贡湖湾北部退渔还湖区水、沉积物和土壤中氮的时空分布

太湖贡湖湾北部退渔还湖区(2.18 km2)的水陆交错带,虽已进行了基底改造和小部分植物种植,但仍需开展大规模种植,故迫切需要了解其生境特性的状况,为此开展了该区域的水陆交错带水、沉积物、土壤中氮的时空分布特征调查,以便为后续示范工程的设计提供基本参数。选择南部和北部两处交错带(面积分别为6700、8300 m2)及其周边陆域、水域,分别在2012年11月和2013年5月采集17个点位的水、沉积物和土壤样品,分析了其氮的时空分布。结果表明:水、沉积物和土壤样品中的氮存在明显的季节变化,春季水、沉积物和土壤中的总氮和氨氮均低于秋季,而春季沉积物和土壤中硝氮含量较高。人为栽种植物有利于氮的去除,温度和微生物的活动对此也有一定的贡献。在春季,水陆交错区的硝化作用更强烈;氨氮的空间分布与总氮基本一致,水中氮的主要存在形式是氨氮,而沉积物和土壤中的氮以有机氮为主。

Distribution of Nitrogen in Water, Soil and Sediment in Water/Land Ecotone of Returning Fishpond to Lake Area of Northern Gonghu Bay

Returning fishpond to lake is one of approaches to restore regional ecosystems. Understanding transformation and cycling of nutrients in the restored area is critical to implementation of such practice. Here, a water-land ecotone(2.18 km²) in returning fishpond to lake area of north Gonghu Bay of Lake Taihu was selected to examine the temporal and spatial variations of nitrogen in water, sediment, and soil. Seventeen sampling locations were chosen at the north and south zones. Water, sediment and soil samples were collected in November 2012 and May 2013. Total nitrogen and ammonia nitrogen in water, soil and sediment samples were lower in Spring than in Autumn, but nitrate nitrogen in soils was higher in Spring than in Autumn, showing a significant seasonal variation. Growing plants artificially had a great contribution to the removal of nitrogen. In addition, temperature and microbial activity would help improve nitrogen removal. In water-land ecotone, nitrification was greater in Spring than in Autumn. The spatial distribution of ammonia nitrogen was consistent with that of total nitrogen. The dominant form of nitrogen in water was ammonia nitrogen, however, organic nitrogen was the main form in the sediment and soil.