湖泊水、沉积物氮磷的空间分析及其耦合特征研究——以大通湖为例

摘要

Datong lake is the largest freshwater lake for aquaculture in Hunan province.Nitrogen and phosphorus in water and surface sediment can be easily affected during the fishing season in winter because of lower water stage and more human activities.In order to explore the influence factors and eutrophication of Datong lake in winter,geostatistical analysis was carried out to study the spatial characteristics and coupling relationship of organic matter,nitrogen and phosphorus in water and sediment.The results showed that concentration of total N and total T in water reached very high levels (3.78mg/L and 0.29mg/L),which exceed the Ⅴ class of surface water quality standard.The concentration of NH4+ was only about 0.17mg/L,which belonged to the Ⅱ class of surface water quality standard.Compare with the data of 2011,TP in sediment reached a high level with 1469mg/kg,but TN was still maintained at a steady level with 1224mg/kg.The value of nugget/sill was 43.4％ and 34.5％ for sediment TN and water NO3-,which indicated a moderately spatial dependent.However,nugget/sill was less than 25％ for the other N and P,which indicated a highly spatial dependent.OM,TN and TP in sediment showed an ascending tendency from northeast to southwest.Furthermore,N and P in water showed a patchy distribution.The average value of nitrogen/phosphorus ratio in water was 13.03,which was suitable for phytoplankton growth.OM was significantly correlated with TN and TP in sediment (P＜0.01).But TN and TP in sediment had no significant correlation with them in water.Therefore,aim to restore the lake environment,we should not only control the input of pollutant but also apply ecological measures.%大通湖是湖南省面积最大的淡水养殖湖泊,冬季作为捕鱼的旺季并且水位较低,水体和表面沉积物中氮、磷容易受到渔业生产的影响.本文从地统计学出发,通过研究冬季大通湖水体和沉积物中有机质(OM)、氮(N)和磷(P)的空间结构特征及其耦合关系,探讨大通湖富营养化程度及其影响因素,为可持续水产养殖和生态修复提供科学依据.结果表明:冬季大通湖水体中总氮(TN)、总磷(TP)浓度较高,平均值分别达到了3.78mg/L和0.29mg/L,为劣Ⅴ类.水体中NH:含量相对较低,平均为0.17mg/L,属于地表水Ⅱ类.与2011年数据比较,沉积物中TP浓度较高,平均升高到了1469mg/kg;而沉积物TN基本持平,平均为1224mg/kg;沉积物TP和水NO3-的“块金值/基台值”分别为43.4％和34.5％,表现为中等空间相关性(spatial dependence),其他N、P指标的“块金值/基台值”均低于25％,表现为强烈空间相关性.冬季大通湖沉积物OM、TN和TP在空间上呈现出有规律的带状分布,而水体N、P大体上呈现出“品”字形的斑块分布;水体中的氮磷比平均为13.03,比较适合浮游植物生长;沉积物OM只与沉积物TN和TP呈极显著正相关(P＜0.01),而积物中TN和TP与水体中的TN和TP相关性不显著.因此,大通湖水体修复在控制外源输入的情况下,还应考虑综合的生态系统工程措施.