Continuous measurements of nitrous acid (HONO) were performed from December 12 to December 22, 2015 in both urban and suburban areas of Beijing to study the formation mechanism of HONO. The measurement campaign in both sites included a cleanhaze-clean transformation process. HONO concentrations showed similar variations in the two sites, while they were always higher in the urban area. Moreover, correlations of HONO with NO x , NO 2 , NO, PM 2.5 and relative humidity (RH) were studied to explore possible HONO formation pathways, and the contributions of direct emissions, heterogeneous reactions, and homogeneous reactions were also calculated. This showed that HONO in urban and suburban areas underwent totally different formation procedures, which were affected by meteorological conditions, PM 2.5 concentrations, direct emissions, homogeneous reactions and heterogeneous reactions. PM 2.5 concentrations and RH would influence the NO 2 conversion efficiency. Heterogeneous reactions of NO 2 were more efficient in suburban areas and in clean periods while direct emissions and homogeneous reactions contributed more in urban areas and in polluted periods when the concentrations of NO x and NO were at a high level.

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Purchase subsidy has been adopted to accelerate the diffusion of New Energy Vehicles (NEVs) in China. With a Multi-stage Difference-in-Differences (DID) method, this research investigates the impact of purchase subsidy on Research and Development (R&D) efforts of NEV enterprises. The results indicate that purchase subsidy for NEVs has a positive and significant impact on R&D efforts of NEV enterprises. The impact increases when the purchase subsidy rate decreases. When considering the influences of government procurement and exemption on purchase tax, the positive impact of purchase subsidy still remains significant. The policy implications are that the purchase subsidy rate should be reduced, and stricter technological requirements should be set to couple with the purchase subsidy.