SPATIALLY RESOLVED MONITORING FOR VOLATILE ORGANIC-COMPOUNDS USING REMOTE SECTOR SAMPLING

Sector sampling for volatile organic compounds (VOCs) is conducted wit hin an integrated sampling scheme and relies on a wind direction senso r. The wind sensor directs whole air, sampled at a constant rate, into either an ''IN'' sector canister or an ''OUT'' sector canister; when the wind comes from the suspected emissions area, sample is routed int o the IN sector canister, otherwise, sample is collected in the OUT se ctor canister. This method is analogous to ''upwind/downwind'' samplin g but does not require two distinct sites or manual sampler control. F or this set of experiments, the IN and OUT sectors were 90 and 270-deg rees, respectively, and the IN sector was centered on the VOC source. Two sampling sites were used. The first was about 2 miles north-northe ast of a group of industrial facilities, and the second was located ab out 1 mile south-southeast of the same sources. Sites were operated co ncurrently with one sampler each; a third sampler was rotated between the sites to obtain duplicate samples. The air samples were analysed b y gas chromatography for VOCs. The resultant data comparisons between IN and OUT duplicate samples show good correlation with expected VOC e missions, which were determined by grab samples within the target area . A t-test method for interpreting the sometimes subtle differences be tween IN and OUT sample data is presented.