Does Ammonia Deposition From Poultry Barn Exhaust Contribute to Soil Nitrate Contamination?.

The Abbotsford-Sumas aquifer of BC and Washington State is an important source of drinking water that frequently has elevated levels of nitrate. Intensive production of both berries and poultry is thought to contribute to the elevated nitrate in the aquifer. The objectives of this study are to determine if dry deposition of ammonia from poultry barn exhaust contributes to nitrate leaching. To determine this, ammonia emissions from broiler (meat bird) barns; dry deposition rates of ammonia around the poultry barns; and concentration of nitrate in soil water near the barns are quantified. The total barn ventilation rate is determined by timing fan activity and flow rates predetermined with a mobile anemometer system. The concentration of ammonia in the exhaust is measured with impingers. Dry deposition is measured with soil adsorption traps arranged in a grid around the barns. Emission and deposition are sampled weekly over 24-hour periods for one year (6 production cycles). Nitrate concentrations in the soil solution are measured in samples from tension lysimeters, installed at 45 cm depth in a grid pattern. Preliminary analysis of one growth cycle in two barns shows emission factors of 0.39 and 0.40 g NH₄-N bird^-1 day^-1. The emissions increase dramatically through the cycle, and are expected to vary seasonally. Deposition levels reach 4.4% of the total emissions and water collected with the lysimeters shows NO₃-N concentrations exceeding 250 mg kg^-1 at 2.1 m and 125 mg kg^-1 at 3.6 m from the fans. A water balance model will be used to estimate nitrate flux from the lysimeter measurements. The data will be up-scaled spatially according to poultry distribution to determine potential of dry ammonia deposition to contribute to nitrate contamination of the aquifer.