广西乐业大石围天坑群多环芳烃的干湿沉降

为研究大气多环芳烃(PAHs)的沉降对广西乐业大石围天坑群喀斯特生态环境的影响,选择典型的大石围天坑,采用大气干湿采样器分季节进行了为期1 a(2007-03～2008-03)的大气干湿沉降样品采集,利用气相色谱-质谱联用仪(GC-MS)测定了16种PAHs优先控制污染物.结果表明,大气干湿沉降中PAHs的干湿沉降通量为132.36～1 655.27 ng.(m2.d)-1,平均值为855.00 ng.(m2.d)-1,大石围天坑的PAHs沉降量为51.98 g.a-1;PAHs的组成以苯并b]荧蒽、、苯并a]芘、苯并k]荧蒽、蒽、菲、萘7种为主,占总量PAHs的78.5%;大气PAHs沉降通量的空间分布为东垭口>南垭口>西峰>北垭口;不同季节的沉降通量为春季>夏季>秋季>冬季,春、夏季PAHs沉降通量高于秋、冬季4.6倍,春、夏季以4～6环PAHs为主,而秋、冬季以2～3环PAHs为主;研究区大气PAHs沉降通量与降雨量、风向、风速、温度气象因子及污染源的方位密切相关;大石围天坑群大气PAHs沉降通量在春季、夏季呈季节性增高可能来源于高气温、低海拔的广西工业发达地区.

Atmospheric Deposition of PAHs in Dashiwei Karst Tiankeng Group in Leye,Guangxi

In order to understand atmospheric deposition of polycyclic aromatic hydrocarbons impact on ecological environment of Dashiwei Karst Tiankeng Group in Leye County,Guangxi(National Geological Park), the dry and wet deposition samples around Dashiwei Tiankeng were collected by season for a year, and were analyzed utilizing GC-MS for 16 EPA PAHs. The results showed that PAH depositional fluxes ranged from 132.36-1655.27 ng·(m²·d)^-1, with an average value of 855.00 ng·(m²·d)^-1. Weight of PAHs which deposited into Dashiwei Tiankeng was 51.98 g·a^-1, and the dominant PAH compounds are benzob]fluoranthene, chrysene, benzoa]pryene, benzok]fluoranthene, anthracene, phenanthrene and naphthalene. Spatial distribution of PAHs around Dashiwei Tiankeng was: the east valley entrance>the south valley entrance>the north valley entrance>the west peak; seasonal variability of PAH depositional fluxes was: spring>summer>autumn>winter. Deposition fluxes of PAHs were 4.6 times higher in spring and summer than those in autumn and winter. The dominant PAH compounds were 4-6 rings PAHs in spring and summer, but the dominant PAH compounds were 2-3 rings PAHs in autumn and winter. PAH depositional fluxes in this study area were closely related with precipitation, wind direction, temperature, wind speed and location of pollution sources. PAHs increased in spring and summer in Dashiwei Karst Tiankeng Group, this could be transported by atmospheric movement from higher air temperature and lower elevation areas where industry developed in Guangxi.