Key Laboratory of Tibetan Environmental Changes and Land Surface Process, Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS) , Beijing 100101, China.
CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China.
Environ Sci Technol. 2017 May 16;51(10):5642-5649. doi: 10.1021/acs.est.7b01029. Epub 2017 May 2.
The passive air sampler based on XAD-2 resin (XAD-PAS) has proven useful for collecting atmospheric persistent organic pollutants (POPs) in remote regions. Whereas laboratory studies have shown that, due to the open bottom of its housing, the passive sampling rate (PSR) of the XAD-PAS is susceptible to wind and other processes causing air turbulence, the sampler has not been calibrated in the field at sites experiencing high winds. In this study, the PSRs of the XAD-PAS were calibrated at three sites on the Tibetan Plateau, covering a wide range in temperature (T), pressure (P) and wind speed (v). At sites with low wind speeds (i.e., in a forest and an urban site), the PSRs are proportional to the ratio T/ P; at windy sites with an average wind speed above 3 m/s, the influence of v on PSRs cannot be ignored. Moreover, the open bottom of the XAD-PAS housing causes the PSRs to be influenced by wind angle and air turbulence caused by sloped terrain. Field calibration, wind speed measurements, and computational fluid dynamics (CFD) simulations indicate that a modified design incorporating an air spoiler consisting of 4 metal sheets dampens the turbulence caused by wind angle and sloped terrain and caps the PSR at ∼5 m/day, irrespective of ambient wind. Therefore, the original XAD-PAS with an open bottom is suitable for deployment in urban areas and other less windy places, the modified design is preferable in mountain regions and other places where air circulation is complicated and strong.
基于 XAD-2 树脂的被动空气采样器（XAD-PAS）已被证明可用于收集偏远地区的大气持久性有机污染物（POPs）。虽然实验室研究表明，由于其外壳底部是敞开的，XAD-PAS 的被动采样速率（PSR）容易受到风以及其他引起空气紊流的过程的影响，但在风速较高的地点，尚未在野外对该采样器进行校准。本研究在青藏高原的三个地点对 XAD-PAS 的 PSR 进行了校准，这些地点的温度（T）、压力（P）和风速（v）范围很广。在风速较低的地点（即森林和城市地点），PSR 与 T/P 比值成正比；在平均风速超过 3 m/s 的大风地点，v 对 PSR 的影响不容忽视。此外，XAD-PAS 外壳的底部敞开会导致 PSR 受到风向和由地形倾斜引起的空气紊流的影响。现场校准、风速测量和计算流体动力学（CFD）模拟表明，一种改良设计，其中包括由 4 个金属片组成的空气扰流器，可减轻风向和地形倾斜引起的紊流，并将 PSR 限制在约 5 m/天，而与环境风无关。因此，带有敞开底部的原始 XAD-PAS 适用于城市地区和其他风速较低的地方，改良设计在山区和其他空气循环复杂且强劲的地方更可取。
