"INTRODUCTION This final report describes the work performed on Phase II of APRAC Project CAPA-7-68@ ""Atmospheric Reaction Studies in the Los Angeles Basin"" (Contract No. CPA-22-69-19). Phase II consisted of two major activities: analysis of the aerometric data collected by Scott during the fall of 1968 and development of improved methods of chemical analysis applicable to the 1969 field survey and other future aerometric studies. The purpose of the data analysis was to study the relationships among the chemical and meteorological parameters measured in the 1968 field survey of the Los Angeles Basin in order to define the formation rates of various photochemical products@ especially nitrogen dioxide@ oxidant and ozone in terms of these parameters. Additional relationships were studied to shed light on emissions sources@ reaction times and the overall behavior of the atmospheric system. The data analysis was .also conducted to aid in the design of the 1969 field program by providing a firmer basis for evaluating the most important factors to be measured@ the critical periods during which measurements should be made and the location of sampling points. The methods development was undertaken to improve analytical techniques which did not produce satisfactory results in the 1968 field survey or devise alternate methods@ to expand other procedures to make them capable of providing additional useful data@ and to .validate the performance of the instrumentation and procedures employed in the field work. Emphasis was placed on analysis of nitrogen compounds and individual C1 to C10 hydrocarbons. Most of the work was performed in Scott's Plumsteadville laboratory using the same instrumentation and equipment that had been located in the Scott mobile laboratory used to obtain data at the E1 Monte site in the 1968 Los Angeles Basin survey."