Non–methane hydrocarbon emission profiles from printing and electronic industrial processes and its implications on the ambient atmosphere in the Pearl River Delta, South China

Thirty–seven non–methane hydrocarbons (NMHCs) were quantified for seven industrial work processes, covering the electronic industry and the printing industry, in the Pearl River Delta (PRD). NMHC source profiles (% by wt.) for the respective work processes and their associated industrial solvents were obtained. In order to examine the contribution of the individual work processes to the neighborhood atmospheres, ambient samples on the rooftop of the printing and electronic factories were collected. Total NMHC concentrations of 3 700 ± 740 ppbv and 169 ± 64 ppbv were detected, respectively. Air samples from roadside of a main roundabout, from rooftop of a residential building in the town center and from a background site were also collected to examine the impact of industrial and vehicular emissions on local NMHC levels. NMHC emissions from the printing factory were significantly higher than that from the electronic factory. The two work processes, plastic molding and soldering in the electronics factory, emitted mainly C3–C7 alkanes, while paint solvents used in the printing factory released C7–C8 aromatics. Toluene was the most abundant NMHCs measured for all work processes in the printing factory. It was due to the heavy usage of various solvent–based inks and paint solvents. In general, high toluene levels were found in the ambient and industrial–related atmosphere and this led to low benzene–to–toluene ratios (B/T, ppbv/ppbv) in this study. The B/T ratios for urban, suburban and roadside ambient atmospheres were smaller than 0.2. Much lower ratios (<0.04) were measured for industrial work processes associated with usage of ink and paint solvents. Our study suggests that toluene–rich emission from the printing industry contributes to the gradual increase in the atmospheric toluene background in the PRD.