杭州西湖表层沉积物中水溶性有机碳含量的时空分布特征

Spatial and Temporal Variations of Water-soluble Organic Carbon in Surface Sediments of West Lake,Hangzhou

为了解西湖不同湖区表层沉积物中水溶性有机碳(WSOC)含量及动态变化规律,分别对西湖西进区域及大湖区域表层沉积物中的WSOC含量进行了调查。采用奚旦立的改进方法,用总有机碳分析仪测定分析沉积物中WSOC含量。结果表明,西湖表层沉积物WSOC平均含量是387.1 mg/kg,西湖不同湖区的表层沉积物中WSOC含量均呈现显著性的季节性变化,表现为春季(437.5 mg/kg)>冬季(436.6 mg/kg)>夏季(405.0 mg/kg)>秋季(269.4 mg/kg);其中秋季含量显著低于另外3个季节,同一季节不同湖区的表层沉积物中WSOC含量不同。西湖西进区域茅家埠、乌龟潭和浴鹄湾沉水植物恢复区表层沉积物中WSOC含量平均值为388.5 mg/kg,均高于沉水植物匮乏区的均值304.6 mg/kg,但差异并不显著,可能是由于水流和人工作用使得恢复区与匮乏区没有严格的界限;开展沉水植被恢复措施的西湖西进区域WSOC含量为346.6 mg/kg,显著低于没有植被恢复的大湖区域WSOC含量432.3 mg/kg,表明沉水植被恢复可以降低湖泊沉积物中WSOC含量,减少内源等污染物来源。

Water-soluble organic carbon（ WSOC） is the critical component of organic carbon in lake sediments,and plays an important role in lake ecology. Research has shown that an increase of WSOC in sediments and lakes has a significant effect on water quality. Hangzhou＇s West Lake is world famous,but also suffers from eutrophication.In this study,water-soluble organic carbon（ WSOC） concentrations in surface sediments were investigated in different areas of West Lake over an entire year and the aim of the study is to understand the WSOC levels in different areas of the lake,explore factors accounting for the dynamic variation of WSOC and supply basic data to support remediation of West Lake. A total of 13 sampling sites were selected： 6 sampling sites in the western section（ Maojiabu（ MY,MW）,Wuguitan（ WY,WW）,Yuguwan（ YY,YW）; 2 sampling sites at Xiaonan Lake（ NY,NW）;1 site each in the open waters of Xili Lake（ XL）,Beili Lake（ BL） and West Lake（ HC）,1 site in a bay of West Lake（ HW） and 1 site at the Yuehu Lake（ YH）. Surface sediment samples（ 0- 10） cm were taken in December（ winter） of 2013,April（ spring）,June（ summer） and October（ autumn） of 2014. The improved method of Xi Danli was used to analyze WSOC concentrations in the sediments with a total organic carbon（ TOC） analyzer. Results are as follows： The mean concentration of WSOC in surface sediments was 387. 1 mg / kg with significant differences among the seasons; Average concentrations for Spring,Winter,Summer and Autumn were,respectively,437. 5 mg / kg,436. 6 mg / kg,405. 0 mg / kg,269. 4 mg / kg,displaying much lower levels in autumn; Spatial variation occurred during each season. The average WSOC concentration（ 388. 5 mg / kg） in submerged macrophyte restoration areas（ MY,WY,YY） was higher than in areas（ MW,WW,YW） without submerged macrophytes（ 304. 6 mg /kg）,but the difference was not significant. This is likely because there are no strict boundaries between vegetated and non-vegetated areas to influence water flow. However,the average value（ 346. 6 mg / kg） of WSOC in the western area of West Lake,where macrophyte restoration was carried out,was significantly lower than other areas（ 432. 3 mg / kg）,indicating that submerged vegetation restoration reduces WSOC content in surface sediments.