天津地区菲的空间分异多介质归趋模型

Multimedia Fate Modeling with Spatial Resolution for Phenanthrene in Tianjin

在稳态假设条件下研究了菲在天津市的多介质分布和相间迁移 .在探讨了废气排放和土壤有机质含量和土壤中菲降解速率常数的空间变异的基础上 ,建立了具有空间变异特征的多介质模型 .并根据实际观测数据对平均浓度加以验证 .所研究的 4种介质的模型误差在 0 5个对数单位左右 ,完全符合区域多介质模型的精度要求 .土壤菲含量空间计算结果和实际观测数据在宏观尺度上表现出一致的趋势 .作为过程模型 ,这样的结果有助于解释形成其空间分异的原因 ,也为进一步研究奠定了基础 .模型计算结果表明 ,土壤和沉积物是该地区菲的主要汇 ,特别是沉积物中积累了菲总量的 70 %以上 .大气菲的空间分布格局基本服从其人为排放特征 ,而土壤有机质含量对菲降解速率的影响决定了其在土壤中的分布 .

Behavior and fate of phenanthrene in various phases in Tianjin were calculated using a multimedia model with spatial resolution under steady-state assumption. Spatial variation of two parameters, namely soil organic carbon content and emission from fossil fuel combustion,were taken into consideration. Both soil and air phases were further divided into 3113 sub-compartments and 6226 equations in total were solved simultaneously under mass-balance assumption. A number of output parameters, therefore, were generated and were used for mapping of phenanthrene concentrations in soil and air, as well as transfer fluxes between compartments. The model was evaluated in two ways: ① comparison between the calculated and the observed average concentrations in bulk compartments, and ② comparison of spatial distribution of the calculated and the observed phenanthrene concentrations in surface soil. In both cases, the predicted results are in fair agreement with the independently measured values. As the results of the modeling, it was demonstrated that soil and sediment, especially the later, is the primary sink of phenanthrene in the area over 70% of the chemical accumulated in sediment. The spatial distribution pattern of phenanthrene in surface soil depends on content of soil organic matter which prevent the degradation of the material by bacteria. For distribution in ambient air, the dominant controlling factor is the emission.