MEASUREMENTS OF NITRIC-OXIDE FLUX FROM AN UPPER COASTAL-PLAIN, NORTH-CAROLINA AGRICULTURAL SOIL

Agricultural soil NO flux measurements (using a dynamic chamber technique) were made from 18 August to 1 September 1993 in the Upper Coastal Plain region of North Carolina in an effort to determine the role of natural emissions of NO on rural atmospheric photochemistry. Overall average NO flux rates increased proportionally to the level of applied fertilizer nitrogen in the agricultural soil. The soybean, cotton, and corn field measurements revealed an average NO flux of 1.79 (range - 1.0-6.9) ng N m(-2) s(-1); 3.77 (range - 0.1-38.0) ng N m(-2) s(-1); and 8.05 (range - 0.5-52.8) ng N m(-2) s(-1) respectively. There was a positive correlation between NO concentration near the soil surface (similar to 50 cm) and NO flux. A significant negative correlation between NO flux and ambient O-3 concentration, however, supports the hypothesis that soil emissions of NO contribute to local production of O-3 in rural areas.