东部平原湖区沉积物中溶解性有机氮分布特征

Distribution characteristics of dissolved organic nitrogen(DON) in the lake sediments of Eastern Plain Region,China

选择东部平原湖区11个湖泊进行水质和表层沉积物调查,采用综合营养状态指数（TLI）对各湖泊营养状态进行评价,研究了沉积物溶解性有机氮（DON）和游离氨基酸（FAA）的含量分布及DON分子质量分级特征,并探讨了不同湖泊沉积物有机质来源。结果表明：除固城湖和骆马湖处于中营养水平外,东部平原湖区其他湖泊均处于富营养化状态。沉积物DON浓度差异较大,在9.98～182.00 mg·kg-1之间波动,均值为57.25 mg·kg-1,太湖、滆湖、阳澄湖沉积物DON含量较高,均在140 mg·kg-1以上,其他湖泊沉积物DON含量均在50 mg·kg-1以下。区域内氨基酸（FAA）分布比较均匀,FAA浓度在3.58～13.28 mg·kg-1之间,平均值是8.14 mg·kg-1。沉积物DON和FAA含量与沉积物其他形态氮、溶解性有机碳（DOC）等污染指标均表现出显著正相关性。东部平原湖区沉积物分子质量分级结果表明：该湖区沉积物DON、DOC和SUV254基本都分布在〈1 k Da和〉30 k Da 2个范围内。东部平原湖区C/N比的值介于2.31～89.02之间,除滆湖外其他湖泊沉积物C/N值均大于10,说明该地区湖泊沉积物有机质主要来自外源。

The characteristics of water and surface sediments in 11 lakes located in the Eastern Plain Re- gion were surveyed, and a comprehensive trophic level index method （TLI） was applied to evaluate the water quality conditions. For sediments,in particular,the contents of dissolved organic nitrogen （DON） and free amino acids （FAA） were determined and DON molecular weight （MW） fractionation analyses were performed. The sources of natural organic matter （NOM） in lake sediments were also investigated. The results indicated that most lakes in the Eastern Plain Region were at the eutrophic level,whereas Gucheng Lake and Luoma Lake were at the mesotrophic level. The DON contents in lake sediments varied greatly from 9.98 to 182.00 mg· kg-1, and the average value was 57.25 mg· kg-l. The DON contents of Taihu Lake, Gehu Lake, and Yangcheng Lake were higher than 150 mg· kg-1 ,while the DON contents in other lakes were lower than 50 mg· kg-1. The contents of FAA were more evenly distributed from 3.58 to 13.28 mg· kg-1 ,with an average value of 8.14 mg· kg-1. The DON and FAA contents were significantly correlated with the contents of other nitrogen forms and dissolved or- ganic carbon （DOC）. The DON, DOC, and SUV254 molecular fractionation results indicated that the dominant fractions in lake sediments of the Eastern Plain Region included the fractions with low molecular weights （MW） of 〈 1 kDa and high MW 〉 30 kDa. The C/N ratios in the Eastern Plain Region ranged from 2.31 to 89.02 ,with an average of 41.26, and these findings suggest that the NOM was mainly derived from external sources of input.