Spatially resolved monitoring for volatile organic compounds using remote sector sampling

Sector sampling for volatile organic compounds (VOCs) is conducted within an integrated sampling scheme and relies on a wind direction sensor. 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 into the IN sector canister; otherwise, sample is collected in the OUT sector canister. This method is analogous to “upwind/downwind” sampling but does not require two distinct sites or manual sampler control. For this set of experiments, the IN and OUT sectors were 90 and 270°, respectively, and the IN sector was centered on the VOC source. Two sampling sites were used. The first was about 2 miles north-northeast of a group of industrial facilities, and the second was located about 1 mile south-southeast of the same sources. Sites were operated concurrently with one sampler each; a third sampler was rotated between the sites to obtain duplicate samples. The air samples were analysed by gas chromatography for VOCs. The resultant data comparisons between IN and OUT duplicate samples show good correlation with expected VOC emissions, which were determined by grab samples within the target area. A t-test method for interpreting the sometimes subtle differences between IN and OUT sample data is presented.