As provided for under the 1980 visibility regulation, an attribution analysis may be required for a class I area where one or more pollution emission sources are thought to contribute substantially to visibility impairment. Often, routine monitoring data will not be sufficient for attribution analysis. In such circumstances, special studies may be required to supplement the routine monitoring in- formation. Special studies, unlike routine monitoring, do not lend themselves to standard design recommendations.
Special studies range from simple to sophisticated.
To document the contribution of a more distant source of gaseous precursors for secondary particles, a substantial effort may be required, which could include a supplemental monitoring network, instrumented aircraft, and stack release and ambient monitoring of unique tracer materials. To increase the likelihood of the success of a special study, it should be designed in conjunction with those who are responsible for conducting the attribution analysis. In addition to source attribution, special studies have been performed to enhance the science of visibility monitoring and data analyses. The Winter 1992 intensive monitoring period was just completed. Monitoring continues and a Summer intensive period is scheduled for July through September 1992.