Dr. Cortes et Ra. Hites, Detection of statistically significant trends in atmospheric concentrations of semivolatile compounds, ENV SCI TEC, 34(13), 2000, pp. 2826-2829
Citations number
19
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
This paper examines the sampling and analytical requirements of observing s
tatistically significant temporal trends in atmospheric concentrations of s
emivolatile organic pollutants. Data precision and study duration are found
to be the most important factors that are subject to experimental control.
We define a detectable half-life as the longest half-life for which statis
tical significance can be observed for a given length of study and show how
this can be calculated. Finally, we show how to predict the length of a st
udy that will find a statistically significant half-life. These concepts ar
e applied to a recently updated temporal trends study from the Integrated A
tmospheric Deposition Network. Updated ha If-lives for gas-phase pesticides
at three U.S. sampling sites are given. There are now enough data to obser
ve statistically significant temporal trends for most of the gas-phase pest
icides except for alpha-chlordane and trans-nonachlor at Eagle Harbor. Usin
g the concept of detectable half-life and based on observations of half-liv
es at other lADN sites, at least 2 more years of study are required to obse
rve statistically significant trends for alpha-chlordane and trans-nonachlo
r. The concepts presented in this paper can also be applied to the design o
f sampling strategies for measuring long-term temporal trends in media othe
r than air.