古水稻土中多环芳烃的分布特征及其来源判定

Distribution Characteristics and Sources Identification of PAHs in Ancient Paddy Soil

测定了马家浜文化（距今约6000a）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．

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 202.9μg·kg^-1 and 207.7μg·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 56.0μg·kg^-1, but was still higher than those in ancient dry land soil and bottom soils with the sum of 32.0～36μg·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.