Dynamic Flow-through Chamber System Research Articles

Modeling Ammonia Emissions from Broiler Litter at Laboratory Scale

The objectives of this study were to develop a mechanistic emission model to estimate ammonia flux from broiler litter and to evaluate the model at laboratory scale. In the proposed model, the ammonia flux is essentially a function of the litter's total ammoniacal nitrogen (TAN) content, moisture content, pH, and temperature, as well as the Freundlich partition coefficient (Kf), mass transfer coefficient (KG), ventilation rate (Q), and emission surface area (A). The Freundlich partition coefficient (Kf) was used as a fitting parameter in the model. A dynamic flow-through chamber system and a wind tunnel were designed to measure ammonia fluxes from broiler litter. The dynamic flow-through chamber experiments evaluated the proposed model with various litter samples under a constant temperature and wind profile. The wind tunnel experiments evaluated the proposed model under various temperatures and wind profiles. Model parameters such as Kf and KG were estimated. The results from the two experiments were consistent with each other. The estimated KG ranged from 1.11 to 27.64 m h-1, and the estimated Kf ranged from 0.56 to 4.48 L kg-1. A regression sub-model was developed to estimate Kf as function of litter pH and temperature, which indicated that Kf increased with increasing litter pH and decreased with increasing temperature. The proposed model was used to estimate the equilibrium gas phase ammonia concentration (Cg,0) in litter, and the model-predicted values were compared with the observed values. The normalized mean error (NME), the normalized mean square error (NMSE), and fractional bias (FB) were calculated to be 25%, 12%, and -0.3%, respectively, for all 94 measurements, and the model was able to reproduce 80% of the variability of the data. Sensitivity analysis of the model showed that ammonia flux is very sensitive to litter pH and to a lesser extent temperature. The relative sensitivity of pH or temperature increases as the pH or temperature increases.

Effect of moisture content on ammonia emissions from broiler litter: A laboratory study

A dynamic flow-through chamber system was designed to measure ammonia emissions from broiler litter and to investigate the responses of ammonia emissions to litter moisture content under laboratory-controlled conditions. It was observed that ammonia emissions from litter were very sensitive to litter moisture content. As water was added to the litter, the total ammoniac nitrogen content (TAN) in the litter increased, and can potentially increase ammonia emissions. However, measurements of ammonia concentrations in the chamber and total nitrogen losses from litter samples all suggested that water applied to the litter also had an effect of suppressing ammonia emissions for a short time. After enough time (1 to 2 weeks) was allowed, higher moisture content in litter eventually resulted in higher ammonia emissions. It was also noticed that, at very high litter moisture content, even when more time was allowed, ammonia concentrations began to decrease as moisture content further increased.

Characterizing ammonia and hydrogen sulfide emissions from a swine waste treatment lagoon in North Carolina

Emissions of atmospheric ammonia–nitrogen (NH 3-N, where NH 3-N=(14/17)NH 3) and hydrogen sulfide (H 2S) from a commercial anaerobic swine waste treatment lagoon (17,150 m 2 at normal liquid level) were measured over a 1-year period. Continuous simultaneous measurements were made at the lagoon using a dynamic flow-through chamber system for ∼1 week during four seasons, October–November 2004 (fall), February 2005 (winter), April 2005 (spring), and June 2005 (summer) in an effort to examine diurnal and seasonal variability, and the respective relationships of NH 3-N and H 2S emissions to lagoon physicochemical properties. Continuously measured lagoon physicochemical parameters include lagoon surface temperature and lagoon pH. Aqueous lagoon samples were collected daily and analyzed for total Kjeldahl nitrogen (TKN), total ammoniacal nitrogen (TAN), and total sulfide concentration. TKN, TAN, and sulfide concentrations ranged from 400–650, 360–590, and 0.1–13.0 mg L −1, respectively. For NH 3-N, the largest fluxes were observed during the summer (>4200 μg N m −2 min −1). During the fall and spring, average NH 3-N fluxes were 1634±505 and >2495 μg N m −2 min −1, respectively. The lowest fluxes were observed during the winter where average flux values were 1290±246 μg N m −2 min −1. Fluxes for H 2S were negligible during the winter season. Average fluxes increased during the fall (0.3±0.1 μg m −2 min −1) and spring (0.5±1.0 μg m −2 min −1), and highest flux values were observed during the summer (5.3±3.2 μg m −2 min −1). The seasonal NH 3-N and H 2S emission factors ranged from ∼10 to ∼40 kg N AU −1 yr −1 (1 AU=500 kg live animal weight) and ∼0 to ∼0.05 kg H 2S AU −1 yr −1, respectively. Generally, the lagoon emissions for H 2S were ∼3–4 orders of magnitude less than NH 3-N. The gas fluxes were related to various physicochemical parameters including the pH and near-surface temperature of the lagoon, and the aqueous concentration of the respective gas.

