THE NONMETHANE HYDROCARBON INTERCOMPARISON EXPERIMENT (NOMHICE) - TASK-1 AND TASK-2

The NOMHICE program has been designed to evaluate current methods bein g used to determine the ambient levels of various atmospheric nonmetha ne hydrocarbons, to identify existing problems in these analyses, to c orrect these problems, and to help ensure quality control of hydrocarb on analyses made by atmospheric scientists throughout the world. To ac complish this, a series of planned experiments (tasks) is now under wa y which involves all the common classes of the atmospheric hydrocarbon s: alkanes, alkenes, alkynes, aromatic hydrocarbons, and the terpenes. The various tasks of the study have been scheduled in order of increa sing complexity so that problems can be addressed as they arise. Preli minary results are presented for task 1 and task 2 of a multitask prog ram. Each laboratory used its own analysis and calibration procedures. The first task of NOMHICE involved the circulation of a two-component , gravimetrically prepared, hydrocarbon mixture of known composition a nd unknown concentration to 36 participating scientific groups from la boratories throughout the world. This experiment was planned to check on the reliability of the standards employed by each of the participat ing groups. Task 2 involved the circulation, to participant laboratori es, of a more complex, gravimetrically prepared, 16-component hydrocar bon mixture (unknown composition and concentration) to determine wheth er suitable separation, identification, and quantification can be made of the individual hydrocarbons present in the mixture. Further tasks are described which will be carried out in the future.