基于蒙特卡洛模拟技术的杭嘉湖平原稻田土壤镉安全阈值研究

The Study on Cd Safety Benchmarks of Paddy Soil Based on Monte Carlo Simulation Technology on Hangjiahu Plain

安全的稻米产地环境是保障稻米镉含量不超标的基础,而正确确定稻米产地土壤镉安全阈值是进行产地安全管理的关键。为此,以杭嘉湖稻米主产区为例,通过土壤-稻米对应采样分别获得了研究区118个土壤-稻米样品,并基于监测数据采用线性回归与蒙特卡洛耦合模型法,回归方程法及吸收系数法构建了研究区稻米产地镉安全阈值。研究结果表明,土壤镉含量、土壤pH、土壤质地是影响稻米镉含量的主要因素。线性回归与蒙特卡洛耦合模型分析结果表明,在稻米镉达标期望概率为70%、80%、90%、100%时,土壤镉安全阈值分别为1.2 mg/kg、1.0 mg/kg、0.8 mg/kg及不能确定。采用吸收系数法计算的安全阈值为1.2 mg/kg,而直接采用监测数据的平均值代入回归方程得到的产地土壤安全阈值为1.5 mg/kg。不同安全需求下的土壤镉安全阈值有差异显著,运用回归方程法得出的结论高于令稻米镉含量达标率为70%的土壤镉安全阈值,吸收系数法得出的结论与令稻米镉含量达标率为70%的土壤镉安全阈值相一致。且结果均高于土壤环境质量标准二级镉阈值。

The foundation of avoiding the substandard of rice Cd is secure producing surroundings, while the key of ensuring secure producing surroundings is to value the safety threshold of soil Cd correctly. Therefore producing areas in Hangjiahu Paddy were taken for example and 118 soil-rice samples were taken on the research areas. Linear regression coupled with Monte Carlo method, regression model method and absorption coefficient method were used to value the safety threshold of soil Cd in paddy producing areas. The result showed that the main factors of rice Cd content are soil Cd content, soil pH and soil texture. Analysis based on linear regression coupled with Monte Carlo method indicated that when the expected qualification rate for rice Cd is 70% ,80% ,90%, 100%, the soil Cd safety threshold are 1.2 mg/kg, 1.0 mg/kg,0. 8 mg/kg and cannot achieved,respectively. The safety threshold valued by absorption coefficient method is 1.2 mg/kg, while that based on regression model method which plugs the monito- ring data averages into the regression model is 1.5 mg/kg. The soil Cd safety threshold under different security needs are significantly disparate. And the conclusion of regression model method is higher than that of Monte Carlo simulation technique when the qualification rate for rice Cd was 70% while the conclusion of absorption coefficient method is same with the result of Monte Carlo simulation technique when the qualification rate for rice Cd was 70%. And all the results of the three methods are higher than the soil environmental quality standards.