FINE PARTICULATE ORGANIC MATERIAL IN THE LOS-ANGELES BASIN - I - ASSESSMENT OF THE HIGH-VOLUME BRIGHAM-YOUNG-UNIVERSITY ORGANIC-SAMPLING SYSTEM, BIG BOSS

A multi-system, high-volume, parallel plate diffusion denuder Brigham Young University Organic Sampling System (BIG BOSS) was tested using c ollocated samplers at the Pico Rivera Monitoring Station of the South Coast Air Quality Management District, South Coast Air Basin, in Septe mber 1994. Six-hr daytime and 9-hr nighttime samples were collected wi th a how of about 200 L/min through each of the three systems designed to collect particles smaller than 2.5, 0.8, and 0.4 mu m in a diffusi on denuder sampler. Efficiency for the removal of gas phase organic co mpounds by the diffusion denuder was evaluated using both theoretical predictions and field measurements. Both measured and calculated data indicate high denuder efficiency for the removal of gas phase aromatic and paraffinic compounds. The precision of the BIG BOSS was evaluated using collocated samplers. The precision of determination of total ca rbon and elemental carbon retained by a quartz filter or of semi-volat ile carbonaceous material lost from particles during sampling averaged +/-7%. The precision of determination of individual organic compounds averaged +/-10%. An average of 42 and 62% of the particulate organic material was semi-volatile organic compounds (SVOCs) lost from particl es during sampling for daytime and nighttime samples, respectively. Th is ''negative'' sampling artifact was an order of magnitude larger tha n the ''positive'' quartz filter artifact due to adsorption of gas pha se organic material. Daytime concentrations of fine particulate elemen tal carbon and nonvolatile organic carbon were higher than nighttime c oncentrations, but nighttime fine particles contained more semi-volati le organic material than daytime.