Dr. Cortes et al., Evidence of current pesticide use from temporal and Clausius-Clapeyron plots: A case study from the Integrated Atmospheric Deposition Network, ENV SCI TEC, 33(13), 1999, pp. 2145-2150
Citations number
18
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
We found evidence of recent agricultural pesticide use in atmospheric sampl
es collected at Point Petre, Ontario, one of the sampling sites of the Inte
grated Atmospheric Deposition Network. The evidence consists of a residual
cycle of gamma-HCH concentrations that remains after correction for tempera
ture effects. While the recent use of gamma-HCH has been observed by other
researchers, the length and resolution of this study allow for a more quant
itative assessment. To characterize the residual cycle, we compared the fit
of three periodic functions and included the function with the best fit in
a model with temperature and time. The estimated parameters were used to i
dentify agricultural use as the source of the residual cycle. We also exami
ned the effect of agricultural use on the information typically extracted f
rom Clausius-Clapeyron plots. We found that the presence of an agricultural
cycle maximizing near the temperature cycle results in an increased enthal
py of phase transition. In addition, the phase offset of the two cycles res
ults in an increased apparent scatter in the data. Finally, the shape of th
e agricultural cycle imparts curvature to the normally linear relationship
observed in Clausius-Clapeyron plots. These findings suggest that recent in
terpretations of Clausius-Clapeyron plots in terms of a compound's environm
ental behavior may be incomplete.