Meyer Torsten, Lei Ying Duan, Wania Frank
Department of Chemical Engineering and Applied Chemistry and Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada, M1C 1A4.
Environ Sci Technol. 2006 May 15;40(10):3320-6. doi: 10.1021/es060049q.
The release of organic contaminants from a melting snowpack may result in temporary concentration peaks in receiving water bodies and respective pulse exposure of aquatic organisms. It is thus of considerable interest to gain a mechanistic and quantitative understanding of the processes determining the dynamic behavior of organic chemicals during snowmelt. Uniformly structured and contaminated snow was produced with the help of a newly designed snow gun and exposed to predetermined temperature conditions in a temperature-controlled cold room. The dry density and liquid water content during four freeze-thaw cycles was recorded continuously at different layers within the snowpack using time domain reflectometry, providing information on meltwater production and propagation as well as snow metamorphism. Fractionated meltwater samples were filtered and the dissolved and particle phase analyzed for five polycyclic aromatic hydrocarbons (PAHs) using gas chromatography/ mass spectrometry. The distribution of the PAHs between the dissolved and particulate fractions of the meltwater was strongly related to their hydrophobicity. Particle-bound PAHs were released late during the snowmelt, whereas PAHs in the dissolved phase were released uniformly during a two day melting period. Even though conductivity measurements indicated a preferential early elution of ions in the first meltwater fractions, no such "first flush" behavior was observed for soluble PAH. The developed laboratory-based approach opens up for the first time the possibility of reproducible experiments on organic contaminant behavior in snow. Future experiments will explore, in detail, how the properties of organic chemicals, the physical and chemical properties of the snowpack, and the temperature variations before and during the time of melting interact to determine the timing of chemical release from a snowpack.
融雪层中有机污染物的释放可能导致受纳水体中出现暂时的浓度峰值，并使水生生物受到相应的脉冲式暴露。因此，深入了解决定融雪期间有机化学物质动态行为的过程，从机理和定量角度进行认识，具有相当重要的意义。借助新设计的雪枪制作出结构均匀且受污染的雪，并将其置于温控冷室中，使其暴露于预定的温度条件下。利用时域反射仪连续记录雪层不同深度在四个冻融循环过程中的干密度和液态水含量，从而获取有关融水产生、传播以及雪变质作用的信息。对分馏后的融水样本进行过滤，并采用气相色谱/质谱联用技术分析其中溶解相和颗粒相中的五种多环芳烃（PAHs）。融水中PAHs在溶解相和颗粒相之间的分布与它们的疏水性密切相关。颗粒结合态的PAHs在融雪后期释放，而溶解相中的PAHs在为期两天的融雪期内均匀释放。尽管电导率测量表明在最初的融水部分中离子优先早期洗脱，但可溶性PAH并未观察到这种“首效”行为。所开发的基于实验室的方法首次开启了对雪中有机污染物行为进行可重复实验的可能性。未来的实验将详细探究有机化学物质的性质、雪层的物理和化学性质以及融雪前后的温度变化如何相互作用，以确定化学物质从雪层中释放的时间。
