DEGRADATION OF DISSOLVED ORGANIC NITROGEN AND BIOGEOCHEMISTRY OF AMINO ACIDS IN SURFACE SEDIMENT OF LAKE QINGNIAN AND WETLAND QILIHAI

摘要

To investigate the spatial distribution and seasonal variation of dissolved organic nitrogen (DON) in surface sediment, field study was performed in Lake Qingnian and Wetland Qilihai from February to December in 2010. Meanwhile, simulation experiments were carried out to better understand the degradation of DON. The pollution of Lake Qingnian was more serious than that of Wetland Qilihai. Total hydrolyzable amino acid (THAA-N), accounting for about 40% of DON, was the dominant nitrogen species in the sediment. Bacterial residues were the most important source of organic nitrogen in the sediment of Wetland Qilihai, where DON more highly degraded than Lake Qingnian. Degradative Index (DI) was successfully applied to examine the degradation status of sedimentary organic matter in different seasons. That DI decreased in spring and summer whereas increased in autumn and winter, illustrated that more degraded organic matter in summer and autumn than spring and winter in the cores. By principal component analysis, that a higher loading of Leu, Glu, Ile, Gly, Ser and Thr in the first principal component reflect the degradability of sedimentary organic nitrogen. As to natural shallow anoxic sediments, the decomposition rate of organic nitrogen in anoxic condition was slightly higher than that of aerobic condition, whereas aerobic condition conducive to the degradation of amino sugar (HA-N). The degradation of DON was major in terms of THAA-N which accounting for about 45% of the DON degradation in control. In the degradation of the THAA-N by microbe, THAA-N were absorbed and utilized in terms of polypep-tide before decomposed into free amino acids.