CAF =

climate adjustment factor for the farm, which represents the extent to which B0 is realized under climatic conditions (e.g., temperature, rainfall) on the farm (note: 0 ≤ CAF ≤ 1); and

Quantitative information in the literature on production of hydrogen sulfide in animal manures is limited. Arogo et al. (2000) developed equations for predicting the production rate of hydrogen sulfide in swine manure storage as a function of time and depth in the manure. However, their study did not account for the influence of different temperatures, manure solid content, and oxygen content. More research is needed to develop accurate prediction models for quantifying the production rate of hydrogen sulfide from different types of manure management systems.

Emission of Hydrogen Sulfide from Animal Manure

Continuous emission of hydrogen sulfide from manure to the atmosphere is controlled by the aqueous chemistry of hydrogen sulfide in the manure and convective mass-transfer mechanisms at the manure surface. The pH, manure temperature, air temperature, wind velocity, and relative humidity are major factors that affect the emission process. The pH controls the partitioning of sulfide among three species, H2S, HS, and S2−. The emission rate of hydrogen sulfide from manure on the kth day can be calculated using the following mass-transfer equation:

(Eq. 5-7)

where KLS is the convective mass transfer coefficient and [S]total is the total sulfide concentration at the manure surface. If the stratification of total sulfide is negligible, [S]total can be assumed to be the total sulfide concentration in the bulk liquid. On any given day, the [S]total,k can be calculated by the concentration at the end of the previous day [S]total,k−1, and the new concentration generated, which can be calculated from generation rate divided by the volume of the liquid in storage (V), as shown below,

(Eq. 5-8)

In Equation 5-7, α is a fraction and can be calculated from the pH and ionization constants Ks,1 and Ks,2 (Arogo et al., 1999):

α = (10−pH)2/[(10−pH)2 + Ks,1 (10−pH) + Ks,1Ks,2],

(Eq. 5-9)

where Ks,1 is the ionization constant for the equilibrium reaction H2S = H+ + HS, and Ks,2 is the constant for HS = H+ + S2−. Their relationships to the temperature in aqueous solutions are well defined. However, the influence of manure charac-



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