Determination of ammonia and hydrogen sulfide emissions from a commercial dairy farm with an exercise yard and the health-related impact for residents

Abstract

Airborne emissions from concentrated animal feeding operations (CAFOs) have the potential to pose a risk to human health and the environment. Here, we present an assessment of the emission, dispersion, and health-related impact of ammonia and hydrogen sulfide emitted from a 300-head, full-scale dairy farm with an exercise yard in Beijing, China. By monitoring the referred gas emissions with a dynamic flux chamber for seven consecutive days, we examined their emission rates. An annual hourly emission time series was constructed on the basis of the measured emission rates and a release modification model. The health risk of ammonia and hydrogen sulfide emissions around the dairy farm was then determined using atmospheric dispersion modeling and exposure risk assessment. The body mass-related mean emission factors of ammonia and hydrogen sulfide were 2.13 kg a^-1 AU^-1 and 24.9 g a^-1 AU^-1, respectively (one animal unit (AU) is equivalent to 500 kg body mass). A log-normal distribution fitted well to ammonia emission rates. Contour lines of predicted hourly mean concentrations of ammonia and hydrogen sulfide were mainly driven by the meteorological conditions. The concentrations of ammonia and hydrogen sulfide at the fence line were below 10 μg m^-3 and 0.04 μg m^-3, respectively, and were 2-3 orders of magnitude lower than the current Chinese air quality standards for such pollutants. Moreover, the cumulative non-carcinogenic risks (HI) of ammonia and hydrogen sulfide were 4 orders of magnitudes lower than the acceptable risk levels (HI = 1). Considering a health risk criterion of 1E-4, the maximum distance from the farm fence line to meet this criterion was nearly 1000 m towards north-northeast. The encompassed area of the contour lines of the ambient concentration of ammonia is much larger than that of hydrogen sulfide. However, the contour lines of the ammonia health risk are analogous to those of hydrogen sulfide. In general, the ammonia and hydrogen sulfide emissions from the dairy farm are unlikely to cause any health risks for the population living in the neighborhood.

Keywords: Ammonia; Dairy farm; Dispersion model; Emission; Health risk; Hydrogen sulfide.

Fig. 1

Location and surrounding of the dairy farm. a Feedlot pens (including cowshed and exercise yard); b silage storage; c1 village 1; c2 village 2, c3 village 3; pentagram stands for the sampling site

Fig. 2

Empirical cumulative distribution function of the measured body mass-specific emission factor e_M,meas (kg a⁻¹ AU⁻¹) and the body mass-specific reference emission factor e_M,0 (kg a⁻¹ AU⁻¹) for the NH₃ emissions from the dairy farm for the field measurements. Black lines show the theoretical log-normal distributions. The mean value of the measured emission factor e_M,meas is 2.13 kg a⁻¹ AU⁻¹; the mean reference emission factor e_M,0 is 0.672 kg a⁻¹ AU⁻¹ (Table 1)

Fig. 3

Time course of the ammonia emission rate E (mg s⁻¹) calculated by the body mass-specific emission factor e_M,0 = 0.672 kg a⁻¹ AU⁻¹ and the total body mass inside the barn of M = 360 AU, calculated for the 2017 meteorological dataset of the Haidian station by the release modification factor R₁₇. The field measurements are shown in red. The annual mean value is 11.3 mg s⁻¹ shown by the black line. Panel A is linearly, panel B logarithmically diagramed

Fig. 4

Contour plot of hourly mean concentrations of ammonia in the surrounding area of the dairy farm. The black circle stands for the fence line of the farm, and the red rectangle stands for the feedlot pen areas

Fig. 5

Contour plot of hourly mean concentrations of hydrogen sulfide in the surrounding area of the dairy farm. The black circle stands for the fence line of the farm, and the red rectangle stands for the feedlot pen areas

Fig. 6

Contour plot of the criterion for non-carcinogenic risk HI of ammonia in the surrounding area of the dairy farm. The farm fence line is depicted in the center of the plot

Fig. 7

Contour plot of the criterion for non-carcinogenic risk HI of hydrogen sulfide in the surrounding area of the dairy farm. The farm fence line is depicted in the center of the plot

Fig. 8

Contour plot of the criterion for cumulative carcinogenic risk (∑HI) of ammonia and hydrogen sulfide in the surrounding area of the dairy farm. The farm fence line is depicted in the center of the plot