Development, calibration and application of new analytical methodologies for measurements of ammonia and nitrogen oxide emissions from fertilized soil

Author(s)

Carolina Gomes da Rocha

• Document type: Doctoral Thesis
• Press: Araraquara. 2021-07-27.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Química. Araraquara
• Defense date: 2021-07-19
• Advisor: Arnaldo Alves Cardoso

Abstract

Modern agriculture is the dominant anthropogenic source in the creation and emission of reactive nitrogen (Nr) compounds to the environment. Once applied to the crops, part of the nitrogen (N) contained in fertilizers is lost to the environment, not only through leaching, but also through the formation of volatile compounds in the soil. Ammonia (NH3) and nitric oxide (NO) are examples of gaseous pollutants from agricultural activities. In the atmosphere, NH3 acts primarily in the neutralization of acidic compounds, which leads to the formation of secondary atmospheric aerosol, which belongs to the fine fraction of the particulate matter. NO, in turn, is rapidly oxidized to nitrogen dioxide (NO2) through reactions with ozone or other atmospheric oxidizing compounds, and subsequently to nitric acid (HNO3) or organic nitrates. In the atmosphere, these gases and their transformation products can be transported by wind, undergo other chemical reactions and/or be deposited back to the Earth's surface. The excessive increase of these pollutants in the environment leads to harmful effects on human health and contributes to the degradation of ecosystems on a regional scale. Thus, the quantification of these emissions from agriculture becomes critical, not only for understanding the contribution of this source and its effects on the environment, but also for evaluating mitigation strategies and improving the N use efficiency. In this way, the present study addresses the development, optimization and calibration of a simple and low-cost analytical methodology for measuring the emission of NH3 and NO/NO2 from the soil using passive samplers associated with a semi-open chamber. Passive samplers were built from commercial monitors using filters impregnated with a specific reagent solution to collect the gases of interest. The passive samplers were coupled to a semi-open chamber, whose calibration step allowed to establish the mass fraction present in the chamber's atmosphere at a given time, thus allowing the estimation of the total amount emitted by the soil portion delimited by the chamber in a given sampling. The proposed methodology was applied to sugarcane crops during a complete cycle and the accumulated emissions in the period were determined. Additional studies, both in the field and in the laboratory, made it possible to verify how different management practices, environmental conditions and soil properties contribute to the emission processes of these compounds to the atmosphere. (AU)

• FAPESP's process: 16/05706-7 - Development, calibration and application of new analytical methodologies for measuring ammonia and nitrogen oxide emissions from fertilized soil
• Grantee: Carolina Gomes da Rocha
• Support Opportunities: Scholarships in Brazil - Doctorate