三峡库区腹心地带消落区土壤氮磷含量调查

消落区土壤中氮磷是上覆水体营养物质的潜在来源之一。在2008年底三峡蓄水至172 m之前，采样分析了小江（澎溪河）等库区5条典型支流淹没前的消落区土壤氮磷含量分布情况。在研究样区范围内，消落区土壤全氮均值为1317±0484 mg/g，变化范围在0459~2735 mg/g，而土壤全磷均值为0676±0282 mg/g，变化范围在0314~2799 mg/g。不同的土地利用方式消落区土壤全氮含量有明显差异，耕地消落区和园林地消落区的全氮值明显高于河滩地消落区。不同流域之间氮素差异也达到极显著水平，朱衣河和大宁河流域消落区土壤氮素要明显高于其他3条支流。但是，不同土地利用方式的消落区之间全磷差异不显著，不同流域之间磷素差异也不显著。相比长江中下游一些浅水湖泊的底泥，库区消落区土壤中全氮和全磷含量水平已处于偏高状态，向上覆水体释放的风险较大。小江流域的丰乐镇和养鹿镇、朱衣河的胡家坝地区是研究范围内释放风险高的区域.

INVESTIGATION OF SOIL NITROGEN AND PHOSPHORUS IN WATER FLUCTUATION ZONE IN CENTRAL DISTRICT OF THREE GORGES RESERVOIR AREA

Soil nitrogen and phosphorus in water fluctuation zone are one of the potential sources and the nutrients for the upper layer water column.Nitrogen and phosphorus concentration among five representative tributary in Three Gorges Reservoir Area were analyzed before the impoundment of Three Gorges Reservoir to a water level of 172 m at the end of 2008.It was found that mean of soil total nitrogen in study area was 1317±0484 mg/g with variation range of 0459~2735 mg/g，while that of phosphorus was 0676±0282 mg/g with a range of 0314~2799 mg/g.Soil total nitrogen from different type of land use showed significant difference.Soil nitrogen in agriculture farmland and fruit gardens was remarkably higher than those in riverbank and flood plains.Difference of soil nitrogen was also observed among different tributaries，the soil nitrogen in Zhuyi Basin and Daning Basin was obviously higher than in the other basins.However，the soil phosphorus among various types of land use in the study area as well as different basins showed no significant difference.Compared with some shallow lakes in the downstream plain of the Yangtze basin，soil total nitrogen and total phosphorus were high relatively，and had a potential risk of releasing to the upper layer water column.Fengle town and Yanglu town in Xiaojiang River and Hujiaba town in Zhuyi River were the highest risk to release nitrogen and phosphorus in study areas.