Cao Hongying, Tao Shu, Xu Fuliu, Coveney Raymond M, Cao Jun, Li Bengang, Liu Wenxin, Wang Xuejun, Hu Jianying, Shen Weiran, Qin Baoping, Sun Ren
Department of Urban and Environmental Sciences, Laboratory for Earth Surface Processes, Peking University, Beijing 100871, China.
Environ Sci Technol. 2004 Apr 1;38(7):2126-32. doi: 10.1021/es0305860.
A level III fugacity model was applied to characterize the fate of gamma-HCH in Tianjin, China, before the 1990s when the contamination reached its maximum at steady state. Geometric means were used as model inputs. The concentrations of gamma-HCH in air, surface water, soil, sediment, crops, and fish as well as transfer fluxes across the interface between the compartments were derived under the assumption of steady state. The calculated concentrations were validated by independent data collected from the literature. There was generally good agreement between the estimated and the observed concentrations, and the differences were all less than 0.6 log units for air, water, soil, sediment, and fish and approximately 1 order of magnitude for crops. Around 97% of gamma-HCH accumulated in soil and sediment. Wastewater irrigation was not an important pathway for delivering gamma-HCH to soil as compared to the dominant source of agricultural application. Degradation and advective airflow carried much gamma-HCH out of the system. Sensitivities of the model estimates to input parameters were tested, and a coefficient of variation normalized sensitivity coefficient was defined for the test. The most influential parameters were degradation rates in sediment and soil, application rates, concentrations in wastewater, and adsorption coefficients. Monte Carlo simulation was conducted for model uncertainty analysis. The model was run 20 000 times using randomly generated data from predefined log-normal distribution density functions. All calculated concentrations and fluxes were log-normally distributed. The dispersions of the calculated and observed concentrations were compared in terms of coefficients of variation to distinguish between true variability and model uncertainty.
应用三级逸度模型来描述20世纪90年代之前中国天津γ-六氯环己烷的归宿，当时该污染物在稳态下达到污染最大值。采用几何平均值作为模型输入。在稳态假设下，得出了空气中、地表水中、土壤中、沉积物中、农作物和鱼类中γ-六氯环己烷的浓度以及各隔室间界面的转移通量。计算得出的浓度通过从文献中收集的独立数据进行验证。估计浓度与观测浓度总体上吻合良好，空气、水、土壤、沉积物和鱼类的差异均小于0.6对数单位，农作物的差异约为1个数量级。约97%的γ-六氯环己烷累积在土壤和沉积物中。与农业施用这一主要来源相比，废水灌溉并非γ-六氯环己烷进入土壤的重要途径。降解和平流气流将大量γ-六氯环己烷带出系统。测试了模型估计对输入参数的敏感性，并定义了变异系数归一化灵敏度系数用于该测试。最具影响力的参数是沉积物和土壤中的降解率、施用量、废水中的浓度以及吸附系数。进行了蒙特卡罗模拟以分析模型不确定性。使用从预定义对数正态分布密度函数中随机生成的数据运行该模型20000次。所有计算得出的浓度和通量均呈对数正态分布。根据变异系数比较计算浓度和观测浓度的离散程度，以区分真实变异性和模型不确定性。
