古水稻土中多环芳烃的分布特征及其来源判定

测定了马家浜文化(距今约6 000a)遗址2个剖面表层土壤、古代水稻土和古代旱地土壤、以及底层土壤中15种多环芳烃的含量,并对其可能来源进行了判定.结果表明,表层土壤中PAHs的含量分别为202.9μg·kg^-1和207.7μg·kg^-1,主要来源于大气沉降;古水稻土中PAHs含量明显降低,仅为56.0μg·kg^-1,但高于古旱地土壤及底层土壤。古旱地土壤及底层土壤PAHs含量在32.0～36.9μg·kg^-1.古水稻土中,2环和3环所占比例较大,达63%,萘和菲含量最高,而4环以上的多环芳烃含量较低.Phe/Ant和BaA/Chr比值和有机质¹³C-NMR图谱显示,古水稻土中的多环芳烃主要来源于水稻秸秆的焚烧,同时还原条件下的生物合成可能是其另一个重要来源.

Distribution Characteristics and Sources Identification of PAHs in Ancient Paddy Soil

Soil samples of current paddy soils, ancient paddy soil/ancient dry land soil, and bottom soils were collected from two sites in Chuodunshan Site of Majiabang Culture (about 6,000a). 15 polycyclic aromatic hydrocarbons (PAHs) were analyzed with HPLC, and their possible sources were identified. The sum of 15 PAHs was 202.9microg x kg(-1) and 207.7microg x kg(-1) in the surface soils from Site A and Site B respectively, which were mainly deposited from atmosphere. In ancient paddy soil from Site A, the total PAHs concentration sharply decreased to 56.0microg x kg(-1), but was still higher than those in ancient dry land soil and bottom soils with the sum of 32.0 approximately 36.9microg x kg(-1). In ancient paddy soil, the concentrations of 2-ring and 3-ring PAHs took a larger portion of 63 percents to the total PAHs, and naphthalene and phenanthrene were the most abundant compounds, while PAHs of more than 4 rings took a small part. The ratios of phenanthrene anthracene and benzo(a) anthracene chrysene and 13C-NMR spectrum of soil organic matter showed that PAHs in ancient paddy soil mainly originated from rice straw burning, biogenesis under reducing conditions may be another source.