基于水位-面积-湖容关系的东洞庭湖动态纳污能力分析

Dynamic Pollutant Absorption Capacity of East Dongting Lake Based on Relationship among Water Level,Area and Volume

为测算不同水文水质条件下东洞庭湖动态纳污能力,利用2003—2016年MODIS遥感数据和实测水文数据建立水位-面积-湖容关系模型,提取不同水位、入湖流量、入湖水质条件下的纳污能力计算参数,参照《水域纳污能力计算规程》测算出不同水文水质条件下的东洞庭湖动态纳污能力系数以及COD、氨氮的动态纳污能力。研究结果表明:东洞庭湖纳污能力随着水位、流量、水质而动态变化,COD最小纳污能力为14 200 g/s,大于2016年年均排放强度1 837 g/s,不存在水质超标风险;氨氮最小纳污能力43 g/s,小于2016年年均排放强度275 g/s,水质超标风险大;明确了导致氨氮超标的水文、水质条件,认为氨氮入湖浓度<0.95 mg/L时,湖泊氨氮不超标。主要结论为:(1)水位-面积-湖容关系模型可为测算湖泊动态纳污能力提供支撑;(2)建议根据动态水域纳污能力确定污染物排放量,科学利用水环境容量;(3)东洞庭湖入湖氨氮浓度应控制在0.95 mg/L以下,以保证水质达标。研究成果对维护和改善洞庭湖水环境质量具有重要的现实意义。

In an attempt to obtain the dynamic pollutant absorption capacity of East Dongting Lake in different hydrological and water quality conditions,a model of relationship among water level,area and volume was established according to MODIS remote sensing data in 2003-2016 and hydrological data.Some calculation parameters in the presence of different water levels,incoming flow rates,and incoming water quality indicators were acquired.According to the Code for calculation of water pollution absorption capacity,the coefficient of pollutant absorption capacity,together with the dynamic absorption capacity of COD and ammonia-nitrogen in different hydrological and water quality conditions was calculated.Authors insisted that the pollutant absorption capacity of East Dongting Lake varies with water level,discharge and water quality dynamically.The minimum absorption capacity of COD is 14 200 g/s,greater than the average emission intensity which is 1 837 g/s in 2016,brewing no risk of standard-exceeding;but the minimum absorption capacity of ammonia-nitrogen is 43 g/s,smaller than the average emission intensity which is 275 g/s in 2016,posing large risk of standard-exceeding of ammonia-nitrogen.Moreover,hydrology and water quality conditions which would result in the standard-exceeding of water quality were determined:when incoming concentration of ammonia-nitrogen stays below 0.95 mg/L,ammonia-nitrogen concentration in the Lake would not exceed standard.We concluded that(1)The established model provides support for the calculation of dynamic pollutant absorption capacity;(2)Pollutant emission could be rearranged reasonably according to the dynamic pollutant absorption capacity.(3)The incoming concentration of ammonia-nitrogen should be controlled under 0.95 mg/L in East Dongting Lake.