Dynamic atmospheric chamber systems: applications to trace gas emissions from soil and plant uptake

Atmospheric emissions, transport, transformation and deposition of trace gases may be simulated through chambers. The dynamic flow-through chamber system has been developed in response to a need to measure emissions of nitrogen, sulphur and carbon compounds for a variety of field applications. Oxides of nitrogen (NO, NO2, NOY) emissions have been measured from agricultural fertilised/unfertilised soils. Ammonia-nitrogen (NH3–N) and reduced organic sulphur compound emissions have been measured using this same technique across a gas-liquid and soil-atmosphere interface at swine waste treatment anaerobic storage lagoons and in agricultural fields. Similar chamber systems have also been deployed to measure the uptake of nitrogen, sulphur, ozone and hydrogen peroxide gases by crops and vegetation to examine atmospheric-biospheric interactions. Emission measurements compare well with a coupled gas-liquid transfer with chemical reaction model as well as a US Environmental Protection Agency (EPA) WATER9 model.

Modeling of Ammonia Emissions from Soils

Using a dynamic flow-through chamber system in conjunction with a Thermo Environmental 17C Chemiluminescence ammonia (NH3) analyzer, emissions from slurry-amended, that is, effluent from the lagoon (∼33 kg N ha-1) and nonamended soils were calculated at a swine farm in eastern North Carolina. The average NH3-N flux values during the period when the soils were not amended with any slurry were ∼54 ng N m-2 s-1, while the average NH3-N flux values measured immediately following the application of slurry to the soil were 1723.9 ng N m-2 s-1. An empirical model relating soil temperature to NH3 flux for nonamended soils explained over 70% of the variability in NH3 emissions; however, a similar empirical model relating soil temperature to NH3 flux for slurry-amended soils was able to explain only 39% of the variability in NH3 emissions. A mass transport model, based on physical and chemical processes to estimate NH3 emissions from recently amended soils is also presented and compared and contrasted to the empirical model. The variables used in the mechanistic model are pH, soil temperature, and total ammoniacal nitrogen content. When using the mass transport model, the percentage difference between predicted and measured values for the nonamended and slurry-amended soils were 164 and 16%, respectively, indicating that the mechanistic model is only applicable for periods when nitrification/denitrification, plant uptake, and immobilization are small enough in comparison to the chemical and physical processes following slurry application that they can be ignored. The percentage of the nitrogen (N) applied, which was emitted as NH3, increased at its greatest rate immediately following slurry application (1–2 days) and then began to level out at a value of approximately 20% by day 4. Previous laboratory studies found these volatilization events to be short lived (few days–2 weeks), and this study corroborates those findings.

