IMPLICATIONSAlthough the urban PM 10 concentrations reported in the AIRS database show a decreasing trend, no decrease was observed for either PM 10 or PM 2.5 concentrations at IM-PROVE sites with continuous records from 1988 to 1993. This may indicate that the regional background is remaining constant.Many of the samples collected at Shenandoah during the summer showed a significant fraction, up to one-half, of the sulfur in particles larger than 2.5 µm. Some sulfur episodes in the East would be missed if PM 10 sampling is replaced by PM 2.5 sampling. This has implications on shifting from a PM 10 to PM 2.5 standard in the East. ISSN 1047-3289 J. Air & Waste Manage. Assoc. 47: 194-203 TECHNICAL PAPER

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The San Joaquin Valley (SJV) in California currently experiences some of the highest surface ozone (O(3)) concentrations in the United States even though it has a population density that is an order of magnitude lower than many urban areas with similar ozone problems. Previously unrecognized agricultural emissions may explain why O(3) concentrations in the SJV have not responded to traditional emissions control programs. In the present study, the ozone formation potentials (OFP) of livestock feed emissions were measured on representative field samples using a transportable smog chamber. Seven feeds were considered: cereal silage (wheat grain and oat grain), alfalfa silage, corn silage, high moisture ground corn (HMGC), almond shells, almond hulls, and total mixed ration (TMR = 55% corn silage, 16% corn grain, 8% almond hulls, 7% hay, 7% bran + seeds, and 5% protein + vitamins + minerals). The measured short-term OFP for each gram of reactive organic gas (ROG) emissions from all livestock feed was 0.17-0.41 g-O(3) per g-ROG. For reference, OFP of exhaust from light duty gasoline powered cars under the same conditions is 0.69 +/- 0.15 g-O(3) per g-ROG. Model calculations were able to reproduce the ozone formation from animal feeds indicating that the measured ROG compounds account for the observed ozone formation (i.e., ozone closure was achieved). Ethanol and other alcohol species accounted for more than 50% of the ozone formation for most types of feed. Aldehydes were also significant contributors for cereal silage, high moisture ground corn, and total mixed ration. Ozone production calculations based on feed consumption rates, ROG emissions rates, and OFP predict that animal feed emissions dominate the ROG contributions to ozone formation in the SJV with total production of 25 +/- 10 t O(3) day(-1). The next most significant ROG source of ozone production in the SJV is estimated to be light duty vehicles with total production of 14.3 +/- 1.4 t O(3) day(-1). The majority of the animal feed ozone formation is attributed to corn silage. Future work should be conducted to reduce the uncertainty of ROG emissions from animal feeds in the SJV and to include this significant source of ozone formation in regional airshed models.

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