Preprints

URI permanente para esta colecciónhttp://10.0.96.45:4000/handle/11056/20514

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Investigating the impacts of biochar on water fluxes in 2 tropical agriculture using stable isotopes
(European Geosciences Union, 2020) C. Fischer, Benjamin M.; Morillas, Laura; Rojas-Conejo, Johanna; Sanchez-Murillo, Ricardo; Suárez Serrano, Andrea; Frentress, Jay; Cheng, Chih-Hsin; García, Mónica; Manzoni, Stefano; Johnson, Mark; Lyon, Steve W
Amending soils with biochar, a pyrolyzed organic material, is an emerging practice to potentially increase plant available water. However, it is not clear (1) to what extent biochar amendments increase soil water storage relative to non-amended soils and (2) whether plants grown in biochar amended soils access different pools of water compared to those grown in non-amended soils. To investigate these questions, we set up an upland rice field experiment in a tropical seasonally dry region in Costa Rica, with plots treated with two different biochar amendments and control plots, from where we collected hydrometric and isotopic data (δ18O and δ2H from rain, soil, groundwater and rice plants). Our results show that the soil water retention curves for biochar treated soils shifted, indicating that rice plants had 2 % to 7 % more water available throughout the growing season relative to the control plots. In addition, we observed a within treatment variability in the soil water retention curves which was in the same order of magnitude as one would expect from responses due to differences in biochar application rates or due to differences in biochar typologies. The stable water isotope composition of plant water showed that the rice plants across all plots preferentially utilized the more variable soil water from the top 20 cm of the soil instead of using the deeper and less variable sources of water. Our results indicated that rice plants in biochar amended soils could access larger stores of water more consistently and thus could withstand dry spells of seven extra days relative to rice grown in non-treated soils. Though supplemental irrigation was required to facilitate plant growth during extended dry periods. Therefore, biochar amendments can complement, but not necessarily replace, other water management strategies.
Stable isotopic characterization of nitrate wet deposition in the tropical urban atmosphere of Costa Rica
(Research Square, 2021) Villalobos Forbes, Mario; Esquivel-Hernández, Germain; Sanchez-Murillo, Ricardo; Sánchez-Gutiérrez, Rolando; Matiatos, Ioannis
Increasing energy consumption and food production worldwide results in anthropogenic emissions of reactive nitrogen into the atmosphere. To date, however, little information is available on tropical urban environments where inorganic nitrogen is vastly transported and deposited through precipitation on terrestrial and aquatic ecosystems. To fill this gap, we present compositions of water stable isotopes in precipitation and atmospheric nitrate (δ 18 O-H2O, δ 2 H-H2O, δ 15 N-NO3-, and δ 18 O-NO3-) collected daily between August 2018 and November 2019 in a tropical urban atmosphere of central Costa Rica. Rainfall generation processes (convective and stratiform) were identified using stable isotopes in precipitation combined with air mass back trajectory analysis. A Bayesian isotope mixing model forced with δ 15 N-NO3-values corrected for potential 15 N fractionation effects reveal the predominant contribution of biomass burning and lightning to nitrate wet deposition. δ 18 O-28 NO3-values in Caribbean convective rainfall reflect the oxidation chemistry of NOx sources whereas δ 15 N-NO3-values in Pacific stratiform rainfall indicate the transport of nitrogen sources contributing to nitrate in atmospheric deposition. These findings provide necessary baseline information about the combination of water and nitrogen stable isotopes with atmospheric chemistry and hydrometeorological techniques to better understand wet deposition processes and to characterize the origin of inorganic nitrogen loadings in tropical regions.
Validación de un método de cromatografía líquida (HPLC-UV/Vis) para la cuantificación de aldehídos agua de lluvia y aire
(2023-07-13) Araya Araya, María Melissa; Sibaja Brenes, José Pablo; Soto-Fallas, Roy; mora barrantes, jose carlos; Alfaro Solís, Rosa; Borbón Alpízar, Henry; Valdés González, Juan
Los aldehídos son compuestos presentes en la atmósfera que se forman por la degradación fotoquímica de otros compuestos orgánicos en la tropósfera, pueden ser emitidos por fuentes naturales o antropogénicas. En el presente trabajo se implementó un método analítico para la cuantificación de muestras de aldehídos en matrices como aire y agua de lluvia. El muestreo y el análisis de los aldehídos utilizó la metodología TO-11 de la Agencia de Protección Ambiental de los Estados Unidos (EPA). El muestreo se realizó mediante el uso de cartuchos de adsorción recubiertos con una disolución de 2,4-DNFH, formando una hidrazona con los aldehídos presentes en el agua de lluvia y en el aire. Estos fueron analizados mediante un cromatógrafo de líquido acoplado a un detector UV-Visible (HPLC-UV/Vis). Para la validación de la técnica de análisis y la calidad analítica de los resultados se determinaron: linealidad, sensibilidad, límites de cuantificación, límites de detección, repetibilidad, reproducibilidad y el porcentaje de recuperación. En el caso de la repetibilidad, se utilizó la comparación del coeficiente de variación de Horwitz con los porcentajes de desviación estándar relativo (% DER) de las muestras. Los límites de detección obtenidos oscilan entre 0,18 μg/m3 para el acetaldehído y 3,20 μg/m3 en el caso de la acroleína, mientras que los límites de cuantificación están entre 0,62 μg/m3 para el acetaldehído y 4,70 μg/m3 para el heptanal, datos que garantizan la calidad analítica del método. En general, el método de análisis para los aldehídos mostró buena correlación lineal, con valores de R2 igual o mayores a 0,9991 para cada curva de calibración, y valores de porcentajes de desvío relativo menores al 2,25 %, indicando una buena precisión en el análisis.

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