桂林市果园表土多环芳烃含量及来源研究

Contents and Sources of PAHs in Topsoils of Orchards in Guilin

[目的]分析桂林市果园土壤多环芳烃(PAHs)含量与来源,为评价果园地安全性提供参考。[方法]在桂林市葡萄园、柑橘园和桃园基地采集表土,分析美国环保署优控的16种多环芳烃(PAH16),运用多环芳烃单体含量、谱系、丰度及诊断比值等构成的指标体系进行源识别。[结果]果园表土PAH16含量平均为34.91 ng/g(<报出限~143.8 ng/g),低于我国土壤背景值和荷兰无污染土壤限值(<200 ng/g)。果园表土PAH16以4~6环的芘(Pyr)、苯并[a]蒽(BaA)、(?)(Chr)、苯并[b]荧蒽(BbF)、苯并[k]荧蒽(BkF)、苯并[a]芘(BaP)、茚并[1,2,3-cd]芘(InP)、苯并[g,h,i]苝(BgP)为主,2~3环的PAH16低于报出限(荧蒽除外),单体含量介于<报出限~23.4ng/g之间,检出率12.5%~68.8%,以BbF检出率最高,其次是Chr(56.3%)。葡萄园表土检出的PAHs种类最全、含量最高,其中LX001样地PAH16单体均>10.0 ng/g,而柑橘园仅检出单体BbF(<报出限~6.64 ng/g)、Chr(<报出限~3.34 ng/g),检出率44.4%~66.7%。PAHs指标体系表明,废旧轮胎炼油与汽车尾气、农药杂质降解和木头、草燃烧可能分别是三类果园土壤PAH16的主要来源。[结论]就土壤PAH16而言,炼油厂约7 km以远或交通干道200 m以外的果园是安全的。

[Objective]To provide a reference for evaluating the safety of orchard,the contents and sources of polycyclic aromatic hydrocarbons(PAHs)from orchard soil in Guilin were analyzed.[Method]The topsoil(0-20 cm)was sampled from the vineyard,the citrus orchard and the peach garden in Guilin to analyze sixteen US EPA priority PAHs(PAH_(16))and to identify their sources using indicators system composed of the level,profile,and diagnostic ratios of individual PAHs and relative abundance of low/high benzene rings PAHs to PAH16.[Result]The mean content of PAH16 from orchard topsoil was 34.91 ng/g(reporting limits to 143.8 ng/g),which was below the background of national soil and the no pollution limit of 200 ng/g determined by Netherlands.4-6 rings of PAH16,such as pyrene(Pyr),benzo[a]anthracene(BaA),chrysene(Chr),benzo[b]fluorathene(BbF),benzo-[k]fluorathene(BkF),benzoapyrene(BaP),indeno(1,2,3-cd)pyrene(InP)and benzo[ghi]perylene(BgP),were predominant in topsoil of orchard surveyed,while 2-3 rings were below the reporting limit except fluoranthene(Flt).The level of individual PAH16 was betweenreporting limits and 23.4 ng/g,with detection frequencies of 12.5%-68.8% followed by decline order of the highest BbF and higher Chr(56.3%).The most species and content of PAH16 were checked in vineyard soils,especially with more than 10 ng/g of all detectable individuals in the LX001 plot sampled,whereas only BbF(6.64 ng/g)and Chr(3.34 ng/g)were detected at detection frequencies of 44.4%-66.7% in citrus orchard soils.Indicators system of PAHs showed that dominant pyrolysis of scrap tires for diesel along with vehicle emission,pesticide impurity degradation and combustion of wood and grass were main sources of PAH16 in the soil of vineyard,citrus orchard and peach garden,respectively.[Conclusion]In terms of soil PAH16,the orchards about 7 km far from oil refinery or 200 meters far from main road were safe.