Modeling nitric oxide emissions from biosolid amended soils

Utilizing a state-of-the-art mobile laboratory in conjunction with a dynamic flow-through chamber system, nitric oxide concentrations [NO] were measured and NO fluxes were calculated during the summer, winter and spring of 1999/2000. The field site where these measurements were conducted was an agricultural soil amended with biosolids from a municipal wastewater treatment facility. These NO flux values were then used to assess the impact of including biosolid amended soils as a land-use class in an air quality model. The average NO flux from this biosolid amended soil was found to be exponentially dependent on soil temperature [NO Flux ( ng N m −2 s −1)=1.07 exp(0.14 T soil ) ; R 2=0.81—NO Flux=71.3 ng N m −2 s −1 at 30°C]. Comparing this relationship to results of the widely applied biogenic emissions inventory system (BEIS2) model revealed that for this field site, if the BEIS2 model was used, the NO emissions would have been underestimated by a factor of 26. Using this newly developed NO flux algorithm, combined with North Carolina Division of Water Quality statistics on how many biosolid amended acres are permitted per county, county-based NO inventories from these biosolid amended soils were calculated. Results from this study indicate that county-level biogenic NO emissions can increase by as much as 18% when biosolid amended soils are included as a land-use class. The multiscale air quality simulation platform (MAQSIP) was then used to determine differences in ozone (O 3) and odd-reactive nitrogen compounds (NO y ) between models run with and without the biosolid amended acreages included in the inventory. Results showed that during the daytime, when atmospheric mixing heights are typically at their greatest, any increase in O 3 or NO y concentrations predicted by the model were small (<3%). In some locations during late evening/early morning hours, ozone was found to be consumed by as much as 11%.

Characterization of ammonia emissions from soils in the upper coastal plain, North Carolina

A dynamic flow-through chamber system was used to measure fluxes of ammonia-nitrogen (NH 3-N, where NH 3-N=(14/17)NH 3) from soil surfaces. The research site was located in eastern North Carolina (35.9°N latitude; 77.7°W longitude) and measurements were conducted during spring and winter 2000, in order to assess the NH 3 source strength of intensively managed agricultural soils and the physiochemical properties which control these emissions. Soil temperature ( T soil), soil pH, soil moisture, total Kjeldahl nitrogen (TKN=organic N+NH 3-N+NH 4 +-N) were monitored throughout both research periods. Soil temperature was found to explain the largest variability in soil NH 3 emissions (Log 10 NH 3-N Flux=0.054 T soil+0.66; R 2=0.71), suggesting that an approach similar in design to the biogenic emissions inventory system land use and temperature model for NO emissions, might be effective for modeling biogenic NH 3 emissions. Soil nitrogen was also significant in predicting NH 3 flux [NH 3 Flux=55.5(NH 3-N)−160, R 2=0.86; NH 3 Flux=0.6(TKN)−410, R 2=0.27], but only after the two days with the heaviest rainfall were removed from the regression, emphasizing the role of soil moisture in controlling the transfer of gases across the soil/air interface. Soil pH remained relatively constant throughout both research periods and therefore did not serve as a useful predictor of NH 3 flux. A rain event, followed by a drying period produced a characteristic pulse in ammonia emissions. This pulsing phenomenon has been observed for other trace gases by various researchers. This research location was the site of a commercial hog operation, which allowed for the comparison of soil and lagoon emissions (lagoon emissions were based on an algorithm developed by Aneja et al. (J. Geophys. Res. 105 (2000) 11,535). An analysis of the source strengths confirmed that lagoon emissions are a larger flux source (average lagoon flux ∼18,137 ng N m −2 s −1; average soil flux ∼54 ng N m −2 s −1); however soil surfaces make up a larger fraction of a commercial hog operation than the lagoon surfaces, and as a result they cannot be neglected when developing and apportioning NH 3 emissions. A yearly average of ammonia emissions at this site revealed that soil emissions represent approximately 28% of the lagoon emissions.

