Application of Receptor Modeling to Indoor Air Emissions from Electroplating

Abstract

In work areas containing multiple sources of the same air pollutant, it is useful for control purposes to be able to separate out the contribution from each individual source. In this study, the chemical mass balance (CMB) receptor model was used to allocate the contributions from multiple sources to area concentration measurements in three electroplating shops. Shop 1 was a room with a single copper electroplating line; shop 2 was a large bay containing a chromium conversion coating line, a continuous chromium electroplating line, and several manual electroplating operations; shop 3 contained a piston chrome plating line, a decorative chrome plating line, and manual and barrel zinc coating lines. Hourly area concentrations of the composition of particulate matter were collected at a number of locations in each workroom. Activities of individual sources within each room were observed and recorded over each 1-hour interval. The receptor modeling approach uses the elemental composition of one or more source categories to determine what fraction of an area sample is contributed by each source. In most cases the CMB model predicted over 90 percent of the measured concentrations. The allocation procedure explained 100 percent of the copper measured at three locations in shop 1, with contributions of 95 to 98 percent from the plating line and the rest from air outside the room. Copper concentrations contributed from plating were consistent with the emission rates determined by other methods. For shop 2, a two-source model explained 100 percent of the chromium measured at five sampling locations. Chromium residuals at two other locations were related to manual line activities not included in the model, which were also likely to involve chromium emissions. For shop 3, the percent contributions of chromium from the piston plating line and the decorative plating line were consistent with distance from each of the sources. Piston line contributions were also consistent with emission rates. Based on these findings, the CMB model is a useful method for allocating specific source contributions to area concentration measurements in spaces containing multiple sources, and the same approach could also be applied to personal samples.