Soil Nitric Oxide Emissions: Lab and Field Measurements and Comparison

Abstract

Equipment and procedures are developed and implemented to measure nitric oxide (NO) emissions from unamended and municipal wastewater treatment plant biosolids-amended soil in controlled laboratory experiments and in situ field experiments. NO plays an important role in the formation of tropospheric ozone. Minimization of NO flux from soil is advantageous, protecting air quality as well as conserving valued nitrogen fertilizers. Controlled laboratory and in situ field measurements of soil NO flux were conducted on similar soil types under similar water-filled pore space (WFPS) and temperature conditions. The difference in NO emissions between the lab and the field measurements was statistically significant within the WFPS range (18.1 to 45.3%) and temperature range (12 to 28°C) studied. The soil NO flux measured in the lab ranged from 2.5 to 62.9 ng-N/m²s) compared to 2.8 to 128.1 ng-N/(m²s) for field measurements. The NO flux from biosolids amended soil was significantly higher than unamended soil. Temperature relationships modeling NO flux for the lab and field experiments are developed and compared to the EPA's BEIS2 model.