太湖西北部湖区入湖河流氮磷水质标准修正方案研究

氮磷污染一直是太湖流域的首要污染问题,有效遏制氮磷入湖量的增加是治理太湖的重要任务。然而由于我国现行的地表水环境质量标准(GB3838-2002)中河流和湖泊氮、磷水质标准存在差异,即河流无总氮控制指标、河湖总磷标准不一致的问题,往往造成通过控制入湖河流污染来改善太湖湖泊水质时,湖泊污染物浓度往往达不到治理目标。以太湖西北部湖区及其入湖河流为例,利用BATHTUB模型模拟入湖河流与湖泊TN、TP的关系,推算太湖在满足现行湖泊水质标准中TN和TP各类别目标值的情形下的环境容量并以此环境容量决定入湖河流的水质,进而提出相应的方案进行比选,从而提出太湖入湖河流氮磷水质标准修正方案。结果表明:(1)当太湖入湖河流执行现行河流水质TP标准时,对应湖泊的水质TP超标,并不能达到保护湖泊的目标;(2)当太湖西北部湖区入湖河流TN、TP执行现行湖泊水质标准,对应湖区水质均能达标并且优于目标限值,然而该方案对于污染较为严重的太湖区域的实际参考意义不足;(3)以现行湖泊水质标准TN、TP各类别为目标值反推计算入湖河流水质指标,既能保证湖泊水质达标,又不会使河流水质标准过于严格,因此其结果可作为入湖河流水质标准修正的参考,从而提出太湖入湖河流TN、TP水质标准建议方案。

THE RESEARCH IN THE REVISED PLAN OF WATER QUALITY STANDARD OF THE NITROGEN AND PHOSPHORUS FOR THE INFLOW RIVERS IN THE NORTHWEST OF THE TAIHU LAKE

Excessive input of nitrogen and phosphorus is always the main problem in the Taihu Lake basin,and it is important to cut the nitrogen and phosphorus loading from the catchment and control the water quality in the inflow rivers efficiently.The TN and TP standards in national surface water environmental quality standards of China (GB3838-2002) have discrepancy between rivers and lakes.That is,the lack of the TN standard for rivers and the inconformity between the TP standard for rivers and lakes.Thus,the pollutant control objective in lake is difficult to meet by restricting the nutrient input from rivers under nowadays' guideline.This paper took the northwest of the Taihu Lake and its inflow rivers as case study and used the BATHTUB model to simulate the correspondence between the concentrations of TN and TP in the inflow rivers and lakes.Then a plan to revise the nitrogen and phosphorus control was proposed for the inflow rivers in the northwest of the Taihu Lake.The modeling results showed that:1.If the inflow rivers implement the TP standard for rivers in the GB3838-2002,the TP concentration in lake would exceed its own standard and couldn't achieve the environmental goals.2.Provided the inflow rivers implementing the TN and TP standards for lakes in the GB3838-2002,the associated TN and TP concentrations in the lake could fulfill their environmental goals in GB3838-2002.However,this plan is lack of practical significance due to the poor water quality background in the Taihu Lake.3.If the TN and TP concentrations for inflow rivers are inferred according to each environmental goal for lakes in the GB3838-2002,the result is more practical to implement and could guarantee the water quality in the lake.Our results may give a reference to the revise of nitrogen and phosphorus standards for inflow rivers and then the water quality in the northwest of the TaihuLake can be improved.