基于统计模型LOADEST的宝象河污染物通量估算

污染物通量的估算是掌握河流输移负荷的简便方法,可为流域总量控制提供科学依据.LOADEST模型利用连续的水量数据和离散的水质数据,建立污染物通量回归方程,进而估算河流不同时间尺度(日/月/季节/年)下的污染物通量,此外,模型还考虑删失型水质数据的情况,是估算低频率水质监测河流污染物通量的有效途径.以滇池污染严重的入湖河流—宝象河为例,利用LOADEST模型建立污染物通量回归方程,进而估算1999—2008年河流的入湖通量和水质情况.结果表明:(1)TP、COD、TSS多年平均入湖通量分别为18.9×103、1374.0×103、5608.6×103kg/年,TN为239.2×103kg/年,其中溶解态氮(NO3--N,NH4+-N)占83.8%;(2)2001年后各污染物年均浓度均超过Ⅳ类水质标准,超标最严重的为TN;(3)丰水期入湖通量占年通量的40%以上,暴雨径流冲刷成为污染物进入河流的主要方式;(4)NH4+-N、TN、TP年和不同季节入湖通量、浓度均呈现显著增加趋势,年增长率达6%以上;COD入湖通量和浓度在1999—2004年呈增加趋势,2005年后呈下降趋势;由于流域开展水土保持治理措施,TSS的入湖通量和浓度均呈下降趋势.

Pollutant Fluxes Estimation for Baoxiang River,Dianchi Lake by Using LOADEST Model

Pollutant Fluxes Estimation is simple method to estimate river transport amount,thus providing scientific basis for total amount control.Load estimator model(LOADEST)uses continuous daily flow data and discontinuous water quality concentration data to predict a linear regression function that can be used to predict continuous daily,monthly,seasonal,or annual fluxes and concentrations.In addition,the model considers censored data of water quality.So it becomes the effective ways to estimate pollutant fluxes with low-frequency water quality data.Constituent concentrations and loads were evaluated at Baoxiang River,the Dianchi Lake,using the LOADEST during 1999 to 2008.The following conclusions were obtained:(1)Average annual loads of total phosphors(TP),COD,total suspended-sediment(TSS)were 18.9×103,1374.0×103 and 5608.6×103kg/a;total nitrogen(TN)were 239.2×103 kg/a,with 83.8% of TN as dissolved N(NO-3-N,NH+4-N).(2)Average annual concentrations of all constituents were higher than the fourth standard after 2001,especially nitrogen.(3)Approximately of 40% the annual loads of constituents occurred during wet season due to increased transports of nonpoint source loads by hydrologic pathway into the receiving water.(4)Fluxes and concentrations of NH+4-N,TN,TP,have significantly increased during the past 10 years,with annual mean growth rate of over 6%;fluxes and concentrations of COD showed an ascending tendency during 1999 to 2004 and descending tendency after 2005;due to development of soil and water conservation,fluxes and concentrations of TSS decreased.