| Abstract
| - California dairies house approximately 1.8 million lactatingand 1.5 million dry cows and heifers. State air regulatoryagencies view these dairies as a major air pollutant source,but emissions data are sparse, particularly for volatileorganic compounds (VOCs). The objective of this work wasto determine VOC emissions from lactating and dry dairycows and their waste using an environmental chamber. Carbondioxide and methane were measured to provide contextfor the VOCs. VOCs were measured by proton-transfer-reaction mass spectrometry (PTR-MS). The compounds withhighest fluxes when cows plus waste were presentwere methanol, acetone + propanal, dimethylsulfide, andm/z 109 (likely 4-methyl-phenol). The compounds withhighest fluxes from fresh waste (urine and feces) weremethanol, m/z 109, and m/z 60 (likely trimethylamine). Ethanolfluxes are reported qualitatively, and several VOCs thatwere likely emitted (formaldehyde, methylamine, dimethylamine) were not detectable by PTR-MS. The sum ofreactive VOC fluxes measured when cows were presentwas a factor of 6−10 less than estimates historically usedfor regulatory purposes. In addition, ozone formationpotentials of the dominant VOCs were ∼10% those of typicalcombustion or biogenic VOCs. Thus dairy cattle have acomparatively small impact on ozone formation per VOCmass emitted.
|
