基于Monte Carlo模拟的河流水质评价——以温瑞塘河为例

基于水质评价的综合污染指数（CWQI）法和水质指标实测含量的统计分析，应用Monte Carlo模拟方法，建立了河流水质评价的Monte Carlo-CWQI耦合模型并进行实例研究.通过建立的耦合模型和温瑞塘河流域14个监测断面2004~2010年的水质监测数据，定量分析各监测断面隶属于不同污染等级的概率水平和各水质指标对水体污染的影响程度.结果表明：温瑞塘河水系水质污染十分严重，勤奋、九山、东水厂、十字河、南白象、灰桥、新桥、米筛桥、仙门、光明、郭溪、瞿溪、西岙和梧田监测断面处于重度污染的概率分别为28.50%，0.55%，92.71%，59.73%，78.85%，39.38%，78.87%，83.09%，65.32%，78.08%，0.00%，0.96%，68.09%，86.06%；处于严重污染的概率分别为71.28%，0.01%，4.33%，39.76%，21.07%，60.59%，4.42%，12.41%，11.02%，21.24%，0.00%，0.02%，1.42%，13.12%.各监测断面总氮（TN），氨氮（NH₃-N）和溶解氧（DO）的Spearman等级相关系数范围分别是0.41~0.76、0.25~0.63和0.14~0.66，是其他指标的2倍以上，表明影响该地区水质达标的主要因子是TN，NH₃-N和DO.本研究拓宽了河流水质评价的研究视角，能够为流域水环境管理提供丰富的决策依据.

River water quality assessment based on Monte Carlo simulation: A case study of Wen-Rui Tang River

Accurate evaluation of the pollution magnitude in a water body is an important premise for effective water pollution prevention and control. This study used Monte Carlo simulation method together with comprehensive water quality index (CWQI) method and statistical analysis of measured water quality parameters to assess water quality. The Wen-Rui Tang River watershed was used as the study site. Through the combined model and water quality data from 14 monitoring sites at Wen-Rui Tang River during 2004 to 2010, the probability of each site for every pollution level and the influence of each water quality parameter on water pollution were quantified. The results of Monte Carlo-CWQI coupled model indicated that the water quality of Wen-Rui Tang River was highly impaired. The probabilities of the water impairments at sites of Qinfen, Jiushan, Dongshuichang, Shizihe, Nanbaixiang, Huiqiao, Xinqiao, Mishaiqiao, Xianmen, Guangming, Guoxi, Quxi, Xi-ao, and Wutian being at the heavy pollution level were 28.50%, 0.55%, 92.71%, 59.73%, 78.85%, 39.38%, 78.87%, 83.09%, 65.32%, 78.08%, 0.00%, 0.96%, 68.09%, and 86.06%, respectively. The probabilities of the water impairments at these monitoring sites being worse than heavy pollution level were 71.28%, 0.01%, 4.33%, 39.76%, 21.07%, 60.59%, 4.42%, 12.41%, 11.02%, 21.24%, 0.00%, 0.02%, 1.42%, and 13.12%, respectively. The spearman rank correlation coefficient for total nitrogen (TN), ammonium-nitrogen (NH₃-N) and dissolved oxygen (DO) respectively ranged from 0.41 to 0.76, 0.25 to 0.63 and 0.14 to 0.66, which were more than twice on the values for other parameters. This result implied that TN, NH₃-N and DO were the dominant factors affecting the rate of reaching water quality standard in Wen-Rui Tang River. This investigation can broaden the viewpoints for researches and managers on river water quality evaluation and can provide abundant information for decision-making on water environment management.