Environmental monitoring and spatial assessment of atmospheric ammonia levels near hog CAFOs and human receptor sites in eastern North Carolina

Hog concentrated animal feeding operations (CAFOs) release contaminants to the atmosphere including ammonia (NH3), hydrogen sulfide, VOCs, and particulate matter. Most of these operations are found in the coastal plain of the state and can create potential health hazards for nearby human populations. Limited work has been performed to measure, map, and estimate NH3 at the community level to assess potential human exposure. In an effort to address this issue, a study was designed to characterize NH3 levels near hog CAFOs and human receptor sites in Eastern North Carolina.; NH3 was collected using passive diffusion tubes in triplicate set for one week at a time. Sampling occurred continuously from October 2003 to May 2004 (twenty sites) and from July 2004 to October 2004 (twenty-three sites) at varying distances from hog CAFOs in close proximity to human receptor locations (homes and schools). Average weekly NH3 levels were measured as mass (mug NH3-N) and converted to concentration (ppb). Mean levels near human receptor locations (less than 2 km) were 4 to 12 times greater than ambient background levels (1-3 ppb), reaching as high as 80 ppb. Exposed sites (less than 2 km from a hog CAFO) had mean levels which were three times higher than less exposed sites (greater than 2 km from a hog CAFO). Statistical analyses confirmed that source terms such as distance to a hog CAFO and liveweight per operation, as well as temperature, wind speed and wind direction were important predictors of NH3 levels.; The study established that passive sampling in conjunction with GIS methodologies could effectively show NH3 variation in space. ArcGIS 8.3 and the BME framework were utilized to map and estimate ammonia levels using interpolation methods (e.g. kriging and cokriging). The collected data and constructed maps act as indicators of relative exposure for human populations who live near a hog CAFO. The closer a populace is to the hog CAFO, the more intense the exposure. The study confirms potential NH3 exposure for human populations near hog CAFOs and suggests the possibility of using NH3 as a marker for other contaminants.