate, and original N content had a significant influence on pyrolysis efficiency. N pyrolysis efficiency occurred at significantly higher rates (56.7-75.8%) than C pyrolysis efficiency (45.1-51.6%). N pyrolysis efficiency was also negatively influenced by decreasing concentrations of original sample N, suggesting that N-containing compounds may undergo preferential volatilization in high pyrolysis temperatures. Our data suggest that C pyrolysis efficiency is relatively insensitive to instrumental parameters; whereas when seeking to identify N-containing compounds, appropriate temperatures and heating rates must be chosen. These results provide an expected range for pyrolysis efficiency as a reference for peat samples analyzed with this technique.

Soil contamination with trace elements is an important and global environmental concern. This study examined the potential of biochars derived from rice husk (RHB), olive pit (OPB), and a certified biochar produced from wood chips (CWB) to immobilize copper (Cu2+) and lead (Pb2+) in aqueous solution to avoid its leaching and in a pot experiment with acidic Xerofluvent soils multicontaminated with trace elements. After assessing the adsorption potential of Cu2+ and Pb2+ from an aqueous solution of the three studied biochars, the development of Brassica rapa pekinensis plants was monitored on polluted soils amended with the same biochars, to determine their capability to boost plant growth in a soil contaminated with several trace elements. RHB and CWB removed the maximum amounts of Cu2+ and Pb2+ from aqueous solution in the adsorption experiment. The adsorption capacity increased with initial metal concentrations for all biochars. The efficiency in the adsorption of cationic metals by biochars was clearly affected by biochar chemical properties, whereas total specific surface area seemed to not correlate with the adsorption capacity. Among the isotherm models, the Langmuir model was in the best agreement with the experimental data for both cations for CWB and RHB. The maximum adsorption capacity of Cu2+ was 30.77 and 58.82 mg g−1 for RHB and CWB, respectively, and of Pb2+ was 19.34 and 77.52 mg g−1 for RHB and CWB, respectively. The application of 5% of RHB and CWB to the acidic polluted soils improved soil physico-chemical properties, which permitted the development of Brassica rapa pekinensis plants. RHB and CWB have been shown to be effective for the removal of Cu2+ and Pb2+, and the results obtained regarding plant development in the soils contaminated with trace elements indicated that the soil amendments have promising potential for the recovery of land polluted with heavy metals.