Exploring rice biomass burning and its chemical transformations in the Valencia Region

Rice is one of the most widely cultivated cereals in the world. In Europe, rice cultivation is limited to Mediterranean countries, where geographical characteristics for rice production can be found. Spain is the second largest European producer. There are some regions in Spain, being Levante (Valencia) the most important one, with a long cultural, social, and gastronomic tradition associated with rice production. Valencian Community annually produce more than 60 kt of straw, a large part of which will follow a burning process of elimination due to sanitary reasons. The practice of burning it in the field produces harmful effects on the environment and human health.

The burning of rice straw, a common practice in many agricultural regions, continues to be a significant source of air emissions. causing frequent acute pollution episodes and exceedances of regulatory limits. However, there is a notable lack of knowledge about the nature of the emissions and their potential health hazards, as well as their contribution to secondary pollution and in particular to photochemical processes. Within this context, emissions and their chemical transformation were studied from 27/09/2023 to 02/11/2023 in the Valencia Region near a smoke-affected area. Using advanced analytical techniques, including gas chromatography, and particle analysis, a detailed evaluation of the components emitted during the burning of rice straw has been carried out. Various analytical instruments were used to characterize both the optical properties and chemical composition of the particle phase (aethalometers, nephelometer, PM low-cost sensors and PM₁₀ and PM_2.5 filters for offline analysis) and the gas phase (optical equipment, monitors, Tenax, DNPH and C18 cartridges, and high-resolution state-of-the-art spectrometers: PTR-MS), which allowed a detailed examination of the chemical composition, aging and transformation of the emissions.

The results reveal a diversity of gaseous pollutants, including nitrogen oxides (NOx), sulfur dioxide (SO₂) and volatile organic compounds (VOCs), whose concentrations and compositions vary significantly depending on combustion conditions.In addition, an exhaustive characterization of the aerosols and particles generated has been carried out, highlighting the presence of fine particulate matter with potential impact on air quality and human health. The preliminary results show high values ​​of VOCs, PM₁₀, PM_2.5 and PM₁ in the populated areas near the burned plots. These emissions also caused elevated ozone values up to 120 µg m^-3 ​​in interior areas of the region, previously associated with high PM values.

These findings offer a deeper understanding of the complexity of emissions from rice straw burning and provide a solid foundation for future mitigation strategies and the development of environmental policies in affected regions.

 

This work is part of a project that is supported by ATMOBE  PID2022-1423660B-100 funded by MCIN/AEI/ 10.13039/501100011033 and,  by “ERDF A way of making Europe” and by PROMETEO (EVER project) CIPROM/20200/37