A Passive Sampler for the Determination of Airborne Ammonia Concentrations near Large-Scale Animal Facilities

Abstract

Few data are available on the ammonia emissions of large-scale outdoor animal facilities in arid climates such as those found in California's San Joaquin Valley. Passive samplers provide an ideal tool for studying such large and heterogeneous area sources, because they are inexpensive, portable, and fully self-contained. UC Davis passive ammonia samplers incorporate modifications on a previous design, the Willems Badge, for ease of analysis. Citric acid was chosen as a coating medium though it performed as well as oxalic, sulfuric, and tartaric acids. Zefluor PTFE prefilters were used instead of Teflo though both showed the same resistance to diffusion. Citric acid-coated filters were stable for up to 10 weeks, though more so if stored in Petri dishes rather than in the sampling cassettes themselves. The most effective sampler position was found to be in a face-down configuration fixed into the wind to avoid debris and sensitivity to wind shifts. A new method of rinsing the filters within the cassettes by dropwise elution proved highly effective, with 85% of the ammonium being removed in the first 3 mL of the 10-mL rinse volume. Application of the sampler at a dairy in the Joaquin Valley revealed large variations in concentrations at different locations along the downwind fenceline, which correlated with animal populations and activities directly upwind. In addition, large variations in ammonia concentrations were observed in relation to time of day and animal activity. Field blank loadings were of 1.40 microg NH4-N/filter (SD = 0.74 microg NH4-N/filter). Replicate passive samplers placed side-by-side during sampling episodes agreed with a slope of 1.010 (standard error = 0.028). Impingers were used as a reference method to obtain the correlation between filter loadings and air concentrations, yielding an "effective sampling rate" for the passive samplers of 6.18 L/h (error = 0.23 L/h). Using a theoretical calculation, that "effective flow rate" was calculated to be 6.29 L/h. The method's limit of detection was found to be 82.5 microg NH4-N/m3. Wind speed was found to theoretically affect linearity of sampler response only for speeds less than 0.92 m/s.

Measuring Ammonia Concentrations and Emissions from Agricultural Land and Liquid Surfaces: A Review

“…In passive filter packs (no forced air), ammonia in the air is transported by diffusion to the filter where it forms a salt with the acid; in forced-air filter packs, convective flow transports ammonia. Rabaud et al 21 found no difference in performance among filters coated with citric acid, oxalic acid, tartaric acid, or H 2 SO 4 , but weak citric acid-ammonia bond reduced ammonia trapping in denuders 22 (discussed later). After the experiment, the filter is eluted, and the eluent is analyzed for NH 4 ϩ .…”

“…Based on design, preparation, and analytical methods, filter packs have DLs of 0.2-2.8 g/filter 21,23,24 where the DL was 2-3 standard deviations (SDs) in the field blanks. The saturation limit of a filter pack is much lower than its stoichiometric capacity because of reduced mass transfer to the deeper, unsaturated layer through a "saturated" surface layer.…”

Ammonia Emission Factors for Open-Lot Dairies: Direct Measurements and Estimation by Nitrogen Intake

“…Passive filter packs, adapted from Willems badges, 24 consisted of citric acid-coated Whatman filters supported 2 m above ground in 37-mm Gelman filter holders with 2-m pore size Teflon prefilters. 25 Passive filter samplers were collocated with all reference samplers. Linear regression of the rate of NH 3 -N accumulation in the passive filter (field blank corrected mass of NH 4 -N divided by time of exposure) to the air NH 3 -N concentrations measured by the reference method, for non-zero data, provided a slope and error of the slope for the best fit line through the data points and the origin.…”

Simple approaches for measuring dry atmospheric nitrogen deposition to watersheds

“…In response to this challenge, we sought a more affordable method and designed a passive HNO 3 sampler from commercially available monitoring cassettes that are specified for vacuum sampling of particulate matter and gases for industrial hygienic sampling. Our sampler conceptually follows Bytnerowicz et al [2005] and is similar in appearance to Rabaud et al [2001] (Figure 1). Table 2 provides a complete listing of sampler components and prices as of June 2008.…”