草海沉积物营养元素分布特征与控制因素

选取贵州草海这一典型高原湖泊湿地作为研究对象,在代表性湖区共布设17个采样点,采集了表层沉积物和沉积物柱芯,对沉积物总有机碳(TOC)、总氮(TN)和总磷(TP)分布特征及控制因素开展了对比研究。研究结果表明,草海表层沉积物营养盐分布主要受外源输入和湖泊初级生产控制:表层沉积物TOC、TN含量平均值分别为232.98mg/g和25.21mg/g,远高于国内其他湖泊,且呈现湖心高、近岸区低的分布特征,由于氮较高的迁移性和生物可利用性,草海沉积物TN明显受湖泊水生植物生长控制,主要以有机质形式赋存于沉积物中;表层沉积物TP含量平均值为1.03mg/g,其空间分布特征显著不同于TOC、TN,在湖心、东南湖区和出水口其含量较低,主要受外源输入控制,且主要以沉淀、吸附等无机形态赋存于沉积物中。草海沉积物柱芯中TOC、TN、TP含量总体上呈现随深度增加先迅速降低而后趋于稳定的变化趋势,但不同湖区其含量差异较大,反映了人为干扰强度和沉积环境的差异。草海流域外源污染物输入和沉积物较高的营养盐内负荷是其水体富营养化面临的主要威胁,一方面应采取有效手段消减外源污染物输入,另一方面应通过合理的生态修复措施控制内源营养盐释放。草海繁茂的沉水植物增强了水体自净功能,优化草海水生植物种群结构、恢复草型健康湖泊生态系统对保护草海生态环境具有重要意义。

Distribution Characteristics and Controlling Factors of Total Organic Carbon, Total Nitrogen, and Total Phosphorus in Sediments of Caohai Lake, China

This study focused on the distribution characteristics and controlling factors of nutrients in sediments of Caohai Lake, a typical plateau wetland in China. Contents of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in 17 surface sediments and three sediment cores were analyzed. Results show that the contents of TOC range from 68.64 mg/g to 348.48 mg/g, with an average of 232.98±77.95 mg/g, and the contents of TN range from 9.32 mg/g to 39.96 mg/g, with an average of 25.21±7.58 mg/g, both of which are much higher than other lakes in China. The TOC and TN in surface sediments come mainly from hydrophytes, and their contents are low in nearshore zone whereas high in central area. Contents of TP range from 0.52 mg/g to 1.54 mg/g, which was also higher than most lakes. The TP contents are low in central area but high in nearshore zone and come from sewage and agricultural nonpoint source pollution. Although there are differences for nutrients in sediments cores because of different anthropogenic disturbance and sedimentary environments, contents of TOC, TN, and TP decrease and gradually keep a constant level with increasing depth. The exogenous pollutions and heavy internal loading of nutrient pose a great threat to the water environment of Caohai Lake. Effective measures and ecological restoration should be taken to reduce the external pollution and control the release from sediment. The lush submerged plants in this lake greatly enhance self-purification and restrain the release of nutrient from sediments, and are therefore important for the optimization of submerged plants and restoration of a clear macrophytic-healthy ecosystem in Caohai Lake.