Does Proximity of a Field to a Highway Affect Greenhouse Gas Emissions From Soil?.

A field study was conducted to (i) measure carbon dioxide (CO₂) flux from soil in a corn and soybean field and (ii) assess the relationship between soil CO₂ flux and the field proximity to a highway. The study was conducted at Lincoln University’s Freeman farm which is located along Missouri highway 94 (I-94). Forty-eight static and vented chambers were installed in a corn and soybean field at distances of 148, 224, 291, and 362 feet from I-94. Soil air samples were collected between 7:00 and 10:00 a.m every two weeks from August to November 2011. Concentrations of CO₂ from soil air samples were measured with a Shimadzu GC-2014 gas chromatograph.  CO₂ fluxes concentrations were statistically analyzed and mapped using Statistix 9 and ARCGIS 10.0 Geostatistical Analyst Extension, respectively. A Pearson correlation analysis showed that CO₂ flux was significantly correlated with the distance from I-94 at all sampling dates (p<0.05, r=0.33 to 0.71). These correlations were opposite in 7 out of 8 sampling dates, meaning that CO2 flux increased as sampling points were closer to I-94. Resulting maps also showed greater CO₂ flux near the highway with flux decreasing as distance increases away from I-94. These results, although preliminary, suggest that highway traffic may influence soil CO₂ flux along heavily traveled roadways. The study is being pursued to confirm these results.