PNNL

Abstract

The Pacific Northwest National Laboratory (PNNL) operates a number of multidisciplinary laboratory research facilities for the U. S. Department of Energy and has sampled air chemical emissions from some of these facilities since 1998. The primary purpose of this sampling is to obtain data to compare estimated release fractions to those used for emissions estimates, verifying that methods used to determine compliance with air regulations and permits conservatively predict actual emissions. Sampling is also used to identify and quantify the air toxics emitted during normal working hours and to compare these emissions to compliance limits established by regulatory agencies. Hundreds of samples have been taken from four different multi-purpose laboratories over a 10-year time period. Results from initial sampling campaigns were evaluated and reported by Woodruff, Benar, and McCarthy (2000) who summarized the compliance approach used by PNNL and described sampling and analytical measurements for the first sampling campaigns. Conclusions reported at this time were that none of the measurements of the target compounds exceeded an acceptable source impact level (ASIL) (Washington Administrative Code, Chapter 173-460) even using significant overestimation factors, and that an average release fraction calculated from the data provided reasonable validation of the factor used in compliance assessments. A statistical analysis of the full data set is being conducted to obtain a better understanding of releases from R&D facilities including uncertainties, confidence intervals, and the relationship of release concentrations to chemical inventories or processes. This is intended to be a more in-depth investigation of release fractions with possible development of predictor source term models that include chemical and process properties (e.g. vapor pressure, temperature). One aspect of this analysis is to determine if emissions are significantly different for separate R&D facilities or if there is a commonality so that the data can be analyzed as a single group. The data set from air chemical sampling from 1998 through 2007 was analyzed to identify the chemical signature from each laboratory and determine how this signature differed by sampling location. Sampling locations included stacks from each of the four research facilities and non-stack locations such as lobbies and corridors which represent background concentrations of the volatile organic carbon (VOC) compounds being measured. For this analysis, the chemical signature was defined as the detection proportion of the VOCs analyzed. A simple metric was developed to quantitatively compare the chemical detection proportions from different locations or groups of locations. This metric is useful in comparing the combination of chemicals that have been detected in stack sampling, but not in comparing relative concentrations of those chemicals.