Bidleman Terry E, Leone Andi D, Wong Fiona, van Vliet Laurens, Szeto Sunny, Ripley Brian D
Centre for Atmospheric Research Experiments, Environment Canada, 6248 Eighth Line, Egbert, Ontario, Canada.
Environ Toxicol Chem. 2006 Jun;25(6):1448-57. doi: 10.1897/05-361r.1.
Air samples were collected above agricultural fields in the Fraser Valley and orchards in the Okanagan Valley, British Columbia, Canada, to investigate volatilization of organochlorine pesticides used in the past. Concentrations of pesticides in air were elevated over soils that contained higher residues. Soil/air fugacity ratios at sites with the higher soil residues were calculated relative to air sampled at 40 cm height and background air. The fugacity ratios in the first case indicated net volatilization or soil-air equilibrium for most compounds and occasional net deposition for p,p'-dichlorodiphenyldichloroethene (p,p'-DDE), whereas those in the second case showed a strong potential for net volatilization of all compounds. The enantiomer fraction (EF) of chiral compounds alpha-hexachlorocyclohexane (alpha-HCH), trans-chlordane, cis-chlordane, and o,p'-DDT were determined in overlying air samples and soils. Enantiomer fractions in air corresponded to those in soils at fields in which soil concentrations were high but were decoupled from soil signatures at fields with low soil residues. Mean EFs in air sampled over soils were significantly (p < 0.001) nonracemic for alpha-HCH and the chlordanes and agreed with published EFs in regional ambient air. The mean EF of o,p'-DDT for all air samples did not show a significant deviation from racemic EFs (p > 0.2), but EFs of individual samples reflected the ambivalent nature of o,p'-DDT degradation, sometimes preferring the (+) enantiomer and other times the (-) enantiomer. The study indicates that soils are continuing to emit "legacy" pesticides into the regional atmosphere.
在加拿大不列颠哥伦比亚省弗雷泽河谷的农田上方以及奥肯那根山谷的果园中采集空气样本，以调查过去使用的有机氯农药的挥发情况。在含有较高残留量的土壤上方，空气中农药的浓度有所升高。相对于在40厘米高度采集的空气样本和背景空气，计算了土壤残留量较高地点的土壤/空气逸度比。第一种情况下的逸度比表明，大多数化合物存在净挥发或土壤-空气平衡，而p,p'-二氯二苯二氯乙烯（p,p'-DDE）偶尔存在净沉降，而第二种情况下的逸度比表明所有化合物都有很强的净挥发潜力。在手性化合物α-六氯环己烷（α-HCH）、反式氯丹、顺式氯丹和o,p'-滴滴涕（o,p'-DDT）的上覆空气样本和土壤中测定了对映体分数（EF）。在土壤浓度较高的田地中，空气中的对映体分数与土壤中的对映体分数相对应，但在土壤残留量较低的田地中，空气中的对映体分数与土壤特征脱钩。在土壤上方采集的空气样本中，α-HCH和氯丹的平均EFs显著非外消旋（p < 0.001），与区域环境空气中公布的EFs一致。所有空气样本中o,p'-DDT的平均EF与外消旋EF没有显著偏差（p > 0.2），但个别样本的EF反映了o,p'-DDT降解的矛盾性质，有时优先选择（+）对映体，有时优先选择（-）对映体。该研究表明，土壤仍在继续向区域大气中排放“遗留”农药。
