Short-term variation in ambient concentrations and gas/particle partitioning of organochlorine pesticides in Izmir, Turkey
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Twenty successive daytime and nighttime air samples were collected and analyzed for 23 currently used and/banned organochlorine pesticides (OCPs) between 14 and 23 May 2003 in Izmir, Turkey. Average individual OCP concentrations ranged from 5±4pgm-3 (p,p′- dichlorodiphenyldichloroethane) to 391±306pgm-3 (chlorpyrifos) and they were within the ranges previously measured at different sites. Most of the OCPs did not exhibit strong diurnal cycling. The temperature dependence of gas-phase atmospheric concentrations of OCPs investigated using Clausius-Clapeyron plots was statistically significant for β-HCH and endosulfan sulfate (p<0.1) and was not significant for other compounds (0-21% of the variability in their gas-phase concentrations). In addition to temperature, the effect of wind speed and direction was also investigated using multiple linear regression analysis and these three parameters together explained the 2% (aldrin) to 72% (endosulfan II) of the variability in gas-phase OCP concentrations. Results of the multiple regression analysis indicated that wind speed was a statistically significant factor for most of the OCPs and wind direction was important for some compounds. The temperature-dependent diurnal cycling of most OCPs was probably masked by the higher wind speeds observed during daytime periods with high temperatures, different source sectors and ongoing sources. The lack of correlation for heptachlor, aldrin, p,p′-dichlorodiphenyldichloroethylene (p-p′-DDE), and p,p′-dichlorodiphenyltrichloroethane (p-p′-DDT) with temperature, wind speed and direction suggested that their concentrations were affected by long-range transport. The partitioning of OCPs between particle and gas phases was investigated and compared to KOA (octanol/air partition coefficient) absorption model. The overall agreement between experimental and modeled logKp (gas/particle partition coefficient) values was good (p<0.01, slope=0.94). Prediction of absorption model for particulate percentages was excellent for β-HCH, endosulfan I, and p-p′-DDT. However, the model underpredicted the particulate percentages for α,γ-HCHs, chlorpyrifos, and dieldrin, and overpredicted those for p-p′-DDE.