Project Number: 1265-32420-004-02
Project Type: Reimbursable

Start Date: Jul 01, 2007
End Date: May 03, 2008

Objective:
1) Determine the concentrations of viable E. coli and fecal indicator/pathogen microbes (FIM) in ambient air and in particulate depositions at and downwind of composting and livestock/animal operations in the California Central Coast region during typical unit operations. 2) Analyze survival of bioaerosol and deposited E. coli and FIMs relative to compost/manure matrix moisture content and other unit operation and environmental factors associated with the bioaerosol sources and the atmospheric/environmental conditions.

Approach:
Animal and compost production facilities are known sources of airborne particulates and bioaerosols, but emission rates, transport, survival and deposition of particulates containing E. coli and FIMs from these sources currently are not clearly quantified or estimable from existing data. Current grower association metrics for lettuce and leafy greens require set-back distances ranging from 30 to 400 feet between crop fields and adjacent compost and livestock fields/operations. Data are needed to assess the adequacy and appropriateness of these distances relative to environmental conditions that may influence survival and deposition of bioaerosol particles on lettuce. The proposed project focuses on conducting an initial study of concentrations of viable E. coli and FIMs in airborne particulates generated during typical livestock production operations at cattle yards, housing facilities, and pastures, including wind, animal, and vehicle entrainment of surface particles and manure management activities. At compost sites, bioaerosol assessments will focus on all unit operations and vehicular movements leading to air entrainment of particulates and their off-site transport. Measured microbial content of airborne particulates (< 100 mm aerodynamic diameter) per mg will provide a link to existing data on total suspended particulates for livestock operation emissions, and hence future transport model calculations. Survival of E. coli in airborne compost/manure particulates will be analyzed relative to substrate moisture, RH, solar radiation intensity, temperature, and wind conditions at field sites and in controlled laboratory tests. Samples will include a range of atmospheric stability classes, seasons of year, and times of day. Results will provide data sufficient to indicate which types of operations generate target bioaerosol depositions at 30-400 ft.