路旁土壤公路源重金属含量空间分布数值模型的探讨

公路源重金属产生后,赋存于大气颗粒物中,随颗粒物在大气中迁移沉降,最终沉降于路旁土壤中.本研究通过对公路源重金属迁移机理的分析,以高斯污染物扩散模型为基础,构建公路源重金属在路旁土壤中空间分布的数值模型,并用G310国道杏花营断面路旁土壤重金属(Cd、Cr、Cu、Ni、Pb和Zn)含量空间分布实测数据对模型预测能力进行验证.结果表明:土壤Cr和Cu含量呈指数分布,土壤Cd、Ni、Pb和Zn含量呈偏态分布,指数分布实质上是偏态分布的峰值十分接近路基的一种特例.研究表明,本文构造的数值模型可以较好地拟合上述两种路旁土壤重金属空间分布形式,模拟情景数n的取值越大,模拟结果越准确.

Spatial numerical model of traffic-source heavy metals in roadside soils

Heavy metals generated from traffic exhausts are mainly adsorbed by atmospheric particulate matters, which transport and often deposit on to roadside soils in distances away from the road. Based on the analysis of the transport mechanism of traffic-source heavy metals by the Gaussian pollutant dispersion model, a numerical model that simulates the spatial distribution of traffic-source heavy metals in roadside soils was developed. The model was verified with the heavy metal concentration data in the roadside soil of the Xinghuaying transect, G310 Highway. The results show that the concentrations of Cr and Cu in roadside soils decrease exponentially with the distance from the road; however, the concentrations of Cd, Ni, Pb and Zn appear a skewed distribution. Actually, the exponential distribution of heavy metals in roadside soils is a special case of the skewed distribution, with its peak value very close to the road. The numerical model can well fit with both the exponential and skewed distribution of heavy metals in roadside soils. The larger the parameter "n" in the model is, the more accurate the model simulation results.