北京典型土壤剖面含氧非烃化合物分布及成因

根据对北京地区6个典型采样点土壤样品的试验分析结果,探讨了含氧非烃化合物的含量、组成及其在采样点剖面上的分布特征,并对其污染源进行了讨论. 结果表明,检测到的含氧非烃化合物主要包括C₆~C₂₈正构烷酸类、C₁₂~C₂₈正构烷醇类、正构烷酸甲酯类、酞酸酯类、甾醇类和脱氢松香酸等. 含氧非烃化合物总质量分数及各类化合物的质量分数均有随深度增大而降低的趋势,其中0~40cm含氧非烃化合物总质量分数(4.539~60.689μg/g)较高且变化明显,深度大于40cm的土壤中降至<9.000 μg/g且均趋于稳定. 各采样点含氧非烃化合物的总质量分数纵向变化特征与w(TOC)的变化趋势基本一致,表明w(TOC)是控制土壤中含氧非烃化合物分布的重要因素. 不同采样点正构烷酸类化合物都以C₁₆为主峰碳,次主峰碳为C₁₈,除个别采样点表层土壤中高碳数正构烷酸存在较明显奇偶优势外,中低碳数正构烷酸偶碳优势不明显,推测其主要来源于化石燃料或原土中的有机质,部分高分子量正构烷酸来源于生物质；正构烷醇类以C₂₂为主峰碳,并具有明显的偶碳优势,主要来源于植物或者微生物源等天然源；酞酸酯中DBP(邻苯二甲酸二丁基酯)、DEHP〔邻苯二甲酸二(2-乙基己基)酯〕和DIBP(邻苯二甲酸二异丁基酯)质量分数较高,其来源与这些化合物的人为使用有关；甾醇类以β-谷甾醇占优势,并且大部分集中在表层,主要为生物源. 

The Distribution and the Origin of Oxygenated Non-Hydrocarbons in Soil Profiles in Beijing, China

Oxygenated non-hydrocarbons are widely distributed in soil environment and most of the species are toxic, teratogenetic and persistent. They could be fatally harmful to soil ecosystem and human health. Recently, many studies reported that oxygenated non-hydrocarbons widely existed in different environments in Beijing. However, the distribution and the origin of those compounds in soil profiles still remain unclear. To investigate the distribution and the origin of oxygenated non-hydrocarbons, the content and compositions of the compounds were measured using soil samples collected from six site profiles in Beijing. The results showed that oxygenated non-hydrocarbons in soil samples mainly consisted of C₆-C₂₈ n-fatty acids, C₁₂-C₂₈ n-fatty alcohols, n-fatty acid methyl esters, phthalates, sterols and dehydrogenation rosin acid, and the contents of total oxygenated non-hydrocarbons changed at a range of 4.539-60.689μg/g in the surface layer of those soil profiles. The contents and compositions of those compounds from surface layer were distinct between different soil profiles. The contents of the total oxygenated non-hydrocarbons and a single compound decreased with increase of depth in some typical soil profiles. The contents were relatively high and the vertical change was significant for the surface layer (0-40cm), whereas the contents (<9.000μg/g) were greatly low and gradually tended to be constant in the deep layer (>40cm). The vertical changes of total organic carbon (TOC) were consistent with that of oxygenated non-hydrocarbons in soil profiles. This result indicated that the origins of those oxygenated non-hydrocarbons were related with the organic matters in the soil. The n-fatty acids in those samples had a main peak of C₁₆, and were followed by a peak C₁₈. Except for few soil profiles, those n-fatty acids with low carbon number showed no any predominance in odd-or even-number of carbon, it was inferred that those compounds were probably originated from fossil fuel or organic matters in soil, and some high molecular weight n-alky fatty acids may be derived from biomass. The n-fatty alcohols show a main peak of C₂₂, and are obvious predominated by even-number of carbon compounds, so we infer that those compounds are mainly originated from plant or microbial and other natural sources. Among the phthalates, the contents of DBP, DEHP and DIBP were high, and it indicated that those compounds were caused by the human usage of these compounds. The sterols were predominated by β-sitosterol, and were mainly enriched in the surface layer. Consequently, we suggest that those compounds are originated from the biological source, especially from the plants.