水稻根系中多环芳烃的动态变化

Dynamics of polycyclic aromatic hydrocarbon (PAH) accumulation in rice roots

水稻根系的多环芳烃浓度随着水稻的生长不断变化,呈现出初期逐渐升高,到成熟期趋于稳定的一般趋势.幼穗期、乳熟期、蜡熟期、完熟期和枯熟期水稻根系的多环芳烃总含量(PAH15)平均分别为464、969、592、1075ng·g-1和1059ng·g-1,并主要由3环化合物组成.根系的脂含量、比表面和生物量等指标对根系多环芳烃的变化起到了一定影响.其中,脂含量和比表面的影响比生物量的影响更为显著.随着水稻的成熟,水稻土多环芳烃含量逐渐降低,而5、6环化合物的比例逐渐增加.水稻根系和水稻土中的多环芳烃含量之间存在明显的负相关关系.

The concentration of polyeyelie aromatic hydrocarbons accumulated in rice roots shows an increasing trend with growth. The total amount of 15 measured PAH compounds present in rice roots during various growth stages were 464, 969, 592, 1075 and 1059 ng· g^-1 respectively, corresponding to headlng, milk, dough, mature and wilting stages, in turn. The PAHs spectrum consisted of mainly 3-ring and lower molecular weight compounds. Three factors-ruot lipid content, specific surface area and root biomass-are discussed in this study. When normalizing the root dry weight PAH concentration to root lipid concentration and root specific surface area, the differences among the growth stages were diminished by a factor of 4 to 5. However, the same normalization to the root biomass did not affect the differences significantly, indicating that rice root PAH uptake is affected by the root lipid content and surface area much more than by the root biomass. The PAHs in paddy field soil are significantly different from those in rice roots, both in the trend daring growth stages and in the distribution patterns. A significant negative relationship was observed between the PAHs concentrations in rice roots and paddy soil. Soil PAHs decreased with rice growth and consisted predominantly （ 〉 50% ） of 5 and 6 ring compounds. The combined effects of microbial activity, root exudates, hydrolysis and photolysis may explain the above observations.