Faculty of Civil and Environmental Engineering, Technion-Israel Institute of Technology, Technion City, 32000, Haifa, Israel.
Phys Chem Chem Phys. 2011 Jan 14;13(2):506-17. doi: 10.1039/c0cp00931h. Epub 2010 Nov 8.
Evaluation of pesticides' fate in the atmosphere is important in terms of environmental effects on non-target areas and risk assessments analysis. This evaluation is usually done in the laboratory using analytical grade materials and is then extrapolated to more realistic conditions. To assess the effect of the pesticide purity level (i.e. analytical vs. technical) and state (i.e. sorbed film vs. airborne particles), we have investigated the oxidation rates and products of technical grade cypermethrin as thin film and in its airborne form, and compared it with our former results for analytical grade material. Technical grade thin film kinetics for both ozone and OH radicals revealed reaction rates similar to the analytical material, implying that for these processes, the analytical grade can be used as a good proxy. Oxidation products, however, were slightly different with two additional condensed phase products: formanilide, N-phenyl and 2-biphenyl carboxylic acid, which were seen with the technical grade material only. OH experiments revealed spectral changes that suggest the immediate formation of surface products containing OH functionalities. For the ozonolysis studies of airborne material, a novel set-up was used, which included a long-path FTIR cell in conjugation with a Scanning Mobility Particle Sizer (SMPS) system. This set-up allowed monitoring of real-time reaction kinetics and product formation (gas and condensed phases) together with aerosol size distribution measurements. Similar condensed phase products were observed for airborne and thin film technical grade cypermethrin after ozonolysis. Additionally, CO, CO(2) and possibly acetaldehyde were identified as gaseous oxidation products in the aerosols experiments only. A kinetic model fitted to our experimental system enabled the identification of both primary and secondary products as well as extraction of a formation rate constant. Kinetic calculations (based on gaseous products formation rate) have revealed values similar to that of the thin film experiments. Interestingly, heterogeneous oxidation of cypermethrin was also found to generate ultra fine secondary organic aerosols. Again, no significant difference was observed between analytical and technical grade materials. However, particle size distribution was much broader when films were exposed to OH and ozone than to ozone alone.
评估农药在大气中的归宿对于非靶标区域的环境影响和风险评估分析非常重要。通常在实验室中使用分析纯物质进行此类评估，然后外推至更现实的条件下。为了评估农药纯度水平（分析级与技术级）和状态（吸附膜与空气传播颗粒）的影响，我们研究了技术级氯菊酯薄膜和空气传播形式的氧化速率和产物，并将其与我们之前分析级物质的结果进行了比较。技术级薄膜对臭氧和 OH 自由基的动力学研究表明，反应速率与分析级物质相似，这意味着对于这些过程，可以使用分析级物质作为良好的替代品。然而，氧化产物略有不同，出现了两个附加的凝聚相产物：甲酰苯胺、N-苯基和 2-联苯羧酸，仅在技术级材料中观察到。OH 实验揭示了光谱变化，表明立即形成含有 OH 官能团的表面产物。对于空气传播物质的臭氧化研究，采用了一种新的装置，该装置包括长程傅里叶变换红外（FTIR）池与扫描迁移率颗粒谱（SMPS）系统的联用。该装置允许实时监测反应动力学和产物形成（气相和凝聚相）以及气溶胶粒度分布测量。空气传播和薄膜技术级氯菊酯臭氧化后的凝聚相产物相似。此外，仅在气溶胶实验中鉴定出 CO、CO(2)和可能的乙醛作为气态氧化产物。拟合我们实验系统的动力学模型使我们能够识别主要和次要产物，并提取形成速率常数。动力学计算（基于气态产物形成速率）表明，其值与薄膜实验相似。有趣的是，氯菊酯的非均相氧化也被发现会产生超细二次有机气溶胶。同样，在分析级和技术级材料之间未观察到明显差异。然而，当薄膜暴露于 OH 和臭氧时，与单独暴露于臭氧相比，颗粒尺寸分布要宽得多。