Nitric oxide emissions from soils amended with municipal waste biosolids

Land spreading nitrogen-rich municipal waste biosolids (NO 3 −-N<256 mg N kg −1 dry weight, NH 3-N∼23,080 mg N kg −1 dry weight, Total Kjeldahl N∼41,700 mg N kg −1 dry weight) to human food and non-food chain land is a practice followed throughout the US. This practice may lead to the recovery and utilization of the nitrogen by vegetation, but it may also lead to emissions of biogenic nitric oxide (NO), which may enhance ozone pollution in the lower levels of the troposphere. Recent global estimates of biogenic NO emissions from soils are cited in the literature, which are based on field measurements of NO emissions from various agricultural and non-agricultural fields. However, biogenic emissions of NO from soils amended with biosolids are lacking. Utilizing a state-of-the-art mobile laboratory and a dynamic flow-through chamber system, in-situ concentrations of nitric oxide (NO) were measured during the spring/summer of 1999 and winter/spring of 2000 from an agricultural soil which is routinely amended with municipal waste biosolids. The average NO flux for the late spring/summer time period (10 June 1999–5 August 1999) was 69.4±34.9 ng N m −2 s −1. Biosolids were applied during September 1999 and the field site was sampled again during winter/spring 2000 (28 February 2000–9 March 2000), during which the average flux was 3.6±1.7 ng N m −2 s −1. The same field site was sampled again in late spring (2–9 June 2000) and the average flux was 64.8±41.0 ng N m −2 s −1. An observationally based model, developed as part of this study, found that summer accounted for 60% of the yearly emission while fall, winter and spring accounted for 20%, 4% and 16% respectively. Field experiments were conducted which indicated that the application of biosolids increases the emissions of NO and that techniques to estimate biogenic NO emissions would, on a yearly average, underestimate the NO flux from this field by a factor of 26. Soil temperature and % water filled pore space (%WFPS) were observed to be significant variables for predicting NO emissions, however %WFPS was found to be most significant during high soil temperature conditions. In the range of pH values found at this site (5.8±0.3), pH was not observed to be a significant parameter in predicting NO emissions.

Biogenic nitric oxide emissions from cropland soils

Emissions of nitric oxide (NO) were determined during late spring and summer 1995 and the spring of 1996 from four agricultural soils on which four different crops were grown. These agricultural soils were located at four different sites throughout North Carolina. Emission rates were calculated using a dynamic flow-through chamber system coupled to a mobile laboratory for in-situ analysis. Average NO fluxes during late spring 1995 were: 50.9±47.7 ng N m −2 s −1 from soil planted with corn in the lower coastal plain. Average NO fluxes during summer 1995 were: 6.4±4.6 and 20.2±19.0 ng N m −2 s −1, respectively, from soils planted with corn and soybean in the coastal region; 4.2±1.7 ng N m −2 s −1 from soils planted with tobacco in the piedmont region; and 8.5±4.9 ng N m −2 s −1 from soils planted with corn in the upper piedmont region. Average NO fluxes for spring 1996 were: 66.7±60.7 ng N m −2 s −1 from soils planted with wheat in the lower coastal plain; 9.5±2.9 ng N m −2 s −1 from soils planted with wheat in the coastal plain; 2.7±3.4 ng N m −2 s −1 from soils planted with wheat in the piedmont region; and 56.1±53.7 ng N m −2 s −1 from soils planted with corn in the upper piedmont region. An apparent increase in NO flux with soil temperature was present at all of the locations. The composite data from all the research sites revealed a general positive trend of increasing NO flux with soil water content. In general, increases in total extractable nitrogen (TEN) appeared to be related to increased NO emissions within each site, however a consistent trend was not evident across all sites.

Characterization of biogenic nitric oxide source strength in the southeast United States

Emissions of nitric oxide (NO) were measured during the summer of 1995 from 4 crops, located at three different sites throughout North Carolina. These sites were chosen to represent major physiographic regions of the Southeast US, in an effort to compare fluxes from different agriculturally managed soils. Emission rates were determined using a dynamic flow-through chamber system. In order to understand the NO flux from the different soil and crop types, measurements were made on corn and soybean crops in the coastal region, tobacco in the piedmont region, and corn in the upper piedmont region of North Carolina. Average NO fluxes were 5.5 ± 2.2 ng N m −2 s −1, 20.7 ± 19.2 ng N m −2 s −1, 4.1 ± 1.4 ng N m −2 s −1, and 8.5 ± 4.9 ng N m −2 s −1 respectively for corn and soybean in the coastal region, tobacco in the piedmont region, and corn in the upper piedmont region. We were only able to detect an exponential dependence of NO flux on soil temperature at two of the locations. The composite data of all the research sites revealed a general trend of increasing NO flux with soil water content or increasing extractable nitrogen in the soil, however, the day to day variations within each site did not reveal the same trends. We feel that acquisition of a soil NO flux data set in this fashion, which consists of observations collected over different points in both space and time, makes attempts to model soil NO flux in terms of different soil parameters difficult.