基于环境基准的太湖氨氮最大容量研究

Research on Maximum Capacity of Ammonia Nitrogen in Taihu Lake Based on Environmental Benchmark

环境基准反映了环境介质中污染物的阈值剂量与保护对象的临界效应之间的对应性,其本质是一种下限阈值。经由推导和检验而得到的环境基准,可以在环境管理方面广泛应用。太湖位于我国经济最发达的地区之一——长江三角洲,其水质直接影响着该地区的生活与经济,太湖水环境污染主要是氨氮污染。该研究以太湖为对象,推导出太湖的氨氮环境容量,确定氨氮浓度控制目标和最大容许排放量,为今后太湖氨氮减排与治理提供理论依据。通过环境基准共性推导模式,建立和率定了水环境系统阈值响应模型;为了确定环境容量,开展了多种情景的模型模拟,将实测值与模拟值进行独立样本T检验,得出模拟值与实测值之间并无差异;建立的水环境系统的阈值响应模型具有一定的有效性。基于模拟结果比较而确定了氨氮的环境容量为1.334 mg·L^(-1),将其作为氨氮污染控制目标。以太湖流域2010氨氮年均浓度0.26 mg·L^(-1)为初始浓度,以20 a为模拟期,模拟不同排放强度下氨氮的浓度变化。将控制目标代入阈值响应模型,分析了不同排放情景下氨氮的浓度,通过情景模拟发现,氨氮的综合响应、消极响应(水体氨氮浓度对氨氮排放的响应)和积极响应(水体的自净能力)在不同排放强度下呈现出不同的变化特征。发现如果以20 a为目标期限,为保证氨氮浓度不超过污染物浓度控制目标,氨氮年度排放量要低于7.2×10~4t。

Environmental benchmark reflects the correspondence between threshold dose of pollutants in environmental media andcritical effect of protected object,and its essence is a lower threshold.And environmental benchmark can be applied inenvironmental management after derivations and tests.Taihu Lake is located in one of the most economically developed regions ofChina,of which water quality directly affects the life and economy in the Yangtze Delta.Ammonia nitrogen is the main pollutant inTaihu Lake.Taking Taihu Lake as the object,this study derives capacity of ammonia nitrogen in Taihu Lake and sets controlobjective of ammonia nitrogen concentration as well as maximum permissible emissions to provide a theoretical basis for the futuregovernance and emission reduction of ammonia nitrogen in Taihu Lake.In this paper,a threshold-response model of waterenvironmental system was established based on general derivation mode of environmental benchmark,and model simulations basedon different scenarios were carried out to determine the capacity of the environment,which comes out that there is no differencebetween the simulated and measured values by independent sample T-test.The threshold-response model of water environmentalsystem established in this paper has certain effectiveness.Environmental capacity was determined as1.334mg·L-1by means ofsimulation results comparison and the capacity was applied as control objective of ammonia nitrogen pollution.This research sets0.26mg·L-1(2010annual average ammonia nitrogen concentration of Taihu Lake Basin)as initial concentration and20years assimulation period,simulating the concentration changes under different emission intensity levels.Putting the control objective intomodel,and ammonia nitrogen concentration in different discharge scenarios was analyzed in this paper.Simulations indicates that thecomprehensive response and negative response(water ammonia nitrogen concentration in response to ammonia nitrogen emissions)and the positive response(water self-purification capacity)in different emission intensity levels show different changes.The resultsshowed that annual emissions should not exceed72000tons to ensure the ammonia nitrogen concentration does not exceed thecontrol objective.