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A pilot study, which was conducted in the Southern Blue Ridge geographical province of the Southeastern U.S., demonstrated the feasibility of a probability‐based regional synoptic design for the National Stream Survey, which is a project aimed at estimating the number and percentage of streams in various regions of the U.S. that are acidic or at risk from acid deposition. Estimated population distributions for key chemical variables were not appreciably affected by week‐to‐week variability in stream chemistry during the spring index period chosen for the study. Differences were observed in estimated acid neutralizing capacity (ANC), nitrate, and pH frequency distributions between spring and summer. Observations made at the downstream node did not represent the chemistry of the entire reach for some variables (ANC and nitrate) as indicated by differences in chemical concentrations between upstream and downstream sampling locations. Coefficients of variation in chemical species were low enough to provide a reasonably stable classification of streams based on ANC. Although median ANC, sulfate, and nitrate concentrations were quite low in the region, the probability of finding streams with ph < 6.3 is less than 1.3 percent at the α= 0.05 confidence level.

Hydroxylation by housefly microsomes, using naphthalene-1-C14 as substrate, has been tested as a possible site of action of the pyrethrin synergists. Five commercial and nine noncommercial compounds containing the methylenedioxyphenyl structure were inhibitory of this process. Inhibitory concentrations range from 10_2M for piperonylic acid to 1 CT5M for safrole and isosafrole. Of the commercial synergists, piperonyl cyclonene is the most potent inhibitor of microsomal hydroxylation. The commercial synergists, sesamex, sulfoxide, piperonyl butoxide, and n-propyl isome, and the noncommercial compounds, safrole, isosafrole, and piperonal, were found to be synergistic with naphthalene in in vivo tests with female houseflies.

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