雪冰中持久性有机污染物的研究进展

PROGRESS IN THE STUDY OF PERSISTENT ORGANIC POLLUTANTS IN SNOW AND ICE

雪冰是温带和极地生态系统中最重要的环境组份,它们不仅影响了能量平衡和水循环,而且也能直接影响当地、区域以及全球环境范围内的化学行为。降雪能很有效地从大气中清除颗粒和气相的POPs。本文简要介绍了雪冰环境中持久性有机污染物研究的科学意义,着重综述了POPs在极地和高海拔地区雪冰中的环境化学行为和雪冰中POPs的历史环境记录,并讨论了雪冰中POPs浓度的不确定性。持久性有机污染物从大气到冰川的过程并不容易理解,半挥发性有机化合物在沉积后的浓度存在不确定性。有机物沉积在积雪中后,随着积雪的老化和变形,它们能够随着融水迁移或者又挥发到大气中。全文最后对未来雪冰中POPs的研究需要进行了展望,并提出四点今后需加强研究的内容。由于青藏高原位于人类居住的低纬度高海拔地区,可能在POPs全球输送过程中起到重要的作用,今后需加强青藏高原地区雪冰中持久性有机污染物的研究;有机污染物在雪冰中主要是通过光化学反应进行转化,雪冰中有机污染物的光化学反应机理研究必须引起重视;随着雪冰样品前处理和分析测试技术的提高,将会推动雪冰中痕量POPs的环境变化记录研究的发展;通过建立模型模拟预算和评价POPs在积雪中的物理化学行为,也可以利用模型模拟POPs在老雪中的命运,确定其在融水中成比例蒸发和渗浸的速率。

Snow and ice are important environmental components of the ecosystem at temperate and polar latitudes. They affect energy balances and hydrologic cycles and can thus directly affect the behaviour of chemicals in the environment on the local, regional and global scales. Snow is an efficient scavenger of POPs from the atmosphere both by adsorption of gaseous and particle scavenging. This paper presents a review of the environmental chemical behavior in snow, discusses the chemical fate following snowfall. The post-depositional fate of POPs in aging snow packs is poorly understood, falling snow scavenges organic contaminants from the atmosphere, which are thus contained in snow packs accumulating on the ground, during snow pack aging and metamorphosis, a chemical can be transferred with melt water to the terrestrial or aquatic environment underlying the snow pack or it may volatilize back into the atmosphere. Furthermore, historical environmental records and analysis methods of POPs from ice and snow in the areas at polar and high altitudes are reviewed as well. Finally, from a consideration of the present state of knowledge, we suggest a number of priority areas for research： a lot of work should be done on POPs from ice and snow on the Tibetan Plateau, because the Tibet Plateau plays an important role in the global transport of POPs and it suffers heavy threat of pollutants; enough attention should be paid to photochemical reaction mechanism in snow and ice; pre-handling and analytical techniques need to be greatly improved. Measurements and models of the fate of POPs in aging snow packs, especially the determination of rates and proportions evaporated and leached in melt water should be conducted and established.