Nitric Oxide Emissions from Fertilized and Biosolids-Amended Soil

Abstract

Nitric oxide (NO) emissions from soil amended with municipal wastewater biosolids or mineral fertilizer can adversely impact ozone levels in the lower troposphere and are studied here. A comprehensive laboratory protocol was developed and conducted to consider the influence of biosolids-amended (BSA) soil and mineral-fertilizer-amended (MFA) soil, as compared with unamended soil, on NO emissions with varying temperature, moisture content, and pH. 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. BSA and MFA soils were found to produce NO emissions over five times greater than unamended soils. Distinctions between NO flux from MFA and BSA soil cannot be made. NO flux from soils at pH 6.25 and 6.75 were not found to be statistically different. Soils with higher water-filled pore space (WFPS) and temperature are generally shown to produce greater quantities of NO within the range of temperature (15- 28C) and WFPS (3-40%) studied. INTRODUCTION AND OBJECTIVES Nitric oxide (NO) is the subject of ongoing studies due to its importance in the production of tropospheric ozone and its importance as soil nitrogen (N) is lost to the atmosphere and not available for plant uptake. NO is an important precursor to ozone (O3) formation in the lower atmosphere that can lead to undesirable air quality and detrimental effects on human health. A comprehensive laboratory protocol was developed and conducted to consider the influence of municipal waste- water treatment plant biosolids-amended (BSA) soil and min- eral-fertilizer-amended (MFA) soil, as compared with un- amended agricultural soil, on NO emissions with varying temperature, moisture content, and pH. NO found in the troposphere originates from both natural and anthropogenic sources. Natural sources include emissions from soils, lightning, and forest fires. Anthropogenic sources of NO include motor vehicles and large-scale fossil fuel elec- tric generating facilities. Other sources of NO include am- monia oxidation, aircraft, and input from the stratosphere (Lo- gan 1983). NO is typically found in unpolluted atmospheres